]> git.ipfire.org Git - thirdparty/git.git/commitdiff
reftable: implement stack, a mutable database of reftable files.
authorHan-Wen Nienhuys <hanwen@google.com>
Thu, 7 Oct 2021 20:25:13 +0000 (20:25 +0000)
committerJunio C Hamano <gitster@pobox.com>
Fri, 8 Oct 2021 17:45:48 +0000 (10:45 -0700)
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Makefile
reftable/reftable-stack.h [new file with mode: 0644]
reftable/stack.c [new file with mode: 0644]
reftable/stack.h [new file with mode: 0644]
reftable/stack_test.c [new file with mode: 0644]
t/helper/test-reftable.c

index 827a719014096ed7e3428b777888d1722f5a97f9..8be7e05ff994cb69218261ab885c8500db6faad7 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -2479,6 +2479,7 @@ REFTABLE_TEST_OBJS += reftable/pq_test.o
 REFTABLE_TEST_OBJS += reftable/record_test.o
 REFTABLE_TEST_OBJS += reftable/readwrite_test.o
 REFTABLE_TEST_OBJS += reftable/refname_test.o
+REFTABLE_TEST_OBJS += reftable/stack_test.o
 REFTABLE_TEST_OBJS += reftable/test_framework.o
 REFTABLE_TEST_OBJS += reftable/tree_test.o
 
diff --git a/reftable/reftable-stack.h b/reftable/reftable-stack.h
new file mode 100644 (file)
index 0000000..1b602dd
--- /dev/null
@@ -0,0 +1,128 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#ifndef REFTABLE_STACK_H
+#define REFTABLE_STACK_H
+
+#include "reftable-writer.h"
+
+/*
+ * The stack presents an interface to a mutable sequence of reftables.
+
+ * A stack can be mutated by pushing a table to the top of the stack.
+
+ * The reftable_stack automatically compacts files on disk to ensure good
+ * amortized performance.
+ *
+ * For windows and other platforms that cannot have open files as rename
+ * destinations, concurrent access from multiple processes needs the rand()
+ * random seed to be randomized.
+ */
+struct reftable_stack;
+
+/* open a new reftable stack. The tables along with the table list will be
+ *  stored in 'dir'. Typically, this should be .git/reftables.
+ */
+int reftable_new_stack(struct reftable_stack **dest, const char *dir,
+                      struct reftable_write_options config);
+
+/* returns the update_index at which a next table should be written. */
+uint64_t reftable_stack_next_update_index(struct reftable_stack *st);
+
+/* holds a transaction to add tables at the top of a stack. */
+struct reftable_addition;
+
+/*
+ * returns a new transaction to add reftables to the given stack. As a side
+ * effect, the ref database is locked.
+ */
+int reftable_stack_new_addition(struct reftable_addition **dest,
+                               struct reftable_stack *st);
+
+/* Adds a reftable to transaction. */
+int reftable_addition_add(struct reftable_addition *add,
+                         int (*write_table)(struct reftable_writer *wr,
+                                            void *arg),
+                         void *arg);
+
+/* Commits the transaction, releasing the lock. After calling this,
+ * reftable_addition_destroy should still be called.
+ */
+int reftable_addition_commit(struct reftable_addition *add);
+
+/* Release all non-committed data from the transaction, and deallocate the
+ * transaction. Releases the lock if held. */
+void reftable_addition_destroy(struct reftable_addition *add);
+
+/* add a new table to the stack. The write_table function must call
+ * reftable_writer_set_limits, add refs and return an error value. */
+int reftable_stack_add(struct reftable_stack *st,
+                      int (*write_table)(struct reftable_writer *wr,
+                                         void *write_arg),
+                      void *write_arg);
+
+/* returns the merged_table for seeking. This table is valid until the
+ * next write or reload, and should not be closed or deleted.
+ */
+struct reftable_merged_table *
+reftable_stack_merged_table(struct reftable_stack *st);
+
+/* frees all resources associated with the stack. */
+void reftable_stack_destroy(struct reftable_stack *st);
+
+/* Reloads the stack if necessary. This is very cheap to run if the stack was up
+ * to date */
+int reftable_stack_reload(struct reftable_stack *st);
+
+/* Policy for expiring reflog entries. */
+struct reftable_log_expiry_config {
+       /* Drop entries older than this timestamp */
+       uint64_t time;
+
+       /* Drop older entries */
+       uint64_t min_update_index;
+};
+
+/* compacts all reftables into a giant table. Expire reflog entries if config is
+ * non-NULL */
+int reftable_stack_compact_all(struct reftable_stack *st,
+                              struct reftable_log_expiry_config *config);
+
+/* heuristically compact unbalanced table stack. */
+int reftable_stack_auto_compact(struct reftable_stack *st);
+
+/* delete stale .ref tables. */
+int reftable_stack_clean(struct reftable_stack *st);
+
+/* convenience function to read a single ref. Returns < 0 for error, 0 for
+ * success, and 1 if ref not found. */
+int reftable_stack_read_ref(struct reftable_stack *st, const char *refname,
+                           struct reftable_ref_record *ref);
+
+/* convenience function to read a single log. Returns < 0 for error, 0 for
+ * success, and 1 if ref not found. */
+int reftable_stack_read_log(struct reftable_stack *st, const char *refname,
+                           struct reftable_log_record *log);
+
+/* statistics on past compactions. */
+struct reftable_compaction_stats {
+       uint64_t bytes; /* total number of bytes written */
+       uint64_t entries_written; /* total number of entries written, including
+                                    failures. */
+       int attempts; /* how often we tried to compact */
+       int failures; /* failures happen on concurrent updates */
+};
+
+/* return statistics for compaction up till now. */
+struct reftable_compaction_stats *
+reftable_stack_compaction_stats(struct reftable_stack *st);
+
+/* print the entire stack represented by the directory */
+int reftable_stack_print_directory(const char *stackdir, uint32_t hash_id);
+
+#endif
diff --git a/reftable/stack.c b/reftable/stack.c
new file mode 100644 (file)
index 0000000..df5021e
--- /dev/null
@@ -0,0 +1,1396 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#include "stack.h"
+
+#include "system.h"
+#include "merged.h"
+#include "reader.h"
+#include "refname.h"
+#include "reftable-error.h"
+#include "reftable-record.h"
+#include "reftable-merged.h"
+#include "writer.h"
+
+static int stack_try_add(struct reftable_stack *st,
+                        int (*write_table)(struct reftable_writer *wr,
+                                           void *arg),
+                        void *arg);
+static int stack_write_compact(struct reftable_stack *st,
+                              struct reftable_writer *wr, int first, int last,
+                              struct reftable_log_expiry_config *config);
+static int stack_check_addition(struct reftable_stack *st,
+                               const char *new_tab_name);
+static void reftable_addition_close(struct reftable_addition *add);
+static int reftable_stack_reload_maybe_reuse(struct reftable_stack *st,
+                                            int reuse_open);
+
+static void stack_filename(struct strbuf *dest, struct reftable_stack *st,
+                          const char *name)
+{
+       strbuf_reset(dest);
+       strbuf_addstr(dest, st->reftable_dir);
+       strbuf_addstr(dest, "/");
+       strbuf_addstr(dest, name);
+}
+
+static ssize_t reftable_fd_write(void *arg, const void *data, size_t sz)
+{
+       int *fdp = (int *)arg;
+       return write(*fdp, data, sz);
+}
+
+int reftable_new_stack(struct reftable_stack **dest, const char *dir,
+                      struct reftable_write_options config)
+{
+       struct reftable_stack *p =
+               reftable_calloc(sizeof(struct reftable_stack));
+       struct strbuf list_file_name = STRBUF_INIT;
+       int err = 0;
+
+       if (config.hash_id == 0) {
+               config.hash_id = GIT_SHA1_FORMAT_ID;
+       }
+
+       *dest = NULL;
+
+       strbuf_reset(&list_file_name);
+       strbuf_addstr(&list_file_name, dir);
+       strbuf_addstr(&list_file_name, "/tables.list");
+
+       p->list_file = strbuf_detach(&list_file_name, NULL);
+       p->reftable_dir = xstrdup(dir);
+       p->config = config;
+
+       err = reftable_stack_reload_maybe_reuse(p, 1);
+       if (err < 0) {
+               reftable_stack_destroy(p);
+       } else {
+               *dest = p;
+       }
+       return err;
+}
+
+static int fd_read_lines(int fd, char ***namesp)
+{
+       off_t size = lseek(fd, 0, SEEK_END);
+       char *buf = NULL;
+       int err = 0;
+       if (size < 0) {
+               err = REFTABLE_IO_ERROR;
+               goto done;
+       }
+       err = lseek(fd, 0, SEEK_SET);
+       if (err < 0) {
+               err = REFTABLE_IO_ERROR;
+               goto done;
+       }
+
+       buf = reftable_malloc(size + 1);
+       if (read(fd, buf, size) != size) {
+               err = REFTABLE_IO_ERROR;
+               goto done;
+       }
+       buf[size] = 0;
+
+       parse_names(buf, size, namesp);
+
+done:
+       reftable_free(buf);
+       return err;
+}
+
+int read_lines(const char *filename, char ***namesp)
+{
+       int fd = open(filename, O_RDONLY);
+       int err = 0;
+       if (fd < 0) {
+               if (errno == ENOENT) {
+                       *namesp = reftable_calloc(sizeof(char *));
+                       return 0;
+               }
+
+               return REFTABLE_IO_ERROR;
+       }
+       err = fd_read_lines(fd, namesp);
+       close(fd);
+       return err;
+}
+
+struct reftable_merged_table *
+reftable_stack_merged_table(struct reftable_stack *st)
+{
+       return st->merged;
+}
+
+static int has_name(char **names, const char *name)
+{
+       while (*names) {
+               if (!strcmp(*names, name))
+                       return 1;
+               names++;
+       }
+       return 0;
+}
+
+/* Close and free the stack */
+void reftable_stack_destroy(struct reftable_stack *st)
+{
+       char **names = NULL;
+       int err = 0;
+       if (st->merged) {
+               reftable_merged_table_free(st->merged);
+               st->merged = NULL;
+       }
+
+       err = read_lines(st->list_file, &names);
+       if (err < 0) {
+               FREE_AND_NULL(names);
+       }
+
+       if (st->readers) {
+               int i = 0;
+               struct strbuf filename = STRBUF_INIT;
+               for (i = 0; i < st->readers_len; i++) {
+                       const char *name = reader_name(st->readers[i]);
+                       strbuf_reset(&filename);
+                       if (names && !has_name(names, name)) {
+                               stack_filename(&filename, st, name);
+                       }
+                       reftable_reader_free(st->readers[i]);
+
+                       if (filename.len) {
+                               /* On Windows, can only unlink after closing. */
+                               unlink(filename.buf);
+                       }
+               }
+               strbuf_release(&filename);
+               st->readers_len = 0;
+               FREE_AND_NULL(st->readers);
+       }
+       FREE_AND_NULL(st->list_file);
+       FREE_AND_NULL(st->reftable_dir);
+       reftable_free(st);
+       free_names(names);
+}
+
+static struct reftable_reader **stack_copy_readers(struct reftable_stack *st,
+                                                  int cur_len)
+{
+       struct reftable_reader **cur =
+               reftable_calloc(sizeof(struct reftable_reader *) * cur_len);
+       int i = 0;
+       for (i = 0; i < cur_len; i++) {
+               cur[i] = st->readers[i];
+       }
+       return cur;
+}
+
+static int reftable_stack_reload_once(struct reftable_stack *st, char **names,
+                                     int reuse_open)
+{
+       int cur_len = !st->merged ? 0 : st->merged->stack_len;
+       struct reftable_reader **cur = stack_copy_readers(st, cur_len);
+       int err = 0;
+       int names_len = names_length(names);
+       struct reftable_reader **new_readers =
+               reftable_calloc(sizeof(struct reftable_reader *) * names_len);
+       struct reftable_table *new_tables =
+               reftable_calloc(sizeof(struct reftable_table) * names_len);
+       int new_readers_len = 0;
+       struct reftable_merged_table *new_merged = NULL;
+       int i;
+
+       while (*names) {
+               struct reftable_reader *rd = NULL;
+               char *name = *names++;
+
+               /* this is linear; we assume compaction keeps the number of
+                  tables under control so this is not quadratic. */
+               int j = 0;
+               for (j = 0; reuse_open && j < cur_len; j++) {
+                       if (cur[j] && 0 == strcmp(cur[j]->name, name)) {
+                               rd = cur[j];
+                               cur[j] = NULL;
+                               break;
+                       }
+               }
+
+               if (!rd) {
+                       struct reftable_block_source src = { NULL };
+                       struct strbuf table_path = STRBUF_INIT;
+                       stack_filename(&table_path, st, name);
+
+                       err = reftable_block_source_from_file(&src,
+                                                             table_path.buf);
+                       strbuf_release(&table_path);
+
+                       if (err < 0)
+                               goto done;
+
+                       err = reftable_new_reader(&rd, &src, name);
+                       if (err < 0)
+                               goto done;
+               }
+
+               new_readers[new_readers_len] = rd;
+               reftable_table_from_reader(&new_tables[new_readers_len], rd);
+               new_readers_len++;
+       }
+
+       /* success! */
+       err = reftable_new_merged_table(&new_merged, new_tables,
+                                       new_readers_len, st->config.hash_id);
+       if (err < 0)
+               goto done;
+
+       new_tables = NULL;
+       st->readers_len = new_readers_len;
+       if (st->merged) {
+               merged_table_release(st->merged);
+               reftable_merged_table_free(st->merged);
+       }
+       if (st->readers) {
+               reftable_free(st->readers);
+       }
+       st->readers = new_readers;
+       new_readers = NULL;
+       new_readers_len = 0;
+
+       new_merged->suppress_deletions = 1;
+       st->merged = new_merged;
+       for (i = 0; i < cur_len; i++) {
+               if (cur[i]) {
+                       const char *name = reader_name(cur[i]);
+                       struct strbuf filename = STRBUF_INIT;
+                       stack_filename(&filename, st, name);
+
+                       reader_close(cur[i]);
+                       reftable_reader_free(cur[i]);
+
+                       /* On Windows, can only unlink after closing. */
+                       unlink(filename.buf);
+
+                       strbuf_release(&filename);
+               }
+       }
+
+done:
+       for (i = 0; i < new_readers_len; i++) {
+               reader_close(new_readers[i]);
+               reftable_reader_free(new_readers[i]);
+       }
+       reftable_free(new_readers);
+       reftable_free(new_tables);
+       reftable_free(cur);
+       return err;
+}
+
+/* return negative if a before b. */
+static int tv_cmp(struct timeval *a, struct timeval *b)
+{
+       time_t diff = a->tv_sec - b->tv_sec;
+       int udiff = a->tv_usec - b->tv_usec;
+
+       if (diff != 0)
+               return diff;
+
+       return udiff;
+}
+
+static int reftable_stack_reload_maybe_reuse(struct reftable_stack *st,
+                                            int reuse_open)
+{
+       struct timeval deadline = { 0 };
+       int err = gettimeofday(&deadline, NULL);
+       int64_t delay = 0;
+       int tries = 0;
+       if (err < 0)
+               return err;
+
+       deadline.tv_sec += 3;
+       while (1) {
+               char **names = NULL;
+               char **names_after = NULL;
+               struct timeval now = { 0 };
+               int err = gettimeofday(&now, NULL);
+               int err2 = 0;
+               if (err < 0) {
+                       return err;
+               }
+
+               /* Only look at deadlines after the first few times. This
+                  simplifies debugging in GDB */
+               tries++;
+               if (tries > 3 && tv_cmp(&now, &deadline) >= 0) {
+                       break;
+               }
+
+               err = read_lines(st->list_file, &names);
+               if (err < 0) {
+                       free_names(names);
+                       return err;
+               }
+               err = reftable_stack_reload_once(st, names, reuse_open);
+               if (err == 0) {
+                       free_names(names);
+                       break;
+               }
+               if (err != REFTABLE_NOT_EXIST_ERROR) {
+                       free_names(names);
+                       return err;
+               }
+
+               /* err == REFTABLE_NOT_EXIST_ERROR can be caused by a concurrent
+                  writer. Check if there was one by checking if the name list
+                  changed.
+               */
+               err2 = read_lines(st->list_file, &names_after);
+               if (err2 < 0) {
+                       free_names(names);
+                       return err2;
+               }
+
+               if (names_equal(names_after, names)) {
+                       free_names(names);
+                       free_names(names_after);
+                       return err;
+               }
+               free_names(names);
+               free_names(names_after);
+
+               delay = delay + (delay * rand()) / RAND_MAX + 1;
+               sleep_millisec(delay);
+       }
+
+       return 0;
+}
+
+/* -1 = error
+ 0 = up to date
+ 1 = changed. */
+static int stack_uptodate(struct reftable_stack *st)
+{
+       char **names = NULL;
+       int err = read_lines(st->list_file, &names);
+       int i = 0;
+       if (err < 0)
+               return err;
+
+       for (i = 0; i < st->readers_len; i++) {
+               if (!names[i]) {
+                       err = 1;
+                       goto done;
+               }
+
+               if (strcmp(st->readers[i]->name, names[i])) {
+                       err = 1;
+                       goto done;
+               }
+       }
+
+       if (names[st->merged->stack_len]) {
+               err = 1;
+               goto done;
+       }
+
+done:
+       free_names(names);
+       return err;
+}
+
+int reftable_stack_reload(struct reftable_stack *st)
+{
+       int err = stack_uptodate(st);
+       if (err > 0)
+               return reftable_stack_reload_maybe_reuse(st, 1);
+       return err;
+}
+
+int reftable_stack_add(struct reftable_stack *st,
+                      int (*write)(struct reftable_writer *wr, void *arg),
+                      void *arg)
+{
+       int err = stack_try_add(st, write, arg);
+       if (err < 0) {
+               if (err == REFTABLE_LOCK_ERROR) {
+                       /* Ignore error return, we want to propagate
+                          REFTABLE_LOCK_ERROR.
+                       */
+                       reftable_stack_reload(st);
+               }
+               return err;
+       }
+
+       if (!st->disable_auto_compact)
+               return reftable_stack_auto_compact(st);
+
+       return 0;
+}
+
+static void format_name(struct strbuf *dest, uint64_t min, uint64_t max)
+{
+       char buf[100];
+       uint32_t rnd = (uint32_t)rand();
+       snprintf(buf, sizeof(buf), "0x%012" PRIx64 "-0x%012" PRIx64 "-%08x",
+                min, max, rnd);
+       strbuf_reset(dest);
+       strbuf_addstr(dest, buf);
+}
+
+struct reftable_addition {
+       int lock_file_fd;
+       struct strbuf lock_file_name;
+       struct reftable_stack *stack;
+
+       char **new_tables;
+       int new_tables_len;
+       uint64_t next_update_index;
+};
+
+#define REFTABLE_ADDITION_INIT                \
+       {                                     \
+               .lock_file_name = STRBUF_INIT \
+       }
+
+static int reftable_stack_init_addition(struct reftable_addition *add,
+                                       struct reftable_stack *st)
+{
+       int err = 0;
+       add->stack = st;
+
+       strbuf_reset(&add->lock_file_name);
+       strbuf_addstr(&add->lock_file_name, st->list_file);
+       strbuf_addstr(&add->lock_file_name, ".lock");
+
+       add->lock_file_fd = open(add->lock_file_name.buf,
+                                O_EXCL | O_CREAT | O_WRONLY, 0644);
+       if (add->lock_file_fd < 0) {
+               if (errno == EEXIST) {
+                       err = REFTABLE_LOCK_ERROR;
+               } else {
+                       err = REFTABLE_IO_ERROR;
+               }
+               goto done;
+       }
+       err = stack_uptodate(st);
+       if (err < 0)
+               goto done;
+
+       if (err > 1) {
+               err = REFTABLE_LOCK_ERROR;
+               goto done;
+       }
+
+       add->next_update_index = reftable_stack_next_update_index(st);
+done:
+       if (err) {
+               reftable_addition_close(add);
+       }
+       return err;
+}
+
+static void reftable_addition_close(struct reftable_addition *add)
+{
+       int i = 0;
+       struct strbuf nm = STRBUF_INIT;
+       for (i = 0; i < add->new_tables_len; i++) {
+               stack_filename(&nm, add->stack, add->new_tables[i]);
+               unlink(nm.buf);
+               reftable_free(add->new_tables[i]);
+               add->new_tables[i] = NULL;
+       }
+       reftable_free(add->new_tables);
+       add->new_tables = NULL;
+       add->new_tables_len = 0;
+
+       if (add->lock_file_fd > 0) {
+               close(add->lock_file_fd);
+               add->lock_file_fd = 0;
+       }
+       if (add->lock_file_name.len > 0) {
+               unlink(add->lock_file_name.buf);
+               strbuf_release(&add->lock_file_name);
+       }
+
+       strbuf_release(&nm);
+}
+
+void reftable_addition_destroy(struct reftable_addition *add)
+{
+       if (!add) {
+               return;
+       }
+       reftable_addition_close(add);
+       reftable_free(add);
+}
+
+int reftable_addition_commit(struct reftable_addition *add)
+{
+       struct strbuf table_list = STRBUF_INIT;
+       int i = 0;
+       int err = 0;
+       if (add->new_tables_len == 0)
+               goto done;
+
+       for (i = 0; i < add->stack->merged->stack_len; i++) {
+               strbuf_addstr(&table_list, add->stack->readers[i]->name);
+               strbuf_addstr(&table_list, "\n");
+       }
+       for (i = 0; i < add->new_tables_len; i++) {
+               strbuf_addstr(&table_list, add->new_tables[i]);
+               strbuf_addstr(&table_list, "\n");
+       }
+
+       err = write(add->lock_file_fd, table_list.buf, table_list.len);
+       strbuf_release(&table_list);
+       if (err < 0) {
+               err = REFTABLE_IO_ERROR;
+               goto done;
+       }
+
+       err = close(add->lock_file_fd);
+       add->lock_file_fd = 0;
+       if (err < 0) {
+               err = REFTABLE_IO_ERROR;
+               goto done;
+       }
+
+       err = rename(add->lock_file_name.buf, add->stack->list_file);
+       if (err < 0) {
+               err = REFTABLE_IO_ERROR;
+               goto done;
+       }
+
+       /* success, no more state to clean up. */
+       strbuf_release(&add->lock_file_name);
+       for (i = 0; i < add->new_tables_len; i++) {
+               reftable_free(add->new_tables[i]);
+       }
+       reftable_free(add->new_tables);
+       add->new_tables = NULL;
+       add->new_tables_len = 0;
+
+       err = reftable_stack_reload(add->stack);
+done:
+       reftable_addition_close(add);
+       return err;
+}
+
+int reftable_stack_new_addition(struct reftable_addition **dest,
+                               struct reftable_stack *st)
+{
+       int err = 0;
+       struct reftable_addition empty = REFTABLE_ADDITION_INIT;
+       *dest = reftable_calloc(sizeof(**dest));
+       **dest = empty;
+       err = reftable_stack_init_addition(*dest, st);
+       if (err) {
+               reftable_free(*dest);
+               *dest = NULL;
+       }
+       return err;
+}
+
+static int stack_try_add(struct reftable_stack *st,
+                        int (*write_table)(struct reftable_writer *wr,
+                                           void *arg),
+                        void *arg)
+{
+       struct reftable_addition add = REFTABLE_ADDITION_INIT;
+       int err = reftable_stack_init_addition(&add, st);
+       if (err < 0)
+               goto done;
+       if (err > 0) {
+               err = REFTABLE_LOCK_ERROR;
+               goto done;
+       }
+
+       err = reftable_addition_add(&add, write_table, arg);
+       if (err < 0)
+               goto done;
+
+       err = reftable_addition_commit(&add);
+done:
+       reftable_addition_close(&add);
+       return err;
+}
+
+int reftable_addition_add(struct reftable_addition *add,
+                         int (*write_table)(struct reftable_writer *wr,
+                                            void *arg),
+                         void *arg)
+{
+       struct strbuf temp_tab_file_name = STRBUF_INIT;
+       struct strbuf tab_file_name = STRBUF_INIT;
+       struct strbuf next_name = STRBUF_INIT;
+       struct reftable_writer *wr = NULL;
+       int err = 0;
+       int tab_fd = 0;
+
+       strbuf_reset(&next_name);
+       format_name(&next_name, add->next_update_index, add->next_update_index);
+
+       stack_filename(&temp_tab_file_name, add->stack, next_name.buf);
+       strbuf_addstr(&temp_tab_file_name, ".temp.XXXXXX");
+
+       tab_fd = mkstemp(temp_tab_file_name.buf);
+       if (tab_fd < 0) {
+               err = REFTABLE_IO_ERROR;
+               goto done;
+       }
+
+       wr = reftable_new_writer(reftable_fd_write, &tab_fd,
+                                &add->stack->config);
+       err = write_table(wr, arg);
+       if (err < 0)
+               goto done;
+
+       err = reftable_writer_close(wr);
+       if (err == REFTABLE_EMPTY_TABLE_ERROR) {
+               err = 0;
+               goto done;
+       }
+       if (err < 0)
+               goto done;
+
+       err = close(tab_fd);
+       tab_fd = 0;
+       if (err < 0) {
+               err = REFTABLE_IO_ERROR;
+               goto done;
+       }
+
+       err = stack_check_addition(add->stack, temp_tab_file_name.buf);
+       if (err < 0)
+               goto done;
+
+       if (wr->min_update_index < add->next_update_index) {
+               err = REFTABLE_API_ERROR;
+               goto done;
+       }
+
+       format_name(&next_name, wr->min_update_index, wr->max_update_index);
+       strbuf_addstr(&next_name, ".ref");
+
+       stack_filename(&tab_file_name, add->stack, next_name.buf);
+
+       /*
+         On windows, this relies on rand() picking a unique destination name.
+         Maybe we should do retry loop as well?
+        */
+       err = rename(temp_tab_file_name.buf, tab_file_name.buf);
+       if (err < 0) {
+               err = REFTABLE_IO_ERROR;
+               goto done;
+       }
+
+       add->new_tables = reftable_realloc(add->new_tables,
+                                          sizeof(*add->new_tables) *
+                                                  (add->new_tables_len + 1));
+       add->new_tables[add->new_tables_len] = strbuf_detach(&next_name, NULL);
+       add->new_tables_len++;
+done:
+       if (tab_fd > 0) {
+               close(tab_fd);
+               tab_fd = 0;
+       }
+       if (temp_tab_file_name.len > 0) {
+               unlink(temp_tab_file_name.buf);
+       }
+
+       strbuf_release(&temp_tab_file_name);
+       strbuf_release(&tab_file_name);
+       strbuf_release(&next_name);
+       reftable_writer_free(wr);
+       return err;
+}
+
+uint64_t reftable_stack_next_update_index(struct reftable_stack *st)
+{
+       int sz = st->merged->stack_len;
+       if (sz > 0)
+               return reftable_reader_max_update_index(st->readers[sz - 1]) +
+                      1;
+       return 1;
+}
+
+static int stack_compact_locked(struct reftable_stack *st, int first, int last,
+                               struct strbuf *temp_tab,
+                               struct reftable_log_expiry_config *config)
+{
+       struct strbuf next_name = STRBUF_INIT;
+       int tab_fd = -1;
+       struct reftable_writer *wr = NULL;
+       int err = 0;
+
+       format_name(&next_name,
+                   reftable_reader_min_update_index(st->readers[first]),
+                   reftable_reader_max_update_index(st->readers[last]));
+
+       stack_filename(temp_tab, st, next_name.buf);
+       strbuf_addstr(temp_tab, ".temp.XXXXXX");
+
+       tab_fd = mkstemp(temp_tab->buf);
+       wr = reftable_new_writer(reftable_fd_write, &tab_fd, &st->config);
+
+       err = stack_write_compact(st, wr, first, last, config);
+       if (err < 0)
+               goto done;
+       err = reftable_writer_close(wr);
+       if (err < 0)
+               goto done;
+
+       err = close(tab_fd);
+       tab_fd = 0;
+
+done:
+       reftable_writer_free(wr);
+       if (tab_fd > 0) {
+               close(tab_fd);
+               tab_fd = 0;
+       }
+       if (err != 0 && temp_tab->len > 0) {
+               unlink(temp_tab->buf);
+               strbuf_release(temp_tab);
+       }
+       strbuf_release(&next_name);
+       return err;
+}
+
+static int stack_write_compact(struct reftable_stack *st,
+                              struct reftable_writer *wr, int first, int last,
+                              struct reftable_log_expiry_config *config)
+{
+       int subtabs_len = last - first + 1;
+       struct reftable_table *subtabs = reftable_calloc(
+               sizeof(struct reftable_table) * (last - first + 1));
+       struct reftable_merged_table *mt = NULL;
+       int err = 0;
+       struct reftable_iterator it = { NULL };
+       struct reftable_ref_record ref = { NULL };
+       struct reftable_log_record log = { NULL };
+
+       uint64_t entries = 0;
+
+       int i = 0, j = 0;
+       for (i = first, j = 0; i <= last; i++) {
+               struct reftable_reader *t = st->readers[i];
+               reftable_table_from_reader(&subtabs[j++], t);
+               st->stats.bytes += t->size;
+       }
+       reftable_writer_set_limits(wr, st->readers[first]->min_update_index,
+                                  st->readers[last]->max_update_index);
+
+       err = reftable_new_merged_table(&mt, subtabs, subtabs_len,
+                                       st->config.hash_id);
+       if (err < 0) {
+               reftable_free(subtabs);
+               goto done;
+       }
+
+       err = reftable_merged_table_seek_ref(mt, &it, "");
+       if (err < 0)
+               goto done;
+
+       while (1) {
+               err = reftable_iterator_next_ref(&it, &ref);
+               if (err > 0) {
+                       err = 0;
+                       break;
+               }
+               if (err < 0) {
+                       break;
+               }
+
+               if (first == 0 && reftable_ref_record_is_deletion(&ref)) {
+                       continue;
+               }
+
+               err = reftable_writer_add_ref(wr, &ref);
+               if (err < 0) {
+                       break;
+               }
+               entries++;
+       }
+       reftable_iterator_destroy(&it);
+
+       err = reftable_merged_table_seek_log(mt, &it, "");
+       if (err < 0)
+               goto done;
+
+       while (1) {
+               err = reftable_iterator_next_log(&it, &log);
+               if (err > 0) {
+                       err = 0;
+                       break;
+               }
+               if (err < 0) {
+                       break;
+               }
+               if (first == 0 && reftable_log_record_is_deletion(&log)) {
+                       continue;
+               }
+
+               if (config && config->min_update_index > 0 &&
+                   log.update_index < config->min_update_index) {
+                       continue;
+               }
+
+               if (config && config->time > 0 &&
+                   log.value.update.time < config->time) {
+                       continue;
+               }
+
+               err = reftable_writer_add_log(wr, &log);
+               if (err < 0) {
+                       break;
+               }
+               entries++;
+       }
+
+done:
+       reftable_iterator_destroy(&it);
+       if (mt) {
+               merged_table_release(mt);
+               reftable_merged_table_free(mt);
+       }
+       reftable_ref_record_release(&ref);
+       reftable_log_record_release(&log);
+       st->stats.entries_written += entries;
+       return err;
+}
+
+/* <  0: error. 0 == OK, > 0 attempt failed; could retry. */
+static int stack_compact_range(struct reftable_stack *st, int first, int last,
+                              struct reftable_log_expiry_config *expiry)
+{
+       struct strbuf temp_tab_file_name = STRBUF_INIT;
+       struct strbuf new_table_name = STRBUF_INIT;
+       struct strbuf lock_file_name = STRBUF_INIT;
+       struct strbuf ref_list_contents = STRBUF_INIT;
+       struct strbuf new_table_path = STRBUF_INIT;
+       int err = 0;
+       int have_lock = 0;
+       int lock_file_fd = 0;
+       int compact_count = last - first + 1;
+       char **listp = NULL;
+       char **delete_on_success =
+               reftable_calloc(sizeof(char *) * (compact_count + 1));
+       char **subtable_locks =
+               reftable_calloc(sizeof(char *) * (compact_count + 1));
+       int i = 0;
+       int j = 0;
+       int is_empty_table = 0;
+
+       if (first > last || (!expiry && first == last)) {
+               err = 0;
+               goto done;
+       }
+
+       st->stats.attempts++;
+
+       strbuf_reset(&lock_file_name);
+       strbuf_addstr(&lock_file_name, st->list_file);
+       strbuf_addstr(&lock_file_name, ".lock");
+
+       lock_file_fd =
+               open(lock_file_name.buf, O_EXCL | O_CREAT | O_WRONLY, 0644);
+       if (lock_file_fd < 0) {
+               if (errno == EEXIST) {
+                       err = 1;
+               } else {
+                       err = REFTABLE_IO_ERROR;
+               }
+               goto done;
+       }
+       /* Don't want to write to the lock for now.  */
+       close(lock_file_fd);
+       lock_file_fd = 0;
+
+       have_lock = 1;
+       err = stack_uptodate(st);
+       if (err != 0)
+               goto done;
+
+       for (i = first, j = 0; i <= last; i++) {
+               struct strbuf subtab_file_name = STRBUF_INIT;
+               struct strbuf subtab_lock = STRBUF_INIT;
+               int sublock_file_fd = -1;
+
+               stack_filename(&subtab_file_name, st,
+                              reader_name(st->readers[i]));
+
+               strbuf_reset(&subtab_lock);
+               strbuf_addbuf(&subtab_lock, &subtab_file_name);
+               strbuf_addstr(&subtab_lock, ".lock");
+
+               sublock_file_fd = open(subtab_lock.buf,
+                                      O_EXCL | O_CREAT | O_WRONLY, 0644);
+               if (sublock_file_fd > 0) {
+                       close(sublock_file_fd);
+               } else if (sublock_file_fd < 0) {
+                       if (errno == EEXIST) {
+                               err = 1;
+                       } else {
+                               err = REFTABLE_IO_ERROR;
+                       }
+               }
+
+               subtable_locks[j] = subtab_lock.buf;
+               delete_on_success[j] = subtab_file_name.buf;
+               j++;
+
+               if (err != 0)
+                       goto done;
+       }
+
+       err = unlink(lock_file_name.buf);
+       if (err < 0)
+               goto done;
+       have_lock = 0;
+
+       err = stack_compact_locked(st, first, last, &temp_tab_file_name,
+                                  expiry);
+       /* Compaction + tombstones can create an empty table out of non-empty
+        * tables. */
+       is_empty_table = (err == REFTABLE_EMPTY_TABLE_ERROR);
+       if (is_empty_table) {
+               err = 0;
+       }
+       if (err < 0)
+               goto done;
+
+       lock_file_fd =
+               open(lock_file_name.buf, O_EXCL | O_CREAT | O_WRONLY, 0644);
+       if (lock_file_fd < 0) {
+               if (errno == EEXIST) {
+                       err = 1;
+               } else {
+                       err = REFTABLE_IO_ERROR;
+               }
+               goto done;
+       }
+       have_lock = 1;
+
+       format_name(&new_table_name, st->readers[first]->min_update_index,
+                   st->readers[last]->max_update_index);
+       strbuf_addstr(&new_table_name, ".ref");
+
+       stack_filename(&new_table_path, st, new_table_name.buf);
+
+       if (!is_empty_table) {
+               /* retry? */
+               err = rename(temp_tab_file_name.buf, new_table_path.buf);
+               if (err < 0) {
+                       err = REFTABLE_IO_ERROR;
+                       goto done;
+               }
+       }
+
+       for (i = 0; i < first; i++) {
+               strbuf_addstr(&ref_list_contents, st->readers[i]->name);
+               strbuf_addstr(&ref_list_contents, "\n");
+       }
+       if (!is_empty_table) {
+               strbuf_addbuf(&ref_list_contents, &new_table_name);
+               strbuf_addstr(&ref_list_contents, "\n");
+       }
+       for (i = last + 1; i < st->merged->stack_len; i++) {
+               strbuf_addstr(&ref_list_contents, st->readers[i]->name);
+               strbuf_addstr(&ref_list_contents, "\n");
+       }
+
+       err = write(lock_file_fd, ref_list_contents.buf, ref_list_contents.len);
+       if (err < 0) {
+               err = REFTABLE_IO_ERROR;
+               unlink(new_table_path.buf);
+               goto done;
+       }
+       err = close(lock_file_fd);
+       lock_file_fd = 0;
+       if (err < 0) {
+               err = REFTABLE_IO_ERROR;
+               unlink(new_table_path.buf);
+               goto done;
+       }
+
+       err = rename(lock_file_name.buf, st->list_file);
+       if (err < 0) {
+               err = REFTABLE_IO_ERROR;
+               unlink(new_table_path.buf);
+               goto done;
+       }
+       have_lock = 0;
+
+       /* Reload the stack before deleting. On windows, we can only delete the
+          files after we closed them.
+       */
+       err = reftable_stack_reload_maybe_reuse(st, first < last);
+
+       listp = delete_on_success;
+       while (*listp) {
+               if (strcmp(*listp, new_table_path.buf)) {
+                       unlink(*listp);
+               }
+               listp++;
+       }
+
+done:
+       free_names(delete_on_success);
+
+       listp = subtable_locks;
+       while (*listp) {
+               unlink(*listp);
+               listp++;
+       }
+       free_names(subtable_locks);
+       if (lock_file_fd > 0) {
+               close(lock_file_fd);
+               lock_file_fd = 0;
+       }
+       if (have_lock) {
+               unlink(lock_file_name.buf);
+       }
+       strbuf_release(&new_table_name);
+       strbuf_release(&new_table_path);
+       strbuf_release(&ref_list_contents);
+       strbuf_release(&temp_tab_file_name);
+       strbuf_release(&lock_file_name);
+       return err;
+}
+
+int reftable_stack_compact_all(struct reftable_stack *st,
+                              struct reftable_log_expiry_config *config)
+{
+       return stack_compact_range(st, 0, st->merged->stack_len - 1, config);
+}
+
+static int stack_compact_range_stats(struct reftable_stack *st, int first,
+                                    int last,
+                                    struct reftable_log_expiry_config *config)
+{
+       int err = stack_compact_range(st, first, last, config);
+       if (err > 0) {
+               st->stats.failures++;
+       }
+       return err;
+}
+
+static int segment_size(struct segment *s)
+{
+       return s->end - s->start;
+}
+
+int fastlog2(uint64_t sz)
+{
+       int l = 0;
+       if (sz == 0)
+               return 0;
+       for (; sz; sz /= 2) {
+               l++;
+       }
+       return l - 1;
+}
+
+struct segment *sizes_to_segments(int *seglen, uint64_t *sizes, int n)
+{
+       struct segment *segs = reftable_calloc(sizeof(struct segment) * n);
+       int next = 0;
+       struct segment cur = { 0 };
+       int i = 0;
+
+       if (n == 0) {
+               *seglen = 0;
+               return segs;
+       }
+       for (i = 0; i < n; i++) {
+               int log = fastlog2(sizes[i]);
+               if (cur.log != log && cur.bytes > 0) {
+                       struct segment fresh = {
+                               .start = i,
+                       };
+
+                       segs[next++] = cur;
+                       cur = fresh;
+               }
+
+               cur.log = log;
+               cur.end = i + 1;
+               cur.bytes += sizes[i];
+       }
+       segs[next++] = cur;
+       *seglen = next;
+       return segs;
+}
+
+struct segment suggest_compaction_segment(uint64_t *sizes, int n)
+{
+       int seglen = 0;
+       struct segment *segs = sizes_to_segments(&seglen, sizes, n);
+       struct segment min_seg = {
+               .log = 64,
+       };
+       int i = 0;
+       for (i = 0; i < seglen; i++) {
+               if (segment_size(&segs[i]) == 1) {
+                       continue;
+               }
+
+               if (segs[i].log < min_seg.log) {
+                       min_seg = segs[i];
+               }
+       }
+
+       while (min_seg.start > 0) {
+               int prev = min_seg.start - 1;
+               if (fastlog2(min_seg.bytes) < fastlog2(sizes[prev])) {
+                       break;
+               }
+
+               min_seg.start = prev;
+               min_seg.bytes += sizes[prev];
+       }
+
+       reftable_free(segs);
+       return min_seg;
+}
+
+static uint64_t *stack_table_sizes_for_compaction(struct reftable_stack *st)
+{
+       uint64_t *sizes =
+               reftable_calloc(sizeof(uint64_t) * st->merged->stack_len);
+       int version = (st->config.hash_id == GIT_SHA1_FORMAT_ID) ? 1 : 2;
+       int overhead = header_size(version) - 1;
+       int i = 0;
+       for (i = 0; i < st->merged->stack_len; i++) {
+               sizes[i] = st->readers[i]->size - overhead;
+       }
+       return sizes;
+}
+
+int reftable_stack_auto_compact(struct reftable_stack *st)
+{
+       uint64_t *sizes = stack_table_sizes_for_compaction(st);
+       struct segment seg =
+               suggest_compaction_segment(sizes, st->merged->stack_len);
+       reftable_free(sizes);
+       if (segment_size(&seg) > 0)
+               return stack_compact_range_stats(st, seg.start, seg.end - 1,
+                                                NULL);
+
+       return 0;
+}
+
+struct reftable_compaction_stats *
+reftable_stack_compaction_stats(struct reftable_stack *st)
+{
+       return &st->stats;
+}
+
+int reftable_stack_read_ref(struct reftable_stack *st, const char *refname,
+                           struct reftable_ref_record *ref)
+{
+       struct reftable_table tab = { NULL };
+       reftable_table_from_merged_table(&tab, reftable_stack_merged_table(st));
+       return reftable_table_read_ref(&tab, refname, ref);
+}
+
+int reftable_stack_read_log(struct reftable_stack *st, const char *refname,
+                           struct reftable_log_record *log)
+{
+       struct reftable_iterator it = { NULL };
+       struct reftable_merged_table *mt = reftable_stack_merged_table(st);
+       int err = reftable_merged_table_seek_log(mt, &it, refname);
+       if (err)
+               goto done;
+
+       err = reftable_iterator_next_log(&it, log);
+       if (err)
+               goto done;
+
+       if (strcmp(log->refname, refname) ||
+           reftable_log_record_is_deletion(log)) {
+               err = 1;
+               goto done;
+       }
+
+done:
+       if (err) {
+               reftable_log_record_release(log);
+       }
+       reftable_iterator_destroy(&it);
+       return err;
+}
+
+static int stack_check_addition(struct reftable_stack *st,
+                               const char *new_tab_name)
+{
+       int err = 0;
+       struct reftable_block_source src = { NULL };
+       struct reftable_reader *rd = NULL;
+       struct reftable_table tab = { NULL };
+       struct reftable_ref_record *refs = NULL;
+       struct reftable_iterator it = { NULL };
+       int cap = 0;
+       int len = 0;
+       int i = 0;
+
+       if (st->config.skip_name_check)
+               return 0;
+
+       err = reftable_block_source_from_file(&src, new_tab_name);
+       if (err < 0)
+               goto done;
+
+       err = reftable_new_reader(&rd, &src, new_tab_name);
+       if (err < 0)
+               goto done;
+
+       err = reftable_reader_seek_ref(rd, &it, "");
+       if (err > 0) {
+               err = 0;
+               goto done;
+       }
+       if (err < 0)
+               goto done;
+
+       while (1) {
+               struct reftable_ref_record ref = { NULL };
+               err = reftable_iterator_next_ref(&it, &ref);
+               if (err > 0) {
+                       break;
+               }
+               if (err < 0)
+                       goto done;
+
+               if (len >= cap) {
+                       cap = 2 * cap + 1;
+                       refs = reftable_realloc(refs, cap * sizeof(refs[0]));
+               }
+
+               refs[len++] = ref;
+       }
+
+       reftable_table_from_merged_table(&tab, reftable_stack_merged_table(st));
+
+       err = validate_ref_record_addition(tab, refs, len);
+
+done:
+       for (i = 0; i < len; i++) {
+               reftable_ref_record_release(&refs[i]);
+       }
+
+       free(refs);
+       reftable_iterator_destroy(&it);
+       reftable_reader_free(rd);
+       return err;
+}
+
+static int is_table_name(const char *s)
+{
+       const char *dot = strrchr(s, '.');
+       return dot && !strcmp(dot, ".ref");
+}
+
+static void remove_maybe_stale_table(struct reftable_stack *st, uint64_t max,
+                                    const char *name)
+{
+       int err = 0;
+       uint64_t update_idx = 0;
+       struct reftable_block_source src = { NULL };
+       struct reftable_reader *rd = NULL;
+       struct strbuf table_path = STRBUF_INIT;
+       stack_filename(&table_path, st, name);
+
+       err = reftable_block_source_from_file(&src, table_path.buf);
+       if (err < 0)
+               goto done;
+
+       err = reftable_new_reader(&rd, &src, name);
+       if (err < 0)
+               goto done;
+
+       update_idx = reftable_reader_max_update_index(rd);
+       reftable_reader_free(rd);
+
+       if (update_idx <= max) {
+               unlink(table_path.buf);
+       }
+done:
+       strbuf_release(&table_path);
+}
+
+static int reftable_stack_clean_locked(struct reftable_stack *st)
+{
+       uint64_t max = reftable_merged_table_max_update_index(
+               reftable_stack_merged_table(st));
+       DIR *dir = opendir(st->reftable_dir);
+       struct dirent *d = NULL;
+       if (!dir) {
+               return REFTABLE_IO_ERROR;
+       }
+
+       while ((d = readdir(dir))) {
+               int i = 0;
+               int found = 0;
+               if (!is_table_name(d->d_name))
+                       continue;
+
+               for (i = 0; !found && i < st->readers_len; i++) {
+                       found = !strcmp(reader_name(st->readers[i]), d->d_name);
+               }
+               if (found)
+                       continue;
+
+               remove_maybe_stale_table(st, max, d->d_name);
+       }
+
+       closedir(dir);
+       return 0;
+}
+
+int reftable_stack_clean(struct reftable_stack *st)
+{
+       struct reftable_addition *add = NULL;
+       int err = reftable_stack_new_addition(&add, st);
+       if (err < 0) {
+               goto done;
+       }
+
+       err = reftable_stack_reload(st);
+       if (err < 0) {
+               goto done;
+       }
+
+       err = reftable_stack_clean_locked(st);
+
+done:
+       reftable_addition_destroy(add);
+       return err;
+}
+
+int reftable_stack_print_directory(const char *stackdir, uint32_t hash_id)
+{
+       struct reftable_stack *stack = NULL;
+       struct reftable_write_options cfg = { .hash_id = hash_id };
+       struct reftable_merged_table *merged = NULL;
+       struct reftable_table table = { NULL };
+
+       int err = reftable_new_stack(&stack, stackdir, cfg);
+       if (err < 0)
+               goto done;
+
+       merged = reftable_stack_merged_table(stack);
+       reftable_table_from_merged_table(&table, merged);
+       err = reftable_table_print(&table);
+done:
+       if (stack)
+               reftable_stack_destroy(stack);
+       return err;
+}
diff --git a/reftable/stack.h b/reftable/stack.h
new file mode 100644 (file)
index 0000000..f570058
--- /dev/null
@@ -0,0 +1,41 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#ifndef STACK_H
+#define STACK_H
+
+#include "system.h"
+#include "reftable-writer.h"
+#include "reftable-stack.h"
+
+struct reftable_stack {
+       char *list_file;
+       char *reftable_dir;
+       int disable_auto_compact;
+
+       struct reftable_write_options config;
+
+       struct reftable_reader **readers;
+       size_t readers_len;
+       struct reftable_merged_table *merged;
+       struct reftable_compaction_stats stats;
+};
+
+int read_lines(const char *filename, char ***lines);
+
+struct segment {
+       int start, end;
+       int log;
+       uint64_t bytes;
+};
+
+int fastlog2(uint64_t sz);
+struct segment *sizes_to_segments(int *seglen, uint64_t *sizes, int n);
+struct segment suggest_compaction_segment(uint64_t *sizes, int n);
+
+#endif
diff --git a/reftable/stack_test.c b/reftable/stack_test.c
new file mode 100644 (file)
index 0000000..eb0b722
--- /dev/null
@@ -0,0 +1,953 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#include "stack.h"
+
+#include "system.h"
+
+#include "reftable-reader.h"
+#include "merged.h"
+#include "basics.h"
+#include "constants.h"
+#include "record.h"
+#include "test_framework.h"
+#include "reftable-tests.h"
+
+#include <sys/types.h>
+#include <dirent.h>
+
+static void clear_dir(const char *dirname)
+{
+       struct strbuf path = STRBUF_INIT;
+       strbuf_addstr(&path, dirname);
+       remove_dir_recursively(&path, 0);
+       strbuf_release(&path);
+}
+
+static int count_dir_entries(const char *dirname)
+{
+       DIR *dir = opendir(dirname);
+       int len = 0;
+       struct dirent *d;
+       if (dir == NULL)
+               return 0;
+
+       while ((d = readdir(dir))) {
+               if (!strcmp(d->d_name, "..") || !strcmp(d->d_name, "."))
+                       continue;
+               len++;
+       }
+       closedir(dir);
+       return len;
+}
+
+/*
+ * Work linenumber into the tempdir, so we can see which tests forget to
+ * cleanup.
+ */
+static char *get_tmp_template(int linenumber)
+{
+       const char *tmp = getenv("TMPDIR");
+       static char template[1024];
+       snprintf(template, sizeof(template) - 1, "%s/stack_test-%d.XXXXXX",
+                tmp ? tmp : "/tmp", linenumber);
+       return template;
+}
+
+static char *get_tmp_dir(int linenumber)
+{
+       char *dir = get_tmp_template(linenumber);
+       EXPECT(mkdtemp(dir));
+       return dir;
+}
+
+static void test_read_file(void)
+{
+       char *fn = get_tmp_template(__LINE__);
+       int fd = mkstemp(fn);
+       char out[1024] = "line1\n\nline2\nline3";
+       int n, err;
+       char **names = NULL;
+       char *want[] = { "line1", "line2", "line3" };
+       int i = 0;
+
+       EXPECT(fd > 0);
+       n = write(fd, out, strlen(out));
+       EXPECT(n == strlen(out));
+       err = close(fd);
+       EXPECT(err >= 0);
+
+       err = read_lines(fn, &names);
+       EXPECT_ERR(err);
+
+       for (i = 0; names[i]; i++) {
+               EXPECT(0 == strcmp(want[i], names[i]));
+       }
+       free_names(names);
+       remove(fn);
+}
+
+static void test_parse_names(void)
+{
+       char buf[] = "line\n";
+       char **names = NULL;
+       parse_names(buf, strlen(buf), &names);
+
+       EXPECT(NULL != names[0]);
+       EXPECT(0 == strcmp(names[0], "line"));
+       EXPECT(NULL == names[1]);
+       free_names(names);
+}
+
+static void test_names_equal(void)
+{
+       char *a[] = { "a", "b", "c", NULL };
+       char *b[] = { "a", "b", "d", NULL };
+       char *c[] = { "a", "b", NULL };
+
+       EXPECT(names_equal(a, a));
+       EXPECT(!names_equal(a, b));
+       EXPECT(!names_equal(a, c));
+}
+
+static int write_test_ref(struct reftable_writer *wr, void *arg)
+{
+       struct reftable_ref_record *ref = arg;
+       reftable_writer_set_limits(wr, ref->update_index, ref->update_index);
+       return reftable_writer_add_ref(wr, ref);
+}
+
+struct write_log_arg {
+       struct reftable_log_record *log;
+       uint64_t update_index;
+};
+
+static int write_test_log(struct reftable_writer *wr, void *arg)
+{
+       struct write_log_arg *wla = arg;
+
+       reftable_writer_set_limits(wr, wla->update_index, wla->update_index);
+       return reftable_writer_add_log(wr, wla->log);
+}
+
+static void test_reftable_stack_add_one(void)
+{
+       char *dir = get_tmp_dir(__LINE__);
+
+       struct reftable_write_options cfg = { 0 };
+       struct reftable_stack *st = NULL;
+       int err;
+       struct reftable_ref_record ref = {
+               .refname = "HEAD",
+               .update_index = 1,
+               .value_type = REFTABLE_REF_SYMREF,
+               .value.symref = "master",
+       };
+       struct reftable_ref_record dest = { NULL };
+
+
+       err = reftable_new_stack(&st, dir, cfg);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_add(st, &write_test_ref, &ref);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_read_ref(st, ref.refname, &dest);
+       EXPECT_ERR(err);
+       EXPECT(0 == strcmp("master", dest.value.symref));
+
+       printf("testing print functionality:\n");
+       err = reftable_stack_print_directory(dir, GIT_SHA1_FORMAT_ID);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_print_directory(dir, GIT_SHA256_FORMAT_ID);
+       EXPECT(err == REFTABLE_FORMAT_ERROR);
+
+       reftable_ref_record_release(&dest);
+       reftable_stack_destroy(st);
+       clear_dir(dir);
+}
+
+static void test_reftable_stack_uptodate(void)
+{
+       struct reftable_write_options cfg = { 0 };
+       struct reftable_stack *st1 = NULL;
+       struct reftable_stack *st2 = NULL;
+       char *dir = get_tmp_dir(__LINE__);
+
+       int err;
+       struct reftable_ref_record ref1 = {
+               .refname = "HEAD",
+               .update_index = 1,
+               .value_type = REFTABLE_REF_SYMREF,
+               .value.symref = "master",
+       };
+       struct reftable_ref_record ref2 = {
+               .refname = "branch2",
+               .update_index = 2,
+               .value_type = REFTABLE_REF_SYMREF,
+               .value.symref = "master",
+       };
+
+
+       /* simulate multi-process access to the same stack
+          by creating two stacks for the same directory.
+        */
+       err = reftable_new_stack(&st1, dir, cfg);
+       EXPECT_ERR(err);
+
+       err = reftable_new_stack(&st2, dir, cfg);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_add(st1, &write_test_ref, &ref1);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_add(st2, &write_test_ref, &ref2);
+       EXPECT(err == REFTABLE_LOCK_ERROR);
+
+       err = reftable_stack_reload(st2);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_add(st2, &write_test_ref, &ref2);
+       EXPECT_ERR(err);
+       reftable_stack_destroy(st1);
+       reftable_stack_destroy(st2);
+       clear_dir(dir);
+}
+
+static void test_reftable_stack_transaction_api(void)
+{
+       char *dir = get_tmp_dir(__LINE__);
+
+       struct reftable_write_options cfg = { 0 };
+       struct reftable_stack *st = NULL;
+       int err;
+       struct reftable_addition *add = NULL;
+
+       struct reftable_ref_record ref = {
+               .refname = "HEAD",
+               .update_index = 1,
+               .value_type = REFTABLE_REF_SYMREF,
+               .value.symref = "master",
+       };
+       struct reftable_ref_record dest = { NULL };
+
+
+       err = reftable_new_stack(&st, dir, cfg);
+       EXPECT_ERR(err);
+
+       reftable_addition_destroy(add);
+
+       err = reftable_stack_new_addition(&add, st);
+       EXPECT_ERR(err);
+
+       err = reftable_addition_add(add, &write_test_ref, &ref);
+       EXPECT_ERR(err);
+
+       err = reftable_addition_commit(add);
+       EXPECT_ERR(err);
+
+       reftable_addition_destroy(add);
+
+       err = reftable_stack_read_ref(st, ref.refname, &dest);
+       EXPECT_ERR(err);
+       EXPECT(REFTABLE_REF_SYMREF == dest.value_type);
+       EXPECT(0 == strcmp("master", dest.value.symref));
+
+       reftable_ref_record_release(&dest);
+       reftable_stack_destroy(st);
+       clear_dir(dir);
+}
+
+static void test_reftable_stack_validate_refname(void)
+{
+       struct reftable_write_options cfg = { 0 };
+       struct reftable_stack *st = NULL;
+       int err;
+       char *dir = get_tmp_dir(__LINE__);
+
+       int i;
+       struct reftable_ref_record ref = {
+               .refname = "a/b",
+               .update_index = 1,
+               .value_type = REFTABLE_REF_SYMREF,
+               .value.symref = "master",
+       };
+       char *additions[] = { "a", "a/b/c" };
+
+       err = reftable_new_stack(&st, dir, cfg);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_add(st, &write_test_ref, &ref);
+       EXPECT_ERR(err);
+
+       for (i = 0; i < ARRAY_SIZE(additions); i++) {
+               struct reftable_ref_record ref = {
+                       .refname = additions[i],
+                       .update_index = 1,
+                       .value_type = REFTABLE_REF_SYMREF,
+                       .value.symref = "master",
+               };
+
+               err = reftable_stack_add(st, &write_test_ref, &ref);
+               EXPECT(err == REFTABLE_NAME_CONFLICT);
+       }
+
+       reftable_stack_destroy(st);
+       clear_dir(dir);
+}
+
+static int write_error(struct reftable_writer *wr, void *arg)
+{
+       return *((int *)arg);
+}
+
+static void test_reftable_stack_update_index_check(void)
+{
+       char *dir = get_tmp_dir(__LINE__);
+
+       struct reftable_write_options cfg = { 0 };
+       struct reftable_stack *st = NULL;
+       int err;
+       struct reftable_ref_record ref1 = {
+               .refname = "name1",
+               .update_index = 1,
+               .value_type = REFTABLE_REF_SYMREF,
+               .value.symref = "master",
+       };
+       struct reftable_ref_record ref2 = {
+               .refname = "name2",
+               .update_index = 1,
+               .value_type = REFTABLE_REF_SYMREF,
+               .value.symref = "master",
+       };
+
+       err = reftable_new_stack(&st, dir, cfg);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_add(st, &write_test_ref, &ref1);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_add(st, &write_test_ref, &ref2);
+       EXPECT(err == REFTABLE_API_ERROR);
+       reftable_stack_destroy(st);
+       clear_dir(dir);
+}
+
+static void test_reftable_stack_lock_failure(void)
+{
+       char *dir = get_tmp_dir(__LINE__);
+
+       struct reftable_write_options cfg = { 0 };
+       struct reftable_stack *st = NULL;
+       int err, i;
+
+       err = reftable_new_stack(&st, dir, cfg);
+       EXPECT_ERR(err);
+       for (i = -1; i != REFTABLE_EMPTY_TABLE_ERROR; i--) {
+               err = reftable_stack_add(st, &write_error, &i);
+               EXPECT(err == i);
+       }
+
+       reftable_stack_destroy(st);
+       clear_dir(dir);
+}
+
+static void test_reftable_stack_add(void)
+{
+       int i = 0;
+       int err = 0;
+       struct reftable_write_options cfg = {
+               .exact_log_message = 1,
+       };
+       struct reftable_stack *st = NULL;
+       char *dir = get_tmp_dir(__LINE__);
+
+       struct reftable_ref_record refs[2] = { { NULL } };
+       struct reftable_log_record logs[2] = { { NULL } };
+       int N = ARRAY_SIZE(refs);
+
+
+       err = reftable_new_stack(&st, dir, cfg);
+       EXPECT_ERR(err);
+       st->disable_auto_compact = 1;
+
+       for (i = 0; i < N; i++) {
+               char buf[256];
+               snprintf(buf, sizeof(buf), "branch%02d", i);
+               refs[i].refname = xstrdup(buf);
+               refs[i].update_index = i + 1;
+               refs[i].value_type = REFTABLE_REF_VAL1;
+               refs[i].value.val1 = reftable_malloc(GIT_SHA1_RAWSZ);
+               set_test_hash(refs[i].value.val1, i);
+
+               logs[i].refname = xstrdup(buf);
+               logs[i].update_index = N + i + 1;
+               logs[i].value_type = REFTABLE_LOG_UPDATE;
+
+               logs[i].value.update.new_hash = reftable_malloc(GIT_SHA1_RAWSZ);
+               logs[i].value.update.email = xstrdup("identity@invalid");
+               set_test_hash(logs[i].value.update.new_hash, i);
+       }
+
+       for (i = 0; i < N; i++) {
+               int err = reftable_stack_add(st, &write_test_ref, &refs[i]);
+               EXPECT_ERR(err);
+       }
+
+       for (i = 0; i < N; i++) {
+               struct write_log_arg arg = {
+                       .log = &logs[i],
+                       .update_index = reftable_stack_next_update_index(st),
+               };
+               int err = reftable_stack_add(st, &write_test_log, &arg);
+               EXPECT_ERR(err);
+       }
+
+       err = reftable_stack_compact_all(st, NULL);
+       EXPECT_ERR(err);
+
+       for (i = 0; i < N; i++) {
+               struct reftable_ref_record dest = { NULL };
+
+               int err = reftable_stack_read_ref(st, refs[i].refname, &dest);
+               EXPECT_ERR(err);
+               EXPECT(reftable_ref_record_equal(&dest, refs + i,
+                                                GIT_SHA1_RAWSZ));
+               reftable_ref_record_release(&dest);
+       }
+
+       for (i = 0; i < N; i++) {
+               struct reftable_log_record dest = { NULL };
+               int err = reftable_stack_read_log(st, refs[i].refname, &dest);
+               EXPECT_ERR(err);
+               EXPECT(reftable_log_record_equal(&dest, logs + i,
+                                                GIT_SHA1_RAWSZ));
+               reftable_log_record_release(&dest);
+       }
+
+       /* cleanup */
+       reftable_stack_destroy(st);
+       for (i = 0; i < N; i++) {
+               reftable_ref_record_release(&refs[i]);
+               reftable_log_record_release(&logs[i]);
+       }
+       clear_dir(dir);
+}
+
+static void test_reftable_stack_log_normalize(void)
+{
+       int err = 0;
+       struct reftable_write_options cfg = {
+               0,
+       };
+       struct reftable_stack *st = NULL;
+       char *dir = get_tmp_dir(__LINE__);
+
+       uint8_t h1[GIT_SHA1_RAWSZ] = { 0x01 }, h2[GIT_SHA1_RAWSZ] = { 0x02 };
+
+       struct reftable_log_record input = { .refname = "branch",
+                                            .update_index = 1,
+                                            .value_type = REFTABLE_LOG_UPDATE,
+                                            .value = { .update = {
+                                                               .new_hash = h1,
+                                                               .old_hash = h2,
+                                                       } } };
+       struct reftable_log_record dest = {
+               .update_index = 0,
+       };
+       struct write_log_arg arg = {
+               .log = &input,
+               .update_index = 1,
+       };
+
+       err = reftable_new_stack(&st, dir, cfg);
+       EXPECT_ERR(err);
+
+       input.value.update.message = "one\ntwo";
+       err = reftable_stack_add(st, &write_test_log, &arg);
+       EXPECT(err == REFTABLE_API_ERROR);
+
+       input.value.update.message = "one";
+       err = reftable_stack_add(st, &write_test_log, &arg);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_read_log(st, input.refname, &dest);
+       EXPECT_ERR(err);
+       EXPECT(0 == strcmp(dest.value.update.message, "one\n"));
+
+       input.value.update.message = "two\n";
+       arg.update_index = 2;
+       err = reftable_stack_add(st, &write_test_log, &arg);
+       EXPECT_ERR(err);
+       err = reftable_stack_read_log(st, input.refname, &dest);
+       EXPECT_ERR(err);
+       EXPECT(0 == strcmp(dest.value.update.message, "two\n"));
+
+       /* cleanup */
+       reftable_stack_destroy(st);
+       reftable_log_record_release(&dest);
+       clear_dir(dir);
+}
+
+static void test_reftable_stack_tombstone(void)
+{
+       int i = 0;
+       char *dir = get_tmp_dir(__LINE__);
+
+       struct reftable_write_options cfg = { 0 };
+       struct reftable_stack *st = NULL;
+       int err;
+       struct reftable_ref_record refs[2] = { { NULL } };
+       struct reftable_log_record logs[2] = { { NULL } };
+       int N = ARRAY_SIZE(refs);
+       struct reftable_ref_record dest = { NULL };
+       struct reftable_log_record log_dest = { NULL };
+
+
+       err = reftable_new_stack(&st, dir, cfg);
+       EXPECT_ERR(err);
+
+       /* even entries add the refs, odd entries delete them. */
+       for (i = 0; i < N; i++) {
+               const char *buf = "branch";
+               refs[i].refname = xstrdup(buf);
+               refs[i].update_index = i + 1;
+               if (i % 2 == 0) {
+                       refs[i].value_type = REFTABLE_REF_VAL1;
+                       refs[i].value.val1 = reftable_malloc(GIT_SHA1_RAWSZ);
+                       set_test_hash(refs[i].value.val1, i);
+               }
+
+               logs[i].refname = xstrdup(buf);
+               /* update_index is part of the key. */
+               logs[i].update_index = 42;
+               if (i % 2 == 0) {
+                       logs[i].value_type = REFTABLE_LOG_UPDATE;
+                       logs[i].value.update.new_hash =
+                               reftable_malloc(GIT_SHA1_RAWSZ);
+                       set_test_hash(logs[i].value.update.new_hash, i);
+                       logs[i].value.update.email =
+                               xstrdup("identity@invalid");
+               }
+       }
+       for (i = 0; i < N; i++) {
+               int err = reftable_stack_add(st, &write_test_ref, &refs[i]);
+               EXPECT_ERR(err);
+       }
+
+       for (i = 0; i < N; i++) {
+               struct write_log_arg arg = {
+                       .log = &logs[i],
+                       .update_index = reftable_stack_next_update_index(st),
+               };
+               int err = reftable_stack_add(st, &write_test_log, &arg);
+               EXPECT_ERR(err);
+       }
+
+       err = reftable_stack_read_ref(st, "branch", &dest);
+       EXPECT(err == 1);
+       reftable_ref_record_release(&dest);
+
+       err = reftable_stack_read_log(st, "branch", &log_dest);
+       EXPECT(err == 1);
+       reftable_log_record_release(&log_dest);
+
+       err = reftable_stack_compact_all(st, NULL);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_read_ref(st, "branch", &dest);
+       EXPECT(err == 1);
+
+       err = reftable_stack_read_log(st, "branch", &log_dest);
+       EXPECT(err == 1);
+       reftable_ref_record_release(&dest);
+       reftable_log_record_release(&log_dest);
+
+       /* cleanup */
+       reftable_stack_destroy(st);
+       for (i = 0; i < N; i++) {
+               reftable_ref_record_release(&refs[i]);
+               reftable_log_record_release(&logs[i]);
+       }
+       clear_dir(dir);
+}
+
+static void test_reftable_stack_hash_id(void)
+{
+       char *dir = get_tmp_dir(__LINE__);
+
+       struct reftable_write_options cfg = { 0 };
+       struct reftable_stack *st = NULL;
+       int err;
+
+       struct reftable_ref_record ref = {
+               .refname = "master",
+               .value_type = REFTABLE_REF_SYMREF,
+               .value.symref = "target",
+               .update_index = 1,
+       };
+       struct reftable_write_options cfg32 = { .hash_id = GIT_SHA256_FORMAT_ID };
+       struct reftable_stack *st32 = NULL;
+       struct reftable_write_options cfg_default = { 0 };
+       struct reftable_stack *st_default = NULL;
+       struct reftable_ref_record dest = { NULL };
+
+       err = reftable_new_stack(&st, dir, cfg);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_add(st, &write_test_ref, &ref);
+       EXPECT_ERR(err);
+
+       /* can't read it with the wrong hash ID. */
+       err = reftable_new_stack(&st32, dir, cfg32);
+       EXPECT(err == REFTABLE_FORMAT_ERROR);
+
+       /* check that we can read it back with default config too. */
+       err = reftable_new_stack(&st_default, dir, cfg_default);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_read_ref(st_default, "master", &dest);
+       EXPECT_ERR(err);
+
+       EXPECT(reftable_ref_record_equal(&ref, &dest, GIT_SHA1_RAWSZ));
+       reftable_ref_record_release(&dest);
+       reftable_stack_destroy(st);
+       reftable_stack_destroy(st_default);
+       clear_dir(dir);
+}
+
+static void test_log2(void)
+{
+       EXPECT(1 == fastlog2(3));
+       EXPECT(2 == fastlog2(4));
+       EXPECT(2 == fastlog2(5));
+}
+
+static void test_sizes_to_segments(void)
+{
+       uint64_t sizes[] = { 2, 3, 4, 5, 7, 9 };
+       /* .................0  1  2  3  4  5 */
+
+       int seglen = 0;
+       struct segment *segs =
+               sizes_to_segments(&seglen, sizes, ARRAY_SIZE(sizes));
+       EXPECT(segs[2].log == 3);
+       EXPECT(segs[2].start == 5);
+       EXPECT(segs[2].end == 6);
+
+       EXPECT(segs[1].log == 2);
+       EXPECT(segs[1].start == 2);
+       EXPECT(segs[1].end == 5);
+       reftable_free(segs);
+}
+
+static void test_sizes_to_segments_empty(void)
+{
+       int seglen = 0;
+       struct segment *segs = sizes_to_segments(&seglen, NULL, 0);
+       EXPECT(seglen == 0);
+       reftable_free(segs);
+}
+
+static void test_sizes_to_segments_all_equal(void)
+{
+       uint64_t sizes[] = { 5, 5 };
+
+       int seglen = 0;
+       struct segment *segs =
+               sizes_to_segments(&seglen, sizes, ARRAY_SIZE(sizes));
+       EXPECT(seglen == 1);
+       EXPECT(segs[0].start == 0);
+       EXPECT(segs[0].end == 2);
+       reftable_free(segs);
+}
+
+static void test_suggest_compaction_segment(void)
+{
+       uint64_t sizes[] = { 128, 64, 17, 16, 9, 9, 9, 16, 16 };
+       /* .................0    1    2  3   4  5  6 */
+       struct segment min =
+               suggest_compaction_segment(sizes, ARRAY_SIZE(sizes));
+       EXPECT(min.start == 2);
+       EXPECT(min.end == 7);
+}
+
+static void test_suggest_compaction_segment_nothing(void)
+{
+       uint64_t sizes[] = { 64, 32, 16, 8, 4, 2 };
+       struct segment result =
+               suggest_compaction_segment(sizes, ARRAY_SIZE(sizes));
+       EXPECT(result.start == result.end);
+}
+
+static void test_reflog_expire(void)
+{
+       char *dir = get_tmp_dir(__LINE__);
+
+       struct reftable_write_options cfg = { 0 };
+       struct reftable_stack *st = NULL;
+       struct reftable_log_record logs[20] = { { NULL } };
+       int N = ARRAY_SIZE(logs) - 1;
+       int i = 0;
+       int err;
+       struct reftable_log_expiry_config expiry = {
+               .time = 10,
+       };
+       struct reftable_log_record log = { NULL };
+
+
+       err = reftable_new_stack(&st, dir, cfg);
+       EXPECT_ERR(err);
+
+       for (i = 1; i <= N; i++) {
+               char buf[256];
+               snprintf(buf, sizeof(buf), "branch%02d", i);
+
+               logs[i].refname = xstrdup(buf);
+               logs[i].update_index = i;
+               logs[i].value_type = REFTABLE_LOG_UPDATE;
+               logs[i].value.update.time = i;
+               logs[i].value.update.new_hash = reftable_malloc(GIT_SHA1_RAWSZ);
+               logs[i].value.update.email = xstrdup("identity@invalid");
+               set_test_hash(logs[i].value.update.new_hash, i);
+       }
+
+       for (i = 1; i <= N; i++) {
+               struct write_log_arg arg = {
+                       .log = &logs[i],
+                       .update_index = reftable_stack_next_update_index(st),
+               };
+               int err = reftable_stack_add(st, &write_test_log, &arg);
+               EXPECT_ERR(err);
+       }
+
+       err = reftable_stack_compact_all(st, NULL);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_compact_all(st, &expiry);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_read_log(st, logs[9].refname, &log);
+       EXPECT(err == 1);
+
+       err = reftable_stack_read_log(st, logs[11].refname, &log);
+       EXPECT_ERR(err);
+
+       expiry.min_update_index = 15;
+       err = reftable_stack_compact_all(st, &expiry);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_read_log(st, logs[14].refname, &log);
+       EXPECT(err == 1);
+
+       err = reftable_stack_read_log(st, logs[16].refname, &log);
+       EXPECT_ERR(err);
+
+       /* cleanup */
+       reftable_stack_destroy(st);
+       for (i = 0; i <= N; i++) {
+               reftable_log_record_release(&logs[i]);
+       }
+       clear_dir(dir);
+       reftable_log_record_release(&log);
+}
+
+static int write_nothing(struct reftable_writer *wr, void *arg)
+{
+       reftable_writer_set_limits(wr, 1, 1);
+       return 0;
+}
+
+static void test_empty_add(void)
+{
+       struct reftable_write_options cfg = { 0 };
+       struct reftable_stack *st = NULL;
+       int err;
+       char *dir = get_tmp_dir(__LINE__);
+
+       struct reftable_stack *st2 = NULL;
+
+
+       err = reftable_new_stack(&st, dir, cfg);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_add(st, &write_nothing, NULL);
+       EXPECT_ERR(err);
+
+       err = reftable_new_stack(&st2, dir, cfg);
+       EXPECT_ERR(err);
+       clear_dir(dir);
+       reftable_stack_destroy(st);
+       reftable_stack_destroy(st2);
+}
+
+static void test_reftable_stack_auto_compaction(void)
+{
+       struct reftable_write_options cfg = { 0 };
+       struct reftable_stack *st = NULL;
+       char *dir = get_tmp_dir(__LINE__);
+
+       int err, i;
+       int N = 100;
+
+       err = reftable_new_stack(&st, dir, cfg);
+       EXPECT_ERR(err);
+
+       st->disable_auto_compact = 1; /* call manually below for coverage. */
+       for (i = 0; i < N; i++) {
+               char name[100];
+               struct reftable_ref_record ref = {
+                       .refname = name,
+                       .update_index = reftable_stack_next_update_index(st),
+                       .value_type = REFTABLE_REF_SYMREF,
+                       .value.symref = "master",
+               };
+               snprintf(name, sizeof(name), "branch%04d", i);
+
+               err = reftable_stack_add(st, &write_test_ref, &ref);
+               EXPECT_ERR(err);
+
+               err = reftable_stack_auto_compact(st);
+               EXPECT(i < 3 || st->merged->stack_len < 2 * fastlog2(i));
+       }
+
+       EXPECT(reftable_stack_compaction_stats(st)->entries_written <
+              (uint64_t)(N * fastlog2(N)));
+
+       reftable_stack_destroy(st);
+       clear_dir(dir);
+}
+
+static void test_reftable_stack_compaction_concurrent(void)
+{
+       struct reftable_write_options cfg = { 0 };
+       struct reftable_stack *st1 = NULL, *st2 = NULL;
+       char *dir = get_tmp_dir(__LINE__);
+
+       int err, i;
+       int N = 3;
+
+       err = reftable_new_stack(&st1, dir, cfg);
+       EXPECT_ERR(err);
+
+       for (i = 0; i < N; i++) {
+               char name[100];
+               struct reftable_ref_record ref = {
+                       .refname = name,
+                       .update_index = reftable_stack_next_update_index(st1),
+                       .value_type = REFTABLE_REF_SYMREF,
+                       .value.symref = "master",
+               };
+               snprintf(name, sizeof(name), "branch%04d", i);
+
+               err = reftable_stack_add(st1, &write_test_ref, &ref);
+               EXPECT_ERR(err);
+       }
+
+       err = reftable_new_stack(&st2, dir, cfg);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_compact_all(st1, NULL);
+       EXPECT_ERR(err);
+
+       reftable_stack_destroy(st1);
+       reftable_stack_destroy(st2);
+
+       EXPECT(count_dir_entries(dir) == 2);
+       clear_dir(dir);
+}
+
+static void unclean_stack_close(struct reftable_stack *st)
+{
+       /* break abstraction boundary to simulate unclean shutdown. */
+       int i = 0;
+       for (; i < st->readers_len; i++) {
+               reftable_reader_free(st->readers[i]);
+       }
+       st->readers_len = 0;
+       FREE_AND_NULL(st->readers);
+}
+
+static void test_reftable_stack_compaction_concurrent_clean(void)
+{
+       struct reftable_write_options cfg = { 0 };
+       struct reftable_stack *st1 = NULL, *st2 = NULL, *st3 = NULL;
+       char *dir = get_tmp_dir(__LINE__);
+
+       int err, i;
+       int N = 3;
+
+       err = reftable_new_stack(&st1, dir, cfg);
+       EXPECT_ERR(err);
+
+       for (i = 0; i < N; i++) {
+               char name[100];
+               struct reftable_ref_record ref = {
+                       .refname = name,
+                       .update_index = reftable_stack_next_update_index(st1),
+                       .value_type = REFTABLE_REF_SYMREF,
+                       .value.symref = "master",
+               };
+               snprintf(name, sizeof(name), "branch%04d", i);
+
+               err = reftable_stack_add(st1, &write_test_ref, &ref);
+               EXPECT_ERR(err);
+       }
+
+       err = reftable_new_stack(&st2, dir, cfg);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_compact_all(st1, NULL);
+       EXPECT_ERR(err);
+
+       unclean_stack_close(st1);
+       unclean_stack_close(st2);
+
+       err = reftable_new_stack(&st3, dir, cfg);
+       EXPECT_ERR(err);
+
+       err = reftable_stack_clean(st3);
+       EXPECT_ERR(err);
+       EXPECT(count_dir_entries(dir) == 2);
+
+       reftable_stack_destroy(st1);
+       reftable_stack_destroy(st2);
+       reftable_stack_destroy(st3);
+
+       clear_dir(dir);
+}
+
+int stack_test_main(int argc, const char *argv[])
+{
+       RUN_TEST(test_empty_add);
+       RUN_TEST(test_log2);
+       RUN_TEST(test_names_equal);
+       RUN_TEST(test_parse_names);
+       RUN_TEST(test_read_file);
+       RUN_TEST(test_reflog_expire);
+       RUN_TEST(test_reftable_stack_add);
+       RUN_TEST(test_reftable_stack_add_one);
+       RUN_TEST(test_reftable_stack_auto_compaction);
+       RUN_TEST(test_reftable_stack_compaction_concurrent);
+       RUN_TEST(test_reftable_stack_compaction_concurrent_clean);
+       RUN_TEST(test_reftable_stack_hash_id);
+       RUN_TEST(test_reftable_stack_lock_failure);
+       RUN_TEST(test_reftable_stack_log_normalize);
+       RUN_TEST(test_reftable_stack_tombstone);
+       RUN_TEST(test_reftable_stack_transaction_api);
+       RUN_TEST(test_reftable_stack_update_index_check);
+       RUN_TEST(test_reftable_stack_uptodate);
+       RUN_TEST(test_reftable_stack_validate_refname);
+       RUN_TEST(test_sizes_to_segments);
+       RUN_TEST(test_sizes_to_segments_all_equal);
+       RUN_TEST(test_sizes_to_segments_empty);
+       RUN_TEST(test_suggest_compaction_segment);
+       RUN_TEST(test_suggest_compaction_segment_nothing);
+       return 0;
+}
index c8db6852c353d09999f6612de9f22a09f4b700dd..996da85f7b5c3274402a41e6e787560ecfba6d36 100644 (file)
@@ -10,6 +10,7 @@ int cmd__reftable(int argc, const char **argv)
        record_test_main(argc, argv);
        refname_test_main(argc, argv);
        readwrite_test_main(argc, argv);
+       stack_test_main(argc, argv);
        tree_test_main(argc, argv);
        return 0;
 }