--- /dev/null
+/* Set operations for device-inode pairs stored in a space-efficient manner.
+
+ Copyright 2009-2010 Free Software Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+/* written by Jim Meyering */
+
+#include <config.h>
+#include "di-set.h"
+
+#include <stdio.h>
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "verify.h"
+
+/* Set operations for device-inode pairs stored in a space-efficient manner.
+ A naive mapping uses 16 bytes to save a single st_dev, st_ino pair.
+ However, in many applications, the vast majority of actual device,inode
+ number pairs can be efficiently compressed to fit in 8 or even 4 bytes,
+ by using a separate table to map a relatively small number of devices
+ to small integers. */
+
+#define N_DEV_BITS_4 5
+#define N_INO_BITS_4 (32 - N_DEV_BITS_4 - 2 - 1)
+
+#define N_DEV_BITS_8 8
+#define N_INO_BITS_8 (64 - N_DEV_BITS_8 - 2 - 1)
+
+/* Note how the last bit is always set.
+ This is required, in order to be able to distinguish
+ an encoded di_ent value from a malloc-returned pointer,
+ which must be 4-byte-aligned or better. */
+struct dev_ino_4
+{
+ uint32_t mode:2; /* must be first */
+ uint32_t short_ino:N_INO_BITS_4;
+ uint32_t mapped_dev:N_DEV_BITS_4;
+ uint32_t always_set:1;
+};
+verify (N_DEV_BITS_4 <= 8 * sizeof (int));
+verify (sizeof (struct dev_ino_4) == 4);
+
+struct dev_ino_8
+{
+ uint32_t mode:2; /* must be first */
+ uint64_t short_ino:N_INO_BITS_8;
+ uint32_t mapped_dev:N_DEV_BITS_8;
+ uint32_t always_set:1;
+};
+verify (sizeof (struct dev_ino_8) == 8);
+
+struct dev_ino_full
+{
+ uint32_t mode:2; /* must be first */
+ dev_t dev;
+ ino_t ino;
+};
+
+enum di_mode
+{
+ DI_MODE_4 = 1,
+ DI_MODE_8 = 2,
+ DI_MODE_FULL = 3
+};
+
+/*
+ di_mode raw_inode mapped dev always_set
+ \____________|_______________\_____/
+ 4-byte | 2| 25 | 5 |1| mapped_dev
+ `----------------------------------------------------|-----.
+ 8-byte | 2| 53 | 8 |1|
+ `----------------------------------------------------------'
+*/
+struct di_ent
+{
+ union
+ {
+ struct dev_ino_4 di4;
+ struct dev_ino_8 di8;
+ struct dev_ino_full full;
+ uint32_t u32;
+ uint64_t u64;
+ void *ptr;
+ } u;
+};
+
+struct dev_map_ent
+{
+ dev_t dev;
+ uint32_t mapped_dev;
+};
+
+static inline bool
+is_encoded_ptr (struct di_ent const *v)
+{
+ return (size_t) v % 4;
+}
+
+static struct di_ent
+decode_ptr (struct di_ent const *v)
+{
+ if (!is_encoded_ptr (v))
+ return *v;
+
+ struct di_ent di;
+ di.u.ptr = (void *) v;
+ return di;
+}
+
+static size_t
+di_ent_hash (void const *x, size_t table_size)
+{
+ struct di_ent e = decode_ptr (x);
+ return (e.u.di4.mode == DI_MODE_4
+ ? e.u.u32
+ : (e.u.di4.mode == DI_MODE_8
+ ? e.u.u64
+ : e.u.full.ino)) % table_size;
+}
+
+/* Compare two di_ent structs.
+ Return true if they are the same. */
+static bool
+di_ent_compare (void const *x, void const *y)
+{
+ struct di_ent a = decode_ptr (x);
+ struct di_ent b = decode_ptr (y);
+ if (a.u.di4.mode != b.u.di4.mode)
+ return false;
+
+ if (a.u.di4.mode == DI_MODE_4)
+ return (a.u.di4.short_ino == b.u.di4.short_ino
+ && a.u.di4.mapped_dev == b.u.di4.mapped_dev);
+
+ if (a.u.di8.mode == DI_MODE_8)
+ return (a.u.di8.short_ino == b.u.di8.short_ino
+ && a.u.di8.mapped_dev == b.u.di8.mapped_dev);
+
+ return (a.u.full.ino == b.u.full.ino
+ && a.u.full.dev == b.u.full.dev);
+}
+
+static void
+di_ent_free (void *v)
+{
+ if ( ! is_encoded_ptr (v))
+ free (v);
+}
+
+int
+di_set_init (struct di_set_state *dis, size_t initial_size)
+{
+ if (dev_map_init (&dis->dev_map) < 0)
+ return -1;
+
+ dis->di_set = hash_initialize (initial_size, NULL,
+ di_ent_hash, di_ent_compare, di_ent_free);
+ return dis->di_set ? 0 : -1;
+}
+
+void
+di_set_free (struct di_set_state *dis)
+{
+ dev_map_free (&dis->dev_map);
+ hash_free (dis->di_set);
+}
+
+/* Given a device-inode set, DIS, create an entry for the DEV,INO
+ pair, and store it in *V. If possible, encode DEV,INO into the pointer
+ itself, but if not, allocate space for a full "struct di_ent" and set *V
+ to that pointer. Upon memory allocation failure, return -1.
+ Otherwise return 0. */
+int
+di_ent_create (struct di_set_state *dis,
+ dev_t dev, ino_t ino,
+ struct di_ent **v)
+{
+ static int prev_m = -1;
+ static dev_t prev_dev = -1;
+ struct di_ent di_ent;
+ int mapped_dev;
+
+ if (dev == prev_dev)
+ mapped_dev = prev_m;
+ else
+ {
+ mapped_dev = dev_map_insert (&dis->dev_map, dev);
+ if (mapped_dev < 0)
+ return -1;
+ prev_dev = dev;
+ prev_m = mapped_dev;
+ }
+
+ if (mapped_dev < (1 << N_DEV_BITS_4)
+ && ino < (1 << N_INO_BITS_4))
+ {
+#if lint
+ /* When this struct is smaller than a pointer, initialize
+ the pointer so tools like valgrind don't complain about
+ the uninitialized bytes. */
+ if (sizeof di_ent.u.di4 < sizeof di_ent.u.ptr)
+ di_ent.u.ptr = NULL;
+#endif
+ di_ent.u.di4.mode = DI_MODE_4;
+ di_ent.u.di4.short_ino = ino;
+ di_ent.u.di4.mapped_dev = mapped_dev;
+ di_ent.u.di4.always_set = 1;
+ *v = di_ent.u.ptr;
+ }
+ else if (mapped_dev < (1 << N_DEV_BITS_8)
+ && ino < ((uint64_t) 1 << N_INO_BITS_8))
+ {
+ di_ent.u.di8.mode = DI_MODE_8;
+ di_ent.u.di8.short_ino = ino;
+ di_ent.u.di8.mapped_dev = mapped_dev;
+ di_ent.u.di8.always_set = 1;
+ *v = di_ent.u.ptr;
+ }
+ else
+ {
+ /* Handle the case in which INO is too large or in which (far less
+ likely) we encounter hard-linked files on 2^N_DEV_BITS_8
+ different devices. */
+ struct di_ent *p = malloc (sizeof *p);
+ if (!p)
+ return -1;
+ assert ((size_t) p % 4 == 0);
+ p->u.full.mode = DI_MODE_FULL;
+ p->u.full.ino = ino;
+ p->u.full.dev = dev;
+ *v = p;
+ }
+
+ return 0;
+}
+
+/* Attempt to insert the DEV,INO pair into the set, DIS.
+ If it matches a pair already in DIS, don't modify DIS and return 0.
+ Otherwise, if insertion is successful, return 1.
+ Upon any failure return -1. */
+int
+di_set_insert (struct di_set_state *dis, dev_t dev, ino_t ino)
+{
+ struct di_ent *v;
+ if (di_ent_create (dis, dev, ino, &v) < 0)
+ return -1;
+
+ int err = hash_insert0 (dis->di_set, v, NULL);
+ if (err == -1) /* Insertion failed due to lack of memory. */
+ return -1;
+
+ if (err == 1) /* Insertion succeeded. */
+ return 1;
+
+ /* That pair is already in the table, so ENT was not inserted. Free it. */
+ if (! is_encoded_ptr (v))
+ free (v);
+
+ return 0;
+}
--- /dev/null
+/* Test the dev-map module.
+ Copyright (C) 2010 Free Software Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+/* Written by Jim Meyering. */
+
+#include <config.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+#define ASSERT(expr) \
+ do \
+ { \
+ if (!(expr)) \
+ { \
+ fprintf (stderr, "%s:%d: assertion failed\n", __FILE__, __LINE__); \
+ fflush (stderr); \
+ abort (); \
+ } \
+ } \
+ while (0)
+
+#include "di-set.h"
+
+/* FIXME: ugly duplication of code from di-set.c */
+#define N_DEV_BITS_4 5
+#define N_INO_BITS_4 (32 - N_DEV_BITS_4 - 2 - 1)
+
+#define N_DEV_BITS_8 8
+#define N_INO_BITS_8 (64 - N_DEV_BITS_8 - 2 - 1)
+
+int
+main (void)
+{
+ /* set_program_name (argv[0]); placate overzealous "syntax-check" test. */
+ size_t initial_size = 61;
+ /* "real" code might prefer to avoid the allocation here, simply
+ declaring "struct di_set_state dis;", do a global substitution,
+ s/\<dis\>/\&dis/, and remove the final free. */
+ struct di_set_state *dis = malloc (sizeof *dis);
+ ASSERT (dis);
+ ASSERT (di_set_init (dis, initial_size) == 0);
+
+ struct di_ent *di_ent;
+ ASSERT (di_ent_create (dis, 1, 1, &di_ent) == 0);
+ ASSERT (di_ent_create (dis, 1 << N_DEV_BITS_4, 1, &di_ent) == 0);
+ ASSERT (di_ent_create (dis, 1, 1 << N_INO_BITS_4, &di_ent) == 0);
+ ASSERT (di_ent_create (dis, 1,
+ (uint64_t) 1 << N_INO_BITS_8, &di_ent) == 0);
+ free (di_ent);
+
+ ASSERT (di_set_insert (dis, 2, 5) == 1); /* first insertion succeeds */
+ ASSERT (di_set_insert (dis, 2, 5) == 0); /* duplicate fails */
+ ASSERT (di_set_insert (dis, 3, 5) == 1); /* diff dev, duplicate inode is ok */
+ ASSERT (di_set_insert (dis, 2, 8) == 1); /* same dev, different inode is ok */
+
+ /* very large inode number */
+ ASSERT (di_set_insert (dis, 5, (uint64_t) 1 << 63) == 1);
+ ASSERT (di_set_insert (dis, 5, (uint64_t) 1 << 63) == 0); /* dup */
+
+ unsigned int i;
+ for (i = 0; i < 3000; i++)
+ ASSERT (di_set_insert (dis, 9, i) == 1);
+ for (i = 0; i < 3000; i++)
+ ASSERT (di_set_insert (dis, 9, i) == 0); /* duplicate fails */
+
+ di_set_free (dis);
+ free (dis);
+
+ return 0;
+}
projects / thirdparty / coreutils.git / commitdiff
