introduce delta objects with offset to base

[thirdparty/git.git] / sha1_file.c

diff --git a/sha1_file.c b/sha1_file.c
index 27b1ebb720b1530d673f3dfb1c27862b4cf90dfd..fdb4588280634e3d87c02353db55bc808f57f16f 100644 (file)
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -883,26 +883,61 @@ void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned l
        return unpack_sha1_rest(&stream, hdr, *size);
 }
 
+static unsigned long get_delta_base(struct packed_git *p,
+                                   unsigned long offset,
+                                   enum object_type kind,
+                                   unsigned long delta_obj_offset,
+                                   unsigned long *base_obj_offset)
+{
+       unsigned char *base_info = (unsigned char *) p->pack_base + offset;
+       unsigned long base_offset;
+
+       /* there must be at least 20 bytes left regardless of delta type */
+       if (p->pack_size <= offset + 20)
+               die("truncated pack file");
+
+       if (kind == OBJ_OFS_DELTA) {
+               unsigned used = 0;
+               unsigned char c = base_info[used++];
+               base_offset = c & 127;
+               while (c & 128) {
+                       base_offset += 1;
+                       if (!base_offset || base_offset & ~(~0UL >> 7))
+                               die("offset value overflow for delta base object");
+                       c = base_info[used++];
+                       base_offset = (base_offset << 7) + (c & 127);
+               }
+               base_offset = delta_obj_offset - base_offset;
+               if (base_offset >= delta_obj_offset)
+                       die("delta base offset out of bound");
+               offset += used;
+       } else if (kind == OBJ_REF_DELTA) {
+               /* The base entry _must_ be in the same pack */
+               base_offset = find_pack_entry_one(base_info, p);
+               if (!base_offset)
+                       die("failed to find delta-pack base object %s",
+                               sha1_to_hex(base_info));
+               offset += 20;
+       } else
+               die("I am totally screwed");
+       *base_obj_offset = base_offset;
+       return offset;
+}
+
 /* forward declaration for a mutually recursive function */
 static int packed_object_info(struct packed_git *p, unsigned long offset,
                              char *type, unsigned long *sizep);
 
 static int packed_delta_info(struct packed_git *p,
                             unsigned long offset,
+                            enum object_type kind,
+                            unsigned long obj_offset,
                             char *type,
                             unsigned long *sizep)
 {
        unsigned long base_offset;
-       unsigned char *base_sha1 = (unsigned char *) p->pack_base + offset;
 
-       if (p->pack_size < offset + 20)
-               die("truncated pack file");
-       /* The base entry _must_ be in the same pack */
-       base_offset = find_pack_entry_one(base_sha1, p);
-       if (!base_offset)
-               die("failed to find delta-pack base object %s",
-                   sha1_to_hex(base_sha1));
-       offset += 20;
+       offset = get_delta_base(p, offset, kind, obj_offset, &base_offset);
 
        /* We choose to only get the type of the base object and
         * ignore potentially corrupt pack file that expects the delta
@@ -975,7 +1010,7 @@ int check_reuse_pack_delta(struct packed_git *p, unsigned long offset,
        use_packed_git(p);
        ptr = offset;
        ptr = unpack_object_header(p, ptr, kindp, sizep);
-       if (*kindp != OBJ_DELTA)
+       if (*kindp != OBJ_REF_DELTA)
                goto done;
        hashcpy(base, (unsigned char *) p->pack_base + ptr);
        status = 0;
@@ -992,11 +1027,12 @@ void packed_object_info_detail(struct packed_git *p,
                               unsigned int *delta_chain_length,
                               unsigned char *base_sha1)
 {
-       unsigned long val;
+       unsigned long obj_offset, val;
        unsigned char *next_sha1;
        enum object_type kind;
 
        *delta_chain_length = 0;
+       obj_offset = offset;
        offset = unpack_object_header(p, offset, &kind, size);
 
        for (;;) {
@@ -1011,7 +1047,13 @@ void packed_object_info_detail(struct packed_git *p,
                        strcpy(type, type_names[kind]);
                        *store_size = 0; /* notyet */
                        return;
-               case OBJ_DELTA:
+               case OBJ_OFS_DELTA:
+                       get_delta_base(p, offset, kind, obj_offset, &offset);
+                       if (*delta_chain_length == 0) {
+                               /* TODO: find base_sha1 as pointed by offset */
+                       }
+                       break;
+               case OBJ_REF_DELTA:
                        if (p->pack_size <= offset + 20)
                                die("pack file %s records an incomplete delta base",
                                    p->pack_name);
@@ -1021,6 +1063,7 @@ void packed_object_info_detail(struct packed_git *p,
                        offset = find_pack_entry_one(next_sha1, p);
                        break;
                }
+               obj_offset = offset;
                offset = unpack_object_header(p, offset, &kind, &val);
                (*delta_chain_length)++;
        }
@@ -1029,15 +1072,15 @@ void packed_object_info_detail(struct packed_git *p,
 static int packed_object_info(struct packed_git *p, unsigned long offset,
                              char *type, unsigned long *sizep)
 {
-       unsigned long size;
+       unsigned long size, obj_offset = offset;
        enum object_type kind;
 
        offset = unpack_object_header(p, offset, &kind, &size);
 
-       if (kind == OBJ_DELTA)
-               return packed_delta_info(p, offset, type, sizep);
-
        switch (kind) {
+       case OBJ_OFS_DELTA:
+       case OBJ_REF_DELTA:
+               return packed_delta_info(p, offset, kind, obj_offset, type, sizep);
        case OBJ_COMMIT:
        case OBJ_TREE:
        case OBJ_BLOB:
@@ -1083,23 +1126,15 @@ static void *unpack_compressed_entry(struct packed_git *p,
 static void *unpack_delta_entry(struct packed_git *p,
                                unsigned long offset,
                                unsigned long delta_size,
+                               enum object_type kind,
+                               unsigned long obj_offset,
                                char *type,
                                unsigned long *sizep)
 {
        void *delta_data, *result, *base;
        unsigned long result_size, base_size, base_offset;
-       unsigned char *base_sha1;
-
-       if (p->pack_size < offset + 20)
-               die("truncated pack file");
-       /* The base entry _must_ be in the same pack */
-       base_sha1 = (unsigned char*)p->pack_base + offset;
-       base_offset = find_pack_entry_one(base_sha1, p);
-       if (!base_offset)
-               die("failed to find delta-pack base object %s",
-                   sha1_to_hex(base_sha1));
-       offset += 20;
 
+       offset = get_delta_base(p, offset, kind, obj_offset, &base_offset);
        base = unpack_entry_gently(p, base_offset, type, &base_size);
        if (!base)
                die("failed to read delta base object at %lu from %s",
@@ -1136,13 +1171,14 @@ static void *unpack_entry(struct pack_entry *entry,
 void *unpack_entry_gently(struct packed_git *p, unsigned long offset,
                          char *type, unsigned long *sizep)
 {
-       unsigned long size;
+       unsigned long size, obj_offset = offset;
        enum object_type kind;
 
        offset = unpack_object_header(p, offset, &kind, &size);
        switch (kind) {
-       case OBJ_DELTA:
-               return unpack_delta_entry(p, offset, size, type, sizep);
+       case OBJ_OFS_DELTA:
+       case OBJ_REF_DELTA:
+               return unpack_delta_entry(p, offset, size, kind, obj_offset, type, sizep);
        case OBJ_COMMIT:
        case OBJ_TREE:
        case OBJ_BLOB: