[PATCH] write_sha1_to_fd()
[git/git.git] / sha1_file.c
index 66308ed..b13578b 100644 (file)
@@ -6,10 +6,11 @@
  * This handles basic git sha1 object files - packing, unpacking,
  * creation etc.
  */
-#include <stdarg.h>
+#include <sys/types.h>
+#include <dirent.h>
 #include "cache.h"
-
-const char *sha1_file_directory = NULL;
+#include "delta.h"
+#include "pack.h"
 
 #ifndef O_NOATIME
 #if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
@@ -45,6 +46,105 @@ int get_sha1_hex(const char *hex, unsigned char *sha1)
        return 0;
 }
 
+static int get_sha1_file(const char *path, unsigned char *result)
+{
+       char buffer[60];
+       int fd = open(path, O_RDONLY);
+       int len;
+
+       if (fd < 0)
+               return -1;
+       len = read(fd, buffer, sizeof(buffer));
+       close(fd);
+       if (len < 40)
+               return -1;
+       return get_sha1_hex(buffer, result);
+}
+
+static char *git_dir, *git_object_dir, *git_index_file, *git_refs_dir;
+static void setup_git_env(void)
+{
+       git_dir = gitenv(GIT_DIR_ENVIRONMENT);
+       if (!git_dir)
+               git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
+       git_object_dir = gitenv(DB_ENVIRONMENT);
+       if (!git_object_dir) {
+               git_object_dir = xmalloc(strlen(git_dir) + 9);
+               sprintf(git_object_dir, "%s/objects", git_dir);
+       }
+       git_refs_dir = xmalloc(strlen(git_dir) + 6);
+       sprintf(git_refs_dir, "%s/refs", git_dir);
+       git_index_file = gitenv(INDEX_ENVIRONMENT);
+       if (!git_index_file) {
+               git_index_file = xmalloc(strlen(git_dir) + 7);
+               sprintf(git_index_file, "%s/index", git_dir);
+       }
+}
+
+char *get_object_directory(void)
+{
+       if (!git_object_dir)
+               setup_git_env();
+       return git_object_dir;
+}
+
+char *get_refs_directory(void)
+{
+       if (!git_refs_dir)
+               setup_git_env();
+       return git_refs_dir;
+}
+
+char *get_index_file(void)
+{
+       if (!git_index_file)
+               setup_git_env();
+       return git_index_file;
+}
+
+int safe_create_leading_directories(char *path)
+{
+       char *pos = path;
+
+       while (pos) {
+               pos = strchr(pos, '/');
+               if (!pos)
+                       break;
+               *pos = 0;
+               if (mkdir(path, 0777) < 0)
+                       if (errno != EEXIST) {
+                               *pos = '/';
+                               return -1;
+                       }
+               *pos++ = '/';
+       }
+       return 0;
+}
+
+int get_sha1(const char *str, unsigned char *sha1)
+{
+       static const char *prefix[] = {
+               "",
+               "refs",
+               "refs/tags",
+               "refs/heads",
+               "refs/snap",
+               NULL
+       };
+       const char **p;
+
+       if (!get_sha1_hex(str, sha1))
+               return 0;
+
+       for (p = prefix; *p; p++) {
+               char * pathname = git_path("%s/%s", *p, str);
+               if (!get_sha1_file(pathname, sha1))
+                       return 0;
+       }
+
+       return -1;
+}
+
 char * sha1_to_hex(const unsigned char *sha1)
 {
        static char buffer[50];
@@ -60,37 +160,320 @@ char * sha1_to_hex(const unsigned char *sha1)
        return buffer;
 }
 
+static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
+{
+       int i;
+       for (i = 0; i < 20; i++) {
+               static char hex[] = "0123456789abcdef";
+               unsigned int val = sha1[i];
+               char *pos = pathbuf + i*2 + (i > 0);
+               *pos++ = hex[val >> 4];
+               *pos = hex[val & 0xf];
+       }
+}
+
 /*
  * NOTE! This returns a statically allocated buffer, so you have to be
  * careful about using it. Do a "strdup()" if you need to save the
  * filename.
+ *
+ * Also note that this returns the location for creating.  Reading
+ * SHA1 file can happen from any alternate directory listed in the
+ * DB_ENVIRONMENT environment variable if it is not found in
+ * the primary object database.
  */
 char *sha1_file_name(const unsigned char *sha1)
 {
-       int i;
        static char *name, *base;
 
        if (!base) {
-               char *sha1_file_directory = getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT;
+               const char *sha1_file_directory = get_object_directory();
                int len = strlen(sha1_file_directory);
-               base = malloc(len + 60);
+               base = xmalloc(len + 60);
                memcpy(base, sha1_file_directory, len);
                memset(base+len, 0, 60);
                base[len] = '/';
                base[len+3] = '/';
                name = base + len + 1;
        }
-       for (i = 0; i < 20; i++) {
-               static char hex[] = "0123456789abcdef";
-               unsigned int val = sha1[i];
-               char *pos = name + i*2 + (i > 0);
-               *pos++ = hex[val >> 4];
-               *pos = hex[val & 0xf];
-       }
+       fill_sha1_path(name, sha1);
        return base;
 }
 
-int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size, const char *type)
+struct alternate_object_database *alt_odb;
+
+/*
+ * Prepare alternate object database registry.
+ * alt_odb points at an array of struct alternate_object_database.
+ * This array is terminated with an element that has both its base
+ * and name set to NULL.  alt_odb[n] comes from n'th non-empty
+ * element from colon separated ALTERNATE_DB_ENVIRONMENT environment
+ * variable, and its base points at a statically allocated buffer
+ * that contains "/the/directory/corresponding/to/.git/objects/...",
+ * while its name points just after the slash at the end of
+ * ".git/objects/" in the example above, and has enough space to hold
+ * 40-byte hex SHA1, an extra slash for the first level indirection,
+ * and the terminating NUL.
+ * This function allocates the alt_odb array and all the strings
+ * pointed by base fields of the array elements with one xmalloc();
+ * the string pool immediately follows the array.
+ */
+void prepare_alt_odb(void)
+{
+       int pass, totlen, i;
+       const char *cp, *last;
+       char *op = NULL;
+       const char *alt = gitenv(ALTERNATE_DB_ENVIRONMENT) ? : "";
+
+       if (alt_odb)
+               return;
+       /* The first pass counts how large an area to allocate to
+        * hold the entire alt_odb structure, including array of
+        * structs and path buffers for them.  The second pass fills
+        * the structure and prepares the path buffers for use by
+        * fill_sha1_path().
+        */
+       for (totlen = pass = 0; pass < 2; pass++) {
+               last = alt;
+               i = 0;
+               do {
+                       cp = strchr(last, ':') ? : last + strlen(last);
+                       if (last != cp) {
+                               /* 43 = 40-byte + 2 '/' + terminating NUL */
+                               int pfxlen = cp - last;
+                               int entlen = pfxlen + 43;
+                               if (pass == 0)
+                                       totlen += entlen;
+                               else {
+                                       alt_odb[i].base = op;
+                                       alt_odb[i].name = op + pfxlen + 1;
+                                       memcpy(op, last, pfxlen);
+                                       op[pfxlen] = op[pfxlen + 3] = '/';
+                                       op[entlen-1] = 0;
+                                       op += entlen;
+                               }
+                               i++;
+                       }
+                       while (*cp && *cp == ':')
+                               cp++;
+                       last = cp;
+               } while (*cp);
+               if (pass)
+                       break;
+               alt_odb = xmalloc(sizeof(*alt_odb) * (i + 1) + totlen);
+               alt_odb[i].base = alt_odb[i].name = NULL;
+               op = (char*)(&alt_odb[i+1]);
+       }
+}
+
+static char *find_sha1_file(const unsigned char *sha1, struct stat *st)
+{
+       int i;
+       char *name = sha1_file_name(sha1);
+
+       if (!stat(name, st))
+               return name;
+       prepare_alt_odb();
+       for (i = 0; (name = alt_odb[i].name) != NULL; i++) {
+               fill_sha1_path(name, sha1);
+               if (!stat(alt_odb[i].base, st))
+                       return alt_odb[i].base;
+       }
+       return NULL;
+}
+
+#define PACK_MAX_SZ (1<<26)
+static int pack_used_ctr;
+static unsigned long pack_mapped;
+struct packed_git *packed_git;
+
+static int check_packed_git_idx(const char *path, unsigned long *idx_size_,
+                               void **idx_map_)
+{
+       void *idx_map;
+       unsigned int *index;
+       unsigned long idx_size;
+       int nr, i;
+       int fd = open(path, O_RDONLY);
+       struct stat st;
+       if (fd < 0)
+               return -1;
+       if (fstat(fd, &st)) {
+               close(fd);
+               return -1;
+       }
+       idx_size = st.st_size;
+       idx_map = mmap(NULL, idx_size, PROT_READ, MAP_PRIVATE, fd, 0);
+       close(fd);
+       if (idx_map == MAP_FAILED)
+               return -1;
+
+       index = idx_map;
+       *idx_map_ = idx_map;
+       *idx_size_ = idx_size;
+
+       /* check index map */
+       if (idx_size < 4*256 + 20 + 20)
+               return error("index file too small");
+       nr = 0;
+       for (i = 0; i < 256; i++) {
+               unsigned int n = ntohl(index[i]);
+               if (n < nr)
+                       return error("non-monotonic index");
+               nr = n;
+       }
+
+       /*
+        * Total size:
+        *  - 256 index entries 4 bytes each
+        *  - 24-byte entries * nr (20-byte sha1 + 4-byte offset)
+        *  - 20-byte SHA1 of the packfile
+        *  - 20-byte SHA1 file checksum
+        */
+       if (idx_size != 4*256 + nr * 24 + 20 + 20)
+               return error("wrong index file size");
+
+       return 0;
+}
+
+static int unuse_one_packed_git(void)
+{
+       struct packed_git *p, *lru = NULL;
+
+       for (p = packed_git; p; p = p->next) {
+               if (p->pack_use_cnt || !p->pack_base)
+                       continue;
+               if (!lru || p->pack_last_used < lru->pack_last_used)
+                       lru = p;
+       }
+       if (!lru)
+               return 0;
+       munmap(lru->pack_base, lru->pack_size);
+       lru->pack_base = NULL;
+       return 1;
+}
+
+void unuse_packed_git(struct packed_git *p)
+{
+       p->pack_use_cnt--;
+}
+
+int use_packed_git(struct packed_git *p)
+{
+       if (!p->pack_base) {
+               int fd;
+               struct stat st;
+               void *map;
+
+               pack_mapped += p->pack_size;
+               while (PACK_MAX_SZ < pack_mapped && unuse_one_packed_git())
+                       ; /* nothing */
+               fd = open(p->pack_name, O_RDONLY);
+               if (fd < 0)
+                       die("packfile %s cannot be opened", p->pack_name);
+               if (fstat(fd, &st)) {
+                       close(fd);
+                       die("packfile %s cannot be opened", p->pack_name);
+               }
+               if (st.st_size != p->pack_size)
+                       die("packfile %s size mismatch.", p->pack_name);
+               map = mmap(NULL, p->pack_size, PROT_READ, MAP_PRIVATE, fd, 0);
+               close(fd);
+               if (map == MAP_FAILED)
+                       die("packfile %s cannot be mapped.", p->pack_name);
+               p->pack_base = map;
+
+               /* Check if the pack file matches with the index file.
+                * this is cheap.
+                */
+               if (memcmp((char*)(p->index_base) + p->index_size - 40,
+                          p->pack_base + p->pack_size - 20, 20))
+                       die("packfile %s does not match index.", p->pack_name);
+       }
+       p->pack_last_used = pack_used_ctr++;
+       p->pack_use_cnt++;
+       return 0;
+}
+
+struct packed_git *add_packed_git(char *path, int path_len)
+{
+       struct stat st;
+       struct packed_git *p;
+       unsigned long idx_size;
+       void *idx_map;
+
+       if (check_packed_git_idx(path, &idx_size, &idx_map))
+               return NULL;
+
+       /* do we have a corresponding .pack file? */
+       strcpy(path + path_len - 4, ".pack");
+       if (stat(path, &st) || !S_ISREG(st.st_mode)) {
+               munmap(idx_map, idx_size);
+               return NULL;
+       }
+       /* ok, it looks sane as far as we can check without
+        * actually mapping the pack file.
+        */
+       p = xmalloc(sizeof(*p) + path_len + 2);
+       strcpy(p->pack_name, path);
+       p->index_size = idx_size;
+       p->pack_size = st.st_size;
+       p->index_base = idx_map;
+       p->next = NULL;
+       p->pack_base = NULL;
+       p->pack_last_used = 0;
+       p->pack_use_cnt = 0;
+       return p;
+}
+
+static void prepare_packed_git_one(char *objdir)
+{
+       char path[PATH_MAX];
+       int len;
+       DIR *dir;
+       struct dirent *de;
+
+       sprintf(path, "%s/pack", objdir);
+       len = strlen(path);
+       dir = opendir(path);
+       if (!dir)
+               return;
+       path[len++] = '/';
+       while ((de = readdir(dir)) != NULL) {
+               int namelen = strlen(de->d_name);
+               struct packed_git *p;
+
+               if (strcmp(de->d_name + namelen - 4, ".idx"))
+                       continue;
+
+               /* we have .idx.  Is it a file we can map? */
+               strcpy(path + len, de->d_name);
+               p = add_packed_git(path, len + namelen);
+               if (!p)
+                       continue;
+               p->next = packed_git;
+               packed_git = p;
+       }
+       closedir(dir);
+}
+
+void prepare_packed_git(void)
+{
+       int i;
+       static int run_once = 0;
+
+       if (run_once++)
+               return;
+
+       prepare_packed_git_one(get_object_directory());
+       prepare_alt_odb();
+       for (i = 0; alt_odb[i].base != NULL; i++) {
+               alt_odb[i].name[0] = 0;
+               prepare_packed_git_one(alt_odb[i].base);
+       }
+}
+
+int check_sha1_signature(const unsigned char *sha1, void *map, unsigned long size, const char *type)
 {
        char header[100];
        unsigned char real_sha1[20];
@@ -103,12 +486,20 @@ int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size, con
        return memcmp(sha1, real_sha1, 20) ? -1 : 0;
 }
 
-void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
+static void *map_sha1_file_internal(const unsigned char *sha1,
+                                   unsigned long *size,
+                                   int say_error)
 {
-       char *filename = sha1_file_name(sha1);
        struct stat st;
        void *map;
        int fd;
+       char *filename = find_sha1_file(sha1, &st);
+
+       if (!filename) {
+               if (say_error)
+                       error("cannot map sha1 file %s", sha1_to_hex(sha1));
+               return NULL;
+       }
 
        fd = open(filename, O_RDONLY | sha1_file_open_flag);
        if (fd < 0) {
@@ -120,17 +511,16 @@ void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
                                break;
                /* Fallthrough */
                case 0:
-                       perror(filename);
+                       if (say_error)
+                               perror(filename);
                        return NULL;
                }
 
-               /* If it failed once, it will probably fail again. Stop using O_NOATIME */
+               /* If it failed once, it will probably fail again.
+                * Stop using O_NOATIME
+                */
                sha1_file_open_flag = 0;
        }
-       if (fstat(fd, &st) < 0) {
-               close(fd);
-               return NULL;
-       }
        map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
        close(fd);
        if (-1 == (int)(long)map)
@@ -139,40 +529,516 @@ void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
        return map;
 }
 
+void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
+{
+       return map_sha1_file_internal(sha1, size, 1);
+}
+
+int unpack_sha1_header(z_stream *stream, void *map, unsigned long mapsize, void *buffer, unsigned long size)
+{
+       /* Get the data stream */
+       memset(stream, 0, sizeof(*stream));
+       stream->next_in = map;
+       stream->avail_in = mapsize;
+       stream->next_out = buffer;
+       stream->avail_out = size;
+
+       inflateInit(stream);
+       return inflate(stream, 0);
+}
+
+static void *unpack_sha1_rest(z_stream *stream, void *buffer, unsigned long size)
+{
+       int bytes = strlen(buffer) + 1;
+       unsigned char *buf = xmalloc(1+size);
+
+       memcpy(buf, buffer + bytes, stream->total_out - bytes);
+       bytes = stream->total_out - bytes;
+       if (bytes < size) {
+               stream->next_out = buf + bytes;
+               stream->avail_out = size - bytes;
+               while (inflate(stream, Z_FINISH) == Z_OK)
+                       /* nothing */;
+       }
+       buf[size] = 0;
+       inflateEnd(stream);
+       return buf;
+}
+
+/*
+ * We used to just use "sscanf()", but that's actually way
+ * too permissive for what we want to check. So do an anal
+ * object header parse by hand.
+ */
+int parse_sha1_header(char *hdr, char *type, unsigned long *sizep)
+{
+       int i;
+       unsigned long size;
+
+       /*
+        * The type can be at most ten bytes (including the 
+        * terminating '\0' that we add), and is followed by
+        * a space. 
+        */
+       i = 10;
+       for (;;) {
+               char c = *hdr++;
+               if (c == ' ')
+                       break;
+               if (!--i)
+                       return -1;
+               *type++ = c;
+       }
+       *type = 0;
+
+       /*
+        * The length must follow immediately, and be in canonical
+        * decimal format (ie "010" is not valid).
+        */
+       size = *hdr++ - '0';
+       if (size > 9)
+               return -1;
+       if (size) {
+               for (;;) {
+                       unsigned long c = *hdr - '0';
+                       if (c > 9)
+                               break;
+                       hdr++;
+                       size = size * 10 + c;
+               }
+       }
+       *sizep = size;
+
+       /*
+        * The length must be followed by a zero byte
+        */
+       return *hdr ? -1 : 0;
+}
+
 void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
 {
-       int ret, bytes;
+       int ret;
        z_stream stream;
-       char buffer[8192];
-       char *buf;
+       char hdr[8192];
+
+       ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
+       if (ret < Z_OK || parse_sha1_header(hdr, type, size) < 0)
+               return NULL;
+
+       return unpack_sha1_rest(&stream, hdr, *size);
+}
+
+/* forward declaration for a mutually recursive function */
+static int packed_object_info(struct pack_entry *entry,
+                             char *type, unsigned long *sizep);
+
+static int packed_delta_info(unsigned char *base_sha1,
+                            unsigned long delta_size,
+                            unsigned long left,
+                            char *type,
+                            unsigned long *sizep,
+                            struct packed_git *p)
+{
+       struct pack_entry base_ent;
+
+       if (left < 20)
+               die("truncated pack file");
+
+       /* The base entry _must_ be in the same pack */
+       if (!find_pack_entry_one(base_sha1, &base_ent, p))
+               die("failed to find delta-pack base object %s",
+                   sha1_to_hex(base_sha1));
+
+       /* We choose to only get the type of the base object and
+        * ignore potentially corrupt pack file that expects the delta
+        * based on a base with a wrong size.  This saves tons of
+        * inflate() calls.
+        */
+
+       if (packed_object_info(&base_ent, type, NULL))
+               die("cannot get info for delta-pack base");
+
+       if (sizep) {
+               const unsigned char *data;
+               unsigned char delta_head[64];
+               unsigned long result_size;
+               z_stream stream;
+               int st;
+
+               memset(&stream, 0, sizeof(stream));
+
+               data = stream.next_in = base_sha1 + 20;
+               stream.avail_in = left - 20;
+               stream.next_out = delta_head;
+               stream.avail_out = sizeof(delta_head);
+
+               inflateInit(&stream);
+               st = inflate(&stream, Z_FINISH);
+               inflateEnd(&stream);
+               if ((st != Z_STREAM_END) &&
+                   stream.total_out != sizeof(delta_head))
+                       die("delta data unpack-initial failed");
+
+               /* Examine the initial part of the delta to figure out
+                * the result size.
+                */
+               data = delta_head;
+               get_delta_hdr_size(&data); /* ignore base size */
+
+               /* Read the result size */
+               result_size = get_delta_hdr_size(&data);
+               *sizep = result_size;
+       }
+       return 0;
+}
+
+static unsigned long unpack_object_header(struct packed_git *p, unsigned long offset,
+       enum object_type *type, unsigned long *sizep)
+{
+       unsigned shift;
+       unsigned char *pack, c;
+       unsigned long size;
+
+       if (offset >= p->pack_size)
+               die("object offset outside of pack file");
+
+       pack =  p->pack_base + offset;
+       c = *pack++;
+       offset++;
+       *type = (c >> 4) & 7;
+       size = c & 15;
+       shift = 4;
+       while (c & 0x80) {
+               if (offset >= p->pack_size)
+                       die("object offset outside of pack file");
+               c = *pack++;
+               offset++;
+               size += (c & 0x7f) << shift;
+               shift += 7;
+       }
+       *sizep = size;
+       return offset;
+}
+
+void packed_object_info_detail(struct pack_entry *e,
+                              char *type,
+                              unsigned long *size,
+                              unsigned long *store_size,
+                              int *delta_chain_length,
+                              unsigned char *base_sha1)
+{
+       struct packed_git *p = e->p;
+       unsigned long offset, left;
+       unsigned char *pack;
+       enum object_type kind;
+
+       offset = unpack_object_header(p, e->offset, &kind, size);
+       pack = p->pack_base + offset;
+       left = p->pack_size - offset;
+       if (kind != OBJ_DELTA)
+               *delta_chain_length = 0;
+       else {
+               int chain_length = 0;
+               memcpy(base_sha1, pack, 20);
+               do {
+                       struct pack_entry base_ent;
+                       unsigned long junk;
+
+                       find_pack_entry_one(pack, &base_ent, p);
+                       offset = unpack_object_header(p, base_ent.offset,
+                                                     &kind, &junk);
+                       pack = p->pack_base + offset;
+                       chain_length++;
+               } while (kind == OBJ_DELTA);
+               *delta_chain_length = chain_length;
+       }
+       switch (kind) {
+       case OBJ_COMMIT:
+               strcpy(type, "commit");
+               break;
+       case OBJ_TREE:
+               strcpy(type, "tree");
+               break;
+       case OBJ_BLOB:
+               strcpy(type, "blob");
+               break;
+       case OBJ_TAG:
+               strcpy(type, "tag");
+               break;
+       default:
+               die("corrupted pack file");
+       }
+       *store_size = 0; /* notyet */
+}
+
+static int packed_object_info(struct pack_entry *entry,
+                             char *type, unsigned long *sizep)
+{
+       struct packed_git *p = entry->p;
+       unsigned long offset, size, left;
+       unsigned char *pack;
+       enum object_type kind;
+       int retval;
+
+       if (use_packed_git(p))
+               die("cannot map packed file");
+
+       offset = unpack_object_header(p, entry->offset, &kind, &size);
+       pack = p->pack_base + offset;
+       left = p->pack_size - offset;
+
+       switch (kind) {
+       case OBJ_DELTA:
+               retval = packed_delta_info(pack, size, left, type, sizep, p);
+               unuse_packed_git(p);
+               return retval;
+       case OBJ_COMMIT:
+               strcpy(type, "commit");
+               break;
+       case OBJ_TREE:
+               strcpy(type, "tree");
+               break;
+       case OBJ_BLOB:
+               strcpy(type, "blob");
+               break;
+       case OBJ_TAG:
+               strcpy(type, "tag");
+               break;
+       default:
+               die("corrupted pack file");
+       }
+       if (sizep)
+               *sizep = size;
+       unuse_packed_git(p);
+       return 0;
+}
+
+/* forward declaration for a mutually recursive function */
+static void *unpack_entry(struct pack_entry *, char *, unsigned long *);
+
+static void *unpack_delta_entry(unsigned char *base_sha1,
+                               unsigned long delta_size,
+                               unsigned long left,
+                               char *type,
+                               unsigned long *sizep,
+                               struct packed_git *p)
+{
+       struct pack_entry base_ent;
+       void *data, *delta_data, *result, *base;
+       unsigned long data_size, result_size, base_size;
+       z_stream stream;
+       int st;
+
+       if (left < 20)
+               die("truncated pack file");
+       data = base_sha1 + 20;
+       data_size = left - 20;
+       delta_data = xmalloc(delta_size);
 
-       /* Get the data stream */
        memset(&stream, 0, sizeof(stream));
-       stream.next_in = map;
-       stream.avail_in = mapsize;
+
+       stream.next_in = data;
+       stream.avail_in = data_size;
+       stream.next_out = delta_data;
+       stream.avail_out = delta_size;
+
+       inflateInit(&stream);
+       st = inflate(&stream, Z_FINISH);
+       inflateEnd(&stream);
+       if ((st != Z_STREAM_END) || stream.total_out != delta_size)
+               die("delta data unpack failed");
+
+       /* The base entry _must_ be in the same pack */
+       if (!find_pack_entry_one(base_sha1, &base_ent, p))
+               die("failed to find delta-pack base object %s",
+                   sha1_to_hex(base_sha1));
+       base = unpack_entry_gently(&base_ent, type, &base_size);
+       if (!base)
+               die("failed to read delta-pack base object %s",
+                   sha1_to_hex(base_sha1));
+       result = patch_delta(base, base_size,
+                            delta_data, delta_size,
+                            &result_size);
+       if (!result)
+               die("failed to apply delta");
+       free(delta_data);
+       free(base);
+       *sizep = result_size;
+       return result;
+}
+
+static void *unpack_non_delta_entry(unsigned char *data,
+                                   unsigned long size,
+                                   unsigned long left)
+{
+       int st;
+       z_stream stream;
+       unsigned char *buffer;
+
+       buffer = xmalloc(size + 1);
+       buffer[size] = 0;
+       memset(&stream, 0, sizeof(stream));
+       stream.next_in = data;
+       stream.avail_in = left;
        stream.next_out = buffer;
-       stream.avail_out = sizeof(buffer);
+       stream.avail_out = size;
 
        inflateInit(&stream);
-       ret = inflate(&stream, 0);
-       if (sscanf(buffer, "%10s %lu", type, size) != 2)
+       st = inflate(&stream, Z_FINISH);
+       inflateEnd(&stream);
+       if ((st != Z_STREAM_END) || stream.total_out != size) {
+               free(buffer);
                return NULL;
+       }
+
+       return buffer;
+}
+
+static void *unpack_entry(struct pack_entry *entry,
+                         char *type, unsigned long *sizep)
+{
+       struct packed_git *p = entry->p;
+       void *retval;
 
-       bytes = strlen(buffer) + 1;
-       buf = malloc(*size);
-       if (!buf)
+       if (use_packed_git(p))
+               die("cannot map packed file");
+       retval = unpack_entry_gently(entry, type, sizep);
+       unuse_packed_git(p);
+       if (!retval)
+               die("corrupted pack file");
+       return retval;
+}
+
+/* The caller is responsible for use_packed_git()/unuse_packed_git() pair */
+void *unpack_entry_gently(struct pack_entry *entry,
+                         char *type, unsigned long *sizep)
+{
+       struct packed_git *p = entry->p;
+       unsigned long offset, size, left;
+       unsigned char *pack;
+       enum object_type kind;
+       void *retval;
+
+       offset = unpack_object_header(p, entry->offset, &kind, &size);
+       pack = p->pack_base + offset;
+       left = p->pack_size - offset;
+       switch (kind) {
+       case OBJ_DELTA:
+               retval = unpack_delta_entry(pack, size, left, type, sizep, p);
+               return retval;
+       case OBJ_COMMIT:
+               strcpy(type, "commit");
+               break;
+       case OBJ_TREE:
+               strcpy(type, "tree");
+               break;
+       case OBJ_BLOB:
+               strcpy(type, "blob");
+               break;
+       case OBJ_TAG:
+               strcpy(type, "tag");
+               break;
+       default:
                return NULL;
+       }
+       *sizep = size;
+       retval = unpack_non_delta_entry(pack, size, left);
+       return retval;
+}
 
-       memcpy(buf, buffer + bytes, stream.total_out - bytes);
-       bytes = stream.total_out - bytes;
-       if (bytes < *size && ret == Z_OK) {
-               stream.next_out = buf + bytes;
-               stream.avail_out = *size - bytes;
-               while (inflate(&stream, Z_FINISH) == Z_OK)
-                       /* nothing */;
+int num_packed_objects(const struct packed_git *p)
+{
+       /* See check_packed_git_idx() */
+       return (p->index_size - 20 - 20 - 4*256) / 24;
+}
+
+int nth_packed_object_sha1(const struct packed_git *p, int n,
+                          unsigned char* sha1)
+{
+       void *index = p->index_base + 256;
+       if (n < 0 || num_packed_objects(p) <= n)
+               return -1;
+       memcpy(sha1, (index + 24 * n + 4), 20);
+       return 0;
+}
+
+int find_pack_entry_one(const unsigned char *sha1,
+                       struct pack_entry *e, struct packed_git *p)
+{
+       unsigned int *level1_ofs = p->index_base;
+       int hi = ntohl(level1_ofs[*sha1]);
+       int lo = ((*sha1 == 0x0) ? 0 : ntohl(level1_ofs[*sha1 - 1]));
+       void *index = p->index_base + 256;
+
+       do {
+               int mi = (lo + hi) / 2;
+               int cmp = memcmp(index + 24 * mi + 4, sha1, 20);
+               if (!cmp) {
+                       e->offset = ntohl(*((int*)(index + 24 * mi)));
+                       memcpy(e->sha1, sha1, 20);
+                       e->p = p;
+                       return 1;
+               }
+               if (cmp > 0)
+                       hi = mi;
+               else
+                       lo = mi+1;
+       } while (lo < hi);
+       return 0;
+}
+
+static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e)
+{
+       struct packed_git *p;
+       prepare_packed_git();
+
+       for (p = packed_git; p; p = p->next) {
+               if (find_pack_entry_one(sha1, e, p))
+                       return 1;
+       }
+       return 0;
+}
+
+int sha1_object_info(const unsigned char *sha1, char *type, unsigned long *sizep)
+{
+       int status;
+       unsigned long mapsize, size;
+       void *map;
+       z_stream stream;
+       char hdr[128];
+
+       map = map_sha1_file_internal(sha1, &mapsize, 0);
+       if (!map) {
+               struct pack_entry e;
+
+               if (!find_pack_entry(sha1, &e))
+                       return error("unable to find %s", sha1_to_hex(sha1));
+               return packed_object_info(&e, type, sizep);
+       }
+       if (unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr)) < 0)
+               status = error("unable to unpack %s header",
+                              sha1_to_hex(sha1));
+       if (parse_sha1_header(hdr, type, &size) < 0)
+               status = error("unable to parse %s header", sha1_to_hex(sha1));
+       else {
+               status = 0;
+               if (sizep)
+                       *sizep = size;
        }
        inflateEnd(&stream);
-       return buf;
+       munmap(map, mapsize);
+       return status;
+}
+
+static void *read_packed_sha1(const unsigned char *sha1, char *type, unsigned long *size)
+{
+       struct pack_entry e;
+
+       if (!find_pack_entry(sha1, &e)) {
+               error("cannot read sha1_file for %s", sha1_to_hex(sha1));
+               return NULL;
+       }
+       return unpack_entry(&e, type, size);
 }
 
 void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
@@ -180,97 +1046,142 @@ void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size
        unsigned long mapsize;
        void *map, *buf;
 
-       map = map_sha1_file(sha1, &mapsize);
+       map = map_sha1_file_internal(sha1, &mapsize, 0);
        if (map) {
                buf = unpack_sha1_file(map, mapsize, type, size);
                munmap(map, mapsize);
                return buf;
        }
-       return NULL;
+       return read_packed_sha1(sha1, type, size);
 }
 
-void *read_tree_with_tree_or_commit_sha1(const unsigned char *sha1,
-                                        unsigned long *size,
-                                        unsigned char *tree_sha1_return)
+void *read_object_with_reference(const unsigned char *sha1,
+                                const char *required_type,
+                                unsigned long *size,
+                                unsigned char *actual_sha1_return)
 {
        char type[20];
        void *buffer;
        unsigned long isize;
-       int was_commit = 0;
-       unsigned char tree_sha1[20];
+       unsigned char actual_sha1[20];
 
-       buffer = read_sha1_file(sha1, type, &isize);
+       memcpy(actual_sha1, sha1, 20);
+       while (1) {
+               int ref_length = -1;
+               const char *ref_type = NULL;
 
-       /* 
-        * We might have read a commit instead of a tree, in which case
-        * we parse out the tree_sha1 and attempt to read from there.
-        * (buffer + 5) is because the tree sha1 is always at offset 5
-        * in a commit record ("tree ").
-        */
-       if (buffer &&
-           !strcmp(type, "commit") &&
-           !get_sha1_hex(buffer + 5, tree_sha1)) {
-               free(buffer);
-               buffer = read_sha1_file(tree_sha1, type, &isize);
-               was_commit = 1;
-       }
+               buffer = read_sha1_file(actual_sha1, type, &isize);
+               if (!buffer)
+                       return NULL;
+               if (!strcmp(type, required_type)) {
+                       *size = isize;
+                       if (actual_sha1_return)
+                               memcpy(actual_sha1_return, actual_sha1, 20);
+                       return buffer;
+               }
+               /* Handle references */
+               else if (!strcmp(type, "commit"))
+                       ref_type = "tree ";
+               else if (!strcmp(type, "tag"))
+                       ref_type = "object ";
+               else {
+                       free(buffer);
+                       return NULL;
+               }
+               ref_length = strlen(ref_type);
 
-       /*
-        * Now do we have something and if so is it a tree?
-        */
-       if (!buffer || strcmp(type, "tree")) {
-               free(buffer);
-               return NULL;
+               if (memcmp(buffer, ref_type, ref_length) ||
+                   get_sha1_hex(buffer + ref_length, actual_sha1)) {
+                       free(buffer);
+                       return NULL;
+               }
+               /* Now we have the ID of the referred-to object in
+                * actual_sha1.  Check again. */
        }
-
-       *size = isize;
-       if (tree_sha1_return)
-               memcpy(tree_sha1_return, was_commit ? tree_sha1 : sha1, 20);
-       return buffer;
 }
 
-int write_sha1_file(char *buf, unsigned len, unsigned char *returnsha1)
+char *write_sha1_file_prepare(void *buf,
+                             unsigned long len,
+                             const char *type,
+                             unsigned char *sha1,
+                             unsigned char *hdr,
+                             int *hdrlen)
 {
-       int size;
-       char *compressed;
-       z_stream stream;
-       unsigned char sha1[20];
        SHA_CTX c;
-       char *filename;
-       int fd;
+
+       /* Generate the header */
+       *hdrlen = sprintf((char *)hdr, "%s %lu", type, len)+1;
 
        /* Sha1.. */
        SHA1_Init(&c);
+       SHA1_Update(&c, hdr, *hdrlen);
        SHA1_Update(&c, buf, len);
        SHA1_Final(sha1, &c);
 
-       if (returnsha1)
-               memcpy(returnsha1, sha1, 20);
+       return sha1_file_name(sha1);
+}
 
-       filename = sha1_file_name(sha1);
-       fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
-       if (fd < 0) {
-               if (errno != EEXIST)
-                       return -1;
+int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *returnsha1)
+{
+       int size;
+       unsigned char *compressed;
+       z_stream stream;
+       unsigned char sha1[20];
+       char *filename;
+       static char tmpfile[PATH_MAX];
+       unsigned char hdr[50];
+       int fd, hdrlen, ret;
 
+       /* Normally if we have it in the pack then we do not bother writing
+        * it out into .git/objects/??/?{38} file.
+        */
+       filename = write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen);
+       if (returnsha1)
+               memcpy(returnsha1, sha1, 20);
+       if (has_sha1_file(sha1))
+               return 0;
+       fd = open(filename, O_RDONLY);
+       if (fd >= 0) {
                /*
-                * We might do collision checking here, but we'd need to
-                * uncompress the old file and check it. Later.
+                * FIXME!!! We might do collision checking here, but we'd
+                * need to uncompress the old file and check it. Later.
                 */
+               close(fd);
                return 0;
        }
 
+       if (errno != ENOENT) {
+               fprintf(stderr, "sha1 file %s: %s", filename, strerror(errno));
+               return -1;
+       }
+
+       snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
+
+       fd = mkstemp(tmpfile);
+       if (fd < 0) {
+               fprintf(stderr, "unable to create temporary sha1 filename %s: %s", tmpfile, strerror(errno));
+               return -1;
+       }
+
        /* Set it up */
        memset(&stream, 0, sizeof(stream));
        deflateInit(&stream, Z_BEST_COMPRESSION);
-       size = deflateBound(&stream, len);
-       compressed = malloc(size);
+       size = deflateBound(&stream, len+hdrlen);
+       compressed = xmalloc(size);
 
        /* Compress it */
-       stream.next_in = buf;
-       stream.avail_in = len;
        stream.next_out = compressed;
        stream.avail_out = size;
+
+       /* First header.. */
+       stream.next_in = hdr;
+       stream.avail_in = hdrlen;
+       while (deflate(&stream, 0) == Z_OK)
+               /* nothing */;
+
+       /* Then the data itself.. */
+       stream.next_in = buf;
+       stream.avail_in = len;
        while (deflate(&stream, Z_FINISH) == Z_OK)
                /* nothing */;
        deflateEnd(&stream);
@@ -278,53 +1189,199 @@ int write_sha1_file(char *buf, unsigned len, unsigned char *returnsha1)
 
        if (write(fd, compressed, size) != size)
                die("unable to write file");
+       fchmod(fd, 0444);
        close(fd);
-               
+       free(compressed);
+
+       ret = link(tmpfile, filename);
+       if (ret < 0) {
+               ret = errno;
+
+               /*
+                * Coda hack - coda doesn't like cross-directory links,
+                * so we fall back to a rename, which will mean that it
+                * won't be able to check collisions, but that's not a
+                * big deal.
+                *
+                * When this succeeds, we just return 0. We have nothing
+                * left to unlink.
+                */
+               if (ret == EXDEV && !rename(tmpfile, filename))
+                       return 0;
+       }
+       unlink(tmpfile);
+       if (ret) {
+               if (ret != EEXIST) {
+                       fprintf(stderr, "unable to write sha1 filename %s: %s", filename, strerror(ret));
+                       return -1;
+               }
+               /* FIXME!!! Collision check here ? */
+       }
+
        return 0;
 }
 
-static inline int collision_check(char *filename, void *buf, unsigned int size)
+int write_sha1_to_fd(int fd, const unsigned char *sha1)
 {
-#ifdef COLLISION_CHECK
-       void *map;
-       int fd = open(filename, O_RDONLY);
-       struct stat st;
-       int cmp;
+       ssize_t size;
+       unsigned long objsize;
+       int posn = 0;
+       char *buf = map_sha1_file_internal(sha1, &objsize, 0);
+       z_stream stream;
+       if (!buf) {
+               unsigned char *unpacked;
+               unsigned long len;
+               char type[20];
+               char hdr[50];
+               int hdrlen;
+               // need to unpack and recompress it by itself
+               unpacked = read_packed_sha1(sha1, type, &len);
 
-       /* Unreadable object, or object went away? Strange. */
-       if (fd < 0)
-               return -1;
+               hdrlen = sprintf(hdr, "%s %lu", type, len) + 1;
 
-       if (fstat(fd, &st) < 0 || size != st.st_size)
-               return -1;
+               /* Set it up */
+               memset(&stream, 0, sizeof(stream));
+               deflateInit(&stream, Z_BEST_COMPRESSION);
+               size = deflateBound(&stream, len + hdrlen);
+               buf = xmalloc(size);
 
-       map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
-       close(fd);
-       if (map == MAP_FAILED)
-               return -1;
-       cmp = memcmp(buf, map, size);
-       munmap(map, size);
-       if (cmp)
-               return -1;
-#endif
+               /* Compress it */
+               stream.next_out = buf;
+               stream.avail_out = size;
+               
+               /* First header.. */
+               stream.next_in = hdr;
+               stream.avail_in = hdrlen;
+               while (deflate(&stream, 0) == Z_OK)
+                       /* nothing */;
+
+               /* Then the data itself.. */
+               stream.next_in = unpacked;
+               stream.avail_in = len;
+               while (deflate(&stream, Z_FINISH) == Z_OK)
+                       /* nothing */;
+               deflateEnd(&stream);
+               
+               objsize = stream.total_out;
+       }
+
+       do {
+               size = write(fd, buf + posn, objsize - posn);
+               if (size <= 0) {
+                       if (!size) {
+                               fprintf(stderr, "write closed");
+                       } else {
+                               perror("write ");
+                       }
+                       return -1;
+               }
+               posn += size;
+       } while (posn < objsize);
        return 0;
 }
 
-int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
+int write_sha1_from_fd(const unsigned char *sha1, int fd)
 {
        char *filename = sha1_file_name(sha1);
-       int fd;
 
-       fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
-       if (fd < 0) {
-               if (errno != EEXIST)
+       int local;
+       z_stream stream;
+       unsigned char real_sha1[20];
+       unsigned char buf[4096];
+       unsigned char discard[4096];
+       int ret;
+       SHA_CTX c;
+
+       local = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
+
+       if (local < 0)
+               return error("Couldn't open %s\n", filename);
+
+       memset(&stream, 0, sizeof(stream));
+
+       inflateInit(&stream);
+
+       SHA1_Init(&c);
+
+       do {
+               ssize_t size;
+               size = read(fd, buf, 4096);
+               if (size <= 0) {
+                       close(local);
+                       unlink(filename);
+                       if (!size)
+                               return error("Connection closed?");
+                       perror("Reading from connection");
                        return -1;
-               if (collision_check(filename, buf, size))
-                       return error("SHA1 collision detected!"
-                                       " This is bad, bad, BAD!\a\n");
-               return 0;
+               }
+               write(local, buf, size);
+               stream.avail_in = size;
+               stream.next_in = buf;
+               do {
+                       stream.next_out = discard;
+                       stream.avail_out = sizeof(discard);
+                       ret = inflate(&stream, Z_SYNC_FLUSH);
+                       SHA1_Update(&c, discard, sizeof(discard) -
+                                   stream.avail_out);
+               } while (stream.avail_in && ret == Z_OK);
+               
+       } while (ret == Z_OK);
+       inflateEnd(&stream);
+
+       close(local);
+       SHA1_Final(real_sha1, &c);
+       if (ret != Z_STREAM_END) {
+               unlink(filename);
+               return error("File %s corrupted", sha1_to_hex(sha1));
        }
-       write(fd, buf, size);
-       close(fd);
+       if (memcmp(sha1, real_sha1, 20)) {
+               unlink(filename);
+               return error("File %s has bad hash\n", sha1_to_hex(sha1));
+       }
+       
        return 0;
 }
+
+int has_sha1_pack(const unsigned char *sha1)
+{
+       struct pack_entry e;
+       return find_pack_entry(sha1, &e);
+}
+
+int has_sha1_file(const unsigned char *sha1)
+{
+       struct stat st;
+       struct pack_entry e;
+
+       if (find_sha1_file(sha1, &st))
+               return 1;
+       return find_pack_entry(sha1, &e);
+}
+
+int index_fd(unsigned char *sha1, int fd, struct stat *st, int write_object, const char *type)
+{
+       unsigned long size = st->st_size;
+       void *buf;
+       int ret;
+       unsigned char hdr[50];
+       int hdrlen;
+
+       buf = "";
+       if (size)
+               buf = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
+       close(fd);
+       if ((int)(long)buf == -1)
+               return -1;
+
+       if (!type)
+               type = "blob";
+       if (write_object)
+               ret = write_sha1_file(buf, size, type, sha1);
+       else {
+               write_sha1_file_prepare(buf, size, type, sha1, hdr, &hdrlen);
+               ret = 0;
+       }
+       if (size)
+               munmap(buf, size);
+       return ret;
+}