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[gitweb.git] / pack-objects.c
index cde4afa798e093922f3e25738a65b6cc8f400fea..179560f2bd67e08d25bef0199c41ee0ee70793f9 100644 (file)
@@ -1,8 +1,13 @@
 #include "cache.h"
 #include "object.h"
+#include "blob.h"
+#include "commit.h"
+#include "tag.h"
+#include "tree.h"
 #include "delta.h"
 #include "pack.h"
 #include "csum-file.h"
+#include "tree-walk.h"
 #include <sys/time.h>
 #include <signal.h>
 
@@ -27,6 +32,10 @@ struct object_entry {
        struct object_entry *delta_sibling; /* other deltified objects who
                                             * uses the same base as me
                                             */
+       int preferred_base;     /* we do not pack this, but is encouraged to
+                                * be used as the base objectto delta huge
+                                * objects against.
+                                */
 };
 
 /*
@@ -49,7 +58,7 @@ static int local = 0;
 static int incremental = 0;
 static struct object_entry **sorted_by_sha, **sorted_by_type;
 static struct object_entry *objects = NULL;
-static int nr_objects = 0, nr_alloc = 0;
+static int nr_objects = 0, nr_alloc = 0, nr_result = 0;
 static const char *base_name;
 static unsigned char pack_file_sha1[20];
 static int progress = 1;
@@ -91,7 +100,7 @@ static int reused_delta = 0;
 
 static int pack_revindex_ix(struct packed_git *p)
 {
-       unsigned int ui = (unsigned int) p;
+       unsigned long ui = (unsigned long)p;
        int i;
 
        ui = ui ^ (ui >> 16); /* defeat structure alignment */
@@ -147,7 +156,7 @@ static void prepare_pack_revindex(struct pack_revindex *rix)
 
        rix->revindex = xmalloc(sizeof(unsigned long) * (num_ent + 1));
        for (i = 0; i < num_ent; i++) {
-               long hl = *((long *)(index + 24 * i));
+               unsigned int hl = *((unsigned int *)(index + 24 * i));
                rix->revindex[i] = ntohl(hl);
        }
        /* This knows the pack format -- the 20-byte trailer
@@ -231,7 +240,8 @@ static int encode_header(enum object_type type, unsigned long size, unsigned cha
        return n;
 }
 
-static unsigned long write_object(struct sha1file *f, struct object_entry *entry)
+static unsigned long write_object(struct sha1file *f,
+                                 struct object_entry *entry)
 {
        unsigned long size;
        char type[10];
@@ -241,6 +251,9 @@ static unsigned long write_object(struct sha1file *f, struct object_entry *entry
        enum object_type obj_type;
        int to_reuse = 0;
 
+       if (entry->preferred_base)
+               return 0;
+
        obj_type = entry->type;
        if (! entry->in_pack)
                to_reuse = 0;   /* can't reuse what we don't have */
@@ -335,20 +348,22 @@ static void write_pack_file(void)
                do_progress = progress;
        }
        if (do_progress)
-               fprintf(stderr, "Writing %d objects.\n", nr_objects);
+               fprintf(stderr, "Writing %d objects.\n", nr_result);
 
        hdr.hdr_signature = htonl(PACK_SIGNATURE);
        hdr.hdr_version = htonl(PACK_VERSION);
-       hdr.hdr_entries = htonl(nr_objects);
+       hdr.hdr_entries = htonl(nr_result);
        sha1write(f, &hdr, sizeof(hdr));
        offset = sizeof(hdr);
+       if (!nr_result)
+               goto done;
        for (i = 0; i < nr_objects; i++) {
                offset = write_one(f, objects + i, offset);
                if (do_progress) {
-                       unsigned percent = written * 100 / nr_objects;
+                       unsigned percent = written * 100 / nr_result;
                        if (progress_update || percent != last_percent) {
                                fprintf(stderr, "%4u%% (%u/%u) done\r",
-                                       percent, written, nr_objects);
+                                       percent, written, nr_result);
                                progress_update = 0;
                                last_percent = percent;
                        }
@@ -356,16 +371,17 @@ static void write_pack_file(void)
        }
        if (do_progress)
                fputc('\n', stderr);
-
+ done:
        sha1close(f, pack_file_sha1, 1);
 }
 
 static void write_index_file(void)
 {
        int i;
-       struct sha1file *f = sha1create("%s-%s.%s", base_name, sha1_to_hex(object_list_sha1), "idx");
+       struct sha1file *f = sha1create("%s-%s.%s", base_name,
+                                       sha1_to_hex(object_list_sha1), "idx");
        struct object_entry **list = sorted_by_sha;
-       struct object_entry **last = list + nr_objects;
+       struct object_entry **last = list + nr_result;
        unsigned int array[256];
 
        /*
@@ -390,7 +406,7 @@ static void write_index_file(void)
         * Write the actual SHA1 entries..
         */
        list = sorted_by_sha;
-       for (i = 0; i < nr_objects; i++) {
+       for (i = 0; i < nr_result; i++) {
                struct object_entry *entry = *list++;
                unsigned int offset = htonl(entry->offset);
                sha1write(f, &offset, 4);
@@ -400,27 +416,97 @@ static void write_index_file(void)
        sha1close(f, NULL, 1);
 }
 
-static int add_object_entry(unsigned char *sha1, unsigned int hash)
+static int locate_object_entry_hash(const unsigned char *sha1)
+{
+       int i;
+       unsigned int ui;
+       memcpy(&ui, sha1, sizeof(unsigned int));
+       i = ui % object_ix_hashsz;
+       while (0 < object_ix[i]) {
+               if (!memcmp(sha1, objects[object_ix[i]-1].sha1, 20))
+                       return i;
+               if (++i == object_ix_hashsz)
+                       i = 0;
+       }
+       return -1 - i;
+}
+
+static struct object_entry *locate_object_entry(const unsigned char *sha1)
+{
+       int i;
+
+       if (!object_ix_hashsz)
+               return NULL;
+
+       i = locate_object_entry_hash(sha1);
+       if (0 <= i)
+               return &objects[object_ix[i]-1];
+       return NULL;
+}
+
+static void rehash_objects(void)
+{
+       int i;
+       struct object_entry *oe;
+
+       object_ix_hashsz = nr_objects * 3;
+       if (object_ix_hashsz < 1024)
+               object_ix_hashsz = 1024;
+       object_ix = xrealloc(object_ix, sizeof(int) * object_ix_hashsz);
+       memset(object_ix, 0, sizeof(int) * object_ix_hashsz);
+       for (i = 0, oe = objects; i < nr_objects; i++, oe++) {
+               int ix = locate_object_entry_hash(oe->sha1);
+               if (0 <= ix)
+                       continue;
+               ix = -1 - ix;
+               object_ix[ix] = i + 1;
+       }
+}
+
+static unsigned name_hash(const char *name)
+{
+       unsigned char c;
+       unsigned hash = 0;
+
+       /*
+        * This effectively just creates a sortable number from the
+        * last sixteen non-whitespace characters. Last characters
+        * count "most", so things that end in ".c" sort together.
+        */
+       while ((c = *name++) != 0) {
+               if (isspace(c))
+                       continue;
+               hash = (hash >> 2) + (c << 24);
+       }
+       return hash;
+}
+
+static int add_object_entry(const unsigned char *sha1, unsigned hash, int exclude)
 {
        unsigned int idx = nr_objects;
        struct object_entry *entry;
        struct packed_git *p;
        unsigned int found_offset = 0;
        struct packed_git *found_pack = NULL;
-
-       for (p = packed_git; p; p = p->next) {
-               struct pack_entry e;
-               if (find_pack_entry_one(sha1, &e, p)) {
-                       if (incremental)
-                               return 0;
-                       if (local && !p->pack_local)
-                               return 0;
-                       if (!found_pack) {
-                               found_offset = e.offset;
-                               found_pack = e.p;
+       int ix, status = 0;
+
+       if (!exclude) {
+               for (p = packed_git; p; p = p->next) {
+                       struct pack_entry e;
+                       if (find_pack_entry_one(sha1, &e, p)) {
+                               if (incremental)
+                                       return 0;
+                               if (local && !p->pack_local)
+                                       return 0;
+                               if (!found_pack) {
+                                       found_offset = e.offset;
+                                       found_pack = e.p;
+                               }
                        }
                }
        }
+       if ((entry = locate_object_entry(sha1)) != NULL)
+               goto already_added;
 
        if (idx >= nr_alloc) {
                unsigned int needed = (idx + 1024) * 3 / 2;
@@ -428,45 +514,283 @@ static int add_object_entry(unsigned char *sha1, unsigned int hash)
                nr_alloc = needed;
        }
        entry = objects + idx;
+       nr_objects = idx + 1;
        memset(entry, 0, sizeof(*entry));
        memcpy(entry->sha1, sha1, 20);
        entry->hash = hash;
-       if (found_pack) {
-               entry->in_pack = found_pack;
-               entry->in_pack_offset = found_offset;
+
+       if (object_ix_hashsz * 3 <= nr_objects * 4)
+               rehash_objects();
+       else {
+               ix = locate_object_entry_hash(entry->sha1);
+               if (0 <= ix)
+                       die("internal error in object hashing.");
+               object_ix[-1 - ix] = idx + 1;
        }
-       nr_objects = idx+1;
-       return 1;
+       status = 1;
+
+ already_added:
+       if (progress_update) {
+               fprintf(stderr, "Counting objects...%d\r", nr_objects);
+               progress_update = 0;
+       }
+       if (exclude)
+               entry->preferred_base = 1;
+       else {
+               if (found_pack) {
+                       entry->in_pack = found_pack;
+                       entry->in_pack_offset = found_offset;
+               }
+       }
+       return status;
 }
 
-static int locate_object_entry_hash(unsigned char *sha1)
+struct pbase_tree_cache {
+       unsigned char sha1[20];
+       int ref;
+       int temporary;
+       void *tree_data;
+       unsigned long tree_size;
+};
+
+static struct pbase_tree_cache *(pbase_tree_cache[256]);
+static int pbase_tree_cache_ix(const unsigned char *sha1)
+{
+       return sha1[0] % ARRAY_SIZE(pbase_tree_cache);
+}
+static int pbase_tree_cache_ix_incr(int ix)
+{
+       return (ix+1) % ARRAY_SIZE(pbase_tree_cache);
+}
+
+static struct pbase_tree {
+       struct pbase_tree *next;
+       /* This is a phony "cache" entry; we are not
+        * going to evict it nor find it through _get()
+        * mechanism -- this is for the toplevel node that
+        * would almost always change with any commit.
+        */
+       struct pbase_tree_cache pcache;
+} *pbase_tree;
+
+static struct pbase_tree_cache *pbase_tree_get(const unsigned char *sha1)
+{
+       struct pbase_tree_cache *ent, *nent;
+       void *data;
+       unsigned long size;
+       char type[20];
+       int neigh;
+       int my_ix = pbase_tree_cache_ix(sha1);
+       int available_ix = -1;
+
+       /* pbase-tree-cache acts as a limited hashtable.
+        * your object will be found at your index or within a few
+        * slots after that slot if it is cached.
+        */
+       for (neigh = 0; neigh < 8; neigh++) {
+               ent = pbase_tree_cache[my_ix];
+               if (ent && !memcmp(ent->sha1, sha1, 20)) {
+                       ent->ref++;
+                       return ent;
+               }
+               else if (((available_ix < 0) && (!ent || !ent->ref)) ||
+                        ((0 <= available_ix) &&
+                         (!ent && pbase_tree_cache[available_ix])))
+                       available_ix = my_ix;
+               if (!ent)
+                       break;
+               my_ix = pbase_tree_cache_ix_incr(my_ix);
+       }
+
+       /* Did not find one.  Either we got a bogus request or
+        * we need to read and perhaps cache.
+        */
+       data = read_sha1_file(sha1, type, &size);
+       if (!data)
+               return NULL;
+       if (strcmp(type, tree_type)) {
+               free(data);
+               return NULL;
+       }
+
+       /* We need to either cache or return a throwaway copy */
+
+       if (available_ix < 0)
+               ent = NULL;
+       else {
+               ent = pbase_tree_cache[available_ix];
+               my_ix = available_ix;
+       }
+
+       if (!ent) {
+               nent = xmalloc(sizeof(*nent));
+               nent->temporary = (available_ix < 0);
+       }
+       else {
+               /* evict and reuse */
+               free(ent->tree_data);
+               nent = ent;
+       }
+       memcpy(nent->sha1, sha1, 20);
+       nent->tree_data = data;
+       nent->tree_size = size;
+       nent->ref = 1;
+       if (!nent->temporary)
+               pbase_tree_cache[my_ix] = nent;
+       return nent;
+}
+
+static void pbase_tree_put(struct pbase_tree_cache *cache)
+{
+       if (!cache->temporary) {
+               cache->ref--;
+               return;
+       }
+       free(cache->tree_data);
+       free(cache);
+}
+
+static int name_cmp_len(const char *name)
 {
        int i;
-       unsigned int ui;
-       memcpy(&ui, sha1, sizeof(unsigned int));
-       i = ui % object_ix_hashsz;
-       while (0 < object_ix[i]) {
-               if (!memcmp(sha1, objects[object_ix[i]-1].sha1, 20))
-                       return i;
-               if (++i == object_ix_hashsz)
-                       i = 0;
+       for (i = 0; name[i] && name[i] != '\n' && name[i] != '/'; i++)
+               ;
+       return i;
+}
+
+static void add_pbase_object(struct tree_desc *tree,
+                            const char *name,
+                            int cmplen,
+                            const char *fullname)
+{
+       struct name_entry entry;
+
+       while (tree_entry(tree,&entry)) {
+               unsigned long size;
+               char type[20];
+
+               if (entry.pathlen != cmplen ||
+                   memcmp(entry.path, name, cmplen) ||
+                   !has_sha1_file(entry.sha1) ||
+                   sha1_object_info(entry.sha1, type, &size))
+                       continue;
+               if (name[cmplen] != '/') {
+                       unsigned hash = name_hash(fullname);
+                       add_object_entry(entry.sha1, hash, 1);
+                       return;
+               }
+               if (!strcmp(type, tree_type)) {
+                       struct tree_desc sub;
+                       struct pbase_tree_cache *tree;
+                       const char *down = name+cmplen+1;
+                       int downlen = name_cmp_len(down);
+
+                       tree = pbase_tree_get(entry.sha1);
+                       if (!tree)
+                               return;
+                       sub.buf = tree->tree_data;
+                       sub.size = tree->tree_size;
+
+                       add_pbase_object(&sub, down, downlen, fullname);
+                       pbase_tree_put(tree);
+               }
        }
-       return -1 - i;
 }
 
-static struct object_entry *locate_object_entry(unsigned char *sha1)
+static unsigned *done_pbase_paths;
+static int done_pbase_paths_num;
+static int done_pbase_paths_alloc;
+static int done_pbase_path_pos(unsigned hash)
 {
-       int i = locate_object_entry_hash(sha1);
-       if (0 <= i)
-               return &objects[object_ix[i]-1];
-       return NULL;
+       int lo = 0;
+       int hi = done_pbase_paths_num;
+       while (lo < hi) {
+               int mi = (hi + lo) / 2;
+               if (done_pbase_paths[mi] == hash)
+                       return mi;
+               if (done_pbase_paths[mi] < hash)
+                       hi = mi;
+               else
+                       lo = mi + 1;
+       }
+       return -lo-1;
+}
+
+static int check_pbase_path(unsigned hash)
+{
+       int pos = (!done_pbase_paths) ? -1 : done_pbase_path_pos(hash);
+       if (0 <= pos)
+               return 1;
+       pos = -pos - 1;
+       if (done_pbase_paths_alloc <= done_pbase_paths_num) {
+               done_pbase_paths_alloc = alloc_nr(done_pbase_paths_alloc);
+               done_pbase_paths = xrealloc(done_pbase_paths,
+                                           done_pbase_paths_alloc *
+                                           sizeof(unsigned));
+       }
+       done_pbase_paths_num++;
+       if (pos < done_pbase_paths_num)
+               memmove(done_pbase_paths + pos + 1,
+                       done_pbase_paths + pos,
+                       (done_pbase_paths_num - pos - 1) * sizeof(unsigned));
+       done_pbase_paths[pos] = hash;
+       return 0;
+}
+
+static void add_preferred_base_object(char *name, unsigned hash)
+{
+       struct pbase_tree *it;
+       int cmplen = name_cmp_len(name);
+
+       if (check_pbase_path(hash))
+               return;
+
+       for (it = pbase_tree; it; it = it->next) {
+               if (cmplen == 0) {
+                       hash = name_hash("");
+                       add_object_entry(it->pcache.sha1, hash, 1);
+               }
+               else {
+                       struct tree_desc tree;
+                       tree.buf = it->pcache.tree_data;
+                       tree.size = it->pcache.tree_size;
+                       add_pbase_object(&tree, name, cmplen, name);
+               }
+       }
+}
+
+static void add_preferred_base(unsigned char *sha1)
+{
+       struct pbase_tree *it;
+       void *data;
+       unsigned long size;
+       unsigned char tree_sha1[20];
+
+       data = read_object_with_reference(sha1, tree_type, &size, tree_sha1);
+       if (!data)
+               return;
+
+       for (it = pbase_tree; it; it = it->next) {
+               if (!memcmp(it->pcache.sha1, tree_sha1, 20)) {
+                       free(data);
+                       return;
+               }
+       }
+
+       it = xcalloc(1, sizeof(*it));
+       it->next = pbase_tree;
+       pbase_tree = it;
+
+       memcpy(it->pcache.sha1, tree_sha1, 20);
+       it->pcache.tree_data = data;
+       it->pcache.tree_size = size;
 }
 
 static void check_object(struct object_entry *entry)
 {
        char type[20];
 
-       if (entry->in_pack) {
+       if (entry->in_pack && !entry->preferred_base) {
                unsigned char base[20];
                unsigned long size;
                struct object_entry *base_entry;
@@ -485,7 +809,8 @@ static void check_object(struct object_entry *entry)
                 */
                if (!no_reuse_delta &&
                    entry->in_pack_type == OBJ_DELTA &&
-                   (base_entry = locate_object_entry(base))) {
+                   (base_entry = locate_object_entry(base)) &&
+                   (!base_entry->preferred_base)) {
 
                        /* Depth value does not matter - find_deltas()
                         * will never consider reused delta as the
@@ -510,38 +835,19 @@ static void check_object(struct object_entry *entry)
                die("unable to get type of object %s",
                    sha1_to_hex(entry->sha1));
 
-       if (!strcmp(type, "commit")) {
+       if (!strcmp(type, commit_type)) {
                entry->type = OBJ_COMMIT;
-       } else if (!strcmp(type, "tree")) {
+       } else if (!strcmp(type, tree_type)) {
                entry->type = OBJ_TREE;
-       } else if (!strcmp(type, "blob")) {
+       } else if (!strcmp(type, blob_type)) {
                entry->type = OBJ_BLOB;
-       } else if (!strcmp(type, "tag")) {
+       } else if (!strcmp(type, tag_type)) {
                entry->type = OBJ_TAG;
        } else
                die("unable to pack object %s of type %s",
                    sha1_to_hex(entry->sha1), type);
 }
 
-static void hash_objects(void)
-{
-       int i;
-       struct object_entry *oe;
-
-       object_ix_hashsz = nr_objects * 2;
-       object_ix = xcalloc(sizeof(int), object_ix_hashsz);
-       for (i = 0, oe = objects; i < nr_objects; i++, oe++) {
-               int ix = locate_object_entry_hash(oe->sha1);
-               if (0 <= ix) {
-                       error("the same object '%s' added twice",
-                             sha1_to_hex(oe->sha1));
-                       continue;
-               }
-               ix = -1 - ix;
-               object_ix[ix] = i + 1;
-       }
-}
-
 static unsigned int check_delta_limit(struct object_entry *me, unsigned int n)
 {
        struct object_entry *child = me->delta_child;
@@ -560,14 +866,26 @@ static void get_object_details(void)
        int i;
        struct object_entry *entry;
 
-       hash_objects();
        prepare_pack_ix();
        for (i = 0, entry = objects; i < nr_objects; i++, entry++)
                check_object(entry);
-       for (i = 0, entry = objects; i < nr_objects; i++, entry++)
-               if (!entry->delta && entry->delta_child)
-                       entry->delta_limit =
-                               check_delta_limit(entry, 1);
+
+       if (nr_objects == nr_result) {
+               /*
+                * Depth of objects that depend on the entry -- this
+                * is subtracted from depth-max to break too deep
+                * delta chain because of delta data reusing.
+                * However, we loosen this restriction when we know we
+                * are creating a thin pack -- it will have to be
+                * expanded on the other end anyway, so do not
+                * artificially cut the delta chain and let it go as
+                * deep as it wants.
+                */
+               for (i = 0, entry = objects; i < nr_objects; i++, entry++)
+                       if (!entry->delta && entry->delta_child)
+                               entry->delta_limit =
+                                       check_delta_limit(entry, 1);
+       }
 }
 
 typedef int (*entry_sort_t)(const struct object_entry *, const struct object_entry *);
@@ -598,6 +916,24 @@ static int sha1_sort(const struct object_entry *a, const struct object_entry *b)
        return memcmp(a->sha1, b->sha1, 20);
 }
 
+static struct object_entry **create_final_object_list(void)
+{
+       struct object_entry **list;
+       int i, j;
+
+       for (i = nr_result = 0; i < nr_objects; i++)
+               if (!objects[i].preferred_base)
+                       nr_result++;
+       list = xmalloc(nr_result * sizeof(struct object_entry *));
+       for (i = j = 0; i < nr_objects; i++) {
+               if (!objects[i].preferred_base)
+                       list[j++] = objects + i;
+       }
+       current_sort = sha1_sort;
+       qsort(list, nr_result, sizeof(struct object_entry *), sort_comparator);
+       return list;
+}
+
 static int type_size_sort(const struct object_entry *a, const struct object_entry *b)
 {
        if (a->type < b->type)
@@ -608,6 +944,10 @@ static int type_size_sort(const struct object_entry *a, const struct object_entr
                return -1;
        if (a->hash > b->hash)
                return 1;
+       if (a->preferred_base < b->preferred_base)
+               return -1;
+       if (a->preferred_base > b->preferred_base)
+               return 1;
        if (a->size < b->size)
                return -1;
        if (a->size > b->size)
@@ -618,6 +958,7 @@ static int type_size_sort(const struct object_entry *a, const struct object_entr
 struct unpacked {
        struct object_entry *entry;
        void *data;
+       struct delta_index *index;
 };
 
 /*
@@ -628,59 +969,59 @@ struct unpacked {
  * more importantly, the bigger file is likely the more recent
  * one.
  */
-static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_depth)
+static int try_delta(struct unpacked *trg, struct unpacked *src,
+                    struct delta_index *src_index, unsigned max_depth)
 {
-       struct object_entry *cur_entry = cur->entry;
-       struct object_entry *old_entry = old->entry;
-       unsigned long size, oldsize, delta_size, sizediff;
-       long max_size;
+       struct object_entry *trg_entry = trg->entry;
+       struct object_entry *src_entry = src->entry;
+       unsigned long size, src_size, delta_size, sizediff, max_size;
        void *delta_buf;
 
        /* Don't bother doing diffs between different types */
-       if (cur_entry->type != old_entry->type)
+       if (trg_entry->type != src_entry->type)
                return -1;
 
-       /* If the current object is at edge, take the depth the objects
-        * that depend on the current object into account -- otherwise
-        * they would become too deep.
+       /* We do not compute delta to *create* objects we are not
+        * going to pack.
         */
-       if (cur_entry->delta_child) {
-               if (max_depth <= cur_entry->delta_limit)
-                       return 0;
-               max_depth -= cur_entry->delta_limit;
-       }
-
-       size = cur_entry->size;
-       if (size < 50)
+       if (trg_entry->preferred_base)
                return -1;
-       oldsize = old_entry->size;
-       sizediff = oldsize > size ? oldsize - size : size - oldsize;
-       if (sizediff > size / 8)
-               return -1;
-       if (old_entry->depth >= max_depth)
-               return 0;
 
        /*
-        * NOTE!
-        *
-        * We always delta from the bigger to the smaller, since that's
-        * more space-efficient (deletes don't have to say _what_ they
-        * delete).
+        * If the current object is at pack edge, take the depth the
+        * objects that depend on the current object into account --
+        * otherwise they would become too deep.
         */
-       max_size = size / 2 - 20;
-       if (cur_entry->delta)
-               max_size = cur_entry->delta_size-1;
+       if (trg_entry->delta_child) {
+               if (max_depth <= trg_entry->delta_limit)
+                       return 0;
+               max_depth -= trg_entry->delta_limit;
+       }
+       if (src_entry->depth >= max_depth)
+               return 0;
+
+       /* Now some size filtering heuristics. */
+       size = trg_entry->size;
+       max_size = size/2 - 20;
+       max_size = max_size * (max_depth - src_entry->depth) / max_depth;
+       if (max_size == 0)
+               return 0;
+       if (trg_entry->delta && trg_entry->delta_size <= max_size)
+               max_size = trg_entry->delta_size-1;
+       src_size = src_entry->size;
+       sizediff = src_size < size ? size - src_size : 0;
        if (sizediff >= max_size)
-               return -1;
-       delta_buf = diff_delta(old->data, oldsize,
-                              cur->data, size, &delta_size, max_size);
+               return 0;
+
+       delta_buf = create_delta(src_index, trg->data, size, &delta_size, max_size);
        if (!delta_buf)
                return 0;
-       cur_entry->delta = old_entry;
-       cur_entry->delta_size = delta_size;
-       cur_entry->depth = old_entry->depth + 1;
+
+       trg_entry->delta = src_entry;
+       trg_entry->delta_size = delta_size;
+       trg_entry->depth = src_entry->depth + 1;
        free(delta_buf);
-       return 0;
+       return 1;
 }
 
 static void progress_interval(int signum)
@@ -700,7 +1041,7 @@ static void find_deltas(struct object_entry **list, int window, int depth)
        i = nr_objects;
        idx = 0;
        if (progress)
-               fprintf(stderr, "Deltifying %d objects.\n", nr_objects);
+               fprintf(stderr, "Deltifying %d objects.\n", nr_result);
 
        while (--i >= 0) {
                struct object_entry *entry = list[i];
@@ -709,12 +1050,14 @@ static void find_deltas(struct object_entry **list, int window, int depth)
                char type[10];
                int j;
 
-               processed++;
+               if (!entry->preferred_base)
+                       processed++;
+
                if (progress) {
-                       unsigned percent = processed * 100 / nr_objects;
+                       unsigned percent = processed * 100 / nr_result;
                        if (percent != last_percent || progress_update) {
                                fprintf(stderr, "%4u%% (%u/%u) done\r",
-                                       percent, processed, nr_objects);
+                                       percent, processed, nr_result);
                                progress_update = 0;
                                last_percent = percent;
                        }
@@ -726,11 +1069,16 @@ static void find_deltas(struct object_entry **list, int window, int depth)
                         */
                        continue;
 
+               if (entry->size < 50)
+                       continue;
+               free_delta_index(n->index);
+               n->index = NULL;
                free(n->data);
                n->entry = entry;
                n->data = read_sha1_file(entry->sha1, type, &size);
                if (size != entry->size)
-                       die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
+                       die("object %s inconsistent object length (%lu vs %lu)",
+                           sha1_to_hex(entry->sha1), size, entry->size);
 
                j = window;
                while (--j > 0) {
@@ -741,9 +1089,20 @@ static void find_deltas(struct object_entry **list, int window, int depth)
                        m = array + other_idx;
                        if (!m->entry)
                                break;
-                       if (try_delta(n, m, depth) < 0)
+                       if (try_delta(n, m, m->index, depth) < 0)
                                break;
                }
+               /* if we made n a delta, and if n is already at max
+                * depth, leaving it in the window is pointless.  we
+                * should evict it first.
+                */
+               if (entry->delta && depth <= entry->depth)
+                       continue;
+
+               n->index = create_delta_index(n->data, size);
+               if (!n->index)
+                       die("out of memory");
+
                idx++;
                if (idx >= window)
                        idx = 0;
@@ -752,8 +1111,10 @@ static void find_deltas(struct object_entry **list, int window, int depth)
        if (progress)
                fputc('\n', stderr);
 
-       for (i = 0; i < window; ++i)
+       for (i = 0; i < window; ++i) {
+               free_delta_index(array[i].index);
                free(array[i].data);
+       }
        free(array);
 }
 
@@ -839,13 +1200,15 @@ static void setup_progress_signal(void)
 int main(int argc, char **argv)
 {
        SHA_CTX ctx;
-       char line[PATH_MAX + 20];
+       char line[40 + 1 + PATH_MAX + 2];
        int window = 10, depth = 10, pack_to_stdout = 0;
        struct object_entry **list;
+       int num_preferred_base = 0;
        int i;
 
        setup_git_directory();
 
+       progress = isatty(2);
        for (i = 1; i < argc; i++) {
                const char *arg = argv[i];
 
@@ -876,6 +1239,10 @@ int main(int argc, char **argv)
                                        usage(pack_usage);
                                continue;
                        }
+                       if (!strcmp("--progress", arg)) {
+                               progress = 1;
+                               continue;
+                       }
                        if (!strcmp("-q", arg)) {
                                progress = 0;
                                continue;
@@ -905,45 +1272,56 @@ int main(int argc, char **argv)
                setup_progress_signal();
        }
 
-       while (fgets(line, sizeof(line), stdin) != NULL) {
-               unsigned int hash;
-               char *p;
+       for (;;) {
                unsigned char sha1[20];
+               unsigned hash;
 
-               if (progress_update) {
-                       fprintf(stderr, "Counting objects...%d\r", nr_objects);
-                       progress_update = 0;
+               if (!fgets(line, sizeof(line), stdin)) {
+                       if (feof(stdin))
+                               break;
+                       if (!ferror(stdin))
+                               die("fgets returned NULL, not EOF, not error!");
+                       if (errno != EINTR)
+                               die("fgets: %s", strerror(errno));
+                       clearerr(stdin);
+                       continue;
+               }
+
+               if (line[0] == '-') {
+                       if (get_sha1_hex(line+1, sha1))
+                               die("expected edge sha1, got garbage:\n %s",
+                                   line+1);
+                       if (num_preferred_base++ < window)
+                               add_preferred_base(sha1);
+                       continue;
                }
                if (get_sha1_hex(line, sha1))
                        die("expected sha1, got garbage:\n %s", line);
-               hash = 0;
-               p = line+40;
-               while (*p) {
-                       unsigned char c = *p++;
-                       if (isspace(c))
-                               continue;
-                       hash = hash * 11 + c;
-               }
-               add_object_entry(sha1, hash);
+               hash = name_hash(line+41);
+               add_preferred_base_object(line+41, hash);
+               add_object_entry(sha1, hash, 0);
        }
        if (progress)
                fprintf(stderr, "Done counting %d objects.\n", nr_objects);
-       if (non_empty && !nr_objects)
+       sorted_by_sha = create_final_object_list();
+       if (non_empty && !nr_result)
                return 0;
 
-       sorted_by_sha = create_sorted_list(sha1_sort);
        SHA1_Init(&ctx);
        list = sorted_by_sha;
-       for (i = 0; i < nr_objects; i++) {
+       for (i = 0; i < nr_result; i++) {
                struct object_entry *entry = *list++;
                SHA1_Update(&ctx, entry->sha1, 20);
        }
        SHA1_Final(object_list_sha1, &ctx);
+       if (progress && (nr_objects != nr_result))
+               fprintf(stderr, "Result has %d objects.\n", nr_result);
 
        if (reuse_cached_pack(object_list_sha1, pack_to_stdout))
                ;
        else {
-               prepare_pack(window, depth);
+               if (nr_result)
+                       prepare_pack(window, depth);
                if (progress && pack_to_stdout) {
                        /* the other end usually displays progress itself */
                        struct itimerval v = {{0,},};
@@ -959,6 +1337,6 @@ int main(int argc, char **argv)
        }
        if (progress)
                fprintf(stderr, "Total %d, written %d (delta %d), reused %d (delta %d)\n",
-                       nr_objects, written, written_delta, reused, reused_delta);
+                       nr_result, written, written_delta, reused, reused_delta);
        return 0;
 }