git-tar-tree: no more void pointer arithmetic

[git.git] / diff-delta.c

diff --git a/diff-delta.c b/diff-delta.c
index 35e517d..25a798d 100644 (file)
--- a/diff-delta.c
+++ b/diff-delta.c
@@ -136,11 +136,12 @@ struct delta_index {
 
 struct delta_index * create_delta_index(const void *buf, unsigned long bufsize)
 {
-       unsigned int i, hsize, hmask, entries, *hash_count;
+       unsigned int i, hsize, hmask, entries, prev_val, *hash_count;
        const unsigned char *data, *buffer = buf;
        struct delta_index *index;
        struct index_entry *entry, **hash;
        void *mem;
+       unsigned long memsize;
 
        if (!buf || !bufsize)
                return NULL;
@@ -155,9 +156,10 @@ struct delta_index * create_delta_index(const void *buf, unsigned long bufsize)
        hmask = hsize - 1;
 
        /* allocate lookup index */
-       mem = malloc(sizeof(*index) +
-                    sizeof(*hash) * hsize +
-                    sizeof(*entry) * entries);
+       memsize = sizeof(*index) +
+                 sizeof(*hash) * hsize +
+                 sizeof(*entry) * entries;
+       mem = malloc(memsize);
        if (!mem)
                return NULL;
        index = mem;
@@ -179,18 +181,25 @@ struct delta_index * create_delta_index(const void *buf, unsigned long bufsize)
        }
 
        /* then populate the index */
-       data = buffer + entries * RABIN_WINDOW - RABIN_WINDOW;
-       while (data >= buffer) {
+       prev_val = ~0;
+       for (data = buffer + entries * RABIN_WINDOW - RABIN_WINDOW;
+            data >= buffer;
+            data -= RABIN_WINDOW) {
                unsigned int val = 0;
                for (i = 1; i <= RABIN_WINDOW; i++)
                        val = ((val << 8) | data[i]) ^ T[val >> RABIN_SHIFT];
-               i = val & hmask;
-               entry->ptr = data + RABIN_WINDOW;
-               entry->val = val;
-               entry->next = hash[i];
-               hash[i] = entry++;
-               hash_count[i]++;
-               data -= RABIN_WINDOW;
+               if (val == prev_val) {
+                       /* keep the lowest of consecutive identical blocks */
+                       entry[-1].ptr = data + RABIN_WINDOW;
+               } else {
+                       prev_val = val;
+                       i = val & hmask;
+                       entry->ptr = data + RABIN_WINDOW;
+                       entry->val = val;
+                       entry->next = hash[i];
+                       hash[i] = entry++;
+                       hash_count[i]++;
+               }
        }
 
        /*
@@ -239,7 +248,7 @@ create_delta(const struct delta_index *index,
             const void *trg_buf, unsigned long trg_size,
             unsigned long *delta_size, unsigned long max_size)
 {
-       unsigned int i, outpos, outsize, hash_mask, val;
+       unsigned int i, outpos, outsize, val;
        int inscnt;
        const unsigned char *ref_data, *ref_top, *data, *top;
        unsigned char *out;
@@ -275,7 +284,6 @@ create_delta(const struct delta_index *index,
        ref_top = ref_data + index->src_size;
        data = trg_buf;
        top = trg_buf + trg_size;
-       hash_mask = index->hash_mask;
 
        outpos++;
        val = 0;
@@ -290,7 +298,7 @@ create_delta(const struct delta_index *index,
                struct index_entry *entry;
                val ^= U[data[-RABIN_WINDOW]];
                val = ((val << 8) | *data) ^ T[val >> RABIN_SHIFT];
-               i = val & hash_mask;
+               i = val & index->hash_mask;
                for (entry = index->hash[i]; entry; entry = entry->next) {
                        const unsigned char *ref = entry->ptr;
                        const unsigned char *src = data;