git-describe: documentation.

diff --git a/diff-delta.c b/diff-delta.c
index 480f03cd16841945352c176b50300613fbf71175..890986eeb022816da078794555a9a0135783bd40 100644 (file)
--- a/diff-delta.c
+++ b/diff-delta.c
@@ -84,20 +84,15 @@ typedef struct s_chanode {
 } chanode_t;
 
 typedef struct s_chastore {
-       chanode_t *head, *tail;
        int isize, nsize;
        chanode_t *ancur;
-       chanode_t *sncur;
-       int scurr;
 } chastore_t;
 
 static void cha_init(chastore_t *cha, int isize, int icount)
 {
-       cha->head = cha->tail = NULL;
        cha->isize = isize;
        cha->nsize = icount * isize;
-       cha->ancur = cha->sncur = NULL;
-       cha->scurr = 0;
+       cha->ancur = NULL;
 }
 
 static void *cha_alloc(chastore_t *cha)
@@ -111,12 +106,7 @@ static void *cha_alloc(chastore_t *cha)
                if (!ancur)
                        return NULL;
                ancur->icurr = 0;
-               ancur->next = NULL;
-               if (cha->tail)
-                       cha->tail->next = ancur;
-               if (!cha->head)
-                       cha->head = ancur;
-               cha->tail = ancur;
+               ancur->next = cha->ancur;
                cha->ancur = ancur;
        }
 
@@ -127,7 +117,7 @@ static void *cha_alloc(chastore_t *cha)
 
 static void cha_free(chastore_t *cha)
 {
-       chanode_t *cur = cha->head;
+       chanode_t *cur = cha->ancur;
        while (cur) {
                chanode_t *tmp = cur;
                cur = cur->next;
@@ -142,7 +132,6 @@ typedef struct s_bdrecord {
 } bdrecord_t;
 
 typedef struct s_bdfile {
-       const unsigned char *data, *top;
        chastore_t cha;
        unsigned int fphbits;
        bdrecord_t **fphash;
@@ -152,7 +141,7 @@ static int delta_prepare(const unsigned char *buf, int bufsize, bdfile_t *bdf)
 {
        unsigned int fphbits;
        int i, hsize;
-       const unsigned char *base, *data, *top;
+       const unsigned char *data, *top;
        bdrecord_t *brec;
        bdrecord_t **fphash;
 
@@ -165,13 +154,12 @@ static int delta_prepare(const unsigned char *buf, int bufsize, bdfile_t *bdf)
                fphash[i] = NULL;
        cha_init(&bdf->cha, sizeof(bdrecord_t), hsize / 4 + 1);
 
-       bdf->data = data = base = buf;
-       bdf->top = top = buf + bufsize;
-       data += (bufsize / BLK_SIZE) * BLK_SIZE;
+       top = buf + bufsize;
+       data = buf + (bufsize / BLK_SIZE) * BLK_SIZE;
        if (data == top)
                data -= BLK_SIZE;
 
-       for ( ; data >= base; data -= BLK_SIZE) {
+       for ( ; data >= buf; data -= BLK_SIZE) {
                brec = cha_alloc(&bdf->cha);
                if (!brec) {
                        cha_free(&bdf->cha);
@@ -203,11 +191,12 @@ static void delta_cleanup(bdfile_t *bdf)
 
 void *diff_delta(void *from_buf, unsigned long from_size,
                 void *to_buf, unsigned long to_size,
-                unsigned long *delta_size)
+                unsigned long *delta_size,
+                unsigned long max_size)
 {
        int i, outpos, outsize, inscnt, csize, msize, moff;
        unsigned int fp;
-       const unsigned char *data, *top, *ptr1, *ptr2;
+       const unsigned char *ref_data, *ref_top, *data, *top, *ptr1, *ptr2;
        unsigned char *out, *orig;
        bdrecord_t *brec;
        bdfile_t bdf;
@@ -223,32 +212,28 @@ void *diff_delta(void *from_buf, unsigned long from_size,
                return NULL;
        }
 
+       ref_data = from_buf;
+       ref_top = from_buf + from_size;
        data = to_buf;
        top = to_buf + to_size;
 
        /* store reference buffer size */
-       orig = out + outpos++;
-       *orig = i = 0;
-       do {
-               if (from_size & 0xff) {
-                       *orig |= (1 << i);
-                       out[outpos++] = from_size;
-               }
-               i++;
-               from_size >>= 8;
-       } while (from_size);
+       out[outpos++] = from_size;
+       from_size >>= 7;
+       while (from_size) {
+               out[outpos - 1] |= 0x80;
+               out[outpos++] = from_size;
+               from_size >>= 7;
+       }
 
        /* store target buffer size */
-       orig = out + outpos++;
-       *orig = i = 0;
-       do {
-               if (to_size & 0xff) {
-                       *orig |= (1 << i);
-                       out[outpos++] = to_size;
-               }
-               i++;
-               to_size >>= 8;
-       } while (to_size);
+       out[outpos++] = to_size;
+       to_size >>= 7;
+       while (to_size) {
+               out[outpos - 1] |= 0x80;
+               out[outpos++] = to_size;
+               to_size >>= 7;
+       }
 
        inscnt = 0;
        moff = 0;
@@ -258,7 +243,7 @@ void *diff_delta(void *from_buf, unsigned long from_size,
                i = HASH(fp, bdf.fphbits);
                for (brec = bdf.fphash[i]; brec; brec = brec->next) {
                        if (brec->fp == fp) {
-                               csize = bdf.top - brec->ptr;
+                               csize = ref_top - brec->ptr;
                                if (csize > top - data)
                                        csize = top - data;
                                for (ptr1 = brec->ptr, ptr2 = data; 
@@ -267,7 +252,7 @@ void *diff_delta(void *from_buf, unsigned long from_size,
 
                                csize = ptr1 - brec->ptr;
                                if (csize > msize) {
-                                       moff = brec->ptr - bdf.data;
+                                       moff = brec->ptr - ref_data;
                                        msize = csize;
                                        if (msize >= 0x10000) {
                                                msize = 0x10000;
@@ -311,6 +296,12 @@ void *diff_delta(void *from_buf, unsigned long from_size,
                        *orig = i;
                }
 
+               if (max_size && outpos > max_size) {
+                       free(out);
+                       delta_cleanup(&bdf);
+                       return NULL;
+               }
+
                /* next time around the largest possible output is 1 + 4 + 3 */
                if (outpos > outsize - 8) {
                        void *tmp = out;