[PATCH] Deltification library work by Nicolas Pitre.

This patch adds the basic library functions to create and replay delta
information.  Also included is a test-delta utility to validate the
code.

diff-delta was based on LibXDiff written by Davide Libenzi

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/Makefile b/Makefile
index cde27275fad8103084d7ed2d08d246ba4ce6eb9c..272d956d0dd3c8fe343b09bb7cba51e8dac6ac32 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -36,9 +36,9 @@ install: $(PROG) $(SCRIPTS)
        $(INSTALL) $(PROG) $(SCRIPTS) $(dest)$(bin)
 
 LIB_OBJS=read-cache.o sha1_file.o usage.o object.o commit.o tree.o blob.o \
-        tag.o date.o
+        tag.o date.o diff-delta.o patch-delta.o
 LIB_FILE=libgit.a
-LIB_H=cache.h object.h blob.h tree.h commit.h tag.h
+LIB_H=cache.h object.h blob.h tree.h commit.h tag.h delta.h
 
 LIB_H += strbuf.h
 LIB_OBJS += strbuf.o
@@ -72,6 +72,9 @@ $(LIB_FILE): $(LIB_OBJS)
 test-date: test-date.c date.o
        $(CC) $(CFLAGS) -o $@ test-date.c date.o
 
+test-delta: test-delta.c diff-delta.o patch-delta.o
+       $(CC) $(CFLAGS) -o $@ $^
+
 git-%: %.c $(LIB_FILE)
        $(CC) $(CFLAGS) -o $@ $(filter %.c,$^) $(LIBS)
 

diff --git a/delta.h b/delta.h
new file mode 100644 (file)
index 0000000..e073dff
--- /dev/null
+++ b/delta.h
@@ -0,0 +1,6 @@
+extern void *diff_delta(void *from_buf, unsigned long from_size,
+                       void *to_buf, unsigned long to_size,
+                       unsigned long *delta_size);
+extern void *patch_delta(void *src_buf, unsigned long src_size,
+                        void *delta_buf, unsigned long delta_size,
+                        unsigned long *dst_size);

diff --git a/diff-delta.c b/diff-delta.c
new file mode 100644 (file)
index 0000000..480f03c
--- /dev/null
+++ b/diff-delta.c
@@ -0,0 +1,333 @@
+/*
+ * diff-delta.c: generate a delta between two buffers
+ *
+ *  Many parts of this file have been lifted from LibXDiff version 0.10.
+ *  http://www.xmailserver.org/xdiff-lib.html
+ *
+ *  LibXDiff was written by Davide Libenzi <davidel@xmailserver.org>
+ *  Copyright (C) 2003 Davide Libenzi
+ *
+ *  Many mods for GIT usage by Nicolas Pitre <nico@cam.org>, (C) 2005.
+ *
+ *  This file is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Lesser General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2.1 of the License, or (at your option) any later version.
+ *
+ *  Use of this within git automatically means that the LGPL
+ *  licensing gets turned into GPLv2 within this project.
+ */
+
+#include <stdlib.h>
+#include "delta.h"
+
+
+/* block size: min = 16, max = 64k, power of 2 */
+#define BLK_SIZE 16
+
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+
+#define GR_PRIME 0x9e370001
+#define HASH(v, b) (((unsigned int)(v) * GR_PRIME) >> (32 - (b)))
+       
+/* largest prime smaller than 65536 */
+#define BASE 65521
+
+/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
+#define NMAX 5552
+
+#define DO1(buf, i)  { s1 += buf[i]; s2 += s1; }
+#define DO2(buf, i)  DO1(buf, i); DO1(buf, i + 1);
+#define DO4(buf, i)  DO2(buf, i); DO2(buf, i + 2);
+#define DO8(buf, i)  DO4(buf, i); DO4(buf, i + 4);
+#define DO16(buf)    DO8(buf, 0); DO8(buf, 8);
+
+static unsigned int adler32(unsigned int adler, const unsigned char *buf, int len)
+{
+       int k;
+       unsigned int s1 = adler & 0xffff;
+       unsigned int s2 = adler >> 16;
+
+       while (len > 0) {
+               k = MIN(len, NMAX);
+               len -= k;
+               while (k >= 16) {
+                       DO16(buf);
+                       buf += 16;
+                       k -= 16;
+               }
+               if (k != 0)
+                       do {
+                               s1 += *buf++;
+                               s2 += s1;
+                       } while (--k);
+               s1 %= BASE;
+               s2 %= BASE;
+       }
+
+       return (s2 << 16) | s1;
+}
+
+static unsigned int hashbits(unsigned int size)
+{
+       unsigned int val = 1, bits = 0;
+       while (val < size && bits < 32) {
+               val <<= 1;
+               bits++;
+       }
+       return bits ? bits: 1;
+}
+
+typedef struct s_chanode {
+       struct s_chanode *next;
+       int icurr;
+} 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;
+}
+
+static void *cha_alloc(chastore_t *cha)
+{
+       chanode_t *ancur;
+       void *data;
+
+       ancur = cha->ancur;
+       if (!ancur || ancur->icurr == cha->nsize) {
+               ancur = malloc(sizeof(chanode_t) + cha->nsize);
+               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;
+               cha->ancur = ancur;
+       }
+
+       data = (void *)ancur + sizeof(chanode_t) + ancur->icurr;
+       ancur->icurr += cha->isize;
+       return data;
+}
+
+static void cha_free(chastore_t *cha)
+{
+       chanode_t *cur = cha->head;
+       while (cur) {
+               chanode_t *tmp = cur;
+               cur = cur->next;
+               free(tmp);
+       }
+}
+
+typedef struct s_bdrecord {
+       struct s_bdrecord *next;
+       unsigned int fp;
+       const unsigned char *ptr;
+} bdrecord_t;
+
+typedef struct s_bdfile {
+       const unsigned char *data, *top;
+       chastore_t cha;
+       unsigned int fphbits;
+       bdrecord_t **fphash;
+} bdfile_t;
+
+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;
+       bdrecord_t *brec;
+       bdrecord_t **fphash;
+
+       fphbits = hashbits(bufsize / BLK_SIZE + 1);
+       hsize = 1 << fphbits;
+       fphash = malloc(hsize * sizeof(bdrecord_t *));
+       if (!fphash)
+               return -1;
+       for (i = 0; i < hsize; i++)
+               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;
+       if (data == top)
+               data -= BLK_SIZE;
+
+       for ( ; data >= base; data -= BLK_SIZE) {
+               brec = cha_alloc(&bdf->cha);
+               if (!brec) {
+                       cha_free(&bdf->cha);
+                       free(fphash);
+                       return -1;
+               }
+               brec->fp = adler32(0, data, MIN(BLK_SIZE, top - data));
+               brec->ptr = data;
+               i = HASH(brec->fp, fphbits);
+               brec->next = fphash[i];
+               fphash[i] = brec;
+       }
+
+       bdf->fphbits = fphbits;
+       bdf->fphash = fphash;
+
+       return 0;
+}
+
+static void delta_cleanup(bdfile_t *bdf)
+{
+       free(bdf->fphash);
+       cha_free(&bdf->cha);
+}
+
+#define COPYOP_SIZE(o, s) \
+    (!!(o & 0xff) + !!(o & 0xff00) + !!(o & 0xff0000) + !!(o & 0xff000000) + \
+     !!(s & 0xff) + !!(s & 0xff00) + 1)
+
+void *diff_delta(void *from_buf, unsigned long from_size,
+                void *to_buf, unsigned long to_size,
+                unsigned long *delta_size)
+{
+       int i, outpos, outsize, inscnt, csize, msize, moff;
+       unsigned int fp;
+       const unsigned char *data, *top, *ptr1, *ptr2;
+       unsigned char *out, *orig;
+       bdrecord_t *brec;
+       bdfile_t bdf;
+
+       if (!from_size || !to_size || delta_prepare(from_buf, from_size, &bdf))
+               return NULL;
+       
+       outpos = 0;
+       outsize = 8192;
+       out = malloc(outsize);
+       if (!out) {
+               delta_cleanup(&bdf);
+               return NULL;
+       }
+
+       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);
+
+       /* 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);
+
+       inscnt = 0;
+       moff = 0;
+       while (data < top) {
+               msize = 0;
+               fp = adler32(0, data, MIN(top - data, BLK_SIZE));
+               i = HASH(fp, bdf.fphbits);
+               for (brec = bdf.fphash[i]; brec; brec = brec->next) {
+                       if (brec->fp == fp) {
+                               csize = bdf.top - brec->ptr;
+                               if (csize > top - data)
+                                       csize = top - data;
+                               for (ptr1 = brec->ptr, ptr2 = data; 
+                                    csize && *ptr1 == *ptr2;
+                                    csize--, ptr1++, ptr2++);
+
+                               csize = ptr1 - brec->ptr;
+                               if (csize > msize) {
+                                       moff = brec->ptr - bdf.data;
+                                       msize = csize;
+                                       if (msize >= 0x10000) {
+                                               msize = 0x10000;
+                                               break;
+                                       }
+                               }
+                       }
+               }
+
+               if (!msize || msize < COPYOP_SIZE(moff, msize)) {
+                       if (!inscnt)
+                               outpos++;
+                       out[outpos++] = *data++;
+                       inscnt++;
+                       if (inscnt == 0x7f) {
+                               out[outpos - inscnt - 1] = inscnt;
+                               inscnt = 0;
+                       }
+               } else {
+                       if (inscnt) {
+                               out[outpos - inscnt - 1] = inscnt;
+                               inscnt = 0;
+                       }
+
+                       data += msize;
+                       orig = out + outpos++;
+                       i = 0x80;
+
+                       if (moff & 0xff) { out[outpos++] = moff; i |= 0x01; }
+                       moff >>= 8;
+                       if (moff & 0xff) { out[outpos++] = moff; i |= 0x02; }
+                       moff >>= 8;
+                       if (moff & 0xff) { out[outpos++] = moff; i |= 0x04; }
+                       moff >>= 8;
+                       if (moff & 0xff) { out[outpos++] = moff; i |= 0x08; }
+
+                       if (msize & 0xff) { out[outpos++] = msize; i |= 0x10; }
+                       msize >>= 8;
+                       if (msize & 0xff) { out[outpos++] = msize; i |= 0x20; }
+
+                       *orig = i;
+               }
+
+               /* next time around the largest possible output is 1 + 4 + 3 */
+               if (outpos > outsize - 8) {
+                       void *tmp = out;
+                       outsize = outsize * 3 / 2;
+                       out = realloc(out, outsize);
+                       if (!out) {
+                               free(tmp);
+                               delta_cleanup(&bdf);
+                               return NULL;
+                       }
+               }
+       }
+
+       if (inscnt)
+               out[outpos - inscnt - 1] = inscnt;
+
+       delta_cleanup(&bdf);
+       *delta_size = outpos;
+       return out;
+}

diff --git a/patch-delta.c b/patch-delta.c
new file mode 100644 (file)
index 0000000..a8d75ee
--- /dev/null
+++ b/patch-delta.c
@@ -0,0 +1,88 @@
+/*
+ * patch-delta.c:
+ * recreate a buffer from a source and the delta produced by diff-delta.c
+ *
+ * (C) 2005 Nicolas Pitre <nico@cam.org>
+ *
+ * This code is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include "delta.h"
+
+void *patch_delta(void *src_buf, unsigned long src_size,
+                 void *delta_buf, unsigned long delta_size,
+                 unsigned long *dst_size)
+{
+       const unsigned char *data, *top;
+       unsigned char *dst_buf, *out, cmd;
+       unsigned long size;
+       int i;
+
+       /* the smallest delta size possible is 6 bytes */
+       if (delta_size < 6)
+               return NULL;
+
+       data = delta_buf;
+       top = delta_buf + delta_size;
+
+       /* make sure the orig file size matches what we expect */
+       size = i = 0;
+       cmd = *data++;
+       while (cmd) {
+               if (cmd & 1)
+                       size |= *data++ << i;
+               i += 8;
+               cmd >>= 1;
+       }
+       if (size != src_size)
+               return NULL;
+
+       /* now the result size */
+       size = i = 0;
+       cmd = *data++;
+       while (cmd) {
+               if (cmd & 1)
+                       size |= *data++ << i;
+               i += 8;
+               cmd >>= 1;
+       }
+       dst_buf = malloc(size);
+       if (!dst_buf)
+               return NULL;
+
+       out = dst_buf;
+       while (data < top) {
+               cmd = *data++;
+               if (cmd & 0x80) {
+                       unsigned long cp_off = 0, cp_size = 0;
+                       const unsigned char *buf;
+                       if (cmd & 0x01) cp_off = *data++;
+                       if (cmd & 0x02) cp_off |= (*data++ << 8);
+                       if (cmd & 0x04) cp_off |= (*data++ << 16);
+                       if (cmd & 0x08) cp_off |= (*data++ << 24);
+                       if (cmd & 0x10) cp_size = *data++;
+                       if (cmd & 0x20) cp_size |= (*data++ << 8);
+                       if (cp_size == 0) cp_size = 0x10000;
+                       buf = (cmd & 0x40) ? dst_buf : src_buf;
+                       memcpy(out, buf + cp_off, cp_size);
+                       out += cp_size;
+               } else {
+                       memcpy(out, data, cmd);
+                       out += cmd;
+                       data += cmd;
+               }
+       }
+
+       /* sanity check */
+       if (data != top || out - dst_buf != size) {
+               free(dst_buf);
+               return NULL;
+       }
+
+       *dst_size = size;
+       return dst_buf;
+}

diff --git a/test-delta.c b/test-delta.c
new file mode 100644 (file)
index 0000000..8751e27
--- /dev/null
+++ b/test-delta.c
@@ -0,0 +1,79 @@
+/*
+ * test-delta.c: test code to exercise diff-delta.c and patch-delta.c
+ *
+ * (C) 2005 Nicolas Pitre <nico@cam.org>
+ *
+ * This code is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include "delta.h"
+
+static const char *usage =
+       "test-delta (-d|-p) <from_file> <data_file> <out_file>";
+
+int main(int argc, char *argv[])
+{
+       int fd;
+       struct stat st;
+       void *from_buf, *data_buf, *out_buf;
+       unsigned long from_size, data_size, out_size;
+
+       if (argc != 5 || (strcmp(argv[1], "-d") && strcmp(argv[1], "-p"))) {
+               fprintf(stderr, "Usage: %s\n", usage);
+               return 1;
+       }
+
+       fd = open(argv[2], O_RDONLY);
+       if (fd < 0 || fstat(fd, &st)) {
+               perror(argv[2]);
+               return 1;
+       }
+       from_size = st.st_size;
+       from_buf = mmap(NULL, from_size, PROT_READ, MAP_PRIVATE, fd, 0);
+       if (from_buf == MAP_FAILED) {
+               perror(argv[2]);
+               return 1;
+       }
+       close(fd);
+
+       fd = open(argv[3], O_RDONLY);
+       if (fd < 0 || fstat(fd, &st)) {
+               perror(argv[3]);
+               return 1;
+       }
+       data_size = st.st_size;
+       data_buf = mmap(NULL, data_size, PROT_READ, MAP_PRIVATE, fd, 0);
+       if (data_buf == MAP_FAILED) {
+               perror(argv[3]);
+               return 1;
+       }
+       close(fd);
+
+       if (argv[1][1] == 'd')
+               out_buf = diff_delta(from_buf, from_size,
+                                    data_buf, data_size, &out_size);
+       else
+               out_buf = patch_delta(from_buf, from_size,
+                                     data_buf, data_size, &out_size);
+       if (!out_buf) {
+               fprintf(stderr, "delta operation failed (returned NULL)\n");
+               return 1;
+       }
+
+       fd = open (argv[4], O_WRONLY|O_CREAT|O_TRUNC, 0666);
+       if (fd < 0 || write(fd, out_buf, out_size) != out_size) {
+               perror(argv[4]);
+               return 1;
+       }
+
+       return 0;
+}