delta: move delta application to delta.c

Move the delta application functions into `delta.c`, next to the
similar delta creation functions.  Make the `git__delta_apply`
functions adhere to other naming and parameter style within the
library.

src/delta-apply.c

-/*
- * Copyright (C) the libgit2 contributors. All rights reserved.
- *
- * This file is part of libgit2, distributed under the GNU GPL v2 with
- * a Linking Exception. For full terms see the included COPYING file.
- */
-#include "common.h"
-#include "git2/odb.h"
-#include "delta-apply.h"
-
-/*
- * This file was heavily cribbed from BinaryDelta.java in JGit, which
- * itself was heavily cribbed from <code>patch-delta.c</code> in the
- * GIT project.	The original delta patching code was written by
- * Nicolas Pitre <nico@cam.org>.
- */
-
-static int hdr_sz(
-	size_t *size,
-	const unsigned char **delta,
-	const unsigned char *end)
-{
-	const unsigned char *d = *delta;
-	size_t r = 0;
-	unsigned int c, shift = 0;
-
-	do {
-		if (d == end)
-			return -1;
-		c = *d++;
-		r |= (c & 0x7f) << shift;
-		shift += 7;
-	} while (c & 0x80);
-	*delta = d;
-	*size = r;
-	return 0;
-}
-
-int git__delta_read_header(
-	const unsigned char *delta,
-	size_t delta_len,
-	size_t *base_sz,
-	size_t *res_sz)
-{
-	const unsigned char *delta_end = delta + delta_len;
-	if ((hdr_sz(base_sz, &delta, delta_end) < 0) ||
-	    (hdr_sz(res_sz, &delta, delta_end) < 0))
-		return -1;
-	return 0;
-}
-
-#define DELTA_HEADER_BUFFER_LEN 16
-int git__delta_read_header_fromstream(size_t *base_sz, size_t *res_sz, git_packfile_stream *stream)
-{
-	static const size_t buffer_len = DELTA_HEADER_BUFFER_LEN;
-	unsigned char buffer[DELTA_HEADER_BUFFER_LEN];
-	const unsigned char *delta, *delta_end;
-	size_t len;
-	ssize_t read;
-
-	len = read = 0;
-	while (len < buffer_len) {
-		read = git_packfile_stream_read(stream, &buffer[len], buffer_len - len);
-
-		if (read == 0)
-			break;
-
-		if (read == GIT_EBUFS)
-			continue;
-
-		len += read;
-	}
-
-	delta = buffer;
-	delta_end = delta + len;
-	if ((hdr_sz(base_sz, &delta, delta_end) < 0) ||
-	    (hdr_sz(res_sz, &delta, delta_end) < 0))
-		return -1;
-
-	return 0;
-}
-
-int git__delta_apply(
-	git_rawobj *out,
-	const unsigned char *base,
-	size_t base_len,
-	const unsigned char *delta,
-	size_t delta_len)
-{
-	const unsigned char *delta_end = delta + delta_len;
-	size_t base_sz, res_sz, alloc_sz;
-	unsigned char *res_dp;
-
-	/* Check that the base size matches the data we were given;
-	 * if not we would underflow while accessing data from the
-	 * base object, resulting in data corruption or segfault.
-	 */
-	if ((hdr_sz(&base_sz, &delta, delta_end) < 0) || (base_sz != base_len)) {
-		giterr_set(GITERR_INVALID, "Failed to apply delta. Base size does not match given data");
-		return -1;
-	}
-
-	if (hdr_sz(&res_sz, &delta, delta_end) < 0) {
-		giterr_set(GITERR_INVALID, "Failed to apply delta. Base size does not match given data");
-		return -1;
-	}
-
-	GITERR_CHECK_ALLOC_ADD(&alloc_sz, res_sz, 1);
-	res_dp = git__malloc(alloc_sz);
-	GITERR_CHECK_ALLOC(res_dp);
-
-	res_dp[res_sz] = '\0';
-	out->data = res_dp;
-	out->len = res_sz;
-
-	while (delta < delta_end) {
-		unsigned char cmd = *delta++;
-		if (cmd & 0x80) {
-			/* cmd is a copy instruction; copy from the base.
-			 */
-			size_t off = 0, len = 0;
-
-			if (cmd & 0x01) off = *delta++;
-			if (cmd & 0x02) off |= *delta++ << 8UL;
-			if (cmd & 0x04) off |= *delta++ << 16UL;
-			if (cmd & 0x08) off |= *delta++ << 24UL;
-
-			if (cmd & 0x10) len = *delta++;
-			if (cmd & 0x20) len |= *delta++ << 8UL;
-			if (cmd & 0x40) len |= *delta++ << 16UL;
-			if (!len)		len = 0x10000;
-
-			if (base_len < off + len || res_sz < len)
-				goto fail;
-			memcpy(res_dp, base + off, len);
-			res_dp += len;
-			res_sz -= len;
-
-		} else if (cmd) {
-			/* cmd is a literal insert instruction; copy from
-			 * the delta stream itself.
-			 */
-			if (delta_end - delta < cmd || res_sz < cmd)
-				goto fail;
-			memcpy(res_dp, delta, cmd);
-			delta += cmd;
-			res_dp += cmd;
-			res_sz -= cmd;
-
-		} else {
-			/* cmd == 0 is reserved for future encodings.
-			 */
-			goto fail;
-		}
-	}
-
-	if (delta != delta_end || res_sz)
-		goto fail;
-	return 0;
-
-fail:
-	git__free(out->data);
-	out->data = NULL;
-	giterr_set(GITERR_INVALID, "Failed to apply delta");
-	return -1;
-}

src/delta-apply.h

-/*
- * Copyright (C) the libgit2 contributors. All rights reserved.
- *
- * This file is part of libgit2, distributed under the GNU GPL v2 with
- * a Linking Exception. For full terms see the included COPYING file.
- */
-#ifndef INCLUDE_delta_apply_h__
-#define INCLUDE_delta_apply_h__
-
-#include "odb.h"
-#include "pack.h"
-
-/**
- * Apply a git binary delta to recover the original content.
- *
- * @param out the output buffer to receive the original data.
- *		Only out->data and out->len are populated, as this is
- *		the only information available in the delta.
- * @param base the base to copy from during copy instructions.
- * @param base_len number of bytes available at base.
- * @param delta the delta to execute copy/insert instructions from.
- * @param delta_len total number of bytes in the delta.
- * @return
- * - 0 on a successful delta unpack.
- * - GIT_ERROR if the delta is corrupt or doesn't match the base.
- */
-extern int git__delta_apply(
-	git_rawobj *out,
-	const unsigned char *base,
-	size_t base_len,
-	const unsigned char *delta,
-	size_t delta_len);
-
-/**
- * Read the header of a git binary delta.
- *
- * @param delta the delta to execute copy/insert instructions from.
- * @param delta_len total number of bytes in the delta.
- * @param base_sz pointer to store the base size field.
- * @param res_sz pointer to store the result size field.
- * @return
- * - 0 on a successful decoding the header.
- * - GIT_ERROR if the delta is corrupt.
- */
-extern int git__delta_read_header(
-	const unsigned char *delta,
-	size_t delta_len,
-	size_t *base_sz,
-	size_t *res_sz);
-
-/**
- * Read the header of a git binary delta
- *
- * This variant reads just enough from the packfile stream to read the
- * delta header.
- */
-extern int git__delta_read_header_fromstream(
-	size_t *base_sz,
-	size_t *res_sz,
-	git_packfile_stream *stream);
-
-#endif

src/delta.c

@@ -441,3 +441,170 @@ git_delta_create(
 	*delta_size = outpos;
 	return out;
 }
+
+/*
+* Delta application was heavily cribbed from BinaryDelta.java in JGit, which
+* itself was heavily cribbed from <code>patch-delta.c</code> in the
+* GIT project.	The original delta patching code was written by
+* Nicolas Pitre <nico@cam.org>.
+*/
+
+static int hdr_sz(
+	size_t *size,
+	const unsigned char **delta,
+	const unsigned char *end)
+{
+	const unsigned char *d = *delta;
+	size_t r = 0;
+	unsigned int c, shift = 0;
+
+	do {
+		if (d == end)
+			return -1;
+		c = *d++;
+		r |= (c & 0x7f) << shift;
+		shift += 7;
+	} while (c & 0x80);
+	*delta = d;
+	*size = r;
+	return 0;
+}
+
+int git_delta_read_header(
+	size_t *base_out,
+	size_t *result_out,
+	const unsigned char *delta,
+	size_t delta_len)
+{
+	const unsigned char *delta_end = delta + delta_len;
+	if ((hdr_sz(base_out, &delta, delta_end) < 0) ||
+		(hdr_sz(result_out, &delta, delta_end) < 0))
+		return -1;
+	return 0;
+}
+
+#define DELTA_HEADER_BUFFER_LEN 16
+int git_delta_read_header_fromstream(
+	size_t *base_sz, size_t *res_sz, git_packfile_stream *stream)
+{
+	static const size_t buffer_len = DELTA_HEADER_BUFFER_LEN;
+	unsigned char buffer[DELTA_HEADER_BUFFER_LEN];
+	const unsigned char *delta, *delta_end;
+	size_t len;
+	ssize_t read;
+
+	len = read = 0;
+	while (len < buffer_len) {
+		read = git_packfile_stream_read(stream, &buffer[len], buffer_len - len);
+
+		if (read == 0)
+			break;
+
+		if (read == GIT_EBUFS)
+			continue;
+
+		len += read;
+	}
+
+	delta = buffer;
+	delta_end = delta + len;
+	if ((hdr_sz(base_sz, &delta, delta_end) < 0) ||
+		(hdr_sz(res_sz, &delta, delta_end) < 0))
+		return -1;
+
+	return 0;
+}
+
+int git_delta_apply(
+	void **out,
+	size_t *out_len,
+	const unsigned char *base,
+	size_t base_len,
+	const unsigned char *delta,
+	size_t delta_len)
+{
+	const unsigned char *delta_end = delta + delta_len;
+	size_t base_sz, res_sz, alloc_sz;
+	unsigned char *res_dp;
+
+	*out = NULL;
+	*out_len = 0;
+
+	/* Check that the base size matches the data we were given;
+	* if not we would underflow while accessing data from the
+	* base object, resulting in data corruption or segfault.
+	*/
+	if ((hdr_sz(&base_sz, &delta, delta_end) < 0) || (base_sz != base_len)) {
+		giterr_set(GITERR_INVALID, "Failed to apply delta. Base size does not match given data");
+		return -1;
+	}
+
+	if (hdr_sz(&res_sz, &delta, delta_end) < 0) {
+		giterr_set(GITERR_INVALID, "Failed to apply delta. Base size does not match given data");
+		return -1;
+	}
+
+	GITERR_CHECK_ALLOC_ADD(&alloc_sz, res_sz, 1);
+	res_dp = git__malloc(alloc_sz);
+	GITERR_CHECK_ALLOC(res_dp);
+
+	res_dp[res_sz] = '\0';
+	*out = res_dp;
+	*out_len = res_sz;
+
+	while (delta < delta_end) {
+		unsigned char cmd = *delta++;
+		if (cmd & 0x80) {
+			/* cmd is a copy instruction; copy from the base.
+			*/
+			size_t off = 0, len = 0;
+
+			if (cmd & 0x01) off = *delta++;
+			if (cmd & 0x02) off |= *delta++ << 8UL;
+			if (cmd & 0x04) off |= *delta++ << 16UL;
+			if (cmd & 0x08) off |= *delta++ << 24UL;
+
+			if (cmd & 0x10) len = *delta++;
+			if (cmd & 0x20) len |= *delta++ << 8UL;
+			if (cmd & 0x40) len |= *delta++ << 16UL;
+			if (!len)		len = 0x10000;
+
+			if (base_len < off + len || res_sz < len)
+				goto fail;
+			memcpy(res_dp, base + off, len);
+			res_dp += len;
+			res_sz -= len;
+
+		}
+		else if (cmd) {
+			/* cmd is a literal insert instruction; copy from
+			* the delta stream itself.
+			*/
+			if (delta_end - delta < cmd || res_sz < cmd)
+				goto fail;
+			memcpy(res_dp, delta, cmd);
+			delta += cmd;
+			res_dp += cmd;
+			res_sz -= cmd;
+
+		}
+		else {
+			/* cmd == 0 is reserved for future encodings.
+			*/
+			goto fail;
+		}
+	}
+
+	if (delta != delta_end || res_sz)
+		goto fail;
+	return 0;
+
+fail:
+	git__free(*out);
+
+	*out = NULL;
+	*out_len = 0;
+
+	giterr_set(GITERR_INVALID, "Failed to apply delta");
+	return -1;
+}

src/delta.h

@@ -6,6 +6,7 @@
 #define INCLUDE_git_delta_h__
 
 #include "common.h"
+#include "pack.h"
 
 /* opaque object for delta index */
 struct git_delta_index;
@@ -19,8 +20,8 @@ struct git_delta_index;
  * before free_delta_index() is called.  The returned pointer must be freed
  * using free_delta_index().
  */
-extern struct git_delta_index *
-git_delta_create_index(const void *buf, unsigned long bufsize);
+extern struct git_delta_index *git_delta_create_index(
+	const void *buf, unsigned long bufsize);
 
 /*
  * free_delta_index: free the index created by create_delta_index()
@@ -111,4 +112,50 @@ GIT_INLINE(unsigned long) git_delta_get_hdr_size(
 	return size;
 }
 
+/**
+* Apply a git binary delta to recover the original content.
+* The caller is responsible for freeing the returned buffer.
+*
+* @param out the output buffer
+* @param out_len the length of the output buffer
+* @param base the base to copy from during copy instructions.
+* @param base_len number of bytes available at base.
+* @param delta the delta to execute copy/insert instructions from.
+* @param delta_len total number of bytes in the delta.
+* @return 0 on success or an error code
+*/
+extern int git_delta_apply(
+	void **out,
+	size_t *out_len,
+	const unsigned char *base,
+	size_t base_len,
+	const unsigned char *delta,
+	size_t delta_len);
+
+/**
+* Read the header of a git binary delta.
+*
+* @param base_out pointer to store the base size field.
+* @param result_out pointer to store the result size field.
+* @param delta the delta to execute copy/insert instructions from.
+* @param delta_len total number of bytes in the delta.
+* @return 0 on success or an error code
+*/
+extern int git_delta_read_header(
+	size_t *base_out,
+	size_t *result_out,
+	const unsigned char *delta,
+	size_t delta_len);
+
+/**
+ * Read the header of a git binary delta
+ *
+ * This variant reads just enough from the packfile stream to read the
+ * delta header.
+ */
+extern int git_delta_read_header_fromstream(
+	size_t *base_out,
+	size_t *result_out,
+	git_packfile_stream *stream);
+
 #endif

src/odb.c

@@ -12,7 +12,7 @@
 #include "fileops.h"
 #include "hash.h"
 #include "odb.h"
-#include "delta-apply.h"
+#include "delta.h"
 #include "filter.h"
 #include "repository.h"
 

src/odb_loose.c

@@ -12,7 +12,7 @@
 #include "fileops.h"
 #include "hash.h"
 #include "odb.h"
-#include "delta-apply.h"
+#include "delta.h"
 #include "filebuf.h"
 
 #include "git2/odb_backend.h"

src/odb_pack.c

@@ -13,7 +13,7 @@
 #include "fileops.h"
 #include "hash.h"
 #include "odb.h"
-#include "delta-apply.h"
+#include "delta.h"
 #include "sha1_lookup.h"
 #include "mwindow.h"
 #include "pack.h"

src/pack.c

@@ -8,7 +8,7 @@
 #include "common.h"
 #include "odb.h"
 #include "pack.h"
-#include "delta-apply.h"
+#include "delta.h"
 #include "sha1_lookup.h"
 #include "mwindow.h"
 #include "fileops.h"
@@ -505,7 +505,7 @@ int git_packfile_resolve_header(
 		git_mwindow_close(&w_curs);
 		if ((error = git_packfile_stream_open(&stream, p, curpos)) < 0)
 			return error;
-		error = git__delta_read_header_fromstream(&base_size, size_p, &stream);
+		error = git_delta_read_header_fromstream(&base_size, size_p, &stream);
 		git_packfile_stream_free(&stream);
 		if (error < 0)
 			return error;
@@ -730,8 +730,9 @@ int git_packfile_unpack(
 		obj->len = 0;
 		obj->type = GIT_OBJ_BAD;
 
-		error = git__delta_apply(obj, base.data, base.len, delta.data, delta.len);
+		error = git_delta_apply(&obj->data, &obj->len, base.data, base.len, delta.data, delta.len);
 		obj->type = base_type;
+
 		/*
 		 * We usually don't want to free the base at this
 		 * point, as we put it into the cache in the previous