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[PATCH v2 02/19] read-cache: split index file version specific functionality

From
Thomas Gummerer <t.gummerer@gmail.com>
Date
Jul 12, 2013, 17:26 UTC
Message-ID
<1373650024-3001-3-git-send-email-t.gummerer@gmail.com>
In-Reply-To
<1373650024-3001-1-git-send-email-t.gummerer@gmail.com>

Split index file version specific functionality to their own functions, to prepare for moving the index file version specific parts to their own file. This makes it easier to add a new index file format later.

Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
---
 cache.h              |   5 +-
 read-cache.c         | 130 +++++++++++++++++++++++++++++++++------------------
 test-index-version.c |   2 +-
 3 files changed, 90 insertions(+), 47 deletions(-)
diff --git a/cache.h b/cache.h
index c288678..7af853b 100644
--- a/cache.h
+++ b/cache.h
@@ -100,9 +100,12 @@ unsigned long git_deflate_bound(git_zstream *, unsigned long);
  */
 
 #define CACHE_SIGNATURE 0x44495243	/* "DIRC" */
-struct cache_header {
+struct cache_version_header {
 	unsigned int hdr_signature;
 	unsigned int hdr_version;
+};
+
+struct cache_header {
 	unsigned int hdr_entries;
 };
 
diff --git a/read-cache.c b/read-cache.c
index d5201f9..93947bf 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1268,10 +1268,8 @@ struct ondisk_cache_entry_extended {
 			    ondisk_cache_entry_extended_size(ce_namelen(ce)) : \
 			    ondisk_cache_entry_size(ce_namelen(ce)))
 
-static int verify_hdr(struct cache_header *hdr, unsigned long size)
+static int verify_hdr_version(struct cache_version_header *hdr, unsigned long size)
 {
-	git_SHA_CTX c;
-	unsigned char sha1[20];
 	int hdr_version;
 
 	if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
@@ -1279,10 +1277,22 @@ static int verify_hdr(struct cache_header *hdr, unsigned long size)
 	hdr_version = ntohl(hdr->hdr_version);
 	if (hdr_version < INDEX_FORMAT_LB || INDEX_FORMAT_UB < hdr_version)
 		return error("bad index version %d", hdr_version);
+	return 0;
+}
+
+static int verify_hdr(void *mmap, unsigned long size)
+{
+	git_SHA_CTX c;
+	unsigned char sha1[20];
+
+	if (size < sizeof(struct cache_version_header)
+	    + sizeof(struct cache_header) + 20)
+		die("index file smaller than expected");
+
 	git_SHA1_Init(&c);
-	git_SHA1_Update(&c, hdr, size - 20);
+	git_SHA1_Update(&c, mmap, size - 20);
 	git_SHA1_Final(sha1, &c);
-	if (hashcmp(sha1, (unsigned char *)hdr + size - 20))
+	if (hashcmp(sha1, (unsigned char *)mmap + size - 20))
 		return error("bad index file sha1 signature");
 	return 0;
 }
@@ -1424,47 +1434,19 @@ static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk,
 	return ce;
 }
 
-/* remember to discard_cache() before reading a different cache! */
-int read_index_from(struct index_state *istate, const char *path)
+static int read_index_v2(struct index_state *istate, void *mmap, unsigned long mmap_size)
 {
-	int fd, i;
-	struct stat st;
+	int i;
 	unsigned long src_offset;
-	struct cache_header *hdr;
-	void *mmap;
-	size_t mmap_size;
+	struct cache_version_header *hdr;
+	struct cache_header *hdr_v2;
 	struct strbuf previous_name_buf = STRBUF_INIT, *previous_name;
 
-	if (istate->initialized)
-		return istate->cache_nr;
-
-	istate->timestamp.sec = 0;
-	istate->timestamp.nsec = 0;
-	fd = open(path, O_RDONLY);
-	if (fd < 0) {
-		if (errno == ENOENT)
-			return 0;
-		die_errno("index file open failed");
-	}
-
-	if (fstat(fd, &st))
-		die_errno("cannot stat the open index");
-
-	mmap_size = xsize_t(st.st_size);
-	if (mmap_size < sizeof(struct cache_header) + 20)
-		die("index file smaller than expected");
-
-	mmap = xmmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
-	if (mmap == MAP_FAILED)
-		die_errno("unable to map index file");
-	close(fd);
-
 	hdr = mmap;
-	if (verify_hdr(hdr, mmap_size) < 0)
-		goto unmap;
+	hdr_v2 = (struct cache_header *)((char *)mmap + sizeof(*hdr));
 
 	istate->version = ntohl(hdr->hdr_version);
-	istate->cache_nr = ntohl(hdr->hdr_entries);
+	istate->cache_nr = ntohl(hdr_v2->hdr_entries);
 	istate->cache_alloc = alloc_nr(istate->cache_nr);
 	istate->cache = xcalloc(istate->cache_alloc, sizeof(*istate->cache));
 	istate->initialized = 1;
@@ -1474,7 +1456,7 @@ int read_index_from(struct index_state *istate, const char *path)
 	else
 		previous_name = NULL;
 
-	src_offset = sizeof(*hdr);
+	src_offset = sizeof(*hdr) + sizeof(*hdr_v2);
 	for (i = 0; i < istate->cache_nr; i++) {
 		struct ondisk_cache_entry *disk_ce;
 		struct cache_entry *ce;
@@ -1487,8 +1469,6 @@ int read_index_from(struct index_state *istate, const char *path)
 		src_offset += consumed;
 	}
 	strbuf_release(&previous_name_buf);
-	istate->timestamp.sec = st.st_mtime;
-	istate->timestamp.nsec = ST_MTIME_NSEC(st);
 
 	while (src_offset <= mmap_size - 20 - 8) {
 		/* After an array of active_nr index entries,
@@ -1508,6 +1488,58 @@ int read_index_from(struct index_state *istate, const char *path)
 		src_offset += 8;
 		src_offset += extsize;
 	}
+	return 0;
+unmap:
+	munmap(mmap, mmap_size);
+	die("index file corrupt");
+}
+
+/* remember to discard_cache() before reading a different cache! */
+int read_index_from(struct index_state *istate, const char *path)
+{
+	int fd;
+	struct stat st;
+	struct cache_version_header *hdr;
+	void *mmap;
+	size_t mmap_size;
+
+	errno = EBUSY;
+	if (istate->initialized)
+		return istate->cache_nr;
+
+	errno = ENOENT;
+	istate->timestamp.sec = 0;
+	istate->timestamp.nsec = 0;
+	fd = open(path, O_RDONLY);
+	if (fd < 0) {
+		if (errno == ENOENT)
+			return 0;
+		die_errno("index file open failed");
+	}
+
+	if (fstat(fd, &st))
+		die_errno("cannot stat the open index");
+
+	errno = EINVAL;
+	mmap_size = xsize_t(st.st_size);
+	if (mmap_size < sizeof(struct cache_header) + 20)
+		die("index file smaller than expected");
+
+	mmap = xmmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
+	close(fd);
+	if (mmap == MAP_FAILED)
+		die_errno("unable to map index file");
+
+	hdr = mmap;
+	if (verify_hdr_version(hdr, mmap_size) < 0)
+		goto unmap;
+
+	if (verify_hdr(mmap, mmap_size) < 0)
+		goto unmap;
+
+	read_index_v2(istate, mmap, mmap_size);
+	istate->timestamp.sec = st.st_mtime;
+	istate->timestamp.nsec = ST_MTIME_NSEC(st);
 	munmap(mmap, mmap_size);
 	return istate->cache_nr;
 
@@ -1771,10 +1803,11 @@ void update_index_if_able(struct index_state *istate, struct lock_file *lockfile
 		rollback_lock_file(lockfile);
 }
 
-int write_index(struct index_state *istate, int newfd)
+static int write_index_v2(struct index_state *istate, int newfd)
 {
 	git_SHA_CTX c;
-	struct cache_header hdr;
+	struct cache_version_header hdr;
+	struct cache_header hdr_v2;
 	int i, err, removed, extended, hdr_version;
 	struct cache_entry **cache = istate->cache;
 	int entries = istate->cache_nr;
@@ -1804,11 +1837,13 @@ int write_index(struct index_state *istate, int newfd)
 
 	hdr.hdr_signature = htonl(CACHE_SIGNATURE);
 	hdr.hdr_version = htonl(hdr_version);
-	hdr.hdr_entries = htonl(entries - removed);
+	hdr_v2.hdr_entries = htonl(entries - removed);
 
 	git_SHA1_Init(&c);
 	if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
 		return -1;
+	if (ce_write(&c, newfd, &hdr_v2, sizeof(hdr_v2)) < 0)
+		return -1;
 
 	previous_name = (hdr_version == 4) ? &previous_name_buf : NULL;
 	for (i = 0; i < entries; i++) {
@@ -1854,6 +1889,11 @@ int write_index(struct index_state *istate, int newfd)
 	return 0;
 }
 
+int write_index(struct index_state *istate, int newfd)
+{
+	return write_index_v2(istate, newfd);
+}
+
 /*
  * Read the index file that is potentially unmerged into given
  * index_state, dropping any unmerged entries.  Returns true if
diff --git a/test-index-version.c b/test-index-version.c
index 05d4699..4c0386f 100644
--- a/test-index-version.c
+++ b/test-index-version.c
@@ -2,7 +2,7 @@
 
 int main(int argc, char **argv)
 {
-	struct cache_header hdr;
+	struct cache_version_header hdr;
 	int version;
 
 	memset(&hdr,0,sizeof(hdr));

-- 
1.8.3.453.g1dfc63d
Previous: Thomas GummererNext: Thomas Gummerer
Message 3 of 51 in “Index-v5”
  1. 00/19 Index-v5Thomas Gummerer, Jul 12, 2013
  2. 01/19 t2104: Don't fail for index versions other than [23]Thomas Gummerer, Jul 12, 2013
  3. 02/19 read-cache: split index file version specific functionalityThomas Gummerer, Jul 12, 2013
  4. 03/19 read-cache: move index v2 specific functions to their own fileThomas Gummerer, Jul 12, 2013
  5. Duy NguyenJul 14, 2013
  6. Thomas GummererJul 19, 2013
  7. 04/19 read-cache: Re-read index if index file changedThomas Gummerer, Jul 12, 2013
  8. 05/19 Add documentation for the index apiThomas Gummerer, Jul 12, 2013
  9. 06/19 read-cache: add index reading apiThomas Gummerer, Jul 12, 2013
  10. Duy NguyenJul 14, 2013
  11. 07/19 make sure partially read index is not changedThomas Gummerer, Jul 12, 2013
  12. Duy NguyenJul 14, 2013
  13. Thomas GummererJul 17, 2013
  14. 08/19 grep.c: Use index apiThomas Gummerer, Jul 12, 2013
  15. Duy NguyenJul 14, 2013
  16. Thomas GummererJul 15, 2013
  17. 09/19 ls-files.c: use index apiThomas Gummerer, Jul 12, 2013
  18. Duy NguyenJul 14, 2013
  19. Thomas GummererJul 17, 2013
  20. 10/19 documentation: add documentation of the index-v5 file formatThomas Gummerer, Jul 12, 2013
  21. Duy NguyenJul 14, 2013
  22. Thomas GummererJul 17, 2013
  23. Duy NguyenAug 4, 2013
  24. Thomas GummererAug 4, 2013
  25. 11/19 read-cache: make in-memory format aware of stat_crcThomas Gummerer, Jul 12, 2013
  26. 12/19 read-cache: read index-v5Thomas Gummerer, Jul 12, 2013
  27. Duy NguyenJul 14, 2013
  28. Thomas GummererAug 7, 2013
  29. Duy NguyenJul 15, 2013
  30. Thomas GummererJul 17, 2013
  31. Duy NguyenAug 8, 2013
  32. Thomas GummererAug 8, 2013
  33. Thomas GummererAug 9, 2013
  34. Thomas GummererAug 7, 2013
  35. Duy NguyenAug 8, 2013
  36. 13/19 read-cache: read resolve-undo dataThomas Gummerer, Jul 12, 2013
  37. 14/19 read-cache: read cache-tree in index-v5Thomas Gummerer, Jul 12, 2013
  38. 15/19 read-cache: write index-v5Thomas Gummerer, Jul 12, 2013
  39. 16/19 read-cache: write index-v5 cache-tree dataThomas Gummerer, Jul 12, 2013
  40. 17/19 read-cache: write resolve-undo data for index-v5Thomas Gummerer, Jul 12, 2013
  41. 18/19 update-index.c: rewrite index when index-version is givenThomas Gummerer, Jul 12, 2013
  42. 19/19 p0003-index.sh: add perf test for the index formatsThomas Gummerer, Jul 12, 2013
  43. Duy NguyenJul 14, 2013
  44. Thomas GummererJul 15, 2013
  45. Duy NguyenJul 15, 2013
  46. Thomas GummererJul 17, 2013
  47. Junio C HamanoJul 17, 2013
  48. Thomas GummererJul 19, 2013
  49. Junio C HamanoJul 19, 2013
  50. Ramsay JonesJul 16, 2013
  51. Thomas GummererJul 17, 2013

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