It is useful to be able to rewind a check-summed file to a certain
previous state after writing data into it using sha1write() API. The
fast-import command does this after streaming a blob data to the packfile
being generated and then noticing that the same blob has already been
written, and it does this with a private code truncate_pack() that is
commented as "Yes, this is a layering violation".
Introduce two API functions, sha1file_checkpoint(), that allows the caller
to save a state of a sha1file, and then later revert it to the saved state.
Use it to reimplement truncate_pack().
Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx>
---
* An extremely low-prio clean-up during the pre-release freeze period,
but this is necessary to advance the jc/stream-to-pack topic forward.
csum-file.c | 20 ++++++++++++++++++++
csum-file.h | 9 +++++++++
fast-import.c | 25 ++++++++-----------------
3 files changed, 37 insertions(+), 17 deletions(-)
diff --git a/csum-file.c b/csum-file.c
index fc97d6e..53f5375 100644
--- a/csum-file.c
+++ b/csum-file.c
@@ -158,6 +158,26 @@ struct sha1file *sha1fd_throughput(int fd, const char *name, struct progress *tp
return f;
}
+void sha1file_checkpoint(struct sha1file *f, struct sha1file_checkpoint *checkpoint)
+{
+ sha1flush(f);
+ checkpoint->offset = f->total;
+ checkpoint->ctx = f->ctx;
+}
+
+int sha1file_truncate(struct sha1file *f, struct sha1file_checkpoint *checkpoint)
+{
+ off_t offset = checkpoint->offset;
+
+ if (ftruncate(f->fd, offset) ||
+ lseek(f->fd, offset, SEEK_SET) != offset)
+ return -1;
+ f->total = offset;
+ f->ctx = checkpoint->ctx;
+ f->offset = 0; /* sha1flush() was called in checkpoint */
+ return 0;
+}
+
void crc32_begin(struct sha1file *f)
{
f->crc32 = crc32(0, NULL, 0);
diff --git a/csum-file.h b/csum-file.h
index 6a7967c..3b540bd 100644
--- a/csum-file.h
+++ b/csum-file.h
@@ -17,6 +17,15 @@ struct sha1file {
unsigned char buffer[8192];
};
+/* Checkpoint */
+struct sha1file_checkpoint {
+ off_t offset;
+ git_SHA_CTX ctx;
+};
+
+extern void sha1file_checkpoint(struct sha1file *, struct sha1file_checkpoint *);
+extern int sha1file_truncate(struct sha1file *, struct sha1file_checkpoint *);
+
/* sha1close flags */
#define CSUM_CLOSE 1
#define CSUM_FSYNC 2
diff --git a/fast-import.c b/fast-import.c
index 8d8ea3c..a8db41b 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -1143,17 +1143,11 @@ static int store_object(
return 0;
}
-static void truncate_pack(off_t to, git_SHA_CTX *ctx)
+static void truncate_pack(struct sha1file_checkpoint *checkpoint)
{
- if (ftruncate(pack_data->pack_fd, to)
- || lseek(pack_data->pack_fd, to, SEEK_SET) != to)
+ if (sha1file_truncate(pack_file, checkpoint))
die_errno("cannot truncate pack to skip duplicate");
- pack_size = to;
-
- /* yes this is a layering violation */
- pack_file->total = to;
- pack_file->offset = 0;
- pack_file->ctx = *ctx;
+ pack_size = checkpoint->offset;
}
static void stream_blob(uintmax_t len, unsigned char *sha1out, uintmax_t mark)
@@ -1166,8 +1160,8 @@ static void stream_blob(uintmax_t len, unsigned char *sha1out, uintmax_t mark)
unsigned long hdrlen;
off_t offset;
git_SHA_CTX c;
- git_SHA_CTX pack_file_ctx;
git_zstream s;
+ struct sha1file_checkpoint checkpoint;
int status = Z_OK;
/* Determine if we should auto-checkpoint. */
@@ -1175,11 +1169,8 @@ static void stream_blob(uintmax_t len, unsigned char *sha1out, uintmax_t mark)
|| (pack_size + 60 + len) < pack_size)
cycle_packfile();
- offset = pack_size;
-
- /* preserve the pack_file SHA1 ctx in case we have to truncate later */
- sha1flush(pack_file);
- pack_file_ctx = pack_file->ctx;
+ sha1file_checkpoint(pack_file, &checkpoint);
+ offset = checkpoint.offset;
hdrlen = snprintf((char *)out_buf, out_sz, "blob %" PRIuMAX, len) + 1;
if (out_sz <= hdrlen)
@@ -1245,14 +1236,14 @@ static void stream_blob(uintmax_t len, unsigned char *sha1out, uintmax_t mark)
if (e->idx.offset) {
duplicate_count_by_type[OBJ_BLOB]++;
- truncate_pack(offset, &pack_file_ctx);
+ truncate_pack(&checkpoint);
} else if (find_sha1_pack(sha1, packed_git)) {
e->type = OBJ_BLOB;
e->pack_id = MAX_PACK_ID;
e->idx.offset = 1; /* just not zero! */
duplicate_count_by_type[OBJ_BLOB]++;
- truncate_pack(offset, &pack_file_ctx);
+ truncate_pack(&checkpoint);
} else {
e->depth = 0;
--
1.7.8.rc3.111.g7d421
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