Han Xin <chiyutianyi@xxxxxxxxx> writes:
> From: Han Xin <hanxin.hx@xxxxxxxxxxxxxxx>
>
> We used to call "get_data()" in "unpack_non_delta_entry()" to read the
> entire contents of a blob object, no matter how big it is. This
> implementation may consume all the memory and cause OOM.
>
> This can be improved by feeding data to "write_loose_object()" in a
> stream. The input stream is implemented as an interface. In the first
> step, we make a simple implementation, feeding the entire buffer in the
> "stream" to "write_loose_object()" as a refactor.
Possibly a stupid question (not a review).
How does this compare with "struct git_istream" implemented for a
few existing codepaths? It seems that the existing users are
pack-objects, index-pack and archive and all of them use the
interface to obtain data given an object name without having to grab
everything in core at once.
If we are adding a new streaming interface to go in the opposite
direction, i.e. from the working tree data to object store, I would
understand it as a complementary interface (but then I suspect there
is a half of it already in bulk-checkin API), but I am not sure how
this new thing fits in the larger picture.
> Helped-by: Jiang Xin <zhiyou.jx@xxxxxxxxxxxxxxx>
> Signed-off-by: Han Xin <hanxin.hx@xxxxxxxxxxxxxxx>
> ---
> object-file.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++----
> object-store.h | 5 +++++
> 2 files changed, 51 insertions(+), 4 deletions(-)
>
> diff --git a/object-file.c b/object-file.c
> index c3d866a287..227f53a0de 100644
> --- a/object-file.c
> +++ b/object-file.c
> @@ -1860,8 +1860,26 @@ static int create_tmpfile(struct strbuf *tmp, const char *filename)
> return fd;
> }
>
> +struct simple_input_stream_data {
> + const void *buf;
> + unsigned long len;
> +};
> +
> +static const void *feed_simple_input_stream(struct input_stream *in_stream, unsigned long *len)
> +{
> + struct simple_input_stream_data *data = in_stream->data;
> +
> + if (data->len == 0) {
> + *len = 0;
> + return NULL;
> + }
> + *len = data->len;
> + data->len = 0;
> + return data->buf;
> +}
> +
> static int write_loose_object(const struct object_id *oid, char *hdr,
> - int hdrlen, const void *buf, unsigned long len,
> + int hdrlen, struct input_stream *in_stream,
> time_t mtime, unsigned flags)
> {
> int fd, ret;
> @@ -1871,6 +1889,8 @@ static int write_loose_object(const struct object_id *oid, char *hdr,
> struct object_id parano_oid;
> static struct strbuf tmp_file = STRBUF_INIT;
> static struct strbuf filename = STRBUF_INIT;
> + const void *buf;
> + unsigned long len;
>
> loose_object_path(the_repository, &filename, oid);
>
> @@ -1898,6 +1918,7 @@ static int write_loose_object(const struct object_id *oid, char *hdr,
> the_hash_algo->update_fn(&c, hdr, hdrlen);
>
> /* Then the data itself.. */
> + buf = in_stream->read(in_stream, &len);
> stream.next_in = (void *)buf;
> stream.avail_in = len;
> do {
> @@ -1960,6 +1981,13 @@ int write_object_file_flags(const void *buf, unsigned long len,
> {
> char hdr[MAX_HEADER_LEN];
> int hdrlen = sizeof(hdr);
> + struct input_stream in_stream = {
> + .read = feed_simple_input_stream,
> + .data = (void *)&(struct simple_input_stream_data) {
> + .buf = buf,
> + .len = len,
> + },
> + };
>
> /* Normally if we have it in the pack then we do not bother writing
> * it out into .git/objects/??/?{38} file.
> @@ -1968,7 +1996,7 @@ int write_object_file_flags(const void *buf, unsigned long len,
> &hdrlen);
> if (freshen_packed_object(oid) || freshen_loose_object(oid))
> return 0;
> - return write_loose_object(oid, hdr, hdrlen, buf, len, 0, flags);
> + return write_loose_object(oid, hdr, hdrlen, &in_stream, 0, flags);
> }
>
> int hash_object_file_literally(const void *buf, unsigned long len,
> @@ -1977,6 +2005,13 @@ int hash_object_file_literally(const void *buf, unsigned long len,
> {
> char *header;
> int hdrlen, status = 0;
> + struct input_stream in_stream = {
> + .read = feed_simple_input_stream,
> + .data = (void *)&(struct simple_input_stream_data) {
> + .buf = buf,
> + .len = len,
> + },
> + };
>
> /* type string, SP, %lu of the length plus NUL must fit this */
> hdrlen = strlen(type) + MAX_HEADER_LEN;
> @@ -1988,7 +2023,7 @@ int hash_object_file_literally(const void *buf, unsigned long len,
> goto cleanup;
> if (freshen_packed_object(oid) || freshen_loose_object(oid))
> goto cleanup;
> - status = write_loose_object(oid, header, hdrlen, buf, len, 0, 0);
> + status = write_loose_object(oid, header, hdrlen, &in_stream, 0, 0);
>
> cleanup:
> free(header);
> @@ -2003,14 +2038,21 @@ int force_object_loose(const struct object_id *oid, time_t mtime)
> char hdr[MAX_HEADER_LEN];
> int hdrlen;
> int ret;
> + struct simple_input_stream_data data;
> + struct input_stream in_stream = {
> + .read = feed_simple_input_stream,
> + .data = &data,
> + };
>
> if (has_loose_object(oid))
> return 0;
> buf = read_object(the_repository, oid, &type, &len);
> if (!buf)
> return error(_("cannot read object for %s"), oid_to_hex(oid));
> + data.buf = buf;
> + data.len = len;
> hdrlen = xsnprintf(hdr, sizeof(hdr), "%s %"PRIuMAX , type_name(type), (uintmax_t)len) + 1;
> - ret = write_loose_object(oid, hdr, hdrlen, buf, len, mtime, 0);
> + ret = write_loose_object(oid, hdr, hdrlen, &in_stream, mtime, 0);
> free(buf);
>
> return ret;
> diff --git a/object-store.h b/object-store.h
> index 952efb6a4b..ccc1fc9c1a 100644
> --- a/object-store.h
> +++ b/object-store.h
> @@ -34,6 +34,11 @@ struct object_directory {
> char *path;
> };
>
> +struct input_stream {
> + const void *(*read)(struct input_stream *, unsigned long *len);
> + void *data;
> +};
> +
> KHASH_INIT(odb_path_map, const char * /* key: odb_path */,
> struct object_directory *, 1, fspathhash, fspatheq)
