Re: [PATCH 14/23] pack v4: object data copy
From: Junio C Hamano <hidden>
Date: 2016-06-15 22:58:31
Nicolas Pitre [off-list ref] writes:
Blob and tag objects have no particular changes except for their object header. Delta objects are also copied as is, except for their delta base reference which is converted to the new way as used elsewhere in pack v4 encoding i.e. an index into the SHA1 table or a literal SHA1 prefixed by 0 if not found in the table (see add_sha1_ref). This is true for both REF_DELTA as well as OFS_DELTA. Object payload is validated against the recorded CRC32 in the source pack index file when possible. Signed-off-by: Nicolas Pitre <nico@fluxnic.net> ---
The title somewhat confused me until I realized that this series is building a program that would convert existing data from a single pack into packv4 format, not a "pack-objects --pack-verison=4".
quoted hunk
packv4-create.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 66 insertions(+)diff --git a/packv4-create.c b/packv4-create.c index 6e0bb1d..a6dc818 100644 --- a/packv4-create.c +++ b/packv4-create.c@@ -12,6 +12,7 @@ #include "object.h" #include "tree-walk.h" #include "pack.h" +#include "pack-revindex.h" static int pack_compression_level = Z_DEFAULT_COMPRESSION;@@ -673,6 +674,71 @@ static unsigned int write_object_header(struct sha1file *f, enum object_type typ return end - buf; } +static unsigned long copy_object_data(struct sha1file *f, struct packed_git *p, + off_t offset) +{ + struct pack_window *w_curs = NULL; + struct revindex_entry *revidx; + enum object_type type; + unsigned long avail, size, datalen, written; + int hdrlen, idx_nr; + unsigned char *src, *end, buf[24]; + + revidx = find_pack_revindex(p, offset); + idx_nr = revidx->nr; + datalen = revidx[1].offset - offset; + + src = use_pack(p, &w_curs, offset, &avail); + hdrlen = unpack_object_header_buffer(src, avail, &type, &size); + + written = write_object_header(f, type, size); + + if (type == OBJ_OFS_DELTA) { + unsigned char c = src[hdrlen++]; + off_t base_offset = c & 127; + while (c & 128) { + base_offset += 1; + if (!base_offset || MSB(base_offset, 7)) + die("delta offset overflow"); + c = src[hdrlen++]; + base_offset = (base_offset << 7) + (c & 127); + } + base_offset = offset - base_offset; + if (base_offset <= 0 || base_offset >= offset) + die("delta offset out of bound"); + revidx = find_pack_revindex(p, base_offset); + end = add_sha1_ref(buf, nth_packed_object_sha1(p, revidx->nr)); + sha1write(f, buf, end - buf); + written += end - buf; + } else if (type == OBJ_REF_DELTA) { + end = add_sha1_ref(buf, src + hdrlen); + hdrlen += 20; + sha1write(f, buf, end - buf); + written += end - buf; + } + + if (p->index_version > 1 && + check_pack_crc(p, &w_curs, offset, datalen, idx_nr)) + die("bad CRC for object at offset %"PRIuMAX" in %s", + (uintmax_t)offset, p->pack_name); + + offset += hdrlen; + datalen -= hdrlen; + + while (datalen) { + src = use_pack(p, &w_curs, offset, &avail); + if (avail > datalen) + avail = datalen; + sha1write(f, src, avail); + written += avail; + offset += avail; + datalen -= avail; + } + unuse_pack(&w_curs); + + return written; +} + static struct packed_git *open_pack(const char *path) { char arg[PATH_MAX];