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libarchive: treat one "FIXME: avoid seek"

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function                                             old     new   delta
xmalloc_read_with_initial_buf                          -     205    +205
setup_transformer_on_fd                              154     150      -4
xmalloc_open_zipped_read_close                       143     135      -8
xmalloc_read                                         201      10    -191
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/3 up/down: 205/-203)            Total: 2 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
2019-05-24 17:03:28 +02:00
parent 309f5e3775
commit dff2bd733f
4 changed files with 41 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

44
archival/libarchive/open_transformer.c
View File

@@ -159,47 +159,44 @@ void FAST_FUNC fork_transformer(int fd, const char *transform_prog)
*/
static transformer_state_t *setup_transformer_on_fd(int fd, int fail_if_not_compressed)
{
union {
uint8_t b[4];
uint16_t b16[2];
uint32_t b32[1];
} magic;
transformer_state_t *xstate;
xstate = xzalloc(sizeof(*xstate));
xstate->src_fd = fd;
xstate->signature_skipped = 2;
/* .gz and .bz2 both have 2-byte signature, and their
* unpack_XXX_stream wants this header skipped. */
xread(fd, magic.b16, sizeof(magic.b16[0]));
xstate->signature_skipped = 2;
xread(fd, xstate->magic.b16, 2);
if (ENABLE_FEATURE_SEAMLESS_GZ
&& magic.b16[0] == GZIP_MAGIC
&& xstate->magic.b16[0] == GZIP_MAGIC
) {
xstate->xformer = unpack_gz_stream;
USE_FOR_NOMMU(xstate->xformer_prog = "gunzip";)
goto found_magic;
}
if (ENABLE_FEATURE_SEAMLESS_Z
&& magic.b16[0] == COMPRESS_MAGIC
&& xstate->magic.b16[0] == COMPRESS_MAGIC
) {
xstate->xformer = unpack_Z_stream;
USE_FOR_NOMMU(xstate->xformer_prog = "uncompress";)
goto found_magic;
}
if (ENABLE_FEATURE_SEAMLESS_BZ2
&& magic.b16[0] == BZIP2_MAGIC
&& xstate->magic.b16[0] == BZIP2_MAGIC
) {
xstate->xformer = unpack_bz2_stream;
USE_FOR_NOMMU(xstate->xformer_prog = "bunzip2";)
goto found_magic;
}
if (ENABLE_FEATURE_SEAMLESS_XZ
&& magic.b16[0] == XZ_MAGIC1
&& xstate->magic.b16[0] == XZ_MAGIC1
) {
uint32_t v32;
xstate->signature_skipped = 6;
xread(fd, magic.b32, sizeof(magic.b32[0]));
if (magic.b32[0] == XZ_MAGIC2) {
xread(fd, &xstate->magic.b16[1], 4);
move_from_unaligned32(v32, &xstate->magic.b16[1]);
if (v32 == XZ_MAGIC2) {
xstate->xformer = unpack_xz_stream;
USE_FOR_NOMMU(xstate->xformer_prog = "unxz";)
goto found_magic;
@@ -344,11 +341,24 @@ void* FAST_FUNC xmalloc_open_zipped_read_close(const char *fname, size_t *maxsz_
*maxsz_p = xstate->mem_output_size;
}
} else {
/* File is not compressed */
//FIXME: avoid seek
xlseek(xstate->src_fd, - xstate->signature_skipped, SEEK_CUR);
/* File is not compressed.
* We already read first few bytes, account for that.
* Exmaple where it happens:
* "modinfo MODULE.ko" (not compressed)
* open("MODULE.ko", O_RDONLY|O_LARGEFILE) = 4
* read(4, "\177E", 2) = 2
* fstat64(4, ...)
* mmap(...)
* read(4, "LF\2\1\1\0\0\0\0"...
* ...and we avoided seeking on the fd! :)
*/
xstate->signature_skipped = 0;
image = xmalloc_read(xstate->src_fd, maxsz_p);
image = xmalloc_read_with_initial_buf(
xstate->src_fd,
maxsz_p,
xmemdup(&xstate->magic, xstate->signature_skipped),
xstate->signature_skipped
);
}
if (!image)