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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
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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)

6
include/bb_archive.h
View File

@ -235,6 +235,12 @@ typedef struct transformer_state_t {
off_t bytes_in; /* used in unzip code only: needs to know packed size */
uint32_t crc32;
time_t mtime; /* gunzip code may set this on exit */
union { /* if we read magic, it's saved here */
uint8_t b[8];
uint16_t b16[4];
uint32_t b32[2];
} magic;
} transformer_state_t;
void init_transformer_state(transformer_state_t *xstate) FAST_FUNC;

1
include/libbb.h
View File

@ -881,6 +881,7 @@ extern ssize_t open_read_close(const char *filename, void *buf, size_t maxsz) FA
extern char *xmalloc_reads(int fd, size_t *maxsz_p) FAST_FUNC;
/* Reads block up to *maxsz_p (default: INT_MAX - 4095) */
extern void *xmalloc_read(int fd, size_t *maxsz_p) FAST_FUNC RETURNS_MALLOC;
extern void *xmalloc_read_with_initial_buf(int fd, size_t *maxsz_p, char *buf, size_t total) FAST_FUNC;
/* Returns NULL if file can't be opened (default max size: INT_MAX - 4095) */
extern void *xmalloc_open_read_close(const char *filename, size_t *maxsz_p) FAST_FUNC RETURNS_MALLOC;
/* Never returns NULL */

12
libbb/read_printf.c
View File

@ -102,10 +102,9 @@ char* FAST_FUNC xmalloc_reads(int fd, size_t *maxsz_p)
// Read (potentially big) files in one go. File size is estimated
// by stat. Extra '\0' byte is appended.
void* FAST_FUNC xmalloc_read(int fd, size_t *maxsz_p)
void* FAST_FUNC xmalloc_read_with_initial_buf(int fd, size_t *maxsz_p, char *buf, size_t total)
{
char *buf;
size_t size, rd_size, total;
size_t size, rd_size;
size_t to_read;
struct stat st;
@ -118,8 +117,6 @@ void* FAST_FUNC xmalloc_read(int fd, size_t *maxsz_p)
/* In order to make such files readable, we add small const */
size = (st.st_size | 0x3ff) + 1;
total = 0;
buf = NULL;
while (1) {
if (to_read < size)
size = to_read;
@ -148,6 +145,11 @@ void* FAST_FUNC xmalloc_read(int fd, size_t *maxsz_p)
return buf;
}
void* FAST_FUNC xmalloc_read(int fd, size_t *maxsz_p)
{
return xmalloc_read_with_initial_buf(fd, maxsz_p, NULL, 0);
}
#ifdef USING_LSEEK_TO_GET_SIZE
/* Alternatively, file size can be obtained by lseek to the end.
* The code is slightly bigger. Retained in case fstat approach