libarchive: add capability to unpack to mem.buffer

The performance and number of processes for a "depmod -a" with gzipped
modules was abysmal. This patch adds a code path without fork,
benefiting all users of xmalloc_open_zipped_read_close.

"modinfo radeon.ko.gz", a single-file reader, got 30% faster.
"depmod -a", which used to fork over 800 times, got 20% faster.

Heavily based on a patch by Lauri Kasanen <curaga@operamail.com>

function                                             old     new   delta
setup_transformer_on_fd                                -     159    +159
transformer_write                                      -     122    +122
fork_transformer                                       -     112    +112
xmalloc_open_zipped_read_close                        63     118     +55
read_bunzip                                         1866    1896     +30
xtransformer_write                                     -      19     +19
unzip_main                                          2449    2462     +13
bbunpack                                             755     766     +11
unpack_lzma_stream                                  2717    2723      +6
unpack_xz_stream                                    2393    2397      +4
unpack_Z_stream                                     1173    1175      +2
inflate_unzip                                        111     105      -6
check_signature16                                     70      63      -7
unpack_bz2_stream                                    359     349     -10
unpack_unxz                                           12       -     -12
unpack_unlzma                                         12       -     -12
unpack_uncompress                                     12       -     -12
unpack_gunzip                                         12       -     -12
unpack_bunzip2                                        12       -     -12
open_transformer                                     106      92     -14
inflate_unzip_internal                              1945    1916     -29
unpack_gz_stream                                     693     655     -38
open_zipped                                           89      47     -42
setup_unzip_on_fd                                    142      53     -89
------------------------------------------------------------------------------
(add/remove: 4/5 grow/shrink: 7/8 up/down: 533/-295)          Total: 238 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/archival/libarchive/decompress_unxz.c b/archival/libarchive/decompress_unxz.c
index 6df54e131..1f408abfd 100644
--- a/archival/libarchive/decompress_unxz.c
+++ b/archival/libarchive/decompress_unxz.c
@@ -38,7 +38,7 @@ static uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc)
 #include "unxz/xz_dec_stream.c"
 
 IF_DESKTOP(long long) int FAST_FUNC
-unpack_xz_stream(transformer_state_t *xstate, int src_fd, int dst_fd)
+unpack_xz_stream(transformer_state_t *xstate)
 {
 	enum xz_ret xz_result;
 	struct xz_buf iobuf;
@@ -67,7 +67,7 @@ unpack_xz_stream(transformer_state_t *xstate, int src_fd, int dst_fd)
 	xz_result = X_OK;
 	while (1) {
 		if (iobuf.in_pos == iobuf.in_size) {
-			int rd = safe_read(src_fd, membuf, BUFSIZ);
+			int rd = safe_read(xstate->src_fd, membuf, BUFSIZ);
 			if (rd < 0) {
 				bb_error_msg(bb_msg_read_error);
 				total = -1;
@@ -104,7 +104,7 @@ unpack_xz_stream(transformer_state_t *xstate, int src_fd, int dst_fd)
 //		bb_error_msg("<in pos:%d size:%d out pos:%d size:%d r:%d",
 //				iobuf.in_pos, iobuf.in_size, iobuf.out_pos, iobuf.out_size, xz_result);
 		if (iobuf.out_pos) {
-			xwrite(dst_fd, iobuf.out, iobuf.out_pos);
+			xtransformer_write(xstate, iobuf.out, iobuf.out_pos);
 			IF_DESKTOP(total += iobuf.out_pos;)
 			iobuf.out_pos = 0;
 		}