Remove lzma_init() and other init functions from liblzma API.

Half of developers were already forgetting to use these
functions, which could have caused total breakage in some future
liblzma version or even now if --enable-small was used. Now
liblzma uses pthread_once() to do the initializations unless
it has been built with --disable-threads which make these
initializations thread-unsafe.

When --enable-small isn't used, liblzma currently gets needlessly
linked against libpthread (on systems that have it). While it is
stupid for now, liblzma will need threads in future anyway, so
this stupidity will be temporary only.

When --enable-small is used, different code CRC32 and CRC64 is
now used than without --enable-small. This made the resulting
binary slightly smaller, but the main reason was to clean it up
and to handle the lack of lzma_init_check().

The pkg-config file lzma.pc was renamed to liblzma.pc. I'm not
sure if it works correctly and portably for static linking
(Libs.private includes -pthread or other operating system
specific flags). Hopefully someone complains if it is bad.

lzma_rc_prices[] is now included as a precomputed array even
with --enable-small. It's just 128 bytes now that it uses uint8_t
instead of uint32_t. Smaller array seemed to be at least as fast
as the more bloated uint32_t array on x86; hopefully it's not bad
on other architectures.

1 files changed, 88 insertions, 0 deletions

diff --git a/src/liblzma/check/crc32_fast.c b/src/liblzma/check/crc32_fast.c
new file mode 100644
index 00000000..698cf768
--- /dev/null
+++ b/src/liblzma/check/crc32_fast.c
@@ -0,0 +1,88 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       crc32.c
+/// \brief      CRC32 calculation
+//
+//  This code has been put into the public domain.
+//
+//  This library is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "check.h"
+#include "crc_macros.h"
+
+
+// If you make any changes, do some bench marking! Seemingly unrelated
+// changes can very easily ruin the performance (and very probably is
+// very compiler dependent).
+extern LZMA_API uint32_t
+lzma_crc32(const uint8_t *buf, size_t size, uint32_t crc)
+{
+	crc = ~crc;
+
+#ifdef WORDS_BIGENDIAN
+	crc = bswap_32(crc);
+#endif
+
+	if (size > 8) {
+		// Fix the alignment, if needed. The if statement above
+		// ensures that this won't read past the end of buf[].
+		while ((uintptr_t)(buf) & 7) {
+			crc = lzma_crc32_table[0][*buf++ ^ A(crc)] ^ S8(crc);
+			--size;
+		}
+
+		// Calculate the position where to stop.
+		const uint8_t *const limit = buf + (size & ~(size_t)(7));
+
+		// Calculate how many bytes must be calculated separately
+		// before returning the result.
+		size &= (size_t)(7);
+
+		// Calculate the CRC32 using the slice-by-eight algorithm.
+		// It is explained in this document:
+		// http://www.intel.com/technology/comms/perfnet/download/CRC_generators.pdf
+		//
+		// The code below is different than the code in Intel's
+		// paper, but the principle is identical. This should be
+		// faster with GCC than Intel's code. This is tested only
+		// with GCC 3.4.6 and 4.1.2 on x86, so your results may vary.
+		//
+		// Using -Os and -fomit-frame-pointer seem to give the best
+		// results at least with GCC 4.1.2 on x86. It's sill far
+		// from the speed of hand-optimized assembler.
+		while (buf < limit) {
+			crc ^= *(uint32_t *)(buf);
+			buf += 4;
+
+			crc = lzma_crc32_table[7][A(crc)]
+			    ^ lzma_crc32_table[6][B(crc)]
+			    ^ lzma_crc32_table[5][C(crc)]
+			    ^ lzma_crc32_table[4][D(crc)];
+
+			const uint32_t tmp = *(uint32_t *)(buf);
+			buf += 4;
+
+			// It is critical for performance, that
+			// the crc variable is XORed between the
+			// two table-lookup pairs.
+			crc = lzma_crc32_table[3][A(tmp)]
+			    ^ lzma_crc32_table[2][B(tmp)]
+			    ^ crc
+			    ^ lzma_crc32_table[1][C(tmp)]
+			    ^ lzma_crc32_table[0][D(tmp)];
+		}
+	}
+
+	while (size-- != 0)
+		crc = lzma_crc32_table[0][*buf++ ^ A(crc)] ^ S8(crc);
+
+#ifdef WORDS_BIGENDIAN
+	crc = bswap_32(crc);
+#endif
+
+	return ~crc;
+}