--- /dev/null
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file memcmplen.h
+/// \brief Optimized comparison of two buffers
+//
+// Author: Lasse Collin
+//
+// This file has been put into the public domain.
+// You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef LZMA_MEMCMPLEN_H
+#define LZMA_MEMCMPLEN_H
+
+#include "common.h"
+
+#ifdef HAVE_IMMINTRIN_H
+# include <immintrin.h>
+#endif
+
+
+/// Find out how many equal bytes the two buffers have.
+///
+/// \param buf1 First buffer
+/// \param buf2 Second buffer
+/// \param len How many bytes have already been compared and will
+/// be assumed to match
+/// \param limit How many bytes to compare at most, including the
+/// already-compared bytes. This must be significantly
+/// smaller than UINT32_MAX to avoid integer overflows.
+/// Up to LZMA_MEMCMPLEN_EXTRA bytes may be read past
+/// the specified limit from both buf1 and buf2.
+///
+/// \return Number of equal bytes in the buffers is returned.
+/// This is always at least len and at most limit.
+///
+/// \note LZMA_MEMCMPLEN_EXTRA defines how many extra bytes may be read.
+/// It's rounded up to 2^n. This extra amount needs to be
+/// allocated in the buffers being used. It needs to be
+/// initialized too to keep Valgrind quiet.
+static inline uint32_t lzma_attribute((__always_inline__))
+lzma_memcmplen(const uint8_t *buf1, const uint8_t *buf2,
+ uint32_t len, uint32_t limit)
+{
+ assert(len <= limit);
+ assert(limit <= UINT32_MAX / 2);
+
+#if defined(TUKLIB_FAST_UNALIGNED_ACCESS) \
+ && ((TUKLIB_GNUC_REQ(3, 4) && defined(__x86_64__)) \
+ || (defined(__INTEL_COMPILER) && defined(__x86_64__)) \
+ || (defined(__INTEL_COMPILER) && defined(_M_X64)) \
+ || (defined(_MSC_VER) && defined(_M_X64)))
+ // NOTE: This will use 64-bit unaligned access which
+ // TUKLIB_FAST_UNALIGNED_ACCESS wasn't meant to permit, but
+ // it's convenient here at least as long as it's x86-64 only.
+ //
+ // I keep this x86-64 only for now since that's where I know this
+ // to be a good method. This may be fine on other 64-bit CPUs too.
+ // On big endian one should use xor instead of subtraction and switch
+ // to __builtin_clzll().
+#define LZMA_MEMCMPLEN_EXTRA 8
+ while (len < limit) {
+ const uint64_t x = *(const uint64_t *)(buf1 + len)
+ - *(const uint64_t *)(buf2 + len);
+ if (x != 0) {
+# if defined(_M_X64) // MSVC or Intel C compiler on Windows
+ unsigned long tmp;
+ _BitScanForward64(&tmp, x);
+ len += (uint32_t)tmp >> 3;
+# else // GCC, clang, or Intel C compiler
+ len += (uint32_t)__builtin_ctzll(x) >> 3;
+# endif
+ return my_min(len, limit);
+ }
+
+ len += 8;
+ }
+
+ return limit;
+
+#elif defined(TUKLIB_FAST_UNALIGNED_ACCESS) \
+ && defined(HAVE__MM_MOVEMASK_EPI8) \
+ && ((defined(__GNUC__) && defined(__SSE2_MATH__)) \
+ || (defined(__INTEL_COMPILER) && defined(__SSE2__)) \
+ || (defined(_MSC_VER) && defined(_M_IX86_FP) \
+ && _M_IX86_FP >= 2))
+ // NOTE: Like above, this will use 128-bit unaligned access which
+ // TUKLIB_FAST_UNALIGNED_ACCESS wasn't meant to permit.
+ //
+ // SSE2 version for 32-bit and 64-bit x86. On x86-64 the above
+ // version is sometimes significantly faster and sometimes
+ // slightly slower than this SSE2 version, so this SSE2
+ // version isn't used on x86-64.
+# define LZMA_MEMCMPLEN_EXTRA 16
+ while (len < limit) {
+ const uint32_t x = 0xFFFF ^ _mm_movemask_epi8(_mm_cmpeq_epi8(
+ _mm_loadu_si128((const __m128i *)(buf1 + len)),
+ _mm_loadu_si128((const __m128i *)(buf2 + len))));
+
+ if (x != 0) {
+# if defined(__INTEL_COMPILER)
+ len += _bit_scan_forward(x);
+# elif defined(_MSC_VER)
+ unsigned long tmp;
+ _BitScanForward(&tmp, x);
+ len += tmp;
+# else
+ len += __builtin_ctz(x);
+# endif
+ return my_min(len, limit);
+ }
+
+ len += 16;
+ }
+
+ return limit;
+
+#elif defined(TUKLIB_FAST_UNALIGNED_ACCESS) && !defined(WORDS_BIGENDIAN)
+ // Generic 32-bit little endian method
+# define LZMA_MEMCMPLEN_EXTRA 4
+ while (len < limit) {
+ uint32_t x = *(const uint32_t *)(buf1 + len)
+ - *(const uint32_t *)(buf2 + len);
+ if (x != 0) {
+ if ((x & 0xFFFF) == 0) {
+ len += 2;
+ x >>= 16;
+ }
+
+ if ((x & 0xFF) == 0)
+ ++len;
+
+ return my_min(len, limit);
+ }
+
+ len += 4;
+ }
+
+ return limit;
+
+#elif defined(TUKLIB_FAST_UNALIGNED_ACCESS) && defined(WORDS_BIGENDIAN)
+ // Generic 32-bit big endian method
+# define LZMA_MEMCMPLEN_EXTRA 4
+ while (len < limit) {
+ uint32_t x = *(const uint32_t *)(buf1 + len)
+ ^ *(const uint32_t *)(buf2 + len);
+ if (x != 0) {
+ if ((x & 0xFFFF0000) == 0) {
+ len += 2;
+ x <<= 16;
+ }
+
+ if ((x & 0xFF000000) == 0)
+ ++len;
+
+ return my_min(len, limit);
+ }
+
+ len += 4;
+ }
+
+ return limit;
+
+#else
+ // Simple portable version that doesn't use unaligned access.
+# define LZMA_MEMCMPLEN_EXTRA 0
+ while (len < limit && buf1[len] == buf2[len])
+ ++len;
+
+ return len;
+#endif
+}
+
+#endif
projects / zpackage / blobdiff