This is an automated email from the ASF dual-hosted git repository. ronny pushed a commit to branch update-snappy in repository https://gitbox.apache.org/repos/asf/couchdb-snappy.git
commit 05c004c8c6394ee8cb7173fec257868ce0f14133 Author: Peter Membrey <[email protected]> AuthorDate: Fri Nov 15 18:11:31 2013 +0800 Updating to snappy 1.1.1 --- c_src/snappy/NEWS | 71 +++++ c_src/snappy/README | 4 +- c_src/snappy/snappy-internal.h | 4 +- c_src/snappy/snappy-sinksource.cc | 1 - c_src/snappy/snappy-sinksource.h | 1 + c_src/snappy/snappy-stubs-internal.h | 188 +++++++------ c_src/snappy/snappy-stubs-public.h | 20 +- c_src/snappy/snappy.cc | 505 +++++++++++++++++++++++++++-------- c_src/snappy/snappy.h | 51 +++- c_src/snappy_nif.cc | 12 +- rebar.config | 2 +- 11 files changed, 638 insertions(+), 221 deletions(-) diff --git a/c_src/snappy/NEWS b/c_src/snappy/NEWS index d514787..f21e9d0 100644 --- a/c_src/snappy/NEWS +++ b/c_src/snappy/NEWS @@ -1,3 +1,74 @@ +Snappy v1.1.1, October 15th 2013: + + * Add support for uncompressing to iovecs (scatter I/O). + The bulk of this patch was contributed by Mohit Aron. + + * Speed up decompression by ~2%; much more so (~13-20%) on + a few benchmarks on given compilers and CPUs. + + * Fix a few issues with MSVC compilation. + + * Support truncated test data in the benchmark. + + +Snappy v1.1.0, January 18th 2013: + + * Snappy now uses 64 kB block size instead of 32 kB. On average, + this means it compresses about 3% denser (more so for some + inputs), at the same or better speeds. + + * libsnappy no longer depends on iostream. + + * Some small performance improvements in compression on x86 + (0.5–1%). + + * Various portability fixes for ARM-based platforms, for MSVC, + and for GNU/Hurd. + + +Snappy v1.0.5, February 24th 2012: + + * More speed improvements. Exactly how big will depend on + the architecture: + + - 3–10% faster decompression for the base case (x86-64). + + - ARMv7 and higher can now use unaligned accesses, + and will see about 30% faster decompression and + 20–40% faster compression. + + - 32-bit platforms (ARM and 32-bit x86) will see 2–5% + faster compression. + + These are all cumulative (e.g., ARM gets all three speedups). + + * Fixed an issue where the unit test would crash on system + with less than 256 MB address space available, + e.g. some embedded platforms. + + * Added a framing format description, for use over e.g. HTTP, + or for a command-line compressor. We do not have any + implementations of this at the current point, but there seems + to be enough of a general interest in the topic. + Also make the format description slightly clearer. + + * Remove some compile-time warnings in -Wall + (mostly signed/unsigned comparisons), for easier embedding + into projects that use -Wall -Werror. + + +Snappy v1.0.4, September 15th 2011: + + * Speeded up the decompressor somewhat; typically about 2–8% + for Core i7, in 64-bit mode (comparable for Opteron). + Somewhat more for some tests, almost no gain for others. + + * Make Snappy compile on certain platforms it didn't before + (Solaris with SunPro C++, HP-UX, AIX). + + * Correct some minor errors in the format description. + + Snappy v1.0.3, June 2nd 2011: * Speeded up the decompressor somewhat; about 3-6% for Core 2, diff --git a/c_src/snappy/README b/c_src/snappy/README index df8f0e1..3bc8888 100644 --- a/c_src/snappy/README +++ b/c_src/snappy/README @@ -76,11 +76,11 @@ your calling file, and link against the compiled library. There are many ways to call Snappy, but the simplest possible is - snappy::Compress(input, &output); + snappy::Compress(input.data(), input.size(), &output); and similarly - snappy::Uncompress(input, &output); + snappy::Uncompress(input.data(), input.size(), &output); where "input" and "output" are both instances of std::string. diff --git a/c_src/snappy/snappy-internal.h b/c_src/snappy/snappy-internal.h index a32eda5..c99d331 100644 --- a/c_src/snappy/snappy-internal.h +++ b/c_src/snappy/snappy-internal.h @@ -85,7 +85,7 @@ char* CompressFragment(const char* input, static inline int FindMatchLength(const char* s1, const char* s2, const char* s2_limit) { - DCHECK_GE(s2_limit, s2); + assert(s2_limit >= s2); int matched = 0; // Find out how long the match is. We loop over the data 64 bits at a @@ -122,7 +122,7 @@ static inline int FindMatchLength(const char* s1, const char* s2, const char* s2_limit) { // Implementation based on the x86-64 version, above. - DCHECK_GE(s2_limit, s2); + assert(s2_limit >= s2); int matched = 0; while (s2 <= s2_limit - 4 && diff --git a/c_src/snappy/snappy-sinksource.cc b/c_src/snappy/snappy-sinksource.cc index 1017895..5844552 100644 --- a/c_src/snappy/snappy-sinksource.cc +++ b/c_src/snappy/snappy-sinksource.cc @@ -68,5 +68,4 @@ char* UncheckedByteArraySink::GetAppendBuffer(size_t len, char* scratch) { return dest_; } - } diff --git a/c_src/snappy/snappy-sinksource.h b/c_src/snappy/snappy-sinksource.h index 430baea..faabfa1 100644 --- a/c_src/snappy/snappy-sinksource.h +++ b/c_src/snappy/snappy-sinksource.h @@ -60,6 +60,7 @@ class Sink { // The default implementation always returns the scratch buffer. virtual char* GetAppendBuffer(size_t length, char* scratch); + private: // No copying Sink(const Sink&); diff --git a/c_src/snappy/snappy-stubs-internal.h b/c_src/snappy/snappy-stubs-internal.h index 46ee235..12393b6 100644 --- a/c_src/snappy/snappy-stubs-internal.h +++ b/c_src/snappy/snappy-stubs-internal.h @@ -35,14 +35,13 @@ #include "config.h" #endif -#include <iostream> #include <string> #include <assert.h> #include <stdlib.h> #include <string.h> -#ifdef HAVE_SYS_MMAN +#ifdef HAVE_SYS_MMAN_H #include <sys/mman.h> #endif @@ -86,99 +85,19 @@ using namespace std; // version (anyone who wants to regenerate it can just do the call // themselves within main()). #define DEFINE_bool(flag_name, default_value, description) \ - bool FLAGS_ ## flag_name = default_value; + bool FLAGS_ ## flag_name = default_value #define DECLARE_bool(flag_name) \ - extern bool FLAGS_ ## flag_name; -#define REGISTER_MODULE_INITIALIZER(name, code) + extern bool FLAGS_ ## flag_name namespace snappy { static const uint32 kuint32max = static_cast<uint32>(0xFFFFFFFF); static const int64 kint64max = static_cast<int64>(0x7FFFFFFFFFFFFFFFLL); -// Logging. - -#define LOG(level) LogMessage() -#define VLOG(level) true ? (void)0 : \ - snappy::LogMessageVoidify() & snappy::LogMessage() - -class LogMessage { - public: - LogMessage() { } - ~LogMessage() { - cerr << endl; - } - - LogMessage& operator<<(const std::string& msg) { - cerr << msg; - return *this; - } - LogMessage& operator<<(int x) { - cerr << x; - return *this; - } -}; - -// Asserts, both versions activated in debug mode only, -// and ones that are always active. - -#define CRASH_UNLESS(condition) \ - PREDICT_TRUE(condition) ? (void)0 : \ - snappy::LogMessageVoidify() & snappy::LogMessageCrash() - -class LogMessageCrash : public LogMessage { - public: - LogMessageCrash() { } - ~LogMessageCrash() { - cerr << endl; - abort(); - } -}; - -// This class is used to explicitly ignore values in the conditional -// logging macros. This avoids compiler warnings like "value computed -// is not used" and "statement has no effect". - -class LogMessageVoidify { - public: - LogMessageVoidify() { } - // This has to be an operator with a precedence lower than << but - // higher than ?: - void operator&(const LogMessage&) { } -}; - -#define CHECK(cond) CRASH_UNLESS(cond) -#define CHECK_LE(a, b) CRASH_UNLESS((a) <= (b)) -#define CHECK_GE(a, b) CRASH_UNLESS((a) >= (b)) -#define CHECK_EQ(a, b) CRASH_UNLESS((a) == (b)) -#define CHECK_NE(a, b) CRASH_UNLESS((a) != (b)) -#define CHECK_LT(a, b) CRASH_UNLESS((a) < (b)) -#define CHECK_GT(a, b) CRASH_UNLESS((a) > (b)) - -#ifdef NDEBUG - -#define DCHECK(cond) CRASH_UNLESS(true) -#define DCHECK_LE(a, b) CRASH_UNLESS(true) -#define DCHECK_GE(a, b) CRASH_UNLESS(true) -#define DCHECK_EQ(a, b) CRASH_UNLESS(true) -#define DCHECK_NE(a, b) CRASH_UNLESS(true) -#define DCHECK_LT(a, b) CRASH_UNLESS(true) -#define DCHECK_GT(a, b) CRASH_UNLESS(true) - -#else - -#define DCHECK(cond) CHECK(cond) -#define DCHECK_LE(a, b) CHECK_LE(a, b) -#define DCHECK_GE(a, b) CHECK_GE(a, b) -#define DCHECK_EQ(a, b) CHECK_EQ(a, b) -#define DCHECK_NE(a, b) CHECK_NE(a, b) -#define DCHECK_LT(a, b) CHECK_LT(a, b) -#define DCHECK_GT(a, b) CHECK_GT(a, b) - -#endif - // Potentially unaligned loads and stores. +// x86 and PowerPC can simply do these loads and stores native. + #if defined(__i386__) || defined(__x86_64__) || defined(__powerpc__) #define UNALIGNED_LOAD16(_p) (*reinterpret_cast<const uint16 *>(_p)) @@ -189,6 +108,49 @@ class LogMessageVoidify { #define UNALIGNED_STORE32(_p, _val) (*reinterpret_cast<uint32 *>(_p) = (_val)) #define UNALIGNED_STORE64(_p, _val) (*reinterpret_cast<uint64 *>(_p) = (_val)) +// ARMv7 and newer support native unaligned accesses, but only of 16-bit +// and 32-bit values (not 64-bit); older versions either raise a fatal signal, +// do an unaligned read and rotate the words around a bit, or do the reads very +// slowly (trip through kernel mode). There's no simple #define that says just +// “ARMv7 or higher”, so we have to filter away all ARMv5 and ARMv6 +// sub-architectures. +// +// This is a mess, but there's not much we can do about it. + +#elif defined(__arm__) && \ + !defined(__ARM_ARCH_4__) && \ + !defined(__ARM_ARCH_4T__) && \ + !defined(__ARM_ARCH_5__) && \ + !defined(__ARM_ARCH_5T__) && \ + !defined(__ARM_ARCH_5TE__) && \ + !defined(__ARM_ARCH_5TEJ__) && \ + !defined(__ARM_ARCH_6__) && \ + !defined(__ARM_ARCH_6J__) && \ + !defined(__ARM_ARCH_6K__) && \ + !defined(__ARM_ARCH_6Z__) && \ + !defined(__ARM_ARCH_6ZK__) && \ + !defined(__ARM_ARCH_6T2__) + +#define UNALIGNED_LOAD16(_p) (*reinterpret_cast<const uint16 *>(_p)) +#define UNALIGNED_LOAD32(_p) (*reinterpret_cast<const uint32 *>(_p)) + +#define UNALIGNED_STORE16(_p, _val) (*reinterpret_cast<uint16 *>(_p) = (_val)) +#define UNALIGNED_STORE32(_p, _val) (*reinterpret_cast<uint32 *>(_p) = (_val)) + +// TODO(user): NEON supports unaligned 64-bit loads and stores. +// See if that would be more efficient on platforms supporting it, +// at least for copies. + +inline uint64 UNALIGNED_LOAD64(const void *p) { + uint64 t; + memcpy(&t, p, sizeof t); + return t; +} + +inline void UNALIGNED_STORE64(void *p, uint64 v) { + memcpy(p, &v, sizeof v); +} + #else // These functions are provided for architectures that don't support @@ -226,9 +188,31 @@ inline void UNALIGNED_STORE64(void *p, uint64 v) { #endif +// This can be more efficient than UNALIGNED_LOAD64 + UNALIGNED_STORE64 +// on some platforms, in particular ARM. +inline void UnalignedCopy64(const void *src, void *dst) { + if (sizeof(void *) == 8) { + UNALIGNED_STORE64(dst, UNALIGNED_LOAD64(src)); + } else { + const char *src_char = reinterpret_cast<const char *>(src); + char *dst_char = reinterpret_cast<char *>(dst); + + UNALIGNED_STORE32(dst_char, UNALIGNED_LOAD32(src_char)); + UNALIGNED_STORE32(dst_char + 4, UNALIGNED_LOAD32(src_char + 4)); + } +} + // The following guarantees declaration of the byte swap functions. #ifdef WORDS_BIGENDIAN +#ifdef HAVE_SYS_BYTEORDER_H +#include <sys/byteorder.h> +#endif + +#ifdef HAVE_SYS_ENDIAN_H +#include <sys/endian.h> +#endif + #ifdef _MSC_VER #include <stdlib.h> #define bswap_16(x) _byteswap_ushort(x) @@ -242,8 +226,38 @@ inline void UNALIGNED_STORE64(void *p, uint64 v) { #define bswap_32(x) OSSwapInt32(x) #define bswap_64(x) OSSwapInt64(x) -#else +#elif defined(HAVE_BYTESWAP_H) #include <byteswap.h> + +#elif defined(bswap32) +// FreeBSD defines bswap{16,32,64} in <sys/endian.h> (already #included). +#define bswap_16(x) bswap16(x) +#define bswap_32(x) bswap32(x) +#define bswap_64(x) bswap64(x) + +#elif defined(BSWAP_64) +// Solaris 10 defines BSWAP_{16,32,64} in <sys/byteorder.h> (already #included). +#define bswap_16(x) BSWAP_16(x) +#define bswap_32(x) BSWAP_32(x) +#define bswap_64(x) BSWAP_64(x) + +#else + +inline uint16 bswap_16(uint16 x) { + return (x << 8) | (x >> 8); +} + +inline uint32 bswap_32(uint32 x) { + x = ((x & 0xff00ff00UL) >> 8) | ((x & 0x00ff00ffUL) << 8); + return (x >> 16) | (x << 16); +} + +inline uint64 bswap_64(uint64 x) { + x = ((x & 0xff00ff00ff00ff00ULL) >> 8) | ((x & 0x00ff00ff00ff00ffULL) << 8); + x = ((x & 0xffff0000ffff0000ULL) >> 16) | ((x & 0x0000ffff0000ffffULL) << 16); + return (x >> 32) | (x << 32); +} + #endif #endif // WORDS_BIGENDIAN diff --git a/c_src/snappy/snappy-stubs-public.h b/c_src/snappy/snappy-stubs-public.h index e545220..ecda439 100644 --- a/c_src/snappy/snappy-stubs-public.h +++ b/c_src/snappy/snappy-stubs-public.h @@ -36,11 +36,20 @@ #ifndef UTIL_SNAPPY_OPENSOURCE_SNAPPY_STUBS_PUBLIC_H_ #define UTIL_SNAPPY_OPENSOURCE_SNAPPY_STUBS_PUBLIC_H_ +#if 1 #include <stdint.h> +#endif + +#if 1 #include <stddef.h> +#endif + +#if 0 +#include <sys/uio.h> +#endif #define SNAPPY_MAJOR 1 -#define SNAPPY_MINOR 0 +#define SNAPPY_MINOR 1 #define SNAPPY_PATCHLEVEL 1 #define SNAPPY_VERSION \ ((SNAPPY_MAJOR << 16) | (SNAPPY_MINOR << 8) | SNAPPY_PATCHLEVEL) @@ -75,6 +84,15 @@ typedef std::string string; TypeName(const TypeName&); \ void operator=(const TypeName&) +#if !0 +// Windows does not have an iovec type, yet the concept is universally useful. +// It is simple to define it ourselves, so we put it inside our own namespace. +struct iovec { + void* iov_base; + size_t iov_len; +}; +#endif + } // namespace snappy #endif // UTIL_SNAPPY_OPENSOURCE_SNAPPY_STUBS_PUBLIC_H_ diff --git a/c_src/snappy/snappy.cc b/c_src/snappy/snappy.cc index a591aba..f8d0d23 100644 --- a/c_src/snappy/snappy.cc +++ b/c_src/snappy/snappy.cc @@ -82,6 +82,7 @@ enum { COPY_2_BYTE_OFFSET = 2, COPY_4_BYTE_OFFSET = 3 }; +static const int kMaximumTagLength = 5; // COPY_4_BYTE_OFFSET plus the actual offset. // Copy "len" bytes from "src" to "op", one byte at a time. Used for // handling COPY operations where the input and output regions may @@ -94,8 +95,8 @@ enum { // ababababababababababab // Note that this does not match the semantics of either memcpy() // or memmove(). -static inline void IncrementalCopy(const char* src, char* op, int len) { - DCHECK_GT(len, 0); +static inline void IncrementalCopy(const char* src, char* op, ssize_t len) { + assert(len > 0); do { *op++ = *src++; } while (--len > 0); @@ -136,22 +137,22 @@ namespace { const int kMaxIncrementCopyOverflow = 10; -} // namespace - -static inline void IncrementalCopyFastPath(const char* src, char* op, int len) { +inline void IncrementalCopyFastPath(const char* src, char* op, ssize_t len) { while (op - src < 8) { - UNALIGNED_STORE64(op, UNALIGNED_LOAD64(src)); + UnalignedCopy64(src, op); len -= op - src; op += op - src; } while (len > 0) { - UNALIGNED_STORE64(op, UNALIGNED_LOAD64(src)); + UnalignedCopy64(src, op); src += 8; op += 8; len -= 8; } } +} // namespace + static inline char* EmitLiteral(char* op, const char* literal, int len, @@ -172,8 +173,8 @@ static inline char* EmitLiteral(char* op, // - The output will always have 32 spare bytes (see // MaxCompressedLength). if (allow_fast_path && len <= 16) { - UNALIGNED_STORE64(op, UNALIGNED_LOAD64(literal)); - UNALIGNED_STORE64(op + 8, UNALIGNED_LOAD64(literal + 8)); + UnalignedCopy64(literal, op); + UnalignedCopy64(literal + 8, op + 8); return op + len; } } else { @@ -194,25 +195,25 @@ static inline char* EmitLiteral(char* op, return op + len; } -static inline char* EmitCopyLessThan64(char* op, int offset, int len) { - DCHECK_LE(len, 64); - DCHECK_GE(len, 4); - DCHECK_LT(offset, 65536); +static inline char* EmitCopyLessThan64(char* op, size_t offset, int len) { + assert(len <= 64); + assert(len >= 4); + assert(offset < 65536); if ((len < 12) && (offset < 2048)) { - int len_minus_4 = len - 4; + size_t len_minus_4 = len - 4; assert(len_minus_4 < 8); // Must fit in 3 bits - *op++ = COPY_1_BYTE_OFFSET | ((len_minus_4) << 2) | ((offset >> 8) << 5); + *op++ = COPY_1_BYTE_OFFSET + ((len_minus_4) << 2) + ((offset >> 8) << 5); *op++ = offset & 0xff; } else { - *op++ = COPY_2_BYTE_OFFSET | ((len-1) << 2); + *op++ = COPY_2_BYTE_OFFSET + ((len-1) << 2); LittleEndian::Store16(op, offset); op += 2; } return op; } -static inline char* EmitCopy(char* op, int offset, int len) { +static inline char* EmitCopy(char* op, size_t offset, int len) { // Emit 64 byte copies but make sure to keep at least four bytes reserved while (len >= 68) { op = EmitCopyLessThan64(op, offset, 64); @@ -249,12 +250,10 @@ uint16* WorkingMemory::GetHashTable(size_t input_size, int* table_size) { // compression, and if the input is short, we won't need that // many hash table entries anyway. assert(kMaxHashTableSize >= 256); - int htsize = 256; + size_t htsize = 256; while (htsize < kMaxHashTableSize && htsize < input_size) { htsize <<= 1; } - CHECK_EQ(0, htsize & (htsize - 1)) << ": must be power of two"; - CHECK_LE(htsize, kMaxHashTableSize) << ": hash table too large"; uint16* table; if (htsize <= ARRAYSIZE(small_table_)) { @@ -272,16 +271,49 @@ uint16* WorkingMemory::GetHashTable(size_t input_size, int* table_size) { } } // end namespace internal -// For 0 <= offset <= 4, GetUint32AtOffset(UNALIGNED_LOAD64(p), offset) will +// For 0 <= offset <= 4, GetUint32AtOffset(GetEightBytesAt(p), offset) will // equal UNALIGNED_LOAD32(p + offset). Motivation: On x86-64 hardware we have // empirically found that overlapping loads such as // UNALIGNED_LOAD32(p) ... UNALIGNED_LOAD32(p+1) ... UNALIGNED_LOAD32(p+2) // are slower than UNALIGNED_LOAD64(p) followed by shifts and casts to uint32. +// +// We have different versions for 64- and 32-bit; ideally we would avoid the +// two functions and just inline the UNALIGNED_LOAD64 call into +// GetUint32AtOffset, but GCC (at least not as of 4.6) is seemingly not clever +// enough to avoid loading the value multiple times then. For 64-bit, the load +// is done when GetEightBytesAt() is called, whereas for 32-bit, the load is +// done at GetUint32AtOffset() time. + +#ifdef ARCH_K8 + +typedef uint64 EightBytesReference; + +static inline EightBytesReference GetEightBytesAt(const char* ptr) { + return UNALIGNED_LOAD64(ptr); +} + static inline uint32 GetUint32AtOffset(uint64 v, int offset) { - DCHECK(0 <= offset && offset <= 4) << offset; + assert(offset >= 0); + assert(offset <= 4); return v >> (LittleEndian::IsLittleEndian() ? 8 * offset : 32 - 8 * offset); } +#else + +typedef const char* EightBytesReference; + +static inline EightBytesReference GetEightBytesAt(const char* ptr) { + return ptr; +} + +static inline uint32 GetUint32AtOffset(const char* v, int offset) { + assert(offset >= 0); + assert(offset <= 4); + return UNALIGNED_LOAD32(v + offset); +} + +#endif + // Flat array compression that does not emit the "uncompressed length" // prefix. Compresses "input" string to the "*op" buffer. // @@ -294,29 +326,29 @@ static inline uint32 GetUint32AtOffset(uint64 v, int offset) { // Returns an "end" pointer into "op" buffer. // "end - op" is the compressed size of "input". namespace internal { -char* CompressFragment(const char* const input, - const size_t input_size, +char* CompressFragment(const char* input, + size_t input_size, char* op, uint16* table, const int table_size) { // "ip" is the input pointer, and "op" is the output pointer. const char* ip = input; - CHECK_LE(input_size, kBlockSize); - CHECK_EQ(table_size & (table_size - 1), 0) << ": table must be power of two"; + assert(input_size <= kBlockSize); + assert((table_size & (table_size - 1)) == 0); // table must be power of two const int shift = 32 - Bits::Log2Floor(table_size); - DCHECK_EQ(kuint32max >> shift, table_size - 1); + assert(static_cast<int>(kuint32max >> shift) == table_size - 1); const char* ip_end = input + input_size; const char* base_ip = ip; // Bytes in [next_emit, ip) will be emitted as literal bytes. Or // [next_emit, ip_end) after the main loop. const char* next_emit = ip; - const int kInputMarginBytes = 15; + const size_t kInputMarginBytes = 15; if (PREDICT_TRUE(input_size >= kInputMarginBytes)) { const char* ip_limit = input + input_size - kInputMarginBytes; for (uint32 next_hash = Hash(++ip, shift); ; ) { - DCHECK_LT(next_emit, ip); + assert(next_emit < ip); // The body of this loop calls EmitLiteral once and then EmitCopy one or // more times. (The exception is that when we're close to exhausting // the input we goto emit_remainder.) @@ -349,7 +381,7 @@ char* CompressFragment(const char* const input, do { ip = next_ip; uint32 hash = next_hash; - DCHECK_EQ(hash, Hash(ip, shift)); + assert(hash == Hash(ip, shift)); uint32 bytes_between_hash_lookups = skip++ >> 5; next_ip = ip + bytes_between_hash_lookups; if (PREDICT_FALSE(next_ip > ip_limit)) { @@ -357,8 +389,8 @@ char* CompressFragment(const char* const input, } next_hash = Hash(next_ip, shift); candidate = base_ip + table[hash]; - DCHECK_GE(candidate, base_ip); - DCHECK_LT(candidate, ip); + assert(candidate >= base_ip); + assert(candidate < ip); table[hash] = ip - base_ip; } while (PREDICT_TRUE(UNALIGNED_LOAD32(ip) != @@ -367,7 +399,7 @@ char* CompressFragment(const char* const input, // Step 2: A 4-byte match has been found. We'll later see if more // than 4 bytes match. But, prior to the match, input // bytes [next_emit, ip) are unmatched. Emit them as "literal bytes." - DCHECK_LE(next_emit + 16, ip_end); + assert(next_emit + 16 <= ip_end); op = EmitLiteral(op, next_emit, ip - next_emit, true); // Step 3: Call EmitCopy, and then see if another EmitCopy could @@ -378,7 +410,7 @@ char* CompressFragment(const char* const input, // though we don't yet know how big the literal will be. We handle that // by proceeding to the next iteration of the main loop. We also can exit // this loop via goto if we get close to exhausting the input. - uint64 input_bytes = 0; + EightBytesReference input_bytes; uint32 candidate_bytes = 0; do { @@ -387,8 +419,8 @@ char* CompressFragment(const char* const input, const char* base = ip; int matched = 4 + FindMatchLength(candidate + 4, ip + 4, ip_end); ip += matched; - int offset = base - candidate; - DCHECK_EQ(0, memcmp(base, candidate, matched)); + size_t offset = base - candidate; + assert(0 == memcmp(base, candidate, matched)); op = EmitCopy(op, offset, matched); // We could immediately start working at ip now, but to improve // compression we first update table[Hash(ip - 1, ...)]. @@ -397,7 +429,7 @@ char* CompressFragment(const char* const input, if (PREDICT_FALSE(ip >= ip_limit)) { goto emit_remainder; } - input_bytes = UNALIGNED_LOAD64(insert_tail); + input_bytes = GetEightBytesAt(insert_tail); uint32 prev_hash = HashBytes(GetUint32AtOffset(input_bytes, 0), shift); table[prev_hash] = ip - base_ip - 1; uint32 cur_hash = HashBytes(GetUint32AtOffset(input_bytes, 1), shift); @@ -435,12 +467,31 @@ char* CompressFragment(const char* const input, // bool CheckLength() const; // // // Called repeatedly during decompression -// bool Append(const char* ip, uint32 length, bool allow_fast_path); -// bool AppendFromSelf(uint32 offset, uint32 length); -// }; +// bool Append(const char* ip, size_t length); +// bool AppendFromSelf(uint32 offset, size_t length); // -// "allow_fast_path" is a parameter that says if there is at least 16 -// readable bytes in "ip". It is currently only used by SnappyArrayWriter. +// // The rules for how TryFastAppend differs from Append are somewhat +// // convoluted: +// // +// // - TryFastAppend is allowed to decline (return false) at any +// // time, for any reason -- just "return false" would be +// // a perfectly legal implementation of TryFastAppend. +// // The intention is for TryFastAppend to allow a fast path +// // in the common case of a small append. +// // - TryFastAppend is allowed to read up to <available> bytes +// // from the input buffer, whereas Append is allowed to read +// // <length>. However, if it returns true, it must leave +// // at least five (kMaximumTagLength) bytes in the input buffer +// // afterwards, so that there is always enough space to read the +// // next tag without checking for a refill. +// // - TryFastAppend must always return decline (return false) +// // if <length> is 61 or more, as in this case the literal length is not +// // decoded fully. In practice, this should not be a big problem, +// // as it is unlikely that one would implement a fast path accepting +// // this much data. +// // +// bool TryFastAppend(const char* ip, size_t available, size_t length); +// }; // ----------------------------------------------------------------------- // Lookup table for decompression code. Generated by ComputeTable() below. @@ -507,9 +558,9 @@ static uint16 MakeEntry(unsigned int extra, unsigned int len, unsigned int copy_offset) { // Check that all of the fields fit within the allocated space - DCHECK_EQ(extra, extra & 0x7); // At most 3 bits - DCHECK_EQ(copy_offset, copy_offset & 0x7); // At most 3 bits - DCHECK_EQ(len, len & 0x7f); // At most 7 bits + assert(extra == (extra & 0x7)); // At most 3 bits + assert(copy_offset == (copy_offset & 0x7)); // At most 3 bits + assert(len == (len & 0x7f)); // At most 7 bits return len | (copy_offset << 8) | (extra << 11); } @@ -567,9 +618,15 @@ static void ComputeTable() { } // Check that each entry was initialized exactly once. - CHECK_EQ(assigned, 256); + if (assigned != 256) { + fprintf(stderr, "ComputeTable: assigned only %d of 256\n", assigned); + abort(); + } for (int i = 0; i < 256; i++) { - CHECK_NE(dst[i], 0xffff); + if (dst[i] == 0xffff) { + fprintf(stderr, "ComputeTable: did not assign byte %d\n", i); + abort(); + } } if (FLAGS_snappy_dump_decompression_table) { @@ -584,10 +641,13 @@ static void ComputeTable() { // Check that computed table matched recorded table for (int i = 0; i < 256; i++) { - CHECK_EQ(dst[i], char_table[i]); + if (dst[i] != char_table[i]) { + fprintf(stderr, "ComputeTable: byte %d: computed (%x), expect (%x)\n", + i, static_cast<int>(dst[i]), static_cast<int>(char_table[i])); + abort(); + } } } -REGISTER_MODULE_INITIALIZER(snappy, ComputeTable()); #endif /* !NDEBUG */ // Helper class for decompression @@ -598,7 +658,7 @@ class SnappyDecompressor { const char* ip_limit_; // Points just past buffered bytes uint32 peeked_; // Bytes peeked from reader (need to skip) bool eof_; // Hit end of input without an error? - char scratch_[5]; // Temporary buffer for PeekFast() boundaries + char scratch_[kMaximumTagLength]; // See RefillTag(). // Ensure that all of the tag metadata for the next tag is available // in [ip_..ip_limit_-1]. Also ensures that [ip,ip+4] is readable even @@ -630,7 +690,7 @@ class SnappyDecompressor { // On succcess, stores the length in *result and returns true. // On failure, returns false. bool ReadUncompressedLength(uint32* result) { - DCHECK(ip_ == NULL); // Must not have read anything yet + assert(ip_ == NULL); // Must not have read anything yet // Length is encoded in 1..5 bytes *result = 0; uint32 shift = 0; @@ -655,25 +715,43 @@ class SnappyDecompressor { template <class Writer> void DecompressAllTags(Writer* writer) { const char* ip = ip_; - for ( ;; ) { - if (ip_limit_ - ip < 5) { - ip_ = ip; - if (!RefillTag()) return; - ip = ip_; - } + // We could have put this refill fragment only at the beginning of the loop. + // However, duplicating it at the end of each branch gives the compiler more + // scope to optimize the <ip_limit_ - ip> expression based on the local + // context, which overall increases speed. + #define MAYBE_REFILL() \ + if (ip_limit_ - ip < kMaximumTagLength) { \ + ip_ = ip; \ + if (!RefillTag()) return; \ + ip = ip_; \ + } + + MAYBE_REFILL(); + for ( ;; ) { const unsigned char c = *(reinterpret_cast<const unsigned char*>(ip++)); - const uint32 entry = char_table[c]; - const uint32 trailer = LittleEndian::Load32(ip) & wordmask[entry >> 11]; - ip += entry >> 11; - const uint32 length = entry & 0xff; if ((c & 0x3) == LITERAL) { - uint32 literal_length = length + trailer; - uint32 avail = ip_limit_ - ip; + size_t literal_length = (c >> 2) + 1u; + if (writer->TryFastAppend(ip, ip_limit_ - ip, literal_length)) { + assert(literal_length < 61); + ip += literal_length; + // NOTE(user): There is no MAYBE_REFILL() here, as TryFastAppend() + // will not return true unless there's already at least five spare + // bytes in addition to the literal. + continue; + } + if (PREDICT_FALSE(literal_length >= 61)) { + // Long literal. + const size_t literal_length_length = literal_length - 60; + literal_length = + (LittleEndian::Load32(ip) & wordmask[literal_length_length]) + 1; + ip += literal_length_length; + } + + size_t avail = ip_limit_ - ip; while (avail < literal_length) { - bool allow_fast_path = (avail >= 16); - if (!writer->Append(ip, avail, allow_fast_path)) return; + if (!writer->Append(ip, avail)) return; literal_length -= avail; reader_->Skip(peeked_); size_t n; @@ -683,12 +761,17 @@ class SnappyDecompressor { if (avail == 0) return; // Premature end of input ip_limit_ = ip + avail; } - bool allow_fast_path = (avail >= 16); - if (!writer->Append(ip, literal_length, allow_fast_path)) { + if (!writer->Append(ip, literal_length)) { return; } ip += literal_length; + MAYBE_REFILL(); } else { + const uint32 entry = char_table[c]; + const uint32 trailer = LittleEndian::Load32(ip) & wordmask[entry >> 11]; + const uint32 length = entry & 0xff; + ip += entry >> 11; + // copy_offset/256 is encoded in bits 8..10. By just fetching // those bits, we get copy_offset (since the bit-field starts at // bit 8). @@ -696,8 +779,11 @@ class SnappyDecompressor { if (!writer->AppendFromSelf(copy_offset + trailer, length)) { return; } + MAYBE_REFILL(); } } + +#undef MAYBE_REFILL } }; @@ -717,11 +803,11 @@ bool SnappyDecompressor::RefillTag() { } // Read the tag character - DCHECK_LT(ip, ip_limit_); + assert(ip < ip_limit_); const unsigned char c = *(reinterpret_cast<const unsigned char*>(ip)); const uint32 entry = char_table[c]; const uint32 needed = (entry >> 11) + 1; // +1 byte for 'c' - DCHECK_LE(needed, sizeof(scratch_)); + assert(needed <= sizeof(scratch_)); // Read more bytes from reader if needed uint32 nbuf = ip_limit_ - ip; @@ -742,10 +828,10 @@ bool SnappyDecompressor::RefillTag() { nbuf += to_add; reader_->Skip(to_add); } - DCHECK_EQ(nbuf, needed); + assert(nbuf == needed); ip_ = scratch_; ip_limit_ = scratch_ + needed; - } else if (nbuf < 5) { + } else if (nbuf < kMaximumTagLength) { // Have enough bytes, but move into scratch_ so that we do not // read past end of input memmove(scratch_, ip, nbuf); @@ -761,23 +847,23 @@ bool SnappyDecompressor::RefillTag() { } template <typename Writer> -static bool InternalUncompress(Source* r, - Writer* writer, - uint32 max_len) { +static bool InternalUncompress(Source* r, Writer* writer) { // Read the uncompressed length from the front of the compressed input SnappyDecompressor decompressor(r); uint32 uncompressed_len = 0; if (!decompressor.ReadUncompressedLength(&uncompressed_len)) return false; - // Protect against possible DoS attack - if (static_cast<uint64>(uncompressed_len) > max_len) { - return false; - } + return InternalUncompressAllTags(&decompressor, writer, uncompressed_len); +} +template <typename Writer> +static bool InternalUncompressAllTags(SnappyDecompressor* decompressor, + Writer* writer, + uint32 uncompressed_len) { writer->SetExpectedLength(uncompressed_len); // Process the entire input - decompressor.DecompressAllTags(writer); - return (decompressor.eof() && writer->CheckLength()); + decompressor->DecompressAllTags(writer); + return (decompressor->eof() && writer->CheckLength()); } bool GetUncompressedLength(Source* source, uint32* result) { @@ -787,7 +873,7 @@ bool GetUncompressedLength(Source* source, uint32* result) { size_t Compress(Source* reader, Sink* writer) { size_t written = 0; - int N = reader->Available(); + size_t N = reader->Available(); char ulength[Varint::kMax32]; char* p = Varint::Encode32(ulength, N); writer->Append(ulength, p-ulength); @@ -801,11 +887,11 @@ size_t Compress(Source* reader, Sink* writer) { // Get next block to compress (without copying if possible) size_t fragment_size; const char* fragment = reader->Peek(&fragment_size); - DCHECK_NE(fragment_size, 0) << ": premature end of input"; - const int num_to_read = min(N, kBlockSize); + assert(fragment_size != 0); // premature end of input + const size_t num_to_read = min(N, kBlockSize); size_t bytes_read = fragment_size; - int pending_advance = 0; + size_t pending_advance = 0; if (bytes_read >= num_to_read) { // Buffer returned by reader is large enough pending_advance = num_to_read; @@ -828,11 +914,11 @@ size_t Compress(Source* reader, Sink* writer) { bytes_read += n; reader->Skip(n); } - DCHECK_EQ(bytes_read, num_to_read); + assert(bytes_read == num_to_read); fragment = scratch; fragment_size = num_to_read; } - DCHECK_EQ(fragment_size, num_to_read); + assert(fragment_size == num_to_read); // Get encoding table for compression int table_size; @@ -866,6 +952,183 @@ size_t Compress(Source* reader, Sink* writer) { return written; } +// ----------------------------------------------------------------------- +// IOVec interfaces +// ----------------------------------------------------------------------- + +// A type that writes to an iovec. +// Note that this is not a "ByteSink", but a type that matches the +// Writer template argument to SnappyDecompressor::DecompressAllTags(). +class SnappyIOVecWriter { + private: + const struct iovec* output_iov_; + const size_t output_iov_count_; + + // We are currently writing into output_iov_[curr_iov_index_]. + int curr_iov_index_; + + // Bytes written to output_iov_[curr_iov_index_] so far. + size_t curr_iov_written_; + + // Total bytes decompressed into output_iov_ so far. + size_t total_written_; + + // Maximum number of bytes that will be decompressed into output_iov_. + size_t output_limit_; + + inline char* GetIOVecPointer(int index, size_t offset) { + return reinterpret_cast<char*>(output_iov_[index].iov_base) + + offset; + } + + public: + // Does not take ownership of iov. iov must be valid during the + // entire lifetime of the SnappyIOVecWriter. + inline SnappyIOVecWriter(const struct iovec* iov, size_t iov_count) + : output_iov_(iov), + output_iov_count_(iov_count), + curr_iov_index_(0), + curr_iov_written_(0), + total_written_(0), + output_limit_(-1) { + } + + inline void SetExpectedLength(size_t len) { + output_limit_ = len; + } + + inline bool CheckLength() const { + return total_written_ == output_limit_; + } + + inline bool Append(const char* ip, size_t len) { + if (total_written_ + len > output_limit_) { + return false; + } + + while (len > 0) { + assert(curr_iov_written_ <= output_iov_[curr_iov_index_].iov_len); + if (curr_iov_written_ >= output_iov_[curr_iov_index_].iov_len) { + // This iovec is full. Go to the next one. + if (curr_iov_index_ + 1 >= output_iov_count_) { + return false; + } + curr_iov_written_ = 0; + ++curr_iov_index_; + } + + const size_t to_write = std::min( + len, output_iov_[curr_iov_index_].iov_len - curr_iov_written_); + memcpy(GetIOVecPointer(curr_iov_index_, curr_iov_written_), + ip, + to_write); + curr_iov_written_ += to_write; + total_written_ += to_write; + ip += to_write; + len -= to_write; + } + + return true; + } + + inline bool TryFastAppend(const char* ip, size_t available, size_t len) { + const size_t space_left = output_limit_ - total_written_; + if (len <= 16 && available >= 16 + kMaximumTagLength && space_left >= 16 && + output_iov_[curr_iov_index_].iov_len - curr_iov_written_ >= 16) { + // Fast path, used for the majority (about 95%) of invocations. + char* ptr = GetIOVecPointer(curr_iov_index_, curr_iov_written_); + UnalignedCopy64(ip, ptr); + UnalignedCopy64(ip + 8, ptr + 8); + curr_iov_written_ += len; + total_written_ += len; + return true; + } + + return false; + } + + inline bool AppendFromSelf(size_t offset, size_t len) { + if (offset > total_written_ || offset == 0) { + return false; + } + const size_t space_left = output_limit_ - total_written_; + if (len > space_left) { + return false; + } + + // Locate the iovec from which we need to start the copy. + int from_iov_index = curr_iov_index_; + size_t from_iov_offset = curr_iov_written_; + while (offset > 0) { + if (from_iov_offset >= offset) { + from_iov_offset -= offset; + break; + } + + offset -= from_iov_offset; + --from_iov_index; + assert(from_iov_index >= 0); + from_iov_offset = output_iov_[from_iov_index].iov_len; + } + + // Copy <len> bytes starting from the iovec pointed to by from_iov_index to + // the current iovec. + while (len > 0) { + assert(from_iov_index <= curr_iov_index_); + if (from_iov_index != curr_iov_index_) { + const size_t to_copy = std::min( + output_iov_[from_iov_index].iov_len - from_iov_offset, + len); + Append(GetIOVecPointer(from_iov_index, from_iov_offset), to_copy); + len -= to_copy; + if (len > 0) { + ++from_iov_index; + from_iov_offset = 0; + } + } else { + assert(curr_iov_written_ <= output_iov_[curr_iov_index_].iov_len); + size_t to_copy = std::min(output_iov_[curr_iov_index_].iov_len - + curr_iov_written_, + len); + if (to_copy == 0) { + // This iovec is full. Go to the next one. + if (curr_iov_index_ + 1 >= output_iov_count_) { + return false; + } + ++curr_iov_index_; + curr_iov_written_ = 0; + continue; + } + if (to_copy > len) { + to_copy = len; + } + IncrementalCopy(GetIOVecPointer(from_iov_index, from_iov_offset), + GetIOVecPointer(curr_iov_index_, curr_iov_written_), + to_copy); + curr_iov_written_ += to_copy; + from_iov_offset += to_copy; + total_written_ += to_copy; + len -= to_copy; + } + } + + return true; + } + +}; + +bool RawUncompressToIOVec(const char* compressed, size_t compressed_length, + const struct iovec* iov, size_t iov_cnt) { + ByteArraySource reader(compressed, compressed_length); + return RawUncompressToIOVec(&reader, iov, iov_cnt); +} + +bool RawUncompressToIOVec(Source* compressed, const struct iovec* iov, + size_t iov_cnt) { + SnappyIOVecWriter output(iov, iov_cnt); + return InternalUncompress(compressed, &output); +} + // ----------------------------------------------------------------------- // Flat array interfaces // ----------------------------------------------------------------------- @@ -893,34 +1156,51 @@ class SnappyArrayWriter { return op_ == op_limit_; } - inline bool Append(const char* ip, uint32 len, bool allow_fast_path) { + inline bool Append(const char* ip, size_t len) { char* op = op_; - const int space_left = op_limit_ - op; - if (allow_fast_path && len <= 16 && space_left >= 16) { - // Fast path, used for the majority (about 90%) of dynamic invocations. - UNALIGNED_STORE64(op, UNALIGNED_LOAD64(ip)); - UNALIGNED_STORE64(op + 8, UNALIGNED_LOAD64(ip + 8)); - } else { - if (space_left < len) { - return false; - } - memcpy(op, ip, len); + const size_t space_left = op_limit_ - op; + if (space_left < len) { + return false; } + memcpy(op, ip, len); op_ = op + len; return true; } - inline bool AppendFromSelf(uint32 offset, uint32 len) { + inline bool TryFastAppend(const char* ip, size_t available, size_t len) { char* op = op_; - const int space_left = op_limit_ - op; + const size_t space_left = op_limit_ - op; + if (len <= 16 && available >= 16 + kMaximumTagLength && space_left >= 16) { + // Fast path, used for the majority (about 95%) of invocations. + UnalignedCopy64(ip, op); + UnalignedCopy64(ip + 8, op + 8); + op_ = op + len; + return true; + } else { + return false; + } + } - if (op - base_ <= offset - 1u) { // -1u catches offset==0 + inline bool AppendFromSelf(size_t offset, size_t len) { + char* op = op_; + const size_t space_left = op_limit_ - op; + + // Check if we try to append from before the start of the buffer. + // Normally this would just be a check for "produced < offset", + // but "produced <= offset - 1u" is equivalent for every case + // except the one where offset==0, where the right side will wrap around + // to a very big number. This is convenient, as offset==0 is another + // invalid case that we also want to catch, so that we do not go + // into an infinite loop. + assert(op >= base_); + size_t produced = op - base_; + if (produced <= offset - 1u) { return false; } if (len <= 16 && offset >= 8 && space_left >= 16) { // Fast path, used for the majority (70-80%) of dynamic invocations. - UNALIGNED_STORE64(op, UNALIGNED_LOAD64(op - offset)); - UNALIGNED_STORE64(op + 8, UNALIGNED_LOAD64(op - offset + 8)); + UnalignedCopy64(op - offset, op); + UnalignedCopy64(op - offset + 8, op + 8); } else { if (space_left >= len + kMaxIncrementCopyOverflow) { IncrementalCopyFastPath(op - offset, op, len); @@ -944,7 +1224,7 @@ bool RawUncompress(const char* compressed, size_t n, char* uncompressed) { bool RawUncompress(Source* compressed, char* uncompressed) { SnappyArrayWriter output(uncompressed); - return InternalUncompress(compressed, &output, kuint32max); + return InternalUncompress(compressed, &output); } bool Uncompress(const char* compressed, size_t n, string* uncompressed) { @@ -952,9 +1232,9 @@ bool Uncompress(const char* compressed, size_t n, string* uncompressed) { if (!GetUncompressedLength(compressed, n, &ulength)) { return false; } - // Protect against possible DoS attack - if ((static_cast<uint64>(ulength) + uncompressed->size()) > - uncompressed->max_size()) { + // On 32-bit builds: max_size() < kuint32max. Check for that instead + // of crashing (e.g., consider externally specified compressed data). + if (ulength > uncompressed->max_size()) { return false; } STLStringResizeUninitialized(uncompressed, ulength); @@ -976,12 +1256,17 @@ class SnappyDecompressionValidator { inline bool CheckLength() const { return expected_ == produced_; } - inline bool Append(const char* ip, uint32 len, bool allow_fast_path) { + inline bool Append(const char* ip, size_t len) { produced_ += len; return produced_ <= expected_; } - inline bool AppendFromSelf(uint32 offset, uint32 len) { - if (produced_ <= offset - 1u) return false; // -1u catches offset==0 + inline bool TryFastAppend(const char* ip, size_t available, size_t length) { + return false; + } + inline bool AppendFromSelf(size_t offset, size_t len) { + // See SnappyArrayWriter::AppendFromSelf for an explanation of + // the "offset - 1u" trick. + if (produced_ <= offset - 1u) return false; produced_ += len; return produced_ <= expected_; } @@ -990,7 +1275,7 @@ class SnappyDecompressionValidator { bool IsValidCompressedBuffer(const char* compressed, size_t n) { ByteArraySource reader(compressed, n); SnappyDecompressionValidator writer; - return InternalUncompress(&reader, &writer, kuint32max); + return InternalUncompress(&reader, &writer); } void RawCompress(const char* input, diff --git a/c_src/snappy/snappy.h b/c_src/snappy/snappy.h index 8d6ef22..e879e79 100644 --- a/c_src/snappy/snappy.h +++ b/c_src/snappy/snappy.h @@ -56,6 +56,13 @@ namespace snappy { // number of bytes written. size_t Compress(Source* source, Sink* sink); + // Find the uncompressed length of the given stream, as given by the header. + // Note that the true length could deviate from this; the stream could e.g. + // be truncated. + // + // Also note that this leaves "*source" in a state that is unsuitable for + // further operations, such as RawUncompress(). You will need to rewind + // or recreate the source yourself before attempting any further calls. bool GetUncompressedLength(Source* source, uint32* result); // ------------------------------------------------------------------------ @@ -117,6 +124,28 @@ namespace snappy { // returns false if the message is corrupted and could not be decrypted bool RawUncompress(Source* compressed, char* uncompressed); + // Given data in "compressed[0..compressed_length-1]" generated by + // calling the Snappy::Compress routine, this routine + // stores the uncompressed data to the iovec "iov". The number of physical + // buffers in "iov" is given by iov_cnt and their cumulative size + // must be at least GetUncompressedLength(compressed). The individual buffers + // in "iov" must not overlap with each other. + // + // returns false if the message is corrupted and could not be decrypted + bool RawUncompressToIOVec(const char* compressed, size_t compressed_length, + const struct iovec* iov, size_t iov_cnt); + + // Given data from the byte source 'compressed' generated by calling + // the Snappy::Compress routine, this routine stores the uncompressed + // data to the iovec "iov". The number of physical + // buffers in "iov" is given by iov_cnt and their cumulative size + // must be at least GetUncompressedLength(compressed). The individual buffers + // in "iov" must not overlap with each other. + // + // returns false if the message is corrupted and could not be decrypted + bool RawUncompressToIOVec(Source* compressed, const struct iovec* iov, + size_t iov_cnt); + // Returns the maximal size of the compressed representation of // input data that is "source_bytes" bytes in length; size_t MaxCompressedLength(size_t source_bytes); @@ -135,20 +164,20 @@ namespace snappy { bool IsValidCompressedBuffer(const char* compressed, size_t compressed_length); - // *** DO NOT CHANGE THE VALUE OF kBlockSize *** + // The size of a compression block. Note that many parts of the compression + // code assumes that kBlockSize <= 65536; in particular, the hash table + // can only store 16-bit offsets, and EmitCopy() also assumes the offset + // is 65535 bytes or less. Note also that if you change this, it will + // affect the framing format (see framing_format.txt). // - // New Compression code chops up the input into blocks of at most - // the following size. This ensures that back-references in the - // output never cross kBlockSize block boundaries. This can be - // helpful in implementing blocked decompression. However the - // decompression code should not rely on this guarantee since older - // compression code may not obey it. - static const int kBlockLog = 15; - static const int kBlockSize = 1 << kBlockLog; + // Note that there might be older data around that is compressed with larger + // block sizes, so the decompression code should not rely on the + // non-existence of long backreferences. + static const int kBlockLog = 16; + static const size_t kBlockSize = 1 << kBlockLog; static const int kMaxHashTableBits = 14; - static const int kMaxHashTableSize = 1 << kMaxHashTableBits; - + static const size_t kMaxHashTableSize = 1 << kMaxHashTableBits; } // end namespace snappy diff --git a/c_src/snappy_nif.cc b/c_src/snappy_nif.cc index 93c1859..4c690ab 100644 --- a/c_src/snappy_nif.cc +++ b/c_src/snappy_nif.cc @@ -135,7 +135,7 @@ BEGIN_C ERL_NIF_TERM -snappy_compress(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]) +snappy_compress_erl(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]) { ErlNifBinary input; @@ -157,7 +157,7 @@ snappy_compress(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]) ERL_NIF_TERM -snappy_decompress(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]) +snappy_decompress_erl(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]) { ErlNifBinary bin; ErlNifBinary ret; @@ -189,7 +189,7 @@ snappy_decompress(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]) ERL_NIF_TERM -snappy_uncompressed_length(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]) +snappy_uncompressed_length_erl(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]) { ErlNifBinary bin; size_t len; @@ -252,9 +252,9 @@ on_upgrade(ErlNifEnv* env, void** priv, void** old_priv, ERL_NIF_TERM info) static ErlNifFunc nif_functions[] = { - {"compress", 1, snappy_compress}, - {"decompress", 1, snappy_decompress}, - {"uncompressed_length", 1, snappy_uncompressed_length}, + {"compress", 1, snappy_compress_erl}, + {"decompress", 1, snappy_decompress_erl}, + {"uncompressed_length", 1, snappy_uncompressed_length_erl}, {"is_valid", 1, snappy_is_valid} }; diff --git a/rebar.config b/rebar.config index ad92b23..329f5ec 100644 --- a/rebar.config +++ b/rebar.config @@ -1,4 +1,4 @@ -{require_otp_vsn, "R13B04|R14|R15"}. +{require_otp_vsn, "R13B04|R14|R15|R16"}. {erl_opts, [debug_info, warn_unused_vars, warn_shadow_vars, warn_unused_import]}. {port_env, [
