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snappy/snappy-stubs-internal.h

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// Copyright 2011 Google Inc. All Rights Reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Various stubs for the open-source version of Snappy.
#ifndef THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_STUBS_INTERNAL_H_
#define THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_STUBS_INTERNAL_H_
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <string>
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#ifdef HAVE_SYS_MMAN_H
#include <sys/mman.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#if defined(_MSC_VER)
#include <intrin.h>
#endif // defined(_MSC_VER)
#ifndef __has_feature
#define __has_feature(x) 0
#endif
#if __has_feature(memory_sanitizer)
#include <sanitizer/msan_interface.h>
#define SNAPPY_ANNOTATE_MEMORY_IS_INITIALIZED(address, size) \
__msan_unpoison((address), (size))
#else
#define SNAPPY_ANNOTATE_MEMORY_IS_INITIALIZED(address, size) /* empty */
#endif // __has_feature(memory_sanitizer)
#include "snappy-stubs-public.h"
#if defined(__x86_64__)
// Enable 64-bit optimized versions of some routines.
#define ARCH_K8 1
#elif defined(__ppc64__)
#define ARCH_PPC 1
#elif defined(__aarch64__)
#define ARCH_ARM 1
#endif
// Needed by OS X, among others.
#ifndef MAP_ANONYMOUS
#define MAP_ANONYMOUS MAP_ANON
#endif
// The size of an array, if known at compile-time.
// Will give unexpected results if used on a pointer.
// We undefine it first, since some compilers already have a definition.
#ifdef ARRAYSIZE
#undef ARRAYSIZE
#endif
#define ARRAYSIZE(a) (sizeof(a) / sizeof(*(a)))
// Static prediction hints.
#ifdef HAVE_BUILTIN_EXPECT
#define SNAPPY_PREDICT_FALSE(x) (__builtin_expect(x, 0))
#define SNAPPY_PREDICT_TRUE(x) (__builtin_expect(!!(x), 1))
#else
#define SNAPPY_PREDICT_FALSE(x) x
#define SNAPPY_PREDICT_TRUE(x) x
#endif
// This is only used for recomputing the tag byte table used during
// decompression; for simplicity we just remove it from the open-source
// 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
#define DECLARE_bool(flag_name) \
extern bool FLAGS_ ## flag_name
namespace snappy {
static const uint32 kuint32max = static_cast<uint32>(0xFFFFFFFF);
static const int64 kint64max = static_cast<int64>(0x7FFFFFFFFFFFFFFFLL);
// Potentially unaligned loads and stores.
// x86, PowerPC, and ARM64 can simply do these loads and stores native.
#if defined(__i386__) || defined(__x86_64__) || defined(__powerpc__) || \
defined(__aarch64__)
#define UNALIGNED_LOAD16(_p) (*reinterpret_cast<const uint16 *>(_p))
#define UNALIGNED_LOAD32(_p) (*reinterpret_cast<const uint32 *>(_p))
#define UNALIGNED_LOAD64(_p) (*reinterpret_cast<const uint64 *>(_p))
#define UNALIGNED_STORE16(_p, _val) (*reinterpret_cast<uint16 *>(_p) = (_val))
#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.
//
// To further complicate matters, only LDR instructions (single reads) are
// allowed to be unaligned, not LDRD (two reads) or LDM (many reads). Unless we
// explicitly tell the compiler that these accesses can be unaligned, it can and
// will combine accesses. On armcc, the way to signal this is done by accessing
// through the type (uint32 __packed *), but GCC has no such attribute
// (it ignores __attribute__((packed)) on individual variables). However,
// we can tell it that a _struct_ is unaligned, which has the same effect,
// so we do that.
#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__)
#if __GNUC__
#define ATTRIBUTE_PACKED __attribute__((__packed__))
#else
#define ATTRIBUTE_PACKED
#endif
namespace base {
namespace internal {
struct Unaligned16Struct {
uint16 value;
uint8 dummy; // To make the size non-power-of-two.
} ATTRIBUTE_PACKED;
struct Unaligned32Struct {
uint32 value;
uint8 dummy; // To make the size non-power-of-two.
} ATTRIBUTE_PACKED;
} // namespace internal
} // namespace base
#define UNALIGNED_LOAD16(_p) \
((reinterpret_cast<const ::snappy::base::internal::Unaligned16Struct *>(_p))->value)
#define UNALIGNED_LOAD32(_p) \
((reinterpret_cast<const ::snappy::base::internal::Unaligned32Struct *>(_p))->value)
#define UNALIGNED_STORE16(_p, _val) \
((reinterpret_cast< ::snappy::base::internal::Unaligned16Struct *>(_p))->value = \
(_val))
#define UNALIGNED_STORE32(_p, _val) \
((reinterpret_cast< ::snappy::base::internal::Unaligned32Struct *>(_p))->value = \
(_val))
// TODO: 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
// unaligned loads and stores.
inline uint16 UNALIGNED_LOAD16(const void *p) {
uint16 t;
memcpy(&t, p, sizeof t);
return t;
}
inline uint32 UNALIGNED_LOAD32(const void *p) {
uint32 t;
memcpy(&t, p, sizeof t);
return t;
}
inline uint64 UNALIGNED_LOAD64(const void *p) {
uint64 t;
memcpy(&t, p, sizeof t);
return t;
}
inline void UNALIGNED_STORE16(void *p, uint16 v) {
memcpy(p, &v, sizeof v);
}
inline void UNALIGNED_STORE32(void *p, uint32 v) {
memcpy(p, &v, sizeof v);
}
inline void UNALIGNED_STORE64(void *p, uint64 v) {
memcpy(p, &v, sizeof v);
}
#endif
// The following guarantees declaration of the byte swap functions.
#if defined(SNAPPY_IS_BIG_ENDIAN)
#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)
#define bswap_32(x) _byteswap_ulong(x)
#define bswap_64(x) _byteswap_uint64(x)
#elif defined(__APPLE__)
// Mac OS X / Darwin features
#include <libkern/OSByteOrder.h>
#define bswap_16(x) OSSwapInt16(x)
#define bswap_32(x) OSSwapInt32(x)
#define bswap_64(x) OSSwapInt64(x)
#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 // defined(SNAPPY_IS_BIG_ENDIAN)
// Convert to little-endian storage, opposite of network format.
// Convert x from host to little endian: x = LittleEndian.FromHost(x);
// convert x from little endian to host: x = LittleEndian.ToHost(x);
//
// Store values into unaligned memory converting to little endian order:
// LittleEndian.Store16(p, x);
//
// Load unaligned values stored in little endian converting to host order:
// x = LittleEndian.Load16(p);
class LittleEndian {
public:
// Conversion functions.
#if defined(SNAPPY_IS_BIG_ENDIAN)
static uint16 FromHost16(uint16 x) { return bswap_16(x); }
static uint16 ToHost16(uint16 x) { return bswap_16(x); }
static uint32 FromHost32(uint32 x) { return bswap_32(x); }
static uint32 ToHost32(uint32 x) { return bswap_32(x); }
static bool IsLittleEndian() { return false; }
#else // !defined(SNAPPY_IS_BIG_ENDIAN)
static uint16 FromHost16(uint16 x) { return x; }
static uint16 ToHost16(uint16 x) { return x; }
static uint32 FromHost32(uint32 x) { return x; }
static uint32 ToHost32(uint32 x) { return x; }
static bool IsLittleEndian() { return true; }
#endif // !defined(SNAPPY_IS_BIG_ENDIAN)
// Functions to do unaligned loads and stores in little-endian order.
static uint16 Load16(const void *p) {
return ToHost16(UNALIGNED_LOAD16(p));
}
static void Store16(void *p, uint16 v) {
UNALIGNED_STORE16(p, FromHost16(v));
}
static uint32 Load32(const void *p) {
return ToHost32(UNALIGNED_LOAD32(p));
}
static void Store32(void *p, uint32 v) {
UNALIGNED_STORE32(p, FromHost32(v));
}
};
// Some bit-manipulation functions.
class Bits {
public:
// Return floor(log2(n)) for positive integer n.
static int Log2FloorNonZero(uint32 n);
// Return floor(log2(n)) for positive integer n. Returns -1 iff n == 0.
static int Log2Floor(uint32 n);
// Return the first set least / most significant bit, 0-indexed. Returns an
// undefined value if n == 0. FindLSBSetNonZero() is similar to ffs() except
// that it's 0-indexed.
static int FindLSBSetNonZero(uint32 n);
#if defined(ARCH_K8) || defined(ARCH_PPC) || defined(ARCH_ARM)
static int FindLSBSetNonZero64(uint64 n);
#endif // defined(ARCH_K8) || defined(ARCH_PPC) || defined(ARCH_ARM)
private:
// No copying
Bits(const Bits&);
void operator=(const Bits&);
};
#ifdef HAVE_BUILTIN_CTZ
inline int Bits::Log2FloorNonZero(uint32 n) {
assert(n != 0);
// (31 ^ x) is equivalent to (31 - x) for x in [0, 31]. An easy proof
// represents subtraction in base 2 and observes that there's no carry.
//
// GCC and Clang represent __builtin_clz on x86 as 31 ^ _bit_scan_reverse(x).
// Using "31 ^" here instead of "31 -" allows the optimizer to strip the
// function body down to _bit_scan_reverse(x).
return 31 ^ __builtin_clz(n);
}
inline int Bits::Log2Floor(uint32 n) {
return (n == 0) ? -1 : Bits::Log2FloorNonZero(n);
}
inline int Bits::FindLSBSetNonZero(uint32 n) {
assert(n != 0);
return __builtin_ctz(n);
}
#if defined(ARCH_K8) || defined(ARCH_PPC) || defined(ARCH_ARM)
inline int Bits::FindLSBSetNonZero64(uint64 n) {
assert(n != 0);
return __builtin_ctzll(n);
}
#endif // defined(ARCH_K8) || defined(ARCH_PPC) || defined(ARCH_ARM)
#elif defined(_MSC_VER)
inline int Bits::Log2FloorNonZero(uint32 n) {
assert(n != 0);
unsigned long where;
_BitScanReverse(&where, n);
return static_cast<int>(where);
}
inline int Bits::Log2Floor(uint32 n) {
unsigned long where;
if (_BitScanReverse(&where, n))
return static_cast<int>(where);
return -1;
}
inline int Bits::FindLSBSetNonZero(uint32 n) {
assert(n != 0);
unsigned long where;
if (_BitScanForward(&where, n))
return static_cast<int>(where);
return 32;
}
#if defined(ARCH_K8) || defined(ARCH_PPC) || defined(ARCH_ARM)
inline int Bits::FindLSBSetNonZero64(uint64 n) {
assert(n != 0);
unsigned long where;
if (_BitScanForward64(&where, n))
return static_cast<int>(where);
return 64;
}
#endif // defined(ARCH_K8) || defined(ARCH_PPC) || defined(ARCH_ARM)
#else // Portable versions.
inline int Bits::Log2FloorNonZero(uint32 n) {
assert(n != 0);
int log = 0;
uint32 value = n;
for (int i = 4; i >= 0; --i) {
int shift = (1 << i);
uint32 x = value >> shift;
if (x != 0) {
value = x;
log += shift;
}
}
assert(value == 1);
return log;
}
inline int Bits::Log2Floor(uint32 n) {
return (n == 0) ? -1 : Bits::Log2FloorNonZero(n);
}
inline int Bits::FindLSBSetNonZero(uint32 n) {
assert(n != 0);
int rc = 31;
for (int i = 4, shift = 1 << 4; i >= 0; --i) {
const uint32 x = n << shift;
if (x != 0) {
n = x;
rc -= shift;
}
shift >>= 1;
}
return rc;
}
#if defined(ARCH_K8) || defined(ARCH_PPC) || defined(ARCH_ARM)
// FindLSBSetNonZero64() is defined in terms of FindLSBSetNonZero().
inline int Bits::FindLSBSetNonZero64(uint64 n) {
assert(n != 0);
const uint32 bottombits = static_cast<uint32>(n);
if (bottombits == 0) {
// Bottom bits are zero, so scan in top bits
return 32 + FindLSBSetNonZero(static_cast<uint32>(n >> 32));
} else {
return FindLSBSetNonZero(bottombits);
}
}
#endif // defined(ARCH_K8) || defined(ARCH_PPC) || defined(ARCH_ARM)
#endif // End portable versions.
// Variable-length integer encoding.
class Varint {
public:
// Maximum lengths of varint encoding of uint32.
static const int kMax32 = 5;
// Attempts to parse a varint32 from a prefix of the bytes in [ptr,limit-1].
// Never reads a character at or beyond limit. If a valid/terminated varint32
// was found in the range, stores it in *OUTPUT and returns a pointer just
// past the last byte of the varint32. Else returns NULL. On success,
// "result <= limit".
static const char* Parse32WithLimit(const char* ptr, const char* limit,
uint32* OUTPUT);
// REQUIRES "ptr" points to a buffer of length sufficient to hold "v".
// EFFECTS Encodes "v" into "ptr" and returns a pointer to the
// byte just past the last encoded byte.
static char* Encode32(char* ptr, uint32 v);
// EFFECTS Appends the varint representation of "value" to "*s".
static void Append32(string* s, uint32 value);
};
inline const char* Varint::Parse32WithLimit(const char* p,
const char* l,
uint32* OUTPUT) {
const unsigned char* ptr = reinterpret_cast<const unsigned char*>(p);
const unsigned char* limit = reinterpret_cast<const unsigned char*>(l);
uint32 b, result;
if (ptr >= limit) return NULL;
b = *(ptr++); result = b & 127; if (b < 128) goto done;
if (ptr >= limit) return NULL;
b = *(ptr++); result |= (b & 127) << 7; if (b < 128) goto done;
if (ptr >= limit) return NULL;
b = *(ptr++); result |= (b & 127) << 14; if (b < 128) goto done;
if (ptr >= limit) return NULL;
b = *(ptr++); result |= (b & 127) << 21; if (b < 128) goto done;
if (ptr >= limit) return NULL;
b = *(ptr++); result |= (b & 127) << 28; if (b < 16) goto done;
return NULL; // Value is too long to be a varint32
done:
*OUTPUT = result;
return reinterpret_cast<const char*>(ptr);
}
inline char* Varint::Encode32(char* sptr, uint32 v) {
// Operate on characters as unsigneds
unsigned char* ptr = reinterpret_cast<unsigned char*>(sptr);
static const int B = 128;
if (v < (1<<7)) {
*(ptr++) = v;
} else if (v < (1<<14)) {
*(ptr++) = v | B;
*(ptr++) = v>>7;
} else if (v < (1<<21)) {
*(ptr++) = v | B;
*(ptr++) = (v>>7) | B;
*(ptr++) = v>>14;
} else if (v < (1<<28)) {
*(ptr++) = v | B;
*(ptr++) = (v>>7) | B;
*(ptr++) = (v>>14) | B;
*(ptr++) = v>>21;
} else {
*(ptr++) = v | B;
*(ptr++) = (v>>7) | B;
*(ptr++) = (v>>14) | B;
*(ptr++) = (v>>21) | B;
*(ptr++) = v>>28;
}
return reinterpret_cast<char*>(ptr);
}
// If you know the internal layout of the std::string in use, you can
// replace this function with one that resizes the string without
// filling the new space with zeros (if applicable) --
// it will be non-portable but faster.
inline void STLStringResizeUninitialized(string* s, size_t new_size) {
s->resize(new_size);
}
// Return a mutable char* pointing to a string's internal buffer,
// which may not be null-terminated. Writing through this pointer will
// modify the string.
//
// string_as_array(&str)[i] is valid for 0 <= i < str.size() until the
// next call to a string method that invalidates iterators.
//
// As of 2006-04, there is no standard-blessed way of getting a
// mutable reference to a string's internal buffer. However, issue 530
// (http://www.open-std.org/JTC1/SC22/WG21/docs/lwg-defects.html#530)
// proposes this as the method. It will officially be part of the standard
// for C++0x. This should already work on all current implementations.
inline char* string_as_array(string* str) {
return str->empty() ? NULL : &*str->begin();
}
} // namespace snappy
#endif // THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_STUBS_INTERNAL_H_
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