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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 <stdint.h>
+
+#include <cassert>
+#include <cstdlib>
+#include <cstring>
+#include <limits>
+#include <string>
+
+#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"
+
+// Used to enable 64-bit optimized versions of some routines.
+#if defined(__PPC64__) || defined(__powerpc64__)
+#define ARCH_PPC 1
+#elif defined(__aarch64__) || defined(_M_ARM64)
+#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) int{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
+
+// Inlining hints.
+#ifdef HAVE_ATTRIBUTE_ALWAYS_INLINE
+#define SNAPPY_ATTRIBUTE_ALWAYS_INLINE __attribute__((always_inline))
+#else
+#define SNAPPY_ATTRIBUTE_ALWAYS_INLINE
+#endif
+
+// Stubbed version of ABSL_FLAG.
+//
+// In the open source version, flags can only be changed at compile time.
+#define SNAPPY_FLAG(flag_type, flag_name, default_value, help) \
+ flag_type FLAGS_ ## flag_name = default_value
+
+namespace snappy {
+
+// Stubbed version of absl::GetFlag().
+template <typename T>
+inline T GetFlag(T flag) { return flag; }
+
+static const uint32_t kuint32max = std::numeric_limits<uint32_t>::max();
+static const int64_t kint64max = std::numeric_limits<int64_t>::max();
+
+// Potentially unaligned loads and stores.
+
+inline uint16_t UNALIGNED_LOAD16(const void *p) {
+ // Compiles to a single movzx/ldrh on clang/gcc/msvc.
+ uint16_t v;
+ std::memcpy(&v, p, sizeof(v));
+ return v;
+}
+
+inline uint32_t UNALIGNED_LOAD32(const void *p) {
+ // Compiles to a single mov/ldr on clang/gcc/msvc.
+ uint32_t v;
+ std::memcpy(&v, p, sizeof(v));
+ return v;
+}
+
+inline uint64_t UNALIGNED_LOAD64(const void *p) {
+ // Compiles to a single mov/ldr on clang/gcc/msvc.
+ uint64_t v;
+ std::memcpy(&v, p, sizeof(v));
+ return v;
+}
+
+inline void UNALIGNED_STORE16(void *p, uint16_t v) {
+ // Compiles to a single mov/strh on clang/gcc/msvc.
+ std::memcpy(p, &v, sizeof(v));
+}
+
+inline void UNALIGNED_STORE32(void *p, uint32_t v) {
+ // Compiles to a single mov/str on clang/gcc/msvc.
+ std::memcpy(p, &v, sizeof(v));
+}
+
+inline void UNALIGNED_STORE64(void *p, uint64_t v) {
+ // Compiles to a single mov/str on clang/gcc/msvc.
+ std::memcpy(p, &v, sizeof(v));
+}
+
+// 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:
+ // Functions to do unaligned loads and stores in little-endian order.
+ static inline uint16_t Load16(const void *ptr) {
+ const uint8_t* const buffer = reinterpret_cast<const uint8_t*>(ptr);
+
+ // Compiles to a single mov/str on recent clang and gcc.
+ return (static_cast<uint16_t>(buffer[0])) |
+ (static_cast<uint16_t>(buffer[1]) << 8);
+ }
+
+ static inline uint32_t Load32(const void *ptr) {
+ const uint8_t* const buffer = reinterpret_cast<const uint8_t*>(ptr);
+
+ // Compiles to a single mov/str on recent clang and gcc.
+ return (static_cast<uint32_t>(buffer[0])) |
+ (static_cast<uint32_t>(buffer[1]) << 8) |
+ (static_cast<uint32_t>(buffer[2]) << 16) |
+ (static_cast<uint32_t>(buffer[3]) << 24);
+ }
+
+ static inline uint64_t Load64(const void *ptr) {
+ const uint8_t* const buffer = reinterpret_cast<const uint8_t*>(ptr);
+
+ // Compiles to a single mov/str on recent clang and gcc.
+ return (static_cast<uint64_t>(buffer[0])) |
+ (static_cast<uint64_t>(buffer[1]) << 8) |
+ (static_cast<uint64_t>(buffer[2]) << 16) |
+ (static_cast<uint64_t>(buffer[3]) << 24) |
+ (static_cast<uint64_t>(buffer[4]) << 32) |
+ (static_cast<uint64_t>(buffer[5]) << 40) |
+ (static_cast<uint64_t>(buffer[6]) << 48) |
+ (static_cast<uint64_t>(buffer[7]) << 56);
+ }
+
+ static inline void Store16(void *dst, uint16_t value) {
+ uint8_t* const buffer = reinterpret_cast<uint8_t*>(dst);
+
+ // Compiles to a single mov/str on recent clang and gcc.
+ buffer[0] = static_cast<uint8_t>(value);
+ buffer[1] = static_cast<uint8_t>(value >> 8);
+ }
+
+ static void Store32(void *dst, uint32_t value) {
+ uint8_t* const buffer = reinterpret_cast<uint8_t*>(dst);
+
+ // Compiles to a single mov/str on recent clang and gcc.
+ buffer[0] = static_cast<uint8_t>(value);
+ buffer[1] = static_cast<uint8_t>(value >> 8);
+ buffer[2] = static_cast<uint8_t>(value >> 16);
+ buffer[3] = static_cast<uint8_t>(value >> 24);
+ }
+
+ static void Store64(void* dst, uint64_t value) {
+ uint8_t* const buffer = reinterpret_cast<uint8_t*>(dst);
+
+ // Compiles to a single mov/str on recent clang and gcc.
+ buffer[0] = static_cast<uint8_t>(value);
+ buffer[1] = static_cast<uint8_t>(value >> 8);
+ buffer[2] = static_cast<uint8_t>(value >> 16);
+ buffer[3] = static_cast<uint8_t>(value >> 24);
+ buffer[4] = static_cast<uint8_t>(value >> 32);
+ buffer[5] = static_cast<uint8_t>(value >> 40);
+ buffer[6] = static_cast<uint8_t>(value >> 48);
+ buffer[7] = static_cast<uint8_t>(value >> 56);
+ }
+
+ static inline constexpr bool IsLittleEndian() {
+#if defined(SNAPPY_IS_BIG_ENDIAN)
+ return false;
+#else
+ return true;
+#endif // defined(SNAPPY_IS_BIG_ENDIAN)
+ }
+};
+
+// Some bit-manipulation functions.
+class Bits {
+ public:
+ // Return floor(log2(n)) for positive integer n.
+ static int Log2FloorNonZero(uint32_t n);
+
+ // Return floor(log2(n)) for positive integer n. Returns -1 iff n == 0.
+ static int Log2Floor(uint32_t 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_t n);
+
+ static int FindLSBSetNonZero64(uint64_t n);
+
+ private:
+ // No copying
+ Bits(const Bits&);
+ void operator=(const Bits&);
+};
+
+#if defined(HAVE_BUILTIN_CTZ)
+
+inline int Bits::Log2FloorNonZero(uint32_t 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_t n) {
+ return (n == 0) ? -1 : Bits::Log2FloorNonZero(n);
+}
+
+inline int Bits::FindLSBSetNonZero(uint32_t n) {
+ assert(n != 0);
+ return __builtin_ctz(n);
+}
+
+#elif defined(_MSC_VER)
+
+inline int Bits::Log2FloorNonZero(uint32_t n) {
+ assert(n != 0);
+ // NOLINTNEXTLINE(runtime/int): The MSVC intrinsic demands unsigned long.
+ unsigned long where;
+ _BitScanReverse(&where, n);
+ return static_cast<int>(where);
+}
+
+inline int Bits::Log2Floor(uint32_t n) {
+ // NOLINTNEXTLINE(runtime/int): The MSVC intrinsic demands unsigned long.
+ unsigned long where;
+ if (_BitScanReverse(&where, n))
+ return static_cast<int>(where);
+ return -1;
+}
+
+inline int Bits::FindLSBSetNonZero(uint32_t n) {
+ assert(n != 0);
+ // NOLINTNEXTLINE(runtime/int): The MSVC intrinsic demands unsigned long.
+ unsigned long where;
+ if (_BitScanForward(&where, n))
+ return static_cast<int>(where);
+ return 32;
+}
+
+#else // Portable versions.
+
+inline int Bits::Log2FloorNonZero(uint32_t n) {
+ assert(n != 0);
+
+ int log = 0;
+ uint32_t value = n;
+ for (int i = 4; i >= 0; --i) {
+ int shift = (1 << i);
+ uint32_t x = value >> shift;
+ if (x != 0) {
+ value = x;
+ log += shift;
+ }
+ }
+ assert(value == 1);
+ return log;
+}
+
+inline int Bits::Log2Floor(uint32_t n) {
+ return (n == 0) ? -1 : Bits::Log2FloorNonZero(n);
+}
+
+inline int Bits::FindLSBSetNonZero(uint32_t n) {
+ assert(n != 0);
+
+ int rc = 31;
+ for (int i = 4, shift = 1 << 4; i >= 0; --i) {
+ const uint32_t x = n << shift;
+ if (x != 0) {
+ n = x;
+ rc -= shift;
+ }
+ shift >>= 1;
+ }
+ return rc;
+}
+
+#endif // End portable versions.
+
+#if defined(HAVE_BUILTIN_CTZ)
+
+inline int Bits::FindLSBSetNonZero64(uint64_t n) {
+ assert(n != 0);
+ return __builtin_ctzll(n);
+}
+
+#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
+// _BitScanForward64() is only available on x64 and ARM64.
+
+inline int Bits::FindLSBSetNonZero64(uint64_t n) {
+ assert(n != 0);
+ // NOLINTNEXTLINE(runtime/int): The MSVC intrinsic demands unsigned long.
+ unsigned long where;
+ if (_BitScanForward64(&where, n))
+ return static_cast<int>(where);
+ return 64;
+}
+
+#else // Portable version.
+
+// FindLSBSetNonZero64() is defined in terms of FindLSBSetNonZero().
+inline int Bits::FindLSBSetNonZero64(uint64_t n) {
+ assert(n != 0);
+
+ const uint32_t bottombits = static_cast<uint32_t>(n);
+ if (bottombits == 0) {
+ // Bottom bits are zero, so scan the top bits.
+ return 32 + FindLSBSetNonZero(static_cast<uint32_t>(n >> 32));
+ } else {
+ return FindLSBSetNonZero(bottombits);
+ }
+}
+
+#endif // End portable version.
+
+// Variable-length integer encoding.
+class Varint {
+ public:
+ // Maximum lengths of varint encoding of uint32_t.
+ 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_t* 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_t v);
+
+ // EFFECTS Appends the varint representation of "value" to "*s".
+ static void Append32(std::string* s, uint32_t value);
+};
+
+inline const char* Varint::Parse32WithLimit(const char* p,
+ const char* l,
+ uint32_t* OUTPUT) {
+ const unsigned char* ptr = reinterpret_cast<const unsigned char*>(p);
+ const unsigned char* limit = reinterpret_cast<const unsigned char*>(l);
+ uint32_t 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_t v) {
+ // Operate on characters as unsigneds
+ uint8_t* ptr = reinterpret_cast<uint8_t*>(sptr);
+ static const uint8_t B = 128;
+ if (v < (1 << 7)) {
+ *(ptr++) = static_cast<uint8_t>(v);
+ } else if (v < (1 << 14)) {
+ *(ptr++) = static_cast<uint8_t>(v | B);
+ *(ptr++) = static_cast<uint8_t>(v >> 7);
+ } else if (v < (1 << 21)) {
+ *(ptr++) = static_cast<uint8_t>(v | B);
+ *(ptr++) = static_cast<uint8_t>((v >> 7) | B);
+ *(ptr++) = static_cast<uint8_t>(v >> 14);
+ } else if (v < (1 << 28)) {
+ *(ptr++) = static_cast<uint8_t>(v | B);
+ *(ptr++) = static_cast<uint8_t>((v >> 7) | B);
+ *(ptr++) = static_cast<uint8_t>((v >> 14) | B);
+ *(ptr++) = static_cast<uint8_t>(v >> 21);
+ } else {
+ *(ptr++) = static_cast<uint8_t>(v | B);
+ *(ptr++) = static_cast<uint8_t>((v>>7) | B);
+ *(ptr++) = static_cast<uint8_t>((v>>14) | B);
+ *(ptr++) = static_cast<uint8_t>((v>>21) | B);
+ *(ptr++) = static_cast<uint8_t>(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(std::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(std::string* str) {
+ return str->empty() ? NULL : &*str->begin();
+}
+
+} // namespace snappy
+
+#endif // THIRD_PARTY_SNAPPY_OPENSOURCE_SNAPPY_STUBS_INTERNAL_H_
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