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// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#ifndef RUNTIME_PLATFORM_UTILS_H_
#define RUNTIME_PLATFORM_UTILS_H_
#include <limits>
#include <type_traits>
#include "platform/assert.h"
#include "platform/globals.h"
namespace dart {
class Utils {
public:
template <typename T>
static inline T Minimum(T x, T y) {
return x < y ? x : y;
}
template <typename T>
static inline T Maximum(T x, T y) {
return x > y ? x : y;
}
// Calculates absolute value of a given signed integer.
// `x` must not be equal to minimum value representable by `T`
// as its absolute value is out of range.
template <typename T>
static inline T Abs(T x) {
// Note: as a general rule, it is not OK to use STL in Dart VM.
// However, std::numeric_limits<T>::min() and max() are harmless
// and worthwhile exception from this rule.
ASSERT(x != std::numeric_limits<T>::min());
if (x < 0) return -x;
return x;
}
// Calculates absolute value of a given signed integer with saturation.
// If `x` equals to minimum value representable by `T`, then
// absolute value is saturated to the maximum value representable by `T`.
template <typename T>
static inline T AbsWithSaturation(T x) {
if (x < 0) {
// Note: as a general rule, it is not OK to use STL in Dart VM.
// However, std::numeric_limits<T>::min() and max() are harmless
// and worthwhile exception from this rule.
if (x == std::numeric_limits<T>::min()) {
return std::numeric_limits<T>::max();
}
return -x;
}
return x;
}
template <typename T>
static inline bool IsPowerOfTwo(T x) {
return ((x & (x - 1)) == 0) && (x != 0);
}
template <typename T>
static inline int ShiftForPowerOfTwo(T x) {
ASSERT(IsPowerOfTwo(x));
int num_shifts = 0;
while (x > 1) {
num_shifts++;
x = x >> 1;
}
return num_shifts;
}
template <typename T>
static inline bool IsAligned(T x, intptr_t n) {
ASSERT(IsPowerOfTwo(n));
return (x & (n - 1)) == 0;
}
template <typename T>
static inline bool IsAligned(T* x, intptr_t n) {
return IsAligned(reinterpret_cast<uword>(x), n);
}
template <typename T>
static inline T RoundDown(T x, intptr_t n) {
ASSERT(IsPowerOfTwo(n));
return (x & -n);
}
template <typename T>
static inline T* RoundDown(T* x, intptr_t n) {
return reinterpret_cast<T*>(RoundDown(reinterpret_cast<uword>(x), n));
}
template <typename T>
static inline T RoundUp(T x, intptr_t n) {
return RoundDown(x + n - 1, n);
}
template <typename T>
static inline T* RoundUp(T* x, intptr_t n) {
return reinterpret_cast<T*>(RoundUp(reinterpret_cast<uword>(x), n));
}
static uintptr_t RoundUpToPowerOfTwo(uintptr_t x);
static int CountOneBits32(uint32_t x) {
// Apparently there are x64 chips without popcount.
#if __GNUC__ && !defined(HOST_ARCH_IA32) && !defined(HOST_ARCH_X64)
return __builtin_popcount(x);
#else
// Implementation is from "Hacker's Delight" by Henry S. Warren, Jr.,
// figure 5-2, page 66, where the function is called pop.
x = x - ((x >> 1) & 0x55555555);
x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
x = (x + (x >> 4)) & 0x0F0F0F0F;
x = x + (x >> 8);
x = x + (x >> 16);
return static_cast<int>(x & 0x0000003F);
#endif
}
static int CountOneBits64(uint64_t x) {
// Apparently there are x64 chips without popcount.
#if __GNUC__ && !defined(HOST_ARCH_IA32) && !defined(HOST_ARCH_X64)
return __builtin_popcountll(x);
#else
return CountOneBits32(static_cast<uint32_t>(x)) +
CountOneBits32(static_cast<uint32_t>(x >> 32));
#endif
}
static int CountOneBitsWord(uword x) {
#ifdef ARCH_IS_64_BIT
return CountOneBits64(x);
#else
return CountOneBits32(x);
#endif
}
static int HighestBit(int64_t v);
static int BitLength(int64_t value) {
// Flip bits if negative (-1 becomes 0).
value ^= value >> (8 * sizeof(value) - 1);
return (value == 0) ? 0 : (Utils::HighestBit(value) + 1);
}
static int CountLeadingZeros(uword x);
static int CountTrailingZeros(uword x);
// Computes a hash value for the given string.
static uint32_t StringHash(const char* data, int length);
// Computes a hash value for the given word.
static uint32_t WordHash(intptr_t key);
// Check whether an N-bit two's-complement representation can hold value.
template <typename T>
static inline bool IsInt(int N, T value) {
ASSERT((0 < N) &&
(static_cast<unsigned int>(N) < (kBitsPerByte * sizeof(value))));
T limit = static_cast<T>(1) << (N - 1);
return (-limit <= value) && (value < limit);
}
template <typename T>
static inline bool IsUint(int N, T value) {
ASSERT((0 < N) &&
(static_cast<unsigned int>(N) < (kBitsPerByte * sizeof(value))));
T limit = static_cast<T>(1) << N;
return (0 <= value) && (value < limit);
}
// Check whether the magnitude of value fits in N bits, i.e., whether an
// (N+1)-bit sign-magnitude representation can hold value.
template <typename T>
static inline bool IsAbsoluteUint(int N, T value) {
ASSERT((0 < N) &&
(static_cast<unsigned int>(N) < (kBitsPerByte * sizeof(value))));
if (value < 0) value = -value;
return IsUint(N, value);
}
static inline int32_t Low16Bits(int32_t value) {
return static_cast<int32_t>(value & 0xffff);
}
static inline int32_t High16Bits(int32_t value) {
return static_cast<int32_t>(value >> 16);
}
static inline int32_t Low32Bits(int64_t value) {
return static_cast<int32_t>(value);
}
static inline int32_t High32Bits(int64_t value) {
return static_cast<int32_t>(value >> 32);
}
static inline int64_t LowHighTo64Bits(uint32_t low, int32_t high) {
return (static_cast<int64_t>(high) << 32) | (low & 0x0ffffffffLL);
}
static bool IsDecimalDigit(char c) { return ('0' <= c) && (c <= '9'); }
static bool IsHexDigit(char c) {
return IsDecimalDigit(c) || (('A' <= c) && (c <= 'F')) ||
(('a' <= c) && (c <= 'f'));
}
static int HexDigitToInt(char c) {
ASSERT(IsHexDigit(c));
if (IsDecimalDigit(c)) return c - '0';
if (('A' <= c) && (c <= 'F')) return 10 + (c - 'A');
return 10 + (c - 'a');
}
static char IntToHexDigit(int i) {
ASSERT(0 <= i && i < 16);
if (i < 10) return static_cast<char>('0' + i);
return static_cast<char>('A' + (i - 10));
}
// Perform a range check, checking if
// offset + count <= length
// without the risk of integer overflow.
static inline bool RangeCheck(intptr_t offset,
intptr_t count,
intptr_t length) {
return offset >= 0 && count >= 0 && length >= 0 &&
count <= (length - offset);
}
static inline bool WillAddOverflow(int64_t a, int64_t b) {
return ((b > 0) && (a > (kMaxInt64 - b))) ||
((b < 0) && (a < (kMinInt64 - b)));
}
static inline bool WillSubOverflow(int64_t a, int64_t b) {
return ((b > 0) && (a < (kMinInt64 + b))) ||
((b < 0) && (a > (kMaxInt64 + b)));
}
// Adds two int64_t values with wrapping around
// (two's complement arithmetic).
static inline int64_t AddWithWrapAround(int64_t a, int64_t b) {
// Avoid undefined behavior by doing arithmetic in the unsigned type.
return static_cast<int64_t>(static_cast<uint64_t>(a) +
static_cast<uint64_t>(b));
}
// Subtracts two int64_t values with wrapping around
// (two's complement arithmetic).
static inline int64_t SubWithWrapAround(int64_t a, int64_t b) {
// Avoid undefined behavior by doing arithmetic in the unsigned type.
return static_cast<int64_t>(static_cast<uint64_t>(a) -
static_cast<uint64_t>(b));
}
// Multiplies two int64_t values with wrapping around
// (two's complement arithmetic).
static inline int64_t MulWithWrapAround(int64_t a, int64_t b) {
// Avoid undefined behavior by doing arithmetic in the unsigned type.
return static_cast<int64_t>(static_cast<uint64_t>(a) *
static_cast<uint64_t>(b));
}
// Shifts int64_t value left. Supports any non-negative number of bits and
// silently discards shifted out bits.
static inline int64_t ShiftLeftWithTruncation(int64_t a, int64_t b) {
ASSERT(b >= 0);
if (b >= kBitsPerInt64) {
return 0;
}
// Avoid undefined behavior by doing arithmetic in the unsigned type.
return static_cast<int64_t>(static_cast<uint64_t>(a) << b);
}
// Utility functions for converting values from host endianness to
// big or little endian values.
static uint16_t HostToBigEndian16(uint16_t host_value);
static uint32_t HostToBigEndian32(uint32_t host_value);
static uint64_t HostToBigEndian64(uint64_t host_value);
static uint16_t HostToLittleEndian16(uint16_t host_value);
static uint32_t HostToLittleEndian32(uint32_t host_value);
static uint64_t HostToLittleEndian64(uint64_t host_value);
static uint32_t BigEndianToHost32(uint32_t be_value) {
// Going between Host <-> BE is the same operation for all practical
// purposes.
return HostToBigEndian32(be_value);
}
static bool DoublesBitEqual(const double a, const double b) {
return bit_cast<int64_t, double>(a) == bit_cast<int64_t, double>(b);
}
// A double-to-integer conversion that avoids undefined behavior.
// Out of range values and NaNs are converted to minimum value
// for type T.
template <typename T>
static T SafeDoubleToInt(double v) {
const double min = static_cast<double>(std::numeric_limits<T>::min());
const double max = static_cast<double>(std::numeric_limits<T>::max());
return (min <= v && v <= max) ? static_cast<T>(v)
: std::numeric_limits<T>::min();
}
// dart2js represents integers as double precision floats, which can
// represent anything in the range -2^53 ... 2^53.
static bool IsJavascriptInt(int64_t value) {
return ((-0x20000000000000LL <= value) && (value <= 0x20000000000000LL));
}
// The lowest n bits are 1, the others are 0.
static uword NBitMask(uint32_t n) {
ASSERT(n <= kBitsPerWord);
if (n == kBitsPerWord) {
#if defined(TARGET_ARCH_X64)
return 0xffffffffffffffffll;
#else
return 0xffffffff;
#endif
}
return (1ll << n) - 1;
}
static word SignedNBitMask(uint32_t n) {
uword mask = NBitMask(n);
return bit_cast<word>(mask);
}
static uword Bit(uint32_t n) {
ASSERT(n < kBitsPerWord);
uword bit = 1;
return bit << n;
}
// Decode integer in SLEB128 format from |data| and update |byte_index|.
template <typename ValueType>
static ValueType DecodeSLEB128(const uint8_t* data,
const intptr_t data_length,
intptr_t* byte_index) {
ASSERT(*byte_index < data_length);
uword shift = 0;
ValueType value = 0;
uint8_t part = 0;
do {
part = data[(*byte_index)++];
value |= static_cast<ValueType>(part & 0x7f) << shift;
shift += 7;
} while ((part & 0x80) != 0);
if ((shift < (sizeof(ValueType) * CHAR_BIT)) && ((part & 0x40) != 0)) {
using Unsigned = typename std::make_unsigned<ValueType>::type;
const Unsigned kMax = std::numeric_limits<Unsigned>::max();
value |= static_cast<ValueType>(kMax << shift);
}
return value;
}
static char* StrError(int err, char* buffer, size_t bufsize);
// Not all platforms support strndup.
static char* StrNDup(const char* s, intptr_t n);
static intptr_t StrNLen(const char* s, intptr_t n);
// Print formatted output info a buffer.
//
// Does not write more than size characters (including the trailing '\0').
//
// Returns the number of characters (excluding the trailing '\0')
// that would been written if the buffer had been big enough. If
// the return value is greater or equal than the given size then the
// output has been truncated. The return value is never negative.
//
// The buffer will always be terminated by a '\0', unless the buffer
// is of size 0. The buffer might be NULL if the size is 0.
//
// This specification conforms to C99 standard which is implemented
// by glibc 2.1+ with one exception: the C99 standard allows a
// negative return value. We will terminate the vm rather than let
// that occur.
static int SNPrint(char* str, size_t size, const char* format, ...)
PRINTF_ATTRIBUTE(3, 4);
static int VSNPrint(char* str, size_t size, const char* format, va_list args);
};
} // namespace dart
#if defined(HOST_OS_ANDROID)
#include "platform/utils_android.h"
#elif defined(HOST_OS_FUCHSIA)
#include "platform/utils_fuchsia.h"
#elif defined(HOST_OS_LINUX)
#include "platform/utils_linux.h"
#elif defined(HOST_OS_MACOS)
#include "platform/utils_macos.h"
#elif defined(HOST_OS_WINDOWS)
#include "platform/utils_win.h"
#else
#error Unknown target os.
#endif
#endif // RUNTIME_PLATFORM_UTILS_H_