258 lines
7.6 KiB
C++
258 lines
7.6 KiB
C++
//===- llvm/Support/LEB128.h - [SU]LEB128 utility functions -----*- C++ -*-===//
|
|
//
|
|
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
|
|
// See https://llvm.org/LICENSE.txt for license information.
|
|
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file declares some utility functions for encoding SLEB128 and
|
|
// ULEB128 values.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#ifndef LLVM_SUPPORT_LEB128_H
|
|
#define LLVM_SUPPORT_LEB128_H
|
|
|
|
#include "llvm/Support/Compiler.h"
|
|
#include "llvm/Support/raw_ostream.h"
|
|
|
|
namespace llvm {
|
|
|
|
/// Utility function to encode a SLEB128 value to an output stream. Returns
|
|
/// the length in bytes of the encoded value.
|
|
inline unsigned encodeSLEB128(int64_t Value, raw_ostream &OS,
|
|
unsigned PadTo = 0) {
|
|
bool More;
|
|
unsigned Count = 0;
|
|
do {
|
|
uint8_t Byte = Value & 0x7f;
|
|
// NOTE: this assumes that this signed shift is an arithmetic right shift.
|
|
Value >>= 7;
|
|
More = Value != ((Byte & 0x40) ? -1 : 0);
|
|
Count++;
|
|
if (More || Count < PadTo)
|
|
Byte |= 0x80; // Mark this byte to show that more bytes will follow.
|
|
OS << char(Byte);
|
|
} while (More);
|
|
|
|
// Pad with 0x80 and emit a terminating byte at the end.
|
|
if (Count < PadTo) {
|
|
uint8_t PadValue = Value < 0 ? 0x7f : 0x00;
|
|
for (; Count < PadTo - 1; ++Count)
|
|
OS << char(PadValue | 0x80);
|
|
OS << char(PadValue);
|
|
Count++;
|
|
}
|
|
return Count;
|
|
}
|
|
|
|
/// Utility function to encode a SLEB128 value to a buffer. Returns
|
|
/// the length in bytes of the encoded value.
|
|
inline unsigned encodeSLEB128(int64_t Value, uint8_t *p, unsigned PadTo = 0) {
|
|
uint8_t *orig_p = p;
|
|
unsigned Count = 0;
|
|
bool More;
|
|
do {
|
|
uint8_t Byte = Value & 0x7f;
|
|
// NOTE: this assumes that this signed shift is an arithmetic right shift.
|
|
Value >>= 7;
|
|
More = Value != ((Byte & 0x40) ? -1 : 0);
|
|
Count++;
|
|
if (More || Count < PadTo)
|
|
Byte |= 0x80; // Mark this byte to show that more bytes will follow.
|
|
*p++ = Byte;
|
|
} while (More);
|
|
|
|
// Pad with 0x80 and emit a terminating byte at the end.
|
|
if (Count < PadTo) {
|
|
uint8_t PadValue = Value < 0 ? 0x7f : 0x00;
|
|
for (; Count < PadTo - 1; ++Count)
|
|
*p++ = (PadValue | 0x80);
|
|
*p++ = PadValue;
|
|
}
|
|
return (unsigned)(p - orig_p);
|
|
}
|
|
|
|
/// Utility function to encode a ULEB128 value to an output stream. Returns
|
|
/// the length in bytes of the encoded value.
|
|
inline unsigned encodeULEB128(uint64_t Value, raw_ostream &OS,
|
|
unsigned PadTo = 0) {
|
|
unsigned Count = 0;
|
|
do {
|
|
uint8_t Byte = Value & 0x7f;
|
|
Value >>= 7;
|
|
Count++;
|
|
if (Value != 0 || Count < PadTo)
|
|
Byte |= 0x80; // Mark this byte to show that more bytes will follow.
|
|
OS << char(Byte);
|
|
} while (Value != 0);
|
|
|
|
// Pad with 0x80 and emit a null byte at the end.
|
|
if (Count < PadTo) {
|
|
for (; Count < PadTo - 1; ++Count)
|
|
OS << '\x80';
|
|
OS << '\x00';
|
|
Count++;
|
|
}
|
|
return Count;
|
|
}
|
|
|
|
/// Utility function to encode a ULEB128 value to a buffer. Returns
|
|
/// the length in bytes of the encoded value.
|
|
inline unsigned encodeULEB128(uint64_t Value, uint8_t *p,
|
|
unsigned PadTo = 0) {
|
|
uint8_t *orig_p = p;
|
|
unsigned Count = 0;
|
|
do {
|
|
uint8_t Byte = Value & 0x7f;
|
|
Value >>= 7;
|
|
Count++;
|
|
if (Value != 0 || Count < PadTo)
|
|
Byte |= 0x80; // Mark this byte to show that more bytes will follow.
|
|
*p++ = Byte;
|
|
} while (Value != 0);
|
|
|
|
// Pad with 0x80 and emit a null byte at the end.
|
|
if (Count < PadTo) {
|
|
for (; Count < PadTo - 1; ++Count)
|
|
*p++ = '\x80';
|
|
*p++ = '\x00';
|
|
}
|
|
|
|
return (unsigned)(p - orig_p);
|
|
}
|
|
|
|
/// Utility function to decode a ULEB128 value.
|
|
///
|
|
/// If \p error is non-null, it will point to a static error message,
|
|
/// if an error occurred. It will not be modified on success.
|
|
inline uint64_t decodeULEB128(const uint8_t *p, unsigned *n = nullptr,
|
|
const uint8_t *end = nullptr,
|
|
const char **error = nullptr) {
|
|
const uint8_t *orig_p = p;
|
|
uint64_t Value = 0;
|
|
unsigned Shift = 0;
|
|
do {
|
|
if (LLVM_UNLIKELY(p == end)) {
|
|
if (error)
|
|
*error = "malformed uleb128, extends past end";
|
|
Value = 0;
|
|
break;
|
|
}
|
|
uint64_t Slice = *p & 0x7f;
|
|
if (LLVM_UNLIKELY(Shift >= 63) &&
|
|
((Shift == 63 && (Slice << Shift >> Shift) != Slice) ||
|
|
(Shift > 63 && Slice != 0))) {
|
|
if (error)
|
|
*error = "uleb128 too big for uint64";
|
|
Value = 0;
|
|
break;
|
|
}
|
|
Value += Slice << Shift;
|
|
Shift += 7;
|
|
} while (*p++ >= 128);
|
|
if (n)
|
|
*n = (unsigned)(p - orig_p);
|
|
return Value;
|
|
}
|
|
|
|
/// Utility function to decode a SLEB128 value.
|
|
///
|
|
/// If \p error is non-null, it will point to a static error message,
|
|
/// if an error occurred. It will not be modified on success.
|
|
inline int64_t decodeSLEB128(const uint8_t *p, unsigned *n = nullptr,
|
|
const uint8_t *end = nullptr,
|
|
const char **error = nullptr) {
|
|
const uint8_t *orig_p = p;
|
|
int64_t Value = 0;
|
|
unsigned Shift = 0;
|
|
uint8_t Byte;
|
|
do {
|
|
if (LLVM_UNLIKELY(p == end)) {
|
|
if (error)
|
|
*error = "malformed sleb128, extends past end";
|
|
if (n)
|
|
*n = (unsigned)(p - orig_p);
|
|
return 0;
|
|
}
|
|
Byte = *p;
|
|
uint64_t Slice = Byte & 0x7f;
|
|
if (LLVM_UNLIKELY(Shift >= 63) &&
|
|
((Shift == 63 && Slice != 0 && Slice != 0x7f) ||
|
|
(Shift > 63 && Slice != (Value < 0 ? 0x7f : 0x00)))) {
|
|
if (error)
|
|
*error = "sleb128 too big for int64";
|
|
if (n)
|
|
*n = (unsigned)(p - orig_p);
|
|
return 0;
|
|
}
|
|
Value |= Slice << Shift;
|
|
Shift += 7;
|
|
++p;
|
|
} while (Byte >= 128);
|
|
// Sign extend negative numbers if needed.
|
|
if (Shift < 64 && (Byte & 0x40))
|
|
Value |= UINT64_MAX << Shift;
|
|
if (n)
|
|
*n = (unsigned)(p - orig_p);
|
|
return Value;
|
|
}
|
|
|
|
inline uint64_t decodeULEB128AndInc(const uint8_t *&p, const uint8_t *end,
|
|
const char **error = nullptr) {
|
|
unsigned n;
|
|
auto ret = decodeULEB128(p, &n, end, error);
|
|
p += n;
|
|
return ret;
|
|
}
|
|
|
|
inline int64_t decodeSLEB128AndInc(const uint8_t *&p, const uint8_t *end,
|
|
const char **error = nullptr) {
|
|
unsigned n;
|
|
auto ret = decodeSLEB128(p, &n, end, error);
|
|
p += n;
|
|
return ret;
|
|
}
|
|
|
|
inline uint64_t decodeULEB128AndIncUnsafe(const uint8_t *&p) {
|
|
return decodeULEB128AndInc(p, nullptr);
|
|
}
|
|
|
|
/// Overwrite a ULEB128 value and keep the original length.
|
|
inline uint64_t overwriteULEB128(uint8_t *bufLoc, uint64_t val) {
|
|
while (*bufLoc & 0x80) {
|
|
*bufLoc++ = 0x80 | (val & 0x7f);
|
|
val >>= 7;
|
|
}
|
|
*bufLoc = val;
|
|
return val;
|
|
}
|
|
|
|
enum class LEB128Sign { Unsigned, Signed };
|
|
|
|
template <LEB128Sign Sign, typename T, typename U = char,
|
|
unsigned MaxLEB128SizeBytes = 16>
|
|
inline void appendLEB128(SmallVectorImpl<U> &Buffer, T Value) {
|
|
static_assert(sizeof(U) == 1, "Expected buffer of bytes");
|
|
unsigned LEB128ValueSize;
|
|
U TmpBuffer[MaxLEB128SizeBytes];
|
|
if constexpr (Sign == LEB128Sign::Signed)
|
|
LEB128ValueSize =
|
|
encodeSLEB128(Value, reinterpret_cast<uint8_t *>(TmpBuffer));
|
|
else
|
|
LEB128ValueSize =
|
|
encodeULEB128(Value, reinterpret_cast<uint8_t *>(TmpBuffer));
|
|
Buffer.append(TmpBuffer, TmpBuffer + LEB128ValueSize);
|
|
}
|
|
|
|
/// Utility function to get the size of the ULEB128-encoded value.
|
|
LLVM_ABI extern unsigned getULEB128Size(uint64_t Value);
|
|
|
|
/// Utility function to get the size of the SLEB128-encoded value.
|
|
LLVM_ABI extern unsigned getSLEB128Size(int64_t Value);
|
|
|
|
} // namespace llvm
|
|
|
|
#endif // LLVM_SUPPORT_LEB128_H
|