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//===- 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/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 == 0 ) && ((Byte & 0x40) == 0)) ||
((Value == -1) && ((Byte & 0x40) != 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 == 0 ) && ((Byte & 0x40) == 0)) ||
((Value == -1) && ((Byte & 0x40) != 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 occured. 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 occured. 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);
}
/// Utility function to get the size of the ULEB128-encoded value.
extern unsigned getULEB128Size(uint64_t Value);
/// Utility function to get the size of the SLEB128-encoded value.
extern unsigned getSLEB128Size(int64_t Value);
} // namespace llvm
#endif // LLVM_SUPPORT_LEB128_H
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