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//===- llvm/Support/LEB128.h - [SU]LEB128 utility functions -----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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.
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;
if (error)
*error = nullptr;
do {
if (end && p == end) {
if (error)
*error = "malformed uleb128, extends past end";
if (n)
*n = (unsigned)(p - orig_p);
return 0;
}
uint64_t Slice = *p & 0x7f;
if (Shift >= 64 || Slice << Shift >> Shift != Slice) {
if (error)
*error = "uleb128 too big for uint64";
if (n)
*n = (unsigned)(p - orig_p);
return 0;
}
Value += uint64_t(*p & 0x7f) << Shift;
Shift += 7;
} while (*p++ >= 128);
if (n)
*n = (unsigned)(p - orig_p);
return Value;
}
/// Utility function to decode a SLEB128 value.
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 (end && p == end) {
if (error)
*error = "malformed sleb128, extends past end";
if (n)
*n = (unsigned)(p - orig_p);
return 0;
}
Byte = *p++;
Value |= (int64_t(Byte & 0x7f) << Shift);
Shift += 7;
} while (Byte >= 128);
// Sign extend negative numbers.
if (Byte & 0x40)
Value |= (-1ULL) << Shift;
if (n)
*n = (unsigned)(p - orig_p);
return Value;
}
/// 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_SYSTEM_LEB128_H
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