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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.
static inline void encodeSLEB128(int64_t Value, raw_ostream &OS) {
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))));
if (More)
Byte |= 0x80; // Mark this byte that that more bytes will follow.
OS << char(Byte);
} while (More);
}
/// Utility function to encode a ULEB128 value to an output stream.
static inline void encodeULEB128(uint64_t Value, raw_ostream &OS,
unsigned Padding = 0) {
do {
uint8_t Byte = Value & 0x7f;
Value >>= 7;
if (Value != 0 || Padding != 0)
Byte |= 0x80; // Mark this byte that that more bytes will follow.
OS << char(Byte);
} while (Value != 0);
// Pad with 0x80 and emit a null byte at the end.
if (Padding != 0) {
for (; Padding != 1; --Padding)
OS << '\x80';
OS << '\x00';
}
}
/// Utility function to encode a ULEB128 value to a buffer. Returns
/// the length in bytes of the encoded value.
static inline unsigned encodeULEB128(uint64_t Value, uint8_t *p,
unsigned Padding = 0) {
uint8_t *orig_p = p;
do {
uint8_t Byte = Value & 0x7f;
Value >>= 7;
if (Value != 0 || Padding != 0)
Byte |= 0x80; // Mark this byte that that more bytes will follow.
*p++ = Byte;
} while (Value != 0);
// Pad with 0x80 and emit a null byte at the end.
if (Padding != 0) {
for (; Padding != 1; --Padding)
*p++ = '\x80';
*p++ = '\x00';
}
return (unsigned)(p - orig_p);
}
/// Utility function to decode a ULEB128 value.
static inline uint64_t decodeULEB128(const uint8_t *p, unsigned *n = 0) {
const uint8_t *orig_p = p;
uint64_t Value = 0;
unsigned Shift = 0;
do {
Value += (*p & 0x7f) << Shift;
Shift += 7;
} while (*p++ >= 128);
if (n)
*n = (unsigned)(p - orig_p);
return Value;
}
} // namespace llvm
#endif // LLVM_SYSTEM_LEB128_H
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