llvm-6502/include/llvm/Support/LEB128.h
2014-09-17 18:23:07 +00:00

122 lines
3.4 KiB
C++

//===- 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.
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 to show that more bytes will follow.
OS << char(Byte);
} while (More);
}
/// Utility function to encode a ULEB128 value to an output stream.
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 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 (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.
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 to show 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.
inline uint64_t decodeULEB128(const uint8_t *p, unsigned *n = nullptr) {
const uint8_t *orig_p = p;
uint64_t Value = 0;
unsigned Shift = 0;
do {
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 *orig_p = p;
int64_t Value = 0;
unsigned Shift = 0;
uint8_t Byte;
do {
Byte = *p++;
Value |= ((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