diff options
Diffstat (limited to 'third_party/llvm-project/include/llvm/Support/LEB128.h')
| -rw-r--r-- | third_party/llvm-project/include/llvm/Support/LEB128.h | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/third_party/llvm-project/include/llvm/Support/LEB128.h b/third_party/llvm-project/include/llvm/Support/LEB128.h new file mode 100644 index 000000000..a02b83ca9 --- /dev/null +++ b/third_party/llvm-project/include/llvm/Support/LEB128.h @@ -0,0 +1,198 @@ +//===- 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. +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; + if (error) + *error = nullptr; + 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 |= (uint64_t(Byte & 0x7f) << Shift); + Shift += 7; + } while (Byte >= 128); + // Sign extend negative numbers if needed. + if (Shift < 64 && (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 |