lib/Support/LEB128.cpp

   1 //===- LEB128.cpp - LEB128 utility functions implementation -----*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements some utility functions for encoding SLEB128 and
  11 // ULEB128 values.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/Support/LEB128.h"
  16
  17 namespace llvm {
  18
  19 /// Utility function to get the size of the ULEB128-encoded value.
  20 unsigned getULEB128Size(uint64_t Value) {
  21   unsigned Size = 0;
  22   do {
  23     Value >>= 7;
  24     Size += sizeof(int8_t);
  25   } while (Value);
  26   return Size;
  27 }
  28
  29 /// Utility function to get the size of the SLEB128-encoded value.
  30 unsigned getSLEB128Size(int64_t Value) {
  31   unsigned Size = 0;
  32   int Sign = Value >> (8 * sizeof(Value) - 1);
  33   bool IsMore;
  34
  35   do {
  36     unsigned Byte = Value & 0x7f;
  37     Value >>= 7;
  38     IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
  39     Size += sizeof(int8_t);
  40   } while (IsMore);
  41   return Size;
  42 }
  43
  44 }  // namespace llvm