gold/int_encoding.h

   1 // int_encoding.h -- variable length and unaligned integers -*- C++ -*-
   2
   3 // Copyright (C) 2009-2019 Free Software Foundation, Inc.
   4 // Written by Doug Kwan <dougkwan@google.com> by refactoring scattered
   5 // contents from other files in gold.  Original code written by Ian
   6 // Lance Taylor <iant@google.com> and Caleb Howe  <cshowe@google.com>.
   7
   8 // This file is part of gold.
   9
  10 // This program is free software; you can redistribute it and/or modify
  11 // it under the terms of the GNU General Public License as published by
  12 // the Free Software Foundation; either version 3 of the License, or
  13 // (at your option) any later version.
  14
  15 // This program is distributed in the hope that it will be useful,
  16 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 // GNU General Public License for more details.
  19
  20 // You should have received a copy of the GNU General Public License
  21 // along with this program; if not, write to the Free Software
  22 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  23 // MA 02110-1301, USA.
  24
  25 #ifndef GOLD_INT_ENCODING_H
  26 #define GOLD_INT_ENCODING_H
  27
  28 #include <vector>
  29 #include "elfcpp.h"
  30 #include "target.h"
  31 #include "parameters.h"
  32
  33 namespace gold
  34 {
  35
  36 //
  37 // LEB 128 encoding support.
  38 //
  39
  40 // Read a ULEB 128 encoded integer from BUFFER.  Return the length of the
  41 // encoded integer at the location PLEN.  The common case of a single-byte
  42 // value is handled inline, and multi-byte values are processed by the _x
  43 // routine, where BYTE is the first byte of the value.
  44
  45 uint64_t
  46 read_unsigned_LEB_128_x(const unsigned char* buffer, size_t* plen,
  47                         unsigned char byte);
  48
  49 inline uint64_t
  50 read_unsigned_LEB_128(const unsigned char* buffer, size_t* plen)
  51 {
  52   unsigned char byte = *buffer++;
  53
  54   if ((byte & 0x80) != 0)
  55     return read_unsigned_LEB_128_x(buffer, plen, byte);
  56
  57   *plen = 1;
  58   return static_cast<uint64_t>(byte);
  59 }
  60
  61 // Read an SLEB 128 encoded integer from BUFFER.  Return the length of the
  62 // encoded integer at the location PLEN.  The common case of a single-byte
  63 // value is handled inline, and multi-byte values are processed by the _x
  64 // routine, where BYTE is the first byte of the value.
  65
  66 int64_t
  67 read_signed_LEB_128_x(const unsigned char* buffer, size_t* plen,
  68                       unsigned char byte);
  69
  70 inline int64_t
  71 read_signed_LEB_128(const unsigned char* buffer, size_t* plen)
  72 {
  73   unsigned char byte = *buffer++;
  74
  75   if ((byte & 0x80) != 0)
  76     return read_signed_LEB_128_x(buffer, plen, byte);
  77
  78   *plen = 1;
  79   if (byte & 0x40)
  80     return -(static_cast<int64_t>(1) << 7) | static_cast<int64_t>(byte);
  81   return static_cast<int64_t>(byte);
  82 }
  83
  84 // Write a ULEB 128 encoded VALUE to BUFFER.
  85
  86 void
  87 write_unsigned_LEB_128(std::vector<unsigned char>* buffer, uint64_t value);
  88
  89 // Return the ULEB 128 encoded size of VALUE.
  90
  91 size_t
  92 get_length_as_unsigned_LEB_128(uint64_t value);
  93
  94 //
  95 // Unaligned integer encoding support.
  96 //
  97
  98 // Insert VALSIZE-bit integer VALUE into DESTINATION.
  99
 100 template <int valsize>
 101 void insert_into_vector(std::vector<unsigned char>* destination,
 102                         typename elfcpp::Valtype_base<valsize>::Valtype value)
 103 {
 104   unsigned char buffer[valsize / 8];
 105   if (parameters->target().is_big_endian())
 106     elfcpp::Swap_unaligned<valsize, true>::writeval(buffer, value);
 107   else
 108     elfcpp::Swap_unaligned<valsize, false>::writeval(buffer, value);
 109   destination->insert(destination->end(), buffer, buffer + valsize / 8);
 110 }
 111
 112 // Read a possibly unaligned integer of SIZE from SOURCE.
 113
 114 template <int valsize>
 115 typename elfcpp::Valtype_base<valsize>::Valtype
 116 read_from_pointer(const unsigned char* source)
 117 {
 118   typename elfcpp::Valtype_base<valsize>::Valtype return_value;
 119   if (parameters->target().is_big_endian())
 120     return_value = elfcpp::Swap_unaligned<valsize, true>::readval(source);
 121   else
 122     return_value = elfcpp::Swap_unaligned<valsize, false>::readval(source);
 123   return return_value;
 124 }
 125
 126 // Read a possibly unaligned integer of SIZE.  Update SOURCE after read.
 127
 128 template <int valsize>
 129 typename elfcpp::Valtype_base<valsize>::Valtype
 130 read_from_pointer(unsigned char** source)
 131 {
 132   typename elfcpp::Valtype_base<valsize>::Valtype return_value;
 133   if (parameters->target().is_big_endian())
 134     return_value = elfcpp::Swap_unaligned<valsize, true>::readval(*source);
 135   else
 136     return_value = elfcpp::Swap_unaligned<valsize, false>::readval(*source);
 137   *source += valsize / 8;
 138   return return_value;
 139 }
 140
 141 // Same as the above except for use with const unsigned char data.
 142
 143 template <int valsize>
 144 typename elfcpp::Valtype_base<valsize>::Valtype
 145 read_from_pointer(const unsigned char** source)
 146 {
 147   typename elfcpp::Valtype_base<valsize>::Valtype return_value;
 148   if (parameters->target().is_big_endian())
 149     return_value = elfcpp::Swap_unaligned<valsize, true>::readval(*source);
 150   else
 151     return_value = elfcpp::Swap_unaligned<valsize, false>::readval(*source);
 152   *source += valsize / 8;
 153   return return_value;
 154 }
 155
 156 } // End namespace gold.
 157
 158 #endif // !defined(GOLD_INT_ENCODING_H)