| 1 | // int_encoding.cc -- variable length and unaligned integer encoding support. |
| 2 | |
| 3 | // Copyright (C) 2009-2020 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 | #include "gold.h" |
| 26 | |
| 27 | #include <vector> |
| 28 | |
| 29 | #include "int_encoding.h" |
| 30 | |
| 31 | namespace gold { |
| 32 | |
| 33 | // Read an unsigned LEB128 number. Each byte contains 7 bits of |
| 34 | // information, plus one bit saying whether the number continues or |
| 35 | // not. BYTE contains the first byte of the number, and is guaranteed |
| 36 | // to have the continuation bit set. |
| 37 | |
| 38 | uint64_t |
| 39 | read_unsigned_LEB_128_x(const unsigned char* buffer, size_t* len, |
| 40 | unsigned char byte) |
| 41 | { |
| 42 | uint64_t result = static_cast<uint64_t>(byte & 0x7f); |
| 43 | size_t num_read = 1; |
| 44 | unsigned int shift = 7; |
| 45 | |
| 46 | do |
| 47 | { |
| 48 | if (num_read > 64 / 7 + 1) |
| 49 | { |
| 50 | gold_warning(_("Unusually large LEB128 decoded, " |
| 51 | "debug information may be corrupted")); |
| 52 | break; |
| 53 | } |
| 54 | byte = *buffer++; |
| 55 | num_read++; |
| 56 | result |= (static_cast<uint64_t>(byte & 0x7f)) << shift; |
| 57 | shift += 7; |
| 58 | } |
| 59 | while (byte & 0x80); |
| 60 | |
| 61 | *len = num_read; |
| 62 | |
| 63 | return result; |
| 64 | } |
| 65 | |
| 66 | // Read a signed LEB128 number. These are like regular LEB128 |
| 67 | // numbers, except the last byte may have a sign bit set. |
| 68 | // BYTE contains the first byte of the number, and is guaranteed |
| 69 | // to have the continuation bit set. |
| 70 | |
| 71 | int64_t |
| 72 | read_signed_LEB_128_x(const unsigned char* buffer, size_t* len, |
| 73 | unsigned char byte) |
| 74 | { |
| 75 | int64_t result = static_cast<uint64_t>(byte & 0x7f); |
| 76 | int shift = 7; |
| 77 | size_t num_read = 1; |
| 78 | |
| 79 | do |
| 80 | { |
| 81 | if (num_read > 64 / 7 + 1) |
| 82 | { |
| 83 | gold_warning(_("Unusually large LEB128 decoded, " |
| 84 | "debug information may be corrupted")); |
| 85 | break; |
| 86 | } |
| 87 | byte = *buffer++; |
| 88 | num_read++; |
| 89 | result |= (static_cast<uint64_t>(byte & 0x7f) << shift); |
| 90 | shift += 7; |
| 91 | } |
| 92 | while (byte & 0x80); |
| 93 | |
| 94 | if ((shift < 8 * static_cast<int>(sizeof(result))) && (byte & 0x40)) |
| 95 | result |= -((static_cast<int64_t>(1)) << shift); |
| 96 | *len = num_read; |
| 97 | return result; |
| 98 | } |
| 99 | |
| 100 | void |
| 101 | write_unsigned_LEB_128(std::vector<unsigned char>* buffer, uint64_t value) |
| 102 | { |
| 103 | do |
| 104 | { |
| 105 | unsigned char current_byte = value & 0x7f; |
| 106 | value >>= 7; |
| 107 | if (value != 0) |
| 108 | { |
| 109 | current_byte |= 0x80; |
| 110 | } |
| 111 | buffer->push_back(current_byte); |
| 112 | } |
| 113 | while (value != 0); |
| 114 | } |
| 115 | |
| 116 | size_t |
| 117 | get_length_as_unsigned_LEB_128(uint64_t value) |
| 118 | { |
| 119 | size_t length = 0; |
| 120 | do |
| 121 | { |
| 122 | unsigned char current_byte = value & 0x7f; |
| 123 | value >>= 7; |
| 124 | if (value != 0) |
| 125 | { |
| 126 | current_byte |= 0x80; |
| 127 | } |
| 128 | length++; |
| 129 | } |
| 130 | while (value != 0); |
| 131 | return length; |
| 132 | } |
| 133 | |
| 134 | } // End namespace gold. |