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1 /* Utilities for reading leb128 values.
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145
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2 Copyright (C) 2012-2020 Free Software Foundation, Inc.
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111
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3
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4 This file is part of the libiberty library.
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5 Libiberty is free software; you can redistribute it and/or
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6 modify it under the terms of the GNU Library General Public
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7 License as published by the Free Software Foundation; either
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8 version 2 of the License, or (at your option) any later version.
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9
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10 Libiberty is distributed in the hope that it will be useful,
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 Library General Public License for more details.
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14
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15 You should have received a copy of the GNU Library General Public
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16 License along with libiberty; see the file COPYING.LIB. If not, write
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17 to the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
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18 Boston, MA 02110-1301, USA. */
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19
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20 /* The functions defined here can be speed critical.
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21 Since they are all pretty small we keep things simple and just define
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22 them all as "static inline".
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23
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24 WARNING: This file is used by GDB which is stuck at C90. :-(
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25 Though it can use stdint.h, inttypes.h.
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26 Therefore if you want to add support for "long long" you need
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27 to wrap it in #ifdef CC_HAS_LONG_LONG. */
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28
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29 #ifndef LEB128_H
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30 #define LEB128_H
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31
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32 /* Get a definition for inline. */
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33 #include "ansidecl.h"
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34
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35 /* Get a definition for NULL, size_t. */
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36 #include <stddef.h>
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37
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38 #ifdef HAVE_STDINT_H
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39 #include <stdint.h>
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40 #endif
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41 #ifdef HAVE_INTTYPES_H
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42 #include <inttypes.h>
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43 #endif
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44
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45 /* Decode the unsigned LEB128 constant at BUF into the variable pointed to
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46 by R, and return the number of bytes read.
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47 If we read off the end of the buffer, zero is returned,
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48 and nothing is stored in R.
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49
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50 Note: The result is an int instead of a pointer to the next byte to be
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51 read to avoid const-vs-non-const problems. */
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52
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53 static inline size_t
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54 read_uleb128_to_uint64 (const unsigned char *buf, const unsigned char *buf_end,
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55 uint64_t *r)
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56 {
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57 const unsigned char *p = buf;
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58 unsigned int shift = 0;
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59 uint64_t result = 0;
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60 unsigned char byte;
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61
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62 while (1)
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63 {
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64 if (p >= buf_end)
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65 return 0;
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66
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67 byte = *p++;
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68 result |= ((uint64_t) (byte & 0x7f)) << shift;
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69 if ((byte & 0x80) == 0)
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70 break;
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71 shift += 7;
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72 }
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73
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74 *r = result;
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75 return p - buf;
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76 }
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77
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78 /* Decode the signed LEB128 constant at BUF into the variable pointed to
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79 by R, and return the number of bytes read.
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80 If we read off the end of the buffer, zero is returned,
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81 and nothing is stored in R.
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82
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83 Note: The result is an int instead of a pointer to the next byte to be
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84 read to avoid const-vs-non-const problems. */
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85
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86 static inline size_t
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87 read_sleb128_to_int64 (const unsigned char *buf, const unsigned char *buf_end,
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88 int64_t *r)
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89 {
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90 const unsigned char *p = buf;
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91 unsigned int shift = 0;
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92 int64_t result = 0;
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93 unsigned char byte;
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94
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95 while (1)
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96 {
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97 if (p >= buf_end)
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98 return 0;
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99
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100 byte = *p++;
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101 result |= ((uint64_t) (byte & 0x7f)) << shift;
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102 shift += 7;
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103 if ((byte & 0x80) == 0)
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104 break;
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105 }
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106 if (shift < (sizeof (*r) * 8) && (byte & 0x40) != 0)
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107 result |= -(((uint64_t) 1) << shift);
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108
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109 *r = result;
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110 return p - buf;
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111 }
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112
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113 /* Return the number of bytes to read to skip past an LEB128 number in BUF.
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114 If the end isn't found before reaching BUF_END, return zero.
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115
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116 Note: The result is an int instead of a pointer to the next byte to be
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117 read to avoid const-vs-non-const problems. */
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118
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119 static inline size_t
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120 skip_leb128 (const unsigned char *buf, const unsigned char *buf_end)
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121 {
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122 const unsigned char *p = buf;
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123 unsigned char byte;
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124
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125 while (1)
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126 {
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127 if (p == buf_end)
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128 return 0;
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129
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130 byte = *p++;
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131 if ((byte & 0x80) == 0)
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132 return p - buf;
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133 }
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134 }
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135
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136 #endif /* LEB128_H */
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