1  /* Utilities for reading leb128 values.
       2     Copyright (C) 2012-2023 Free Software Foundation, Inc.
       3  
       4  This file is part of the libiberty library.
       5  Libiberty is free software; you can redistribute it and/or
       6  modify it under the terms of the GNU Library General Public
       7  License as published by the Free Software Foundation; either
       8  version 2 of the License, or (at your option) any later version.
       9  
      10  Libiberty is distributed in the hope that it will be useful,
      11  but WITHOUT ANY WARRANTY; without even the implied warranty of
      12  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13  Library General Public License for more details.
      14  
      15  You should have received a copy of the GNU Library General Public
      16  License along with libiberty; see the file COPYING.LIB.  If not, write
      17  to the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
      18  Boston, MA 02110-1301, USA.  */
      19  
      20  /* The functions defined here can be speed critical.
      21     Since they are all pretty small we keep things simple and just define
      22     them all as "static inline".
      23  
      24     WARNING: This file is used by GDB which is stuck at C90. :-(
      25     Though it can use stdint.h, inttypes.h.
      26     Therefore if you want to add support for "long long" you need
      27     to wrap it in #ifdef CC_HAS_LONG_LONG.  */
      28  
      29  #ifndef LEB128_H
      30  #define LEB128_H
      31  
      32  /* Get a definition for inline.  */
      33  #include "ansidecl.h"
      34  
      35  /* Get a definition for NULL, size_t.  */
      36  #include <stddef.h>
      37  
      38  #ifdef HAVE_STDINT_H
      39  #include <stdint.h>
      40  #endif
      41  #ifdef HAVE_INTTYPES_H
      42  #include <inttypes.h>
      43  #endif
      44  
      45  /* Decode the unsigned LEB128 constant at BUF into the variable pointed to
      46     by R, and return the number of bytes read.
      47     If we read off the end of the buffer, zero is returned,
      48     and nothing is stored in R.
      49  
      50     Note: The result is an int instead of a pointer to the next byte to be
      51     read to avoid const-vs-non-const problems.  */
      52  
      53  static inline size_t
      54  read_uleb128_to_uint64 (const unsigned char *buf, const unsigned char *buf_end,
      55  			uint64_t *r)
      56  {
      57    const unsigned char *p = buf;
      58    unsigned int shift = 0;
      59    uint64_t result = 0;
      60    unsigned char byte;
      61  
      62    while (1)
      63      {
      64        if (p >= buf_end)
      65  	return 0;
      66  
      67        byte = *p++;
      68        result |= ((uint64_t) (byte & 0x7f)) << shift;
      69        if ((byte & 0x80) == 0)
      70  	break;
      71        shift += 7;
      72      }
      73  
      74    *r = result;
      75    return p - buf;
      76  }
      77  
      78  /* Decode the signed LEB128 constant at BUF into the variable pointed to
      79     by R, and return the number of bytes read.
      80     If we read off the end of the buffer, zero is returned,
      81     and nothing is stored in R.
      82  
      83     Note: The result is an int instead of a pointer to the next byte to be
      84     read to avoid const-vs-non-const problems.  */
      85  
      86  static inline size_t
      87  read_sleb128_to_int64 (const unsigned char *buf, const unsigned char *buf_end,
      88  		       int64_t *r)
      89  {
      90    const unsigned char *p = buf;
      91    unsigned int shift = 0;
      92    int64_t result = 0;
      93    unsigned char byte;
      94  
      95    while (1)
      96      {
      97        if (p >= buf_end)
      98  	return 0;
      99  
     100        byte = *p++;
     101        result |= ((uint64_t) (byte & 0x7f)) << shift;
     102        shift += 7;
     103        if ((byte & 0x80) == 0)
     104  	break;
     105      }
     106    if (shift < (sizeof (*r) * 8) && (byte & 0x40) != 0)
     107      result |= -(((uint64_t) 1) << shift);
     108  
     109    *r = result;
     110    return p - buf;
     111  }
     112  
     113  /* Return the number of bytes to read to skip past an LEB128 number in BUF.
     114     If the end isn't found before reaching BUF_END, return zero.
     115  
     116     Note: The result is an int instead of a pointer to the next byte to be
     117     read to avoid const-vs-non-const problems.  */
     118  
     119  static inline size_t
     120  skip_leb128 (const unsigned char *buf, const unsigned char *buf_end)
     121  {
     122    const unsigned char *p = buf;
     123    unsigned char byte;
     124  
     125    while (1)
     126      {
     127        if (p == buf_end)
     128  	return 0;
     129  
     130        byte = *p++;
     131        if ((byte & 0x80) == 0)
     132  	return p - buf;
     133      }
     134  }
     135  
     136  #endif /* LEB128_H */