string/envz.c

   1 /* Routines for dealing with '\0' separated environment vectors
   2    Copyright (C) 1995-2020 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Written by Miles Bader <miles@gnu.org>
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 #include <malloc.h>
  21 #include <string.h>
  22
  23 #include <envz.h>
  24
  25 /* The character separating names from values in an envz.  */
  26 #define SEP '='
  27 \f
  28 /* Returns a pointer to the entry in ENVZ for NAME, or 0 if there is none.
  29    If NAME contains the separator character, only the portion before it is
  30    used in the comparison.  */
  31 char *
  32 envz_entry (const char *envz, size_t envz_len, const char *name)
  33 {
  34   while (envz_len)
  35     {
  36       const char *p = name;
  37       const char *entry = envz; /* Start of this entry. */
  38
  39       /* See how far NAME and ENTRY match.  */
  40       while (envz_len && *p == *envz && *p && *p != SEP)
  41         p++, envz++, envz_len--;
  42
  43       if ((*envz == '\0' || *envz == SEP) && (*p == '\0' || *p == SEP))
  44         /* Bingo! */
  45         return (char *) entry;
  46
  47       /* No match, skip to the next entry.  */
  48       while (envz_len && *envz)
  49         envz++, envz_len--;
  50       if (envz_len)
  51         envz++, envz_len--;     /* skip '\0' */
  52     }
  53
  54   return 0;
  55 }
  56 libc_hidden_def (envz_entry)
  57
  58 /* Returns a pointer to the value portion of the entry in ENVZ for NAME, or 0
  59    if there is none.  */
  60 char *
  61 envz_get (const char *envz, size_t envz_len, const char *name)
  62 {
  63   char *entry = envz_entry (envz, envz_len, name);
  64   if (entry)
  65     {
  66       while (*entry && *entry != SEP)
  67         entry++;
  68       if (*entry)
  69         entry++;
  70       else
  71         entry = 0;              /* A null entry.  */
  72     }
  73   return entry;
  74 }
  75 \f
  76 /* Remove the entry for NAME from ENVZ & ENVZ_LEN, if any.  */
  77 void
  78 envz_remove (char **envz, size_t *envz_len, const char *name)
  79 {
  80   char *entry = envz_entry (*envz, *envz_len, name);
  81   if (entry)
  82     argz_delete (envz, envz_len, entry);
  83 }
  84 libc_hidden_def (envz_remove)
  85
  86 /* Adds an entry for NAME with value VALUE to ENVZ & ENVZ_LEN.  If an entry
  87    with the same name already exists in ENVZ, it is removed.  If VALUE is
  88    NULL, then the new entry will a special null one, for which envz_get will
  89    return NULL, although envz_entry will still return an entry; this is handy
  90    because when merging with another envz, the null entry can override an
  91    entry in the other one.  Null entries can be removed with envz_strip ().  */
  92 error_t
  93 envz_add (char **envz, size_t *envz_len, const char *name, const char *value)
  94 {
  95   envz_remove (envz, envz_len, name);
  96
  97   if (value)
  98     /* Add the new value, if there is one.  */
  99     {
 100       size_t name_len = strlen (name);
 101       size_t value_len = strlen (value);
 102       size_t old_envz_len = *envz_len;
 103       size_t new_envz_len = old_envz_len + name_len + 1 + value_len + 1;
 104       char *new_envz = realloc (*envz, new_envz_len);
 105
 106       if (new_envz)
 107         {
 108           memcpy (new_envz + old_envz_len, name, name_len);
 109           new_envz[old_envz_len + name_len] = SEP;
 110           memcpy (new_envz + old_envz_len + name_len + 1, value, value_len);
 111           new_envz[new_envz_len - 1] = 0;
 112
 113           *envz = new_envz;
 114           *envz_len = new_envz_len;
 115
 116           return 0;
 117         }
 118       else
 119         return ENOMEM;
 120     }
 121   else
 122     /* Add a null entry.  */
 123     return __argz_add (envz, envz_len, name);
 124 }
 125 \f
 126 /* Adds each entry in ENVZ2 to ENVZ & ENVZ_LEN, as if with envz_add().  If
 127    OVERRIDE is true, then values in ENVZ2 will supersede those with the same
 128    name in ENV, otherwise not.  */
 129 error_t
 130 envz_merge (char **envz, size_t *envz_len, const char *envz2,
 131             size_t envz2_len, int override)
 132 {
 133   error_t err = 0;
 134
 135   while (envz2_len && ! err)
 136     {
 137       char *old = envz_entry (*envz, *envz_len, envz2);
 138       size_t new_len = strlen (envz2) + 1;
 139
 140       if (! old)
 141         err = __argz_append (envz, envz_len, envz2, new_len);
 142       else if (override)
 143         {
 144           argz_delete (envz, envz_len, old);
 145           err = __argz_append (envz, envz_len, envz2, new_len);
 146         }
 147
 148       envz2 += new_len;
 149       envz2_len -= new_len;
 150     }
 151
 152   return err;
 153 }
 154
 155 /* Remove null entries.  */
 156 void
 157 envz_strip (char **envz, size_t *envz_len)
 158 {
 159   char *entry = *envz;
 160   size_t left = *envz_len;
 161   while (left)
 162     {
 163       size_t entry_len = strlen (entry) + 1;
 164       left -= entry_len;
 165       if (! strchr (entry, SEP))
 166         /* Null entry. */
 167         memmove (entry, entry + entry_len, left);
 168       else
 169         entry += entry_len;
 170     }
 171   *envz_len = entry - *envz;
 172 }