string/envz.c

   1 /* Routines for dealing with '\0' separated environment vectors
   2    Copyright (C) 1995-1998,2001,2002,2006 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, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <malloc.h>
  22 #include <string.h>
  23
  24 #include <envz.h>
  25
  26 /* The character separating names from values in an envz.  */
  27 #define SEP '='
  28 \f
  29 /* Returns a pointer to the entry in ENVZ for NAME, or 0 if there is none.
  30    If NAME contains the separator character, only the portion before it is
  31    used in the comparison.  */
  32 char *
  33 envz_entry (const char *envz, size_t envz_len, const char *name)
  34 {
  35   while (envz_len)
  36     {
  37       const char *p = name;
  38       const char *entry = envz; /* Start of this entry. */
  39
  40       /* See how far NAME and ENTRY match.  */
  41       while (envz_len && *p == *envz && *p && *p != SEP)
  42         p++, envz++, envz_len--;
  43
  44       if ((*envz == '\0' || *envz == SEP) && (*p == '\0' || *p == SEP))
  45         /* Bingo! */
  46         return (char *) entry;
  47
  48       /* No match, skip to the next entry.  */
  49       while (envz_len && *envz)
  50         envz++, envz_len--;
  51       if (envz_len)
  52         envz++, envz_len--;     /* skip '\0' */
  53     }
  54
  55   return 0;
  56 }
  57 libc_hidden_def (envz_entry)
  58
  59 /* Returns a pointer to the value portion of the entry in ENVZ for NAME, or 0
  60    if there is none.  */
  61 char *
  62 envz_get (const char *envz, size_t envz_len, const char *name)
  63 {
  64   char *entry = envz_entry (envz, envz_len, name);
  65   if (entry)
  66     {
  67       while (*entry && *entry != SEP)
  68         entry++;
  69       if (*entry)
  70         entry++;
  71       else
  72         entry = 0;              /* A null entry.  */
  73     }
  74   return entry;
  75 }
  76 \f
  77 /* Remove the entry for NAME from ENVZ & ENVZ_LEN, if any.  */
  78 void
  79 envz_remove (char **envz, size_t *envz_len, const char *name)
  80 {
  81   char *entry = envz_entry (*envz, *envz_len, name);
  82   if (entry)
  83     argz_delete (envz, envz_len, entry);
  84 }
  85 libc_hidden_def (envz_remove)
  86
  87 /* Adds an entry for NAME with value VALUE to ENVZ & ENVZ_LEN.  If an entry
  88    with the same name already exists in ENVZ, it is removed.  If VALUE is
  89    NULL, then the new entry will a special null one, for which envz_get will
  90    return NULL, although envz_entry will still return an entry; this is handy
  91    because when merging with another envz, the null entry can override an
  92    entry in the other one.  Null entries can be removed with envz_strip ().  */
  93 error_t
  94 envz_add (char **envz, size_t *envz_len, const char *name, const char *value)
  95 {
  96   envz_remove (envz, envz_len, name);
  97
  98   if (value)
  99     /* Add the new value, if there is one.  */
 100     {
 101       size_t name_len = strlen (name);
 102       size_t value_len = strlen (value);
 103       size_t old_envz_len = *envz_len;
 104       size_t new_envz_len = old_envz_len + name_len + 1 + value_len + 1;
 105       char *new_envz = realloc (*envz, new_envz_len);
 106
 107       if (new_envz)
 108         {
 109           memcpy (new_envz + old_envz_len, name, name_len);
 110           new_envz[old_envz_len + name_len] = SEP;
 111           memcpy (new_envz + old_envz_len + name_len + 1, value, value_len);
 112           new_envz[new_envz_len - 1] = 0;
 113
 114           *envz = new_envz;
 115           *envz_len = new_envz_len;
 116
 117           return 0;
 118         }
 119       else
 120         return ENOMEM;
 121     }
 122   else
 123     /* Add a null entry.  */
 124     return __argz_add (envz, envz_len, name);
 125 }
 126 \f
 127 /* Adds each entry in ENVZ2 to ENVZ & ENVZ_LEN, as if with envz_add().  If
 128    OVERRIDE is true, then values in ENVZ2 will supersede those with the same
 129    name in ENV, otherwise not.  */
 130 error_t
 131 envz_merge (char **envz, size_t *envz_len, const char *envz2,
 132             size_t envz2_len, int override)
 133 {
 134   error_t err = 0;
 135
 136   while (envz2_len && ! err)
 137     {
 138       char *old = envz_entry (*envz, *envz_len, envz2);
 139       size_t new_len = strlen (envz2) + 1;
 140
 141       if (! old)
 142         err = __argz_append (envz, envz_len, envz2, new_len);
 143       else if (override)
 144         {
 145           argz_delete (envz, envz_len, old);
 146           err = __argz_append (envz, envz_len, envz2, new_len);
 147         }
 148
 149       envz2 += new_len;
 150       envz2_len -= new_len;
 151     }
 152
 153   return err;
 154 }
 155
 156 /* Remove null entries.  */
 157 void
 158 envz_strip (char **envz, size_t *envz_len)
 159 {
 160   char *entry = *envz;
 161   size_t left = *envz_len;
 162   while (left)
 163     {
 164       size_t entry_len = strlen (entry) + 1;
 165       left -= entry_len;
 166       if (! strchr (entry, SEP))
 167         /* Null entry. */
 168         memmove (entry, entry + entry_len, left);
 169       else
 170         entry += entry_len;
 171     }
 172   *envz_len = entry - *envz;
 173 }