string/envz.c

   1 /* Routines for dealing with '\0' separated environment vectors
   2    Copyright (C) 1995-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <malloc.h>
  20 #include <string.h>
  21
  22 #include <envz.h>
  23
  24 /* The character separating names from values in an envz.  */
  25 #define SEP '='
  26 \f
  27 /* Returns a pointer to the entry in ENVZ for NAME, or 0 if there is none.
  28    If NAME contains the separator character, only the portion before it is
  29    used in the comparison.  */
  30 char *
  31 envz_entry (const char *envz, size_t envz_len, const char *name)
  32 {
  33   while (envz_len)
  34     {
  35       const char *p = name;
  36       const char *entry = envz; /* Start of this entry. */
  37
  38       /* See how far NAME and ENTRY match.  */
  39       while (envz_len && *p == *envz && *p && *p != SEP)
  40         p++, envz++, envz_len--;
  41
  42       if ((*envz == '\0' || *envz == SEP) && (*p == '\0' || *p == SEP))
  43         /* Bingo! */
  44         return (char *) entry;
  45
  46       /* No match, skip to the next entry.  */
  47       while (envz_len && *envz)
  48         envz++, envz_len--;
  49       if (envz_len)
  50         envz++, envz_len--;     /* skip '\0' */
  51     }
  52
  53   return 0;
  54 }
  55 libc_hidden_def (envz_entry)
  56
  57 /* Returns a pointer to the value portion of the entry in ENVZ for NAME, or 0
  58    if there is none.  */
  59 char *
  60 envz_get (const char *envz, size_t envz_len, const char *name)
  61 {
  62   char *entry = envz_entry (envz, envz_len, name);
  63   if (entry)
  64     {
  65       while (*entry && *entry != SEP)
  66         entry++;
  67       if (*entry)
  68         entry++;
  69       else
  70         entry = 0;              /* A null entry.  */
  71     }
  72   return entry;
  73 }
  74 \f
  75 /* Remove the entry for NAME from ENVZ & ENVZ_LEN, if any.  */
  76 void
  77 envz_remove (char **envz, size_t *envz_len, const char *name)
  78 {
  79   char *entry = envz_entry (*envz, *envz_len, name);
  80   if (entry)
  81     argz_delete (envz, envz_len, entry);
  82 }
  83 libc_hidden_def (envz_remove)
  84
  85 /* Adds an entry for NAME with value VALUE to ENVZ & ENVZ_LEN.  If an entry
  86    with the same name already exists in ENVZ, it is removed.  If VALUE is
  87    NULL, then the new entry will a special null one, for which envz_get will
  88    return NULL, although envz_entry will still return an entry; this is handy
  89    because when merging with another envz, the null entry can override an
  90    entry in the other one.  Null entries can be removed with envz_strip ().  */
  91 error_t
  92 envz_add (char **envz, size_t *envz_len, const char *name, const char *value)
  93 {
  94   envz_remove (envz, envz_len, name);
  95
  96   if (value)
  97     /* Add the new value, if there is one.  */
  98     {
  99       size_t name_len = strlen (name);
 100       size_t value_len = strlen (value);
 101       size_t old_envz_len = *envz_len;
 102       size_t new_envz_len = old_envz_len + name_len + 1 + value_len + 1;
 103       char *new_envz = realloc (*envz, new_envz_len);
 104
 105       if (new_envz)
 106         {
 107           memcpy (new_envz + old_envz_len, name, name_len);
 108           new_envz[old_envz_len + name_len] = SEP;
 109           memcpy (new_envz + old_envz_len + name_len + 1, value, value_len);
 110           new_envz[new_envz_len - 1] = 0;
 111
 112           *envz = new_envz;
 113           *envz_len = new_envz_len;
 114
 115           return 0;
 116         }
 117       else
 118         return ENOMEM;
 119     }
 120   else
 121     /* Add a null entry.  */
 122     return __argz_add (envz, envz_len, name);
 123 }
 124 \f
 125 /* Adds each entry in ENVZ2 to ENVZ & ENVZ_LEN, as if with envz_add().  If
 126    OVERRIDE is true, then values in ENVZ2 will supersede those with the same
 127    name in ENV, otherwise not.  */
 128 error_t
 129 envz_merge (char **envz, size_t *envz_len, const char *envz2,
 130             size_t envz2_len, int override)
 131 {
 132   error_t err = 0;
 133
 134   while (envz2_len && ! err)
 135     {
 136       char *old = envz_entry (*envz, *envz_len, envz2);
 137       size_t new_len = strlen (envz2) + 1;
 138
 139       if (! old)
 140         err = __argz_append (envz, envz_len, envz2, new_len);
 141       else if (override)
 142         {
 143           argz_delete (envz, envz_len, old);
 144           err = __argz_append (envz, envz_len, envz2, new_len);
 145         }
 146
 147       envz2 += new_len;
 148       envz2_len -= new_len;
 149     }
 150
 151   return err;
 152 }
 153
 154 /* Remove null entries.  */
 155 void
 156 envz_strip (char **envz, size_t *envz_len)
 157 {
 158   char *entry = *envz;
 159   size_t left = *envz_len;
 160   while (left)
 161     {
 162       size_t entry_len = strlen (entry) + 1;
 163       left -= entry_len;
 164       if (! strchr (entry, SEP))
 165         /* Null entry. */
 166         memmove (entry, entry + entry_len, left);
 167       else
 168         entry += entry_len;
 169     }
 170   *envz_len = entry - *envz;
 171 }