mdw@git.distorted.org.uk Git - mLib/blob - sys/env.c

   1 /* -*-c-*-
   2  *
   3  * Fiddling with environment variables
   4  *
   5  * (c) 1999 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of the mLib utilities library.
  11  *
  12  * mLib is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * mLib is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with mLib; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 /*----- Header files ------------------------------------------------------*/
  29
  30 #include <stdio.h>
  31 #include <stdlib.h>
  32 #include <string.h>
  33
  34 #include "alloc.h"
  35 #include "sym.h"
  36
  37 /*----- Data structures ---------------------------------------------------*/
  38
  39 typedef struct var {
  40   sym_base _base;
  41   char *v;
  42 } var;
  43
  44 /*----- Main code ---------------------------------------------------------*/
  45
  46 /* --- @env_get@ --- *
  47  *
  48  * Arguments:   @sym_table *t@ = pointer to a symbol table
  49  *              @const char *name@ = pointer to variable name to look up
  50  *
  51  * Returns:     Pointer to corresponding value string, or null.
  52  *
  53  * Use:         Looks up an environment variable in the table and returns its
  54  *              value.  If the variable can't be found, a null pointer is
  55  *              returned.
  56  */
  57
  58 char *env_get(sym_table *t, const char *name)
  59 {
  60   var *e = sym_find(t, name, -1, 0, 0);
  61   return (e ? e->v : 0);
  62 }
  63
  64 /* --- @env_put@ --- *
  65  *
  66  * Arguments:   @sym_table *t@ = pointer to a symbol table
  67  *              @const char *name@ = pointer to variable name to set
  68  *              @const char *value@ = pointer to value string to assign
  69  *
  70  * Returns:     ---
  71  *
  72  * Use:         Assigns a value to a variable.  If the @name@ contains an
  73  *              equals character, then it's assumed to be of the form
  74  *              `VAR=VALUE' and @value@ argument is ignored.  Otherwise, if
  75  *              @value@ is null, the variable is deleted.  Finally, the
  76  *              normal case: @name@ is a plain name, and @value@ is a normal
  77  *              string causes the variable to be assigned the value in the
  78  *              way you'd expect.
  79  */
  80
  81 void env_put(sym_table *t, const char *name, const char *value)
  82 {
  83   char *q = 0;
  84
  85   /* --- Sort out the mess with `NAME=VALUE' forms --- */
  86
  87   {
  88     size_t eq = strcspn(name, "=");
  89     if (name[eq] == '=') {
  90       q = x_alloc(t->t.a, eq + 1);
  91       memcpy(q, name, eq);
  92       q[eq] = 0;
  93       value = name + eq + 1;
  94       name = q;
  95     }
  96   }
  97
  98   /* --- Read the current value --- */
  99
 100   if (!value) {
 101     var *v;
 102     if ((v = sym_find(t, name, -1, 0, 0)) != 0) {
 103       x_free(t->t.a, v->v);
 104       sym_remove(t, v);
 105     }
 106   } else {
 107     unsigned found;
 108     var *v = sym_find(t, name, -1, sizeof(*v), &found);
 109     if (found)
 110       x_free(t->t.a, v->v);
 111     v->v = x_strdup(t->t.a, value);
 112   }
 113
 114   /* --- Tidying --- */
 115
 116   if (q)
 117     xfree(q);
 118 }
 119
 120 /* --- @env_import@ --- *
 121  *
 122  * Arguments:   @sym_table *t@ = pointer to a symbol table
 123  *              @char **env@ = pointer to an environment list
 124  *
 125  * Returns:     ---
 126  *
 127  * Use:         Inserts all of the environment variables listed into a symbol
 128  *              table for rapid access.  Equivalent to a lot of calls to
 129  *              @env_put@.
 130  */
 131
 132 void env_import(sym_table *t, char **env)
 133 {
 134   while (*env) {
 135     env_put(t, *env, 0);
 136     env++;
 137   }
 138 }
 139
 140 /* --- @env_export@ --- *
 141  *
 142  * Arguments:   @sym_table *t@ = pointer to a symbol table
 143  *
 144  * Returns:     A big environment list.
 145  *
 146  * Use:         Extracts an environment table from a symbol table
 147  *              representation of an environment.  The table and all of the
 148  *              strings are in one big block allocated from the heap.
 149  */
 150
 151 char **env_export(sym_table *t)
 152 {
 153   size_t n = 1;
 154   size_t sz = 0;
 155   sym_iter i;
 156   var *v;
 157   char **env;
 158   char *p, **pp;
 159
 160   /* --- Work out sizes for everything --- */
 161
 162   for (sym_mkiter(&i, t); (v = sym_next(&i)) != 0; ) {
 163     n++;
 164     sz += SYM_LEN(v) + strlen(v->v) + 2;
 165   }
 166
 167   /* --- Allocate the big chunk of memory --- */
 168
 169   env = pp = xmalloc(n * sizeof(char *) + sz);
 170   p = (char *)(env + n);
 171
 172   /* --- Dump the output in the big chunk of memory --- */
 173
 174   for (sym_mkiter(&i, t); (v = sym_next(&i)) != 0; ) {
 175     const char *name = SYM_NAME(v);
 176     size_t nlen = strlen(name), vlen = strlen(v->v);
 177     *pp++ = p;
 178     memcpy(p, name, nlen); p += nlen;
 179     *p++ = '=';
 180     memcpy(p, v->v, vlen); p += vlen;
 181     *p++ = 0;
 182   }
 183   *pp++ = 0;
 184   return (env);
 185 }
 186
 187 /* --- @env_destroy@ --- *
 188  *
 189  * Arguments:   @sym_table *t@ = pointer to symbol table
 190  *
 191  * Returns:     ---
 192  *
 193  * Use:         Destroys all the variables in the symbol table.
 194  */
 195
 196 void env_destroy(sym_table *t)
 197 {
 198   sym_iter i;
 199   var *v;
 200
 201   for (sym_mkiter(&i, t); (v = sym_next(&i)) != 0; )
 202     x_free(t->t.a, v->v);
 203   sym_destroy(t);
 204 }
 205
 206 /*----- That's all, folks -------------------------------------------------*/