sh-i18n--envsubst.c

   1 /*
   2  * sh-i18n--envsubst.c - a stripped-down version of gettext's envsubst(1)
   3  *
   4  * Copyright (C) 2010 Ævar Arnfjörð Bjarmason
   5  *
   6  * This is a modified version of
   7  * 67d0871a8c:gettext-runtime/src/envsubst.c from the gettext.git
   8  * repository. It has been stripped down to only implement the
   9  * envsubst(1) features that we need in the git-sh-i18n fallbacks.
  10  *
  11  * The "Close standard error" part in main() is from
  12  * 8dac033df0:gnulib-local/lib/closeout.c. The copyright notices for
  13  * both files are reproduced immediately below.
  14  */
  15
  16 #include "git-compat-util.h"
  17
  18 /* Substitution of environment variables in shell format strings.
  19    Copyright (C) 2003-2007 Free Software Foundation, Inc.
  20    Written by Bruno Haible <bruno@clisp.org>, 2003.
  21
  22    This program is free software; you can redistribute it and/or modify
  23    it under the terms of the GNU General Public License as published by
  24    the Free Software Foundation; either version 2, or (at your option)
  25    any later version.
  26
  27    This program is distributed in the hope that it will be useful,
  28    but WITHOUT ANY WARRANTY; without even the implied warranty of
  29    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  30    GNU General Public License for more details.
  31
  32    You should have received a copy of the GNU General Public License
  33    along with this program; if not, write to the Free Software Foundation,
  34    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  35
  36 /* closeout.c - close standard output and standard error
  37    Copyright (C) 1998-2007 Free Software Foundation, Inc.
  38
  39    This program is free software; you can redistribute it and/or modify
  40    it under the terms of the GNU General Public License as published by
  41    the Free Software Foundation; either version 2, or (at your option)
  42    any later version.
  43
  44    This program is distributed in the hope that it will be useful,
  45    but WITHOUT ANY WARRANTY; without even the implied warranty of
  46    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  47    GNU General Public License for more details.
  48
  49    You should have received a copy of the GNU General Public License
  50    along with this program; if not, write to the Free Software Foundation,
  51    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  52
  53 #include <errno.h>
  54 #include <stdio.h>
  55 #include <stdlib.h>
  56 #include <string.h>
  57
  58 /* If true, substitution shall be performed on all variables.  */
  59 static unsigned short int all_variables;
  60
  61 /* Forward declaration of local functions.  */
  62 static void print_variables (const char *string);
  63 static void note_variables (const char *string);
  64 static void subst_from_stdin (void);
  65
  66 int
  67 main (int argc, char *argv[])
  68 {
  69   /* Default values for command line options.  */
  70   /* unsigned short int show_variables = 0; */
  71
  72   switch (argc)
  73         {
  74         case 1:
  75           error ("we won't substitute all variables on stdin for you");
  76           break;
  77           /*
  78           all_variables = 1;
  79       subst_from_stdin ();
  80           */
  81         case 2:
  82           /* echo '$foo and $bar' | git sh-i18n--envsubst --variables '$foo and $bar' */
  83           all_variables = 0;
  84           note_variables (argv[1]);
  85       subst_from_stdin ();
  86           break;
  87         case 3:
  88           /* git sh-i18n--envsubst --variables '$foo and $bar' */
  89           if (strcmp(argv[1], "--variables"))
  90                 error ("first argument must be --variables when two are given");
  91           /* show_variables = 1; */
  92       print_variables (argv[2]);
  93           break;
  94         default:
  95           error ("too many arguments");
  96           break;
  97         }
  98
  99   /* Close standard error.  This is simpler than fwriteerror_no_ebadf, because
 100      upon failure we don't need an errno - all we can do at this point is to
 101      set an exit status.  */
 102   errno = 0;
 103   if (ferror (stderr) || fflush (stderr))
 104     {
 105       fclose (stderr);
 106       exit (EXIT_FAILURE);
 107     }
 108   if (fclose (stderr) && errno != EBADF)
 109     exit (EXIT_FAILURE);
 110
 111   exit (EXIT_SUCCESS);
 112 }
 113
 114 /* Parse the string and invoke the callback each time a $VARIABLE or
 115    ${VARIABLE} construct is seen, where VARIABLE is a nonempty sequence
 116    of ASCII alphanumeric/underscore characters, starting with an ASCII
 117    alphabetic/underscore character.
 118    We allow only ASCII characters, to avoid dependencies w.r.t. the current
 119    encoding: While "${\xe0}" looks like a variable access in ISO-8859-1
 120    encoding, it doesn't look like one in the BIG5, BIG5-HKSCS, GBK, GB18030,
 121    SHIFT_JIS, JOHAB encodings, because \xe0\x7d is a single character in these
 122    encodings.  */
 123 static void
 124 find_variables (const char *string,
 125                 void (*callback) (const char *var_ptr, size_t var_len))
 126 {
 127   for (; *string != '\0';)
 128     if (*string++ == '$')
 129       {
 130         const char *variable_start;
 131         const char *variable_end;
 132         unsigned short int valid;
 133         char c;
 134
 135         if (*string == '{')
 136           string++;
 137
 138         variable_start = string;
 139         c = *string;
 140         if ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || c == '_')
 141           {
 142             do
 143               c = *++string;
 144             while ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z')
 145                    || (c >= '0' && c <= '9') || c == '_');
 146             variable_end = string;
 147
 148             if (variable_start[-1] == '{')
 149               {
 150                 if (*string == '}')
 151                   {
 152                     string++;
 153                     valid = 1;
 154                   }
 155                 else
 156                   valid = 0;
 157               }
 158             else
 159               valid = 1;
 160
 161             if (valid)
 162               callback (variable_start, variable_end - variable_start);
 163           }
 164       }
 165 }
 166
 167
 168 /* Print a variable to stdout, followed by a newline.  */
 169 static void
 170 print_variable (const char *var_ptr, size_t var_len)
 171 {
 172   fwrite (var_ptr, var_len, 1, stdout);
 173   putchar ('\n');
 174 }
 175
 176 /* Print the variables contained in STRING to stdout, each one followed by a
 177    newline.  */
 178 static void
 179 print_variables (const char *string)
 180 {
 181   find_variables (string, &print_variable);
 182 }
 183
 184
 185 /* Type describing list of immutable strings,
 186    implemented using a dynamic array.  */
 187 typedef struct string_list_ty string_list_ty;
 188 struct string_list_ty
 189 {
 190   const char **item;
 191   size_t nitems;
 192   size_t nitems_max;
 193 };
 194
 195 /* Initialize an empty list of strings.  */
 196 static inline void
 197 string_list_init (string_list_ty *slp)
 198 {
 199   slp->item = NULL;
 200   slp->nitems = 0;
 201   slp->nitems_max = 0;
 202 }
 203
 204 /* Append a single string to the end of a list of strings.  */
 205 static inline void
 206 string_list_append (string_list_ty *slp, const char *s)
 207 {
 208   /* Grow the list.  */
 209   if (slp->nitems >= slp->nitems_max)
 210     {
 211       size_t nbytes;
 212
 213       slp->nitems_max = slp->nitems_max * 2 + 4;
 214       nbytes = slp->nitems_max * sizeof (slp->item[0]);
 215       slp->item = (const char **) xrealloc (slp->item, nbytes);
 216     }
 217
 218   /* Add the string to the end of the list.  */
 219   slp->item[slp->nitems++] = s;
 220 }
 221
 222 /* Compare two strings given by reference.  */
 223 static int
 224 cmp_string (const void *pstr1, const void *pstr2)
 225 {
 226   const char *str1 = *(const char **)pstr1;
 227   const char *str2 = *(const char **)pstr2;
 228
 229   return strcmp (str1, str2);
 230 }
 231
 232 /* Sort a list of strings.  */
 233 static inline void
 234 string_list_sort (string_list_ty *slp)
 235 {
 236   if (slp->nitems > 0)
 237     qsort (slp->item, slp->nitems, sizeof (slp->item[0]), cmp_string);
 238 }
 239
 240 /* Test whether a sorted string list contains a given string.  */
 241 static int
 242 sorted_string_list_member (const string_list_ty *slp, const char *s)
 243 {
 244   size_t j1, j2;
 245
 246   j1 = 0;
 247   j2 = slp->nitems;
 248   if (j2 > 0)
 249     {
 250       /* Binary search.  */
 251       while (j2 - j1 > 1)
 252         {
 253           /* Here we know that if s is in the list, it is at an index j
 254              with j1 <= j < j2.  */
 255           size_t j = (j1 + j2) >> 1;
 256           int result = strcmp (slp->item[j], s);
 257
 258           if (result > 0)
 259             j2 = j;
 260           else if (result == 0)
 261             return 1;
 262           else
 263             j1 = j + 1;
 264         }
 265       if (j2 > j1)
 266         if (strcmp (slp->item[j1], s) == 0)
 267           return 1;
 268     }
 269   return 0;
 270 }
 271
 272
 273 /* Set of variables on which to perform substitution.
 274    Used only if !all_variables.  */
 275 static string_list_ty variables_set;
 276
 277 /* Adds a variable to variables_set.  */
 278 static void
 279 note_variable (const char *var_ptr, size_t var_len)
 280 {
 281   char *string = xmemdupz (var_ptr, var_len);
 282
 283   string_list_append (&variables_set, string);
 284 }
 285
 286 /* Stores the variables occurring in the string in variables_set.  */
 287 static void
 288 note_variables (const char *string)
 289 {
 290   string_list_init (&variables_set);
 291   find_variables (string, &note_variable);
 292   string_list_sort (&variables_set);
 293 }
 294
 295
 296 static int
 297 do_getc (void)
 298 {
 299   int c = getc (stdin);
 300
 301   if (c == EOF)
 302     {
 303       if (ferror (stdin))
 304         error ("error while reading standard input");
 305     }
 306
 307   return c;
 308 }
 309
 310 static inline void
 311 do_ungetc (int c)
 312 {
 313   if (c != EOF)
 314     ungetc (c, stdin);
 315 }
 316
 317 /* Copies stdin to stdout, performing substitutions.  */
 318 static void
 319 subst_from_stdin (void)
 320 {
 321   static char *buffer;
 322   static size_t bufmax;
 323   static size_t buflen;
 324   int c;
 325
 326   for (;;)
 327     {
 328       c = do_getc ();
 329       if (c == EOF)
 330         break;
 331       /* Look for $VARIABLE or ${VARIABLE}.  */
 332       if (c == '$')
 333         {
 334           unsigned short int opening_brace = 0;
 335           unsigned short int closing_brace = 0;
 336
 337           c = do_getc ();
 338           if (c == '{')
 339             {
 340               opening_brace = 1;
 341               c = do_getc ();
 342             }
 343           if ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || c == '_')
 344             {
 345               unsigned short int valid;
 346
 347               /* Accumulate the VARIABLE in buffer.  */
 348               buflen = 0;
 349               do
 350                 {
 351                   if (buflen >= bufmax)
 352                     {
 353                       bufmax = 2 * bufmax + 10;
 354                       buffer = xrealloc (buffer, bufmax);
 355                     }
 356                   buffer[buflen++] = c;
 357
 358                   c = do_getc ();
 359                 }
 360               while ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z')
 361                      || (c >= '0' && c <= '9') || c == '_');
 362
 363               if (opening_brace)
 364                 {
 365                   if (c == '}')
 366                     {
 367                       closing_brace = 1;
 368                       valid = 1;
 369                     }
 370                   else
 371                     {
 372                       valid = 0;
 373                       do_ungetc (c);
 374                     }
 375                 }
 376               else
 377                 {
 378                   valid = 1;
 379                   do_ungetc (c);
 380                 }
 381
 382               if (valid)
 383                 {
 384                   /* Terminate the variable in the buffer.  */
 385                   if (buflen >= bufmax)
 386                     {
 387                       bufmax = 2 * bufmax + 10;
 388                       buffer = xrealloc (buffer, bufmax);
 389                     }
 390                   buffer[buflen] = '\0';
 391
 392                   /* Test whether the variable shall be substituted.  */
 393                   if (!all_variables
 394                       && !sorted_string_list_member (&variables_set, buffer))
 395                     valid = 0;
 396                 }
 397
 398               if (valid)
 399                 {
 400                   /* Substitute the variable's value from the environment.  */
 401                   const char *env_value = getenv (buffer);
 402
 403                   if (env_value != NULL)
 404                     fputs (env_value, stdout);
 405                 }
 406               else
 407                 {
 408                   /* Perform no substitution at all.  Since the buffered input
 409                      contains no other '$' than at the start, we can just
 410                      output all the buffered contents.  */
 411                   putchar ('$');
 412                   if (opening_brace)
 413                     putchar ('{');
 414                   fwrite (buffer, buflen, 1, stdout);
 415                   if (closing_brace)
 416                     putchar ('}');
 417                 }
 418             }
 419           else
 420             {
 421               do_ungetc (c);
 422               putchar ('$');
 423               if (opening_brace)
 424                 putchar ('{');
 425             }
 426         }
 427       else
 428         putchar (c);
 429     }
 430 }