func_env.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2010, Digium, Inc.
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief Environment related dialplan functions
 *
 * \ingroup functions
 */

/*** MODULEINFO
   <support_level>core</support_level>
 ***/

#include "asterisk.h"

#include <sys/stat.h>   /* stat(2) */

#include "asterisk/module.h"
#include "asterisk/channel.h"
#include "asterisk/pbx.h"
#include "asterisk/utils.h"
#include "asterisk/app.h"
#include "asterisk/file.h"

/*** DOCUMENTATION
   <function name="ENV" language="en_US">
      <synopsis>
         Gets or sets the environment variable specified.
      </synopsis>
      <syntax>
         <parameter name="varname" required="true">
            <para>Environment variable name</para>
         </parameter>
      </syntax>
      <description>
         <para>Variables starting with <literal>AST_</literal> are reserved to the system and may not be set.</para>
      </description>
   </function>
   <function name="STAT" language="en_US">
      <synopsis>
         Does a check on the specified file.
      </synopsis>
      <syntax>
         <parameter name="flag" required="true">
            <para>Flag may be one of the following:</para>
            <para>d - Checks if the file is a directory.</para>
            <para>e - Checks if the file exists.</para>
            <para>f - Checks if the file is a regular file.</para>
            <para>m - Returns the file mode (in octal)</para>
            <para>s - Returns the size (in bytes) of the file</para>
            <para>A - Returns the epoch at which the file was last accessed.</para>
            <para>C - Returns the epoch at which the inode was last changed.</para>
            <para>M - Returns the epoch at which the file was last modified.</para>
         </parameter>
         <parameter name="filename" required="true" />
      </syntax>
      <description>
         <note>
            <para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
            is set to <literal>no</literal>, this function can only be executed from the
            dialplan, and not directly from external protocols.</para>
         </note>
      </description>
   </function>
   <function name="FILE" language="en_US">
      <synopsis>
         Read or write text file.
      </synopsis>
      <syntax>
         <parameter name="filename" required="true" />
         <parameter name="offset">
            <para>Maybe specified as any number. If negative, <replaceable>offset</replaceable> specifies the number
            of bytes back from the end of the file.</para>
         </parameter>
         <parameter name="length">
            <para>If specified, will limit the length of the data read to that size. If negative,
            trims <replaceable>length</replaceable> bytes from the end of the file.</para>
         </parameter>
         <parameter name="options">
            <optionlist>
               <option name="l">
                  <para>Line mode:  offset and length are assumed to be
                  measured in lines, instead of byte offsets.</para>
               </option>
               <option name="a">
                  <para>In write mode only, the append option is used to
                  append to the end of the file, instead of overwriting
                  the existing file.</para>
               </option>
               <option name="d">
                  <para>In write mode and line mode only, this option does
                  not automatically append a newline string to the end of
                  a value.  This is useful for deleting lines, instead of
                  setting them to blank.</para>
               </option>
            </optionlist>
         </parameter>
         <parameter name="format">
            <para>The <replaceable>format</replaceable> parameter may be
            used to delimit the type of line terminators in line mode.</para>
            <optionlist>
               <option name="u">
                  <para>Unix newline format.</para>
               </option>
               <option name="d">
                  <para>DOS newline format.</para>
               </option>
               <option name="m">
                  <para>Macintosh newline format.</para>
               </option>
            </optionlist>
         </parameter>
      </syntax>
      <description>
         <para>Read and write text file in character and line mode.</para>
         <para>Examples:</para>
         <para/>
         <para>Read mode (byte):</para>
         <para>    ;reads the entire content of the file.</para>
         <para>    Set(foo=${FILE(/tmp/test.txt)})</para>
         <para>    ;reads from the 11th byte to the end of the file (i.e. skips the first 10).</para>
         <para>    Set(foo=${FILE(/tmp/test.txt,10)})</para>
         <para>    ;reads from the 11th to 20th byte in the file (i.e. skip the first 10, then read 10 bytes).</para>
         <para>    Set(foo=${FILE(/tmp/test.txt,10,10)})</para>
         <para/>
         <para>Read mode (line):</para>
         <para>    ; reads the 3rd line of the file.</para>
         <para>    Set(foo=${FILE(/tmp/test.txt,3,1,l)})</para>
         <para>    ; reads the 3rd and 4th lines of the file.</para>
         <para>    Set(foo=${FILE(/tmp/test.txt,3,2,l)})</para>
         <para>    ; reads from the third line to the end of the file.</para>
         <para>    Set(foo=${FILE(/tmp/test.txt,3,,l)})</para>
         <para>    ; reads the last three lines of the file.</para>
         <para>    Set(foo=${FILE(/tmp/test.txt,-3,,l)})</para>
         <para>    ; reads the 3rd line of a DOS-formatted file.</para>
         <para>    Set(foo=${FILE(/tmp/test.txt,3,1,l,d)})</para>
         <para/>
         <para>Write mode (byte):</para>
         <para>    ; truncate the file and write "bar"</para>
         <para>    Set(FILE(/tmp/test.txt)=bar)</para>
         <para>    ; Append "bar"</para>
         <para>    Set(FILE(/tmp/test.txt,,,a)=bar)</para>
         <para>    ; Replace the first byte with "bar" (replaces 1 character with 3)</para>
         <para>    Set(FILE(/tmp/test.txt,0,1)=bar)</para>
         <para>    ; Replace 10 bytes beginning at the 21st byte of the file with "bar"</para>
         <para>    Set(FILE(/tmp/test.txt,20,10)=bar)</para>
         <para>    ; Replace all bytes from the 21st with "bar"</para>
         <para>    Set(FILE(/tmp/test.txt,20)=bar)</para>
         <para>    ; Insert "bar" after the 4th character</para>
         <para>    Set(FILE(/tmp/test.txt,4,0)=bar)</para>
         <para/>
         <para>Write mode (line):</para>
         <para>    ; Replace the first line of the file with "bar"</para>
         <para>    Set(FILE(/tmp/foo.txt,0,1,l)=bar)</para>
         <para>    ; Replace the last line of the file with "bar"</para>
         <para>    Set(FILE(/tmp/foo.txt,-1,,l)=bar)</para>
         <para>    ; Append "bar" to the file with a newline</para>
         <para>    Set(FILE(/tmp/foo.txt,,,al)=bar)</para>
         <note>
            <para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
            is set to <literal>no</literal>, this function can only be executed from the
            dialplan, and not directly from external protocols.</para>
         </note>
      </description>
      <see-also>
         <ref type="function">FILE_COUNT_LINE</ref>
         <ref type="function">FILE_FORMAT</ref>
      </see-also>
   </function>
   <function name="FILE_COUNT_LINE" language="en_US">
      <synopsis>
         Obtains the number of lines of a text file.
      </synopsis>
      <syntax>
         <parameter name="filename" required="true" />
         <parameter name="format">
            <para>Format may be one of the following:</para>
            <optionlist>
               <option name="u">
                  <para>Unix newline format.</para>
               </option>
               <option name="d">
                  <para>DOS newline format.</para>
               </option>
               <option name="m">
                  <para>Macintosh newline format.</para>
               </option>
            </optionlist>
            <note><para>If not specified, an attempt will be made to determine the newline format type.</para></note>
         </parameter>
      </syntax>
      <description>
         <para>Returns the number of lines, or <literal>-1</literal> on error.</para>
         <note>
            <para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
            is set to <literal>no</literal>, this function can only be executed from the
            dialplan, and not directly from external protocols.</para>
         </note>
      </description>
      <see-also>
         <ref type="function">FILE</ref>
         <ref type="function">FILE_FORMAT</ref>
      </see-also>
   </function>
   <function name="FILE_FORMAT" language="en_US">
      <synopsis>
         Return the newline format of a text file.
      </synopsis>
      <syntax>
         <parameter name="filename" required="true" />
      </syntax>
      <description>
         <para>Return the line terminator type:</para>
         <para>'u' - Unix "\n" format</para>
         <para>'d' - DOS "\r\n" format</para>
         <para>'m' - Macintosh "\r" format</para>
         <para>'x' - Cannot be determined</para>
         <note>
            <para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
            is set to <literal>no</literal>, this function can only be executed from the
            dialplan, and not directly from external protocols.</para>
         </note>
      </description>
      <see-also>
         <ref type="function">FILE</ref>
         <ref type="function">FILE_COUNT_LINE</ref>
      </see-also>
   </function>
 ***/

static int env_read(struct ast_channel *chan, const char *cmd, char *data,
         char *buf, size_t len)
{
   char *ret = NULL;

   *buf = '\0';

   if (data)
      ret = getenv(data);

   if (ret)
      ast_copy_string(buf, ret, len);

   return 0;
}

static int env_write(struct ast_channel *chan, const char *cmd, char *data,
          const char *value)
{
   if (!ast_strlen_zero(data) && strncmp(data, "AST_", 4)) {
      if (!ast_strlen_zero(value)) {
         setenv(data, value, 1);
      } else {
         unsetenv(data);
      }
   }

   return 0;
}

static int stat_read(struct ast_channel *chan, const char *cmd, char *data,
          char *buf, size_t len)
{
   char *action;
   struct stat s;

   ast_copy_string(buf, "0", len);

   action = strsep(&data, ",");
   if (stat(data, &s)) {
      return 0;
   } else {
      switch (*action) {
      case 'e':
         strcpy(buf, "1");
         break;
      case 's':
         snprintf(buf, len, "%u", (unsigned int) s.st_size);
         break;
      case 'f':
         snprintf(buf, len, "%d", S_ISREG(s.st_mode) ? 1 : 0);
         break;
      case 'd':
         snprintf(buf, len, "%d", S_ISDIR(s.st_mode) ? 1 : 0);
         break;
      case 'M':
         snprintf(buf, len, "%d", (int) s.st_mtime);
         break;
      case 'A':
         snprintf(buf, len, "%d", (int) s.st_mtime);
         break;
      case 'C':
         snprintf(buf, len, "%d", (int) s.st_ctime);
         break;
      case 'm':
         snprintf(buf, len, "%o", (unsigned int) s.st_mode);
         break;
      }
   }

   return 0;
}

enum file_format {
   FF_UNKNOWN = -1,
   FF_UNIX,
   FF_DOS,
   FF_MAC,
};

static int64_t count_lines(const char *filename, enum file_format newline_format)
{
   int count = 0;
   char fbuf[4096];
   FILE *ff;

   if (!(ff = fopen(filename, "r"))) {
      ast_log(LOG_ERROR, "Unable to open '%s': %s\n", filename, strerror(errno));
      return -1;
   }

   while (fgets(fbuf, sizeof(fbuf), ff)) {
      char *next = fbuf, *first_cr = NULL, *first_nl = NULL;

      /* Must do it this way, because if the fileformat is FF_MAC, then Unix
       * assumptions about line-format will not come into play. */
      while (next) {
         if (newline_format == FF_DOS || newline_format == FF_MAC || newline_format == FF_UNKNOWN) {
            first_cr = strchr(next, '\r');
         }
         if (newline_format == FF_UNIX || newline_format == FF_UNKNOWN) {
            first_nl = strchr(next, '\n');
         }

         /* No terminators found in buffer */
         if (!first_cr && !first_nl) {
            break;
         }

         if (newline_format == FF_UNKNOWN) {
            if ((first_cr && !first_nl) || (first_cr && first_cr < first_nl)) {
               if (first_nl && first_nl == first_cr + 1) {
                  newline_format = FF_DOS;
               } else if (first_cr && first_cr == &fbuf[sizeof(fbuf) - 2]) {
                  /* Get it on the next pass */
                  fseek(ff, -1, SEEK_CUR);
                  break;
               } else {
                  newline_format = FF_MAC;
                  first_nl = NULL;
               }
            } else {
               newline_format = FF_UNIX;
               first_cr = NULL;
            }
            /* Jump down into next section */
         }

         if (newline_format == FF_DOS) {
            if (first_nl && first_cr && first_nl == first_cr + 1) {
               next = first_nl + 1;
               count++;
            } else if (first_cr == &fbuf[sizeof(fbuf) - 2]) {
               /* Get it on the next pass */
               fseek(ff, -1, SEEK_CUR);
               break;
            }
         } else if (newline_format == FF_MAC) {
            if (first_cr) {
               next = first_cr + 1;
               count++;
            }
         } else if (newline_format == FF_UNIX) {
            if (first_nl) {
               next = first_nl + 1;
               count++;
            }
         }
      }
   }
   fclose(ff);

   return count;
}

static int file_count_line(struct ast_channel *chan, const char *cmd, char *data, struct ast_str **buf, ssize_t len)
{
   enum file_format newline_format = FF_UNKNOWN;
   int64_t count;
   AST_DECLARE_APP_ARGS(args,
      AST_APP_ARG(filename);
      AST_APP_ARG(format);
   );

   AST_STANDARD_APP_ARGS(args, data);
   if (args.argc > 1) {
      if (tolower(args.format[0]) == 'd') {
         newline_format = FF_DOS;
      } else if (tolower(args.format[0]) == 'm') {
         newline_format = FF_MAC;
      } else if (tolower(args.format[0]) == 'u') {
         newline_format = FF_UNIX;
      }
   }

   count = count_lines(args.filename, newline_format);
   ast_str_set(buf, len, "%" PRId64, count);
   return 0;
}

#define LINE_COUNTER(cptr, term, counter) \
   if (*cptr == '\n' && term == FF_UNIX) { \
      counter++; \
   } else if (*cptr == '\n' && term == FF_DOS && dos_state == 0) { \
      dos_state = 1; \
   } else if (*cptr == '\r' && term == FF_DOS && dos_state == 1) { \
      dos_state = 0; \
      counter++; \
   } else if (*cptr == '\r' && term == FF_MAC) { \
      counter++; \
   } else if (term == FF_DOS) { \
      dos_state = 0; \
   }

static enum file_format file2format(const char *filename)
{
   FILE *ff;
   char fbuf[4096];
   char *first_cr, *first_nl;
   enum file_format newline_format = FF_UNKNOWN;

   if (!(ff = fopen(filename, "r"))) {
      ast_log(LOG_ERROR, "Cannot open '%s': %s\n", filename, strerror(errno));
      return -1;
   }

   while (fgets(fbuf, sizeof(fbuf), ff)) {
      first_cr = strchr(fbuf, '\r');
      first_nl = strchr(fbuf, '\n');

      if (!first_cr && !first_nl) {
         continue;
      }

      if ((first_cr && !first_nl) || (first_cr && first_cr < first_nl)) {

         if (first_nl && first_nl == first_cr + 1) {
            newline_format = FF_DOS;
         } else if (first_cr && first_cr == &fbuf[sizeof(fbuf) - 2]) {
            /* Edge case: get it on the next pass */
            fseek(ff, -1, SEEK_CUR);
            continue;
         } else {
            newline_format = FF_MAC;
         }
      } else {
         newline_format = FF_UNIX;
      }
      break;
   }
   fclose(ff);
   return newline_format;
}

static int file_format(struct ast_channel *chan, const char *cmd, char *data, struct ast_str **buf, ssize_t len)
{
   enum file_format newline_format = file2format(data);
   ast_str_set(buf, len, "%c", newline_format == FF_UNIX ? 'u' : newline_format == FF_DOS ? 'd' : newline_format == FF_MAC ? 'm' : 'x');
   return 0;
}

static int file_read(struct ast_channel *chan, const char *cmd, char *data, struct ast_str **buf, ssize_t len)
{
   FILE *ff;
   int64_t offset = 0, length = LLONG_MAX;
   enum file_format format = FF_UNKNOWN;
   char fbuf[4096];
   int64_t flength, i; /* iterator needs to be signed, so it can go negative and terminate the loop */
   int64_t offset_offset = -1, length_offset = -1;
   char dos_state = 0;
   AST_DECLARE_APP_ARGS(args,
      AST_APP_ARG(filename);
      AST_APP_ARG(offset);
      AST_APP_ARG(length);
      AST_APP_ARG(options);
      AST_APP_ARG(fileformat);
   );

   AST_STANDARD_APP_ARGS(args, data);

   if (args.argc > 1) {
      sscanf(args.offset, "%" SCNd64, &offset);
   }
   if (args.argc > 2) {
      sscanf(args.length, "%" SCNd64, &length);
   }

   if (args.argc < 4 || !strchr(args.options, 'l')) {
      /* Character-based mode */
      off_t off_i;

      if (!(ff = fopen(args.filename, "r"))) {
         ast_log(LOG_WARNING, "Cannot open file '%s' for reading: %s\n", args.filename, strerror(errno));
         return 0;
      }

      if (fseeko(ff, 0, SEEK_END) < 0) {
         ast_log(LOG_ERROR, "Cannot seek to end of '%s': %s\n", args.filename, strerror(errno));
         fclose(ff);
         return -1;
      }
      flength = ftello(ff);

      if (offset < 0) {
         fseeko(ff, offset, SEEK_END);
         if ((offset = ftello(ff)) < 0) {
            ast_log(AST_LOG_ERROR, "Cannot determine offset position of '%s': %s\n", args.filename, strerror(errno));
            fclose(ff);
            return -1;
         }
      }
      if (length < 0) {
         fseeko(ff, length, SEEK_END);
         if ((length = ftello(ff)) - offset < 0) {
            /* Eliminates all results */
            fclose(ff);
            return -1;
         }
      } else if (length == LLONG_MAX) {
         fseeko(ff, 0, SEEK_END);
         length = ftello(ff);
      }

      ast_str_reset(*buf);

      fseeko(ff, offset, SEEK_SET);
      for (off_i = ftello(ff); off_i < flength && off_i < offset + length; off_i += sizeof(fbuf)) {
         /* Calculate if we need to retrieve just a portion of the file in memory */
         size_t toappend = sizeof(fbuf);

         if (fread(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf) && !feof(ff)) {
            ast_log(LOG_ERROR, "Short read?!!\n");
            break;
         }

         /* Don't go past the length requested */
         if (off_i + toappend > offset + length) {
            toappend = MIN(offset + length - off_i, flength - off_i);
         }

         ast_str_append_substr(buf, len, fbuf, toappend);
      }
      fclose(ff);
      return 0;
   }

   /* Line-based read */
   if (args.argc == 5) {
      if (tolower(args.fileformat[0]) == 'd') {
         format = FF_DOS;
      } else if (tolower(args.fileformat[0]) == 'm') {
         format = FF_MAC;
      } else if (tolower(args.fileformat[0]) == 'u') {
         format = FF_UNIX;
      }
   }

   if (format == FF_UNKNOWN) {
      if ((format = file2format(args.filename)) == FF_UNKNOWN) {
         ast_log(LOG_WARNING, "'%s' is not a line-based file\n", args.filename);
         return -1;
      }
   }

   if (offset < 0 && length <= offset) {
      /* Length eliminates all content */
      return -1;
   } else if (offset == 0) {
      offset_offset = 0;
   }

   if (!(ff = fopen(args.filename, "r"))) {
      ast_log(LOG_ERROR, "Cannot open '%s': %s\n", args.filename, strerror(errno));
      return -1;
   }

   if (fseek(ff, 0, SEEK_END)) {
      ast_log(LOG_ERROR, "Cannot seek to end of file '%s': %s\n", args.filename, strerror(errno));
      fclose(ff);
      return -1;
   }

   flength = ftello(ff);

   if (length == LLONG_MAX) {
      length_offset = flength;
   }

   /* For negative offset and/or negative length */
   if (offset < 0 || length < 0) {
      int64_t count = 0;
      /* Start with an even multiple of fbuf, so at the end of reading with a
       * 0 offset, we don't try to go past the beginning of the file. */
      for (i = (flength / sizeof(fbuf)) * sizeof(fbuf); i >= 0; i -= sizeof(fbuf)) {
         size_t end;
         char *pos;
         if (fseeko(ff, i, SEEK_SET)) {
            ast_log(LOG_ERROR, "Cannot seek to offset %" PRId64 ": %s\n", i, strerror(errno));
         }
         end = fread(fbuf, 1, sizeof(fbuf), ff);
         for (pos = (end < sizeof(fbuf) ? fbuf + end - 1 : fbuf + sizeof(fbuf) - 1); pos >= fbuf; pos--) {
            LINE_COUNTER(pos, format, count);

            if (length < 0 && count * -1 == length) {
               length_offset = i + (pos - fbuf);
            } else if (offset < 0 && count * -1 == (offset - 1)) {
               /* Found our initial offset.  We're done with reverse motion! */
               if (format == FF_DOS) {
                  offset_offset = i + (pos - fbuf) + 2;
               } else {
                  offset_offset = i + (pos - fbuf) + 1;
               }
               break;
            }
         }
         if ((offset < 0 && offset_offset >= 0) || (offset >= 0 && length_offset >= 0)) {
            break;
         }
      }
      /* We're at the beginning, and the negative offset indicates the exact number of lines in the file */
      if (offset < 0 && offset_offset < 0 && offset == count * -1) {
         offset_offset = 0;
      }
   }

   /* Positve line offset */
   if (offset > 0) {
      int64_t count = 0;
      fseek(ff, 0, SEEK_SET);
      for (i = 0; i < flength; i += sizeof(fbuf)) {
         char *pos;
         if (i + sizeof(fbuf) <= flength) {
            /* Don't let previous values influence current counts, due to short reads */
            memset(fbuf, 0, sizeof(fbuf));
         }
         if (fread(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf) && !feof(ff)) {
            ast_log(LOG_ERROR, "Short read?!!\n");
            fclose(ff);
            return -1;
         }
         for (pos = fbuf; pos < fbuf + sizeof(fbuf); pos++) {
            LINE_COUNTER(pos, format, count);

            if (count == offset) {
               offset_offset = i + (pos - fbuf) + 1;
               break;
            }
         }
         if (offset_offset >= 0) {
            break;
         }
      }
   }

   if (offset_offset < 0) {
      ast_log(LOG_ERROR, "Offset '%s' refers to before the beginning of the file!\n", args.offset);
      fclose(ff);
      return -1;
   }

   ast_str_reset(*buf);
   if (fseeko(ff, offset_offset, SEEK_SET)) {
      ast_log(LOG_ERROR, "fseeko failed: %s\n", strerror(errno));
   }

   /* If we have both offset_offset and length_offset, then grabbing the
    * buffer is simply a matter of just retrieving the file and adding it
    * to buf.  Otherwise, we need to run byte-by-byte forward until the
    * length is complete. */
   if (length_offset >= 0) {
      ast_debug(3, "offset=%" PRId64 ", length=%" PRId64 ", offset_offset=%" PRId64 ", length_offset=%" PRId64 "\n", offset, length, offset_offset, length_offset);
      for (i = offset_offset; i < length_offset; i += sizeof(fbuf)) {
         if (fread(fbuf, 1, i + sizeof(fbuf) > flength ? flength - i : sizeof(fbuf), ff) < (i + sizeof(fbuf) > flength ? flength - i : sizeof(fbuf))) {
            ast_log(LOG_ERROR, "Short read?!!\n");
         }
         ast_debug(3, "Appending first %" PRId64" bytes of fbuf=%s\n", (int64_t)(i + sizeof(fbuf) > length_offset ? length_offset - i : sizeof(fbuf)), fbuf);
         ast_str_append_substr(buf, len, fbuf, i + sizeof(fbuf) > length_offset ? length_offset - i : sizeof(fbuf));
      }
   } else if (length == 0) {
      /* Nothing to do */
   } else {
      /* Positive line offset */
      int64_t current_length = 0;
      char dos_state = 0;
      ast_debug(3, "offset=%" PRId64 ", length=%" PRId64 ", offset_offset=%" PRId64 ", length_offset=%" PRId64 "\n", offset, length, offset_offset, length_offset);
      for (i = offset_offset; i < flength; i += sizeof(fbuf)) {
         char *pos;
         size_t bytes_read;
         if ((bytes_read = fread(fbuf, 1, sizeof(fbuf), ff)) < sizeof(fbuf) && !feof(ff)) {
            ast_log(LOG_ERROR, "Short read?!!\n");
            fclose(ff);
            return -1;
         }
         for (pos = fbuf; pos < fbuf + bytes_read; pos++) {
            LINE_COUNTER(pos, format, current_length);

            if (current_length == length) {
               length_offset = i + (pos - fbuf) + 1;
               break;
            }
         }
         ast_debug(3, "length_offset=%" PRId64 ", length_offset - i=%" PRId64 "\n", length_offset, length_offset - i);
         ast_str_append_substr(buf, len, fbuf, (length_offset >= 0) ? length_offset - i : (flength > i + sizeof(fbuf)) ? sizeof(fbuf) : flength - i);

         if (length_offset >= 0) {
            break;
         }
      }
   }

   fclose(ff);
   return 0;
}

const char *format2term(enum file_format f) __attribute__((const));
const char *format2term(enum file_format f)
{
   const char *term[] = { "", "\n", "\r\n", "\r" };
   return term[f + 1];
}

static int file_write(struct ast_channel *chan, const char *cmd, char *data, const char *value)
{
   AST_DECLARE_APP_ARGS(args,
      AST_APP_ARG(filename);
      AST_APP_ARG(offset);
      AST_APP_ARG(length);
      AST_APP_ARG(options);
      AST_APP_ARG(format);
   );
   int64_t offset = 0, length = LLONG_MAX;
   off_t flength, vlength;
   size_t foplen = 0;
   FILE *ff;

   AST_STANDARD_APP_ARGS(args, data);

   if (args.argc > 1) {
      sscanf(args.offset, "%" SCNd64, &offset);
   }
   if (args.argc > 2) {
      sscanf(args.length, "%" SCNd64, &length);
   }

   vlength = strlen(value);

   if (args.argc < 4 || !strchr(args.options, 'l')) {
      /* Character-based mode */

      if (args.argc > 3 && strchr(args.options, 'a')) {
         /* Append mode */
         if (!(ff = fopen(args.filename, "a"))) {
            ast_log(LOG_WARNING, "Cannot open file '%s' for appending: %s\n", args.filename, strerror(errno));
            return 0;
         }
         if (fwrite(value, 1, vlength, ff) < vlength) {
            ast_log(LOG_ERROR, "Short write?!!\n");
         }
         fclose(ff);
         return 0;
      } else if (offset == 0 && length == LLONG_MAX) {
         if (!(ff = fopen(args.filename, "w"))) {
            ast_log(LOG_WARNING, "Cannot open file '%s' for writing: %s\n", args.filename, strerror(errno));
            return 0;
         }
         if (fwrite(value, 1, vlength, ff) < vlength) {
            ast_log(LOG_ERROR, "Short write?!!\n");
         }
         fclose(ff);
         return 0;
      }

      if (!(ff = fopen(args.filename, "r+"))) {
         ast_log(LOG_WARNING, "Cannot open file '%s' for modification: %s\n", args.filename, strerror(errno));
         return 0;
      }
      fseeko(ff, 0, SEEK_END);
      flength = ftello(ff);

      if (offset < 0) {
         if (fseeko(ff, offset, SEEK_END)) {
            ast_log(LOG_ERROR, "Cannot seek to offset of '%s': %s\n", args.filename, strerror(errno));
            fclose(ff);
            return -1;
         }
         if ((offset = ftello(ff)) < 0) {
            ast_log(AST_LOG_ERROR, "Cannot determine offset position of '%s': %s\n", args.filename, strerror(errno));
            fclose(ff);
            return -1;
         }
      }

      if (length < 0) {
         length = flength - offset + length;
         if (length < 0) {
            ast_log(LOG_ERROR, "Length '%s' exceeds the file length.  No data will be written.\n", args.length);
            fclose(ff);
            return -1;
         }
      }

      fseeko(ff, offset, SEEK_SET);

      ast_debug(3, "offset=%s/%" PRId64 ", length=%s/%" PRId64 ", vlength=%" PRId64 ", flength=%" PRId64 "\n",
         S_OR(args.offset, "(null)"), offset, S_OR(args.length, "(null)"), length, vlength, flength);

      if (length == vlength) {
         /* Simplest case, a straight replace */
         if (fwrite(value, 1, vlength, ff) < vlength) {
            ast_log(LOG_ERROR, "Short write?!!\n");
         }
         fclose(ff);
      } else if (length == LLONG_MAX) {
         /* Simple truncation */
         if (fwrite(value, 1, vlength, ff) < vlength) {
            ast_log(LOG_ERROR, "Short write?!!\n");
         }
         fclose(ff);
         if (truncate(args.filename, offset + vlength)) {
            ast_log(LOG_ERROR, "Unable to truncate the file: %s\n", strerror(errno));
         }
      } else if (length > vlength) {
         /* More complex -- need to close a gap */
         char fbuf[4096];
         off_t cur;
         if (fwrite(value, 1, vlength, ff) < vlength) {
            ast_log(LOG_ERROR, "Short write?!!\n");
         }
         fseeko(ff, length - vlength, SEEK_CUR);
         while ((cur = ftello(ff)) < flength) {
            if (fread(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf) && !feof(ff)) {
               ast_log(LOG_ERROR, "Short read?!!\n");
            }
            fseeko(ff, cur + vlength - length, SEEK_SET);
            if (fwrite(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf)) {
               ast_log(LOG_ERROR, "Short write?!!\n");
            }
            /* Seek to where we stopped reading */
            if (fseeko(ff, cur + sizeof(fbuf), SEEK_SET) < 0) {
               /* Only reason for seek to fail is EOF */
               break;
            }
         }
         fclose(ff);
         if (truncate(args.filename, flength - (length - vlength))) {
            ast_log(LOG_ERROR, "Unable to truncate the file: %s\n", strerror(errno));
         }
      } else {
         /* Most complex -- need to open a gap */
         char fbuf[4096];
         off_t lastwritten = flength + vlength - length;

         /* Start reading exactly the buffer size back from the end. */
         fseeko(ff, flength - sizeof(fbuf), SEEK_SET);
         while (offset < ftello(ff)) {
            if (fread(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf)) {
               ast_log(LOG_ERROR, "Short read?!!\n");
               fclose(ff);
               return -1;
            }
            /* Since the read moved our file ptr forward, we reverse, but
             * seek an offset equal to the amount we want to extend the
             * file by */
            fseeko(ff, vlength - length - sizeof(fbuf), SEEK_CUR);

            /* Note the location of this buffer -- we must not overwrite this position. */
            lastwritten = ftello(ff);

            if (fwrite(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf)) {
               ast_log(LOG_ERROR, "Short write?!!\n");
               fclose(ff);
               return -1;
            }

            if (lastwritten < offset + sizeof(fbuf)) {
               break;
            }
            /* Our file pointer is now either pointing to the end of the
             * file (new position) or a multiple of the fbuf size back from
             * that point.  Move back to where we want to start reading
             * again.  We never actually try to read beyond the end of the
             * file, so we don't have do deal with short reads, as we would
             * when we're shortening the file. */
            fseeko(ff, 2 * sizeof(fbuf) + vlength - length, SEEK_CUR);
         }

         /* Last part of the file that we need to preserve */
         if (fseeko(ff, offset + length, SEEK_SET)) {
            ast_log(LOG_WARNING, "Unable to seek to %" PRId64 " + %" PRId64 " != %" PRId64 "?)\n", offset, length, ftello(ff));
         }

         /* Doesn't matter how much we read -- just need to restrict the write */
         ast_debug(1, "Reading at %" PRId64 "\n", ftello(ff));
         if (fread(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf) && !feof(ff)) {
            ast_log(LOG_ERROR, "Short read?!!\n");
         }
         fseek(ff, offset, SEEK_SET);
         /* Write out the value, then write just up until where we last moved some data */
         if (fwrite(value, 1, vlength, ff) < vlength) {
            ast_log(LOG_ERROR, "Short write?!!\n");
         } else {
            off_t curpos = ftello(ff);
            foplen = lastwritten - curpos;
            if (fwrite(fbuf, 1, foplen, ff) < foplen) {
               ast_log(LOG_ERROR, "Short write?!!\n");
            }
         }
         fclose(ff);
      }
   } else {
      enum file_format newline_format = FF_UNKNOWN;

      /* Line mode */
      if (args.argc == 5) {
         if (tolower(args.format[0]) == 'u') {
            newline_format = FF_UNIX;
         } else if (tolower(args.format[0]) == 'm') {
            newline_format = FF_MAC;
         } else if (tolower(args.format[0]) == 'd') {
            newline_format = FF_DOS;
         }
      }
      if (newline_format == FF_UNKNOWN && (newline_format = file2format(args.filename)) == FF_UNKNOWN) {
         ast_log(LOG_ERROR, "File '%s' not in line format\n", args.filename);
         return -1;
      }

      if (strchr(args.options, 'a')) {
         /* Append to file */
         if (!(ff = fopen(args.filename, "a"))) {
            ast_log(LOG_ERROR, "Unable to open '%s' for appending: %s\n", args.filename, strerror(errno));
            return -1;
         }
         if (fwrite(value, 1, vlength, ff) < vlength) {
            ast_log(LOG_ERROR, "Short write?!!\n");
         } else if (!strchr(args.options, 'd') && fwrite(format2term(newline_format), 1, strlen(format2term(newline_format)), ff) < strlen(format2term(newline_format))) {
            ast_log(LOG_ERROR, "Short write?!!\n");
         }
         fclose(ff);
      } else if (offset == 0 && length == LLONG_MAX) {
         /* Overwrite file */
         off_t truncsize;
         if (!(ff = fopen(args.filename, "w"))) {
            ast_log(LOG_ERROR, "Unable to open '%s' for writing: %s\n", args.filename, strerror(errno));
            return -1;
         }
         if (fwrite(value, 1, vlength, ff) < vlength) {
            ast_log(LOG_ERROR, "Short write?!!\n");
         } else if (!strchr(args.options, 'd') && fwrite(format2term(newline_format), 1, strlen(format2term(newline_format)), ff) < strlen(format2term(newline_format))) {
            ast_log(LOG_ERROR, "Short write?!!\n");
         }
         if ((truncsize = ftello(ff)) < 0) {
            ast_log(AST_LOG_ERROR, "Unable to determine truncate position of '%s': %s\n", args.filename, strerror(errno));
         }
         fclose(ff);
         if (truncsize >= 0 && truncate(args.filename, truncsize)) {
            ast_log(LOG_ERROR, "Unable to truncate file '%s': %s\n", args.filename, strerror(errno));
            return -1;
         }
      } else {
         int64_t offset_offset = (offset == 0 ? 0 : -1), length_offset = -1, flength, i, current_length = 0;
         char dos_state = 0, fbuf[4096];

         if (offset < 0 && length < offset) {
            /* Nonsense! */
            ast_log(LOG_ERROR, "Length cannot specify a position prior to the offset\n");
            return -1;
         }

         if (!(ff = fopen(args.filename, "r+"))) {
            ast_log(LOG_ERROR, "Cannot open '%s' for modification: %s\n", args.filename, strerror(errno));
            return -1;
         }

         if (fseek(ff, 0, SEEK_END)) {
            ast_log(LOG_ERROR, "Cannot seek to end of file '%s': %s\n", args.filename, strerror(errno));
            fclose(ff);
            return -1;
         }
         if ((flength = ftello(ff)) < 0) {
            ast_log(AST_LOG_ERROR, "Cannot determine end position of file '%s': %s\n", args.filename, strerror(errno));
            fclose(ff);
            return -1;
         }

         /* For negative offset and/or negative length */
         if (offset < 0 || length < 0) {
            int64_t count = 0;
            for (i = (flength / sizeof(fbuf)) * sizeof(fbuf); i >= 0; i -= sizeof(fbuf)) {
               char *pos;
               if (fseeko(ff, i, SEEK_SET)) {
                  ast_log(LOG_ERROR, "Cannot seek to offset %" PRId64 ": %s\n", i, strerror(errno));
               }
               if (i + sizeof(fbuf) >= flength) {
                  memset(fbuf, 0, sizeof(fbuf));
               }
               if (fread(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf) && !feof(ff)) {
                  ast_log(LOG_ERROR, "Short read: %s\n", strerror(errno));
                  fclose(ff);
                  return -1;
               }
               for (pos = fbuf + sizeof(fbuf) - 1; pos >= fbuf; pos--) {
                  LINE_COUNTER(pos, newline_format, count);

                  if (length < 0 && count * -1 == length) {
                     length_offset = i + (pos - fbuf);
                  } else if (offset < 0 && count * -1 == (offset - 1)) {
                     /* Found our initial offset.  We're done with reverse motion! */
                     if (newline_format == FF_DOS) {
                        offset_offset = i + (pos - fbuf) + 2;
                     } else {
                        offset_offset = i + (pos - fbuf) + 1;
                     }
                     break;
                  }
               }
               if ((offset < 0 && offset_offset >= 0) || (offset >= 0 && length_offset >= 0)) {
                  break;
               }
            }
            /* We're at the beginning, and the negative offset indicates the exact number of lines in the file */
            if (offset < 0 && offset_offset < 0 && offset == count * -1) {
               offset_offset = 0;
            }
         }

         /* Positve line offset */
         if (offset > 0) {
            int64_t count = 0;
            fseek(ff, 0, SEEK_SET);
            for (i = 0; i < flength; i += sizeof(fbuf)) {
               char *pos;
               if (i + sizeof(fbuf) >= flength) {
                  memset(fbuf, 0, sizeof(fbuf));
               }
               if (fread(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf) && !feof(ff)) {
                  ast_log(LOG_ERROR, "Short read?!!\n");
                  fclose(ff);
                  return -1;
               }
               for (pos = fbuf; pos < fbuf + sizeof(fbuf); pos++) {
                  LINE_COUNTER(pos, newline_format, count);

                  if (count == offset) {
                     offset_offset = i + (pos - fbuf) + 1;
                     break;
                  }
               }
               if (offset_offset >= 0) {
                  break;
               }
            }
         }

         if (offset_offset < 0) {
            ast_log(LOG_ERROR, "Offset '%s' refers to before the beginning of the file!\n", args.offset);
            fclose(ff);
            return -1;
         }

         if (length == 0) {
            length_offset = offset_offset;
         } else if (length == LLONG_MAX) {
            length_offset = flength;
         }

         /* Positive line length */
         if (length_offset < 0) {
            fseeko(ff, offset_offset, SEEK_SET);
            for (i = offset_offset; i < flength; i += sizeof(fbuf)) {
               char *pos;
               if (i + sizeof(fbuf) >= flength) {
                  memset(fbuf, 0, sizeof(fbuf));
               }
               if (fread(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf) && !feof(ff)) {
                  ast_log(LOG_ERROR, "Short read?!!\n");
                  fclose(ff);
                  return -1;
               }
               for (pos = fbuf; pos < fbuf + sizeof(fbuf); pos++) {
                  LINE_COUNTER(pos, newline_format, current_length);

                  if (current_length == length) {
                     length_offset = i + (pos - fbuf) + 1;
                     break;
                  }
               }
               if (length_offset >= 0) {
                  break;
               }
            }
            if (length_offset < 0) {
               /* Exceeds length of file */
               ast_debug(3, "Exceeds length of file? length=%" PRId64 ", count=%" PRId64 ", flength=%" PRId64 "\n", length, current_length, flength);
               length_offset = flength;
            }
         }

         /* Have offset_offset and length_offset now */
         if (length_offset - offset_offset == vlength + (strchr(args.options, 'd') ? 0 : strlen(format2term(newline_format)))) {
            /* Simple case - replacement of text inline */
            fseeko(ff, offset_offset, SEEK_SET);
            if (fwrite(value, 1, vlength, ff) < vlength) {
               ast_log(LOG_ERROR, "Short write?!!\n");
            } else if (!strchr(args.options, 'd') && fwrite(format2term(newline_format), 1, strlen(format2term(newline_format)), ff) < strlen(format2term(newline_format))) {
               ast_log(LOG_ERROR, "Short write?!!\n");
            }
            fclose(ff);
         } else if (length_offset - offset_offset > vlength + (strchr(args.options, 'd') ? 0 : strlen(format2term(newline_format)))) {
            /* More complex case - need to shorten file */
            off_t cur;
            int64_t length_length = length_offset - offset_offset;
            size_t vlen = vlength + (strchr(args.options, 'd') ? 0 : strlen(format2term(newline_format)));

            ast_debug(3, "offset=%s/%" PRId64 ", length=%s/%" PRId64 " (%" PRId64 "), vlength=%" PRId64 ", flength=%" PRId64 "\n",
               args.offset, offset_offset, args.length, length_offset, length_length, vlength, flength);

            fseeko(ff, offset_offset, SEEK_SET);
            if (fwrite(value, 1, vlength, ff) < vlength) {
               ast_log(LOG_ERROR, "Short write?!!\n");
               fclose(ff);
               return -1;
            } else if (!strchr(args.options, 'd') && fwrite(format2term(newline_format), 1, vlen - vlength, ff) < vlen - vlength) {
               ast_log(LOG_ERROR, "Short write?!!\n");
               fclose(ff);
               return -1;
            }
            while ((cur = ftello(ff)) < flength) {
               if (cur < 0) {
                  ast_log(AST_LOG_ERROR, "Unable to determine last write position for '%s': %s\n", args.filename, strerror(errno));
                  fclose(ff);
                  return -1;
               }
               fseeko(ff, length_length - vlen, SEEK_CUR);
               if (fread(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf) && !feof(ff)) {
                  ast_log(LOG_ERROR, "Short read?!!\n");
                  fclose(ff);
                  return -1;
               }
               /* Seek to where we last stopped writing */
               fseeko(ff, cur, SEEK_SET);
               if (fwrite(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf)) {
                  ast_log(LOG_ERROR, "Short write?!!\n");
                  fclose(ff);
                  return -1;
               }
            }
            fclose(ff);
            if (truncate(args.filename, flength - (length_length - vlen))) {
               ast_log(LOG_ERROR, "Truncation of file failed: %s\n", strerror(errno));
            }
         } else {
            /* Most complex case - need to lengthen file */
            size_t vlen = vlength + (strchr(args.options, 'd') ? 0 : strlen(format2term(newline_format)));
            int64_t origlen = length_offset - offset_offset;
            off_t lastwritten = flength + vlen - origlen;

            ast_debug(3, "offset=%s/%" PRId64 ", length=%s/%" PRId64 ", vlength=%" PRId64 ", flength=%" PRId64 "\n",
               args.offset, offset_offset, args.length, length_offset, vlength, flength);

            fseeko(ff, flength - sizeof(fbuf), SEEK_SET);
            while (offset_offset + sizeof(fbuf) < ftello(ff)) {
               if (fread(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf)) {
                  ast_log(LOG_ERROR, "Short read?!!\n");
                  fclose(ff);
                  return -1;
               }
               fseeko(ff, sizeof(fbuf) - vlen - origlen, SEEK_CUR);
               if (fwrite(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf)) {
                  ast_log(LOG_ERROR, "Short write?!!\n");
                  fclose(ff);
                  return -1;
               }
               if ((lastwritten = ftello(ff) - sizeof(fbuf)) < offset_offset + sizeof(fbuf)) {
                  break;
               }
               fseeko(ff, 2 * sizeof(fbuf) + vlen - origlen, SEEK_CUR);
            }
            fseek(ff, length_offset, SEEK_SET);
            if (fread(fbuf, 1, sizeof(fbuf), ff) < sizeof(fbuf) && !feof(ff)) {
               ast_log(LOG_ERROR, "Short read?!!\n");
               fclose(ff);
               return -1;
            }
            fseek(ff, offset_offset, SEEK_SET);
            if (fwrite(value, 1, vlength, ff) < vlength) {
               ast_log(LOG_ERROR, "Short write?!!\n");
               fclose(ff);
               return -1;
            } else if (!strchr(args.options, 'd') && fwrite(format2term(newline_format), 1, strlen(format2term(newline_format)), ff) < strlen(format2term(newline_format))) {
               ast_log(LOG_ERROR, "Short write?!!\n");
               fclose(ff);
               return -1;
            } else {
               off_t curpos = ftello(ff);
               foplen = lastwritten - curpos;
               if (fwrite(fbuf, 1, foplen, ff) < foplen) {
                  ast_log(LOG_ERROR, "Short write?!!\n");
               }
            }
            fclose(ff);
         }
      }
   }

   return 0;
}

static struct ast_custom_function env_function = {
   .name = "ENV",
   .read = env_read,
   .write = env_write
};

static struct ast_custom_function stat_function = {
   .name = "STAT",
   .read = stat_read,
   .read_max = 12,
};

static struct ast_custom_function file_function = {
   .name = "FILE",
   .read2 = file_read,
   .write = file_write,
};

static struct ast_custom_function file_count_line_function = {
   .name = "FILE_COUNT_LINE",
   .read2 = file_count_line,
   .read_max = 12,
};

static struct ast_custom_function file_format_function = {
   .name = "FILE_FORMAT",
   .read2 = file_format,
   .read_max = 2,
};

static int unload_module(void)
{
   int res = 0;

   res |= ast_custom_function_unregister(&env_function);
   res |= ast_custom_function_unregister(&stat_function);
   res |= ast_custom_function_unregister(&file_function);
   res |= ast_custom_function_unregister(&file_count_line_function);
   res |= ast_custom_function_unregister(&file_format_function);

   return res;
}

static int load_module(void)
{
   int res = 0;

   res |= ast_custom_function_register(&env_function);
   res |= ast_custom_function_register_escalating(&stat_function, AST_CFE_READ);
   res |= ast_custom_function_register_escalating(&file_function, AST_CFE_BOTH);
   res |= ast_custom_function_register_escalating(&file_count_line_function, AST_CFE_READ);
   res |= ast_custom_function_register_escalating(&file_format_function, AST_CFE_READ);

   return res;
}

AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Environment/filesystem dialplan functions");