diplodocus.org Git - nmh/blob - sbr/mime_type.c

   1 /* mime_type.c -- routine to determine the MIME Content-Type of a file
   2  *
   3  * This code is Copyright (c) 2014, by the authors of nmh.  See the
   4  * COPYRIGHT file in the root directory of the nmh distribution for
   5  * complete copyright information.
   6  */
   7
   8 #include <h/mh.h>
   9 #include <h/utils.h>
  10 #include <h/tws.h>
  11 #include "mime_type.h"
  12
  13 #ifdef MIMETYPEPROC
  14 static char *get_file_info(const char *, const char *);
  15 #endif /* MIMETYPEPROC */
  16
  17 /*
  18  * Try to use external command to determine mime type, and possibly
  19  * encoding.  If that fails try using the filename extension.  Caller
  20  * is responsible for free'ing returned memory.
  21  */
  22 char *
  23 mime_type(const char *file_name) {
  24     char *content_type = NULL;  /* mime content type */
  25     char *p;
  26     static int loaded_defaults = 0;
  27
  28 #ifdef MIMETYPEPROC
  29     char *mimetype;
  30
  31     if ((mimetype = get_file_info(MIMETYPEPROC, file_name))) {
  32 #ifdef MIMEENCODINGPROC
  33         /* Try to append charset for text content. */
  34         char *mimeencoding;
  35
  36         if (!strncasecmp(mimetype, "text", 4) &&
  37             (mimeencoding = get_file_info(MIMEENCODINGPROC, file_name))) {
  38             content_type = concat(mimetype, "; charset=", mimeencoding, NULL);
  39             free(mimeencoding);
  40             free(mimetype);
  41         } else
  42             content_type = mimetype;
  43 #else  /* MIMEENCODINGPROC */
  44         content_type = mimetype;
  45 #endif /* MIMEENCODINGPROC */
  46     }
  47 #endif /* MIMETYPEPROC */
  48
  49     /*
  50      * If we didn't get the MIME type from the contents (or we don't support
  51      * the necessary command) then use the mhshow suffix.
  52      */
  53
  54     if (content_type == NULL) {
  55         struct node *np;                /* Content scan node pointer */
  56         FILE *fp;                       /* File pointer for mhn.defaults */
  57
  58         if (! loaded_defaults &&
  59                         (fp = fopen(p = etcpath("mhn.defaults"), "r"))) {
  60             loaded_defaults = 1;
  61             readconfig(NULL, fp, p, 0);
  62             fclose(fp);
  63         }
  64
  65         if ((p = strrchr(file_name, '.')) != NULL) {
  66             for (np = m_defs; np; np = np->n_next) {
  67                 if (strncasecmp(np->n_name, "mhshow-suffix-", 14) == 0 &&
  68                     strcasecmp(p, FENDNULL(np->n_field)) == 0) {
  69                     content_type = strdup(np->n_name + 14);
  70                     break;
  71                 }
  72             }
  73         }
  74
  75         /*
  76          * If we didn't match any filename extension, try to infer the
  77          * content type. If we have binary, assume application/octet-stream;
  78          * otherwise, assume text/plain.
  79          */
  80
  81         if (content_type == NULL) {
  82             FILE *fp;
  83             int binary = 0, c;
  84
  85             if (!(fp = fopen(file_name, "r"))) {
  86                 inform("unable to access file \"%s\"", file_name);
  87                 return NULL;
  88             }
  89
  90             while ((c = getc(fp)) != EOF) {
  91                 if (! isascii(c)  ||  c == 0) {
  92                     binary = 1;
  93                     break;
  94                 }
  95             }
  96
  97             fclose(fp);
  98
  99             content_type =
 100                 strdup(binary ? "application/octet-stream" : "text/plain");
 101         }
 102     }
 103
 104     return content_type;
 105 }
 106
 107
 108 #ifdef MIMETYPEPROC
 109 /*
 110  * Get information using proc about a file.
 111  * Non-null return value must be free(3)'d. */
 112 static char *
 113 get_file_info(const char *proc, const char *file_name)
 114 {
 115     char *quotec;
 116     char *cmd;
 117     FILE *fp;
 118     bool ok;
 119     char buf[max(BUFSIZ, 2048)];
 120     char *info;
 121     char *needle;
 122
 123     if (strchr(file_name, '\'')) {
 124         if (strchr(file_name, '"')) {
 125             inform("filenames containing both single and double quotes "
 126                 "are unsupported for attachment");
 127             return NULL;
 128         }
 129         quotec = "\"";
 130     } else
 131         quotec = "'";
 132
 133     cmd = concat(proc, " ", quotec, file_name, quotec, NULL);
 134     if (!cmd) {
 135         inform("concat with \"%s\" failed, out of memory?", proc);
 136         return NULL;
 137     }
 138
 139     if ((fp = popen(cmd, "r")) == NULL) {
 140         inform("no output from %s", cmd);
 141         free(cmd);
 142         return NULL;
 143     }
 144
 145     ok = fgets(buf, sizeof buf, fp);
 146     free(cmd);
 147     (void)pclose(fp);
 148     if (!ok)
 149         return NULL;
 150
 151     /* s#^.*:[ \t]*##. */
 152     info = buf;
 153     if ((needle = strchr(info, ':'))) {
 154         info = needle + 1;
 155         while (isblank((unsigned char)*info))
 156             info++;
 157     }
 158
 159     /* s#[\n\r].*##. */
 160     if ((needle = strpbrk(info, "\n\r")))
 161         *needle = '\0';
 162
 163     return strdup(info);
 164 }
 165 #endif /* MIMETYPEPROC */