me.c

   1 /* encode a mime message */
   2 #include <stdio.h>
   3 #include <string.h>
   4 #include <ctype.h>
   5
   6 #define LNSZ            1024
   7
   8 static char out[LNSZ * 2];      /* collected characters */
   9 static int out_n;               /* number of characters in out */
  10 static int out_mime;            /* set if inside a mime encoded word */
  11 static int out_mbuf;            /* buffered characters */
  12 static int out_mlen;            /* number of buffered characters */
  13 static int out_mhdr;            /* header type; 's' for subject 'a' for address */
  14
  15 static char *b64_chr =
  16         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  17
  18 /* encode 3 bytes in base64 */
  19 static void b64_word(char *s, unsigned num)
  20 {
  21         s[3] = b64_chr[num & 0x3f];
  22         num >>= 6;
  23         s[2] = b64_chr[num & 0x3f];
  24         num >>= 6;
  25         s[1] = b64_chr[num & 0x3f];
  26         num >>= 6;
  27         s[0] = b64_chr[num & 0x3f];
  28 }
  29
  30 static void q_beg(void)
  31 {
  32         out[out_n++] = '=';
  33         out[out_n++] = '?';
  34         out[out_n++] = 'U';
  35         out[out_n++] = 'T';
  36         out[out_n++] = 'F';
  37         out[out_n++] = '-';
  38         out[out_n++] = '8';
  39         out[out_n++] = '?';
  40         out[out_n++] = 'B';
  41         out[out_n++] = '?';
  42         out_mime = 1;
  43 }
  44
  45 static void q_put(int c)
  46 {
  47         out_mlen++;
  48         out_mbuf = (out_mbuf << 8) | c;
  49         if (out_mlen == 3) {
  50                 b64_word(out + out_n, out_mbuf);
  51                 out_n += 4;
  52                 out_mlen = 0;
  53                 out_mbuf = 0;
  54         }
  55 }
  56
  57 static void q_end(void)
  58 {
  59         int i;
  60         for (i = 0; out_mlen; i++)
  61                 q_put(0);
  62         while (--i >= 0)
  63                 out[out_n - i - 1] = '=';
  64         out_mime = 0;
  65         out[out_n++] = '?';
  66         out[out_n++] = '=';
  67 }
  68
  69 static void out_flush(void)
  70 {
  71         if (out_mime)
  72                 q_end();
  73         out[out_n] = '\0';
  74         fputs(out, stdout);
  75         out_n = 0;
  76 }
  77
  78 static void out_chr(int c)
  79 {
  80         if (out_mime) {
  81                 if (c == '\r' || c == '\n') {
  82                         q_end();
  83                 } else if (out_mhdr == 'a' && c != ' ' && ~c & 0x80) {
  84                         q_end();
  85                 } else if (out_n > 65 && (c & 0xc0) != 0x80) {
  86                         q_end();
  87                         out_flush();
  88                         out[out_n++] = '\n';
  89                         out[out_n++] = ' ';
  90                         q_beg();
  91                 }
  92         }
  93         if (c == '\n' || out_n > 75) {
  94                 out[out_n++] = c;
  95                 out_flush();
  96         } else {
  97                 if (out_mhdr && (c & 0x80) && !out_mime)
  98                         q_beg();
  99                 if (out_mime)
 100                         q_put(c);
 101                 else
 102                         out[out_n++] = c;
 103         }
 104 }
 105
 106 static int startswith(char *r, char *s)
 107 {
 108         while (*s)
 109                 if (tolower((unsigned char) *s++) != tolower((unsigned char) *r++))
 110                         return 0;
 111         return 1;
 112 }
 113
 114 int me(char *argv[])
 115 {
 116         char ln[LNSZ];
 117         while (fgets(ln, sizeof(ln), stdin)) {
 118                 char *s = ln;
 119                 if (ln[0] != ' ' && ln[0] != '\t')
 120                         out_mhdr = 0;
 121                 if (startswith(ln, "from:") || startswith(ln, "to:") ||
 122                                 startswith(ln, "cc:") || startswith(ln, "bcc:"))
 123                         out_mhdr = 'a';
 124                 if (startswith(ln, "subject:"))
 125                         out_mhdr = 's';
 126                 while (*s)
 127                         out_chr((unsigned char) *s++);
 128                 if (ln[0] == '\n' || ln[0] == '\r')
 129                         break;
 130         }
 131         while (fgets(ln, sizeof(ln), stdin))
 132                 fputs(ln, stdout);
 133         return 0;
 134 }