libs/rfc822/encodeautodetect.c

   1 /*
   2 ** Copyright 2003-2011 Double Precision, Inc.  See COPYING for
   3 ** distribution information.
   4 */
   5
   6 /*
   7 */
   8 #include        "encode.h"
   9 #include        <string.h>
  10 #include        <stdlib.h>
  11 #include        "../unicode/unicode.h"
  12
  13 static const char *libmail_encode_autodetect(int use7bit,
  14                                              int (*func)(void *), void *arg,
  15                                              int *binaryflag)
  16 {
  17         int     l=0;
  18         int     longline=0;
  19         int c;
  20
  21         size_t charcnt=0;
  22         size_t bit8cnt=0;
  23
  24         if (binaryflag)
  25                 *binaryflag=0;
  26
  27         while ((c = (*func)(arg)) != EOF)
  28         {
  29                 unsigned char ch= (unsigned char)c;
  30
  31                 ++charcnt;
  32
  33                 ++l;
  34                 if (ch < 0x20 || ch >= 0x80)
  35                 {
  36                         if (ch != '\t' && ch != '\r' && ch != '\n')
  37                         {
  38                                 ++bit8cnt;
  39                                 l += 2;
  40                         }
  41                 }
  42
  43                 if (ch == 0)
  44                 {
  45                         if (binaryflag)
  46                                 *binaryflag=1;
  47
  48                         return "base64";
  49                 }
  50
  51                 if (ch == '\n') l=0;
  52                 else if (l > 990)
  53                 {
  54                         longline=1;
  55                 }
  56
  57         }
  58
  59         if (use7bit || longline)
  60         {
  61                 if (bit8cnt > charcnt / 10)
  62                         return "base64";
  63
  64                 return "quoted-printable";
  65         }
  66
  67         return bit8cnt ? "8bit":"7bit";
  68 }
  69
  70 struct file_info {
  71         FILE *fp;
  72         off_t pos;
  73         off_t end;
  74 };
  75
  76 static int read_file(void *arg)
  77 {
  78 int c;
  79 struct file_info *fi = (struct file_info *)arg;
  80         if (fi->end >= 0 && fi->pos > fi->end)
  81                 return EOF;
  82         c = getc(fi->fp);
  83         fi->pos++;
  84         return c;
  85 }
  86
  87 static int read_string(void * arg)
  88 {
  89 int c;
  90 unsigned char **strp = (unsigned char **)arg;
  91         if (**strp == 0)
  92                 return EOF;
  93         c = (int)**strp;
  94         (*strp)++;
  95         return c;
  96 }
  97
  98 const char *libmail_encode_autodetect_fp(FILE *fp, int use7bit,
  99                                          int *binaryflag)
 100 {
 101         return libmail_encode_autodetect_fpoff(fp, use7bit, 0, -1,
 102                                                binaryflag);
 103 }
 104
 105 const char *libmail_encode_autodetect_fpoff(FILE *fp, int use7bit,
 106                                             off_t start_pos, off_t end_pos,
 107                                             int *binaryflag)
 108 {
 109 struct file_info fi;
 110 off_t orig_pos = ftell(fp);
 111 off_t pos = orig_pos;
 112 const char *rc;
 113
 114         if (start_pos >= 0)
 115         {
 116                 if (fseek(fp, start_pos, SEEK_SET) == (off_t)-1)
 117                         return NULL;
 118                 else
 119                         pos = start_pos;
 120         }
 121
 122         fi.fp = fp;
 123         fi.pos = pos;
 124         fi.end = end_pos;
 125
 126         rc = libmail_encode_autodetect(use7bit, &read_file, &fi,
 127                                        binaryflag);
 128
 129         if (fseek(fp, orig_pos, SEEK_SET) == (off_t)-1)
 130                 return NULL;
 131         return rc;
 132 }
 133
 134 const char *libmail_encode_autodetect_buf(const char *str, int use7bit)
 135 {
 136         return libmail_encode_autodetect(use7bit, &read_string, &str,
 137                                          NULL);
 138 }