Add RFC-2047 encoder for internationalized mail warnings.

[~andy/fetchmail] / rfc2047e.c

diff --git a/rfc2047e.c b/rfc2047e.c
new file mode 100644 (file)
index 0000000..d42e304
--- /dev/null
+++ b/rfc2047e.c
@@ -0,0 +1,195 @@
+/*
+    rfc2047e.c - encode a string as per RFC-2047
+    Copyright (C) 2004  Matthias Andree
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+*/
+
+#define _GNU_SOURCE
+#include "fetchmail.h"
+
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+
+static const char noenc[] = "!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~";
+static const char encchars[] = "!\"#$%&'*+,-./0123456789:;<>@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^`abcdefghijklmnopqrstuvwxyz{|}~";
+static const char ws[] = " \t\r\n";
+
+#ifdef TEST
+void report (FILE *fp, const char *format, ...) { (void)fp; (void)format;}
+#endif
+
+static int needs_enc(const char *string) {
+    if (strspn(string, noenc) < strlen(string))
+       return 1;
+    if (strncmp(string, "=?", 2) == 0
+           && strcmp(string + strlen(string) - 2, "?=") == 0)
+       return 1;
+    return 0;
+}
+
+static char *encode_words(char *const *words, int nwords, const char *charset)
+{
+    char *out, *t, *v;
+    size_t l = 0;
+    int i;
+
+    for (i = 0; i < nwords; i++)
+       l += strlen(words[i]) * 3; /* worst case, encode everything */
+    l += (strlen(charset) + 8) * (l/60 + 1);
+
+    out = v = xmalloc(l);
+    t = stpcpy(out, "=?");
+    t = stpcpy(t, charset);
+    t = stpcpy(t, "?Q?");
+    for (i = 0; i < nwords; i++) {
+       const char *u;
+       for (u = words[i]; *u; u++) {
+           if (t - v >= 69) {
+               t = stpcpy(t, "?=\r\n=?");
+               v = t - 2;
+               t = stpcpy(t, charset);
+               t = stpcpy(t, "?Q?");
+           }
+           if (*u == ' ') { *t++ = '_'; continue; }
+           if (strchr(encchars, *u)) { *t++ = *u; continue; }
+           sprintf(t, "=%02X", (unsigned char)*u);
+           t += 3;
+       }
+    }
+    strcpy(t, "?=");
+    return out;
+}
+
+char *rfc2047e(const char *string, const char *charset) {
+    char *t, *out;
+    const char *r;
+    int count, minlen, idx, i;
+    char **words = NULL;
+    size_t l;
+
+    assert(strlen(charset) < 40);
+
+    /* phase 1: split original into words */
+    /* 1a: count, 1b: copy */
+    count = 0;
+    r = string;
+    while (*r) {
+       count++;
+       r += strcspn(r, ws);
+       if (!*r) break;
+       count++;
+       r += strspn(r, ws);
+    }
+    words = xmalloc(sizeof(char *) * (count + 1));
+
+    idx = 0;
+    r = string;
+    while (*r) {
+       l = strcspn(r, ws);
+       words[idx] = xmalloc(l+1);
+       memcpy(words[idx], r, l);
+       words[idx][l] = 0;
+       idx++;
+       r += l;
+       if (!*r) break;
+       l = strspn(r, ws);
+       words[idx] = xmalloc(l+1);
+       memcpy(words[idx], r, l);
+       words[idx][l] = 0;
+       idx++;
+       r += l;
+    }
+
+    /* phase 2: encode words */
+    /* a: find ranges of adjacent words to need encoding */
+    /* b: encode ranges */
+
+    idx = 0;
+    while (idx < count) {
+       int end; char *tmp;
+
+       if (!needs_enc(words[idx])) {
+           idx += 2;
+           continue;
+       }
+       for (end = idx + 2; end < count; end += 2) {
+           if (!needs_enc(words[end]))
+               break;
+       }
+       end -= 2;
+       tmp = encode_words(&words[idx], end - idx + 1, charset);
+       free(words[idx]);
+       words[idx] = tmp;
+       for (i = idx + 1; i <= end; i++)
+           words[i][0] = 0;
+       idx = end + 2;
+    }
+
+    for (idx = l = 0; idx < count; idx++) {
+       l += strlen(words[idx]);
+    }
+
+    /* phase 3: limit lengths */
+    minlen = strlen(charset) + 7;
+    /* allocate ample memory */
+    out = xmalloc(l + (l / (72 - minlen) + 1) * (minlen + 2) + 1);
+
+    if (count)
+       t = stpcpy(out, words[0]);
+    else
+       t = out, *out = 0;
+
+    l = strlen(out);
+
+    for (i = 1; i < count; i+=2) {
+       size_t m;
+       char *tmp;
+
+       m = strlen(words[i]);
+       if (i + 1 < count)
+           m += strcspn(words[i+1], "\r\n");
+       if (l + m > 74)
+           l = 0, t = stpcpy(t, "\r\n");
+       t = stpcpy(t, words[i]);
+       if (i + 1 < count) {
+           t = stpcpy(t, words[i+1]);
+       }
+       tmp = strrchr(out, '\n');
+       if (!tmp) tmp = out; else tmp++;
+       l = strlen(tmp);
+    }
+
+    /* free memory */
+    for (i = 0; i < count; i++) free(words[i]);
+    free(words);
+    return out;
+}
+
+#ifdef TEST
+int main(int argc, char **argv) {
+    char *t;
+
+    if (argc > 1) {
+       t = rfc2047e(argv[1], argc > 2 ? argv[2] : "utf-8");
+       printf( " input: \"%s\"\n"
+               "output: \"%s\"\n", argv[1], t);
+       free(t);
+    }
+    return EXIT_SUCCESS;
+}
+#endif