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/* Copyright (c) 2009 Dovecot authors, see the included COPYING file */
#include "lib.h"
#include "str.h"
#include "base64.h"
#include "message-header-encode.h"
#define MIME_WRAPPER_LEN (strlen("=?utf-8?q?""?="))
#define MIME_MAX_LINE_LEN 76
#define IS_LWSP(c) \
((c) == ' ' || (c) == '\t' || (c) == '\n')
static bool input_idx_need_encoding(const unsigned char *input, unsigned int i)
{
if ((input[i] & 0x80) != 0)
return TRUE;
if (input[i] == '=' && input[i+1] == '?' &&
(i == 0 || IS_LWSP(input[i-1])))
return TRUE;
return FALSE;
}
static unsigned int str_last_line_len(string_t *str)
{
const unsigned char *data = str_data(str);
unsigned int i = str_len(str);
while (i > 0 && data[i-1] != '\n')
i--;
return str_len(str) - i;
}
void message_header_encode_q(const unsigned char *input, unsigned int len,
string_t *output)
{
unsigned int i, line_len, line_len_left;
line_len = str_last_line_len(output);
if (line_len >= MIME_MAX_LINE_LEN - MIME_WRAPPER_LEN - 3) {
str_append(output, "\n\t");
line_len = 1;
}
str_append(output, "=?utf-8?q?");
line_len_left = MIME_MAX_LINE_LEN - MIME_WRAPPER_LEN - line_len;
for (i = 0; i < len; i++) {
if (line_len_left < 3) {
/* if we're not at the beginning of a character,
go backwards until we are */
while ((input[i] & 0xc0) == 0x80) {
str_truncate(output, str_len(output)-3);
i--;
}
str_append(output, "?=\n\t=?utf-8?q?");
line_len_left = MIME_MAX_LINE_LEN -
MIME_WRAPPER_LEN - 1;
}
switch (input[i]) {
case ' ':
str_append_c(output, '_');
break;
case '=':
case '?':
case '_':
line_len_left -= 2;
str_printfa(output, "=%2X", input[i]);
break;
default:
if (input[i] < 32 || (input[i] & 0x80) != 0) {
line_len_left -= 2;
str_printfa(output, "=%2X", input[i]);
} else {
str_append_c(output, input[i]);
}
break;
}
line_len_left--;
}
str_append(output, "?=");
}
void message_header_encode_b(const unsigned char *input, unsigned int len,
string_t *output)
{
unsigned int line_len, line_len_left, max;
line_len = str_last_line_len(output);
if (line_len >= MIME_MAX_LINE_LEN - MIME_WRAPPER_LEN) {
str_append(output, "\n\t");
line_len = 1;
}
for (;;) {
line_len_left = MIME_MAX_LINE_LEN - MIME_WRAPPER_LEN - line_len;
max = MAX_BASE64_DECODED_SIZE(line_len_left);
do {
max--;
if (max > len)
max = len;
else {
/* all of it doesn't fit. find a character where we
can split it from. */
while (max > 0 && (input[max] & 0xc0) == 0x80)
max--;
}
} while (MAX_BASE64_ENCODED_SIZE(max) > line_len_left &&
max > 0);
if (max > 0) {
str_append(output, "=?utf-8?b?");
base64_encode(input, max, output);
str_append(output, "?=");
}
input += max;
len -= max;
if (len == 0)
break;
str_append(output, "\n\t");
line_len = 1;
}
}
void message_header_encode(const char *_input, string_t *output)
{
const unsigned char *input = (const unsigned char *)_input;
unsigned int i, first_idx, last_idx;
unsigned int enc_chars, enc_len, base64_len, q_len;
bool use_q;
/* find the first word that needs encoding */
for (i = 0; input[i] != '\0'; i++) {
if (input_idx_need_encoding(input, i))
break;
}
if (input[i] == '\0') {
/* no encoding necessary */
str_append(output, _input);
return;
}
first_idx = i;
while (first_idx > 0 && !IS_LWSP(input[first_idx-1]))
first_idx--;
/* find the last word that needs encoding */
last_idx = ++i; enc_chars = 1;
for (; input[i] != '\0'; i++) {
if (input_idx_need_encoding(input, i)) {
last_idx = i + 1;
enc_chars++;
}
}
while (input[last_idx] != '\0' && !IS_LWSP(input[last_idx]))
last_idx++;
/* figure out if we should use Q or B encoding. Prefer Q if it's not
too much larger. */
enc_len = last_idx - first_idx;
base64_len = MAX_BASE64_ENCODED_SIZE(enc_len);
q_len = enc_len + enc_chars*3;
use_q = q_len*2/3 <= base64_len;
/* and do it */
str_append_n(output, input, first_idx);
if (use_q)
message_header_encode_q(input + first_idx, enc_len, output);
else
message_header_encode_b(input + first_idx, enc_len, output);
str_append(output, _input + last_idx);
}
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