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/* GNU Mailutils -- a suite of utilities for electronic mail
Copyright (C) 2024-2025 Free Software Foundation, Inc.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.
This library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with GNU Mailutils. If not, see <http://www.gnu.org/licenses/>. */
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <mailutils/errno.h>
#include <mailutils/filter.h>
#include <mailutils/stream.h>
enum
{
S_INIT, /* Initial state */
S_BOL, /* Beginning of line */
S_ESC, /* Collecting > escapes */
S_FROM, /* Collecting "From " characters */
};
struct transcoder
{
int state; /* Transcoder state */
int count; /* Number of consecutive '>' seen. */
int len; /* Number of "From" characters collected */
};
static char from_line[] = "From ";
/* Move min(isize,osize) bytes from iptr to optr, removing initial '>'
from each sequence '>+From ' at the beginning of line */
static enum mu_filter_result
_fromrd_decoder (void *xd,
enum mu_filter_command cmd,
struct mu_filter_io *iobuf)
{
const unsigned char *iptr;
size_t isize;
char *optr;
size_t osize;
struct transcoder *xcode = xd;
size_t i, j, k;
size_t len, reqlen;
switch (cmd)
{
case mu_filter_init:
xcode->state = S_BOL;
xcode->count = 0;
xcode->len = 0;
return mu_filter_ok;
case mu_filter_done:
return mu_filter_ok;
default:
break;
}
iptr = (const unsigned char *) iobuf->input;
isize = iobuf->isize;
optr = iobuf->output;
osize = iobuf->osize;
for (i = j = 0; i < isize && j < osize; i++)
{
unsigned char c = *iptr++;
switch (xcode->state)
{
case S_INIT:
optr[j++] = c;
if (c == '\n')
xcode->state = S_BOL;
break;
case S_BOL:
if (c == '>')
{
xcode->state = S_ESC;
xcode->count = 1;
}
else
{
optr[j++] = c;
if (c != '\n')
xcode->state = S_INIT;
}
break;
case S_ESC:
if (c == '>')
{
xcode->count++;
}
else if (c == from_line[0])
{
xcode->state = S_FROM;
xcode->len = 1;
}
else
{
xcode->state = S_INIT;
goto emit;
}
break;
case S_FROM:
if (from_line[xcode->len] == 0)
{
xcode->count--;
}
else if (c == from_line[xcode->len])
{
xcode->len++;
continue;
}
else
{
//RESTORE
}
emit:
reqlen = xcode->len + xcode->count;
len = osize - j;
if (len < reqlen)
{
iobuf->osize += reqlen;
return mu_filter_moreoutput;
}
for (k = 0; k < xcode->count; k++, j++)
optr[j] = '>';
memcpy (optr + j, from_line, xcode->len);
j += xcode->len;
xcode->state = S_INIT;
xcode->count = xcode->len = 0;
i--;
iptr--;
}
}
iobuf->isize = i;
iobuf->osize = j;
return mu_filter_ok;
}
static enum mu_filter_result
_fromrd_encoder (void *xd,
enum mu_filter_command cmd,
struct mu_filter_io *iobuf)
{
const unsigned char *iptr;
size_t isize;
char *optr;
size_t osize;
struct transcoder *xcode = xd;
size_t i, j, k;
size_t len, reqlen;
switch (cmd)
{
case mu_filter_init:
xcode->state = S_BOL;
xcode->count = 0;
xcode->len = 0;
return mu_filter_ok;
case mu_filter_done:
return mu_filter_ok;
default:
break;
}
iptr = (const unsigned char *) iobuf->input;
isize = iobuf->isize;
optr = iobuf->output;
osize = iobuf->osize;
for (i = j = 0; i < isize && j < osize; i++)
{
unsigned char c = *iptr++;
switch (xcode->state)
{
case S_INIT:
optr[j++] = c;
if (c == '\n')
xcode->state = S_BOL;
break;
case S_BOL:
if (c == '>')
{
xcode->state = S_ESC;
xcode->count = 1;
}
else if (c == from_line[0])
{
xcode->state = S_FROM;
xcode->count = 0;
xcode->len = 1;
}
else
{
optr[j++] = c;
if (c != '\n')
xcode->state = S_INIT;
}
break;
case S_ESC:
if (c == '>')
{
xcode->count++;
}
else if (c == from_line[0])
{
xcode->state = S_FROM;
xcode->len = 1;
}
else
{
xcode->state = S_INIT;
goto emit;
}
break;
case S_FROM:
if (from_line[xcode->len] == 0)
{
xcode->count++;
}
else if (c == from_line[xcode->len])
{
xcode->len++;
continue;
}
else
{
//RESTORE
}
emit:
reqlen = xcode->len + xcode->count;
len = osize - j;
if (len < reqlen)
{
iobuf->osize += reqlen;
return mu_filter_moreoutput;
}
for (k = 0; k < xcode->count; k++, j++)
optr[j] = '>';
memcpy (optr + j, from_line, xcode->len);
j += xcode->len;
xcode->state = S_INIT;
xcode->count = xcode->len = 0;
i--;
iptr--;
}
}
iobuf->isize = i;
iobuf->osize = j;
return mu_filter_ok;
}
static int
_fromrd_alloc_state (void **pret, int mode,
int argc MU_ARG_UNUSED, const char **argv MU_ARG_UNUSED)
{
*pret = malloc (sizeof (struct transcoder));
if (!*pret)
return ENOMEM;
return 0;
}
static struct _mu_filter_record _fromrd_filter = {
"FROMRD",
_fromrd_alloc_state,
_fromrd_encoder,
_fromrd_decoder
};
mu_filter_record_t mu_fromrd_filter = &_fromrd_filter;
/* For compatibility with previous versions */
static struct _mu_filter_record _fromrb_filter = {
"FROMRB",
_fromrd_alloc_state,
_fromrd_encoder,
_fromrd_decoder
};
mu_filter_record_t mu_fromrb_filter = &_fromrb_filter;
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