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/*
* Based on node-yencode library by Anime Tosho:
* https://github.com/animetosho/node-yencode
*
* Copyright (C) 2017 Anime Tosho (animetosho)
* Copyright (C) 2017 Andrey Prygunkov <hugbug@users.sourceforge.net>
*
* 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, see <http://www.gnu.org/licenses/>.
*/
#include "nzbget.h"
#include "YEncode.h"
namespace YEncode
{
// return values:
// - 0: no end sequence found
// - 1: \r\n=y sequence found, src points to byte after 'y'
// - 2: \r\n.\r\n sequence found, src points to byte after last '\n'
int decode_scalar(const unsigned char** src, unsigned char** dest, size_t len, YencDecoderState* state) {
const unsigned char *es = (*src) + len; // end source pointer
unsigned char *p = *dest; // destination pointer
long i = -(long)len; // input position
unsigned char c; // input character
if(len < 1) return 0;
#define YDEC_CHECK_END(s) if(i == 0) { \
*state = s; \
*src = es; \
*dest = p; \
return 0; \
}
if(state) switch(*state) {
case YDEC_STATE_CRLFEQ: do_decode_endable_scalar_ceq:
if(es[i] == 'y') {
*state = YDEC_STATE_NONE;
*src = es+i+1;
*dest = p;
return 1;
} // else fall thru and escape
case YDEC_STATE_EQ:
c = es[i];
*p++ = c - 42 - 64;
i++;
if(c != '\r') break;
YDEC_CHECK_END(YDEC_STATE_CR)
// fall through
case YDEC_STATE_CR:
if(es[i] != '\n') break;
i++;
YDEC_CHECK_END(YDEC_STATE_CRLF)
case YDEC_STATE_CRLF: do_decode_endable_scalar_c0:
if(es[i] == '.') {
i++;
YDEC_CHECK_END(YDEC_STATE_CRLFDT)
// fallthru
} else if(es[i] == '=') {
i++;
YDEC_CHECK_END(YDEC_STATE_CRLFEQ)
goto do_decode_endable_scalar_ceq;
} else
break;
case YDEC_STATE_CRLFDT:
if(es[i] == '\r') {
i++;
YDEC_CHECK_END(YDEC_STATE_CRLFDTCR)
// fallthru
} else if(es[i] == '=') { // check for dot-stuffed ending: \r\n.=y
i++;
YDEC_CHECK_END(YDEC_STATE_CRLFEQ)
goto do_decode_endable_scalar_ceq;
} else
break;
case YDEC_STATE_CRLFDTCR:
if(es[i] == '\n') {
*state = YDEC_STATE_CRLF;
*src = es + i + 1;
*dest = p;
return 2;
} else
break;
case YDEC_STATE_NONE: break; // silence compiler warning
} else // treat as YDEC_STATE_CRLF
goto do_decode_endable_scalar_c0;
for(; i < -2; i++) {
c = es[i];
switch(c) {
case '\r': {
if(es[i+1] == '\n') {
c = es[i+2];
if(c == '.') {
// skip past \r\n. sequences
i += 3;
YDEC_CHECK_END(YDEC_STATE_CRLFDT)
// check for end
if(es[i] == '\r') {
i++;
YDEC_CHECK_END(YDEC_STATE_CRLFDTCR)
if(es[i] == '\n') {
*src = es + i + 1;
*dest = p;
*state = YDEC_STATE_CRLF;
return 2;
} else i--;
} else if(es[i] == '=') {
i++;
YDEC_CHECK_END(YDEC_STATE_CRLFEQ)
if(es[i] == 'y') {
*src = es + i + 1;
*dest = p;
*state = YDEC_STATE_NONE;
return 1;
} else {
// escape char & continue
c = es[i];
*p++ = c - 42 - 64;
i -= (c == '\r');
}
} else i--;
}
else if(c == '=') {
i += 3;
YDEC_CHECK_END(YDEC_STATE_CRLFEQ)
if(es[i] == 'y') {
// ended
*src = es + i + 1;
*dest = p;
*state = YDEC_STATE_NONE;
return 1;
} else {
// escape char & continue
c = es[i];
*p++ = c - 42 - 64;
i -= (c == '\r');
}
}
}
} case '\n':
continue;
case '=':
c = es[i+1];
*p++ = c - 42 - 64;
i += (c != '\r'); // if we have a \r, reprocess character to deal with \r\n. case
continue;
default:
*p++ = c - 42;
}
}
if(state) *state = YDEC_STATE_NONE;
if(i == -2) { // 2nd last char
c = es[i];
switch(c) {
case '\r':
if(state && es[i+1] == '\n') {
*state = YDEC_STATE_CRLF;
*src = es;
*dest = p;
return 0;
}
case '\n':
break;
case '=':
c = es[i+1];
*p++ = c - 42 - 64;
i += (c != '\r');
break;
default:
*p++ = c - 42;
}
i++;
}
// do final char; we process this separately to prevent an overflow if the final char is '='
if(i == -1) {
c = es[i];
if(c != '\n' && c != '\r' && c != '=') {
*p++ = c - 42;
} else if(state) {
if(c == '=') *state = YDEC_STATE_EQ;
else if(c == '\r') *state = YDEC_STATE_CR;
else *state = YDEC_STATE_NONE;
}
}
#undef YDEC_CHECK_END
*src = es;
*dest = p;
return 0;
}
void init_decode_scalar() {
decode = decode_scalar;
}
}
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