unsigned int abitreader::read( int nbits )
{
unsigned int retval = 0;
// safety check for eof
if ( eof ) {
peof += nbits;
return 0;
}
while ( nbits >= cbit ) {
nbits -= cbit;
retval |= ( RBITS( data[cbyte], cbit ) << nbits );
cbit = 8;
if ( ++cbyte >= lbyte ) {
peof = nbits;
eof = true;
return retval;
}
}
if ( nbits > 0 ) {
retval |= ( MBITS( data[cbyte], cbit, (cbit-nbits) ) );
cbit -= nbits;
}
return retval;
}
/* -----------------------------------------------
Parse routines for JFIF segments
----------------------------------------------- */
bool parse_jfif_jpg( unsigned char type, unsigned int len, unsigned char* segment )
{
unsigned int hpos = 4; // current position in segment, start after segment header
int lval, rval; // temporary variables
int cmp;
int i;
switch ( type )
{
case 0xC4: // DHT segment
// build huffman trees & codes
// nothing to do here!
return true;
case 0xDB: // DQT segment
// copy quantization tables to internal memory
while ( hpos < len ) {
lval = LBITS( segment[ hpos ], 4 );
rval = RBITS( segment[ hpos ], 4 );
if ( (lval < 0) || (lval >= 2) ) break;
if ( (rval < 0) || (rval >= 4) ) break;
hpos++;
if ( lval == 0 ) { // 8 bit precision
for ( i = 0; i < 64; i++ ) {
qtables[ rval ][ i ] = ( unsigned short ) segment[ hpos + i ];
if ( qtables[ rval ][ i ] == 0 ) break;
}
hpos += 64;
}
else { // 16 bit precision
for ( i = 0; i < 64; i++ ) {
qtables[ rval ][ i ] =
B_SHORT( segment[ hpos + (2*i) ], segment[ hpos + (2*i) + 1 ] );
if ( qtables[ rval ][ i ] == 0 ) break;
}
hpos += 128;
}
}
if ( hpos != len ) {
// if we get here, something went wrong
sprintf( errormessage, "size mismatch in dqt marker" );
errorlevel = 2;
return false;
}
return true;
case 0xDD: // DRI segment
// define restart interval
rsti = B_SHORT( segment[ hpos ], segment[ hpos + 1 ] );
return true;
case 0xDA: // SOS segment
// prepare next scan
cs_cmpc = segment[ hpos ];
if ( cs_cmpc > cmpc ) {
sprintf( errormessage, "%i components in scan, only %i are allowed",
cs_cmpc, cmpc );
errorlevel = 2;
return false;
}
hpos++;
for ( i = 0; i < cs_cmpc; i++ ) {
for ( cmp = 0; ( segment[ hpos ] != cmpnfo[ cmp ].jid ) && ( cmp < cmpc ); cmp++ );
if ( cmp == cmpc ) {
sprintf( errormessage, "component id mismatch in start-of-scan" );
errorlevel = 2;
return false;
}
cs_cmp[ i ] = cmp;
cmpnfo[ cmp ].huffdc = LBITS( segment[ hpos + 1 ], 4 );
cmpnfo[ cmp ].huffac = RBITS( segment[ hpos + 1 ], 4 );
if ( ( cmpnfo[ cmp ].huffdc < 0 ) || ( cmpnfo[ cmp ].huffdc >= 4 ) ||
( cmpnfo[ cmp ].huffac < 0 ) || ( cmpnfo[ cmp ].huffac >= 4 ) ) {
sprintf( errormessage, "huffman table number mismatch" );
errorlevel = 2;
return false;
}
hpos += 2;
}
cs_from = segment[ hpos + 0 ];
cs_to = segment[ hpos + 1 ];
cs_sah = LBITS( segment[ hpos + 2 ], 4 );
cs_sal = RBITS( segment[ hpos + 2 ], 4 );
// check for errors
if ( ( cs_from > cs_to ) || ( cs_from > 63 ) || ( cs_to > 63 ) ) {
sprintf( errormessage, "spectral selection parameter out of range" );
errorlevel = 2;
return false;
}
if ( ( cs_sah >= 12 ) || ( cs_sal >= 12 ) ) {
sprintf( errormessage, "successive approximation parameter out of range" );
errorlevel = 2;
return false;
}
return true;
case 0xC0: // SOF0 segment
// coding process: baseline DCT
case 0xC1: // SOF1 segment
// coding process: extended sequential DCT
case 0xC2: // SOF2 segment
// coding process: progressive DCT
// set JPEG coding type
if ( type == 0xC2 )
jpegtype = 2;
else
jpegtype = 1;
// check data precision, only 8 bit is allowed
lval = segment[ hpos ];
if ( lval != 8 ) {
sprintf( errormessage, "%i bit data precision is not supported", lval );
errorlevel = 2;
return false;
}
// image size, height & component count
imgheight = B_SHORT( segment[ hpos + 1 ], segment[ hpos + 2 ] );
imgwidth = B_SHORT( segment[ hpos + 3 ], segment[ hpos + 4 ] );
cmpc = segment[ hpos + 5 ];
if ( cmpc > 4 ) {
sprintf( errormessage, "image has %i components, max 4 are supported", cmpc );
errorlevel = 2;
return false;
}
hpos += 6;
// components contained in image
for ( cmp = 0; cmp < cmpc; cmp++ ) {
cmpnfo[ cmp ].jid = segment[ hpos ];
cmpnfo[ cmp ].sfv = LBITS( segment[ hpos + 1 ], 4 );
cmpnfo[ cmp ].sfh = RBITS( segment[ hpos + 1 ], 4 );
cmpnfo[ cmp ].qtable = qtables[ segment[ hpos + 2 ] ];
cmpnfo[ cmp ].qtblno = segment[ hpos + 2 ];
hpos += 3;
}
return true;
case 0xC3: // SOF3 segment
// coding process: lossless sequential
sprintf( errormessage, "sof3 marker found, image is coded lossless" );
errorlevel = 2;
return false;
case 0xC5: // SOF5 segment
// coding process: differential sequential DCT
sprintf( errormessage, "sof5 marker found, image is coded diff. sequential" );
errorlevel = 2;
return false;
case 0xC6: // SOF6 segment
// coding process: differential progressive DCT
sprintf( errormessage, "sof6 marker found, image is coded diff. progressive" );
errorlevel = 2;
return false;
case 0xC7: // SOF7 segment
// coding process: differential lossless
sprintf( errormessage, "sof7 marker found, image is coded diff. lossless" );
errorlevel = 2;
return false;
case 0xC9: // SOF9 segment
// coding process: arithmetic extended sequential DCT
sprintf( errormessage, "sof9 marker found, image is coded arithm. sequential" );
errorlevel = 2;
return false;
case 0xCA: // SOF10 segment
// coding process: arithmetic extended sequential DCT
sprintf( errormessage, "sof10 marker found, image is coded arithm. progressive" );
errorlevel = 2;
return false;
case 0xCB: // SOF11 segment
// coding process: arithmetic extended sequential DCT
sprintf( errormessage, "sof11 marker found, image is coded arithm. lossless" );
errorlevel = 2;
return false;
case 0xCD: // SOF13 segment
// coding process: arithmetic differntial sequential DCT
sprintf( errormessage, "sof13 marker found, image is coded arithm. diff. sequential" );
errorlevel = 2;
return false;
case 0xCE: // SOF14 segment
// coding process: arithmetic differential progressive DCT
sprintf( errormessage, "sof14 marker found, image is coded arithm. diff. progressive" );
errorlevel = 2;
return false;
case 0xCF: // SOF15 segment
// coding process: arithmetic differntial lossless
sprintf( errormessage, "sof15 marker found, image is coded arithm. diff. lossless" );
errorlevel = 2;
return false;
case 0xE0: // APP0 segment
case 0xE1: // APP1 segment
case 0xE2: // APP2 segment
case 0xE3: // APP3 segment
case 0xE4: // APP4 segment
case 0xE5: // APP5 segment
case 0xE6: // APP6 segment
case 0xE7: // APP7 segment
case 0xE8: // APP8 segment
case 0xE9: // APP9 segment
case 0xEA: // APP10 segment
case 0xEB: // APP11 segment
case 0xEC: // APP12segment
case 0xED: // APP13 segment
case 0xEE: // APP14 segment
case 0xEF: // APP15 segment
case 0xFE: // COM segment
// do nothing - return true
return true;
case 0xD0: // RST0 segment
case 0xD1: // RST1segment
case 0xD2: // RST2 segment
case 0xD3: // RST3 segment
case 0xD4: // RST4 segment
case 0xD5: // RST5 segment
case 0xD6: // RST6 segment
case 0xD7: // RST7 segment
// return errormessage - RST is out of place here
sprintf( errormessage, "rst marker found out of place" );
errorlevel = 2;
return false;
case 0xD8: // SOI segment
// return errormessage - start-of-image is out of place here
sprintf( errormessage, "soi marker found out of place" );
errorlevel = 2;
return false;
case 0xD9: // EOI segment
// return errormessage - end-of-image is out of place here
sprintf( errormessage, "eoi marker found out of place" );
errorlevel = 2;
return false;
default: // unknown marker segment
// return warning
sprintf( errormessage, "unknown marker found: FF %2X", type );
errorlevel = 1;
return true;
}
}
