diff options
Diffstat (limited to 'urt/rle_getskip.c')
| -rw-r--r-- | urt/rle_getskip.c | 162 |
1 files changed, 162 insertions, 0 deletions
diff --git a/urt/rle_getskip.c b/urt/rle_getskip.c new file mode 100644 index 00000000..f1c333e7 --- /dev/null +++ b/urt/rle_getskip.c @@ -0,0 +1,162 @@ +/* + * This software is copyrighted as noted below. It may be freely copied, + * modified, and redistributed, provided that the copyright notice is + * preserved on all copies. + * + * There is no warranty or other guarantee of fitness for this software, + * it is provided solely "as is". Bug reports or fixes may be sent + * to the author, who may or may not act on them as he desires. + * + * You may not include this software in a program or other software product + * without supplying the source, or without informing the end-user that the + * source is available for no extra charge. + * + * If you modify this software, you should include a notice giving the + * name of the person performing the modification, the date of modification, + * and the reason for such modification. + */ +/* + * rle_getskip.c - Skip scanlines on input. + * + * Author: Spencer W. Thomas + * EECS Dept. + * University of Michigan + * Date: Wed Jun 27 1990 + * Copyright (c) 1990, University of Michigan + */ + +#include "rle.h" +#include "rle_code.h" + +/* Read a two-byte "short" that started in VAX (LITTLE_ENDIAN) order */ +#define VAXSHORT( var, fp )\ + { var = fgetc(fp)&0xFF; var |= (fgetc(fp)) << 8; } + +/* Instruction format -- first byte is opcode, second is datum. */ + +#define OPCODE(inst) (inst[0] & ~LONG) +#define LONGP(inst) (inst[0] & LONG) +#define DATUM(inst) (inst[1] & 0xff) /* Make sure it's unsigned. */ + +/***************************************************************** + * TAG( rle_getskip ) + * + * Skip the next scanline with data on it. + * Most useful for skipping to end-of-image. + * Inputs: + * the_hdr: Describes input image. + * Outputs: + * Returns the number of the next scanline. At EOF returns 32768. + * Assumptions: + * rle_get_setup has been called. + * Algorithm: + * Read input to the beginning of the next scanline, or to EOF or + * end of image. + */ +unsigned int +rle_getskip( the_hdr ) +rle_hdr *the_hdr; +{ + unsigned char inst[2]; + register FILE *infile = the_hdr->rle_file; + int nc; + + /* Add in vertical skip from last scanline */ + if ( the_hdr->priv.get.vert_skip > 0) + the_hdr->priv.get.scan_y += the_hdr->priv.get.vert_skip; + the_hdr->priv.get.vert_skip = 0; + + if ( the_hdr->priv.get.is_eof ) + return 32768; /* too big for 16 bits, signal EOF */ + + /* Otherwise, read and interpret instructions until a skipLines + * instruction is encountered. + */ + for (;;) + { + inst[0] = getc( infile ); + inst[1] = getc( infile ); + if ( feof(infile) ) + { + the_hdr->priv.get.is_eof = 1; + break; /* <--- one of the exits */ + } + + switch( OPCODE(inst) ) + { + case RSkipLinesOp: + if ( LONGP(inst) ) + { + VAXSHORT( the_hdr->priv.get.vert_skip, infile ); + } + else + the_hdr->priv.get.vert_skip = DATUM(inst); + break; /* need to break for() here, too */ + + case RSetColorOp: + /* No-op here. */ + break; + + case RSkipPixelsOp: + if ( LONGP(inst) ) + { + (void)getc( infile ); + (void)getc( infile ); + } + break; + + case RByteDataOp: + if ( LONGP(inst) ) + { + VAXSHORT( nc, infile ); + } + else + nc = DATUM(inst); + nc++; + if ( the_hdr->priv.get.is_seek ) + fseek( infile, ((nc + 1) / 2) * 2, 1 ); + else + { + register int ii; + for ( ii = ((nc + 1) / 2) * 2; ii > 0; ii-- ) + (void) getc( infile ); /* discard it */ + } + + break; + + case RRunDataOp: + if ( LONGP(inst) ) + { + (void)getc( infile ); + (void)getc( infile ); + } + (void)getc( infile ); + (void)getc( infile ); + break; + + case REOFOp: + the_hdr->priv.get.is_eof = 1; + break; + + default: + fprintf( stderr, + "%s: rle_getskip: Unrecognized opcode: %d, reading %s\n", + the_hdr->cmd, OPCODE(inst), the_hdr->file_name ); + exit(1); + } + if ( OPCODE(inst) == REOFOp ) + break; /* <--- the other loop exit */ + if ( OPCODE(inst) == RSkipLinesOp ) + break; + } + + /* Return the number of the NEXT scanline. */ + the_hdr->priv.get.scan_y += + the_hdr->priv.get.vert_skip; + the_hdr->priv.get.vert_skip = 0; + + if ( the_hdr->priv.get.is_eof ) + return 32768; /* too big for 16 bits, signal EOF */ + else + return the_hdr->priv.get.scan_y; +} |