107 lines
1.8 KiB
C
107 lines
1.8 KiB
C
#include <stdio.h>
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/* This file contains the scanner for mylex(), the following functions and
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* variables are exported :
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*
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* int yylineno; - The current line number.
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*
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* char scanc(); - Return next character.
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*
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* backc( c); - Push back one character.
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* char c;
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*
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* FILE *switch_input( new); - Scanner will from now on read from
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* FILE *new; - 'new', old input-file is returned.
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*
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* The scanner must perform a lookahead of more than one character, so it uses
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* it's own internal buffer.
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*/
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int yylineno = 1;
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/********* Internal variables + functions ***********************/
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#define BUF_SIZE 16
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static char buf[BUF_SIZE], /* Bufer to save backc()-characters */
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*bufptr = buf; /* Pointer to space for backc()-character */
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static FILE *infile = stdin;
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static char nextc()
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{
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if ( bufptr > buf)
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return( *--bufptr);
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else
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return( getc( infile));
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}
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/***************************************************************/
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char scanc()
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/* Get next character, but delete al C-comments and count lines */
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{
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char c, nextc();
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c = nextc();
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while ( c == '/') {
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c = nextc();
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if ( c == '*') { /* start of comment */
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while ( nextc() != '*' || nextc() != '/')
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;
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c = nextc();
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}
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else {
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backc( c);
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return( '/');
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}
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}
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if ( c == '\n')
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yylineno++;
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return( c);
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}
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backc( c)
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char c;
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{
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if ( bufptr >= buf + BUF_SIZE)
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error( "backc(), no space in buffer left!");
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else {
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if ( c == '\n')
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yylineno--;
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*bufptr++ = c;
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}
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}
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FILE *switch_input( new)
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FILE *new;
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/* Switch to a new input file, try to save the lookahead-characters in buf[]
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* by calling ungetc(). If they can't be saved return NULL.
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*/
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{
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char *ptr; FILE *old;
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/* Clean buf[] */
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for ( ptr = buf; ptr < bufptr; ptr++)
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if ( ungetc( *ptr, infile) == EOF && *ptr != EOF)
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return( NULL);
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bufptr = buf;
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old = infile;
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infile = new;
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return( old);
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}
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