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