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163 lines
3.6 KiB
ReasonML
163 lines
3.6 KiB
ReasonML
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/* re2c lesson 002_strip_comments, strip_002.s, (c) M. Boerger 2006 - 2007 */
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/*!ignore:re2c
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- complexity
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. When a comment is preceeded by a new line and followed by whitespace and a
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new line then we can drop the trailing whitespace and new line.
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. Additional to what we strip out already what about two consequtive comment
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blocks? When two comments are only separated by whitespace we want to drop
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both. In other words when detecting the end of a comment block we need to
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check whether it is followed by only whitespace and the a new comment in
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which case we continure ignoring the input. If it is followed only by white
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space and a new line we strip out the new white space and new line. In any
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other case we start outputting all that follows.
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But we cannot simply use the following two rules:
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"*" "/" WS* "/" "*" { continue; }
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"*" "/" WS* NL { continue; }
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The main problem is that WS* can get bigger then our buffer, so we need a
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new scanner.
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. Meanwhile our scanner gets a bit more complex and we have to add two more
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things. First the scanner code now uses a YYMARKER to store backtracking
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information.
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- backtracking information
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. When the scanner has two rules that can have the same beginning but a
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different ending then it needs to store the position that identifies the
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common part. This is called backtracking. As mentioned above re2c expects
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you to provide compiler define YYMARKER and a pointer variable.
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. When shifting buffer contents as done in our fill function the marker needs
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to be corrected, too.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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/*!max:re2c */
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#define BSIZE 128
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#if BSIZE < YYMAXFILL
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# error BSIZE must be greater YYMAXFILL
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#endif
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#define YYCTYPE unsigned char
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#define YYCURSOR s.cur
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#define YYLIMIT s.lim
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#define YYMARKER s.mrk
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#define YYFILL(n) { if ((res = fill(&s, n)) >= 0) break; }
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typedef struct Scanner
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{
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FILE *fp;
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unsigned char *cur, *tok, *lim, *eof, *mrk;
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unsigned char buffer[BSIZE];
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} Scanner;
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int fill(Scanner *s, int len)
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{
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if (!len)
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{
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s->cur = s->tok = s->lim = s->mrk = s->buffer;
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s->eof = 0;
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}
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if (!s->eof)
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{
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int got, cnt = s->tok - s->buffer;
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if (cnt > 0)
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{
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memcpy(s->buffer, s->tok, s->lim - s->tok);
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s->tok -= cnt;
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s->cur -= cnt;
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s->lim -= cnt;
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s->mrk -= cnt;
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}
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cnt = BSIZE - cnt;
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if ((got = fread(s->lim, 1, cnt, s->fp)) != cnt)
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{
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s->eof = &s->lim[got];
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}
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s->lim += got;
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}
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else if (s->cur + len > s->eof)
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{
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return 0; /* not enough input data */
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}
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return -1;
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}
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void echo(Scanner *s)
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{
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fwrite(s->tok, 1, s->cur - s->tok, stdout);
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}
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int scan(FILE *fp)
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{
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int res = 0;
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Scanner s;
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if (!fp)
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{
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return 1; /* no file was opened */
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}
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s.fp = fp;
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fill(&s, 0);
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for(;;)
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{
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s.tok = s.cur;
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/*!re2c
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re2c:indent:top = 2;
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NL = "\r"? "\n" ;
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WS = [\r\n\t ] ;
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ANY = [^] ;
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"/" "/" { goto cppcomment; }
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"/" "*" { goto comment; }
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ANY { fputc(*s.tok, stdout); continue; }
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*/
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comment:
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s.tok = s.cur;
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/*!re2c
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"*" "/" { goto commentws; }
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ANY { goto comment; }
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*/
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commentws:
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s.tok = s.cur;
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/*!re2c
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NL { echo(&s); continue; }
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WS { goto commentws; }
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ANY { echo(&s); continue; }
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*/
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cppcomment:
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s.tok = s.cur;
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/*!re2c
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NL { echo(&s); continue; }
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ANY { goto cppcomment; }
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*/
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}
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if (fp != stdin)
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{
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fclose(fp); /* close only if not stdin */
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}
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return res; /* return result */
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}
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int main(int argc, char **argv)
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{
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if (argc > 1)
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{
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return scan(!strcmp(argv[1], "-") ? stdin : fopen(argv[1], "r"));
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}
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else
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{
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fprintf(stderr, "%s <expr>\n", argv[0]);
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return 1;
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}
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}
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