mirror of
https://github.com/ZDoom/gzdoom.git
synced 2024-11-23 04:22:34 +00:00
147 lines
3.5 KiB
C++
147 lines
3.5 KiB
C++
/* re2c lesson 002_strip_comments, strip_001.s, (c) M. Boerger 2006 - 2007 */
|
|
/*!ignore:re2c
|
|
|
|
- basic interface for file reading
|
|
. This scanner will read chunks of input from a file. The easiest way would
|
|
be to read the whole file into a memory buffer and use that a zero
|
|
terminated string.
|
|
. Instead we want to read input chunks of a reasonable size as they are neede
|
|
by the scanner. Thus we basically need YYFILL(n) to call fread(n).
|
|
. Before we provide a buffer that we constantly reallocate we instead use
|
|
one buffer that we get from the stack or global memory just once. When we
|
|
reach the end of the buffer we simply move the beginning of our input
|
|
that is somewhere in our buffer to the beginning of our buffer and then
|
|
append the next chunk of input to the correct end inside our buffer.
|
|
. As re2c scanners might read more than one character we need to ensure our
|
|
buffer is long enough. We can use re2c to inform about the maximum size
|
|
by placing a "!max:re2c" comment somewhere. This gets translated to a
|
|
"#define YYMAXFILL <n>" line where <n> is the maximum length value. This
|
|
define can be used as precompiler condition.
|
|
|
|
- multiple scanner blocks
|
|
. We use a main scanner block that outputs every input character unless the
|
|
input is two /s or a / followed by a *. In the latter two cases we switch
|
|
to a special c++ comment and a comment block respectively.
|
|
. Both special blocks simply detect their end ignore any other character.
|
|
. The c++ block is a bit special. Since the terminating new line needs to
|
|
be output and that can either be a new line or a carridge return followed
|
|
by a new line.
|
|
. In order to ensure that we do not read behind our buffer we reset the token
|
|
pointer to the cursor on every scanner run.
|
|
*/
|
|
|
|
#include <stdlib.h>
|
|
#include <stdio.h>
|
|
#include <string.h>
|
|
|
|
/*!max:re2c */
|
|
#define BSIZE 128
|
|
|
|
#if BSIZE < YYMAXFILL
|
|
# error BSIZE must be greater YYMAXFILL
|
|
#endif
|
|
|
|
#define YYCTYPE unsigned char
|
|
#define YYCURSOR s.cur
|
|
#define YYLIMIT s.lim
|
|
#define YYFILL(n) { if ((res = fill(&s, n)) >= 0) break; }
|
|
|
|
typedef struct Scanner
|
|
{
|
|
FILE *fp;
|
|
unsigned char *cur, *tok, *lim, *eof;
|
|
unsigned char buffer[BSIZE];
|
|
} Scanner;
|
|
|
|
int fill(Scanner *s, int len)
|
|
{
|
|
if (!len)
|
|
{
|
|
s->cur = s->tok = s->lim = s->buffer;
|
|
s->eof = 0;
|
|
}
|
|
if (!s->eof)
|
|
{
|
|
int got, cnt = s->tok - s->buffer;
|
|
|
|
if (cnt > 0)
|
|
{
|
|
memcpy(s->buffer, s->tok, s->lim - s->tok);
|
|
s->tok -= cnt;
|
|
s->cur -= cnt;
|
|
s->lim -= cnt;
|
|
}
|
|
cnt = BSIZE - cnt;
|
|
if ((got = fread(s->lim, 1, cnt, s->fp)) != cnt)
|
|
{
|
|
s->eof = &s->lim[got];
|
|
}
|
|
s->lim += got;
|
|
}
|
|
else if (s->cur + len > s->eof)
|
|
{
|
|
return 0; /* not enough input data */
|
|
}
|
|
return -1;
|
|
}
|
|
|
|
int scan(FILE *fp)
|
|
{
|
|
int res = 0;
|
|
Scanner s;
|
|
|
|
if (!fp)
|
|
{
|
|
return 1; /* no file was opened */
|
|
}
|
|
|
|
s.fp = fp;
|
|
|
|
fill(&s, 0);
|
|
|
|
for(;;)
|
|
{
|
|
s.tok = s.cur;
|
|
/*!re2c
|
|
re2c:indent:top = 2;
|
|
|
|
NL = "\r"? "\n" ;
|
|
ANY = [^] ;
|
|
|
|
"/" "/" { goto cppcomment; }
|
|
"/" "*" { goto comment; }
|
|
ANY { fputc(*s.tok, stdout); continue; }
|
|
*/
|
|
comment:
|
|
s.tok = s.cur;
|
|
/*!re2c
|
|
"*" "/" { continue; }
|
|
ANY { goto comment; }
|
|
*/
|
|
cppcomment:
|
|
s.tok = s.cur;
|
|
/*!re2c
|
|
NL { fwrite(s.tok, 1, s.cur - s.tok, stdout); continue; }
|
|
ANY { goto cppcomment; }
|
|
*/
|
|
}
|
|
|
|
if (fp != stdin)
|
|
{
|
|
fclose(fp); /* close only if not stdin */
|
|
}
|
|
return res; /* return result */
|
|
}
|
|
|
|
int main(int argc, char **argv)
|
|
{
|
|
if (argc > 1)
|
|
{
|
|
return scan(!strcmp(argv[1], "-") ? stdin : fopen(argv[1], "r"));
|
|
}
|
|
else
|
|
{
|
|
fprintf(stderr, "%s <expr>\n", argv[0]);
|
|
return 1;
|
|
}
|
|
}
|