源程序-删除c源文件中的注释

前一周做得一道笔试题。
 /*
 *  comment_strip.c - strip all the comments in a c source file.
 *  Created : Fri Sep  1 21:38:40 2006
 *  Zhang Xuecheng <zhangxuecheng1985@gmail.com>
 * 
 *  usage:  comment_strip input_file output_file
 */

/* 
   version: 2.0
 
   changelog:
   *** fix the bug of "//" , "/*" & "*//" in the former version
   *** fix the new bug of '"' in the beta version of 2.0
   *** optimize the performance by using if...else if... instead of seperate if()
   *** add makefile and debug info.
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#ifdef DEBUG
#define dump() fprintf(stderr,"%c/t",c1);       /
    fprintf(stderr,"%c/t",c2);                  /
    fprintf(stderr,"%d/t",flg_token1);          /
    fprintf(stderr,"%d/t",flg_token2);          /
    fprintf(stderr,"%d/t",flg_omit_output);     /
    fprintf(stderr,"%d/t",flg_quote);           /
    fprintf(stderr,"/n");
#endif

int main (int argc, char *argv[])
{
    FILE *fp_src, *fp_dst;      /* stream for source & destination file */
    char c1 = ' ', c2 = ' ';

    /* below are flags for comments stripping,
       if "//" is probed,token1 is set,omit_output is set,output is disabled,
       if "/*" is probed,token2 is set,omit_output is set,output is disabled.
       if token1 is set & "/n" is probed,_or_ token2 is set & "*//" is probed,
       token1 or token2 is cleared,output is enabled,
       the process of stripping token1&2 should be atomic,
       at one time,only _one_ token should be stripped.        
 */
    int flg_token1 = 0;
    int flg_token2 = 0;
    int flg_omit_output = 0;
    int flg_quote = 0;

    if (3 != argc)
        {
            fprintf (stderr, "please specify the source & destination file/n");
            return 0;
        }

    if (NULL == (fp_src = fopen (argv[1], "r")))
        {
            fprintf (stderr, "can't open source file %s /n", argv[1]);
            return 0;
        }

    if (NULL == (fp_dst = fopen (argv[2], "w")))
        {
            fprintf (stderr, "can't create destination file %s /n", argv[2]);
            return 0;
        }

#ifdef DEBUG
    fprintf(stderr,"c1/tc2/ttoken1/ttoken2/toutput/tquote/n");
#endif

    while (!feof (fp_src))
        {
            c1 = fgetc (fp_src);

            /* probe whether " is begin */
            if ('"' == c1 && !flg_token2 && !flg_token1)
                {
                    c1=fgetc(fp_src);
                    if('/''==c1 && '/'' == c2)
                        {
                            flg_quote = !flg_quote;
                        }
                    ungetc(c1,fp_src);
                    c1='"';
                    flg_quote = !flg_quote;
                }
            else if            /* probe whether "//" is begin */
                ('/' == c2 && '/' == c1 && !flg_token2 && !flg_token1 && !flg_quote)
                {
                    flg_token1 = 1;
                    flg_omit_output = 1;
                }
            else if            /* probe whether "/*" is begin */
                ('/' == c2 && '*' == c1 && !flg_token1 && !flg_token2 && !flg_quote)
                {
                    flg_token2 = 1;
                    flg_omit_output = 1;
                }
            else if            /* probe whether a line begin with "//" is end */
                ('/n' == c2 && flg_token1 && !flg_token2 && !flg_quote)
                {
                    flg_token1 = 0;
                    flg_omit_output = 0;
                }
            else if            /* probe whether a string begin with "/*" is end */
                ('*' == c2 && '/' == c1 && flg_token2 && !flg_token1 && !flg_quote)
                {
                    flg_token2 = 0;
                    flg_omit_output = 0;
                    c2 = ' ';
                    c1 = fgetc (fp_src);
                }
#ifdef DEBUG
            dump();
#endif
            /* if no token is being stripped now,output the char */
            if (!flg_omit_output)
                {
                    fputc (c2, fp_dst);
                }

            /* use c2 as the buffer of c1 */
            c2 = c1;

        }

    return 0;
}