Lexical-Analyser/preprocessor.c at main · sheethal126/Lexical-Analyser · GitHub

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#include <stdio.h>

void preprocess(char *input, char *output)
{
    FILE *fp1 = fopen(input, "r");
    FILE *fp2 = fopen(output, "w");

    char ch, next;
    int in_comment = 0;

    while ((ch = fgetc(fp1)) != EOF)
    {
        /* Remove preprocessor lines */
        if (ch == '#')
        {
            while ((ch = fgetc(fp1)) != '\n');
            continue;
        }

        /* Remove comments */
        if (ch == '/')
        {
            next = fgetc(fp1);

            /* single-line comment */
            if (next == '/')
            {
                while ((ch = fgetc(fp1)) != '\n');
                continue;
            }

            /* multi-line comment */
            if (next == '*')
            {
                while (1)
                {
                    ch = fgetc(fp1);
                    next = fgetc(fp1);
                    if (ch == '*' && next == '/')
                        break;
                }
                continue;
            }

            /* not a comment */
            fputc(ch, fp2);
            fputc(next, fp2);
            continue;
        }

        fputc(ch, fp2);
    }

    fclose(fp1);
    fclose(fp2);
}