webindent.c

Sometimes I want to post code to a website, but they have utterly broken filters (I'm looking at you Yahoo! Answers). So that when I paste nicely indented code it goes from this:

def double(x):
    return x+x

to this:

def double(x):
return x+x

It is annoying in C or Lisp, but it is wrong in python where the syntax relies on proper indentation. When websites do this it is broken.

So I wrote a little program to rectify the situation. It processes a source file so that it looks the same or similar on the web as in your text editor.

usage: webindent < source.c > page.html

#include <stdio.h>
#define true 1
#define false 0

/* main(): get characters from stdin, replace
 * leading spaces with '&nbsp;'
 * and replace leading tabs with 4 '&nbsp;'s
 * This code is donated to the public domain */
int main()
{
    int start = true; /* we're at the start of a line */
    char *space = "&nbsp;";
    char *fourspaces = "&nbsp;&nbsp;&nbsp;&nbsp;";
    char c; /* the current char */

    while ((c = getchar()) != EOF) {
        if (c == ' ') {
            if (start)
                printf(space);
            else
                putchar(c);
        } else if (c == '\t') {
            if (start)
                printf(fourspaces);
            else
                putchar(c);
        } else if (c == '<') {
            printf("&lt;");
        } else if (c == '>') {
            printf("&gt;");
        } else if (c == '\n') {
            printf("<br />");
            putchar(c);
            start = true;
        } else if (c == '&') {
            printf("&amp;");
        } else {
            if (start)
                start = false;
            putchar(c);
        }
    }
    return 0;
}

It does a bit more than is stated in that comment, because it has to remove '&', '<' and '>' for it to be a well-formed HTML fragment. Note that I used this program to process itself.