ponysay/ponysaytruncater.c

/**
 * ponysaytruncater — Output truncater used by ponysay to stop large ponies from being printed badly.
 * 
 * DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
 * See COPYING for details
 */
#include <stdio.h>


#define  String   char*
#define  boolean  char

#define  true     1
#define  false    0



/**
 * Stdin file descriptor ID
 */
#define  STDIN  0



/**
 * The number of columns on the current line
 */
static int x =  0;

/**
 * Escape sequence state
 */
static int esc = 0;

/**
 * Last bytes as written
 */
static boolean ok = true;




void write(char b, int width);
int toInt(String string);



/**
 * <p>Mane method!</p>
 * <p>
 *   The only argument, in addition to the executed file,
 *   should be the width of the terminal which you get by
 *   adding <code>`tput cols || echo 0`</code> as and argument.
 * </p>
 * 
 * @param  argc  The number of startup arguments
 * @param  argv  The startup arguments, the first is the file itself
 * 
 * @author  Mattias Andrée, maandree@kth.se
 */
void main(int argc, String* argv)
{
    int width = 0;
    if (argc > 1)
        width = toInt(*(argv + 1));
    
    char b = 0;
    
    if (width > 15) //sanity
	while (read(STDIN, &b, 1))
	    write(b, width);
    else
	while (read(STDIN, &b, 1))
	    printf("%c", b);
}


/**
 * Writes a character to stdout, iff it fits within the terminal
 * 
 * @param  b      The character (byte) to write
 * @param  width  The width of the terminal
 */
void write(char b, int width)
{
    int i;
    char nx;
    
    if (esc == 0)
    {
        if (b == '\n')
	{
	    if (x >= width)
	    {
	        // Reset background colour
	        write('\e', width);
		write('[', width);
		write('4', width);
		write('9', width);
		write('m', width);
	    }
	    x = -1;
	}
	else if (b == '\t')
	{
	    // Tab to next pos ≡₈ 0
	    nx = 8 - (x & 7);
	    for (i = 0; i < nx; i++)
	        write(' ', width);
	    return; //(!)
	}
	else if (b == '\e')
	    esc = 1;
    }
    else if (esc == 1)
    {
        if      (b == '[')  esc = 2;  //CSI ends with a letter, m is for colour
	else if (b == ']')  esc = 3;  //OSI, OSI P is for palett editing in Linux VT
	else                esc = 10; //Nothing to see here, move along
    }
    else if (esc == 2)
    {
	if ((('a' <= b) && (b <= 'z')) || (('A' <= b) && (b <= 'Z')))
	    esc = 10;
    }
    else if ((esc == 3) && (b == 'P'))
    {
	esc = ~0;
    }
    else if (esc < 0)
    {
        esc--;
	if (esc == ~7)
	    esc = 10;
    }
    else
        esc = 10;
              
    if (                                // Can be printed:
	(x < width) ||                  //       within bounds   ∨ 
	(esc != 0) ||                   //     ∨ escape sequence ∨
	(ok && ((b & 0xC0) == 0x80)))   //     ∨ last with printed ∧ not first byte in character
    {
	printf("%c", b);
	if ((esc == 0) && ((b & 0xC0) != 0x80))  // Count up columns of not in escape sequnce and
	    x++;                                 // the byte is not the first byte in the character
	ok = true;
    }
    else
        ok = false;
	
    if (esc == 10)
        esc = 0;
}


/**
 * Converts a string to an integer
 * 
 * @param   string  The string to convert
 * @return          The integer represented by the string
 */
int toInt(String string)
{
    int rc = 0;
    String str = string;
    char c = 0;
    
    while ((c = *str++) != 0)
        rc = (rc << 1) + (rc << 3) - (c & 15);
    
    return -rc;
}