/* This program is free software. It comes without any warranty, to
 * the extent permitted by applicable law. You can redistribute it
 * and/or modify it under the terms of the Do What The Fuck You Want
 * To Public License, Version 2, as published by Sam Hocevar. See
 * http://www.wtfpl.net/ for more details. */

#include <ctype.h>
#include <stdio.h>
#include <string.h>
#ifdef _WIN32
#	include <fcntl.h>
#	include <io.h>
#endif

const char BASE64[] =
	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

/* put 4 chars, maintain col width */
void put4(int src[4], int colwidth) {
	static int col = 0;
	int i;
	for(i = 0; i < 4; ++i) {
		putchar(src[i]);
		++col;
		if(colwidth > 0 && col == colwidth) {
			putchar('\n');
			col = 0;
		}
	}
}

/* read binary and write base64 */
void encode(int colwidth) {
	int w[4], r[3];
#ifdef _WIN32
	_setmode(STDIN_FILENO, _O_BINARY);
#endif
	for(; ; ) {
		if((r[0] = getchar()) == EOF) {
			return;
		}
		w[0] = BASE64[r[0] >> 2];
		w[1] = BASE64[(r[0] & 3) << 4];
		w[2] = '=';
		w[3] = '=';
		if((r[1] = getchar()) == EOF) {
			put4(w, colwidth);
			return;
		}
		w[1] = BASE64[((r[0] & 3) << 4) | (r[1] >> 4)];
		w[2] = BASE64[(r[1] & 15) << 2];
		if((r[2] = getchar()) == EOF) {
			put4(w, colwidth);
			return;
		}
		w[2] = BASE64[((r[1] & 15) << 2) | (r[2] >> 6)];
		w[3] = BASE64[r[2] & 63];
		put4(w, colwidth);
	}
}

/* read base64 and write binary */
void decode(void) {
	int c, r[4], i;
	char *p;
#ifdef _WIN32
	_setmode(STDOUT_FILENO, _O_BINARY);
#endif
	for(; ; ) {
		for(i = 0; i < 4 && (c = getchar()) != EOF; ) {
			if((p = strchr(BASE64, c)) != NULL)
				r[i++] = p - BASE64;
		}
		if(i == 0 || i == 1)
			return;  /* ==== or x=== (actually invalid) */
		putchar((r[0] << 2) | (r[1] >> 4));
		if(i == 2)
			return;  /* xx== */
		putchar(((r[1] & 15) << 4) | (r[2] >> 2));
		if(i == 3)
			return;  /* xxx= */
		putchar((r[2] << 6) | r[3]);
	}
}

int main(int argc, char *argv[]) {
	int i, ncol = 76, mode = 0;
	for(i = 1; i < argc; ++i) {
		if(!strncmp(argv[i], "-w=", 3))
			ncol = atoi(&argv[i][3]);
		else if(!strncmp(argv[i], "--wrap=", 7))
			ncol = atoi(&argv[i][7]);
		else if(!strcmp(argv[i], "-d")
		|| !strcmp(argv[i], "--decode"))
			mode = 1;
		else if(!strcmp(argv[i], "--help")) {
			printf("Usage: %s [--help] [-d | --decode] [-w | --"
			"wrap=COLS]\nInvalid commands are ignored.\nRead fr"
			"om stdin, write to stdout.\nIf COLS is 0 or not a "
			"valid number, no wrapping is performed. Default to"
			" 76.\n", argv[0]);
			return 0;
		}
	}
	if(mode)
		decode();
	else
		encode(ncol);
	return 0;
}