#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
char oldbase[65];

void do_historical(FILE *in, FILE *out, char *decode) {
	unsigned char input[45];
	unsigned char output[62];
	size_t bytes;

	fprintf(out, "begin %s %s\n", "644", decode);
	do {
		unsigned int bits;
		int i;
		input[0] = 0; input[1] = 0; input[2] = 0;
		bytes = fread(input, 1, 45, in);

		for (i = bytes; i < 45; i++) {
			input[i] = 0;
		}
		output[0] = oldbase[bytes];
		output[1] = 0;

		for (i=0;i<bytes;i+=3) {
			bits = (input[i] << 16) | (input[i+1] << 8) | (input[i+2]);

			output[i/3*4+4] = oldbase[(bits & 0x3f)];
			output[i/3*4+3] = oldbase[((bits >> 6) & 0x3f)];
			output[i/3*4+2] = oldbase[((bits >> 12) & 0x3f)];
			output[i/3*4+1] = oldbase[((bits >> 18) & 0x3f)];
			output[i/3*4+5] = 0;
		}
		fprintf(out, "%s\n", output);
	} while (bytes);
	fprintf(out, "end\n");
}

int main(int ac, char *av[]) {
	int mime = 0;
	char *file = 0;
	char *decode = 0;
	FILE *output = stdout;
	unsigned char input[3];
	int groups = 0;
	size_t bytes;
	int i;

	for (i = 0; i<64; i++) {
		oldbase[i] = i + 0x20;
	}
	oldbase[0] = '`';

	decode = av[ac-1];
	if (!strcmp(av[1], "-m")) {
		mime = 1;
		if (ac == 4) {
			file = av[ac-2];
		}
	} else if (ac == 3) {
		file = av[ac-2];
	}

	if (file) {
		if (freopen(file, "r", stdin) == 0) {
			perror("can't open file:");
			exit(EXIT_FAILURE);
		}
	}

	if (!mime) {
		do_historical(stdin, output, decode);
		exit(EXIT_SUCCESS);
	}

	fprintf(output, "begin-base64 %s %s\n", "644", decode);

	do {
		unsigned char out[4];
		unsigned int bits;
		int i;
		input[0] = 0; input[1] = 0; input[2] = 0;
		bytes = fread(input, 1, 3, stdin);
		if (!bytes) {
			continue;
		}
		bits = (input[0] << 16) | (input[1] << 8) | (input[2]);

		out[3] = bits & 0x3f;
		out[2] = (bits >> 6) & 0x3f;
		out[1] = (bits >> 12) & 0x3f;
		out[0] = (bits >> 18) & 0x3f;
		
		for (i=0;i < bytes+1; i++) {
			fputc(base64[out[i]], stdout);
		}

		switch (bytes) {
			case 1:
				fputc('=', stdout);
			case 2:
				fputc('=', stdout);
		}
		if (++groups % 15 == 0) {
			fputc('\n', stdout);
		}
	} while (bytes);

	if (groups % 15 != 0) {
		fputc('\n', stdout);
	}
	fprintf(stdout, "====\n");

	return 0;
}