utils

base64.c (3229B)

// Collection of Unix tools, comparable to coreutils
// SPDX-FileCopyrightText: 2017-2023 Haelwenn (lanodan) Monnier <contact+utils@hacktivis.me>
// SPDX-License-Identifier: MPL-2.0
#define _POSIX_C_SOURCE 200809L
#include <assert.h> /* assert */
#include <errno.h>  /* errno */
#include <fcntl.h>  /* open(), O_RDONLY */
#include <stdint.h> /* uint8_t */
#include <stdio.h>  /* fprintf(), BUFSIZ */
#include <string.h> /* strerror(), strncmp() */
#include <unistd.h> /* read(), write(), close(), getopt(), opt* */
// 64(26+26+10+2)
static char b64_encmap[64] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static size_t c_out        = 0;
// TODO: -w option ; 76 is lowest of all base64 related RFCs
static size_t wrap_nl = 76;
static inline uint8_t
b64_get(uint8_t pos)
{
	assert(pos <= 64);
	return b64_encmap[pos];
}
static void
b64encode(uint8_t out[4], uint8_t in[3])
{
	out[0] = b64_get(in[0] >> 2);
	out[1] = b64_get((uint8_t)(((in[0] & 0x03) << 4) | (in[1] >> 4)));
	out[2] = b64_get((uint8_t)(((in[1] & 0x0f) << 2) | (in[2] >> 6)));
	out[3] = b64_get(in[2] & 0x3f);
}
static int
encode(int fd, const char *fdname)
{
	ssize_t c = 0;
	char ibuf[3];
	while((c = read(fd, ibuf, sizeof(ibuf))) > 0)
	{
		uint8_t obuf[4] = "----";
		ssize_t pad  = 0;
		assert(pad >= 0);
		for(; c < 3; pad++, c++)
		{
			ibuf[c] = 0;
		}
		assert(c == 3);
		b64encode(obuf, (uint8_t *)ibuf);
		for(; pad > 0; pad--)
		{
			obuf[4 - pad] = '=';
		}
		if(write(1, (char *)obuf, 4) != 4)
		{
			fprintf(stderr, "base64: Error writing: %s\n", strerror(errno));
			return 1;
		}
		c_out += 4;
		if(wrap_nl != 0 && c_out >= wrap_nl)
		{
			c_out = 0;
			if(write(1, "\n", 1) != 1)
			{
				fprintf(stderr, "base64: Error writing: %s\n", strerror(errno));
				return 1;
			}
		}
	}
	if(c < 0)
	{
		fprintf(stderr, "base64: Error reading ‘%s’: %s\n", fdname, strerror(errno));
		return 1;
	}
	return 0;
}
static int
decode(int fd, const char *fdname)
{
	return 1;
}
int
main(int argc, char *argv[])
{
	int (*process)(int, const char *) = &encode;
	int c = 0, ret = 0;
	while((c = getopt(argc, argv, ":d")) != -1)
	{
		switch(c)
		{
		case 'd':
			process = &decode;
			break;
		case ':':
			fprintf(stderr, "base64: Error: Missing operand for option: ‘-%c’\n", optopt);
			return 1;
		case '?':
			fprintf(stderr, "base64: Error: Unrecognised option: ‘-%c’\n", optopt);
			return 1;
		}
	}
	argc -= optind;
	argv += optind;
	if(argc <= 0)
	{
		ret = process(0, "<stdin>");
		goto end;
	}
	for(int argi = 0; argi < argc; argi++)
	{
		if(strncmp(argv[argi], "-", 2) == 0)
		{
			if(process(0, "<stdin>") != 0)
			{
				ret = 1;
				goto end;
			}
		}
		else if(strncmp(argv[argi], "--", 3) == 0)
		{
			continue;
		}
		else
		{
			int fd = open(argv[argi], O_RDONLY);
			if(fd < 0)
			{
				fprintf(stderr, "base64: Error opening ‘%s’: %s\n", argv[argi], strerror(errno));
				ret = 1;
				goto end;
			}
			if(process(fd, argv[argi]) != 0)
			{
				ret = 1;
				goto end;
			}
			if(close(fd) < 0)
			{
				fprintf(stderr, "base64: Error closing ‘%s’: %s\n", argv[argi], strerror(errno));
				ret = 1;
				goto end;
			}
		}
	}
end:
	if(c_out > 0)
	{
		printf("\n");
	}
	return ret;
}