C cleanups example

cleanups.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>

#define BUFFER_SIZE 4096

int copy(const char *src_path, const char *dst_path)
{
	int src, dst;
	char *buffer;
	int n;

	buffer = malloc(BUFFER_SIZE);
	if (!buffer)
		return 1;

	src = open(src_path, O_RDONLY);
	if (src < 0) {
		free(buffer);
		return 2;
	}

	dst = open(dst_path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
	if (dst < 0) {
		close(src);
		free(buffer);
		return 3;
	}

	while ((n = read(src, buffer, BUFFER_SIZE)) > 0) {
		if (write(dst, buffer, n) != n) {
			close(dst);
			close(src);
			free(buffer);
			return 4;
		}
	}

	if (n < 0) {
		close(dst);
		close(src);
		free(buffer);
		return 5;
	}

	close(dst);
	close(src);
	free(buffer);

	return 0;
}

int copy_goto(const char *src_path, const char *dst_path)
{
	int src, dst;
	char *buffer;
	int ret = 0, n;

	buffer = malloc(BUFFER_SIZE);
	if (!buffer) {
		ret = 1;
		goto out;
	}

	src = open(src_path, O_RDONLY);
	if (src < 0) {
		ret = 2;
		goto out_free;
	}

	dst = open(dst_path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
	if (dst < 0) {
		ret = 3;
		goto out_src;
	}

	while ((n = read(src, buffer, BUFFER_SIZE)) > 0) {
		if (write(dst, buffer, n) != n) {
			ret = 4;
			goto out_dst;
		}
	}

	if (n < 0) {
		ret = 5;
		goto out_dst;
	}

out_dst:
	close(dst);
out_src:
	close(src);
out_free:
	free(buffer);
out:
	return ret;
}

#define _cleanup_(x) __attribute__((__cleanup__(x)))
#define _cleanup_close_ _cleanup_(closep)
#define _cleanup_free_ _cleanup_(freep)

static inline void closep(int *fd)
{
	if (*fd >= 0)
		close(*fd);
}

static inline void freep(void *p)
{
	free(*(void **)p);
}

int copy_cleanups(const char *src_path, const char *dst_path)
{
	_cleanup_close_ int src = -EBADF, dst = -EBADF;
	_cleanup_free_ char *buffer = NULL;
	int n;

	buffer = malloc(BUFFER_SIZE);
	if (!buffer)
		return 1;

	src = open(src_path, O_RDONLY);
	if (src < 0)
		return 2;

	dst = open(dst_path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
	if (dst < 0)
		return 3;

	while ((n = read(src, buffer, BUFFER_SIZE)) > 0) {
		if (write(dst, buffer, n) != n)
			return 4;
	}

	if (n < 0)
		return 5;

	return 0;
}

int main(int argc, char *argv[])
{
	if (argc != 3) {
		fprintf(stderr, "Usage: %s <source> <destination>\n", argv[0]);
		return 1;
	}

	copy(argv[1], argv[2]);
	copy_goto(argv[1], argv[2]);
	copy_cleanups(argv[1], argv[2]);

	return 0;
}