/*
 * Print stdin fully reversed. Unlike util-linux rev(1), this program does not
 * reverse lines, but buffers everything fully and then writes it on the end.
 * Author: Peter Wu <lekensteyn@gmail.com>
 * Date: 2012-11-07
 */
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>

#define READ_BLOCK 1024
#define SIZE_INC (4 * READ_BLOCK)

int main(void) {
	unsigned len = 0; /* length of data */
	unsigned str_size = SIZE_INC; /* size of buffer */
	char *str = malloc(str_size);
	if (!str) {
		perror("malloc");
		return 1;
	}
	int n = 0;
	do {
		if (str_size - len < SIZE_INC) {
			str_size += SIZE_INC;
			str = realloc(str, str_size);
			if (!str) {
				fprintf(stderr, "Failed to enlarge buffer to %u: %s\n", str_size, strerror(errno));
				abort();
			}
		}
		n = read(STDIN_FILENO, str + len, READ_BLOCK);
		if (n < 0) {
			perror("read");
			goto free_str;
		} else if (n) {
			len += n;
		}
	} while (n);

	/* print in reverse */
	while (len)
		putchar(str[--len]);

	free(str);
	return 0;
free_str:
	free(str);
	return 1;
}