Reverse Bits

reverse_bits.c

/*******************************************************************************
 * SPDX-License-Identifier: CC0-1.0
 * SPDX-FileType: SOURCE
 * SPDX-FileCopyrightText: (c) 2022, Public Domain
 ******************************************************************************/

#include <cstdint>
#include <cstdio>
#include <cstdlib>

int main(int argc, char *argv[]) {
	uint8_t *buf;
	FILE *fp;
	if(argc != 3) {
		printf("\nWrong parameters given\nUsage: reverse_bits [file_in] [file_out]\n");
		return -1;
	}
	fp = fopen(argv[1], "rb");
	if(fp == NULL) {
		printf("Couldn't open the file %s for input\n", argv[1]);
		return -1;
	}
	fseek(fp, 0L, SEEK_END);
	long size = ftell(fp);
	fseek(fp, 0L, SEEK_SET);

	buf = (uint8_t *) malloc(size);
	if(buf == NULL) {
		printf("Couldn't malloc file\n");
		return -1;
	}

	uint8_t in;
	for(int i = 0; i < size; i++) {
		fread(&in, 1, 1, fp);
		in = ((in & 1) << 7) | ((in & 2) << 5) | ((in & 4) << 3) | ((in & 8) << 1) | ((in & 16) >> 1) | ((in & 32) >> 3) | ((in & 64) >> 5) | ((in & 128) >> 7);

		buf[i] = in;
	}
	fclose(fp);

	printf("Reversed %ld bytes\n", size);
	fp = fopen(argv[2], "wb");
	if(fp == NULL) {
		printf("Couldn't open the file %s for output\n", argv[2]);
		return -1;
	}
	fwrite(buf, 1, size, fp);
	fclose(fp);

	free(buf);
	printf("Done\n");

	return 0;
}