バイナリエディタスプリット

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/stat.h>

static unsigned long get_file_size(FILE* fp);

int main(int argc, const char* argv[])
{
	// check for input parameters
	if (argc < 3) { printf("lack of input paremeters\n"); return -1; }

	// arguments
	const char* in_path = argv[1]; // source file
	char* dmy;
	const unsigned long split_bytes = strtoul(argv[2], &dmy, 10);	// split bytes

	// allocate data buffer 
	unsigned char* buffer = (unsigned char*)malloc(split_bytes);
	if (buffer == NULL) { printf("cannot allocate buffer (bytes = %d)\n", split_bytes); return -1; }

	// open input file
	errno_t error;
	FILE* in_fp;
	error = fopen_s(&in_fp, in_path, "rb");
	if (error != 0) { printf("cannot input file : %s\n", in_path); return -1; }
	// get input file size
	unsigned long in_path_bytes = get_file_size(in_fp);

	// set start position in file pointer
	fseek(in_fp, 0, SEEK_SET);

	// initialize auto variable 		
	size_t remain_bytes = in_path_bytes;
	int split_count = 0;

	do
	{
		// calcurate split binary file size
		size_t next_read_bytes = (remain_bytes > split_bytes) ? split_bytes : remain_bytes;

		// read data from input file
		size_t read_bytes = fread_s(buffer, split_bytes, 1, next_read_bytes, in_fp);
		if (read_bytes != next_read_bytes) { printf("fail to read bytes from input file\n"); return -1;}

		// create new binary file
		char str_out_path[_MAX_FNAME];
		sprintf_s(str_out_path, sizeof(str_out_path), "%s-%03d", in_path, ++split_count);
		FILE* out_fp;
		error = fopen_s(&out_fp, str_out_path, "wb");
		if (out_fp == NULL) { printf("cannot open binary file : %s", str_out_path); return -1; }

		// write data into new binary file
		size_t wrote_bytes = fwrite(buffer, 1, next_read_bytes, out_fp);
		if (read_bytes != next_read_bytes) { printf("fail to write bytes from input file\n"); return -1; }

		// flush and close 
		(void)fflush(out_fp);
		(void)fclose(out_fp);

		remain_bytes -= next_read_bytes;
	} while (remain_bytes > 0);
	
	// close input file
	(void)fclose(in_fp);

	return 0;
}

static unsigned long get_file_size(FILE *fp)
{
	fpos_t pos = 0;
	if((fseek(fp, 0, SEEK_END) == 0) && (fgetpos(fp, &pos) == 0))
	{
		return (unsigned long)pos;
	}
	else
	{
		return 0;
	}
}