C言語でfread検証

ちょっと仕事で調べる必要があって、freadの検証。

ソースコード

/*
	main.cpp
*/

#include <stdio.h>
#include <time.h>
#include <windows.h>
#include <mmsystem.h>
#pragma comment(lib, "Winmm.lib")

#define BUF_SIZE	1024

static LARGE_INTEGER nFreq, nBefore, nAfter;
static LONGLONG DiffTime();

static int test1(FILE *fp, const char *fileName, char *buf);
static int test2(FILE *fp, const char *fileName, char *buf);

int main(int argc, char *argv[]) 
{
	FILE *fp = NULL;
	char buf[BUF_SIZE];
	const char *fileName = "D:\\test.dat";

	QueryPerformanceFrequency(&nFreq);

	test1(fp, fileName, buf);
	test1(fp, fileName, buf);

	test2(fp, fileName, buf);
	test2(fp, fileName, buf);

	return 0;
}

LONGLONG DiffTime()
{
	return (nAfter.QuadPart - nBefore.QuadPart) * 1000 / nFreq.QuadPart;
}

int test1(FILE *fp, const char *fileName, char *buf)
{
	int err = 0;
	int readLength = 0;
	int readTotal = 0;	

	printf("--- 実験１ ---\n");

	fp = fopen(fileName, "rb");
	if (fp == NULL) {
		printf("open error. filename=%s\n", fileName);
		return -1;
	}

	QueryPerformanceCounter(&nBefore);
	while(1) {
		readLength = fread(buf, sizeof(char), BUF_SIZE, fp);
		readTotal += readLength;
		if (readLength != 1024) {
			err = ferror(fp);
			printf("fread length unmatch. ferror=%d, readLength=%d\n", err, readLength);
			break;
		}
	}
	QueryPerformanceCounter(&nAfter);
	printf("readTotal=%d, time=%dms\n", readTotal, DiffTime());

	fclose(fp);

	return 0;
}

int test2(FILE *fp, const char *fileName, char *buf)
{
	int err = 0;
	int readLength = 0;
	int readTotal = 0;	

	printf("--- 実験２ ---\n");

	fp = fopen(fileName, "rb");
	if (fp == NULL) {
		printf("open error. filename=%s\n", fileName);
		return -1;
	}

	QueryPerformanceCounter(&nBefore);
	while(1) {
		readLength = fread(buf, BUF_SIZE, 1, fp) * BUF_SIZE;
		readTotal += readLength;
		if (readLength != 1024) {
			err = ferror(fp);
			if (err != 0) {
				printf("fread error. ferror=%d, readLength=%d\n", err, readLength);
				break;
			} else {
				printf("eof. ferror=%d, readLength=%d\n", err, readLength);
				break;
			}
		}
	}
	QueryPerformanceCounter(&nAfter);
	printf("readTotal=%d, time=%dms\n", readTotal, DiffTime());

	fclose(fp);

	return 0;
}

結果

--- 実験１ ---
fread length unmatch. ferror=0, readLength=344
readTotal=336724312, time=4591ms
--- 実験１ ---
fread length unmatch. ferror=0, readLength=344
readTotal=336724312, time=3490ms
--- 実験２ ---
eof. ferror=0, readLength=0
readTotal=336723968, time=3024ms
--- 実験２ ---
eof. ferror=0, readLength=0
readTotal=336723968, time=3349ms