Hi all,
I'm having a problem writing/reading some unsigned long data in a binary file.
I write 4 values of size 4 bytes; so I'am expecting the file size to be 16 bytes. But when I read the file back; it reports 64 bytes.
I just can't figure out why there is a difference; hope someone else can spot my mistake.
Here is the code I'm using:
#include <sys/stat.h>
#include <malloc.h>
#include <string.h>
#include <process.h>
int _tmain(int argc, _TCHAR* argv[]) {
const unsigned int TOTAL_NUMS = 4;
const unsigned long NUMBERS [] = { 1L, 5L, 7L, 2L };
const char * PATHNAME = "C:\\test.bin";
printf("sizeof(unsigned long) = %d\n", sizeof(unsigned long));
printf("Expected file size = %d\n", (TOTAL_NUMS * sizeof(unsigned long)));
printf("Expected count = %d\n", TOTAL_NUMS);
FILE * fFile = fopen(PATHNAME, "wb");
if (fFile == NULL) {
return 1;
}
for (int i = 0; i < TOTAL_NUMS; i++) {
fwrite(NUMBERS, sizeof(unsigned long), TOTAL_NUMS, fFile);
}
fclose(fFile);
struct stat s;
memset(&s, 0, sizeof(s));
stat(PATHNAME, &s);
const unsigned long fSize = s.st_size;
printf("\nActual file size = %lu\n", fSize);
if (fSize <= 0L) {
return 1;
}
unsigned long * nums = (unsigned long *) malloc( fSize );
if (nums == NULL) {
return 1;
}
memset(nums, 0, fSize);
fFile = fopen(PATHNAME, "rb");
if (fFile == NULL) {
return 1;
}
const unsigned int count = (fSize / sizeof(unsigned long));
const unsigned int actualCount = fread(nums, sizeof(unsigned long), count, fFile);
printf("Calculated count = %u\n", count);
printf("Actual count = %u\n\n", actualCount);
fclose(fFile);
printf("Contents:\n");
for (int i = 0; i < actualCount; i++) {
printf("%d = %lu\n", i, nums);
}
printf("\n");
free(nums);
system("pause");
return 0;
}
And this is the output I get:
sizeof(unsigned long) = 4
Expected file size = 16
Expected count = 4
Actual file size = 64
Calculated count = 16
Actual count = 16
Contents:
0 = 1
1 = 5
2 = 7
3 = 2
4 = 1
5 = 5
6 = 7
7 = 2
8 = 1
9 = 5
10 = 7
11 = 2
12 = 1
13 = 5
14 = 7
15 = 2
Press any key to continue . . .
[EDIT]
Thanks. I was using source tags but I think the comments were screwing it up. After removing them it posted okay.
[Edited by - Angex on December 14, 2008 9:18:23 AM]
