fread（）返回不正确的数据

Question

I am trying to read 128KB binary file in chunks of 256 Bytes. The first 20-40 bytes of 256 bytes seems to be always correct. However after that the data gets corrupted. I tried reading the file and writing it into another binary file and compared. More than half of the data is corrupted. Here is my code

uint8_t buffer[256]
read_bin_file = fopen("vtest.bin", "r");
if (read_bin_file == NULL)
{
    printf("Unable to open file\n");
    return false;
}

test_bin = fopen("test_file.bin", "w");
if (test_file == NULL)
{
    printf("Unable to open file\n");
    return false;
}

fflush(stdout);

for (i = 0; i <=0x1FF; i++)
{
    file_Read_pointer = i * 256;
    fseek(read_bin_file, file_Read_pointer, SEEK_SET);
    fread(buffer, 256, 1, read_bin_file);
    fseek(test_file, file_Read_pointer, SEEK_SET);
    fwrite(buffer, 256, 1, test_file);

}

What is that I am missing? Also when i try to increase the bytes read from 256 to 1024 ( i<0x7F) the error seems to decrease significantly. The file is almost 90% matching

Answer 1

If it is binary data you're reading and writing, then you should open the files in binary mode with read_bin_file = fopen("vtest.bin", "rb"); . Note the "b" in the mode. This prevents special handling of new line characters.

Your fseek s are also unnecessary, the fread and fwrite calls will handle that for you. From here "The file position indicator for the stream is advanced by the number of characters read."