Hi there,
I got a question considering the usage of I/O drivers functions fwrite() and fread(). Specifically in the context of the i2c device. I considered the file "eeprom_int.h" in the mqx 3.6.2 example project i2c_mcf52277evb.mcp.
Why are fwrite and fread calls implemented in a while loop?
Examples are:
/* Write address within memory block */
mem = addr & 0xFF;
printf (" Write to address 0x%02x ... ", mem);
do
{
result = fwrite (&mem, 1, 1, fd);
} while (result < 1);
if (1 == result)
{
printf ("OK\n");
} else {
printf ("ERROR\n");
}
/* Page write of data */
printf (" Page write %d bytes ... ", length);
result = 0;
do
{
result += fwrite (buffer + result, 1, length - result, fd);
} while (result < length);
if (result == length)
{
printf ("OK\n");
} else {
printf ("ERROR\n");
}
/* Read all data */
printf (" Read %d bytes ... ", n);
result = 0;
do
{
result += fread (buffer + result, 1, n - result, fd);
} while (result < n);
if (result == n)
{
printf ("OK\n");
} else {
printf ("ERROR\n");
}
Is there any chance fwrite and fread functions return a non-negative value different from the specified amount of bytes to write/read? And in this case, there will be multiple fread/fwrite calls in a while clause?
Supposing there are multiple calls, isn't the starting address for the write/read operations becoming a problem? Or is this address adjusted automatically?
In the general c++ function description of fwrite it says that a return value different from the specified amount indicates an error. For fread, it might also be that the end of file was reached. Therefore i do not see the purpose of the while loops in the example.
Would be great if somebody could clarify this for me!
Best,
Florian
