I need to compare some of the values in an array to see if they are all the same single value, let's say 0xFF. Is there a common function to do this, like memcmp(), or do I have to do it the hard way and check every explicit value, like:
if ( ary[3] == 0xFF && ary[4] == 0xFF && ary[5] == 0xFF && ary[6] == 0xFF ... )
{
// do something
}
I can obviously make my own function to do it like memcmp, but I don't want to reinvent the wheel if I don't have to.
I suppose a completely generic function would look something like this:
#include <string.h>
bool check_array (const void* array,
size_t array_n
const void* value,
size_t type_size)
{
const uint8_t* begin = array;
const uint8_t* end = begin + array_n * type_size;
const uint8_t* byte_val = value;
const uint8_t* byte_ptr;
for(byte_ptr = begin; byte_ptr < end; byte_ptr += type_size)
{
if( memcmp(byte_ptr,
byte_val,
type_size) != 0 )
{
return false;
}
}
return true;
}
int main()
{
int array [] = { ... };
bool result = check_array (array,
sizeof(array),
0x12345678,
sizeof(int));
}
From your answer I see you need to compare bytes, in that case string.h supports memchr, strchr and their derivatives, depending on how exactly you want to use it.
If you wanted to implement it yourself, and performance is an issue, i'd suggest inlining a block of assembly doing rep scasb
