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Revision as of 15:13, 13 May 2007

Contents 1 Definition 2 Parameters 3 Returns 4 Example

Definition

INT memcmp ( <VOID POINTER ptr1> , <VOID POINTER ptr2> , <INT number> )

Compares the first number bytes of the block of memory pointed by ptr1 to the first number bytes pointed by ptr2, returning zero if they all match or a value different from zero representing which is greater if they do not.

Parameters

VOID POINTER ptr1	- Pointer to a block of memory
VOID POINTER ptr2	- Pointer to a block of memory.
INT number	- The number of bytes to be checked.

Returns

INT : Difference

0	- The blocks of memory are identical.
>0	- The first differing byte in both memory blocks has a greater value in ptr1.
<0	- The first differing byte in both memory blocks has a greater value in ptr2.

A byte ranges from 0 to 255, meaning 189 is a greater value than 105.

Example

Program example;
Const
    elements = 10;
End
Private
    byte pointer pbyte1;
    byte pointer pbyte2;
    int result;
End
Begin

    // Allocate memory
    pbyte1 = alloc(elements);
    pbyte2 = alloc(elements);

    // Make the blocks the same and compare
    memset(pbyte1,3,elements);
    memset(pbyte2,3,elements);
    result = memcmp(pbyte1,pbyte2,elements); // You can also compare the first 5 bytes, or the first elements/2 bytes,
                                             // it depends on what you want.
    say("Memcmp 1: " + result);

    // Make the first block have a greater value and compare
    pbyte1[0] = 4;
    result = memcmp(pbyte1,pbyte2,elements);
    say("Memcmp 2: " + result);

    // Make the blocks the same and compare
    pbyte2[0] = 4;
    result = memcmp(pbyte1,pbyte2,elements);
    say("Memcmp 3: " + result);

    // Make the first block have a greater value and compare
    pbyte2[1] = 5;
    result = memcmp(pbyte1,pbyte2,elements);
    say("Memcmp 4: " + result);

    Repeat
        frame;
    Until(key(_esc))

    // Free the used memory
    free(pbyte1);
    free(pbyte2);

End

Used in example: alloc(), memset(), say(), free(), pointer