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Inside Macintosh: Memory /

Chapter 2 - Memory Manager / Memory Manager Reference

Memory Manager Routines / Manipulating Blocks of Memory

BlockMove

To copy a sequence of bytes from one location in memory to another, you can use the BlockMove procedure.

PROCEDURE BlockMove (sourcePtr, destPtr: Ptr; byteCount: Size);

sourcePtr

The address of the first byte to copy.

destPtr

The address of the first byte to copy to.

byteCount

The number of bytes to copy. If the value of byteCount is 0, BlockMove does nothing.

DESCRIPTION

The BlockMove procedure moves a block of byteCount consecutive bytes from
the address designated by sourcePtr to that designated by destPtr. It updates
no pointers.

The BlockMove procedure works correctly even if the source and destination
blocks overlap.

SPECIAL CONSIDERATIONS

You can safely call BlockMove at interrupt time. Even though it moves memory, BlockMove does not move relocatable blocks, but simply copies bytes.

The BlockMove procedure currently flushes the processor caches whenever the number of bytes to be moved is greater than 12. This behavior can adversely affect your application's performance. You might want to avoid calling BlockMove to move small amounts of data in memory if there is no possibility of moving stale data or instructions. For more information about stale data and instructions, see the discussion of the processor caches in the chapter "Memory Management Utilities" in this book.

ASSEMBLY-LANGUAGE INFORMATION

The registers on entry and exit for BlockMove are

Registers on entry
A0	Pointer to source
A1	Pointer to destination
D0	Number of bytes to copy

Registers on exit
D0	Result code

RESULT CODE

noErr

0

No error