Intel Extensible Firmware Interface - Manual (Page 187)

Services — Boot Services
Version 1.10 12/01/02 5-89
CopyMem()
Summary
The CopyMem() function copies the contents of one buffer to another buffer.
Prototype
VOID
CopyMem (
IN VOID *Destination,
IN VOID *Source,
IN UINTN Length
);
Parameters
Destination Pointer to the destination buffer of the memory copy.
Source Pointer to the source buffer of the memory copy.
Length Number of bytes to copy from Source to Destination .
Description
The CopyMem() function copies Length bytes from the buffer Source to the buffer
Destination .
The implementation of CopyMem() must be reentrant, and it must handle overlapping Source
and Destination buffers. This means that the implementation of CopyMem() must choose the
correct direction of the copy operation based on the type of overlap that exists between the
Source and Destination buffers. If either the Source buffer or the Destination buffer
crosses the top of the processor’s address space, then the result of the copy operation is
unpredictable.
The contents of the Destination buffer on exit from this service must match the contents of the
Source buffer on entry to this service. Due to potential overlaps, the contents of the Source
buffer may be modified by this service. The following rules can be used to guarantee the correct
behavior:
1. If Destination and Source are identical, then no operation should be performed.
2. If Destination > Source and Destination < ( Source + Length ), then the data
should be copied from the Source buffer to the Destination buffer starting from the end
of the buffers and working toward the beginning of the buffers.
3. Otherwise, the data should be copied from the Source buffer to the Destination buffer
starting from the beginning of the buffers and working toward the end of the buffers.
Status Codes Returned
None.