Copies the first part of a block of memory from a location to another and clears the rest

declare sub fb_memcopyclear ( byref dst as any, byval dstlen as uinteger, byref src as any, byval srclen as uinteger )

fb_memcopy( dst, dstlen, src, srclen )

starting address of destination memory
number of bytes to write
starting address of source memory
number of first bytes to copy (other are cleared)

fb_memcopycopy copies a given number of bytes (dstlen) from the memory location src to the memory location dst, but only the first srclen bytes are really copied and the rest is cleared ((dstlen - srclen) bytes).
Each starting address is taken from a reference to a variable or array element.
The memory areas must not overlap (otherwise, the copying is not guaranteed to work properly, especially depending on the platform).
To avoid overflows, the valid memory areas pointed to by both src and dst must be at least equal in size to the number of bytes to be copied (including the bytes cleared).

The underlying type of the objects pointed to by both the source and destination pointers are irrelevant for this function.
The function does not check for any terminating null character in the source area. It always copies exactly the given number of bytes.
The result is a binary copy of the data for the first srclen bytes and a zeroing for the rest ((dstlen - srclen) bytes).

Note: In order to copy from/to memory referenced by a Pointer, it must be dereferenced first (or else specify in argument term the Byval keyword in front of the pointer name). Otherwise, fb_memcopyclear will try to copy the bytes from/to the pointer variable's memory location.

Dim src As ZString * 10 = "FreeBASIC"
Dim dst As ZString * 10 = "012345678"

Print "before:"
Print "src = " & src
Print "dst = " & dst

'' copy first 4 bytes and clear the rest
fb_memcopyclear(dst, SizeOf(dst), src, 4)

Print "after:"
Print "src = " & src
Print "dst = " & dst

src = FreeBASIC
dst = 012345678

src = FreeBASIC
dst = Free

Differences from QB:
See also:
Back to Memory Functions
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