sample_181.md

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StrDup returns a pointer to the duplicate of a source VFP string

Code:

DO decl

LOCAL lcSource, lcTarget, hMemory
lcSource = "Jack and Jill went up a hill"
hMemory = StrDup(lcSource)
	
IF hMemory <> 0
	? "Pointer to a new string:", hMemory

	* copying from a pointer to a VFP string
	lcTarget = SPACE(250)
	= StrCpy (@lcTarget, hMemory)
	? "Transferred string:", LEFT(lcTarget, AT(Chr(0), lcTarget)-1)

	* MSDN: The calling application must free this memory
	* by calling the LocalFree function on the pointer
	* returned by the call to StrDup.
	= LocalFree (hMemory)
ELSE
* error
ENDIF

PROCEDURE  decl
	DECLARE INTEGER LocalFree IN kernel32 INTEGER hMem
	DECLARE INTEGER StrDup IN shlwapi STRING lpsz
	DECLARE INTEGER StrCpyW IN shlwapi AS StrCpy;
		STRING @psz1, INTEGER psz2  

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Listed functions:

LocalFree
StrCpy
StrDup

Comment:

For sure in many situations you can pass pointers to strings to external procedures just using STRING @.

But not when you need to fill a structure, which contains 4-byte pointers to strings. StrDup solves this problem easily, though you have an additional burden to free the allocated memory block.

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