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StringCchCopy function

Applies to: desktop apps | Metro style apps

Copies one string to another. The size of the destination buffer is provided to the function to ensure that it does not write past the end of this buffer.

StringCchCopy is a replacement for the following functions:

Syntax

Copy

HRESULT StringCchCopy(
  __out  LPTSTR pszDest,
  __in   size_t cchDest,
  __in   LPCTSTR pszSrc
);

Parameters

pszDest [out]

Type: LPTSTR

The destination buffer, which receives the copied string.

cchDest [in]

Type: size_t

The size of the destination buffer, in characters. This value must equal the length of pszSrc plus 1 to account for the copied source string and the terminating null character. The maximum number of characters allowed is STRSAFE_MAX_CCH.

pszSrc [in]

Type: LPCTSTR

The source string. This string must be null-terminated.

Return value

Type: HRESULT

This function can return one of the following values. It is strongly recommended that you use the SUCCEEDED and FAILED macros to test the return value of this function.

Return code	Description
S_OK	Source data was present, fully copied without truncation, and the resultant destination buffer is null-terminated.
STRSAFE_E_INVALID_PARAMETER	The value in cchDest is either 0 or larger than STRSAFE_MAX_CCH.
STRSAFE_E_INSUFFICIENT_BUFFER	The copy operation failed due to insufficient buffer space. The destination buffer contains a truncated, null-terminated version of the intended result. In situations where truncation is acceptable, this may not necessarily be seen as a failure condition.

Note that this function returns an HRESULT value, unlike the functions that it replaces.

Remarks

Compared to the functions it replaces, StringCchCopy provides additional processing for proper buffer handling in your code. Poor buffer handling is implicated in many security issues that involve buffer overruns. StringCchCopy always null-terminates a nonzero-length destination buffer.

Behavior is undefined if the strings pointed to by pszSrc and pszDest overlap.

Neither pszSrc nor pszDest should be NULL. See StringCchCopyEx if you require the handling of null string pointer values.

StringCchCopy can be used in its generic form, or in its more specific forms. The data type of the string determines the form of this function that you should use.

String Data Type	String Literal	Function
char	"string"	StringCchCopyA
TCHAR	TEXT("string")	StringCchCopy
WCHAR	L"string"	StringCchCopyW

Requirements

Minimum supported client	Windows XP with SP2
Minimum supported server	Windows Server 2003 with SP1
Header	Strsafe.h
Unicode and ANSI names	StringCchCopyW (Unicode) and StringCchCopyA (ANSI)

It seems to me that the description of cchDest is wrong. Surely it should say "This value must be at least equal the length of pszSrc plus 1 ...". Otherwise you cannot copy a string to a buffer unless the buffer happens to have precisely the same size as the string (because cchDest must also be the size of pszDest).
If the function had that limitation, then it would be practically useless, since it then can be replaced with just a memcpy of sizeof(wchar_t)*cchDest bytes.

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