StringCbCopyExA function (strsafe.h)
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.
StringCbCopyEx adds to the functionality of StringCbCopy by returning a pointer to the end of the destination string as well as the number of bytes left unused in that string. Flags may also be passed to the function for additional control.
StringCbCopyEx is a replacement for the following functions:
Syntax
STRSAFEAPI StringCbCopyExA(
[out] STRSAFE_LPSTR pszDest,
[in] size_t cbDest,
[in] STRSAFE_LPCSTR pszSrc,
[out, optional] STRSAFE_LPSTR *ppszDestEnd,
[out, optional] size_t *pcbRemaining,
[in] DWORD dwFlags
);
Parameters
[out] pszDest
Type: LPTSTR
The destination buffer, which receives the copied string.
[in] cbDest
Type: size_t
The size of the destination buffer, in bytes. This value must consider the length of pszSrc plus the terminating null character. The maximum number of bytes allowed is STRSAFE_MAX_CCH * sizeof(TCHAR).
[in] pszSrc
Type: LPCTSTR
The source string. This string must be null-terminated.
[out, optional] ppszDestEnd
Type: LPTSTR*
The address of a pointer to the end of pszDest. If ppszDestEnd is non-NULL and any data is copied into the destination buffer, this points to the terminating null character at the end of the string.
[out, optional] pcbRemaining
Type: size_t*
The number of unused bytes in pszDest, including those used for the terminating null character. If pcbRemaining is NULL, the count is not kept or returned.
[in] dwFlags
Type: DWORD
One or more of the following values.
| Value | Meaning |
|---|---|
|
If the function succeeds, the low byte of dwFlags (0) is used to fill the uninitialized portion of pszDest following the terminating null character. |
|
Treat NULL string pointers like empty strings (TEXT("")). This flag is useful for emulating functions such as lstrcpy. |
|
If the function fails, the low byte of dwFlags (0) is used to fill the entire pszDest buffer, and the buffer is null-terminated. In the case of a STRSAFE_E_INSUFFICIENT_BUFFER failure, any truncated string returned is overwritten. |
|
If the function fails, pszDest is set to an empty string (TEXT("")). In the case of a STRSAFE_E_INSUFFICIENT_BUFFER failure, any truncated string is overwritten. |
|
As in the case of STRSAFE_NULL_ON_FAILURE, if the function fails, pszDest is set to an empty string (TEXT("")). In the case of a STRSAFE_E_INSUFFICIENT_BUFFER failure, any truncated string is overwritten. |
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 |
|---|---|
|
Source data was present, fully copied without truncation, and the resultant destination buffer is null-terminated. |
|
Either pszDest is NULL when there is source data present to copy, or an invalid flag was passed. |
|
The copy operation failed due to insufficient buffer space. Depending on the value of dwFlags, the destination buffer may contain 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, StringCbCopyEx provides additional processing for proper buffer handling in your code. Poor buffer handling is implicated in many security issues that involve buffer overruns. StringCbCopyEx always null-terminates and never overflows a valid destination buffer, even if the contents of the source string change during the operation.
Behavior is undefined if the strings pointed to by pszSrc and pszDest overlap.
Neither pszSrc nor pszDest should be NULL unless the STRSAFE_IGNORE_NULLS flag is specified, in which case both may be NULL. However, an error due to insufficient space may still be returned even though NULL values are ignored.
StringCbCopyEx 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" | StringCbCopyExA |
| TCHAR | TEXT("string") | StringCbCopyEx |
| WCHAR | L"string" | StringCbCopyExW |
Note
The strsafe.h header defines StringCbCopyEx as an alias that automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that is not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows XP with SP2 [desktop apps | UWP apps] |
| Minimum supported server | Windows Server 2003 with SP1 [desktop apps | UWP apps] |
| Target Platform | Windows |
| Header | strsafe.h |
See also
Reference