StringCbCopyA function (strsafe.h)

Article
02/09/2023

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.

StringCbCopy is a replacement for the following functions:

Syntax

STRSAFEAPI StringCbCopyA(
  [out] STRSAFE_LPSTR  pszDest,
  [in]  size_t         cbDest,
  [in]  STRSAFE_LPCSTR pszSrc
);

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

A pointer to a buffer containing the source string. This source 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 cbDest is either less than `sizeof(TCHAR)` or larger than the maximum allowed value.
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, StringCbCopy provides additional processing for proper buffer handling in your code. Poor buffer handling is implicated in many security issues that involve buffer overruns. StringCbCopy 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. See StringCbCopyEx if you require the handling of null string pointer values.

StringCbCopy 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"	StringCbCopyA
TCHAR	TEXT("string")	StringCbCopy
WCHAR	L"string"	StringCbCopyW

Note

The strsafe.h header defines StringCbCopy as an alias which 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 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