Concatenates the specified number of characters from one string to another string. The size of the destination buffer is provided to the function to ensure that it does not write past the end of this buffer.
StringCchCatNEx adds to the functionality of StringCchCatN by returning a pointer to the end of the destination string as well as the number of characters left unused in that string. Flags may also be passed to the function for additional control.
StringCchCatNEx is a replacement for the following functions:
STRSAFEAPI StringCchCatNExW( STRSAFE_LPWSTR pszDest, size_t cchDest, STRSAFE_PCNZWCH pszSrc, size_t cchToAppend, STRSAFE_LPWSTR *ppszDestEnd, size_t *pcchRemaining, DWORD dwFlags );
The destination buffer, which contains the string that is to be concatenated with pszSrc, and will receive the entire resultant string. The string at pszSrc is added to the end of the string at pszDest.
The size of the destination buffer, in characters. This value must equal the length of pszSrc plus the length of pszDest plus 1 to account for the terminating null character. The maximum number of characters allowed is STRSAFE_MAX_CCH.
The source string that is concatenated to the end of pszDest. This string must be null-terminated.
The maximum number of characters to be appended to pszDest.
The address of a pointer to the end of pszDest. If ppszDestEnd is non-NULL and any data is appended to the destination buffer, this points to the terminating null character at the end of the string.
The number of unused characters in pszDest, including the terminating null character. If pcchRemaining is NULL, the count is not kept or returned.
One or more of the following values.
||Source data was present, the strings were concatenated without truncation, and the resultant destination buffer is null-terminated.|
||The value in cchDest is larger than STRSAFE_MAX_CCH, an invalid flag was passed, or there are discrepancies between the size of the pszDest, cchDest, and the amount of material to append in pszSrc.|
||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.
Compared to the functions it replaces, StringCchCatNEx provides additional processing for proper buffer handling in your code. Poor buffer handling is implicated in many security issues that involve buffer overruns. StringCchCatNExalways 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.
StringCchCatNEx 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|
|Minimum supported client||Windows XP with SP2 [desktop apps | UWP apps]|
|Minimum supported server||Windows Server 2003 with SP1 [desktop apps | UWP apps]|