StringCbGetsExA function (strsafe.h)

Article
02/09/2023

Gets one line of text from stdin, up to and including the newline character ('\n'). The line of text is copied to the destination buffer, and the newline character is replaced with a null character. The size of the destination buffer is provided to the function to ensure that it does not write past the end of this buffer.

Note This function can only be used inline.

StringCbGetsEx adds to the functionality of StringCbGets 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.

StringCbGetsEx is a replacement for the following functions:

gets, _getws, _getts

StringCbGetsEx is not a replacement for fgets, which does not replace newline characters with a terminating null character.

Syntax

STRSAFEAPI StringCbGetsExA(
  [out]           STRSAFE_LPSTR pszDest,
  [in]            size_t        cbDest,
  [out, optional] STRSAFE_LPSTR *ppszDestEnd,
  [out, optional] size_t        *pcbRemaining,
  [in]            DWORD         dwFlags
);

Parameters

[out] pszDest

Type: LPTSTR

The destination buffer, which is to receive the input.

[in] cbDest

Type: size_t

The size of the destination buffer, in bytes. This value must be greater than sizeof(TCHAR) for the function to succeed. The maximum number of bytes allowed is STRSAFE_MAX_CCH * sizeof(TCHAR). If cbDest is too small to hold the full line of text, the data is truncated.

[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
STRSAFE_FILL_BEHIND_NULL 0x00000200	If the function succeeds, the low byte of dwFlags (0) is used to fill the uninitialized portion of pszDest following the terminating null character.
STRSAFE_IGNORE_NULLS 0x00000100	Treat NULL string pointers like empty strings (TEXT("")). This flag is useful for emulating functions such as lstrcpy.
STRSAFE_FILL_ON_FAILURE 0x00000400	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.
STRSAFE_NULL_ON_FAILURE 0x00000800	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.
STRSAFE_NO_TRUNCATION 0x00001000	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
S_OK	Data was read from stdin, was copied to the buffer at pszDest, and the buffer was null-terminated.
STRSAFE_E_END_OF_FILE	Indicates an error or end-of-file condition. Use feof or ferror to determine which one has occurred.
STRSAFE_E_INVALID_PARAMETER	The value in cbDest is larger than the maximum allowed value or an invalid flag was passed.
STRSAFE_E_INSUFFICIENT_BUFFER	The value in cbDest is 1 or less.

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

Remarks

StringCbGetsEx provides additional processing for proper buffer handling in your code. Poor buffer handling is implicated in many security issues that involve buffer overruns. StringCbGetsEx always null-terminates a nonzero-length destination buffer.

The value of pszDest should not be NULL unless the STRSAFE_IGNORE_NULLS flag is specified. However, an error due to insufficient space may still be returned even though NULL values are ignored.

StringCbGetsEx 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, as shown in the following table.

String Data Type	String Literal	Function
char	"string"	StringCbGetsExA
TCHAR	TEXT("string")	StringCbGetsEx
WCHAR	L"string"	StringCbGetsExW

Note

The strsafe.h header defines StringCbGetsEx 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