StringCbGetsEx (Windows CE 5.0)
Developing an Application > Safe String Functions > Safe String Reference > StrSafe.h Byte-Count Functions
This function is a replacement for gets.
The size, in bytes, of the destination buffer is provided to the function to ensure that StringCbGetsEx does not write past the end of this buffer.
It retrieves one line of text from stdin, a newline ('\n') ending the input. The line of text is copied to the destination buffer and the carriage return is replaced with a null character.
StringCbGetsEx adds to the functionality of StringCbGets by returning a pointer to the end of the destination string, and by returning the number of bytes left unused in that string.
Flags can also be passed to the function for additional control.
**Note **This function can only be used inline.
HRESULT StringCbGetsEx( LPTSTR pszDest,
size_t cbDest,
LPTSTR *ppszDestEnd,
size_t *pcbRemaining,
DWORD dwFlags);
Parameters
pszDest
[out] Pointer to a buffer that receives the input.cbDest
[in] Size of the destination buffer, in bytes.For the function to succeed, this value must be greater than sizeof(TCHAR).
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.
ppszDestEnd
[out] Address of a pointer to the end of pszDest.If ppszDestEnd is non-NULL and data is copied into the destination buffer, this points to the terminating null character at the end of the string.
pcbRemaining
[out] Pointer to a variable that indicates 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.
dwFlags
[in] One or more of the following values.Value Description STRSAFE_FILL_BEHIND_NULL 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 Treat null string pointers like empty strings (TEXT("")). This flag is useful for emulating functions such as lstrcpy.
STRSAFE_FILL_ON_FAILURE 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 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 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
This function returns an HRESULT, as opposed to gets, which returns a pointer.
It is strongly recommended that you use the SUCCEEDED and FAILED macros to test the return value of this function.
| Value | 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.
To determine which condition has occurred, use feof or ferror. |
| 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. |
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.
StringCbGetsEx can be used in its generic form, or specifically as StringCbGetsExA (for ANSI strings) or StringCbGetsExW (for Unicode strings). The form to use is determined by your data.
| String data type | String literal | Function |
|---|---|---|
| char | "string" | StringCbGetsExA |
| TCHAR | TEXT("string") | StringCbGetsEx |
| WCHAR | L"string" | StringCbGetsExW |
StringCbGetsEx and its ANSI and Unicode variants are replacements for these functions:
StringCbGetsEx is not a replacement for fgets. That function does not replace newline characters with a null terminator.
The value of pszDest should not be NULL unless the STRSAFE_IGNORE_NULLS flag is specified. However, an error due to insufficient space might still be returned even though null values are ignored.
Requirements
OS Versions: Windows CE 5.0 and later.
Header: strsafe.h.
Link Library: none.
See Also
StringCchGetsEx | StringCbGets
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