TlsSetValue

The TlsSetValue function stores a value in the calling thread's thread local storage (TLS) slot for the specified TLS index. Each thread of a process has its own slot for each TLS index.

BOOL TlsSetValue(
  DWORD dwTlsIndex,  // TLS index
  LPVOID lpTlsValue  // value to store
);

Parameters

dwTlsIndex

[in] Specifies a TLS index that was allocated by the TlsAlloc function.

lpTlsValue

[in] Specifies the value to be stored in the calling thread's TLS slot specified by dwTlsIndex.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

TLS indexes are typically allocated by the TlsAlloc function during process or DLL initialization. Once allocated, each thread of the process can use a TLS index to access its own TLS storage slot for that index. The storage slot for each thread is initialized to NULL. A thread specifies a TLS index in a call to TlsSetValue, to store a value in its slot. The thread specifies the same index in a subsequent call to TlsGetValue, to retrieve the stored value.

TlsSetValue and TlsGetValue were implemented with speed as the primary goal. These functions perform minimal parameter validation and error checking. In particular, this function succeeds if dwTlsIndex is in the range 0 through (TLS_MINIMUM_AVAILABLE – 1). It is up to the programmer to ensure that the index is valid.

Requirements

  Windows NT/2000: Requires Windows NT 3.1 or later.
  Windows 95/98: Requires Windows 95 or later.
  Header: Declared in Winbase.h; include Windows.h.
  Library: Use Kernel32.lib.

See Also

Processes and Threads Overview, Process and Thread Functions, TlsAlloc, TlsFree, TlsGetValue