#ifndef _NTINTSAFE_H_INCLUDED_
#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP | WINAPI_PARTITION_SYSTEM | WINAPI_PARTITION_GAMES)

//=============================================================================
// Conversion functions
//
// There are three reasons for having conversion functions:
//
// 1. We are converting from a signed type to an unsigned type of the same
//    size, or vice-versa.
//
//    Since we default to only having unsigned math functions,
//    (see ENABLE_INTSAFE_SIGNED_FUNCTIONS below) we prefer people to convert
//    to unsigned, do the math, and then convert back to signed.
//
// 2. We are converting to a smaller type, and we could therefore possibly
//    overflow.
//
// 3. We are converting to a bigger type, and we are signed and the type we are
//    converting to is unsigned.
//
//=============================================================================


//
// INT8 -> UCHAR conversion
//
_Must_inspect_result_
__inline
NTSTATUS
RtlInt8ToUChar(
    _In_ INT8 i8Operand,
    _Out_ _Deref_out_range_(==, i8Operand) UCHAR* pch)
{
    NTSTATUS status;

    if (i8Operand >= 0)
    {
        *pch = (UCHAR)i8Operand;
        status = STATUS_SUCCESS;
    }
    else
    {
        *pch = '\0';
        status = STATUS_INTEGER_OVERFLOW;
    }

    return status;
}

#endif
#endif
View code on GitHub

// ntintsafe.h

NTSTATUS RtlInt8ToUChar(
  [in]  INT8  i8Operand,
  [out] UCHAR *pch
);
View the official Windows Driver Kit DDI reference

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Windows Driver Kit DDI reference (nf-ntintsafe-rtlint8touchar)

RtlInt8ToUChar function

Description

Converts a value of type INT8 to a value of type UCHAR.

Parameters

`i8Operand` [in]

The value to be converted.

`pch` [out]

A pointer to the converted value. In the case where the conversion causes a truncation of the original value, the function returns STATUS_INTEGER_OVERFLOW and this parameter is not valid.

Return value

Returns STATUS_SUCCESS if the operation is successful.

See the implementation of this helper function in ntintsafe.h in the WDK for possible error return values.

Remarks

This is one of a set of inline functions designed to provide type conversions and perform validity checks with minimal impact on performance.

View the official Windows Driver Kit DDI reference