Write JS string value into char string buffer without a null terminator

CHAKRA_API
    JsCopyStringOneByte(
        _In_ JsValueRef value,
        _In_ int start,
        _In_ int length,
        _Out_opt_ char* buffer,
        _Out_opt_ size_t* written);

• value: JavascriptString value
• start: Start offset of buffer
• length: Number of characters to be written
• buffer: Pointer to buffer
• written: Total number of characters written

The code JsNoError if the operation succeeded, a failure code otherwise.

This API is experimental and may have breaking change later.

When size of the buffer is unknown, buffer argument can be nullptr. In that case, actualLength argument will return the length needed.

When start is out of range or < 0, returns JsErrorInvalidArgument and written will be equal to 0. If calculated length is 0 (It can be due to string length or start and length combination), then written will be equal to 0 and call returns JsNoError.

The JS string value will be converted one utf16 code point at a time, and if it has code points that do not fit in one byte, those values will be truncated.