Read from the specified input and copy valid UTF‐8 (only) to the specified outputBuffer having the specified outputBufferLength (in bytes). Load the specified status with: * 0 if input reached eof without encountering any invalid UTF‐8 or prematurely exhausting outputBuffer. * A positive value if input was not completely read due to outputBuffer being filled (or nearly filled) without encountering any invalid UTF‐8. * A negative value from ErrorStatus if invalid UTF‐8 was encountered (without having written the invalid sequence to outputBuffer). Return the number of bytes of valid UTF‐8 written to 'outputBuffer. If no invalid UTF‐8 is encountered, or if input supports sputbackc with a putback buffer capacity of at least 4 bytes, input will be left positioned at the end of the valid UTF‐8 read, otherwise, input will be left in an unspecified state. The behavior is undefined unless 4 <= outputBufferLength. Note that this function will stop reading input when less than 4 bytes of space remain in outputBuffer to prevent the possibility of a 4‐byte UTF‐8 sequence being truncated partway through.