Stream.readBytes() read characters from a stream into a buffer. The function terminates if the determined length has been read, or it times out (see setTimeout()). readBytes() returns the number of characters placed in the buffer. A 0 means no valid data was found.
This function is part of the Stream class, and is called by any class that inherits from it (Wire, Serial, etc). See the Stream class main page for more information.
stream : an instance of a class that inherits from Stream.
buffer: the buffer to store the bytes in (char or byte)
length : the number of bytes to read (int)