Reads bytes from file and copies them into the given output buffer.
The output buffer to fill.
Offset with the output buffer to start filling.
The number of bytes to read into the output buffer.
The position within the file to start reading at.
The file read result.
Minimal FileHandle interface for random read access to a file. In Node.js a standard file handle already fulfills this contract. In Browsers it might be needed to read the whole file into memory and then write a simple implementation of this interface to copy the corresponding data to the given output buffer.