IDA Help: loader_input_t.read

Read from the input file
     buf - reference to the variable that will hold the read bytes
           in form of a string
     size - number of bytes to read
Returns: number of read bytes

long loader_input_t.read(vref buf, long size);

// For example:
        auto li, buf;
        li = open_loader_input("myfile", 0);
        li.read(&buf, 100);