in reader.go [266:279]
func (f *File) findBodyOffset() (int64, error) {
var buf [fileHeaderLen]byte
if _, err := f.zipr.ReadAt(buf[:], f.headerOffset); err != nil {
return 0, err
}
b := readBuf(buf[:])
if sig := b.uint32(); sig != fileHeaderSignature {
return 0, ErrFormat
}
b = b[22:] // skip over most of the header
filenameLen := int(b.uint16())
extraLen := int(b.uint16())
return int64(fileHeaderLen + filenameLen + extraLen), nil
}