func writeHeader()

in writer.go [386:427]

• 36 lines of code
• 7 McCabe index (conditional complexity)

func writeHeader(w io.Writer, h *header) error {
	const maxUint16 = 1<<16 - 1
	if len(h.Name) > maxUint16 {
		return errLongName
	}
	if len(h.Extra) > maxUint16 {
		return errLongExtra
	}

	var buf [fileHeaderLen]byte
	b := writeBuf(buf[:])
	b.uint32(uint32(fileHeaderSignature))
	b.uint16(h.ReaderVersion)
	b.uint16(h.Flags)
	b.uint16(h.Method)
	b.uint16(h.ModifiedTime)
	b.uint16(h.ModifiedDate)
	// In raw mode (caller does the compression), the values are either
	// written here or in the trailing data descriptor based on the header
	// flags.
	if h.raw && !h.hasDataDescriptor() {
		b.uint32(h.CRC32)
		b.uint32(uint32(min64(h.CompressedSize64, uint32max)))
		b.uint32(uint32(min64(h.UncompressedSize64, uint32max)))
	} else {
		// When this package handle the compression, these values are
		// always written to the trailing data descriptor.
		b.uint32(0) // crc32
		b.uint32(0) // compressed size
		b.uint32(0) // uncompressed size
	}
	b.uint16(uint16(len(h.Name)))
	b.uint16(uint16(len(h.Extra)))
	if _, err := w.Write(buf[:]); err != nil {
		return err
	}
	if _, err := io.WriteString(w, h.Name); err != nil {
		return err
	}
	_, err := w.Write(h.Extra)
	return err
}