func writeHeader(w io.Writer, h *czip.File, canonicalName string) error {
var buf [fileHeaderLen]byte
b := writeBuf(buf[:])
b.uint32(uint32(fileHeaderSignature))
if isZip64(h) {
b.uint16(zipVersion45)
} else {
b.uint16(zipVersion20)
}
b.uint16(2)
b.uint16(8)
b.uint16(48128)
b.uint16(8600)
b.uint32(h.CRC32)
if isZip64(h) {
// the file needs a zip64 header. store maxint in both
// 32 bit size fields to signal that the
// zip64 extra header should be used.
b.uint32(uint32max) // compressed size
b.uint32(uint32max) // uncompressed size
// append a zip64 extra block to Extra
var buf [20]byte // 2x uint16 + 2x uint64
eb := writeBuf(buf[:])
eb.uint16(zip64ExtraId)
eb.uint16(16) // size = 2x uint64
eb.uint64(h.UncompressedSize64)
eb.uint64(h.CompressedSize64)
h.Extra = append(h.Extra, buf[:]...)
} else {
b.uint32(h.CompressedSize)
b.uint32(h.UncompressedSize)
}
b.uint16(uint16(len(canonicalName)))
b.uint16(uint16(len(h.Extra)))
if _, err := w.Write(buf[:]); err != nil {
return err
}
if _, err := io.WriteString(w, canonicalName); err != nil {
return err
}
_, err := w.Write(h.Extra)
return err
}
func writeCentralHeader(w io.Writer, h *czip.File, canonicalName string, offset int64) error {
var buf [directoryHeaderLen]byte
b := writeBuf(buf[:])
b.uint32(uint32(directoryHeaderSignature))
b.uint16(creatorFAT)
if isZip64(h) || offset > uint32max {
b.uint16(zipVersion45)
} else {
b.uint16(zipVersion20)
}
b.uint16(2)
b.uint16(8)
b.uint16(48128)
b.uint16(8600)
b.uint32(h.CRC32)
if h.CompressedSize64 > uint32max {
b.uint32(uint32max)
} else {
b.uint32(uint32(h.CompressedSize64))
}
if h.UncompressedSize64 > uint32max {
b.uint32(uint32max)
} else {
b.uint32(uint32(h.UncompressedSize64))
}
b.uint16(uint16(len(canonicalName)))
if isZip64(h) || offset > uint32max {
var esize uint16
if h.CompressedSize64 > uint32max {
esize += 8
}
if h.UncompressedSize64 > uint32max {
esize += 8
}
if offset > uint32max {
esize += 8
}
var b1 [4]byte
eb := writeBuf(b1[:])
eb.uint16(zip64ExtraId)
eb.uint16(esize)
h.Extra = append(h.Extra, b1[:]...)
if h.UncompressedSize64 > uint32max {
var b2 [8]byte
eb := writeBuf(b2[:])
eb.uint64(h.UncompressedSize64)
h.Extra = append(h.Extra, b2[:]...)
}
if h.CompressedSize64 > uint32max {
var b2 [8]byte
eb := writeBuf(b2[:])
eb.uint64(h.CompressedSize64)
h.Extra = append(h.Extra, b2[:]...)
}
if offset > uint32max {
var b3 [8]byte
eb := writeBuf(b3[:])
eb.uint64(uint64(offset))
h.Extra = append(h.Extra, b3[:]...)
}
}
b.uint16(uint16(len(h.Extra)))
b.uint16(0)
b.uint16(0)
b.uint16(0)
b.uint32(0)
if offset > uint32max {
b.uint32(uint32max)
} else {
b.uint32(uint32(offset))
}
if _, err := w.Write(buf[:]); err != nil {
return err
}
if _, err := io.WriteString(w, canonicalName); err != nil {
return err
}
_, err := w.Write(h.Extra)
return err
}