/
decompress.go
209 lines (177 loc) · 4.24 KB
/
decompress.go
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// Author: Niels A.D.
// Project: gowarcraft3 (https://github.com/nielsAD/gowarcraft3)
// License: Mozilla Public License, v2.0
package w3g
import (
"bufio"
"compress/zlib"
"hash"
"hash/crc32"
"io"
"io/ioutil"
"github.com/nielsAD/gowarcraft3/protocol"
)
// Decompressor is an io.Reader that decompresses data blocks
type Decompressor struct {
RecordDecoder
SizeRead uint32 // Compressed size read in total
SizeTotal uint32 // Decompressed size left to read in total
SizeBlock uint32 // Decompressed size left to read current block
NumBlocks uint32 // Blocks left to read
r io.Reader
z io.ReadCloser
tee io.Reader
lim *io.LimitedReader
crc hash.Hash32
crcData uint16
buf [12]byte
bufr *bufio.Reader
}
// NewDecompressor for compressed w3g data
func NewDecompressor(r io.Reader, e Encoding, f RecordFactory, numBlocks uint32, sizeTotal uint32) *Decompressor {
var lim = io.LimitedReader{R: r}
var crc = crc32.NewIEEE()
var tee = &toByteReader{Reader: io.TeeReader(&lim, crc)}
return &Decompressor{
RecordDecoder: RecordDecoder{
RecordFactory: f,
Encoding: e,
},
SizeTotal: sizeTotal,
NumBlocks: numBlocks,
r: r,
tee: tee,
lim: &lim,
crc: crc,
}
}
// For some reason, zlib wants a flate.Reader (io.Reader + io.ByteReader), otherwise
// it implicitly uses a bufio.Reader. Use our own straightforward implementation to
// reduce allocations and prevent reading more than necessary.
type toByteReader struct {
io.Reader
b [1]byte
}
// ReadByte implements io.ByteReader interface
func (r *toByteReader) ReadByte() (byte, error) {
_, err := r.Read(r.b[:])
return r.b[0], err
}
func (d *Decompressor) nextBlock() error {
if d.NumBlocks == 0 {
return io.EOF
}
if err := d.closeBlock(); err != nil {
return err
}
d.NumBlocks--
var lenHead = len(d.buf)
if d.GameVersion > 0 && d.GameVersion < 10032 {
lenHead -= 4
}
n, err := io.ReadFull(d.r, d.buf[:lenHead])
d.SizeRead += uint32(n)
if err != nil {
return err
}
var pbuf = protocol.Buffer{Bytes: d.buf[:lenHead]}
var lenDeflate uint32
if d.GameVersion == 0 || d.GameVersion >= 10032 {
lenDeflate = pbuf.ReadUInt32()
d.SizeBlock = pbuf.ReadUInt32()
} else {
lenDeflate = uint32(pbuf.ReadUInt16())
d.SizeBlock = uint32(pbuf.ReadUInt16())
}
var crcHead = pbuf.ReadUInt16()
d.crcData = pbuf.ReadUInt16()
d.buf[lenHead-4], d.buf[lenHead-3], d.buf[lenHead-2], d.buf[lenHead-1] = 0, 0, 0, 0
var crc = crc32.ChecksumIEEE(d.buf[:lenHead])
if crcHead != uint16(crc^crc>>16) {
return ErrInvalidChecksum
}
// Use limr to keep track of how many compressed bytes are read
d.lim.R = d.r
d.lim.N = int64(lenDeflate)
d.crc.Reset()
if d.z == nil {
d.z, err = zlib.NewReader(d.tee)
} else {
err = d.z.(zlib.Resetter).Reset(d.tee, nil)
}
// Account for zlib header
d.SizeRead += lenDeflate - uint32(d.lim.N)
return err
}
func (d *Decompressor) closeBlock() error {
if d.SizeBlock > 0 || d.lim.N > 0 {
return io.ErrUnexpectedEOF
}
var sum = d.crc.Sum32()
if d.crcData != uint16(sum^sum>>16) {
return ErrInvalidChecksum
}
return nil
}
// Read implements the io.Reader interface.
func (d *Decompressor) Read(b []byte) (int, error) {
if d.SizeTotal == 0 {
return 0, io.EOF
}
var n = 0
var l = len(b)
if uint32(l) > d.SizeTotal {
b = b[:d.SizeTotal]
l = len(b)
}
for n != l {
if d.SizeBlock == 0 {
if err := d.nextBlock(); err != nil {
return n, err
}
}
var r = d.lim.N
nn, err := io.ReadFull(d.z, b[n:])
d.SizeRead += uint32(r - d.lim.N)
d.SizeTotal -= uint32(nn)
d.SizeBlock -= uint32(nn)
n += nn
switch err {
case nil:
if d.SizeTotal == 0 && d.SizeBlock > 0 {
nn, _ := io.Copy(ioutil.Discard, d.z)
d.SizeBlock -= uint32(nn)
}
if d.SizeBlock > 0 {
continue
}
fallthrough
case io.ErrUnexpectedEOF:
if err := d.closeBlock(); err != nil {
return n, err
}
default:
return n, err
}
}
return n, nil
}
// ForEach record call f
func (d *Decompressor) ForEach(f func(r Record) error) error {
if d.bufr == nil {
d.bufr = bufio.NewReaderSize(d, 8192)
}
for {
rec, _, err := d.RecordDecoder.Read(d.bufr)
switch err {
case nil:
if err := f(rec); err != nil {
return err
}
case io.EOF:
return nil
default:
return err
}
}
}