Decouple bitmuncher (#495)

* adding comments to d2interface for linter

* moved d2render renderer interfaces and types into d2interface

* fixed most lint errors for monstats loader

* decouple bitmuncher to interface

d2common/bitmuncher.go

@@ -1,66 +1,117 @@
 package d2common
 
+import "github.com/OpenDiablo2/OpenDiablo2/d2common/d2interface"
+
+// BitMuncher is used for parsing files that are not byte-aligned such as the DCC files.
 type BitMuncher struct {
 	data     []byte
-	Offset   int
-	BitsRead int
+	offset   int
+	bitsRead int
 }
 
-func CreateBitMuncher(data []byte, offset int) *BitMuncher {
-	return &BitMuncher{
-		data:     data,
-		Offset:   offset,
-		BitsRead: 0,
-	}
+const (
+	twosComplimentNegativeOne = 4294967295
+	byteLen                   = 8
+	oneBit                    = 0x01
+	fourBytes                 = byteLen * 4
+)
+
+// CreateBitMuncher Creates a BitMuncher
+func CreateBitMuncher(data []byte, offset int) d2interface.BitMuncher {
+	return (&BitMuncher{}).Init(data, offset)
 }
 
-func CopyBitMuncher(source *BitMuncher) *BitMuncher {
-	return &BitMuncher{
-		source.data,
-		source.Offset,
-		0,
-	}
+// CopyBitMuncher Creates a copy of the source BitMuncher
+func CopyBitMuncher(source d2interface.BitMuncher) d2interface.BitMuncher {
+	return source.Copy()
 }
 
+// Init initializes the BitMuncher with data and an offset
+func (v *BitMuncher) Init(data []byte, offset int) d2interface.BitMuncher {
+	v.data = data
+	v.offset = offset
+	v.bitsRead = 0
+
+	return v
+}
+
+// Copy returns a copy of a BitMuncher
+func (v BitMuncher) Copy() d2interface.BitMuncher {
+	v.bitsRead = 0
+	return &v
+}
+
+// Offset returns the offset of the BitMuncher
+func (v *BitMuncher) Offset() int {
+	return v.offset
+}
+
+// SetOffset sets the offset of the BitMuncher
+func (v *BitMuncher) SetOffset(n int) {
+	v.offset = n
+}
+
+// BitsRead returns the number of bits the BitMuncher has read
+func (v *BitMuncher) BitsRead() int {
+	return v.bitsRead
+}
+
+// SetBitsRead sets the number of bits the BitMuncher has read
+func (v *BitMuncher) SetBitsRead(n int) {
+	v.bitsRead = n
+}
+
+// GetBit reads a bit and returns it as uint32
 func (v *BitMuncher) GetBit() uint32 {
-	result := uint32(v.data[v.Offset/8]>>uint(v.Offset%8)) & 0x01
-	v.Offset++
-	v.BitsRead++
+	result := uint32(v.data[v.offset/byteLen]>>uint(v.offset%byteLen)) & oneBit
+	v.offset++
+	v.bitsRead++
+
 	return result
 }
 
+// SkipBits skips bits, incrementing the offset and bits read
 func (v *BitMuncher) SkipBits(bits int) {
-	v.Offset += bits
-	v.BitsRead += bits
+	v.offset += bits
+	v.bitsRead += bits
 }
 
+// GetByte reads a byte from data
 func (v *BitMuncher) GetByte() byte {
-	return byte(v.GetBits(8))
+	return byte(v.GetBits(byteLen))
 }
 
+// GetInt32 reads an int32 from data
 func (v *BitMuncher) GetInt32() int32 {
-	return v.MakeSigned(v.GetBits(32), 32)
+	return v.MakeSigned(v.GetBits(fourBytes), fourBytes)
 }
 
+// GetUInt32 reads an unsigned uint32 from data
 func (v *BitMuncher) GetUInt32() uint32 {
-	return v.GetBits(32)
+	return v.GetBits(fourBytes)
 }
 
+// GetBits given a number of bits to read, reads that number of
+// bits and retruns as a uint32
 func (v *BitMuncher) GetBits(bits int) uint32 {
 	if bits == 0 {
 		return 0
 	}
+
 	result := uint32(0)
 	for i := 0; i < bits; i++ {
 		result |= v.GetBit() << uint(i)
 	}
+
 	return result
 }
 
+// GetSignedBits Given a number of bits, reads that many bits and returns as int
 func (v *BitMuncher) GetSignedBits(bits int) int {
 	return int(v.MakeSigned(v.GetBits(bits), bits))
 }
 
+// MakeSigned converts a uint32 value into an int32
 func (v *BitMuncher) MakeSigned(value uint32, bits int) int32 {
 	if bits == 0 {
 		return 0
@@ -73,13 +124,17 @@ func (v *BitMuncher) MakeSigned(value uint32, bits int) int32 {
 	if (value & (1 << uint(bits-1))) == 0 {
 		return int32(value)
 	}
-	// We need to extend the signed bit out so that the negative value  representation still works with the 2s compliment rule.
-	result := uint32(4294967295)
+
+	// We need to extend the signed bit out so that the negative value
+	// representation still works with the 2s compliment rule.
+	result := uint32(twosComplimentNegativeOne)
+
 	for i := byte(0); i < byte(bits); i++ {
 		if ((value >> uint(i)) & 1) == 0 {
 			result -= uint32(1 << uint(i))
 		}
 	}
+
 	// Force casting to a signed value
 	return int32(result)
 }

d2common/d2fileformats/d2dcc/dcc_direction.go

@@ -3,6 +3,8 @@ package d2dcc
 import (
 	"log"
 
+	"github.com/OpenDiablo2/OpenDiablo2/d2common/d2interface"
+
 	"github.com/OpenDiablo2/OpenDiablo2/d2common"
 )
 
@@ -34,7 +36,7 @@ type DCCDirection struct {
 }
 
 // CreateDCCDirection creates an instance of a DCCDirection.
-func CreateDCCDirection(bm *d2common.BitMuncher, file *DCC) *DCCDirection { //nolint:funlen // Can't reduce
+func CreateDCCDirection(bm d2interface.BitMuncher, file *DCC) *DCCDirection { //nolint:funlen // Can't reduce
 	var crazyBitTable = []byte{0, 1, 2, 4, 6, 8, 10, 12, 14, 16, 20, 24, 26, 28, 30, 32}
 
 	result := &DCCDirection{}
@@ -130,29 +132,29 @@ func CreateDCCDirection(bm *d2common.BitMuncher, file *DCC) *DCCDirection { //no
 	result.PixelBuffer = nil
 
 	// Verify that everything we expected to read was actually read (sanity check)...
-	if equalCellsBitstream.BitsRead != result.EqualCellsBitstreamSize {
+	if equalCellsBitstream.BitsRead() != result.EqualCellsBitstreamSize {
 		log.Panic("Did not read the correct number of bits!")
 	}
 
-	if pixelMaskBitstream.BitsRead != result.PixelMaskBitstreamSize {
+	if pixelMaskBitstream.BitsRead() != result.PixelMaskBitstreamSize {
 		log.Panic("Did not read the correct number of bits!")
 	}
 
-	if encodingTypeBitsream.BitsRead != result.EncodingTypeBitsreamSize {
+	if encodingTypeBitsream.BitsRead() != result.EncodingTypeBitsreamSize {
 		log.Panic("Did not read the correct number of bits!")
 	}
 
-	if rawPixelCodesBitstream.BitsRead != result.RawPixelCodesBitstreamSize {
+	if rawPixelCodesBitstream.BitsRead() != result.RawPixelCodesBitstreamSize {
 		log.Panic("Did not read the correct number of bits!")
 	}
 
-	bm.SkipBits(pixelCodeandDisplacement.BitsRead)
+	bm.SkipBits(pixelCodeandDisplacement.BitsRead())
 
 	return result
 }
 
 //nolint:gocognit nolint:gocyclo // Can't reduce
-func (v *DCCDirection) generateFrames(pcd *d2common.BitMuncher) {
+func (v *DCCDirection) generateFrames(pcd d2interface.BitMuncher) {
 	pbIdx := 0
 
 	for _, cell := range v.Cells {
@@ -255,7 +257,7 @@ func (v *DCCDirection) generateFrames(pcd *d2common.BitMuncher) {
 }
 
 //nolint:funlen nolint:gocognit // can't reduce
-func (v *DCCDirection) fillPixelBuffer(pcd, ec, pm, et, rp *d2common.BitMuncher) {
+func (v *DCCDirection) fillPixelBuffer(pcd, ec, pm, et, rp d2interface.BitMuncher) {
 	var pixelMaskLookup = []int{0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4}
 
 	lastPixel := uint32(0)

d2common/d2fileformats/d2dcc/dcc_direction_frame.go

@@ -3,6 +3,8 @@ package d2dcc
 import (
 	"log"
 
+	"github.com/OpenDiablo2/OpenDiablo2/d2common/d2interface"
+
 	"github.com/OpenDiablo2/OpenDiablo2/d2common"
 )
 
@@ -24,7 +26,7 @@ type DCCDirectionFrame struct {
 }
 
 // CreateDCCDirectionFrame Creates a DCCDirectionFrame for a DCC.
-func CreateDCCDirectionFrame(bits *d2common.BitMuncher, direction *DCCDirection) *DCCDirectionFrame {
+func CreateDCCDirectionFrame(bits d2interface.BitMuncher, direction *DCCDirection) *DCCDirectionFrame {
 	result := &DCCDirectionFrame{}
 
 	bits.GetBits(direction.Variable0Bits) // Variable0

d2common/d2interface/bitmuncher.go

@@ -0,0 +1,18 @@
+package d2interface
+
+type BitMuncher interface {
+	Init(data []byte, offset int) BitMuncher
+	Copy() BitMuncher
+	Offset() int
+	SetOffset(int)
+	BitsRead() int
+	SetBitsRead(int)
+	GetBit() uint32
+	SkipBits(bits int)
+	GetByte() byte
+	GetInt32() int32
+	GetUInt32() uint32
+	GetBits(bits int) uint32
+	GetSignedBits(bits int) int
+	MakeSigned(value uint32, bits int) int32
+}

d2common/d2interface/bitstream.go

@@ -0,0 +1,8 @@
+package d2interface
+
+type BitStream interface {
+	ReadBits(bitCount int) int
+	PeekByte() int
+	EnsureBits(bitCount int) bool
+	WasteBits(bitCount int)
+}