redo the bit reader shit

bit.go

@@ -1,117 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"io"
-)
-
-// a bitBuffer is a buffer of raw data that is not necessarily byte-aligned,
-// for performing bitwise reads and manipulation. The bulk of this source is
-// adapted from the bitReader defined in the standard library bzip2 package.
-type bitBuffer struct {
-	source  []byte // the source data to be read. This slice is never modified
-	index   int    // position of the last byte read out of source
-	scratch uint64 // scratch register of bits worthy of manipulation
-	bits    uint   // bit width of the scratch register
-	err     error  // stored error
-}
-
-func newBitBuffer(buf []byte) *bitBuffer {
-	return &bitBuffer{source: buf}
-}
-
-func (b *bitBuffer) readBits(bits uint) uint64 {
-	for bits > b.bits {
-		if b.index >= len(b.source) {
-			b.err = io.ErrUnexpectedEOF
-			return 0
-		}
-		b.scratch <<= 8
-		b.scratch |= uint64(b.source[b.index])
-		b.index += 1
-		b.bits += 8
-	}
-
-	// b.scratch looks like this (assuming that b.bits = 14 and bits = 6):
-	// Bit: 111111
-	//      5432109876543210
-	//
-	//         (6 bits, the desired output)
-	//        |-----|
-	//        V     V
-	//      0101101101001110
-	//        ^            ^
-	//        |------------|
-	//           b.bits (num valid bits)
-	//
-	// This the next line right shifts the desired bits into the
-	// least-significant places and masks off anything above.
-	n := (b.scratch >> (b.bits - bits)) & ((1 << bits) - 1)
-	b.bits -= bits
-	return n
-}
-
-func (b *bitBuffer) readByte() (out byte) {
-	if b.bits == 0 {
-		if b.index >= len(b.source) {
-			b.err = io.ErrUnexpectedEOF
-			return
-		}
-		out = b.source[b.index]
-		b.index += 1
-		return
-	}
-	return byte(b.readBits(8))
-}
-
-func (b *bitBuffer) readBytes(n int) []byte {
-	if b.bits == 0 {
-		b.index += n
-		if b.index > len(b.source) {
-			b.err = io.ErrUnexpectedEOF
-			return []byte{}
-		}
-		return b.source[b.index-n : b.index]
-	}
-	buf := make([]byte, n)
-	for i := 0; i < n; i++ {
-		buf[i] = byte(b.readBits(8))
-	}
-	return buf
-}
-
-// readVarUint reads a variable-length uint32, encoded with some scheme that I
-// can't find a standard for. first two bits are a length prefix, followed by a
-// 4, 8, 12, or 32-bit wide uint.
-func (b *bitBuffer) readVarUint() uint32 {
-	switch b.readBits(2) {
-	case 0:
-		return uint32(b.readBits(4))
-	case 1:
-		return uint32(b.readBits(4) | b.readBits(4)<<4)
-	case 2:
-		return uint32(b.readBits(4) | b.readBits(8)<<4)
-	case 3:
-		return uint32(b.readBits(4) | b.readBits(28)<<4)
-	default:
-		// this switch is already exhaustive, the compiler just can't tell.
-		panic(fmt.Sprintf("invalid varuint prefix"))
-	}
-}
-
-// readVarInt reads a varint-encoded value off of the front of the buffer. This
-// is the varint encoding used in protobuf. That is: each byte utilizes a 7-bit
-// group. the msb of each byte indicates whether there are more bytes to
-// follow.
-func (b *bitBuffer) readVarInt() uint64 {
-	var x, n uint64
-	for shift := uint(0); shift < 64; shift += 7 {
-		n = b.readBits(8)
-		if n < 0x80 {
-			return x | n<<shift
-		}
-		x |= n &^ 0x80 << shift
-	}
-	b.err = fmt.Errorf("readVarInt never saw the end of varint")
-	return 0
-}

bit/reader.go

@@ -0,0 +1,52 @@
+package bit
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+)
+
+// bit.Reader allows for bit-level reading of arbitrary source data. This is
+// based on the bit reader found in the standard library's bzip2 package.
+// https://golang.org/src/compress/bzip2/bit_reader.go
+type Reader struct {
+	src  io.ByteReader // source of data
+	n    uint64        // bit buffer
+	bits uint          // number of valid bits in n
+	err  error         // stored error
+}
+
+// NewReader creates a new bit.Reader for any arbitrary reader.
+func NewReader(r io.Reader) *Reader {
+	br, ok := r.(io.ByteReader)
+	if !ok {
+		br = bufio.NewReader(r)
+	}
+	return &Reader{src: br}
+}
+
+// NewByteReader creates a bit.Reader for a static slice of bytes. It's just
+// using a bytes.Reader internally.
+func NewBytesReader(b []byte) *Reader {
+	return NewReader(bytes.NewReader(b))
+}
+
+// ReadBits reads the given number of bits and returns them in the
+// least-significant part of a uint64.
+func (r *Reader) ReadBits(bits uint) (n uint64) {
+	for bits > r.bits {
+		b, err := r.src.ReadByte()
+		if err != nil {
+			r.err = err
+			return 0
+		}
+		r.n <<= 8
+		r.n |= uint64(b)
+		r.bits += 8
+	}
+	n = (r.n >> (r.bits - bits)) & ((1 << bits) - 1)
+	r.bits -= bits
+	return
+}
+
+func (r *Reader) Err() error { return r.err }

bit/reader_test.go

@@ -0,0 +1,52 @@
+package bit
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+var (
+	// 1000 1011 1010 1101 1111 0000 0000 1101
+	badFood = []byte{0x8b, 0xad, 0xf0, 0x0d}
+)
+
+func TestRead(t *testing.T) {
+	assert := assert.New(t)
+
+	var r *Reader
+
+	// aligned reading
+	r = NewBytesReader(badFood)
+	assert.Equal(uint64(0x8b), r.ReadBits(8))
+	assert.Equal(uint64(0xad), r.ReadBits(8))
+	assert.Equal(uint64(0xf0), r.ReadBits(8))
+	assert.Equal(uint64(0x0d), r.ReadBits(8))
+
+	// misaligned reading
+	r = NewBytesReader(badFood)
+
+	// 1000 1011 1010 1101 1111 0000 0000 1101
+	// ^
+	assert.Equal(uint64(0x01), r.ReadBits(1))
+
+	// 1000 1011 1010 1101 1111 0000 0000 1101
+	//  ^-^
+	assert.Equal(uint64(0), r.ReadBits(3))
+
+	// 1000 1011 1010 1101 1111 0000 0000 1101
+	//      ^--^
+	assert.Equal(uint64(0xb), r.ReadBits(4))
+
+	// 1000 1011 1010 1101 1111 0000 0000 1101
+	//           ^----^
+	assert.Equal(uint64(0x15), r.ReadBits(5))
+
+	// 1000 1011 1010 1101 1111 0000 0000 1101
+	//                 ^---------^
+	assert.Equal(uint64(0x17c), r.ReadBits(9))
+
+	// 1000 1011 1010 1101 1111 0000 0000 1101
+	//                            ^----------^
+	assert.Equal(uint64(0xd), r.ReadBits(10))
+}

bit_test.go

@@ -1,83 +0,0 @@
-package main
-
-import (
-	"io"
-	"testing"
-)
-
-func TestBits(t *testing.T) {
-	buf := []byte{0x00}
-	bb := newBitBuffer(buf)
-	for i := 0; i < 8; i++ {
-		if bb.readBits(1) != 0x00 {
-			t.Error("hahha what")
-		}
-		if bb.err != nil {
-			t.Errorf("oh weird error: %v", bb.err)
-		}
-	}
-	if bb.readBits(1) != 0x00 {
-		t.Error("hahha what")
-	}
-	if bb.err != io.ErrUnexpectedEOF {
-		t.Errorf("oh weird error: %v", bb.err)
-	}
-
-	buf = []byte{0x10}
-	bb = newBitBuffer(buf)
-	if n := bb.readBits(4); n != 0x01 {
-		t.Errorf("shit. wanted %v, got %v", 0x01, n)
-	}
-	if n := bb.readBits(4); n != 0x00 {
-		t.Errorf("poop. wanted %v, got %v", 0x00, n)
-	}
-	if bb.err != nil {
-		t.Errorf("fuck")
-	}
-
-	buf = []byte{0x4}
-	bb = newBitBuffer(buf)
-	u := bb.readVarUint()
-	if u != 1 {
-		t.Errorf("feck. wanted %v, got %v", 1, u)
-	}
-	if bb.readBits(2); bb.err != nil {
-		t.Errorf("shouldn't have an error yet")
-	}
-	if bb.readBits(1); bb.err == nil {
-		t.Errorf("we should be at EOF now")
-	}
-
-	buf = []byte{0x3c}
-	bb = newBitBuffer(buf)
-	u = bb.readVarUint()
-	if u != 15 {
-		t.Errorf("feck. wanted %v, got %v", 15, u)
-	}
-	if bb.readBits(2); bb.err != nil {
-		t.Errorf("shouldn't have an error yet")
-	}
-	if bb.readBits(1); bb.err == nil {
-		t.Errorf("we should be at EOF now")
-	}
-
-	buf = []byte{0x48, 0x10}
-	// 0100 1000 0001 0000
-	// 01                  - prefix bits. indicates length 12
-	//   00 10             - least significant four
-	//        00 0001 00   - most significant eight
-	//                  00 - not read.
-	//
-	// 0000 0100 0010      - actual value (0x42, or 66)
-	bb = newBitBuffer(buf)
-	u = bb.readVarUint()
-	if u != 66 {
-		t.Errorf("feck. wanted %v, got %v", 66, u)
-	}
-	if bb.readBits(2); bb.err != nil {
-		t.Errorf("shouldn't have an error yet")
-	}
-	if bb.readBits(1); bb.err == nil {
-		t.Errorf("we should be at EOF now")
-	}
-}

glide.lock

@@ -1,10 +1,23 @@
-hash: 9208b00dc0b7be6b23958e0642efb66c8584c0be1d97fd81a9de0df643ac2877
-updated: 2016-07-31T18:52:05.106198608-04:00
+hash: 3f7fbcf64c0749e5f78dc8188c594871ab368257d8a05f238cb2ff901d76f8f8
+updated: 2016-08-01T20:29:43.617478897-04:00
 imports:
 - name: github.com/golang/protobuf
   version: c3cefd437628a0b7d31b34fe44b3a7a540e98527
   subpackages:
   - proto
+  - protoc-gen-go/descriptor
 - name: github.com/golang/snappy
   version: d9eb7a3d35ec988b8585d4a0068e462c27d28380
-testImports: []
+- name: github.com/stretchr/testify
+  version: f390dcf405f7b83c997eac1b06768bb9f44dec18
+  subpackages:
+  - assert
+testImports:
+- name: github.com/davecgh/go-spew
+  version: 5215b55f46b2b919f50a1df0eaa5886afe4e3b3d
+  subpackages:
+  - spew
+- name: github.com/pmezard/go-difflib
+  version: d8ed2627bdf02c080bf22230dbb337003b7aba2d
+  subpackages:
+  - difflib

glide.yaml

@@ -2,3 +2,5 @@ package: github.com/jordanorelli/hyperstone
 import:
 - package: github.com/golang/protobuf
 - package: github.com/golang/snappy
+- package: github.com/stretchr/testify
+  version: ^1.1.3

message.go

@@ -42,18 +42,7 @@ func (m *message) check(dump bool) error {
 	}
 
 	if dump {
-		shit := packet.GetData()[:4]
-		bb := newBitBuffer(packet.GetData())
-		type T struct {
-			t int32
-		}
-		var v T
-		v.t = int32(bb.readVarUint())
-		if bb.err != nil {
-			fmt.Printf("packet error: %v\n", bb.err)
-		} else {
-			fmt.Printf("{in: %d out: %d data: %v shit: %x}\n", packet.GetSequenceIn(), packet.GetSequenceOutAck(), v, shit)
-		}
+		fmt.Println("I broke packet dumping.")
 	}
 	return nil
 }