compress/bzip2: fix bugs

(Once again, proving that a fuzz tester is the first thing that I
should try.)

R=bradfitzgo
CC=golang-dev
https://golang.org/cl/4227042

src/pkg/compress/bzip2/bzip2.go

@@ -141,6 +141,8 @@ func (bz2 *reader) read(buf []byte) (n int, err os.Error) {
 
 		if bz2.lastByte == int(b) {
 			bz2.byteRepeats++
+		} else {
+			bz2.byteRepeats = 0
 		}
 		bz2.lastByte = int(b)
 
@@ -229,6 +231,18 @@ func (bz2 *reader) readBlock() (err os.Error) {
 		treeIndexes[i] = uint8(mtfTreeDecoder.Decode(c))
 	}
 
+	// The list of symbols for the move-to-front transform is taken from
+	// the previously decoded symbol bitmap.
+	symbols := make([]byte, numSymbols)
+	nextSymbol := 0
+	for i := 0; i < 256; i++ {
+		if symbolPresent[i] {
+			symbols[nextSymbol] = byte(i)
+			nextSymbol++
+		}
+	}
+	mtf := newMTFDecoder(symbols)
+
 	numSymbols += 2 // to account for RUNA and RUNB symbols
 	huffmanTrees := make([]huffmanTree, numHuffmanTrees)
 
@@ -259,18 +273,6 @@ func (bz2 *reader) readBlock() (err os.Error) {
 		}
 	}
 
-	// The list of symbols for the move-to-front transform is taken from
-	// the previously decoded symbol bitmap.
-	symbols := make([]byte, numSymbols)
-	nextSymbol := 0
-	for i := 0; i < 256; i++ {
-		if symbolPresent[i] {
-			symbols[nextSymbol] = byte(i)
-			nextSymbol++
-		}
-	}
-	mtf := newMTFDecoder(symbols)
-
 	selectorIndex := 1 // the next tree index to use
 	currentHuffmanTree := huffmanTrees[treeIndexes[0]]
 	bufIndex := 0 // indexes bz2.buf, the output buffer.

src/pkg/compress/bzip2/bzip2_test.go

@@ -92,20 +92,35 @@ func Test1MBZeros(t *testing.T) {
 	testZeros(t, oneMBZerosBZ2Hex, 1024*1024)
 }
 
-func TestRandomData(t *testing.T) {
-	out, err := decompressHex(randBZ2Hex)
+func testRandomData(t *testing.T, compressedHex, uncompressedHex string) {
+	out, err := decompressHex(compressedHex)
 	if err != nil {
 		t.Errorf("error from Read: %s", err)
 		return
 	}
 
-	expected, _ := hex.DecodeString(randHex)
+	expected, _ := hex.DecodeString(uncompressedHex)
 
 	if !bytes.Equal(out, expected) {
-		t.Error("incorrect result")
+		t.Errorf("incorrect result\ngot:  %x\nwant: %x", out, expected)
 	}
 }
 
+func TestRandomData1(t *testing.T) {
+	testRandomData(t, randBZ2Hex, randHex)
+}
+
+func TestRandomData2(t *testing.T) {
+	// This test involves several repeated bytes in the output, but they
+	// should trigger RLE decoding.
+	testRandomData(t, rand2BZ2Hex, rand2Hex)
+}
+
+func TestRandomData3(t *testing.T) {
+	// This test uses the full range of symbols.
+	testRandomData(t, rand3BZ2Hex, rand3Hex)
+}
+
 func Test1MBSawtooth(t *testing.T) {
 	out, err := decompressHex(oneMBSawtoothBZ2Hex)
 	if err != nil {
@@ -135,3 +150,9 @@ const randBZ2Hex = "425a6839314159265359905d990d0001957fffffffffffafffffffffffff
 const randHex = "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"
 
 const oneMBSawtoothBZ2Hex = "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"
+
+const rand2BZ2Hex = "425a6839314159265359d992d0f60000137dfe84020310091c1e280e100e042801099210094806c0110002e70806402000546034000034000000f2830000032000d3403264049270eb7a9280d308ca06ad28f6981bee1bf8160727c7364510d73a1e123083421b63f031f63993a0f40051fbf177245385090d992d0f60"
+const rand2Hex = "92d5652616ac444a4a04af1a8a3964aca0450d43d6cf233bd03233f4ba92f8719e6c2a2bd4f5f88db07ecd0da3a33b263483db9b2c158786ad6363be35d17335ba"
+
+const rand3BZ2Hex = "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"
+const rand3Hex = "1744b384d68c042371244e13500d4bfb98c6244e3d71a5b700224420b59c593553f33bd786e3d0ce31626f511bc985f59d1a88aa38ba8ad6218d306abee60dd9172540232b95be1af146c69e72e5fde667a090dc3f93bdc5c5af0ab80acdbaa7a505f628c59dc0247b31a439cacf5010a94376d71521df08c178b02fb96fdb1809144ea38c68536187c53201fea8631fb0a880b4451ccdca7cc61f6aafca21cc7449d920599db61789ac3b1e164b3390124f95022aeea39ccca3ec1053f4fa10de2978e2861ea58e477085c2220021a0927aa94c5d0006b5055abba340e4f9eba22e969978dfd18e278a8b89d877328ae34268bc0174cfe211954c0036f078025217d1269fac1932a03b05a0b616012271bbe1fb554171c7a59b196d8a4479f45a77931b5d97aaf6c0c673cbe597b79b96e2a0c1eae2e66e46ccc8c85798e23ffe972ebdaa3f6caea243c004e60321eb47cd79137d78fd0613be606feacc5b3637bdc96a89c13746db8cad886f3ccf912b2178c823bcac395f06d28080269bdca2debf3419c66c690fd1adcfbd53e32e79443d7a42511a84cb22ca94fffad9149275a075b2f8ae0b021dcde9bf62b102db920733b897560518b06e1ad7f4b03458493ddaa7f4fa2c1609f7a1735aeeb1b3e2cea3ab45fc376323cc91873b7e9c90d07c192e38d3f5dfc9bfab1fd821c854da9e607ea596c391c7ec4161c6c4493929a8176badaa5a5af7211c623f29643a937677d3df0da9266181b7c4da5dd40376db677fe8f4a1dc456adf6f33c1e37cec471dd318c2647644fe52f93707a77da7d1702380a80e14cc0fdce7bf2eed48a529090bae0388ee277ce6c7018c5fb00b88362554362205c641f0d0fab94fd5b8357b5ff08b207fee023709bc126ec90cfb17c006754638f8186aaeb1265e80be0c1189ec07d01d5f6f96cb9ce82744147d18490de7dc72862f42f024a16968891a356f5e7e0e695d8c933ba5b5e43ad4c4ade5399bc2cae9bb6189b7870d7f22956194d277f28b10e01c10c6ffe3e065f7e2d6d056aa790db5649ca84dc64c35566c0af1b68c32b5b7874aaa66467afa44f40e9a0846a07ae75360a641dd2acc69d93219b2891f190621511e62a27f5e4fbe641ece1fa234fc7e9a74f48d2a760d82160d9540f649256b169d1fed6fbefdc491126530f3cbad7913e19fbd7aa53b1e243fbf28d5f38c10ebd77c8b986775975cc1d619efb27cdcd733fa1ca36cffe9c0a33cc9f02463c91a886601fd349efee85ef1462065ef9bd2c8f533220ad93138b8382d5938103ab25b2d9af8ae106e1211eb9b18793fba033900c809c02cd6d17e2f3e6fc84dae873411f8e87c3f0a8f1765b7825d185ce3730f299c3028d4a62da9ee95c2b870fb70c79370d485f9d5d9acb78926d20444033d960524d2776dc31988ec7c0dbf23b9905d"

src/pkg/compress/bzip2/move_to_front.go

@@ -13,7 +13,7 @@ package bzip2
 // as the symbol will be at the front of the list after the first access.
 type moveToFrontDecoder struct {
 	// Rather than actually keep the list in memory, the symbols are stored
-	// as a circular, double linked list which the symbol indexed by head
+	// as a circular, double linked list with the symbol indexed by head
 	// at the front of the list.
 	symbols []byte
 	next    []uint8
@@ -24,6 +24,10 @@ type moveToFrontDecoder struct {
 // newMTFDecoder creates a move-to-front decoder with an explicit initial list
 // of symbols.
 func newMTFDecoder(symbols []byte) *moveToFrontDecoder {
+	if len(symbols) > 256 {
+		panic("too many symbols")
+	}
+
 	m := &moveToFrontDecoder{
 		symbols: symbols,
 		next:    make([]uint8, len(symbols)),