diff --git a/common/bitutil/compress.go b/common/bitutil/compress.go
index c6c139ab94ef1ca94b1c0fc0d85cb804e4f62d62..a806c0e8b2dab37d827de7db5516803eb45eef7e 100644
--- a/common/bitutil/compress.go
+++ b/common/bitutil/compress.go
@@ -16,78 +16,129 @@
package bitutil
-/*
-The compression algorithm implemented by CompressBytes and DecompressBytes is
-optimized for "sparse" input data which contains a lot of zero bytes. Decompression
-requires knowledge of the decompressed data length. Compression works as follows:
+import "errors"
-if data only contains zeroes,
- CompressBytes(data) == nil
-otherwise if len(data) <= 1,
- CompressBytes(data) == data
-otherwise:
- CompressBytes(data) == append(CompressBytes(nonZeroBits(data)), nonZeroBytes(data)...)
-where
- nonZeroBits(data) is a bit vector with len(data) bits (MSB first):
- nonZeroBits(data)[i/8] && (1 << (7-i%8)) != 0 if data[i] != 0
- len(nonZeroBits(data)) == (len(data)+7)/8
- nonZeroBytes(data) contains the non-zero bytes of data in the same order
-*/
+var (
+ // ErrMissingData is returned from decompression if the byte referenced by
+ // the bitset header overflows the input data.
+ ErrMissingData = errors.New("missing bytes on input")
-// CompressBytes compresses the input byte slice
+ // ErrUnreferencedData is returned from decompression if not all bytes were used
+ // up from the input data after decompressing it.
+ ErrUnreferencedData = errors.New("extra bytes on input")
+
+ // ErrExceededTarget is returned from decompression if the bitset header has
+ // more bits defined than the number of target buffer space available.
+ ErrExceededTarget = errors.New("target data size exceeded")
+
+ // ErrZeroContent is returned from decompression if a data byte referenced in
+ // the bitset header is actually a zero byte.
+ ErrZeroContent = errors.New("zero byte in input content")
+)
+
+// The compression algorithm implemented by CompressBytes and DecompressBytes is
+// optimized for sparse input data which contains a lot of zero bytes. Decompression
+// requires knowledge of the decompressed data length.
+//
+// Compression works as follows:
+//
+// if data only contains zeroes,
+// CompressBytes(data) == nil
+// otherwise if len(data) <= 1,
+// CompressBytes(data) == data
+// otherwise:
+// CompressBytes(data) == append(CompressBytes(nonZeroBitset(data)), nonZeroBytes(data)...)
+// where
+// nonZeroBitset(data) is a bit vector with len(data) bits (MSB first):
+// nonZeroBitset(data)[i/8] && (1 << (7-i%8)) != 0 if data[i] != 0
+// len(nonZeroBitset(data)) == (len(data)+7)/8
+// nonZeroBytes(data) contains the non-zero bytes of data in the same order
+
+// CompressBytes compresses the input byte slice according to the sparse bitset
+// representation algorithm.
func CompressBytes(data []byte) []byte {
+ // Empty slices get compressed to nil
if len(data) == 0 {
return nil
}
+ // One byte slices compress to nil or retain the single byte
if len(data) == 1 {
if data[0] == 0 {
return nil
- } else {
- return data
}
+ return data
}
-
- bitsLen := (len(data) + 7) / 8
- nonZeroBits := make([]byte, bitsLen)
+ // Calculate the bitset of set bytes, and gather the non-zero bytes
+ nonZeroBitset := make([]byte, (len(data)+7)/8)
nonZeroBytes := make([]byte, 0, len(data))
+
for i, b := range data {
if b != 0 {
nonZeroBytes = append(nonZeroBytes, b)
- nonZeroBits[i/8] |= 1 << byte(7-i%8)
+ nonZeroBitset[i/8] |= 1 << byte(7-i%8)
}
}
if len(nonZeroBytes) == 0 {
return nil
}
- return append(CompressBytes(nonZeroBits), nonZeroBytes...)
+ return append(CompressBytes(nonZeroBitset), nonZeroBytes...)
}
-// DecompressBytes decompresses data with a known target size.
-// In addition to the decompressed output, the function returns the length of
-// compressed input data corresponding to the output. The input slice may be longer.
-// If the input slice is too short, (nil, -1) is returned.
-func DecompressBytes(data []byte, targetLen int) ([]byte, int) {
- decomp := make([]byte, targetLen)
- if len(data) == 0 {
- return decomp, 0
+// DecompressBytes decompresses data with a known target size. In addition to the
+// decompressed output, the function returns the length of compressed input data
+// corresponding to the output as the input slice may be longer.
+func DecompressBytes(data []byte, target int) ([]byte, error) {
+ out, size, err := decompressBytes(data, target)
+ if err != nil {
+ return nil, err
}
- if targetLen == 1 {
- return data[0:1], 1
+ if size != len(data) {
+ return nil, ErrUnreferencedData
}
+ return out, nil
+}
- bitsLen := (targetLen + 7) / 8
- nonZeroBits, ptr := DecompressBytes(data, bitsLen)
- if ptr < 0 {
- return nil, -1
+// decompressBytes decompresses data with a known target size. In addition to the
+// decompressed output, the function returns the length of compressed input data
+// corresponding to the output as the input slice may be longer.
+func decompressBytes(data []byte, target int) ([]byte, int, error) {
+ // Sanity check 0 targets to avoid infinite recursion
+ if target == 0 {
+ return nil, 0, nil
+ }
+ // Handle the zero and single byte corner cases
+ decomp := make([]byte, target)
+ if len(data) == 0 {
+ return decomp, 0, nil
+ }
+ if target == 1 {
+ decomp[0] = data[0] // copy to avoid referencing the input slice
+ if data[0] != 0 {
+ return decomp, 1, nil
+ }
+ return decomp, 0, nil
+ }
+ // Decompress the bitset of set bytes and distribute the non zero bytes
+ nonZeroBitset, ptr, err := decompressBytes(data, (target+7)/8)
+ if err != nil {
+ return nil, ptr, err
}
- for i, _ := range decomp {
- if nonZeroBits[i/8]&(1<<byte(7-i%8)) != 0 {
- if ptr == len(data) {
- return nil, -1
+ for i := 0; i < 8*len(nonZeroBitset); i++ {
+ if nonZeroBitset[i/8]&(1<<byte(7-i%8)) != 0 {
+ // Make sure we have enough data to push into the correct slot
+ if ptr >= len(data) {
+ return nil, 0, ErrMissingData
+ }
+ if i >= len(decomp) {
+ return nil, 0, ErrExceededTarget
+ }
+ // Make sure the data is valid and push into the slot
+ if data[ptr] == 0 {
+ return nil, 0, ErrZeroContent
}
decomp[i] = data[ptr]
ptr++
}
}
- return decomp, ptr
+ return decomp, ptr, nil
}
diff --git a/common/bitutil/compress_fuzz.go b/common/bitutil/compress_fuzz.go
new file mode 100644
index 0000000000000000000000000000000000000000..2b7fe29775a0ee878faa16a8ae06234f4b15bd3a
--- /dev/null
+++ b/common/bitutil/compress_fuzz.go
@@ -0,0 +1,56 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// +build gofuzz
+
+package bitutil
+
+import "bytes"
+
+// Fuzz implements a go-fuzz fuzzer method to test various compression method
+// invocations.
+func Fuzz(data []byte) int {
+ if len(data) == 0 {
+ return -1
+ }
+ if data[0]%2 == 0 {
+ return fuzzCompress(data[1:])
+ }
+ return fuzzDecompress(data[1:])
+}
+
+// fuzzCompress implements a go-fuzz fuzzer method to test the bit compression and
+// decompression algorithm.
+func fuzzCompress(data []byte) int {
+ proc, _ := DecompressBytes(CompressBytes(data), len(data))
+ if !bytes.Equal(data, proc) {
+ panic("content mismatch")
+ }
+ return 0
+}
+
+// fuzzDecompress implements a go-fuzz fuzzer method to test the bit decompression
+// and recompression algorithm.
+func fuzzDecompress(data []byte) int {
+ blob, err := DecompressBytes(data, 1024)
+ if err != nil {
+ return 0
+ }
+ if comp := CompressBytes(blob); !bytes.Equal(comp, data) {
+ panic("content mismatch")
+ }
+ return 0
+}
diff --git a/common/bitutil/compress_test.go b/common/bitutil/compress_test.go
new file mode 100644
index 0000000000000000000000000000000000000000..ef38bc7b3897a3c0512c3db701e4e16dfcc8ff65
--- /dev/null
+++ b/common/bitutil/compress_test.go
@@ -0,0 +1,152 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package bitutil
+
+import (
+ "bytes"
+ "math/rand"
+ "testing"
+
+ "github.com/ethereum/go-ethereum/common/hexutil"
+)
+
+// Tests that data compression and decompression works correctly.
+func TestCompressCycle(t *testing.T) {
+ tests := []string{
+ // Tests generated by go-fuzz to maximize code coverage
+ "0x000000000000000000",
+ "0xef0400",
+ "0xdf7070533534333636313639343638373532313536346c1bc33339343837313070706336343035336336346c65fefb3930393233383838ac2f65fefb",
+ "0x7b64000000",
+ "0x000034000000000000",
+ "0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000f0000000000000000000",
+ "0x4912385c0e7b64000000",
+ "0x000034000000000000000000000000000000",
+ "0x00",
+ "0x000003e834ff7f0000",
+ "0x0000",
+ "0x0000000000000000000000000000000000000000000000000000000000ff00",
+ "0x895f0c6a020f850c6a020f85f88df88d",
+ "0xdf7070533534333636313639343638373432313536346c1bc3315aac2f65fefb",
+ "0x0000000000",
+ "0xdf70706336346c65fefb",
+ "0x00006d643634000000",
+ "0xdf7070533534333636313639343638373532313536346c1bc333393438373130707063363430353639343638373532313536346c1bc333393438336336346c65fe",
+ }
+ for i, tt := range tests {
+ data := hexutil.MustDecode(tt)
+
+ proc, err := DecompressBytes(CompressBytes(data), len(data))
+ if err != nil {
+ t.Errorf("test %d: failed to decompress compressed data: %v", i, err)
+ continue
+ }
+ if !bytes.Equal(data, proc) {
+ t.Errorf("test %d: compress/decompress mismatch: have %x, want %x", i, proc, data)
+ }
+ }
+}
+
+// Tests that data decompression works
+func TestDecompress(t *testing.T) {
+ tests := []struct {
+ size int
+ input string
+ fail error
+ }{
+ {size: 0, input: "0x"},
+
+ // Crashers generated by go-fuzz
+ {size: 0, input: "0x0020", fail: ErrUnreferencedData},
+ {size: 0, input: "0x30", fail: ErrUnreferencedData},
+ {size: 1, input: "0x00", fail: ErrUnreferencedData},
+ {size: 2, input: "0x07", fail: ErrMissingData},
+ {size: 1024, input: "0x8000", fail: ErrZeroContent},
+
+ // Tests generated by go-fuzz to maximize code coverage
+ {size: 29490, input: "0x343137343733323134333839373334323073333930783e3078333930783e70706336346c65303e", fail: ErrMissingData},
+ {size: 59395, input: "0x00", fail: ErrUnreferencedData},
+ {size: 52574, input: "0x70706336346c65c0de", fail: ErrExceededTarget},
+ {size: 42264, input: "0x07", fail: ErrMissingData},
+ {size: 52, input: "0xa5045bad48f4", fail: ErrExceededTarget},
+ {size: 52574, input: "0xc0de", fail: ErrMissingData},
+ {size: 52574, input: "0x"},
+ {size: 29490, input: "0x34313734373332313433383937333432307333393078073034333839373334323073333930783e3078333937333432307333393078073061333930783e70706336346c65303e", fail: ErrMissingData},
+ {size: 29491, input: "0x3973333930783e30783e", fail: ErrMissingData},
+
+ {size: 1024, input: "0x808080608080"},
+ {size: 1024, input: "0x808470705e3632383337363033313434303137393130306c6580ef46806380635a80"},
+ {size: 1024, input: "0x8080808070"},
+ {size: 1024, input: "0x808070705e36346c6580ef46806380635a80"},
+ {size: 1024, input: "0x80808046802680"},
+ {size: 1024, input: "0x4040404035"},
+ {size: 1024, input: "0x4040bf3ba2b3f684402d353234373438373934409fe5b1e7ada94ebfd7d0505e27be4035"},
+ {size: 1024, input: "0x404040bf3ba2b3f6844035"},
+ {size: 1024, input: "0x40402d35323437343837393440bfd7d0505e27be4035"},
+ }
+ for i, tt := range tests {
+ data := hexutil.MustDecode(tt.input)
+
+ orig, err := DecompressBytes(data, tt.size)
+ if err != tt.fail {
+ t.Errorf("test %d: failure mismatch: have %v, want %v", i, err, tt.fail)
+ }
+ if err != nil {
+ continue
+ }
+ if comp := CompressBytes(orig); !bytes.Equal(comp, data) {
+ t.Errorf("test %d: decompress/compress mismatch: have %x, want %x", i, comp, data)
+ }
+ }
+}
+
+// Crude benchmark for compressing random slices of bytes.
+func BenchmarkCompress1KBVerySparse(b *testing.B) { benchmarkCompress(b, 1024, 0.0001) }
+func BenchmarkCompress2KBVerySparse(b *testing.B) { benchmarkCompress(b, 2048, 0.0001) }
+func BenchmarkCompress4KBVerySparse(b *testing.B) { benchmarkCompress(b, 4096, 0.0001) }
+
+func BenchmarkCompress1KBSparse(b *testing.B) { benchmarkCompress(b, 1024, 0.001) }
+func BenchmarkCompress2KBSparse(b *testing.B) { benchmarkCompress(b, 2048, 0.001) }
+func BenchmarkCompress4KBSparse(b *testing.B) { benchmarkCompress(b, 4096, 0.001) }
+
+func BenchmarkCompress1KBDense(b *testing.B) { benchmarkCompress(b, 1024, 0.1) }
+func BenchmarkCompress2KBDense(b *testing.B) { benchmarkCompress(b, 2048, 0.1) }
+func BenchmarkCompress4KBDense(b *testing.B) { benchmarkCompress(b, 4096, 0.1) }
+
+func BenchmarkCompress1KBSaturated(b *testing.B) { benchmarkCompress(b, 1024, 0.5) }
+func BenchmarkCompress2KBSaturated(b *testing.B) { benchmarkCompress(b, 2048, 0.5) }
+func BenchmarkCompress4KBSaturated(b *testing.B) { benchmarkCompress(b, 4096, 0.5) }
+
+func benchmarkCompress(b *testing.B, bytes int, fill float64) {
+ // Generate a random slice of bytes to compress
+ random := rand.NewSource(0) // reproducible and comparable
+
+ data := make([]byte, bytes)
+ bits := int(float64(bytes) * 8 * fill)
+
+ for i := 0; i < bits; i++ {
+ idx := random.Int63() % int64(len(data))
+ bit := uint(random.Int63() % 8)
+ data[idx] |= 1 << bit
+ }
+ // Reset the benchmark and measure compression/decompression
+ b.ResetTimer()
+ b.ReportAllocs()
+ for i := 0; i < b.N; i++ {
+ DecompressBytes(CompressBytes(data), len(data))
+ }
+}