rlp: add Split functions

These functions allow destructuring of raw rlp-encoded bytes
without the overhead of reflection or copying.

3 files changed, 337 insertions, 1 deletions

diff --git a/rlp/decode_test.go b/rlp/decode_test.go
index d6b0611dd..ce4f9ecc8 100644
--- a/rlp/decode_test.go
+++ b/rlp/decode_test.go
@@ -24,6 +24,7 @@ import (
 	"io"
 	"math/big"
 	"reflect"
+	"strings"
 	"testing"
 )
 
@@ -725,7 +726,7 @@ func encodeTestSlice(n uint) []byte {
 }
 
 func unhex(str string) []byte {
-	b, err := hex.DecodeString(str)
+	b, err := hex.DecodeString(strings.Replace(str, " ", "", -1))
 	if err != nil {
 		panic(fmt.Sprintf("invalid hex string: %q", str))
 	}
diff --git a/rlp/raw.go b/rlp/raw.go
new file mode 100644
index 000000000..e93c4df40
--- /dev/null
+++ b/rlp/raw.go
@@ -0,0 +1,140 @@
+// Copyright 2015 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 rlp
+
+import "io"
+
+// Split returns the content of first RLP value and any
+// bytes after the value as subslices of b.
+func Split(b []byte) (k Kind, content, rest []byte, err error) {
+	k, ts, cs, err := readKind(b)
+	if err != nil {
+		return 0, nil, b, err
+	}
+	return k, b[ts : ts+cs], b[ts+cs:], nil
+}
+
+// SplitString splits b into the content of an RLP string
+// and any remaining bytes after the string.
+func SplitString(b []byte) (content, rest []byte, err error) {
+	k, content, rest, err := Split(b)
+	if err != nil {
+		return nil, b, err
+	}
+	if k == List {
+		return nil, b, ErrExpectedString
+	}
+	return content, rest, nil
+}
+
+// SplitList splits b into the content of a list and any remaining
+// bytes after the list.
+func SplitList(b []byte) (content, rest []byte, err error) {
+	k, content, rest, err := Split(b)
+	if err != nil {
+		return nil, b, err
+	}
+	if k != List {
+		return nil, b, ErrExpectedList
+	}
+	return content, rest, nil
+}
+
+// CountValues counts the number of encoded values in b.
+func CountValues(b []byte) (int, error) {
+	i := 0
+	for ; len(b) > 0; i++ {
+		_, tagsize, size, err := readKind(b)
+		if err != nil {
+			return 0, err
+		}
+		b = b[tagsize+size:]
+	}
+	return i, nil
+}
+
+func readKind(buf []byte) (k Kind, tagsize, contentsize uint64, err error) {
+	if len(buf) == 0 {
+		return 0, 0, 0, io.ErrUnexpectedEOF
+	}
+	b := buf[0]
+	switch {
+	case b < 0x80:
+		k = Byte
+		tagsize = 0
+		contentsize = 1
+	case b < 0xB8:
+		k = String
+		tagsize = 1
+		contentsize = uint64(b - 0x80)
+		// Reject strings that should've been single bytes.
+		if contentsize == 1 && buf[1] < 128 {
+			return 0, 0, 0, ErrCanonSize
+		}
+	case b < 0xC0:
+		k = String
+		tagsize = uint64(b-0xB7) + 1
+		contentsize, err = readSize(buf[1:], b-0xB7)
+	case b < 0xF8:
+		k = List
+		tagsize = 1
+		contentsize = uint64(b - 0xC0)
+	default:
+		k = List
+		tagsize = uint64(b-0xF7) + 1
+		contentsize, err = readSize(buf[1:], b-0xF7)
+	}
+	if err != nil {
+		return 0, 0, 0, err
+	}
+	// Reject values larger than the input slice.
+	if contentsize > uint64(len(buf))-tagsize {
+		return 0, 0, 0, ErrValueTooLarge
+	}
+	return k, tagsize, contentsize, err
+}
+
+func readSize(b []byte, slen byte) (uint64, error) {
+	if int(slen) > len(b) {
+		return 0, io.ErrUnexpectedEOF
+	}
+	var s uint64
+	switch slen {
+	case 1:
+		s = uint64(b[0])
+	case 2:
+		s = uint64(b[0])<<8 | uint64(b[1])
+	case 3:
+		s = uint64(b[0])<<16 | uint64(b[1])<<8 | uint64(b[2])
+	case 4:
+		s = uint64(b[0])<<24 | uint64(b[1])<<16 | uint64(b[2])<<8 | uint64(b[3])
+	case 5:
+		s = uint64(b[0])<<32 | uint64(b[1])<<24 | uint64(b[2])<<16 | uint64(b[3])<<8 | uint64(b[4])
+	case 6:
+		s = uint64(b[0])<<40 | uint64(b[1])<<32 | uint64(b[2])<<24 | uint64(b[3])<<16 | uint64(b[4])<<8 | uint64(b[5])
+	case 7:
+		s = uint64(b[0])<<48 | uint64(b[1])<<40 | uint64(b[2])<<32 | uint64(b[3])<<24 | uint64(b[4])<<16 | uint64(b[5])<<8 | uint64(b[6])
+	case 8:
+		s = uint64(b[0])<<56 | uint64(b[1])<<48 | uint64(b[2])<<40 | uint64(b[3])<<32 | uint64(b[4])<<24 | uint64(b[5])<<16 | uint64(b[6])<<8 | uint64(b[7])
+	}
+	// Reject sizes < 56 (shouldn't have separate size) and sizes with
+	// leading zero bytes.
+	if s < 56 || b[0] == 0 {
+		return 0, ErrCanonSize
+	}
+	return s, nil
+}
diff --git a/rlp/raw_test.go b/rlp/raw_test.go
new file mode 100644
index 000000000..7d3ca13af
--- /dev/null
+++ b/rlp/raw_test.go
@@ -0,0 +1,195 @@
+// Copyright 2015 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 rlp
+
+import (
+	"bytes"
+	"io"
+	"reflect"
+	"testing"
+)
+
+func TestCountValues(t *testing.T) {
+	tests := []struct {
+		input string // note: spaces in input are stripped by unhex
+		count int
+		err   error
+	}{
+		// simple cases
+		{"", 0, nil},
+		{"00", 1, nil},
+		{"80", 1, nil},
+		{"C0", 1, nil},
+		{"01 02 03", 3, nil},
+		{"01 C406070809 02", 3, nil},
+		{"820101 820202 8403030303 04", 4, nil},
+
+		// size errors
+		{"8142", 0, ErrCanonSize},
+		{"01 01 8142", 0, ErrCanonSize},
+		{"02 84020202", 0, ErrValueTooLarge},
+
+		{
+			input: "A12000BF49F440A1CD0527E4D06E2765654C0F56452257516D793A9B8D604DCFDF2AB853F851808D10000000000000000000000000A056E81F171BCC55A6FF8345E692C0F86E5B48E01B996CADC001622FB5E363B421A0C5D2460186F7233C927E7DB2DCC703C0E500B653CA82273B7BFAD8045D85A470",
+			count: 2,
+		},
+	}
+	for i, test := range tests {
+		count, err := CountValues(unhex(test.input))
+		if count != test.count {
+			t.Errorf("test %d: count mismatch, got %d want %d\ninput: %s", i, count, test.count, test.input)
+		}
+		if !reflect.DeepEqual(err, test.err) {
+			t.Errorf("test %d: err mismatch, got %q want %q\ninput: %s", i, err, test.err, test.input)
+		}
+	}
+}
+
+func TestSplitTypes(t *testing.T) {
+	if _, _, err := SplitString(unhex("C100")); err != ErrExpectedString {
+		t.Error("SplitString returned %q, want %q", err, ErrExpectedString)
+	}
+	if _, _, err := SplitList(unhex("01")); err != ErrExpectedList {
+		t.Error("SplitString returned %q, want %q", err, ErrExpectedList)
+	}
+	if _, _, err := SplitList(unhex("81FF")); err != ErrExpectedList {
+		t.Error("SplitString returned %q, want %q", err, ErrExpectedList)
+	}
+}
+
+func TestSplit(t *testing.T) {
+	tests := []struct {
+		input     string
+		kind      Kind
+		val, rest string
+		err       error
+	}{
+		{input: "01FFFF", kind: Byte, val: "01", rest: "FFFF"},
+		{input: "80FFFF", kind: String, val: "", rest: "FFFF"},
+		{input: "C3010203", kind: List, val: "010203"},
+
+		// errors
+		{input: "", err: io.ErrUnexpectedEOF},
+
+		{input: "8141", err: ErrCanonSize, rest: "8141"},
+		{input: "B800", err: ErrCanonSize, rest: "B800"},
+		{input: "B802FFFF", err: ErrCanonSize, rest: "B802FFFF"},
+		{input: "B90000", err: ErrCanonSize, rest: "B90000"},
+		{input: "B90055", err: ErrCanonSize, rest: "B90055"},
+		{input: "BA0002FFFF", err: ErrCanonSize, rest: "BA0002FFFF"},
+		{input: "F800", err: ErrCanonSize, rest: "F800"},
+		{input: "F90000", err: ErrCanonSize, rest: "F90000"},
+		{input: "F90055", err: ErrCanonSize, rest: "F90055"},
+		{input: "FA0002FFFF", err: ErrCanonSize, rest: "FA0002FFFF"},
+
+		{input: "8501010101", err: ErrValueTooLarge, rest: "8501010101"},
+		{input: "C60607080902", err: ErrValueTooLarge, rest: "C60607080902"},
+
+		// size check overflow
+		{input: "BFFFFFFFFFFFFFFFFF", err: ErrValueTooLarge, rest: "BFFFFFFFFFFFFFFFFF"},
+		{input: "FFFFFFFFFFFFFFFFFF", err: ErrValueTooLarge, rest: "FFFFFFFFFFFFFFFFFF"},
+
+		{
+			input: "B838FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+			err:   ErrValueTooLarge,
+			rest:  "B838FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+		},
+		{
+			input: "F838FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+			err:   ErrValueTooLarge,
+			rest:  "F838FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+		},
+
+		// a few bigger values, just for kicks
+		{
+			input: "F839FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+			kind:  List,
+			val:   "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+			rest:  "",
+		},
+		{
+			input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
+			kind:  List,
+			val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
+			rest:  "",
+		},
+		{
+			input: "F877A12000BF49F440A1CD0527E4D06E2765654C0F56452257516D793A9B8D604DCFDF2AB853F851808D10000000000000000000000000A056E81F171BCC55A6FF8345E692C0F86E5B48E01B996CADC001622FB5E363B421A0C5D2460186F7233C927E7DB2DCC703C0E500B653CA82273B7BFAD8045D85A470",
+			kind:  List,
+			val:   "A12000BF49F440A1CD0527E4D06E2765654C0F56452257516D793A9B8D604DCFDF2AB853F851808D10000000000000000000000000A056E81F171BCC55A6FF8345E692C0F86E5B48E01B996CADC001622FB5E363B421A0C5D2460186F7233C927E7DB2DCC703C0E500B653CA82273B7BFAD8045D85A470",
+			rest:  "",
+		},
+	}
+
+	for i, test := range tests {
+		kind, val, rest, err := Split(unhex(test.input))
+		if kind != test.kind {
+			t.Errorf("test %d: kind mismatch: got %v, want %v", i, kind, test.kind)
+		}
+		if !bytes.Equal(val, unhex(test.val)) {
+			t.Errorf("test %d: val mismatch: got %x, want %s", i, val, test.val)
+		}
+		if !bytes.Equal(rest, unhex(test.rest)) {
+			t.Errorf("test %d: rest mismatch: got %x, want %s", i, rest, test.rest)
+		}
+		if err != test.err {
+			t.Errorf("test %d: error mismatch: got %q, want %q", i, err, test.err)
+		}
+	}
+}
+
+func TestReadSize(t *testing.T) {
+	tests := []struct {
+		input string
+		slen  byte
+		size  uint64
+		err   error
+	}{
+		{input: "", slen: 1, err: io.ErrUnexpectedEOF},
+		{input: "FF", slen: 2, err: io.ErrUnexpectedEOF},
+		{input: "00", slen: 1, err: ErrCanonSize},
+		{input: "36", slen: 1, err: ErrCanonSize},
+		{input: "37", slen: 1, err: ErrCanonSize},
+		{input: "38", slen: 1, size: 0x38},
+		{input: "FF", slen: 1, size: 0xFF},
+		{input: "FFFF", slen: 2, size: 0xFFFF},
+		{input: "FFFFFF", slen: 3, size: 0xFFFFFF},
+		{input: "FFFFFFFF", slen: 4, size: 0xFFFFFFFF},
+		{input: "FFFFFFFFFF", slen: 5, size: 0xFFFFFFFFFF},
+		{input: "FFFFFFFFFFFF", slen: 6, size: 0xFFFFFFFFFFFF},
+		{input: "FFFFFFFFFFFFFF", slen: 7, size: 0xFFFFFFFFFFFFFF},
+		{input: "FFFFFFFFFFFFFFFF", slen: 8, size: 0xFFFFFFFFFFFFFFFF},
+		{input: "0102", slen: 2, size: 0x0102},
+		{input: "010203", slen: 3, size: 0x010203},
+		{input: "01020304", slen: 4, size: 0x01020304},
+		{input: "0102030405", slen: 5, size: 0x0102030405},
+		{input: "010203040506", slen: 6, size: 0x010203040506},
+		{input: "01020304050607", slen: 7, size: 0x01020304050607},
+		{input: "0102030405060708", slen: 8, size: 0x0102030405060708},
+	}
+
+	for _, test := range tests {
+		size, err := readSize(unhex(test.input), test.slen)
+		if err != test.err {
+			t.Errorf("readSize(%s, %d): error mismatch: got %q, want %q", test.input, test.slen, err, test.err)
+			continue
+		}
+		if size != test.size {
+			t.Errorf("readSize(%s, %d): size mismatch: got %#x, want %#x", test.input, test.slen, size, test.size)
+		}
+	}
+}