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authorFelix Lange <fjl@twurst.com>2015-07-01 08:09:02 +0800
committerFelix Lange <fjl@twurst.com>2015-09-11 01:41:51 +0800
commitbc17dba8fba0f3007398f231f07916a95ed963ac (patch)
tree3012f4338d04b20d4399c31b09c7e20766075ad8 /rlp/raw.go
parentac32f52ca6e620556e7a875f0d52ddef72215532 (diff)
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rlp: add Split functions
These functions allow destructuring of raw rlp-encoded bytes without the overhead of reflection or copying.
Diffstat (limited to 'rlp/raw.go')
-rw-r--r--rlp/raw.go140
1 files changed, 140 insertions, 0 deletions
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
+}