Introduce ParseHash

txpool/packets.go

@@ -0,0 +1,48 @@
+/*
+   Copyright 2021 Erigon contributors
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package txpool
+
+import "fmt"
+
+const ParseHashErrorPrefix = "parse hash payload"
+
+// ParseHash extracts the next hash from the RLP encoding (payload) from a given position
+// it appends the hash to the given slice, reusing the space if there is enough capacity
+// The first returned value is the slice where hash is appended to.
+// The second returned value is the new position in the RLP payload after the extraction
+// of the hash.
+func ParseHash(payload []byte, pos int, hashbuf []byte) ([]byte, int, error) {
+	dataPos, dataLen, list, err := prefix(payload, pos)
+	if err != nil {
+		return nil, 0, fmt.Errorf("%s: to len: %w", ParseHashErrorPrefix, err)
+	}
+	if list {
+		return nil, 0, fmt.Errorf("%s: hash must be a string, not list", ParseHashErrorPrefix)
+	}
+	if dataLen != 32 {
+		return nil, 0, fmt.Errorf("%s: hash must be 32 bytes long", ParseHashErrorPrefix)
+	}
+	var hash []byte
+	if total := len(hashbuf) + 32; cap(hashbuf) >= total {
+		hash = hashbuf[:32] // Reuse the space in pkbuf, is it has enough capacity
+	} else {
+		hash = make([]byte, total)
+		copy(hash, hashbuf)
+	}
+	copy(hash, payload[dataPos:dataPos+dataLen])
+	return hash, dataPos + dataLen, nil
+}