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author | ethersphere <thesw@rm.eth> | 2018-06-20 20:06:27 +0800 |
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committer | ethersphere <thesw@rm.eth> | 2018-06-22 03:10:31 +0800 |
commit | e187711c6545487d4cac3701f0f506bb536234e2 (patch) | |
tree | d2f6150f70b84b36e49a449082aeda267b4b9046 /swarm/multihash | |
parent | 574378edb50c907b532946a1d4654dbd6701b20a (diff) | |
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swarm: network rewrite merge
Diffstat (limited to 'swarm/multihash')
-rw-r--r-- | swarm/multihash/multihash.go | 92 | ||||
-rw-r--r-- | swarm/multihash/multihash_test.go | 53 |
2 files changed, 145 insertions, 0 deletions
diff --git a/swarm/multihash/multihash.go b/swarm/multihash/multihash.go new file mode 100644 index 000000000..3306e3a6d --- /dev/null +++ b/swarm/multihash/multihash.go @@ -0,0 +1,92 @@ +// Copyright 2018 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 multihash + +import ( + "bytes" + "encoding/binary" + "errors" + "fmt" +) + +const ( + defaultMultihashLength = 32 + defaultMultihashTypeCode = 0x1b +) + +var ( + multihashTypeCode uint8 + MultihashLength = defaultMultihashLength +) + +func init() { + multihashTypeCode = defaultMultihashTypeCode + MultihashLength = defaultMultihashLength +} + +// check if valid swarm multihash +func isSwarmMultihashType(code uint8) bool { + return code == multihashTypeCode +} + +// GetMultihashLength returns the digest length of the provided multihash +// It will fail if the multihash is not a valid swarm mulithash +func GetMultihashLength(data []byte) (int, int, error) { + cursor := 0 + typ, c := binary.Uvarint(data) + if c <= 0 { + return 0, 0, errors.New("unreadable hashtype field") + } + if !isSwarmMultihashType(uint8(typ)) { + return 0, 0, fmt.Errorf("hash code %x is not a swarm hashtype", typ) + } + cursor += c + hashlength, c := binary.Uvarint(data[cursor:]) + if c <= 0 { + return 0, 0, errors.New("unreadable length field") + } + cursor += c + + // we cheekily assume hashlength < maxint + inthashlength := int(hashlength) + if len(data[c:]) < inthashlength { + return 0, 0, errors.New("length mismatch") + } + return inthashlength, cursor, nil +} + +// FromMulithash returns the digest portion of the multihash +// It will fail if the multihash is not a valid swarm multihash +func FromMultihash(data []byte) ([]byte, error) { + hashLength, _, err := GetMultihashLength(data) + if err != nil { + return nil, err + } + return data[len(data)-hashLength:], nil +} + +// ToMulithash wraps the provided digest data with a swarm mulithash header +func ToMultihash(hashData []byte) []byte { + buf := bytes.NewBuffer(nil) + b := make([]byte, 8) + c := binary.PutUvarint(b, uint64(multihashTypeCode)) + buf.Write(b[:c]) + c = binary.PutUvarint(b, uint64(len(hashData))) + buf.Write(b[:c]) + buf.Write(hashData) + return buf.Bytes() +} diff --git a/swarm/multihash/multihash_test.go b/swarm/multihash/multihash_test.go new file mode 100644 index 000000000..85df741dd --- /dev/null +++ b/swarm/multihash/multihash_test.go @@ -0,0 +1,53 @@ +// Copyright 2018 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 multihash + +import ( + "bytes" + "math/rand" + "testing" +) + +// parse multihash, and check that invalid multihashes fail +func TestCheckMultihash(t *testing.T) { + hashbytes := make([]byte, 32) + c, err := rand.Read(hashbytes) + if err != nil { + t.Fatal(err) + } else if c < 32 { + t.Fatal("short read") + } + + expected := ToMultihash(hashbytes) + + l, hl, _ := GetMultihashLength(expected) + if l != 32 { + t.Fatalf("expected length %d, got %d", 32, l) + } else if hl != 2 { + t.Fatalf("expected header length %d, got %d", 2, hl) + } + if _, _, err := GetMultihashLength(expected[1:]); err == nil { + t.Fatal("expected failure on corrupt header") + } + if _, _, err := GetMultihashLength(expected[:len(expected)-2]); err == nil { + t.Fatal("expected failure on short content") + } + dh, _ := FromMultihash(expected) + if !bytes.Equal(dh, hashbytes) { + t.Fatalf("expected content hash %x, got %x", hashbytes, dh) + } +} |