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Added witness compression and decompression and length tests

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vbuterin committed Mar 24, 2018
1 parent a536495 commit 67b281d5b0738852d9bac4031d48412b02c131d2
@@ -19,19 +19,24 @@ def shuffle_in_place(x):
for _ in range(3):
t = Trie(EphemDB(), b'')
total_long_length, total_short_length = 0, 0
for i, (k, v) in enumerate(shuffle_in_place(kvpairs)):
#print(t.to_dict())
t.update(k, v)
assert t.get(k) == v
if not i % 50:
if not i % 250:
t.to_dict()
b = t.get_long_format_branch(k)
print("Length of long-format branch at %d nodes: %d" % (i, len(rlp.encode(b))))
c = compress(b)
b2 = expand(c)
print("Length of compressed witness: %d" % len(rlp.encode(c)))
assert sorted(b2) == sorted(b), "Witness compression fails"
if not i % 250:
t.to_dict()
b = t.get_long_format_branch(k)
c = compress(b)
b2 = expand(c)
total_long_length += len(rlp.encode(b))
total_short_length += len(rlp.encode(c))
assert sorted(b2) == sorted(b), "Witness compression fails"
if i % 50 == 49:
print("Avg length of long-format branch at %d nodes: %d" % (i-24, total_long_length // 50))
print("Avg length of compressed witness: %d" % (total_short_length // 50))
total_long_length = 0
total_short_length = 0
print('Added 1000 values, doing checks')
assert r1 is None or t.root == r1
r1 = t.root
@@ -14,7 +14,7 @@ def delete(self, k):
del self.kv[k]
zerohashes = [b'\x00' * 32]
for i in range(256):
for i in range(255):
zerohashes.insert(0, sha3(zerohashes[0] + zerohashes[0]))
def new_tree(db):
@@ -101,3 +101,25 @@ def verify_proof(proof, root, key, value):
path >>= 1
v = newv
return root == v
def compress_proof(proof):
bits = bytearray(32)
oproof = b''
for i, p in enumerate(proof):
if p == zerohashes[i]:
bits[i // 8] ^= 1 << i % 8
else:
oproof += p
return bytes(bits) + oproof
def decompress_proof(oproof):
proof = []
bits = bytearray(oproof[:32])
pos = 32
for i in range(256):
if bits[i // 8] & (1 << (i % 8)):
proof.append(zerohashes[i])
else:
proof.append(oproof[pos: pos + 32])
pos += 32
return proof
@@ -1,18 +1,27 @@
from new_bintrie import EphemDB, new_tree, get, update, make_merkle_proof, verify_proof
from new_bintrie import EphemDB, new_tree, get, update, make_merkle_proof, verify_proof, compress_proof, decompress_proof
import random
from ethereum.utils import sha3
KEYS = 500
db = EphemDB()
t = new_tree(db)
for i in range(500):
for i in range(KEYS):
t = update(db, t, sha3(str(i)), sha3(str(i**3)))
for i in range(500):
print('%d elements added' % KEYS)
for i in range(KEYS):
assert get(db, t, sha3(str(i))) == sha3(str(i**3))
for i in range(501, 1000):
print('Get requests for present elements successful')
for i in range(KEYS + 1, KEYS * 2):
assert get(db, t, sha3(str(i))) == b'\x00' * 32
print('Get requests for absent elements successful')
for i in range(1000):
TL = 0
for i in range(KEYS * 2):
key = sha3(str(i))
value = sha3(str(i ** 3)) if i < 500 else b'\x00' * 32
value = sha3(str(i ** 3)) if i < KEYS else b'\x00' * 32
proof = make_merkle_proof(db, t, key)
assert verify_proof(proof, t, key, value)
assert decompress_proof(compress_proof(proof)) == proof
TL += len(compress_proof(proof))
print('Average total length at %d keys: %d, %d including key' % (KEYS, TL // KEYS // 2, TL // KEYS // 2 + 32))

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