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Fix tree hash padding #35

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merged 1 commit into from
Feb 5, 2019
Merged

Fix tree hash padding #35

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7 changes: 5 additions & 2 deletions ssz/hash.py
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Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,6 @@ def merkle_hash(input_items: Sequence[Any]) -> Hash32:

# Store length of list (to compensate for non-bijectiveness of padding)
data_length = len(input_items).to_bytes(32, "little")

if len(input_items) == 0:
# Handle empty list case
chunks = (b'\x00' * SSZ_CHUNK_SIZE,)
Expand All @@ -40,10 +39,14 @@ def merkle_hash(input_items: Sequence[Any]) -> Hash32:
items_per_chunk = SSZ_CHUNK_SIZE // len(input_items[0])

# Build a list of chunks based on the number of items in the chunk
chunks = tuple(
chunks_unpadded = (
b''.join(input_items[i:i + items_per_chunk])
for i in range(0, len(input_items), items_per_chunk)
)
chunks = tuple(
chunk.ljust(SSZ_CHUNK_SIZE, b"\x00")
for chunk in chunks_unpadded
)
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My instinct tells me it's faster in one for loop:

@to_tuple
def get_chunkz_new(input_items, items_per_chunk):
    for i in range(0, len(input_items), items_per_chunk):
        yield b''.join(input_items[i:i + items_per_chunk]).ljust(SSZ_CHUNK_SIZE, b"\x00")

(Although maybe not much performance improvement difference.)

else:
# Leave large items alone
chunks = input_items
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10 changes: 5 additions & 5 deletions tests/tree_hash/test_merkle_hash.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,26 +16,26 @@
),
(
(b'\x01',),
b'\x01' + int(1).to_bytes(32, "little"),
b'\x01' + b'\x00' * 127 + int(1).to_bytes(32, "little"),
),
(
(b'\x01', b'\x01', b'\x01',),
b'\x01\x01\x01' + int(3).to_bytes(32, "little"),
b'\x01\x01\x01' + b'\x00' * 125 + int(3).to_bytes(32, "little"),
),
# two items in one chunk
(
(b'\x55' * 64, b'\x66' * 64, b'\x77' * 64,),
(
hash_eth2(b'\x55' * 64 + b'\x66' * 64 + b'\x77' * 64) +
hash_eth2(b'\x55' * 64 + b'\x66' * 64 + b'\x77' * 64 + b'\x00' * 64) +
int(3).to_bytes(32, "little")
),
),
(
(b'\x55' * 96, b'\x66' * 96, b'\x77' * 96, b'\x88' * 96),
(
hash_eth2((
hash_eth2(b'\x55' * 96 + b'\x66' * 96) +
hash_eth2(b'\x77' * 96 + b'\x88' * 96)
hash_eth2(b'\x55' * 96 + b'\x00' * 32 + b'\x66' * 96 + b'\x00' * 32) +
hash_eth2(b'\x77' * 96 + b'\x00' * 32 + b'\x88' * 96 + b'\x00' * 32)
)) +
int(4).to_bytes(32, "little")
),
Expand Down