Maybe this will help you parse the varints?
Unfortunately not, that is a different varint thing: https://bitcoin.stackexchange.com/questions/121888/what-is-the-data-format-layout-for-txindex-leveldb-values/121889#121889
Topic: parsing leveldb txindex (Read 596 times)
Unfortunately not, that is a different varint thing: https://bitcoin.stackexchange.com/questions/121888/what-is-the-data-format-layout-for-txindex-leveldb-values/121889#121889
Maybe this will help you parse the varints?
This is what I use in my implementation.
Your code looks like it's reading something else, but not a varint.
I would advise you to test your function on some sample cases for which you know what the varint is supposed to decode to, because generally speaking, C and Python have slightly different semantics that might break ported code.
Code:
def parse_varint_hex(data):
varint_type = hex_to_int(data[0:2])
if varint_type < 0xFD:
return varint_type, 1
elif varint_type == 0xFD:
return hex_to_int(data[2:6]), 3
elif varint_type == 0xFE:
return hex_to_int(data[2:10]), 5
elif varint_type == 0xFF:
return hex_to_int(data[2:18]), 9
def hex_to_int(string):
return int.from_bytes(bytes.fromhex(string), byteorder="little")
varint_type = hex_to_int(data[0:2])
if varint_type < 0xFD:
return varint_type, 1
elif varint_type == 0xFD:
return hex_to_int(data[2:6]), 3
elif varint_type == 0xFE:
return hex_to_int(data[2:10]), 5
elif varint_type == 0xFF:
return hex_to_int(data[2:18]), 9
def hex_to_int(string):
return int.from_bytes(bytes.fromhex(string), byteorder="little")
This is what I use in my implementation.
Your code looks like it's reading something else, but not a varint.
I would advise you to test your function on some sample cases for which you know what the varint is supposed to decode to, because generally speaking, C and Python have slightly different semantics that might break ported code.
I've also opened a related thread at: https://bitcoin.stackexchange.com/questions/121888/what-is-the-data-format-layout-for-txindex-leveldb-values I've made some progress in Python, but I must still have a bug in my code.
I'm trying to parse the LevelDB txindex, i.e. fetch raw transaction data given a transaction hash.
I'm reading a key-value pair from LevelDB with 't' + hash_bytes, and e.g. for transaction 444b7ecbda319e184da1a3d68968e6e0ca9346ddcf7afd0e2b887a7949128805 the key's value is
80 58 8f c4 c8 66 80 9b 24
Now, if I'm reading the bitcoin source correctly, this should be three varints:
If I'm correctly decoding them, the 3 values are: 216 34694374 20004 -- which looks good. However, the data at offset 34694374 + 20004 in file 216 is unexpected:
version: 4293214589
inCount: 93952409796607
It looks like either I'm decoding the varints the wrong way or I'm calculating the file offset wrongly?
The varint read+decode code is mostly a direct port from C:
I'm reading a key-value pair from LevelDB with 't' + hash_bytes, and e.g. for transaction 444b7ecbda319e184da1a3d68968e6e0ca9346ddcf7afd0e2b887a7949128805 the key's value is
80 58 8f c4 c8 66 80 9b 24
Now, if I'm reading the bitcoin source correctly, this should be three varints:
- nFile
- nPos
- nTxOffset
If I'm correctly decoding them, the 3 values are: 216 34694374 20004 -- which looks good. However, the data at offset 34694374 + 20004 in file 216 is unexpected:
version: 4293214589
inCount: 93952409796607
It looks like either I'm decoding the varints the wrong way or I'm calculating the file offset wrongly?
The varint read+decode code is mostly a direct port from C:
Code:
def varint(s):
n = 0
while True:
ch = read1(s)
n = (n << 7) | (ch & 0x7f)
if ch & 0x80:
n += 1
else:
return n
n = 0
while True:
ch = read1(s)
n = (n << 7) | (ch & 0x7f)
if ch & 0x80:
n += 1
else:
return n
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