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test: complete BDB parser (handle internal/overflow pages, support all page sizes)

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This aims to complete our test framework BDB parser to reflect
our read-only BDB parser in the wallet codebase. This could be
useful both for making review of #26606 easier and to also possibly
improve our functional tests for the BDB parser by comparing with
an alternative implementation.
This commit is contained in:
Sebastian Falbesoner 2024-05-16 16:17:05 +02:00
parent d94adc7270
commit 01ddd9f646
1 changed files with 95 additions and 36 deletions
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131
test/functional/test_framework/bdb.py
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@ -6,20 +6,18 @@
Utilities for working directly with the wallet's BDB database file
This is specific to the configuration of BDB used in this project:
- pagesize: 4096 bytes
- Outer database contains single subdatabase named 'main'
- btree
- btree leaf pages
- btree internal, leaf and overflow pages
Each key-value pair is two entries in a btree leaf. The first is the key, the one that follows
Each key-value pair is two entries in a btree leaf, which optionally refers to overflow pages
if the data doesn't fit into a single page. The first entry is the key, the one that follows
is the value. And so on. Note that the entry data is itself not in the correct order. Instead
entry offsets are stored in the correct order and those offsets are needed to then retrieve
the data itself.
the data itself. Note that this implementation currently only supports reading databases that
are in the same endianness as the host.
Page format can be found in BDB source code dbinc/db_page.h
This only implements the deserialization of btree metadata pages and normal btree pages. Overflow
pages are not implemented but may be needed in the future if dealing with wallets with large
transactions.
`db_dump -da wallet.dat` is useful to see the data in a wallet.dat BDB file
"""
@ -27,23 +25,36 @@ transactions.
import struct
# Important constants
PAGESIZE = 4096
PAGE_HEADER_SIZE = 26
OUTER_META_PAGE = 0
INNER_META_PAGE = 2
# Page type values
BTREE_INTERNAL = 3
BTREE_LEAF = 5
OVERFLOW_DATA = 7
BTREE_META = 9
# Record type values
RECORD_KEYDATA = 1
RECORD_OVERFLOW_DATA = 3
# Some magic numbers for sanity checking
BTREE_MAGIC = 0x053162
DB_VERSION = 9
SUBDATABASE_NAME = b'main'
# Deserializes a leaf page into a dict.
# Btree internal pages have the same header, for those, return None.
# For the btree leaf pages, deserialize them and put all the data into a dict
def dump_leaf_page(data):
# Deserializes an internal, leaf or overflow page into a dict.
# In addition to the common page header fields, the result contains an 'entries'
# array of dicts with the following fields, depending on the page type:
# internal page [BTREE_INTERNAL]:
# - 'page_num': referenced page number (used to find further pages to process)
# leaf page [BTREE_LEAF]:
# - 'record_type': record type, must be RECORD_KEYDATA or RECORD_OVERFLOW_DATA
# - 'data': binary data (key or value payload), if record type is RECORD_KEYDATA
# - 'page_num': referenced overflow page number, if record type is RECORD_OVERFLOW_DATA
# overflow page [OVERFLOW_DATA]:
# - 'data': binary data (part of key or value payload)
def dump_page(data):
page_info = {}
page_header = data[0:26]
_, pgno, prev_pgno, next_pgno, entries, hf_offset, level, pg_type = struct.unpack('QIIIHHBB', page_header)
@ -56,20 +67,35 @@ def dump_leaf_page(data):
page_info['entry_offsets'] = struct.unpack('{}H'.format(entries), data[26:26 + entries * 2])
page_info['entries'] = []
if pg_type == BTREE_INTERNAL:
# Skip internal pages. These are the internal nodes of the btree and don't contain anything relevant to us
return None
assert pg_type in (BTREE_INTERNAL, BTREE_LEAF, OVERFLOW_DATA)
assert pg_type == BTREE_LEAF, 'A non-btree leaf page has been encountered while dumping leaves'
if pg_type == OVERFLOW_DATA:
assert entries == 1
page_info['entries'].append({'data': data[26:26 + hf_offset]})
return page_info
for i in range(0, entries):
entry = {}
offset = page_info['entry_offsets'][i]
entry = {'offset': offset}
page_data_header = data[offset:offset + 3]
e_len, pg_type = struct.unpack('HB', page_data_header)
entry['len'] = e_len
entry['pg_type'] = pg_type
entry['data'] = data[offset + 3:offset + 3 + e_len]
record_header = data[offset:offset + 3]
offset += 3
e_len, record_type = struct.unpack('HB', record_header)
if pg_type == BTREE_INTERNAL:
assert record_type == RECORD_KEYDATA
internal_record_data = data[offset:offset + 9]
_, page_num, _ = struct.unpack('=BII', internal_record_data)
entry['page_num'] = page_num
elif pg_type == BTREE_LEAF:
assert record_type in (RECORD_KEYDATA, RECORD_OVERFLOW_DATA)
entry['record_type'] = record_type
if record_type == RECORD_KEYDATA:
entry['data'] = data[offset:offset + e_len]
elif record_type == RECORD_OVERFLOW_DATA:
overflow_record_data = data[offset:offset + 9]
_, page_num, _ = struct.unpack('=BII', overflow_record_data)
entry['page_num'] = page_num
page_info['entries'].append(entry)
return page_info
@ -115,16 +141,27 @@ def dump_meta_page(page):
return metadata
# Given the dict from dump_leaf_page, get the key-value pairs and put them into a dict
def extract_kv_pairs(page_data):
def extract_kv_pairs(page_data, pages):
out = {}
last_key = None
for i, entry in enumerate(page_data['entries']):
data = b''
if entry['record_type'] == RECORD_KEYDATA:
data = entry['data']
elif entry['record_type'] == RECORD_OVERFLOW_DATA:
next_page = entry['page_num']
while next_page != 0:
opage = pages[next_page]
opage_info = dump_page(opage)
data += opage_info['entries'][0]['data']
next_page = opage_info['next_pgno']
# By virtue of these all being pairs, even number entries are keys, and odd are values
if i % 2 == 0:
out[entry['data']] = b''
last_key = entry['data']
last_key = data
else:
out[last_key] = entry['data']
out[last_key] = data
return out
# Extract the key-value pairs of the BDB file given in filename
@ -132,20 +169,42 @@ def dump_bdb_kv(filename):
# Read in the BDB file and start deserializing it
pages = []
with open(filename, 'rb') as f:
data = f.read(PAGESIZE)
# Determine pagesize first
data = f.read(PAGE_HEADER_SIZE)
pagesize = struct.unpack('I', data[20:24])[0]
assert pagesize in (512, 1024, 2048, 4096, 8192, 16384, 32768, 65536)
# Read rest of first page
data += f.read(pagesize - PAGE_HEADER_SIZE)
assert len(data) == pagesize
# Read all remaining pages
while len(data) > 0:
pages.append(data)
data = f.read(PAGESIZE)
data = f.read(pagesize)
# Sanity check the meta pages
dump_meta_page(pages[OUTER_META_PAGE])
dump_meta_page(pages[INNER_META_PAGE])
# Sanity check the meta pages, read root page
outer_meta_info = dump_meta_page(pages[OUTER_META_PAGE])
root_page_info = dump_page(pages[outer_meta_info['root']])
assert root_page_info['pg_type'] == BTREE_LEAF
assert len(root_page_info['entries']) == 2
assert root_page_info['entries'][0]['data'] == SUBDATABASE_NAME
assert len(root_page_info['entries'][1]['data']) == 4
inner_meta_page = int.from_bytes(root_page_info['entries'][1]['data'], 'big')
inner_meta_info = dump_meta_page(pages[inner_meta_page])
# Fetch the kv pairs from the leaf pages
# Fetch the kv pairs from the pages
kv = {}
for i in range(3, len(pages)):
info = dump_leaf_page(pages[i])
if info is not None:
info_kv = extract_kv_pairs(info)
pages_to_process = [inner_meta_info['root']]
while len(pages_to_process) > 0:
curr_page_no = pages_to_process.pop()
assert curr_page_no <= outer_meta_info['last_pgno']
info = dump_page(pages[curr_page_no])
assert info['pg_type'] in (BTREE_INTERNAL, BTREE_LEAF)
if info['pg_type'] == BTREE_INTERNAL:
for entry in info['entries']:
pages_to_process.append(entry['page_num'])
elif info['pg_type'] == BTREE_LEAF:
info_kv = extract_kv_pairs(info, pages)
kv = {**kv, **info_kv}
return kv