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# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
# For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
"""
Functions to manipulate packed binary representations of number sets.
To save space, coverage stores sets of line numbers in SQLite using a packed
binary representation called a numbits. A numbits is a set of positive
integers.
A numbits is stored as a blob in the database. The exact meaning of the bytes
in the blobs should be considered an implementation detail that might change in
the future. Use these functions to work with those binary blobs of data.
"""
from coverage import env
from coverage.backward import byte_to_int, bytes_to_ints, binary_bytes, zip_longest
from coverage.misc import contract, new_contract
if env.PY3:
def _to_blob(b):
"""Convert a bytestring into a type SQLite will accept for a blob."""
return b
new_contract('blob', lambda v: isinstance(v, bytes))
else:
def _to_blob(b):
"""Convert a bytestring into a type SQLite will accept for a blob."""
return buffer(b) # pylint: disable=undefined-variable
new_contract('blob', lambda v: isinstance(v, buffer)) # pylint: disable=undefined-variable
@contract(nums='Iterable', returns='blob')
def nums_to_numbits(nums):
"""Convert `nums` into a numbits.
Arguments:
nums (a reusable iterable of integers): the line numbers to store.
Returns:
A binary blob.
"""
try:
nbytes = max(nums) // 8 + 1
except ValueError:
# nums was empty.
return _to_blob(b'')
b = bytearray(nbytes)
for num in nums:
b[num//8] |= 1 << num % 8
return _to_blob(bytes(b))
@contract(numbits='blob', returns='list[int]')
def numbits_to_nums(numbits):
"""Convert a numbits into a list of numbers.
Arguments:
numbits (a binary blob): the packed number set.
Returns:
A list of integers.
"""
nums = []
for byte_i, byte in enumerate(bytes_to_ints(numbits)):
for bit_i in range(8):
if (byte & (1 << bit_i)):
nums.append(byte_i * 8 + bit_i)
return nums
@contract(numbits1='blob', numbits2='blob', returns='blob')
def numbits_union(numbits1, numbits2):
"""Compute the union of two numbits.
Arguments:
numbits1, numbits2: packed number sets.
Returns:
A new numbits, the union of the two number sets.
"""
byte_pairs = zip_longest(bytes_to_ints(numbits1), bytes_to_ints(numbits2), fillvalue=0)
return _to_blob(binary_bytes(b1 | b2 for b1, b2 in byte_pairs))
@contract(numbits1='blob', numbits2='blob', returns='blob')
def numbits_intersection(numbits1, numbits2):
"""Compute the intersection of two numbits.
Arguments:
numbits1, numbits2: packed number sets.
Returns:
A new numbits, the intersection of the two number sets.
"""
byte_pairs = zip_longest(bytes_to_ints(numbits1), bytes_to_ints(numbits2), fillvalue=0)
intersection_bytes = binary_bytes(b1 & b2 for b1, b2 in byte_pairs)
return _to_blob(intersection_bytes.rstrip(b'\0'))
@contract(numbits1='blob', numbits2='blob', returns='bool')
def numbits_any_intersection(numbits1, numbits2):
"""Is there any number that appears in both numbits?
Determine whether two number sets have a non-empty intersection. This is
faster than computing the intersection.
Arguments:
numbits1, numbits2: packed number sets.
Returns:
A boolean, true if there is any number in both of the number sets.
"""
byte_pairs = zip_longest(bytes_to_ints(numbits1), bytes_to_ints(numbits2), fillvalue=0)
return any(b1 & b2 for b1, b2 in byte_pairs)
@contract(num='int', numbits='blob', returns='bool')
def num_in_numbits(num, numbits):
"""Does the integer `num` appear in `numbits`?
Arguments:
num (integer)
numbits (binary blob)
Returns:
A boolean, true if `num` is a member of `numbits`.
"""
nbyte, nbit = divmod(num, 8)
if nbyte >= len(numbits):
return False
return bool(byte_to_int(numbits[nbyte]) & (1 << nbit))
def register_sqlite_functions(connection):
"""
Define numbits functions in a SQLite connection.
This defines these functions for use in SQLite statements:
* :func:`numbits_union`
* :func:`numbits_intersection`
* :func:`numbits_any_intersection`
* :func:`num_in_numbits`
`connection` is a :class:`sqlite3.Connection <python:sqlite3.Connection>`
object. After creating the connection, pass it to this function to
register the numbits functions. Then you can use numbits functions in your
queries::
import sqlite3
from coverage.numbits import register_sqlite_functions
conn = sqlite3.connect('example.db')
register_sqlite_functions(conn)
c = conn.cursor()
c.execute(
"select lb.file_id, lb.context_id from line_bits lb"
"where num_in_numbits(?, lb.numbits)",
(interesting_line_number,)
)
"""
connection.create_function("numbits_union", 2, numbits_union)
connection.create_function("numbits_intersection", 2, numbits_intersection)
connection.create_function("numbits_any_intersection", 2, numbits_any_intersection)
connection.create_function("num_in_numbits", 2, num_in_numbits)
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