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https://github.com/theupdateframework/python-tuf
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Move find_bin_for_hash() to repository_lib
Move repository_tool._find_bin_for_hash() and helper functions it uses to non-protected functions in repository_lib. _find_bin_for_hash() becomes find_bin_for_target_hash() These functions will be useful to adopters using the WIP low-level API for updating metadata files (see #1048) Signed-off-by: Joshua Lock <jlock@vmware.com>
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Joshua Lock
parent
b18eb34830
commit
ed45fb24c2
2 changed files with 113 additions and 88 deletions
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@ -980,6 +980,114 @@ def get_metadata_versioninfo(rolename, repository_name):
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def create_bin_name(low, high, prefix_len):
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"""
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<Purpose>
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Create a string name of a delegated hash bin, where name will be a range of
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zero-padded (up to prefix_len) strings i.e. for low=00, high=07,
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prefix_len=3 the returned name would be '000-007'.
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<Arguments>
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low:
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The low end of the prefix range to be binned
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high:
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The high end of the prefix range to be binned
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prefix_len:
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The length of the prefix range components
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<Returns>
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A string bin name, with each end of the range zero-padded up to prefix_len
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"""
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if low == high:
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return "{low:0{len}x}".format(low=low, len=prefix_len)
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return "{low:0{len}x}-{high:0{len}x}".format(low=low, high=high,
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len=prefix_len)
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def get_bin_numbers(number_of_bins):
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"""
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<Purpose>
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Given the desired number of bins (number_of_bins) calculate the prefix
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length (prefix_length), total number of prefixes (prefix_count) and the
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number of prefixes to be stored in each bin (bin_size).
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Example: number_of_bins = 32
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prefix_length = 2
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prefix_count = 256
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bin_size = 8
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That is, each of the 32 hashed bins are responsible for 8 hash prefixes,
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i.e. 00-07, 08-0f, ..., f8-ff.
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<Arguments>
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number_of_bins:
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The number of hashed bins in use
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<Returns>
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A tuple of three values:
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1. prefix_length: the length of each prefix
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2. prefix_count: the total number of prefixes in use
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3. bin_size: the number of hash prefixes to be stored in each bin
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"""
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# Convert 'number_of_bins' to hexadecimal and determine the number of
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# hexadecimal digits needed by each hash prefix
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prefix_length = len("{:x}".format(number_of_bins - 1))
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# Calculate the total number of hash prefixes (e.g., 000 - FFF total values)
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prefix_count = 16 ** prefix_length
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# Determine how many prefixes to assign to each bin
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bin_size = prefix_count // number_of_bins
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# For simplicity, ensure that 'prefix_count' (16 ^ n) can be evenly
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# distributed over 'number_of_bins' (must be 2 ^ n). Each bin will contain
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# (prefix_count / number_of_bins) hash prefixes.
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if prefix_count % number_of_bins != 0:
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# Note: x % y != 0 does not guarantee that y is not a power of 2 for
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# arbitrary x and y values. However, due to the relationship between
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# number_of_bins and prefix_count, it is true for them.
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raise securesystemslib.exceptions.Error('The "number_of_bins" argument'
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' must be a power of 2.')
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return prefix_length, prefix_count, bin_size
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def find_bin_for_target_hash(target_hash, number_of_bins):
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"""
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<Purpose>
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For a given hashed filename, target_hash, calculate the name of a hashed bin
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into which this file would be delegated given number_of_bins bins are in
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use.
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<Arguments>
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target_hash:
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The hash of the target file's path
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number_of_bins:
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The number of hashed_bins in use
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<Returns>
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The name of the hashed bin target_hash would be binned into
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"""
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prefix_length, _, bin_size = get_bin_numbers(number_of_bins)
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prefix = int(target_hash[:prefix_length], 16)
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low = prefix - (prefix % bin_size)
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high = (low + bin_size - 1)
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return create_bin_name(low, high, prefix_length)
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def get_target_hash(target_filepath):
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"""
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<Purpose>
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@ -1,3 +1,4 @@
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#!/usr/bin/env python
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# Copyright 2013 - 2017, New York University and the TUF contributors
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@ -2529,7 +2530,7 @@ def delegate_hashed_bins(self, list_of_targets, keys_of_hashed_bins,
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securesystemslib.formats.ANYKEYLIST_SCHEMA.check_match(keys_of_hashed_bins)
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tuf.formats.NUMBINS_SCHEMA.check_match(number_of_bins)
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prefix_length, prefix_count, bin_size = _get_bin_numbers(number_of_bins)
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prefix_length, prefix_count, bin_size = repo_lib.get_bin_numbers(number_of_bins)
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logger.info('Creating hashed bin delegations.\n' +
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repr(len(list_of_targets)) + ' total targets.\n' +
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@ -2543,7 +2544,7 @@ def delegate_hashed_bins(self, list_of_targets, keys_of_hashed_bins,
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ordered_roles = []
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for idx in range(0, prefix_count, bin_size):
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high = idx + bin_size - 1
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name = _create_bin_name(idx, high, prefix_length)
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name = repo_lib.create_bin_name(idx, high, prefix_length)
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if bin_size == 1:
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target_hash_prefixes = [name]
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else:
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@ -2675,7 +2676,7 @@ def add_target_to_bin(self, target_filepath, number_of_bins=DEFAULT_NUM_BINS,
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# TODO: check target_filepath is sane
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path_hash = repo_lib.get_target_hash(target_filepath)
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bin_name = _find_bin_for_hash(path_hash, number_of_bins)
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bin_name = repo_lib.find_bin_for_target_hash(path_hash, number_of_bins)
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# Ensure the Targets object has delegated to hashed bins
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if not self._delegated_roles.get(bin_name, None):
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@ -2737,7 +2738,7 @@ def remove_target_from_bin(self, target_filepath,
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# TODO: check target_filepath is sane?
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path_hash = repo_lib.get_target_hash(target_filepath)
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bin_name = _find_bin_for_hash(path_hash, number_of_bins)
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bin_name = repo_lib.find_bin_for_target_hash(path_hash, number_of_bins)
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# Ensure the Targets object has delegated to hashed bins
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if not self._delegated_roles.get(bin_name, None):
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@ -2839,90 +2840,6 @@ def _keys_to_keydict(keys):
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def _create_bin_name(low, high, prefix_len):
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"""
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<Purpose>
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Create a string name of a delegated hash bin, where name will be a range of
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zero-padded (up to prefix_len) strings i.e. for low=00, high=07,
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prefix_len=3 the returned name would be '000-007'.
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"""
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if low == high:
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return "{low:0{len}x}".format(low=low, len=prefix_len)
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return "{low:0{len}x}-{high:0{len}x}".format(low=low, high=high,
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len=prefix_len)
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def _get_bin_numbers(number_of_bins):
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"""
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Given the desired number of bins (number_of_bins) calculate the prefix length
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(prefix_length), total number of prefixes (prefix_count) and the number of
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prefixes to be stored in each bin (bin_size).
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Example: number_of_bins = 32
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prefix_length = 2
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prefix_count = 256
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bin_size = 8
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That is, each of the 32 hashed bins are responsible for 8 hash prefixes, i.e.
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00-07, 08-0f, ..., f8-ff.
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"""
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# Convert 'number_of_bins' to hexadecimal and determine the number of
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# hexadecimal digits needed by each hash prefix
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prefix_length = len("{:x}".format(number_of_bins - 1))
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# Calculate the total number of hash prefixes (e.g., 000 - FFF total values)
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prefix_count = 16 ** prefix_length
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# Determine how many prefixes to assign to each bin
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bin_size = prefix_count // number_of_bins
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# For simplicity, ensure that 'prefix_count' (16 ^ n) can be evenly
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# distributed over 'number_of_bins' (must be 2 ^ n). Each bin will contain
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# (prefix_count / number_of_bins) hash prefixes.
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if prefix_count % number_of_bins != 0:
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# Note: x % y != 0 does not guarantee that y is not a power of 2 for
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# arbitrary x and y values. However, due to the relationship between
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# number_of_bins and prefix_count, it is true for them.
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raise securesystemslib.exceptions.Error('The "number_of_bins" argument'
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' must be a power of 2.')
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return prefix_length, prefix_count, bin_size
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def _find_bin_for_hash(path_hash, number_of_bins):
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"""
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<Purpose>
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For a given hashed filename, path_hash, calculate the name of a hashed bin
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into which this file would be delegated given number_of_bins bins are in
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use.
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<Arguments>
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path_hash:
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The hash of the target file's path
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number_of_bins:
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The number of hashed_bins in use
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<Returns>
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The name of the hashed bin path_hash would be binned into.
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"""
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prefix_length, _, bin_size = _get_bin_numbers(number_of_bins)
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prefix = int(path_hash[:prefix_length], 16)
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low = prefix - (prefix % bin_size)
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high = (low + bin_size - 1)
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return _create_bin_name(low, high, prefix_length)
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def create_new_repository(repository_directory, repository_name='default',
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storage_backend=None):
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"""
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