# Copyright (C) 2015-2021 The Software Heritage developers
# See the AUTHORS file at the top-level directory of this distribution
# License: GNU General Public License version 3, or any later version
# See top-level LICENSE file for more information
"""
Converts SWH model objects to git(-like) objects
Most of the functions in this module take as argument an object from
:mod:`swh.model.model`, and format it like a git object.
They are the inverse functions of those in :mod:`swh.loader.git.converters`,
but with extensions, as SWH's model is a superset of Git's:
* extensions of existing types (eg. revision/commit and release/tag dates
can be expressed with precision up to milliseconds, to support formatting
Mercurial objects)
* new types, for SWH's specific needs (:class:`swh.model.model.RawExtrinsicMetadata`
and :class:`swh.model.model.ExtID`)
* support for somewhat corrupted git objects that we need to reproduce
This is used for two purposes:
* Format manifests that can be hashed to produce :ref:`intrinsic identifiers
<persistent-identifiers>`
* Write git objects to reproduce git repositories that were ingested in the archive.
"""
from __future__ import annotations
import datetime
from functools import lru_cache
from typing import Dict, Iterable, List, Optional, Tuple, Union, cast
import warnings
from . import model
from .collections import ImmutableDict
from .hashutil import git_object_header, hash_to_bytehex
[docs]
def content_git_object(content: model.Content) -> bytes:
"""Formats a content as a git blob.
A content's identifier is the blob sha1 à la git of the tagged content.
"""
content = cast(model.Content, content)
if content.data is None:
raise model.MissingData("Content data is None, cannot format.")
return git_object_header("blob", len(content.data)) + content.data
[docs]
def directory_entry_sort_key(entry: model.DirectoryEntry):
"""The sorting key for tree entries"""
if isinstance(entry, dict):
type_ = entry["type"]
name = entry["name"]
else:
type_ = entry.type
name = entry.name
if type_ == "dir":
return name + b"/"
else:
return name
@lru_cache()
def _perms_to_bytes(perms):
"""Convert the perms value to its canonical bytes representation"""
oc = oct(perms)[2:]
return oc.encode("ascii")
[docs]
def escape_newlines(snippet):
"""Escape the newlines present in snippet according to git rules.
New lines in git manifests are escaped by indenting the next line by one
space.
"""
if b"\n" in snippet:
return b"\n ".join(snippet.split(b"\n"))
else:
return snippet
[docs]
def normalize_timestamp(time_representation):
"""Normalize a time representation for processing by Software Heritage
This function supports a numeric timestamp (representing a number of
seconds since the UNIX epoch, 1970-01-01 at 00:00 UTC), a
:obj:`datetime.datetime` object (with timezone information), or a
normalized Software Heritage time representation (idempotency).
Args:
time_representation: the representation of a timestamp
Returns:
dict: a normalized dictionary with three keys:
- timestamp: a dict with two optional keys:
- seconds: the integral number of seconds since the UNIX epoch
- microseconds: the integral number of microseconds
- offset: the timezone offset as a number of minutes relative to
UTC
- negative_utc: a boolean representing whether the offset is -0000
when offset = 0.
"""
if time_representation is None:
return None
else:
return model.TimestampWithTimezone.from_dict(time_representation).to_dict()
[docs]
def directory_git_object(directory: Union[Dict, model.Directory]) -> bytes:
"""Formats a directory as a git tree.
A directory's identifier is the tree sha1 à la git of a directory listing,
using the following algorithm, which is equivalent to the git algorithm for
trees:
1. Entries of the directory are sorted using the name (or the name with '/'
appended for directory entries) as key, in bytes order.
2. For each entry of the directory, the following bytes are output:
- the octal representation of the permissions for the entry (stored in
the 'perms' member), which is a representation of the entry type:
- b'100644' (int 33188) for files
- b'100755' (int 33261) for executable files
- b'120000' (int 40960) for symbolic links
- b'40000' (int 16384) for directories
- b'160000' (int 57344) for references to revisions
- an ascii space (b'\x20')
- the entry's name (as raw bytes), stored in the 'name' member
- a null byte (b'\x00')
- the 20 byte long identifier of the object pointed at by the entry,
stored in the 'target' member:
- for files or executable files: their blob sha1_git
- for symbolic links: the blob sha1_git of a file containing the link
destination
- for directories: their intrinsic identifier
- for revisions: their intrinsic identifier
(Note that there is no separator between entries)
"""
if isinstance(directory, dict):
# For backward compatibility
warnings.warn(
"directory_git_object's argument should be a swh.model.model.Directory "
"object.",
DeprecationWarning,
stacklevel=2,
)
directory = model.Directory.from_dict(directory)
directory = cast(model.Directory, directory)
components = []
for entry in sorted(directory.entries, key=directory_entry_sort_key):
components.extend(
[
_perms_to_bytes(entry.perms),
b"\x20",
entry.name,
b"\x00",
entry.target,
]
)
return format_git_object_from_parts("tree", components)
[docs]
def revision_git_object(revision: Union[Dict, model.Revision]) -> bytes:
"""Formats a revision as a git tree.
The fields used for the revision identifier computation are:
- directory
- parents
- author
- author_date
- committer
- committer_date
- extra_headers or metadata -> extra_headers
- message
A revision's identifier is the 'git'-checksum of a commit manifest
constructed as follows (newlines are a single ASCII newline character)::
tree <directory identifier>
[for each parent in parents]
parent <parent identifier>
[end for each parents]
author <author> <author_date>
committer <committer> <committer_date>
[for each key, value in extra_headers]
<key> <encoded value>
[end for each extra_headers]
<message>
The directory identifier is the ascii representation of its hexadecimal
encoding.
Author and committer are formatted using the :attr:`Person.fullname` attribute only.
Dates are formatted with the :func:`format_offset` function.
Extra headers are an ordered list of [key, value] pairs. Keys are strings
and get encoded to utf-8 for identifier computation. Values are either byte
strings, unicode strings (that get encoded to utf-8), or integers (that get
encoded to their utf-8 decimal representation).
Multiline extra header values are escaped by indenting the continuation
lines with one ascii space.
If the message is None, the manifest ends with the last header. Else, the
message is appended to the headers after an empty line.
The checksum of the full manifest is computed using the 'commit' git object
type.
"""
if isinstance(revision, dict):
# For backward compatibility
warnings.warn(
"revision_git_object's argument should be a swh.model.model.Revision "
"object.",
DeprecationWarning,
stacklevel=2,
)
revision = model.Revision.from_dict(revision)
revision = cast(model.Revision, revision)
headers = [(b"tree", hash_to_bytehex(revision.directory))]
for parent in revision.parents:
if parent:
headers.append((b"parent", hash_to_bytehex(parent)))
if revision.author is not None:
headers.append((b"author", format_author_data(revision.author, revision.date)))
if revision.committer is not None:
headers.append(
(
b"committer",
format_author_data(revision.committer, revision.committer_date),
)
)
# Handle extra headers
metadata = revision.metadata or ImmutableDict()
extra_headers = revision.extra_headers or ()
if not extra_headers and "extra_headers" in metadata:
extra_headers = metadata["extra_headers"]
headers.extend(extra_headers)
return format_git_object_from_headers("commit", headers, revision.message)
[docs]
def target_type_to_git(target_type: model.ReleaseTargetType) -> bytes:
"""Convert a software heritage target type to a git object type"""
return {
model.ReleaseTargetType.CONTENT: b"blob",
model.ReleaseTargetType.DIRECTORY: b"tree",
model.ReleaseTargetType.REVISION: b"commit",
model.ReleaseTargetType.RELEASE: b"tag",
model.ReleaseTargetType.SNAPSHOT: b"refs",
}[target_type]
[docs]
def release_git_object(release: Union[Dict, model.Release]) -> bytes:
if isinstance(release, dict):
# For backward compatibility
warnings.warn(
"release_git_object's argument should be a swh.model.model.Directory "
"object.",
DeprecationWarning,
stacklevel=2,
)
release = model.Release.from_dict(release)
release = cast(model.Release, release)
headers = [
(b"object", hash_to_bytehex(release.target)),
(b"type", target_type_to_git(release.target_type)),
(b"tag", release.name),
]
if release.author is not None:
headers.append((b"tagger", format_author_data(release.author, release.date)))
return format_git_object_from_headers("tag", headers, release.message)
[docs]
def snapshot_git_object(
snapshot: Union[Dict, model.Snapshot], *, ignore_unresolved: bool = False
) -> bytes:
"""Formats a snapshot as a git-like object.
Snapshots are a set of named branches, which are pointers to objects at any
level of the Software Heritage DAG.
As well as pointing to other objects in the Software Heritage DAG, branches
can also be *alias*es, in which case their target is the name of another
branch in the same snapshot, or *dangling*, in which case the target is
unknown (and represented by the ``None`` value).
A snapshot identifier is a salted sha1 (using the git hashing algorithm
with the ``snapshot`` object type) of a manifest following the algorithm:
1. Branches are sorted using the name as key, in bytes order.
2. For each branch, the following bytes are output:
- the type of the branch target:
- ``content``, ``directory``, ``revision``, ``release`` or ``snapshot``
for the corresponding entries in the DAG;
- ``alias`` for branches referencing another branch;
- ``dangling`` for dangling branches
- an ascii space (``\\x20``)
- the branch name (as raw bytes)
- a null byte (``\\x00``)
- the length of the target identifier, as an ascii-encoded decimal number
(``20`` for current intrinsic identifiers, ``0`` for dangling
branches, the length of the target branch name for branch aliases)
- a colon (``:``)
- the identifier of the target object pointed at by the branch,
stored in the 'target' member:
- for contents: their *sha1_git*
- for directories, revisions, releases or snapshots: their intrinsic
identifier
- for branch aliases, the name of the target branch (as raw bytes)
- for dangling branches, the empty string
Note that, akin to directory manifests, there is no separator between
entries. Because of symbolic branches, identifiers are of arbitrary
length but are length-encoded to avoid ambiguity.
Args:
ignore_unresolved: if False (the default), raises an exception when
alias branches point to non-existing branches
"""
if isinstance(snapshot, dict):
# For backward compatibility
warnings.warn(
"snapshot_git_object's argument should be a swh.model.model.Snapshot "
"object.",
DeprecationWarning,
stacklevel=2,
)
snapshot = model.Snapshot.from_dict(snapshot)
snapshot = cast(model.Snapshot, snapshot)
unresolved = []
lines = []
for name, target in sorted(snapshot.branches.items()):
if not target:
target_type = b"dangling"
target_id = b""
elif target.target_type == model.SnapshotTargetType.ALIAS:
target_type = b"alias"
target_id = target.target
if target_id not in snapshot.branches or target_id == name:
unresolved.append((name, target_id))
else:
target_type = target.target_type.value.encode()
target_id = target.target
lines.extend(
[
target_type,
b"\x20",
name,
b"\x00",
("%d:" % len(target_id)).encode(),
target_id,
]
)
if unresolved and not ignore_unresolved:
raise ValueError(
"Branch aliases unresolved: %s"
% ", ".join("%r -> %r" % x for x in unresolved),
unresolved,
)
return format_git_object_from_parts("snapshot", lines)
[docs]
def extid_git_object(extid: model.ExtID) -> bytes:
"""Formats an extid as a gi-like object.
An ExtID identifier is a salted sha1 (using the git hashing algorithm with
the ``extid`` object type) of a manifest following the format:
```
extid_type $StrWithoutSpaces
[extid_version $Str]
extid $Bytes
target $CoreSwhid
[payload_type $StrWithoutSpaces]
[payload $ContentIdentifier]
```
$StrWithoutSpaces is an ASCII string, and may not contain spaces.
Newlines in $Bytes are escaped as with other git fields, ie. by adding a
space after them.
The extid_version line is only generated if the version is non-zero.
The payload_type and payload lines are only generated if they are not
:const:`None`. $ContentIdentifier is the object ID of a content object.
"""
headers = [
(b"extid_type", extid.extid_type.encode("ascii")),
]
extid_version = extid.extid_version
if extid_version != 0:
headers.append((b"extid_version", str(extid_version).encode("ascii")))
headers.extend(
[
(b"extid", extid.extid),
(b"target", str(extid.target).encode("ascii")),
]
)
payload_type = extid.payload_type
if payload_type is not None:
headers.append((b"payload_type", payload_type.encode("ascii")))
payload = extid.payload
if payload is not None:
headers.append((b"payload", payload))
return format_git_object_from_headers("extid", headers)
