Add cat-file and hash-object

This commit is contained in:
Nathan McRae 2024-07-04 22:14:49 -07:00
parent 7fe0065828
commit a057ea5831

View File

@ -185,3 +185,145 @@ argsp.add_argument("path",
def cmd_status(args):
# TODO: actually get status
print(repo_find(args.path).worktree)
class GitObject (object):
def __init__(self, data=None):
if data != None:
self.deserialize(data)
else:
self.init()
def serialize(self, repo):
"""This function MUST be implemented by subclasses.
It must read the object's contents from self.data, a byte string, and
do whatever it takes to convert it into a meaningful representation. What exactly that means depends on each subclass."""
raise Exception("Unimplemented!")
def deserialize(self, repo):
raise Exception("Unimplemented!")
def init(self):
pass # other implementations might do something here
def object_read(repo, sha):
"""Read object sha from Git repository repo. Return a
GitObject whose exact type depends on the object."""
path = GitRepository.repo_file(repo, "objects", sha[0:2], sha[2:])
if not os.path.isfile(path):
return None
with open(path, "rb") as f:
raw = zlib.decompress(f.read())
# Read object type
x = raw.find(b' ')
fmt = raw[0:x]
# Read and validate object size
y = raw.find(b'\x00', x)
size = int(raw[x:y].decode("ascii"))
if size != len(raw)-y-1:
raise Exception(f"Malformed object {sha}: bad length")
match fmt:
case b'commit' : c=GitCommit
case b'tree' : c=GitTree
case b'tag' : c=GitTag
case b'blob' : c=GitBlob
case _:
raise Exception(f"Unknown type {fmt.decode('ascii')} for object {sha}")
return c(raw[y+1:])
def object_write(obj, repo=None):
data = obj.serialize()
# Add header
result = obj.fmt + b' ' + str(len(data)).encode() + b'\x00' + data
# Compute hash
sha = hashlib.sha1(result).hexdigest()
if repo:
# Compute path
path=GitRepository.repo_file(repo, "objects", sha[0:2], sha[2:], mkdir=True)
if not os.path.exists(path):
with open(path, 'wb') as f:
f.write(zlib.compress(result))
return sha
class GitBlob(GitObject):
fmt=b'blob'
def serialize(self):
return self.blobdata
def deserialize(self, data):
self.blobdata = data
argsp = argsubparsers.add_parser("cat-file",
help="Provide content of repository objects")
argsp.add_argument("type",
metavar="type",
choices=["blob", "commit", "tag", "tree"],
help="Specify the type")
argsp.add_argument("object",
metavar="object",
help="The object to display")
def cmd_cat_file(args):
repo = repo_find()
cat_file(repo, args.object, fmt=args.type.encode())
def cat_file(repo, obj, fmt=None):
obj = object_read(repo, object_find(repo, obj, fmt=fmt))
sys.stdout.buffer.write(obj.serialize())
def object_find(repo, name, fmt=None, follow=True):
return name
argsp = argsubparsers.add_parser(
"hash-object",
help="Compute object ID an optionally creates a blob from a file")
argsp.add_argument("-t",
metavar="type",
dest="type",
choices=["blob", "commit", "tag", "tree"],
default="blob",
help="Specify the type")
argsp.add_argument("-w",
dest="write",
action="store_true",
help="Actually write the object into the database")
argsp.add_argument("path",
help="Read object from <file>")
def cmd_hash_object(args):
if args.write:
repo = repo_find()
else:
repo = None
with open(args.path, "rb") as fd:
sha = object_hash(fd, args.type.encode(), repo)
print(sha)
def object_hash(fd, fmt, repo=None):
"""Hash object, writing it to repo if provided"""
data = fd.read()
match fmt:
case b'commit' : obj=GitCommit(data)
case b'tree' : obj=GitTree(data)
case b'tag' : obj=GitTag(data)
case b'blob' : obj=GitBlob(data)
case _ : raise Exception(f"Unknown type {fmt}")
return object_write(obj, repo)