用python实现git blob对象的创建和查询

Pro Git第九章用ruby创建了一个blob对象，按照其中介绍的步骤，用python实现了一遍。

import hashlib
import zlib
import os
import os.path

def calc_git_blob_obj(blob_content):
blob_header = 'blob ' + str(len(blob_content)) + '\0'
blob_store = blob_header + blob_content

blob_sha1 = hashlib.sha1(blob_store).hexdigest()

blob_compressed_content = zlib.compress(blob_store)

return blob_sha1, blob_compressed_content

def gen_git_blob_file(objects_dir, blob_sha1, blob_compressed_content):
blob_dir = objects_dir + '/' + blob_sha1[:2]
blob_file = blob_dir + '/' + blob_sha1[2:]

if not os.path.exists(blob_dir):
os.mkdir(blob_dir)

open(blob_file, 'w').write(blob_compressed_content)

def gen_git_blob_obj(objects_dir, blob_content):
blob_sha1, blob_compressed_content = calc_git_blob_obj(blob_content)

gen_git_blob_file(objects_dir, blob_sha1, blob_compressed_content)

def get_git_blob_obj(blob_file):
return zlib.decompress(open(blob_file, 'r').read())

gen_git_blob_obj('git/objects', 'what is up, doc?')
print get_git_blob_obj('git/objects/bd/9dbf5aae1a3862dd1526723246b20206e5fc37')

除了直接用zlib，还有更简化的方法，用str的encode和decode方法，还不用import zlib：

#下面两条语句是等价的
#blob_compressed_content = zlib.compress(blob_store)
blob_compressed_content = blob_store.encode('zip')

#下面两条语句也是等价的
#return zlib.decompress(open(blob_file, 'r').read())
return open(blob_file, 'r').read().decode('zip')