1 files changed, 133 insertions, 0 deletions

diff --git a/git_refs.py b/git_refs.py
new file mode 100644
index 00000000..9851e78b
--- /dev/null
+++ b/git_refs.py
@@ -0,0 +1,133 @@
+#
+# Copyright (C) 2009 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+
+HEAD    = 'HEAD'
+R_HEADS = 'refs/heads/'
+R_TAGS  = 'refs/tags/'
+R_PUB   = 'refs/published/'
+R_M     = 'refs/remotes/m/'
+
+
+class GitRefs(object):
+  def __init__(self, gitdir):
+    self._gitdir = gitdir
+    self._phyref = None
+    self._symref = None
+    self._mtime = {}
+
+  @property
+  def all(self):
+    if self._phyref is None or self._NeedUpdate():
+      self._LoadAll()
+    return self._phyref
+
+  def get(self, name):
+    try:
+      return self.all[name]
+    except KeyError:
+      return ''
+
+  def _NeedUpdate(self):
+    for name, mtime in self._mtime.iteritems():
+      try:
+        if mtime != os.path.getmtime(os.path.join(self._gitdir, name)):
+          return True
+      except OSError:
+        return True
+    return False
+
+  def _LoadAll(self):
+    self._phyref = {}
+    self._symref = {}
+    self._mtime = {}
+
+    self._ReadPackedRefs()
+    self._ReadLoose('refs/')
+    self._ReadLoose1(os.path.join(self._gitdir, HEAD), HEAD)
+
+    scan = self._symref
+    attempts = 0
+    while scan and attempts < 5:
+      scan_next = {}
+      for name, dest in scan.iteritems():
+        if dest in self._phyref:
+          self._phyref[name] = self._phyref[dest]
+        else:
+          scan_next[name] = dest
+      scan = scan_next
+      attempts += 1
+
+  def _ReadPackedRefs(self):
+    path = os.path.join(self._gitdir, 'packed-refs')
+    try:
+      fd = open(path, 'r')
+      mtime = os.path.getmtime(path)
+    except IOError:
+      return
+    except OSError:
+      return
+    try:
+      for line in fd:
+        if line[0] == '#':
+          continue
+        if line[0] == '^':
+          continue
+
+        line = line[:-1]
+        p = line.split(' ')
+        id = p[0]
+        name = p[1]
+
+        self._phyref[name] = id
+    finally:
+      fd.close()
+    self._mtime['packed-refs'] = mtime
+
+  def _ReadLoose(self, prefix):
+    base = os.path.join(self._gitdir, prefix)
+    for name in os.listdir(base):
+      p = os.path.join(base, name)
+      if os.path.isdir(p):
+        self._mtime[prefix] = os.path.getmtime(base)
+        self._ReadLoose(prefix + name + '/')
+      elif name.endswith('.lock'):
+        pass
+      else:
+        self._ReadLoose1(p, prefix + name)
+
+  def _ReadLoose1(self, path, name):
+    try:
+      fd = open(path, 'r')
+      mtime = os.path.getmtime(path)
+    except OSError:
+      return
+    except IOError:
+      return
+    try:
+      id = fd.readline()
+    finally:
+      fd.close()
+
+    if not id:
+      return
+    id = id[:-1]
+
+    if id.startswith('ref: '):
+      self._symref[name] = id[5:]
+    else:
+      self._phyref[name] = id
+    self._mtime[name] = mtime