Added utils.{transaction,error}

src/utils/__init__.py

@@ -102,6 +102,8 @@ import seq
 import str
 import file
 import iter
+import error
 import python
+import transaction
 
 # vim:set shiftwidth=4 tabstop=4 expandtab textwidth=79:

src/utils/error.py

@@ -0,0 +1,45 @@
+###
+# Copyright (c) 2005, Jeremiah Fincher
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+#   * Redistributions of source code must retain the above copyright notice,
+#     this list of conditions, and the following disclaimer.
+#   * Redistributions in binary form must reproduce the above copyright notice,
+#     this list of conditions, and the following disclaimer in the
+#     documentation and/or other materials provided with the distribution.
+#   * Neither the name of the author of this software nor the name of
+#     contributors to this software may be used to endorse or promote products
+#     derived from this software without specific prior written consent.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+###
+
+import os
+
+import gen
+
+class Error(Exception):
+    def __init__(self, msg, e=None):
+        self.msg = msg
+        self.e = e
+
+    def __str__(self):
+        if self.e is not None:
+            return os.linesep.join([self.msg, gen.exnToString(self.e)])
+        else:
+            return self.msg
+
+# vim:set shiftwidth=4 tabstop=8 expandtab textwidth=78:

src/utils/file.py

@@ -36,6 +36,32 @@ import shutil
 import os.path
 from iter import ifilter
 
+def contents(filename):
+    return file(filename).read()
+
+def open(filename, mode='wb', *args, **kwargs):
+    """filename -> file object.
+
+    Returns a file object for filename, creating as many directories as may be
+    necessary.  I.e., if the filename is ./foo/bar/baz, and . exists, and ./foo
+    exists, but ./foo/bar does not exist, bar will be created before opening
+    baz in it.
+    """
+    if mode not in ('w', 'wb'):
+        raise ValueError, 'utils.file.open expects to write.'
+    (dirname, basename) = os.path.split(filename)
+    os.makedirs(dirname)
+    return file(filename, mode, *args, **kwargs)
+
+def copy(src, dst):
+    """src, dst -> None
+
+    Copies src to dst, using this module's 'open' function to open dst.
+    """
+    srcfd = file(src)
+    dstfd = open(dst, 'wb')
+    shutil.copyfileobj(srcfd, dstfd)
+    
 def writeLine(fd, line):
     fd.write(line)
     if not line.endswith('\n'):

src/utils/transaction.py

@@ -0,0 +1,179 @@
+###
+# Copyright (c) 2005, Jeremiah Fincher
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+#   * Redistributions of source code must retain the above copyright notice,
+#     this list of conditions, and the following disclaimer.
+#   * Redistributions in binary form must reproduce the above copyright notice,
+#     this list of conditions, and the following disclaimer in the
+#     documentation and/or other materials provided with the distribution.
+#   * Neither the name of the author of this software nor the name of
+#     contributors to this software may be used to endorse or promote products
+#     derived from this software without specific prior written consent.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+###
+
+"""
+Defines a Transaction class for multi-file transactions.
+"""
+
+import os
+import shutil
+import os.path
+
+import error
+import python
+import file as File
+
+# 'txn' is used as an abbreviation for 'transaction' in the following source.
+
+class FailedAcquisition(error.Error):
+    def __init__(self, txnDir, e=None):
+        self.txnDir = txnDir
+        msg = 'Could not acquire transaction directory: %s.' % self.txnDir
+        error.Error.__init__(self, msg, e)
+        
+class InProgress(error.Error):
+    def __init__(self, inProgress, e=None):
+        self.inProgress = inProgress
+        msg = 'Transaction appears to be in progress already: %s exists.' % \
+              self.inProgress
+        error.Error.__init__(self, msg, e)
+        
+
+class TransactionMixin(python.Object):
+    JOURNAL = 'journal'
+    ORIGINALS = 'originals'
+    INPROGRESS = '.inProgress'
+    REPLACEMENTS = 'replacements'
+    # expects a self.dir.  used by Transaction and Rollback.
+    def __init__(self, txnDir):
+        self.txnDir = txnDir
+        self.dir = self.txnDir + self.INPROGRESS
+        self._journalName = self.dirize(self.JOURNAL)
+
+    def escape(self, filename):
+        return os.path.abspath(filename)[1:]
+    
+    def dirize(self, *args):
+        return os.path.join(self.dir, *args)
+
+    def _original(self, filename):
+        return self.dirize(self.ORIGINALS, self.escape(filename))
+    
+    def _replacement(self, filename):
+        return self.dirize(self.REPLACEMENTS, self.escape(filename))
+    
+    def checkCwd(self):
+        expected = File.contents(self.dirize('cwd'))
+        if os.getcwd() != expected:
+            raise InvalidCwd(expected)
+        
+    def journalCommands(self):
+        journal = file(self._journalName)
+        for line in journal:
+            line = line.rstrip('\n')
+            (command, rest) = line.split(None, 1)
+            args = rest.split()
+            yield (command, args)
+        
+
+class Transaction(TransactionMixin):
+    def __init__(self, *args, **kwargs):
+        """Transaction(root, txnDir) -> None
+
+        txnDir is the directory that will hold the transaction's working files
+        and such.  If it can't be renamed, there is probably an active
+        transaction.
+        """
+        TransactionMixin.__init__(self, *args, **kwargs)
+        if os.path.exists(self.dir):
+            raise InProgress(self.dir)
+        if not os.path.exists(self.txnDir):
+            raise FailedAcquisition(self.txnDir)
+        try:
+            os.rename(self.txnDir, self.dir)
+        except EnvironmentError, e:
+            raise TransactionAcquisitionFailure(self.txnDir, e)
+        os.mkdir(self.dirize(self.ORIGINALS))
+        os.mkdir(self.dirize(self.REPLACEMENTS))
+        self._journal = file(self._journalName, 'a')
+        cwd = file(self.dirize('cwd'), 'w')
+        cwd.write(os.getcwd())
+        cwd.close()
+
+    def journalCommand(self, command, *args):
+        File.writeLine(self._journal,
+                       '%s %s' % (command, ' '.join(map(str, args))))
+        self._journal.flush()
+
+    def _makeOriginal(self, filename):
+        File.copy(filename, self._original(filename))
+
+    def replace(self, filename):
+        self.checkCwd()
+        self._makeOriginal(filename)
+        self.journalCommand('replace', filename)
+        return File.open(self._replacement(filename))
+
+    def append(self, filename):
+        self.checkCwd()
+        length = os.stat(filename).st_size
+        self.journalCommand('append', filename, length)
+        replacement = self._replacement(filename)
+        File.copy(filename, replacement)
+        return file(replacement, 'a')
+
+    def commit(self, removeWhenComplete=True):
+        self._journal.close()
+        self.checkCwd()
+        File.touch(self.dirize('commit'))
+        for (command, args) in self.journalCommands():
+            methodName = 'commit%s' % command.capitalize()
+            getattr(self, methodName)(*args)
+        File.touch(self.dirize('committed'))
+        if removeWhenComplete:
+            shutil.rmtree(self.dir)
+
+    def commitReplace(self, filename):
+        shutil.copy(self._replacement(filename), filename)
+
+    def commitAppend(self, filename, length):
+        shutil.copy(self._replacement(filename), filename)
+
+
+class Rollback(TransactionMixin):
+    def rollback(self, removeWhenComplete=True):
+        self.checkCwd()
+        if not os.path.exists(self.dirize('commit')):
+            return # No action taken; commit hadn't begun.
+        for (command, args) in self.journalCommands():
+            methodName = 'rollback%s' % command.capitalize()
+            getattr(self, methodName)(*args)
+        if removeWhenComplete:
+            shutil.rmtree(self.dir)
+
+    def rollbackReplace(self, filename):
+        shutil.copy(self._original(filename), filename)
+
+    def rollbackAppend(self, filename, length):
+        fd = file(filename, 'a')
+        fd.truncate(int(length))
+        fd.close()
+        
+
+# vim:set shiftwidth=4 tabstop=8 expandtab textwidth=78: