[Zodb-checkins] CVS: StandaloneZODB/ZODB - FileStorage.py:1.80

[Jeremy Hylton]

Update of /cvs-repository/StandaloneZODB/ZODB
In directory cvs.zope.org:/tmp/cvs-serv31344

Modified Files:
	FileStorage.py 
Log Message:
Code cleanup.

Replace three small integers with symbolic constants.
    TRANS_HDR_LEN = 23
    DATA_HDR_LEN = 42
    DATA_VERSION_HDR_LEN = 58
The constants make it easier to remember what kind of header is being
read and/or what kind of offset is being computed.

Refactor commitVersion():
    - Keep locking & arg checking in commitVersion(), but move actual
      commit logic to _commitVersion().  This removes a level of
      indentation. 

    - Remove local vars that alias attributes of other vars

Add a few more POSKeyError exceptions.




=== StandaloneZODB/ZODB/FileStorage.py 1.79 => 1.80 === (604/704 lines abridged)
 
 z64='\0'*8
+# constants to support various header sizes
+TRANS_HDR_LEN = 23
+DATA_HDR_LEN = 42
+DATA_VERSION_HDR_LEN = 58
 
 def warn(message, *data):
     LOG('ZODB FS',WARNING, "%s  warn: %s\n" % (packed_version, (message % data)))
@@ -329,25 +333,26 @@
             pos=pos-tl-8
             if pos < 4: return 0
             seek(pos)
-            tid, stl, status, ul, dl, el = unpack(">8s8scHHH", read(23))
+            s = read(TRANS_HDR_LEN)
+            tid, stl, status, ul, dl, el = unpack(">8s8scHHH", s)
             if not ltid: ltid=tid
             if stl != rstl: return 0 # inconsistent lengths
             if status == 'u': continue # undone trans, search back
             if status not in ' p': return 0
-            if tl < (23+ul+dl+el): return 0
+            if tl < (TRANS_HDR_LEN + ul + dl + el): return 0
             tend=pos+tl
-            opos=pos+(23+ul+dl+el)
+            opos=pos+(TRANS_HDR_LEN + ul + dl + el)
             if opos==tend: continue # empty trans
 
             while opos < tend:
                 # Read the data records for this transaction    
                 seek(opos)
-                h=read(42)
+                h=read(DATA_HDR_LEN)
                 oid,serial,sprev,stloc,vlen,splen = unpack(">8s8s8s8sH8s", h)
                 tloc=U64(stloc)
                 plen=U64(splen)
                 
-                dlen=42+(plen or 8)
+                dlen=DATA_HDR_LEN+(plen or 8)
                 if vlen: dlen=dlen+(16+vlen)
     
                 if opos+dlen > tend or tloc != pos: return 0
@@ -422,86 +427,85 @@
         
         self._lock_acquire()
         try:
-            read=self._file.read
-            seek=self._file.seek
-            tfile=self._tfile
-            write=tfile.write
-            tindex=self._tindex

[-=- -=- -=- 604 lines omitted -=- -=- -=-]

-            if tl < (23+ul+dl+el):
+            if tl < (TRANS_HDR_LEN+ul+dl+el):
                 # We're in trouble. Find out if this is bad data in
                 # the middle of the file, or just a turd that Win 9x
                 # dropped at the end when the system crashed.  Skip to
@@ -2192,7 +2201,7 @@
                 rtl=U64(read(8))
                 # Now check to see if the redundant transaction length is
                 # reasonable:
-                if self._file_size - rtl < pos or rtl < 23:
+                if self._file_size - rtl < pos or rtl < TRANS_HDR_LEN:
                     nearPanic('%s has invalid transaction header at %s',
                               self._file.name, pos)
                     warn("It appears that there is invalid data at the end of "
@@ -2225,7 +2234,7 @@
                 pos=tend+8
                 continue
 
-            pos=tpos+(23+ul+dl+el)
+            pos=tpos+(TRANS_HDR_LEN+ul+dl+el)
             user=read(ul)
             description=read(dl)
             if el:
@@ -2273,15 +2282,14 @@
         tend, file, seek, read, tpos = self._stuff
         while pos < tend:
             # Read the data records for this transaction
-
             seek(pos)
-            h=read(42)
+            h=read(DATA_HDR_LEN)
             oid,serial,sprev,stloc,vlen,splen = unpack(">8s8s8s8sH8s", h)
             prev=U64(sprev)
             tloc=U64(stloc)
             plen=U64(splen)
 
-            dlen=42+(plen or 8)
+            dlen=DATA_HDR_LEN+(plen or 8)
 
             if vlen:
                 dlen=dlen+(16+vlen)
@@ -2312,7 +2320,7 @@
                 else:
                     p = _loadBack(file, oid, p)[0]
                 
-            r=Record(oid, serial, version, p)
+            r = Record(oid, serial, version, p)
             
             return r