Added iterator facility, which enables scripts that copy data

from one storage to another.

src/ZODB/FileStorage.py

@@ -184,7 +184,7 @@
 #   may have a back pointer to a version record or to a non-version
 #   record.
 #
-__version__='$Revision: 1.41 $'[11:-2]
+__version__='$Revision: 1.42 $'[11:-2]
 
 import struct, time, os, bpthread, string, base64, sys
 from struct import pack, unpack
@@ -272,6 +272,8 @@ class FileStorage(BaseStorage.BaseStorage):
 
             self._tfile=None
 
+        self._file_name=file_name
+
         BaseStorage.BaseStorage.__init__(self, file_name)
 
         index, vindex, tindex, tvindex = self._newIndexes()
@@ -1312,6 +1314,9 @@ class FileStorage(BaseStorage.BaseStorage):
             self._packt=z64
             _lock_release()
 
+    def iterator(self): return FileIterator(self._file_name)
+        
+
 def shift_transactions_forward(index, vindex, tindex, file, pos, opos):
     """Copy transactions forward in the data file
 
@@ -1684,3 +1689,194 @@ def _truncate(file, name, pos):
             
     seek(pos)
     file.truncate()
+
+class Iterator:
+    """A General simple iterator that uses the Python for-loop index protocol
+    """
+    __index=-1
+    __current=None
+
+    def __getitem__(self, i):
+        __index=self.__index
+        while i > __index:
+            __index=__index+1
+            self.__current=self.next(__index)
+
+        self.__index=__index
+        return self.__current
+
+
+class FileIterator(Iterator):
+    """Iterate over the transactions in a FileStorage file.
+    """
+    _ltid=z64
+    
+    def __init__(self, file):
+        if type(file) is type(''): file=open(file, 'r+b')
+        self._file=file
+        if file.read(4) != packed_version: raise FileStorageFormatError, name
+        file.seek(0,2)
+        self._file_size=file.tell()
+        self._pos=4
+        self._index={}
+
+    def next(self, index=0):
+        file=self._file
+        seek=file.seek
+        read=file.read
+        pos=self._pos
+
+        while 1:
+            # Read the transaction record
+            seek(pos)
+            h=read(23)
+            if len(h) < 23: break
+
+            tid, stl, status, ul, dl, el = unpack(">8s8scHHH",h)
+            if el < 0: el=t32-el
+
+            if tid <= self._ltid:
+                warn("%s time-stamp reduction at %s", name, pos)
+            self._ltid=tid
+
+            tl=u64(stl)
+
+            if tl+pos+8 > self._file_size or status=='c':
+                # Hm, the data were truncated or the checkpoint flag wasn't
+                # cleared.  They may also be corrupted,
+                # in which case, we don't want to totally lose the data.
+                warn("%s truncated, possibly due to damaged records at %s",
+                     name, pos)
+                break
+
+            if status not in ' up':
+                warn('%s has invalid status, %s, at %s', name, status, pos)
+
+            if ul > tl or dl > tl or el > tl or tl < (23+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 the end and read what should be the transaction length
+                # of the last transaction.
+                seek(-8, 2)
+                rtl=u64(read(8))
+                # Now check to see if the redundant transaction length is
+                # reasonable:
+                if self._file_size - rtl < pos or rtl < 23:
+                    nearPanic('%s has invalid transaction header at %s',
+                              name, pos)
+                    warn("It appears that there is invalid data at the end of the "
+                         "file, possibly due to a system crash.  %s truncated "
+                         "to recover from bad data at end."
+                         % name)
+                    break
+                else:
+                    warn('%s has invalid transaction header at %s', name, pos)
+                    break
+
+            # if tid >= stop: raise IndexError, index
+
+            tpos=pos
+            tend=tpos+tl
+
+            if status=='u':
+                # Undone transaction, skip it
+                seek(tend)
+                h=read(8)
+                if h != stl:
+                    panic('%s has inconsistent transaction length at %s',
+                          name, pos)
+                pos=tend+8
+                continue
+
+            pos=tpos+23+ul+dl+el
+            user=read(ul)
+            description=read(dl)
+            d={}
+            if el:
+                try: 
+                    e=loads(read(el))
+                    d.update(e)
+                except: pass
+            result=RecordIterator(
+                tid, user, description, d, 
+                pos, (tend, file, seek, read,
+                      self._index, self._index.get,
+                      tpos,
+                      )
+                )
+
+            pos=tend
+
+            # Read the (intentionally redundant) transaction length
+            seek(pos)
+            h=read(8)
+            if h != stl:
+                warn("%s redundant transaction length check failed at %s",
+                     name, pos)
+                break
+            self._pos=pos+8
+
+            return result
+
+        raise IndexError, index
+    
+class RecordIterator(Iterator):
+    """Iterate over the transactions in a FileStorage file.
+    """
+    def __init__(self, tid, user, desc, ext, pos, stuff):
+        self.tid=tid
+        self.user=user
+        self.description=desc
+        self._extension=ext
+        self._pos=pos
+        self._stuff = stuff
+
+    def next(self, index=0):
+        name=''
+        pos = self._pos
+        tend, file, seek, read, _index, get, tpos = self._stuff
+        while pos < tend:
+            # Read the data records for this transaction
+
+            seek(pos)
+            h=read(42)
+            oid,serial,sprev,stloc,vlen,splen = unpack(">8s8s8s8sH8s", h)
+            prev=u64(sprev)
+            tloc=u64(stloc)
+            plen=u64(splen)
+
+            dlen=42+(plen or 8)
+
+            if vlen:
+                dlen=dlen+16+vlen
+                seek(8,1)
+                pv=u64(read(8))
+                version=read(vlen)
+            else:
+                version=''
+
+            if pos+dlen > tend or tloc != tpos:
+                warn("%s data record exceeds transaction record at %s",
+                     name, pos)
+                break
+
+            self._pos=pos+dlen
+            if plen: p=read(plen)
+            else:
+                p=read(8)
+                p=_loadBack(file, oid, p)[0]
+                
+            r=Record(oid, get(oid, None), serial, version, p)
+            _index[oid]=serial
+            
+            return r
+        
+        raise IndexError, index
+
+
+class Record:
+    """An abstract database record
+    """
+    def __init__(self, *args):
+        self.oid, self.old, self.serial, self.version, self.p = args