# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1317580983 -7200
# Node ID 94f93801356cb6e8b451e362b3b231b6e944b3fe
# Parent  fc8abb1911d0ac8074c52561056e76ec66e77706
Converted the indexer into a sequence-like class.

diff -r fc8abb1911d0 -r 94f93801356c simplex/__init__.py
--- a/simplex/__init__.py	Sun Oct 02 19:52:30 2011 +0200
+++ b/simplex/__init__.py	Sun Oct 02 20:43:03 2011 +0200
@@ -29,42 +29,9 @@
 """
 
 from simplex.readers import *
+from simplex.indexers import *
 import bisect
 
-def make_index(reader, get_key, interval):
-
-    """
-    Index a resource whose 'reader' provides records, using a 'get_key'
-    operation to yield the key for such records, creating an index entry for a
-    record after a given number of records, defined by 'interval', have been
-    read since the last entry was produced.
-    """
-
-    l = []
-    pos = 0
-
-    current_key = None
-    start_pos = 0
-
-    for i, record in enumerate(reader):
-        key = get_key(record)
-
-        # Where duplicate keys are permitted, the first record employing the key
-        # must be available as an index entry. Otherwise, records preceding the
-        # one referenced by the entry may have the same key and be missed when
-        # seeking using the index.
-
-        if key != current_key:
-            current_key = key
-            start_pos = pos
-
-        if i % interval == 0:
-            l.append((current_key, start_pos))
-
-        pos += len(record)
-
-    return l
-
 def find_with_index(reader, get_key, l, term):
 
     """
diff -r fc8abb1911d0 -r 94f93801356c simplex/indexers.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/simplex/indexers.py	Sun Oct 02 20:43:03 2011 +0200
@@ -0,0 +1,86 @@
+#!/usr/bin/env python
+
+"""
+Indexing classes.
+
+Copyright (C) 2011 Paul Boddie <paul@boddie.org.uk>
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; either version 3 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along
+with this program.  If not, see <http://www.gnu.org/licenses/>.
+"""
+
+class Indexer:
+
+    "An indexer which records an entry periodically."
+
+    def __init__(self, output, get_key, interval):
+
+        """
+        Index a resource, recording entries in the given 'output' sequence,
+        using a 'get_key' operation to yield the key for each record, creating
+        an index entry for a record after a given number of records, defined by
+        'interval', have been appended since the last entry was produced.
+        """
+
+        self.output = output
+        self.interval = interval
+        self.get_key = get_key
+
+        self.count = 0
+        self.pos = 0
+
+        # Information about the current group.
+
+        self.start_pos = 0
+        self.current_key = None
+
+    def append(self, record):
+
+        """
+        Present the given 'record' to the indexer, recording it if appropriate.
+        """
+
+        key = self.get_key(record)
+
+        # Where duplicate keys are permitted, the first record employing the key
+        # must be available as an index entry. Otherwise, records preceding the
+        # one referenced by the entry may have the same key and be missed when
+        # seeking using the index.
+
+        if key != self.current_key:
+            self.current_key = key
+            self.start_pos = self.pos
+
+        if self.count % self.interval == 0:
+            self.output.append((self.current_key, self.start_pos))
+
+        self.count += 1
+        self.pos += len(record)
+
+def make_index(reader, get_key, interval):
+
+    """
+    Index a resource whose 'reader' provides records, using a 'get_key'
+    operation to yield the key for such records, creating an index entry for a
+    record after a given number of records, defined by 'interval', have been
+    read since the last entry was produced.
+    """
+
+    l = []
+    indexer = Indexer(l, get_key, interval)
+
+    for record in reader:
+        indexer.append(record)
+
+    return l
+
+# vim: tabstop=4 expandtab shiftwidth=4