# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1295916943 -3600
# Node ID 34f535fe8cb08a727d4edfded47eddc670cbd405
# Parent  c4da9505f73e98eb5cf54d1a23433a395f95aa2d
Introduced various optimisation attempts.

diff -r c4da9505f73e -r 34f535fe8cb0 iixr/data.py
--- a/iixr/data.py	Tue Jan 25 00:36:31 2011 +0100
+++ b/iixr/data.py	Tue Jan 25 01:55:43 2011 +0100
@@ -3,7 +3,7 @@
 """
 Variable-length integer functions.
 
-Copyright (C) 2009, 2010 Paul Boddie <paul@boddie.org.uk>
+Copyright (C) 2009, 2010, 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
@@ -65,6 +65,16 @@
     else:
         bytes.append(number)
 
+def vint_from_array(bytes):
+
+    "Read a variable-length integer from 'bytes', returning a number."
+
+    number = 0
+    while bytes:
+        number <<= 7
+        number += bytes.pop() & 127
+    return number
+
 def string_to_array(s, bytes):
 
     "Write the given string 's' to 'bytes'."
diff -r c4da9505f73e -r 34f535fe8cb0 iixr/files.py
--- a/iixr/files.py	Tue Jan 25 00:36:31 2011 +0100
+++ b/iixr/files.py	Tue Jan 25 01:55:43 2011 +0100
@@ -3,7 +3,7 @@
 """
 Generic file access.
 
-Copyright (C) 2009, 2010 Paul Boddie <paul@boddie.org.uk>
+Copyright (C) 2009, 2010, 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
@@ -18,7 +18,7 @@
 with this program.  If not, see <http://www.gnu.org/licenses/>.
 """
 
-from iixr.data import vint, vint_to_array
+from iixr.data import vint, vint_to_array, vint_from_array
 from array import array
 import zlib
 
@@ -76,6 +76,15 @@
 
         self.f.write(vint(number))
 
+    def write_numbers(self, numbers):
+
+        "Write 'numbers' to the file using a variable length encoding."
+
+        output = array('B')
+        for number in numbers:
+            vint_to_array(number, output)
+        output.tofile(self.f)
+
     def write_string(self, s, compress=0):
 
         """
@@ -152,7 +161,7 @@
             while csd & 128:
                 fromfile(f, 1)
                 csd = a[-1]
-            return sum([((csd & 127) << (number * 7)) for (number, csd) in enumerate(a)])
+            return vint_from_array(a)
 
     def read_string(self, decompress=0):
 
@@ -184,16 +193,21 @@
 
     def read_sequence(self, last, size, monotonic=1):
         if size:
-            expect_delta = 1
             value = []
-            for v in last:
-                v_in = self.read_number()
-                if monotonic or expect_delta:
+            if monotonic:
+                for v in last:
+                    v_in = self.read_number()
                     value.append(v + v_in)
-                    if expect_delta and v_in != 0:
-                        expect_delta = 0
-                else:
-                    value.append(v_in - 1)
+            else:
+                expect_delta = 1
+                for v in last:
+                    v_in = self.read_number()
+                    if expect_delta:
+                        value.append(v + v_in)
+                        if v_in != 0:
+                            expect_delta = 0
+                    else:
+                        value.append(v_in - 1)
             return tuple(value)
         else:
             return last + self.read_number()
diff -r c4da9505f73e -r 34f535fe8cb0 iixr/terms.py
--- a/iixr/terms.py	Tue Jan 25 00:36:31 2011 +0100
+++ b/iixr/terms.py	Tue Jan 25 01:55:43 2011 +0100
@@ -52,16 +52,14 @@
         self.write_string(suffix)
 
         # Write the offset delta.
-
-        self.write_number(offset - self.last_offset)
-
         # Write the frequency.
-
-        self.write_number(frequency)
-
         # Write the document frequency.
 
-        self.write_number(doc_frequency)
+        self.write_numbers((
+            offset - self.last_offset,
+            frequency,
+            doc_frequency
+            ))
 
         self.last_term = term
         self.last_offset = offset