# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1253305285 -7200
# Node ID e0fbe13922c1bc90674132a9916cf714b0ab1448
# Parent  7189d6ef001f984dd34703904850fa6e221252f6
Introduced separate vint functions for strings and byte arrays.
Modified position writing to use arrays for potentially improved performance.

diff -r 7189d6ef001f -r e0fbe13922c1 iixr/data.py
--- a/iixr/data.py	Fri Sep 18 21:07:35 2009 +0200
+++ b/iixr/data.py	Fri Sep 18 22:21:25 2009 +0200
@@ -21,6 +21,7 @@
 from array import array
 
 vint_cache = {}
+vint_bytes_cache = {}
 
 def vint(number):
 
@@ -30,17 +31,8 @@
         return vint_cache[number]
     except KeyError:
         if number >= 0:
-
-            # Write the number from least to most significant digits.
-
             bytes = array('B')
-
-            while number > 127:
-                bytes.append(number & 127 | 128)
-                number = number >> 7
-            else:
-                bytes.append(number)
-
+            _vint_to_array(number, bytes)
             return bytes.tostring()
 
         # Negative numbers are not supported.
@@ -48,7 +40,35 @@
         else:
             raise ValueError, "Number %r is negative." % number
 
+def vint_to_array(number, bytes):
+
+    "Write 'number' as a variable-length integer to 'bytes'."
+
+    try:
+        bytes += vint_bytes_cache[number]
+    except KeyError:
+        if number >= 0:
+            _vint_to_array(number, bytes)
+
+        # Negative numbers are not supported.
+
+        else:
+            raise ValueError, "Number %r is negative." % number
+
+def _vint_to_array(number, bytes):
+
+    "Write the 'number' to 'bytes' from least to most significant digits."
+
+    while number > 127:
+        bytes.append(number & 127 | 128)
+        number = number >> 7
+    else:
+        bytes.append(number)
+
 for i in xrange(0, 65536):
-    vint_cache[i] = vint(i)
+    bytes = array('B')
+    _vint_to_array(i, bytes)
+    vint_bytes_cache[i] = bytes
+    vint_cache[i] = bytes.tostring()
 
 # vim: tabstop=4 expandtab shiftwidth=4
diff -r 7189d6ef001f -r e0fbe13922c1 iixr/positions.py
--- a/iixr/positions.py	Fri Sep 18 21:07:35 2009 +0200
+++ b/iixr/positions.py	Fri Sep 18 22:21:25 2009 +0200
@@ -19,7 +19,8 @@
 """
 
 from iixr.files import *
-from iixr.data import vint
+from iixr.data import vint, vint_to_array
+from array import array
 
 class PositionWriter(FileWriter):
 
@@ -44,18 +45,19 @@
         # Write the document number delta.
         # Write the number of positions.
 
-        output = [docnum - self.last_docnum, len(positions)]
+        output = array('B')
+        vint_to_array(docnum - self.last_docnum, output)
+        vint_to_array(len(positions), output)
 
         # Write the position deltas.
 
-        append = output.append
         last = 0
 
         for position in positions:
-            append(position - last)
+            vint_to_array(position - last, output)
             last = position
 
-        self.f.write("".join([vint(x) for x in output]))
+        output.tofile(self.f)
 
         self.last_docnum = docnum