--- a/mercurial/util.py	Wed Aug 04 13:21:11 2010 -0500
+++ b/mercurial/util.py	Fri Aug 06 12:59:13 2010 -0500
@@ -925,30 +925,36 @@
                 else:
                     yield chunk
         self.iter = splitbig(in_iter)
-        self.buf = ''
+        self._queue = []
 
     def read(self, l):
         """Read L bytes of data from the iterator of chunks of data.
         Returns less than L bytes if the iterator runs dry."""
-        if l > len(self.buf) and self.iter:
-            # Clamp to a multiple of 2**16
-            targetsize = max(l, 2**16)
-            collector = [str(self.buf)]
-            collected = len(self.buf)
-            for chunk in self.iter:
-                collector.append(chunk)
-                collected += len(chunk)
-                if collected >= targetsize:
+        left = l
+        buf = ''
+        queue = self._queue
+        while left > 0:
+            # refill the queue
+            if not queue:
+                target = 2**18
+                for chunk in self.iter:
+                    queue.append(chunk)
+                    target -= len(chunk)
+                    if target <= 0:
+                        break
+                if not queue:
                     break
+
+            chunk = queue.pop(0)
+            left -= len(chunk)
+            if left < 0:
+                queue.insert(0, chunk[left:])
+                buf += chunk[:left]
             else:
-                self.iter = False
-            self.buf = ''.join(collector)
-        if len(self.buf) == l:
-            s, self.buf = str(self.buf), ''
-        else:
-            s, self.buf = self.buf[:l], buffer(self.buf, l)
-        return s
+                buf += chunk
 
+        return buf
+        
 def filechunkiter(f, size=65536, limit=None):
     """Create a generator that produces the data in the file size
     (default 65536) bytes at a time, up to optional limit (default is