Added character data buffering to pyexpat parser objects.

Setting the buffer_text attribute to true causes the parser to collect
character data, waiting as long as possible to report it to the Python
callback.  This can save an enormous number of callbacks from C to
Python, which can be a substantial performance improvement.

buffer_text defaults to false.

Lib/test/test_pyexpat.py

@@ -6,7 +6,7 @@
 import pyexpat
 from xml.parsers import expat
 
-from test_support import sortdict
+from test_support import sortdict, TestFailed
 
 class Outputter:
     def StartElementHandler(self, name, attrs):
@@ -218,3 +218,96 @@ for entry in L:
         print "(it didn't)"
         print "L =", `L`
         break
+
+# Tests of the buffer_text attribute.
+import sys
+
+class TextCollector:
+    def __init__(self, parser):
+        self.stuff = []
+
+    def check(self, expected, label):
+        require(self.stuff == expected,
+                "%s\nstuff    = %s\nexpected = %s"
+                % (label, `self.stuff`, `map(unicode, expected)`))
+
+    def CharacterDataHandler(self, text):
+        self.stuff.append(text)
+
+    def StartElementHandler(self, name, attrs):
+        self.stuff.append("<%s>" % name)
+        bt = attrs.get("buffer-text")
+        if bt == "yes":
+            parser.buffer_text = 1
+        elif bt == "no":
+            parser.buffer_text = 0
+
+    def EndElementHandler(self, name):
+        self.stuff.append("</%s>" % name)
+
+    def CommentHandler(self, data):
+        self.stuff.append("<!--%s-->" % data)
+
+def require(cond, label):
+    # similar to confirm(), but no extraneous output
+    if not cond:
+        raise TestFailed(label)
+
+def setup(handlers=[]):
+    parser = expat.ParserCreate()
+    require(not parser.buffer_text,
+            "buffer_text not disabled by default")
+    parser.buffer_text = 1
+    handler = TextCollector(parser)
+    parser.CharacterDataHandler = handler.CharacterDataHandler
+    for name in handlers:
+        setattr(parser, name, getattr(handler, name))
+    return parser, handler
+
+parser, handler = setup()
+require(parser.buffer_text,
+        "text buffering either not acknowledged or not enabled")
+parser.Parse("<a>1<b/>2<c/>3</a>", 1)
+handler.check(["123"],
+              "buffered text not properly collapsed")
+
+# XXX This test exposes more detail of Expat's text chunking than we
+# XXX like, but it tests what we need to concisely.
+parser, handler = setup(["StartElementHandler"])
+parser.Parse("<a>1<b buffer-text='no'/>2\n3<c buffer-text='yes'/>4\n5</a>", 1)
+handler.check(["<a>", "1", "<b>", "2", "\n", "3", "<c>", "4\n5"],
+              "buffering control not reacting as expected")
+
+parser, handler = setup()
+parser.Parse("<a>1<b/>&lt;2&gt;<c/>&#32;\n&#x20;3</a>", 1)
+handler.check(["1<2> \n 3"],
+              "buffered text not properly collapsed")
+
+parser, handler = setup(["StartElementHandler"])
+parser.Parse("<a>1<b/>2<c/>3</a>", 1)
+handler.check(["<a>", "1", "<b>", "2", "<c>", "3"],
+              "buffered text not properly split")
+
+parser, handler = setup(["StartElementHandler", "EndElementHandler"])
+parser.CharacterDataHandler = None
+parser.Parse("<a>1<b/>2<c/>3</a>", 1)
+handler.check(["<a>", "<b>", "</b>", "<c>", "</c>", "</a>"],
+              "huh?")
+
+parser, handler = setup(["StartElementHandler", "EndElementHandler"])
+parser.Parse("<a>1<b></b>2<c/>3</a>", 1)
+handler.check(["<a>", "1", "<b>", "</b>", "2", "<c>", "</c>", "3", "</a>"],
+              "huh?")
+
+parser, handler = setup(["CommentHandler", "EndElementHandler",
+                         "StartElementHandler"])
+parser.Parse("<a>1<b/>2<c></c>345</a> ", 1)
+handler.check(["<a>", "1", "<b>", "</b>", "2", "<c>", "</c>", "345", "</a>"],
+              "buffered text not properly split")
+
+parser, handler = setup(["CommentHandler", "EndElementHandler",
+                         "StartElementHandler"])
+parser.Parse("<a>1<b/>2<c></c>3<!--abc-->4<!--def-->5</a> ", 1)
+handler.check(["<a>", "1", "<b>", "</b>", "2", "<c>", "</c>", "3",
+               "<!--abc-->", "4", "<!--def-->", "5", "</a>"],
+              "buffered text not properly split")