XML parser

R=r
DELTA=546  (545 added, 0 deleted, 1 changed)
OCL=35318
CL=35341

src/pkg/Make.deps

@@ -30,7 +30,7 @@ expvar.install: bytes.install fmt.install http.install log.install strconv.insta
 flag.install: fmt.install os.install strconv.install
 fmt.install: io.install os.install reflect.install strconv.install utf8.install
 go/ast.install: go/token.install unicode.install utf8.install
-go/doc.install: container/vector.install go/ast.install go/token.install io.install once.install regexp.install sort.install strings.install template.install
+go/doc.install: container/vector.install go/ast.install go/token.install io.install regexp.install sort.install strings.install template.install
 go/parser.install: bytes.install container/vector.install fmt.install go/ast.install go/scanner.install go/token.install io.install os.install path.install strings.install
 go/printer.install: bytes.install container/vector.install fmt.install go/ast.install go/token.install io.install os.install reflect.install runtime.install strings.install tabwriter.install
 go/scanner.install: bytes.install container/vector.install fmt.install go/token.install io.install os.install sort.install strconv.install unicode.install utf8.install
@@ -68,3 +68,4 @@ testing/iotest.install: bytes.install io.install log.install os.install
 time.install: io.install once.install os.install syscall.install
 unicode.install:
 utf8.install: unicode.install
+xml.install: bufio.install bytes.install io.install os.install reflect.install strconv.install strings.install unicode.install utf8.install

src/pkg/Makefile

@@ -82,6 +82,7 @@ DIRS=\
 	time\
 	unicode\
 	utf8\
+	xml\
 
 NOTEST=\
 	debug/proc\

src/pkg/xml/Makefile

+# Copyright 2009 The Go Authors.  All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+include $(GOROOT)/src/Make.$(GOARCH)
+
+TARG=xml
+
+GOFILES=\
+	read.go\
+	xml.go\
+
+include $(GOROOT)/src/Make.pkg

src/pkg/xml/read.go

+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml
+
+import (
+	"bytes";
+	"io";
+	"os";
+	"reflect";
+	"strings";
+)
+
+// BUG(rsc): Mapping between XML elements and data structures is inherently flawed:
+// an XML element is an order-dependent collection of anonymous
+// values, while a data structure is an order-independent collection
+// of named values.
+// See package json for a textual representation more suitable
+// to data structures.
+
+// Unmarshal parses an XML element from r and uses the
+// reflect library to fill in an arbitrary struct, slice, or string
+// pointed at by val.  Well-formed data that does not fit
+// into val is discarded.
+//
+// For example, given these definitions:
+//
+//	type Email struct {
+//		Where string "attr";
+//		Addr string;
+//	}
+//
+//	type Result struct {
+//		XMLName xml.Name "result";
+//		Name string;
+//		Phone string;
+//		Email []Email;
+//	}
+//
+//	var result = Result{ "name", "phone", nil }
+//
+// unmarshalling the XML input
+//
+//	<result>
+//		<email where="home">
+//			<addr>gre@example.com</addr>
+//		</email>
+//		<email where='work'>
+//			<addr>gre@work.com</addr>
+//		</email>
+//		<name>Grace R. Emlin</name>
+//		<address>123 Main Street</address>
+//	</result>
+//
+// via Unmarshal(r, &result) is equivalent to assigning
+//
+//	r = Result{
+//		xml.Name{"", "result"},
+//		"Grace R. Emlin",	// name
+//		"phone",	// no phone given
+//		[]Email{
+//			Email{ "home", "gre@example.com" },
+//			Email{ "work", "gre@work.com" }
+//		}
+//	}
+//
+// Note that the field r.Phone has not been modified and
+// that the XML <address> element was discarded.
+//
+// Because Unmarshal uses the reflect package, it can only
+// assign to upper case fields.  Unmarshal uses a case-insensitive
+// comparison to match XML element names to struct field names.
+//
+// Unmarshal maps an XML element to a struct using the following rules:
+//
+//   * If the struct has a field named XMLName of type xml.Name,
+//      Unmarshal records the element name in that field.
+//
+//   * If the XMLName field has an associated tag string of the form
+//      "tag" or "namespace-URL tag", the XML element must have
+//      the given tag (and, optionally, name space) or else Unmarshal
+//      returns an error.
+//
+//   * If the XML element has an attribute whose name matches a
+//      struct field of type string with tag "attr", Unmarshal records
+//      the attribute value in that field.
+//
+//   * If the XML element contains character data, that data is
+//      accumulated in the first struct field that has tag "chardata".
+//      The struct field may have type []byte or string.
+//      If there is no such field, the character data is discarded.
+//
+//   * If the XML element contains a sub-element whose name
+//      matches a struct field whose tag is neither "attr" nor "chardata",
+//      Unmarshal maps the sub-element to that struct field.
+//
+// Unmarshal maps an XML element to a string or []byte by saving the
+// concatenation of that elements character data in the string or []byte.
+//
+// Unmarshal maps an XML element to a slice by extending the length
+// of the slice and mapping the element to the newly created value.
+//
+func Unmarshal(r io.Reader, val interface{}) os.Error {
+	v, ok := reflect.NewValue(val).(*reflect.PtrValue);
+	if !ok {
+		return os.NewError("non-pointer passed to Unmarshal");
+	}
+	p := NewParser(r);
+	elem := v.Elem();
+	for {
+		err := p.unmarshal(elem, nil);
+		if err != nil {
+			if err == os.EOF {
+				break;
+			}
+			return err;
+		}
+	}
+	return nil;
+}
+
+// An UnmarshalError represents an error in the unmarshalling process.
+type UnmarshalError string
+func (e UnmarshalError) String() string {
+	return string(e);
+}
+
+// Unmarshal a single XML element into val.
+func (p *Parser) unmarshal(val reflect.Value, start *StartElement) os.Error {
+	// Find start element if we need it.
+	if start == nil {
+		for {
+			tok, err := p.Token();
+			if err != nil {
+				return err;
+			}
+			if t, ok := tok.(StartElement); ok {
+				start = &t;
+				break;
+			}
+		}
+	}
+
+	var (
+		data []byte;
+		saveData reflect.Value;
+		sv *reflect.StructValue;
+		styp *reflect.StructType;
+	)
+	switch v := val.(type) {
+	case *reflect.SliceValue:
+		typ := v.Type().(*reflect.SliceType);
+		if _, ok := typ.Elem().(*reflect.Uint8Type); ok {
+			// []byte
+			saveData = v;
+			break;
+		}
+
+		// Slice of element values.
+		// Grow slice.
+		n := v.Len();
+		if n >= v.Cap() {
+			ncap := 2*n;
+			if ncap < 4 {
+				ncap = 4;
+			}
+			new := reflect.MakeSlice(typ, n, ncap);
+			reflect.ArrayCopy(new, v);
+			v.Set(new);
+		}
+		v.SetLen(n+1);
+
+		// Recur to read element into slice.
+		if err := p.unmarshal(v.Elem(n), start); err != nil {
+			v.SetLen(n);
+			return err;
+		}
+		return nil;
+
+	case *reflect.StringValue:
+		saveData = v;
+
+	case *reflect.StructValue:
+		sv = v;
+		typ := sv.Type().(*reflect.StructType);
+		styp = typ;
+		// Assign name.
+		if f, ok := typ.FieldByName("XMLName"); ok {
+			// Validate element name.
+			if f.Tag != "" {
+				tag := f.Tag;
+				ns := "";
+				i := strings.LastIndex(tag, " ");
+				if i >= 0 {
+					ns, tag = tag[0:i], tag[i+1:len(tag)];
+				}
+				if tag != start.Name.Local {
+					return UnmarshalError("expected element type <" + tag + "> but have <" + start.Name.Local + ">");
+				}
+				if ns != "" && ns != start.Name.Space {
+					e := "expected element <" + tag + "> in name space " + ns + " but have ";
+					if start.Name.Space == "" {
+						e += "no name space";
+					} else {
+						e += start.Name.Space;
+					}
+					return UnmarshalError(e);
+				}
+			}
+
+			// Save
+			v := sv.FieldByIndex(f.Index);
+			if _, ok := v.Interface().(Name); !ok {
+				return UnmarshalError(sv.Type().String() + " field XMLName does not have type xml.Name");
+			}
+			v.(*reflect.StructValue).Set(reflect.NewValue(start.Name).(*reflect.StructValue));
+		}
+
+		// Assign attributes.
+		// Also, do we need to save character data?
+		for i, n := 0, typ.NumField(); i < n; i++ {
+			f := typ.Field(i);
+			switch f.Tag {
+			case "attr":
+				strv, ok := sv.FieldByIndex(f.Index).(*reflect.StringValue);
+				if !ok {
+					return UnmarshalError(sv.Type().String() + " field " + f.Name + " has attr tag but is not type string");
+				}
+				// Look for attribute.
+				val := "";
+				k := strings.ToLower(f.Name);
+				for _, a := range start.Attr {
+					if strings.ToLower(a.Name.Local) == k {
+						val = a.Value;
+						break;
+					}
+				}
+				strv.Set(val);
+
+			case "chardata":
+				if saveData == nil {
+					saveData = sv.FieldByIndex(f.Index);
+				}
+			}
+		}
+	}
+
+	// Find end element.
+	// Process sub-elements along the way.
+Loop:
+	for {
+		tok, err := p.Token();
+		if err != nil {
+			return err;
+		}
+		switch t := tok.(type) {
+		case StartElement:
+			// Sub-element.
+			if sv != nil {
+				k := strings.ToLower(t.Name.Local);
+				for i, n := 0, styp.NumField(); i < n; i++ {
+					f := styp.Field(i);
+					if strings.ToLower(f.Name) == k {
+						if err := p.unmarshal(sv.FieldByIndex(f.Index), &t); err != nil {
+							return err;
+						}
+						continue Loop;
+					}
+				}
+			}
+			// Not saving sub-element but still have to skip over it.
+			if err := p.skip(); err != nil {
+				return err;
+			}
+
+		case EndElement:
+			break Loop;
+
+		case CharData:
+			if saveData != nil {
+				data = bytes.Add(data, t);
+			}
+		}
+	}
+
+	// Save accumulated character data
+	if saveData != nil {
+		switch t := saveData.(type) {
+		case *reflect.StringValue:
+			t.Set(string(data));
+		case *reflect.SliceValue:
+			t.Set(reflect.NewValue(data).(*reflect.SliceValue));
+		}
+	}
+
+	return nil;
+}
+
+// Have already read a start element.
+// Read tokens until we find the end element.
+// Token is taking care of making sure the
+// end element matches the start element we saw.
+func (p *Parser) skip() os.Error {
+	for {
+		tok, err := p.Token();
+		if err != nil {
+			return err;
+		}
+		switch t := tok.(type) {
+		case StartElement:
+			if err := p.skip(); err != nil {
+				return err;
+			}
+		case EndElement:
+			return nil;
+		}
+	}
+	panic("unreachable");
+}

src/pkg/xml/read_test.go

+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml
+
+import (
+	"reflect";
+	"testing";
+)
+
+// Stripped down Atom feed data structures.
+
+func TestUnmarshalFeed(t *testing.T) {
+	var f Feed;
+	if err := Unmarshal(StringReader(rssFeedString), &f); err != nil {
+		t.Fatalf("Unmarshal: %s", err);
+	}
+	if !reflect.DeepEqual(f, rssFeed) {
+		t.Fatalf("have %#v\nwant %#v\n\n%#v", f);
+	}
+}
+
+// hget http://codereview.appspot.com/rss/mine/rsc
+const rssFeedString = `
+<?xml version="1.0" encoding="utf-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en-us"><title>Code Review - My issues</title><link href="http://codereview.appspot.com/" rel="alternate"></link><link href="http://codereview.appspot.com/rss/mine/rsc" rel="self"></link><id>http://codereview.appspot.com/</id><updated>2009-10-04T01:35:58+00:00</updated><author><name>rietveld</name></author><entry><title>rietveld: an attempt at pubsubhubbub
+</title><link href="http://codereview.appspot.com/126085" rel="alternate"></link><updated>2009-10-04T01:35:58+00:00</updated><author><name>email-address-removed</name></author><id>urn:md5:134d9179c41f806be79b3a5f7877d19a</id><summary type="html">
+  An attempt at adding pubsubhubbub support to Rietveld.
+http://code.google.com/p/pubsubhubbub
+http://code.google.com/p/rietveld/issues/detail?id=155
+
+The server side of the protocol is trivial:
+  1. add a &amp;lt;link rel=&amp;quot;hub&amp;quot; href=&amp;quot;hub-server&amp;quot;&amp;gt; tag to all
+     feeds that will be pubsubhubbubbed.
+  2. every time one of those feeds changes, tell the hub
+     with a simple POST request.
+
+I have tested this by adding debug prints to a local hub
+server and checking that the server got the right publish
+requests.
+
+I can&amp;#39;t quite get the server to work, but I think the bug
+is not in my code.  I think that the server expects to be
+able to grab the feed and see the feed&amp;#39;s actual URL in
+the link rel=&amp;quot;self&amp;quot;, but the default value for that drops
+the :port from the URL, and I cannot for the life of me
+figure out how to get the Atom generator deep inside
+django not to do that, or even where it is doing that,
+or even what code is running to generate the Atom feed.
+(I thought I knew but I added some assert False statements
+and it kept running!)
+
+Ignoring that particular problem, I would appreciate
+feedback on the right way to get the two values at
+the top of feeds.py marked NOTE(rsc).
+
+
+</summary></entry><entry><title>rietveld: correct tab handling
+</title><link href="http://codereview.appspot.com/124106" rel="alternate"></link><updated>2009-10-03T23:02:17+00:00</updated><author><name>email-address-removed</name></author><id>urn:md5:0a2a4f19bb815101f0ba2904aed7c35a</id><summary type="html">
+  This fixes the buggy tab rendering that can be seen at
+http://codereview.appspot.com/116075/diff/1/2
+
+The fundamental problem was that the tab code was
+not being told what column the text began in, so it
+didn&amp;#39;t know where to put the tab stops.  Another problem
+was that some of the code assumed that string byte
+offsets were the same as column offsets, which is only
+true if there are no tabs.
+
+In the process of fixing this, I cleaned up the arguments
+to Fold and ExpandTabs and renamed them Break and
+_ExpandTabs so that I could be sure that I found all the
+call sites.  I also wanted to verify that ExpandTabs was
+not being used from outside intra_region_diff.py.
+
+
+</summary></entry></feed>`
+
+type Feed struct {
+	XMLName Name "http://www.w3.org/2005/Atom feed";
+	Title string;
+	Id string;
+	Link []Link;
+	Updated Time;
+	Author Person;
+	Entry []Entry;
+}
+
+type Entry struct {
+	Title string;
+	Id string;
+	Link []Link;
+	Updated Time;
+	Author Person;
+	Summary Text;
+}
+
+type Link struct {
+	Rel string "attr";
+	Href string "attr";
+}
+
+type Person struct {
+	Name string;
+	URI string;
+	Email string;
+}
+
+type Text struct {
+	Type string "attr";
+	Body string "chardata";
+}
+
+type Time string
+
+var rssFeed = Feed{
+	XMLName: Name{"http://www.w3.org/2005/Atom", "feed"},
+	Title: "Code Review - My issues",
+	Link: []Link{
+		Link{Rel: "alternate", Href: "http://codereview.appspot.com/"},
+		Link{Rel: "self", Href: "http://codereview.appspot.com/rss/mine/rsc"},
+	},
+	Id: "http://codereview.appspot.com/",
+	Updated: "2009-10-04T01:35:58+00:00",
+	Author: Person{
+		Name: "rietveld"
+	},
+	Entry: []Entry{
+		Entry{
+			Title: "rietveld: an attempt at pubsubhubbub\n",
+			Link: []Link{
+				Link{Rel: "alternate", Href: "http://codereview.appspot.com/126085"},
+			},
+			Updated: "2009-10-04T01:35:58+00:00",
+			Author: Person{
+				Name: "email-address-removed"
+			},
+			Id: "urn:md5:134d9179c41f806be79b3a5f7877d19a",
+			Summary: Text{
+				Type: "html",
+				Body: `
+  An attempt at adding pubsubhubbub support to Rietveld.
+http://code.google.com/p/pubsubhubbub
+http://code.google.com/p/rietveld/issues/detail?id=155
+
+The server side of the protocol is trivial:
+  1. add a &lt;link rel=&quot;hub&quot; href=&quot;hub-server&quot;&gt; tag to all
+     feeds that will be pubsubhubbubbed.
+  2. every time one of those feeds changes, tell the hub
+     with a simple POST request.
+
+I have tested this by adding debug prints to a local hub
+server and checking that the server got the right publish
+requests.
+
+I can&#39;t quite get the server to work, but I think the bug
+is not in my code.  I think that the server expects to be
+able to grab the feed and see the feed&#39;s actual URL in
+the link rel=&quot;self&quot;, but the default value for that drops
+the :port from the URL, and I cannot for the life of me
+figure out how to get the Atom generator deep inside
+django not to do that, or even where it is doing that,
+or even what code is running to generate the Atom feed.
+(I thought I knew but I added some assert False statements
+and it kept running!)
+
+Ignoring that particular problem, I would appreciate
+feedback on the right way to get the two values at
+the top of feeds.py marked NOTE(rsc).
+
+
+`
+			},
+		},
+		Entry{
+			Title: "rietveld: correct tab handling\n",
+			Link: []Link{
+				Link{Rel: "alternate", Href: "http://codereview.appspot.com/124106"},
+			},
+			Updated: "2009-10-03T23:02:17+00:00",
+			Author: Person{
+				Name: "email-address-removed"
+			},
+			Id: "urn:md5:0a2a4f19bb815101f0ba2904aed7c35a",
+			Summary: Text{
+				Type: "html",
+				Body: `
+  This fixes the buggy tab rendering that can be seen at
+http://codereview.appspot.com/116075/diff/1/2
+
+The fundamental problem was that the tab code was
+not being told what column the text began in, so it
+didn&#39;t know where to put the tab stops.  Another problem
+was that some of the code assumed that string byte
+offsets were the same as column offsets, which is only
+true if there are no tabs.
+
+In the process of fixing this, I cleaned up the arguments
+to Fold and ExpandTabs and renamed them Break and
+_ExpandTabs so that I could be sure that I found all the
+call sites.  I also wanted to verify that ExpandTabs was
+not being used from outside intra_region_diff.py.
+
+
+`
+			}
+		},
+	}
+}