template: rearrange the code into separate files.

The single file was getting unwieldy.
Also remove use of vector; a slice works fine - although
it's an unusual one.

R=golang-dev, r, gri
CC=golang-dev
http://codereview.appspot.com/4576042

4 files changed, 474 insertions, 453 deletions

diff --git a/src/pkg/template/Makefile b/src/pkg/template/Makefile
index 4915527b4..4f1e06527 100644
--- a/src/pkg/template/Makefile
+++ b/src/pkg/template/Makefile
@@ -6,7 +6,9 @@ include ../../Make.inc
 
 TARG=template
 GOFILES=\
+	doc.go\
+	execute.go\
 	format.go\
-	template.go\
+	parse.go\
 
 include ../../Make.pkg
diff --git a/src/pkg/template/doc.go b/src/pkg/template/doc.go
new file mode 100644
index 000000000..e778d801d
--- /dev/null
+++ b/src/pkg/template/doc.go
@@ -0,0 +1,91 @@
+// 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 template implements data-driven templates for generating textual
+	output such as HTML.
+
+	Templates are executed by applying them to a data structure.
+	Annotations in the template refer to elements of the data
+	structure (typically a field of a struct or a key in a map)
+	to control execution and derive values to be displayed.
+	The template walks the structure as it executes and the
+	"cursor" @ represents the value at the current location
+	in the structure.
+
+	Data items may be values or pointers; the interface hides the
+	indirection.
+
+	In the following, 'Field' is one of several things, according to the data.
+
+		- The name of a field of a struct (result = data.Field),
+		- The value stored in a map under that key (result = data["Field"]), or
+		- The result of invoking a niladic single-valued method with that name
+		  (result = data.Field())
+
+	If Field is a struct field or method name, it must be an exported
+	(capitalized) name.
+
+	Major constructs ({} are the default delimiters for template actions;
+	[] are the notation in this comment for optional elements):
+
+		{# comment }
+
+	A one-line comment.
+
+		{.section field} XXX [ {.or} YYY ] {.end}
+
+	Set @ to the value of the field.  It may be an explicit @
+	to stay at the same point in the data. If the field is nil
+	or empty, execute YYY; otherwise execute XXX.
+
+		{.repeated section field} XXX [ {.alternates with} ZZZ ] [ {.or} YYY ] {.end}
+
+	Like .section, but field must be an array or slice.  XXX
+	is executed for each element.  If the array is nil or empty,
+	YYY is executed instead.  If the {.alternates with} marker
+	is present, ZZZ is executed between iterations of XXX.
+
+		{field}
+		{field1 field2 ...}
+		{field|formatter}
+		{field1 field2...|formatter}
+		{field|formatter1|formatter2}
+
+	Insert the value of the fields into the output. Each field is
+	first looked for in the cursor, as in .section and .repeated.
+	If it is not found, the search continues in outer sections
+	until the top level is reached.
+
+	If the field value is a pointer, leading asterisks indicate
+	that the value to be inserted should be evaluated through the
+	pointer.  For example, if x.p is of type *int, {x.p} will
+	insert the value of the pointer but {*x.p} will insert the
+	value of the underlying integer.  If the value is nil or not a
+	pointer, asterisks have no effect.
+
+	If a formatter is specified, it must be named in the formatter
+	map passed to the template set up routines or in the default
+	set ("html","str","") and is used to process the data for
+	output.  The formatter function has signature
+		func(wr io.Writer, formatter string, data ...interface{})
+	where wr is the destination for output, data holds the field
+	values at the instantiation, and formatter is its name at
+	the invocation site.  The default formatter just concatenates
+	the string representations of the fields.
+
+	Multiple formatters separated by the pipeline character | are
+	executed sequentially, with each formatter receiving the bytes
+	emitted by the one to its left.
+
+	As well as field names, one may use literals with Go syntax.
+	Integer, floating-point, and string literals are supported.
+	Raw strings may not span newlines.
+
+	The delimiter strings get their default value, "{" and "}", from
+	JSON-template.  They may be set to any non-empty, space-free
+	string using the SetDelims method.  Their value can be printed
+	in the output using {.meta-left} and {.meta-right}.
+*/
+package template
diff --git a/src/pkg/template/execute.go b/src/pkg/template/execute.go
new file mode 100644
index 000000000..5bc7ff7e9
--- /dev/null
+++ b/src/pkg/template/execute.go
@@ -0,0 +1,346 @@
+// 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.
+
+// Code to execute a parsed template.
+
+package template
+
+import (
+	"bytes"
+	"io"
+	"reflect"
+	"strings"
+)
+
+// Internal state for executing a Template.  As we evaluate the struct,
+// the data item descends into the fields associated with sections, etc.
+// Parent is used to walk upwards to find variables higher in the tree.
+type state struct {
+	parent *state          // parent in hierarchy
+	data   reflect.Value   // the driver data for this section etc.
+	wr     io.Writer       // where to send output
+	buf    [2]bytes.Buffer // alternating buffers used when chaining formatters
+}
+
+func (parent *state) clone(data reflect.Value) *state {
+	return &state{parent: parent, data: data, wr: parent.wr}
+}
+
+// Evaluate interfaces and pointers looking for a value that can look up the name, via a
+// struct field, method, or map key, and return the result of the lookup.
+func (t *Template) lookup(st *state, v reflect.Value, name string) reflect.Value {
+	for v.IsValid() {
+		typ := v.Type()
+		if n := v.Type().NumMethod(); n > 0 {
+			for i := 0; i < n; i++ {
+				m := typ.Method(i)
+				mtyp := m.Type
+				if m.Name == name && mtyp.NumIn() == 1 && mtyp.NumOut() == 1 {
+					if !isExported(name) {
+						t.execError(st, t.linenum, "name not exported: %s in type %s", name, st.data.Type())
+					}
+					return v.Method(i).Call(nil)[0]
+				}
+			}
+		}
+		switch av := v; av.Kind() {
+		case reflect.Ptr:
+			v = av.Elem()
+		case reflect.Interface:
+			v = av.Elem()
+		case reflect.Struct:
+			if !isExported(name) {
+				t.execError(st, t.linenum, "name not exported: %s in type %s", name, st.data.Type())
+			}
+			return av.FieldByName(name)
+		case reflect.Map:
+			if v := av.MapIndex(reflect.ValueOf(name)); v.IsValid() {
+				return v
+			}
+			return reflect.Zero(typ.Elem())
+		default:
+			return reflect.Value{}
+		}
+	}
+	return v
+}
+
+// indirectPtr returns the item numLevels levels of indirection below the value.
+// It is forgiving: if the value is not a pointer, it returns it rather than giving
+// an error.  If the pointer is nil, it is returned as is.
+func indirectPtr(v reflect.Value, numLevels int) reflect.Value {
+	for i := numLevels; v.IsValid() && i > 0; i++ {
+		if p := v; p.Kind() == reflect.Ptr {
+			if p.IsNil() {
+				return v
+			}
+			v = p.Elem()
+		} else {
+			break
+		}
+	}
+	return v
+}
+
+// Walk v through pointers and interfaces, extracting the elements within.
+func indirect(v reflect.Value) reflect.Value {
+loop:
+	for v.IsValid() {
+		switch av := v; av.Kind() {
+		case reflect.Ptr:
+			v = av.Elem()
+		case reflect.Interface:
+			v = av.Elem()
+		default:
+			break loop
+		}
+	}
+	return v
+}
+
+// If the data for this template is a struct, find the named variable.
+// Names of the form a.b.c are walked down the data tree.
+// The special name "@" (the "cursor") denotes the current data.
+// The value coming in (st.data) might need indirecting to reach
+// a struct while the return value is not indirected - that is,
+// it represents the actual named field. Leading stars indicate
+// levels of indirection to be applied to the value.
+func (t *Template) findVar(st *state, s string) reflect.Value {
+	data := st.data
+	flattenedName := strings.TrimLeft(s, "*")
+	numStars := len(s) - len(flattenedName)
+	s = flattenedName
+	if s == "@" {
+		return indirectPtr(data, numStars)
+	}
+	for _, elem := range strings.Split(s, ".", -1) {
+		// Look up field; data must be a struct or map.
+		data = t.lookup(st, data, elem)
+		if !data.IsValid() {
+			return reflect.Value{}
+		}
+	}
+	return indirectPtr(data, numStars)
+}
+
+// Is there no data to look at?
+func empty(v reflect.Value) bool {
+	v = indirect(v)
+	if !v.IsValid() {
+		return true
+	}
+	switch v.Kind() {
+	case reflect.Bool:
+		return v.Bool() == false
+	case reflect.String:
+		return v.String() == ""
+	case reflect.Struct:
+		return false
+	case reflect.Map:
+		return false
+	case reflect.Array:
+		return v.Len() == 0
+	case reflect.Slice:
+		return v.Len() == 0
+	}
+	return false
+}
+
+// Look up a variable or method, up through the parent if necessary.
+func (t *Template) varValue(name string, st *state) reflect.Value {
+	field := t.findVar(st, name)
+	if !field.IsValid() {
+		if st.parent == nil {
+			t.execError(st, t.linenum, "name not found: %s in type %s", name, st.data.Type())
+		}
+		return t.varValue(name, st.parent)
+	}
+	return field
+}
+
+func (t *Template) format(wr io.Writer, fmt string, val []interface{}, v *variableElement, st *state) {
+	fn := t.formatter(fmt)
+	if fn == nil {
+		t.execError(st, v.linenum, "missing formatter %s for variable", fmt)
+	}
+	fn(wr, fmt, val...)
+}
+
+// Evaluate a variable, looking up through the parent if necessary.
+// If it has a formatter attached ({var|formatter}) run that too.
+func (t *Template) writeVariable(v *variableElement, st *state) {
+	// Resolve field names
+	val := make([]interface{}, len(v.args))
+	for i, arg := range v.args {
+		if name, ok := arg.(fieldName); ok {
+			val[i] = t.varValue(string(name), st).Interface()
+		} else {
+			val[i] = arg
+		}
+	}
+	for i, fmt := range v.fmts[:len(v.fmts)-1] {
+		b := &st.buf[i&1]
+		b.Reset()
+		t.format(b, fmt, val, v, st)
+		val = val[0:1]
+		val[0] = b.Bytes()
+	}
+	t.format(st.wr, v.fmts[len(v.fmts)-1], val, v, st)
+}
+
+// Execute element i.  Return next index to execute.
+func (t *Template) executeElement(i int, st *state) int {
+	switch elem := t.elems[i].(type) {
+	case *textElement:
+		st.wr.Write(elem.text)
+		return i + 1
+	case *literalElement:
+		st.wr.Write(elem.text)
+		return i + 1
+	case *variableElement:
+		t.writeVariable(elem, st)
+		return i + 1
+	case *sectionElement:
+		t.executeSection(elem, st)
+		return elem.end
+	case *repeatedElement:
+		t.executeRepeated(elem, st)
+		return elem.end
+	}
+	e := t.elems[i]
+	t.execError(st, 0, "internal error: bad directive in execute: %v %T\n", reflect.ValueOf(e).Interface(), e)
+	return 0
+}
+
+// Execute the template.
+func (t *Template) execute(start, end int, st *state) {
+	for i := start; i < end; {
+		i = t.executeElement(i, st)
+	}
+}
+
+// Execute a .section
+func (t *Template) executeSection(s *sectionElement, st *state) {
+	// Find driver data for this section.  It must be in the current struct.
+	field := t.varValue(s.field, st)
+	if !field.IsValid() {
+		t.execError(st, s.linenum, ".section: cannot find field %s in %s", s.field, st.data.Type())
+	}
+	st = st.clone(field)
+	start, end := s.start, s.or
+	if !empty(field) {
+		// Execute the normal block.
+		if end < 0 {
+			end = s.end
+		}
+	} else {
+		// Execute the .or block.  If it's missing, do nothing.
+		start, end = s.or, s.end
+		if start < 0 {
+			return
+		}
+	}
+	for i := start; i < end; {
+		i = t.executeElement(i, st)
+	}
+}
+
+// Return the result of calling the Iter method on v, or nil.
+func iter(v reflect.Value) reflect.Value {
+	for j := 0; j < v.Type().NumMethod(); j++ {
+		mth := v.Type().Method(j)
+		fv := v.Method(j)
+		ft := fv.Type()
+		// TODO(rsc): NumIn() should return 0 here, because ft is from a curried FuncValue.
+		if mth.Name != "Iter" || ft.NumIn() != 1 || ft.NumOut() != 1 {
+			continue
+		}
+		ct := ft.Out(0)
+		if ct.Kind() != reflect.Chan ||
+			ct.ChanDir()&reflect.RecvDir == 0 {
+			continue
+		}
+		return fv.Call(nil)[0]
+	}
+	return reflect.Value{}
+}
+
+// Execute a .repeated section
+func (t *Template) executeRepeated(r *repeatedElement, st *state) {
+	// Find driver data for this section.  It must be in the current struct.
+	field := t.varValue(r.field, st)
+	if !field.IsValid() {
+		t.execError(st, r.linenum, ".repeated: cannot find field %s in %s", r.field, st.data.Type())
+	}
+	field = indirect(field)
+
+	start, end := r.start, r.or
+	if end < 0 {
+		end = r.end
+	}
+	if r.altstart >= 0 {
+		end = r.altstart
+	}
+	first := true
+
+	// Code common to all the loops.
+	loopBody := func(newst *state) {
+		// .alternates between elements
+		if !first && r.altstart >= 0 {
+			for i := r.altstart; i < r.altend; {
+				i = t.executeElement(i, newst)
+			}
+		}
+		first = false
+		for i := start; i < end; {
+			i = t.executeElement(i, newst)
+		}
+	}
+
+	if array := field; array.Kind() == reflect.Array || array.Kind() == reflect.Slice {
+		for j := 0; j < array.Len(); j++ {
+			loopBody(st.clone(array.Index(j)))
+		}
+	} else if m := field; m.Kind() == reflect.Map {
+		for _, key := range m.MapKeys() {
+			loopBody(st.clone(m.MapIndex(key)))
+		}
+	} else if ch := iter(field); ch.IsValid() {
+		for {
+			e, ok := ch.Recv()
+			if !ok {
+				break
+			}
+			loopBody(st.clone(e))
+		}
+	} else {
+		t.execError(st, r.linenum, ".repeated: cannot repeat %s (type %s)",
+			r.field, field.Type())
+	}
+
+	if first {
+		// Empty. Execute the .or block, once.  If it's missing, do nothing.
+		start, end := r.or, r.end
+		if start >= 0 {
+			newst := st.clone(field)
+			for i := start; i < end; {
+				i = t.executeElement(i, newst)
+			}
+		}
+		return
+	}
+}
+
+// A valid delimiter must contain no space and be non-empty.
+func validDelim(d []byte) bool {
+	if len(d) == 0 {
+		return false
+	}
+	for _, c := range d {
+		if isSpace(c) {
+			return false
+		}
+	}
+	return true
+}
diff --git a/src/pkg/template/template.go b/src/pkg/template/parse.go
index f481cbd1e..b4aa5fcd2 100644
--- a/src/pkg/template/template.go
+++ b/src/pkg/template/parse.go
@@ -2,97 +2,11 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-/*
-	Package template implements data-driven templates for generating textual
-	output such as HTML.
+// Code to parse a template.
 
-	Templates are executed by applying them to a data structure.
-	Annotations in the template refer to elements of the data
-	structure (typically a field of a struct or a key in a map)
-	to control execution and derive values to be displayed.
-	The template walks the structure as it executes and the
-	"cursor" @ represents the value at the current location
-	in the structure.
-
-	Data items may be values or pointers; the interface hides the
-	indirection.
-
-	In the following, 'Field' is one of several things, according to the data.
-
-		- The name of a field of a struct (result = data.Field),
-		- The value stored in a map under that key (result = data["Field"]), or
-		- The result of invoking a niladic single-valued method with that name
-		  (result = data.Field())
-
-	If Field is a struct field or method name, it must be an exported
-	(capitalized) name.
-
-	Major constructs ({} are the default delimiters for template actions;
-	[] are the notation in this comment for optional elements):
-
-		{# comment }
-
-	A one-line comment.
-
-		{.section field} XXX [ {.or} YYY ] {.end}
-
-	Set @ to the value of the field.  It may be an explicit @
-	to stay at the same point in the data. If the field is nil
-	or empty, execute YYY; otherwise execute XXX.
-
-		{.repeated section field} XXX [ {.alternates with} ZZZ ] [ {.or} YYY ] {.end}
-
-	Like .section, but field must be an array or slice.  XXX
-	is executed for each element.  If the array is nil or empty,
-	YYY is executed instead.  If the {.alternates with} marker
-	is present, ZZZ is executed between iterations of XXX.
-
-		{field}
-		{field1 field2 ...}
-		{field|formatter}
-		{field1 field2...|formatter}
-		{field|formatter1|formatter2}
-
-	Insert the value of the fields into the output. Each field is
-	first looked for in the cursor, as in .section and .repeated.
-	If it is not found, the search continues in outer sections
-	until the top level is reached.
-
-	If the field value is a pointer, leading asterisks indicate
-	that the value to be inserted should be evaluated through the
-	pointer.  For example, if x.p is of type *int, {x.p} will
-	insert the value of the pointer but {*x.p} will insert the
-	value of the underlying integer.  If the value is nil or not a
-	pointer, asterisks have no effect.
-
-	If a formatter is specified, it must be named in the formatter
-	map passed to the template set up routines or in the default
-	set ("html","str","") and is used to process the data for
-	output.  The formatter function has signature
-		func(wr io.Writer, formatter string, data ...interface{})
-	where wr is the destination for output, data holds the field
-	values at the instantiation, and formatter is its name at
-	the invocation site.  The default formatter just concatenates
-	the string representations of the fields.
-
-	Multiple formatters separated by the pipeline character | are
-	executed sequentially, with each formatter receiving the bytes
-	emitted by the one to its left.
-
-	As well as field names, one may use literals with Go syntax.
-	Integer, floating-point, and string literals are supported.
-	Raw strings may not span newlines.
-
-	The delimiter strings get their default value, "{" and "}", from
-	JSON-template.  They may be set to any non-empty, space-free
-	string using the SetDelims method.  Their value can be printed
-	in the output using {.meta-left} and {.meta-right}.
-*/
 package template
 
 import (
-	"bytes"
-	"container/vector"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -113,6 +27,19 @@ type Error struct {
 
 func (e *Error) String() string { return fmt.Sprintf("line %d: %s", e.Line, e.Msg) }
 
+// checkError is a deferred function to turn a panic with type *Error into a plain error return.
+// Other panics are unexpected and so are re-enabled.
+func checkError(error *os.Error) {
+	if v := recover(); v != nil {
+		if e, ok := v.(*Error); ok {
+			*error = e
+		} else {
+			// runtime errors should crash
+			panic(v)
+		}
+	}
+}
+
 // Most of the literals are aces.
 var lbrace = []byte{'{'}
 var rbrace = []byte{'}'}
@@ -192,21 +119,7 @@ type Template struct {
 	p              int    // position in buf
 	linenum        int    // position in input
 	// Parsed results:
-	elems *vector.Vector
-}
-
-// Internal state for executing a Template.  As we evaluate the struct,
-// the data item descends into the fields associated with sections, etc.
-// Parent is used to walk upwards to find variables higher in the tree.
-type state struct {
-	parent *state          // parent in hierarchy
-	data   reflect.Value   // the driver data for this section etc.
-	wr     io.Writer       // where to send output
-	buf    [2]bytes.Buffer // alternating buffers used when chaining formatters
-}
-
-func (parent *state) clone(data reflect.Value) *state {
-	return &state{parent: parent, data: data, wr: parent.wr}
+	elems []interface{}
 }
 
 // New creates a new template with the specified formatter map (which
@@ -216,7 +129,7 @@ func New(fmap FormatterMap) *Template {
 	t.fmap = fmap
 	t.ldelim = lbrace
 	t.rdelim = rbrace
-	t.elems = new(vector.Vector)
+	t.elems = make([]interface{}, 0, 16)
 	return t
 }
 
@@ -583,24 +496,24 @@ func (t *Template) parseSimple(item []byte) (done bool, tok int, w []string) {
 	case tokComment:
 		return
 	case tokText:
-		t.elems.Push(&textElement{item})
+		t.elems = append(t.elems, &textElement{item})
 		return
 	case tokLiteral:
 		switch w[0] {
 		case ".meta-left":
-			t.elems.Push(&literalElement{t.ldelim})
+			t.elems = append(t.elems, &literalElement{t.ldelim})
 		case ".meta-right":
-			t.elems.Push(&literalElement{t.rdelim})
+			t.elems = append(t.elems, &literalElement{t.rdelim})
 		case ".space":
-			t.elems.Push(&literalElement{space})
+			t.elems = append(t.elems, &literalElement{space})
 		case ".tab":
-			t.elems.Push(&literalElement{tab})
+			t.elems = append(t.elems, &literalElement{tab})
 		default:
 			t.parseError("internal error: unknown literal: %s", w[0])
 		}
 		return
 	case tokVariable:
-		t.elems.Push(t.newVariable(w))
+		t.elems = append(t.elems, t.newVariable(w))
 		return
 	}
 	return false, tok, w
@@ -610,11 +523,11 @@ func (t *Template) parseSimple(item []byte) (done bool, tok int, w []string) {
 
 func (t *Template) parseRepeated(words []string) *repeatedElement {
 	r := new(repeatedElement)
-	t.elems.Push(r)
+	t.elems = append(t.elems, r)
 	r.linenum = t.linenum
 	r.field = words[2]
 	// Scan section, collecting true and false (.or) blocks.
-	r.start = t.elems.Len()
+	r.start = len(t.elems)
 	r.or = -1
 	r.altstart = -1
 	r.altend = -1
@@ -637,8 +550,8 @@ Loop:
 				t.parseError("extra .or in .repeated section")
 				break Loop
 			}
-			r.altend = t.elems.Len()
-			r.or = t.elems.Len()
+			r.altend = len(t.elems)
+			r.or = len(t.elems)
 		case tokSection:
 			t.parseSection(w)
 		case tokRepeated:
@@ -652,26 +565,26 @@ Loop:
 				t.parseError(".alternates inside .or block in .repeated section")
 				break Loop
 			}
-			r.altstart = t.elems.Len()
+			r.altstart = len(t.elems)
 		default:
 			t.parseError("internal error: unknown repeated section item: %s", item)
 			break Loop
 		}
 	}
 	if r.altend < 0 {
-		r.altend = t.elems.Len()
+		r.altend = len(t.elems)
 	}
-	r.end = t.elems.Len()
+	r.end = len(t.elems)
 	return r
 }
 
 func (t *Template) parseSection(words []string) *sectionElement {
 	s := new(sectionElement)
-	t.elems.Push(s)
+	t.elems = append(t.elems, s)
 	s.linenum = t.linenum
 	s.field = words[1]
 	// Scan section, collecting true and false (.or) blocks.
-	s.start = t.elems.Len()
+	s.start = len(t.elems)
 	s.or = -1
 Loop:
 	for {
@@ -692,7 +605,7 @@ Loop:
 				t.parseError("extra .or in .section")
 				break Loop
 			}
-			s.or = t.elems.Len()
+			s.or = len(t.elems)
 		case tokSection:
 			t.parseSection(w)
 		case tokRepeated:
@@ -703,7 +616,7 @@ Loop:
 			t.parseError("internal error: unknown section item: %s", item)
 		}
 	}
-	s.end = t.elems.Len()
+	s.end = len(t.elems)
 	return s
 }
 
@@ -732,337 +645,6 @@ func (t *Template) parse() {
 
 // -- Execution
 
-// Evaluate interfaces and pointers looking for a value that can look up the name, via a
-// struct field, method, or map key, and return the result of the lookup.
-func (t *Template) lookup(st *state, v reflect.Value, name string) reflect.Value {
-	for v.IsValid() {
-		typ := v.Type()
-		if n := v.Type().NumMethod(); n > 0 {
-			for i := 0; i < n; i++ {
-				m := typ.Method(i)
-				mtyp := m.Type
-				if m.Name == name && mtyp.NumIn() == 1 && mtyp.NumOut() == 1 {
-					if !isExported(name) {
-						t.execError(st, t.linenum, "name not exported: %s in type %s", name, st.data.Type())
-					}
-					return v.Method(i).Call(nil)[0]
-				}
-			}
-		}
-		switch av := v; av.Kind() {
-		case reflect.Ptr:
-			v = av.Elem()
-		case reflect.Interface:
-			v = av.Elem()
-		case reflect.Struct:
-			if !isExported(name) {
-				t.execError(st, t.linenum, "name not exported: %s in type %s", name, st.data.Type())
-			}
-			return av.FieldByName(name)
-		case reflect.Map:
-			if v := av.MapIndex(reflect.ValueOf(name)); v.IsValid() {
-				return v
-			}
-			return reflect.Zero(typ.Elem())
-		default:
-			return reflect.Value{}
-		}
-	}
-	return v
-}
-
-// indirectPtr returns the item numLevels levels of indirection below the value.
-// It is forgiving: if the value is not a pointer, it returns it rather than giving
-// an error.  If the pointer is nil, it is returned as is.
-func indirectPtr(v reflect.Value, numLevels int) reflect.Value {
-	for i := numLevels; v.IsValid() && i > 0; i++ {
-		if p := v; p.Kind() == reflect.Ptr {
-			if p.IsNil() {
-				return v
-			}
-			v = p.Elem()
-		} else {
-			break
-		}
-	}
-	return v
-}
-
-// Walk v through pointers and interfaces, extracting the elements within.
-func indirect(v reflect.Value) reflect.Value {
-loop:
-	for v.IsValid() {
-		switch av := v; av.Kind() {
-		case reflect.Ptr:
-			v = av.Elem()
-		case reflect.Interface:
-			v = av.Elem()
-		default:
-			break loop
-		}
-	}
-	return v
-}
-
-// If the data for this template is a struct, find the named variable.
-// Names of the form a.b.c are walked down the data tree.
-// The special name "@" (the "cursor") denotes the current data.
-// The value coming in (st.data) might need indirecting to reach
-// a struct while the return value is not indirected - that is,
-// it represents the actual named field. Leading stars indicate
-// levels of indirection to be applied to the value.
-func (t *Template) findVar(st *state, s string) reflect.Value {
-	data := st.data
-	flattenedName := strings.TrimLeft(s, "*")
-	numStars := len(s) - len(flattenedName)
-	s = flattenedName
-	if s == "@" {
-		return indirectPtr(data, numStars)
-	}
-	for _, elem := range strings.Split(s, ".", -1) {
-		// Look up field; data must be a struct or map.
-		data = t.lookup(st, data, elem)
-		if !data.IsValid() {
-			return reflect.Value{}
-		}
-	}
-	return indirectPtr(data, numStars)
-}
-
-// Is there no data to look at?
-func empty(v reflect.Value) bool {
-	v = indirect(v)
-	if !v.IsValid() {
-		return true
-	}
-	switch v.Kind() {
-	case reflect.Bool:
-		return v.Bool() == false
-	case reflect.String:
-		return v.String() == ""
-	case reflect.Struct:
-		return false
-	case reflect.Map:
-		return false
-	case reflect.Array:
-		return v.Len() == 0
-	case reflect.Slice:
-		return v.Len() == 0
-	}
-	return false
-}
-
-// Look up a variable or method, up through the parent if necessary.
-func (t *Template) varValue(name string, st *state) reflect.Value {
-	field := t.findVar(st, name)
-	if !field.IsValid() {
-		if st.parent == nil {
-			t.execError(st, t.linenum, "name not found: %s in type %s", name, st.data.Type())
-		}
-		return t.varValue(name, st.parent)
-	}
-	return field
-}
-
-func (t *Template) format(wr io.Writer, fmt string, val []interface{}, v *variableElement, st *state) {
-	fn := t.formatter(fmt)
-	if fn == nil {
-		t.execError(st, v.linenum, "missing formatter %s for variable", fmt)
-	}
-	fn(wr, fmt, val...)
-}
-
-// Evaluate a variable, looking up through the parent if necessary.
-// If it has a formatter attached ({var|formatter}) run that too.
-func (t *Template) writeVariable(v *variableElement, st *state) {
-	// Resolve field names
-	val := make([]interface{}, len(v.args))
-	for i, arg := range v.args {
-		if name, ok := arg.(fieldName); ok {
-			val[i] = t.varValue(string(name), st).Interface()
-		} else {
-			val[i] = arg
-		}
-	}
-	for i, fmt := range v.fmts[:len(v.fmts)-1] {
-		b := &st.buf[i&1]
-		b.Reset()
-		t.format(b, fmt, val, v, st)
-		val = val[0:1]
-		val[0] = b.Bytes()
-	}
-	t.format(st.wr, v.fmts[len(v.fmts)-1], val, v, st)
-}
-
-// Execute element i.  Return next index to execute.
-func (t *Template) executeElement(i int, st *state) int {
-	switch elem := t.elems.At(i).(type) {
-	case *textElement:
-		st.wr.Write(elem.text)
-		return i + 1
-	case *literalElement:
-		st.wr.Write(elem.text)
-		return i + 1
-	case *variableElement:
-		t.writeVariable(elem, st)
-		return i + 1
-	case *sectionElement:
-		t.executeSection(elem, st)
-		return elem.end
-	case *repeatedElement:
-		t.executeRepeated(elem, st)
-		return elem.end
-	}
-	e := t.elems.At(i)
-	t.execError(st, 0, "internal error: bad directive in execute: %v %T\n", reflect.ValueOf(e).Interface(), e)
-	return 0
-}
-
-// Execute the template.
-func (t *Template) execute(start, end int, st *state) {
-	for i := start; i < end; {
-		i = t.executeElement(i, st)
-	}
-}
-
-// Execute a .section
-func (t *Template) executeSection(s *sectionElement, st *state) {
-	// Find driver data for this section.  It must be in the current struct.
-	field := t.varValue(s.field, st)
-	if !field.IsValid() {
-		t.execError(st, s.linenum, ".section: cannot find field %s in %s", s.field, st.data.Type())
-	}
-	st = st.clone(field)
-	start, end := s.start, s.or
-	if !empty(field) {
-		// Execute the normal block.
-		if end < 0 {
-			end = s.end
-		}
-	} else {
-		// Execute the .or block.  If it's missing, do nothing.
-		start, end = s.or, s.end
-		if start < 0 {
-			return
-		}
-	}
-	for i := start; i < end; {
-		i = t.executeElement(i, st)
-	}
-}
-
-// Return the result of calling the Iter method on v, or nil.
-func iter(v reflect.Value) reflect.Value {
-	for j := 0; j < v.Type().NumMethod(); j++ {
-		mth := v.Type().Method(j)
-		fv := v.Method(j)
-		ft := fv.Type()
-		// TODO(rsc): NumIn() should return 0 here, because ft is from a curried FuncValue.
-		if mth.Name != "Iter" || ft.NumIn() != 1 || ft.NumOut() != 1 {
-			continue
-		}
-		ct := ft.Out(0)
-		if ct.Kind() != reflect.Chan ||
-			ct.ChanDir()&reflect.RecvDir == 0 {
-			continue
-		}
-		return fv.Call(nil)[0]
-	}
-	return reflect.Value{}
-}
-
-// Execute a .repeated section
-func (t *Template) executeRepeated(r *repeatedElement, st *state) {
-	// Find driver data for this section.  It must be in the current struct.
-	field := t.varValue(r.field, st)
-	if !field.IsValid() {
-		t.execError(st, r.linenum, ".repeated: cannot find field %s in %s", r.field, st.data.Type())
-	}
-	field = indirect(field)
-
-	start, end := r.start, r.or
-	if end < 0 {
-		end = r.end
-	}
-	if r.altstart >= 0 {
-		end = r.altstart
-	}
-	first := true
-
-	// Code common to all the loops.
-	loopBody := func(newst *state) {
-		// .alternates between elements
-		if !first && r.altstart >= 0 {
-			for i := r.altstart; i < r.altend; {
-				i = t.executeElement(i, newst)
-			}
-		}
-		first = false
-		for i := start; i < end; {
-			i = t.executeElement(i, newst)
-		}
-	}
-
-	if array := field; array.Kind() == reflect.Array || array.Kind() == reflect.Slice {
-		for j := 0; j < array.Len(); j++ {
-			loopBody(st.clone(array.Index(j)))
-		}
-	} else if m := field; m.Kind() == reflect.Map {
-		for _, key := range m.MapKeys() {
-			loopBody(st.clone(m.MapIndex(key)))
-		}
-	} else if ch := iter(field); ch.IsValid() {
-		for {
-			e, ok := ch.Recv()
-			if !ok {
-				break
-			}
-			loopBody(st.clone(e))
-		}
-	} else {
-		t.execError(st, r.linenum, ".repeated: cannot repeat %s (type %s)",
-			r.field, field.Type())
-	}
-
-	if first {
-		// Empty. Execute the .or block, once.  If it's missing, do nothing.
-		start, end := r.or, r.end
-		if start >= 0 {
-			newst := st.clone(field)
-			for i := start; i < end; {
-				i = t.executeElement(i, newst)
-			}
-		}
-		return
-	}
-}
-
-// A valid delimiter must contain no space and be non-empty.
-func validDelim(d []byte) bool {
-	if len(d) == 0 {
-		return false
-	}
-	for _, c := range d {
-		if isSpace(c) {
-			return false
-		}
-	}
-	return true
-}
-
-// checkError is a deferred function to turn a panic with type *Error into a plain error return.
-// Other panics are unexpected and so are re-enabled.
-func checkError(error *os.Error) {
-	if v := recover(); v != nil {
-		if e, ok := v.(*Error); ok {
-			*error = e
-		} else {
-			// runtime errors should crash
-			panic(v)
-		}
-	}
-}
-
 // -- Public interface
 
 // Parse initializes a Template by parsing its definition.  The string
@@ -1100,7 +682,7 @@ func (t *Template) Execute(wr io.Writer, data interface{}) (err os.Error) {
 	val := reflect.ValueOf(data)
 	defer checkError(&err)
 	t.p = 0
-	t.execute(0, t.elems.Len(), &state{parent: nil, data: val, wr: wr})
+	t.execute(0, len(t.elems), &state{parent: nil, data: val, wr: wr})
 	return nil
 }