diff --git a/src/pkg/template/Makefile b/src/pkg/template/Makefile index 4915527b44..4f1e06527d 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 0000000000..e778d801da --- /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 0000000000..5bc7ff7e9f --- /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 similarity index 58% rename from src/pkg/template/template.go rename to src/pkg/template/parse.go index f481cbd1ee..b4aa5fcd2d 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 }