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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [text/] [template/] [exec.go] - Blame information for rev 747

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1 747 jeremybenn
// Copyright 2011 The Go Authors. All rights reserved.
2
// Use of this source code is governed by a BSD-style
3
// license that can be found in the LICENSE file.
4
 
5
package template
6
 
7
import (
8
        "fmt"
9
        "io"
10
        "reflect"
11
        "runtime"
12
        "sort"
13
        "strings"
14
        "text/template/parse"
15
)
16
 
17
// state represents the state of an execution. It's not part of the
18
// template so that multiple executions of the same template
19
// can execute in parallel.
20
type state struct {
21
        tmpl *Template
22
        wr   io.Writer
23
        line int        // line number for errors
24
        vars []variable // push-down stack of variable values.
25
}
26
 
27
// variable holds the dynamic value of a variable such as $, $x etc.
28
type variable struct {
29
        name  string
30
        value reflect.Value
31
}
32
 
33
// push pushes a new variable on the stack.
34
func (s *state) push(name string, value reflect.Value) {
35
        s.vars = append(s.vars, variable{name, value})
36
}
37
 
38
// mark returns the length of the variable stack.
39
func (s *state) mark() int {
40
        return len(s.vars)
41
}
42
 
43
// pop pops the variable stack up to the mark.
44
func (s *state) pop(mark int) {
45
        s.vars = s.vars[0:mark]
46
}
47
 
48
// setVar overwrites the top-nth variable on the stack. Used by range iterations.
49
func (s *state) setVar(n int, value reflect.Value) {
50
        s.vars[len(s.vars)-n].value = value
51
}
52
 
53
// varValue returns the value of the named variable.
54
func (s *state) varValue(name string) reflect.Value {
55
        for i := s.mark() - 1; i >= 0; i-- {
56
                if s.vars[i].name == name {
57
                        return s.vars[i].value
58
                }
59
        }
60
        s.errorf("undefined variable: %s", name)
61
        return zero
62
}
63
 
64
var zero reflect.Value
65
 
66
// errorf formats the error and terminates processing.
67
func (s *state) errorf(format string, args ...interface{}) {
68
        format = fmt.Sprintf("template: %s:%d: %s", s.tmpl.Name(), s.line, format)
69
        panic(fmt.Errorf(format, args...))
70
}
71
 
72
// error terminates processing.
73
func (s *state) error(err error) {
74
        s.errorf("%s", err)
75
}
76
 
77
// errRecover is the handler that turns panics into returns from the top
78
// level of Parse.
79
func errRecover(errp *error) {
80
        e := recover()
81
        if e != nil {
82
                switch err := e.(type) {
83
                case runtime.Error:
84
                        panic(e)
85
                case error:
86
                        *errp = err
87
                default:
88
                        panic(e)
89
                }
90
        }
91
}
92
 
93
// ExecuteTemplate applies the template associated with t that has the given name
94
// to the specified data object and writes the output to wr.
95
func (t *Template) ExecuteTemplate(wr io.Writer, name string, data interface{}) error {
96
        tmpl := t.tmpl[name]
97
        if tmpl == nil {
98
                return fmt.Errorf("template: no template %q associated with template %q", name, t.name)
99
        }
100
        return tmpl.Execute(wr, data)
101
}
102
 
103
// Execute applies a parsed template to the specified data object,
104
// and writes the output to wr.
105
func (t *Template) Execute(wr io.Writer, data interface{}) (err error) {
106
        defer errRecover(&err)
107
        value := reflect.ValueOf(data)
108
        state := &state{
109
                tmpl: t,
110
                wr:   wr,
111
                line: 1,
112
                vars: []variable{{"$", value}},
113
        }
114
        if t.Tree == nil || t.Root == nil {
115
                state.errorf("%q is an incomplete or empty template", t.name)
116
        }
117
        state.walk(value, t.Root)
118
        return
119
}
120
 
121
// Walk functions step through the major pieces of the template structure,
122
// generating output as they go.
123
func (s *state) walk(dot reflect.Value, n parse.Node) {
124
        switch n := n.(type) {
125
        case *parse.ActionNode:
126
                s.line = n.Line
127
                // Do not pop variables so they persist until next end.
128
                // Also, if the action declares variables, don't print the result.
129
                val := s.evalPipeline(dot, n.Pipe)
130
                if len(n.Pipe.Decl) == 0 {
131
                        s.printValue(n, val)
132
                }
133
        case *parse.IfNode:
134
                s.line = n.Line
135
                s.walkIfOrWith(parse.NodeIf, dot, n.Pipe, n.List, n.ElseList)
136
        case *parse.ListNode:
137
                for _, node := range n.Nodes {
138
                        s.walk(dot, node)
139
                }
140
        case *parse.RangeNode:
141
                s.line = n.Line
142
                s.walkRange(dot, n)
143
        case *parse.TemplateNode:
144
                s.line = n.Line
145
                s.walkTemplate(dot, n)
146
        case *parse.TextNode:
147
                if _, err := s.wr.Write(n.Text); err != nil {
148
                        s.error(err)
149
                }
150
        case *parse.WithNode:
151
                s.line = n.Line
152
                s.walkIfOrWith(parse.NodeWith, dot, n.Pipe, n.List, n.ElseList)
153
        default:
154
                s.errorf("unknown node: %s", n)
155
        }
156
}
157
 
158
// walkIfOrWith walks an 'if' or 'with' node. The two control structures
159
// are identical in behavior except that 'with' sets dot.
160
func (s *state) walkIfOrWith(typ parse.NodeType, dot reflect.Value, pipe *parse.PipeNode, list, elseList *parse.ListNode) {
161
        defer s.pop(s.mark())
162
        val := s.evalPipeline(dot, pipe)
163
        truth, ok := isTrue(val)
164
        if !ok {
165
                s.errorf("if/with can't use %v", val)
166
        }
167
        if truth {
168
                if typ == parse.NodeWith {
169
                        s.walk(val, list)
170
                } else {
171
                        s.walk(dot, list)
172
                }
173
        } else if elseList != nil {
174
                s.walk(dot, elseList)
175
        }
176
}
177
 
178
// isTrue returns whether the value is 'true', in the sense of not the zero of its type,
179
// and whether the value has a meaningful truth value.
180
func isTrue(val reflect.Value) (truth, ok bool) {
181
        if !val.IsValid() {
182
                // Something like var x interface{}, never set. It's a form of nil.
183
                return false, true
184
        }
185
        switch val.Kind() {
186
        case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
187
                truth = val.Len() > 0
188
        case reflect.Bool:
189
                truth = val.Bool()
190
        case reflect.Complex64, reflect.Complex128:
191
                truth = val.Complex() != 0
192
        case reflect.Chan, reflect.Func, reflect.Ptr, reflect.Interface:
193
                truth = !val.IsNil()
194
        case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
195
                truth = val.Int() != 0
196
        case reflect.Float32, reflect.Float64:
197
                truth = val.Float() != 0
198
        case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
199
                truth = val.Uint() != 0
200
        case reflect.Struct:
201
                truth = true // Struct values are always true.
202
        default:
203
                return
204
        }
205
        return truth, true
206
}
207
 
208
func (s *state) walkRange(dot reflect.Value, r *parse.RangeNode) {
209
        defer s.pop(s.mark())
210
        val, _ := indirect(s.evalPipeline(dot, r.Pipe))
211
        // mark top of stack before any variables in the body are pushed.
212
        mark := s.mark()
213
        oneIteration := func(index, elem reflect.Value) {
214
                // Set top var (lexically the second if there are two) to the element.
215
                if len(r.Pipe.Decl) > 0 {
216
                        s.setVar(1, elem)
217
                }
218
                // Set next var (lexically the first if there are two) to the index.
219
                if len(r.Pipe.Decl) > 1 {
220
                        s.setVar(2, index)
221
                }
222
                s.walk(elem, r.List)
223
                s.pop(mark)
224
        }
225
        switch val.Kind() {
226
        case reflect.Array, reflect.Slice:
227
                if val.Len() == 0 {
228
                        break
229
                }
230
                for i := 0; i < val.Len(); i++ {
231
                        oneIteration(reflect.ValueOf(i), val.Index(i))
232
                }
233
                return
234
        case reflect.Map:
235
                if val.Len() == 0 {
236
                        break
237
                }
238
                for _, key := range sortKeys(val.MapKeys()) {
239
                        oneIteration(key, val.MapIndex(key))
240
                }
241
                return
242
        case reflect.Chan:
243
                if val.IsNil() {
244
                        break
245
                }
246
                i := 0
247
                for ; ; i++ {
248
                        elem, ok := val.Recv()
249
                        if !ok {
250
                                break
251
                        }
252
                        oneIteration(reflect.ValueOf(i), elem)
253
                }
254
                if i == 0 {
255
                        break
256
                }
257
                return
258
        case reflect.Invalid:
259
                break // An invalid value is likely a nil map, etc. and acts like an empty map.
260
        default:
261
                s.errorf("range can't iterate over %v", val)
262
        }
263
        if r.ElseList != nil {
264
                s.walk(dot, r.ElseList)
265
        }
266
}
267
 
268
func (s *state) walkTemplate(dot reflect.Value, t *parse.TemplateNode) {
269
        tmpl := s.tmpl.tmpl[t.Name]
270
        if tmpl == nil {
271
                s.errorf("template %q not defined", t.Name)
272
        }
273
        // Variables declared by the pipeline persist.
274
        dot = s.evalPipeline(dot, t.Pipe)
275
        newState := *s
276
        newState.tmpl = tmpl
277
        // No dynamic scoping: template invocations inherit no variables.
278
        newState.vars = []variable{{"$", dot}}
279
        newState.walk(dot, tmpl.Root)
280
}
281
 
282
// Eval functions evaluate pipelines, commands, and their elements and extract
283
// values from the data structure by examining fields, calling methods, and so on.
284
// The printing of those values happens only through walk functions.
285
 
286
// evalPipeline returns the value acquired by evaluating a pipeline. If the
287
// pipeline has a variable declaration, the variable will be pushed on the
288
// stack. Callers should therefore pop the stack after they are finished
289
// executing commands depending on the pipeline value.
290
func (s *state) evalPipeline(dot reflect.Value, pipe *parse.PipeNode) (value reflect.Value) {
291
        if pipe == nil {
292
                return
293
        }
294
        for _, cmd := range pipe.Cmds {
295
                value = s.evalCommand(dot, cmd, value) // previous value is this one's final arg.
296
                // If the object has type interface{}, dig down one level to the thing inside.
297
                if value.Kind() == reflect.Interface && value.Type().NumMethod() == 0 {
298
                        value = reflect.ValueOf(value.Interface()) // lovely!
299
                }
300
        }
301
        for _, variable := range pipe.Decl {
302
                s.push(variable.Ident[0], value)
303
        }
304
        return value
305
}
306
 
307
func (s *state) notAFunction(args []parse.Node, final reflect.Value) {
308
        if len(args) > 1 || final.IsValid() {
309
                s.errorf("can't give argument to non-function %s", args[0])
310
        }
311
}
312
 
313
func (s *state) evalCommand(dot reflect.Value, cmd *parse.CommandNode, final reflect.Value) reflect.Value {
314
        firstWord := cmd.Args[0]
315
        switch n := firstWord.(type) {
316
        case *parse.FieldNode:
317
                return s.evalFieldNode(dot, n, cmd.Args, final)
318
        case *parse.IdentifierNode:
319
                // Must be a function.
320
                return s.evalFunction(dot, n.Ident, cmd.Args, final)
321
        case *parse.VariableNode:
322
                return s.evalVariableNode(dot, n, cmd.Args, final)
323
        }
324
        s.notAFunction(cmd.Args, final)
325
        switch word := firstWord.(type) {
326
        case *parse.BoolNode:
327
                return reflect.ValueOf(word.True)
328
        case *parse.DotNode:
329
                return dot
330
        case *parse.NumberNode:
331
                return s.idealConstant(word)
332
        case *parse.StringNode:
333
                return reflect.ValueOf(word.Text)
334
        }
335
        s.errorf("can't evaluate command %q", firstWord)
336
        panic("not reached")
337
}
338
 
339
// idealConstant is called to return the value of a number in a context where
340
// we don't know the type. In that case, the syntax of the number tells us
341
// its type, and we use Go rules to resolve.  Note there is no such thing as
342
// a uint ideal constant in this situation - the value must be of int type.
343
func (s *state) idealConstant(constant *parse.NumberNode) reflect.Value {
344
        // These are ideal constants but we don't know the type
345
        // and we have no context.  (If it was a method argument,
346
        // we'd know what we need.) The syntax guides us to some extent.
347
        switch {
348
        case constant.IsComplex:
349
                return reflect.ValueOf(constant.Complex128) // incontrovertible.
350
        case constant.IsFloat && strings.IndexAny(constant.Text, ".eE") >= 0:
351
                return reflect.ValueOf(constant.Float64)
352
        case constant.IsInt:
353
                n := int(constant.Int64)
354
                if int64(n) != constant.Int64 {
355
                        s.errorf("%s overflows int", constant.Text)
356
                }
357
                return reflect.ValueOf(n)
358
        case constant.IsUint:
359
                s.errorf("%s overflows int", constant.Text)
360
        }
361
        return zero
362
}
363
 
364
func (s *state) evalFieldNode(dot reflect.Value, field *parse.FieldNode, args []parse.Node, final reflect.Value) reflect.Value {
365
        return s.evalFieldChain(dot, dot, field.Ident, args, final)
366
}
367
 
368
func (s *state) evalVariableNode(dot reflect.Value, v *parse.VariableNode, args []parse.Node, final reflect.Value) reflect.Value {
369
        // $x.Field has $x as the first ident, Field as the second. Eval the var, then the fields.
370
        value := s.varValue(v.Ident[0])
371
        if len(v.Ident) == 1 {
372
                return value
373
        }
374
        return s.evalFieldChain(dot, value, v.Ident[1:], args, final)
375
}
376
 
377
// evalFieldChain evaluates .X.Y.Z possibly followed by arguments.
378
// dot is the environment in which to evaluate arguments, while
379
// receiver is the value being walked along the chain.
380
func (s *state) evalFieldChain(dot, receiver reflect.Value, ident []string, args []parse.Node, final reflect.Value) reflect.Value {
381
        n := len(ident)
382
        for i := 0; i < n-1; i++ {
383
                receiver = s.evalField(dot, ident[i], nil, zero, receiver)
384
        }
385
        // Now if it's a method, it gets the arguments.
386
        return s.evalField(dot, ident[n-1], args, final, receiver)
387
}
388
 
389
func (s *state) evalFunction(dot reflect.Value, name string, args []parse.Node, final reflect.Value) reflect.Value {
390
        function, ok := findFunction(name, s.tmpl)
391
        if !ok {
392
                s.errorf("%q is not a defined function", name)
393
        }
394
        return s.evalCall(dot, function, name, args, final)
395
}
396
 
397
// evalField evaluates an expression like (.Field) or (.Field arg1 arg2).
398
// The 'final' argument represents the return value from the preceding
399
// value of the pipeline, if any.
400
func (s *state) evalField(dot reflect.Value, fieldName string, args []parse.Node, final, receiver reflect.Value) reflect.Value {
401
        if !receiver.IsValid() {
402
                return zero
403
        }
404
        typ := receiver.Type()
405
        receiver, _ = indirect(receiver)
406
        // Unless it's an interface, need to get to a value of type *T to guarantee
407
        // we see all methods of T and *T.
408
        ptr := receiver
409
        if ptr.Kind() != reflect.Interface && ptr.CanAddr() {
410
                ptr = ptr.Addr()
411
        }
412
        if method := ptr.MethodByName(fieldName); method.IsValid() {
413
                return s.evalCall(dot, method, fieldName, args, final)
414
        }
415
        hasArgs := len(args) > 1 || final.IsValid()
416
        // It's not a method; is it a field of a struct?
417
        receiver, isNil := indirect(receiver)
418
        if receiver.Kind() == reflect.Struct {
419
                tField, ok := receiver.Type().FieldByName(fieldName)
420
                if ok {
421
                        field := receiver.FieldByIndex(tField.Index)
422
                        if hasArgs {
423
                                s.errorf("%s is not a method but has arguments", fieldName)
424
                        }
425
                        if tField.PkgPath == "" { // field is exported
426
                                return field
427
                        }
428
                }
429
        }
430
        // If it's a map, attempt to use the field name as a key.
431
        if receiver.Kind() == reflect.Map {
432
                nameVal := reflect.ValueOf(fieldName)
433
                if nameVal.Type().AssignableTo(receiver.Type().Key()) {
434
                        if hasArgs {
435
                                s.errorf("%s is not a method but has arguments", fieldName)
436
                        }
437
                        return receiver.MapIndex(nameVal)
438
                }
439
        }
440
        if isNil {
441
                s.errorf("nil pointer evaluating %s.%s", typ, fieldName)
442
        }
443
        s.errorf("can't evaluate field %s in type %s", fieldName, typ)
444
        panic("not reached")
445
}
446
 
447
var (
448
        errorType       = reflect.TypeOf((*error)(nil)).Elem()
449
        fmtStringerType = reflect.TypeOf((*fmt.Stringer)(nil)).Elem()
450
)
451
 
452
// evalCall executes a function or method call. If it's a method, fun already has the receiver bound, so
453
// it looks just like a function call.  The arg list, if non-nil, includes (in the manner of the shell), arg[0]
454
// as the function itself.
455
func (s *state) evalCall(dot, fun reflect.Value, name string, args []parse.Node, final reflect.Value) reflect.Value {
456
        if args != nil {
457
                args = args[1:] // Zeroth arg is function name/node; not passed to function.
458
        }
459
        typ := fun.Type()
460
        numIn := len(args)
461
        if final.IsValid() {
462
                numIn++
463
        }
464
        numFixed := len(args)
465
        if typ.IsVariadic() {
466
                numFixed = typ.NumIn() - 1 // last arg is the variadic one.
467
                if numIn < numFixed {
468
                        s.errorf("wrong number of args for %s: want at least %d got %d", name, typ.NumIn()-1, len(args))
469
                }
470
        } else if numIn < typ.NumIn()-1 || !typ.IsVariadic() && numIn != typ.NumIn() {
471
                s.errorf("wrong number of args for %s: want %d got %d", name, typ.NumIn(), len(args))
472
        }
473
        if !goodFunc(typ) {
474
                s.errorf("can't handle multiple results from method/function %q", name)
475
        }
476
        // Build the arg list.
477
        argv := make([]reflect.Value, numIn)
478
        // Args must be evaluated. Fixed args first.
479
        i := 0
480
        for ; i < numFixed; i++ {
481
                argv[i] = s.evalArg(dot, typ.In(i), args[i])
482
        }
483
        // Now the ... args.
484
        if typ.IsVariadic() {
485
                argType := typ.In(typ.NumIn() - 1).Elem() // Argument is a slice.
486
                for ; i < len(args); i++ {
487
                        argv[i] = s.evalArg(dot, argType, args[i])
488
                }
489
        }
490
        // Add final value if necessary.
491
        if final.IsValid() {
492
                argv[i] = final
493
        }
494
        result := fun.Call(argv)
495
        // If we have an error that is not nil, stop execution and return that error to the caller.
496
        if len(result) == 2 && !result[1].IsNil() {
497
                s.errorf("error calling %s: %s", name, result[1].Interface().(error))
498
        }
499
        return result[0]
500
}
501
 
502
// validateType guarantees that the value is valid and assignable to the type.
503
func (s *state) validateType(value reflect.Value, typ reflect.Type) reflect.Value {
504
        if !value.IsValid() {
505
                switch typ.Kind() {
506
                case reflect.Interface, reflect.Ptr, reflect.Chan, reflect.Map, reflect.Slice, reflect.Func:
507
                        // An untyped nil interface{}. Accept as a proper nil value.
508
                        value = reflect.Zero(typ)
509
                default:
510
                        s.errorf("invalid value; expected %s", typ)
511
                }
512
        }
513
        if !value.Type().AssignableTo(typ) {
514
                // Does one dereference or indirection work? We could do more, as we
515
                // do with method receivers, but that gets messy and method receivers
516
                // are much more constrained, so it makes more sense there than here.
517
                // Besides, one is almost always all you need.
518
                switch {
519
                case value.Kind() == reflect.Ptr && value.Type().Elem().AssignableTo(typ):
520
                        value = value.Elem()
521
                case reflect.PtrTo(value.Type()).AssignableTo(typ) && value.CanAddr():
522
                        value = value.Addr()
523
                default:
524
                        s.errorf("wrong type for value; expected %s; got %s", typ, value.Type())
525
                }
526
        }
527
        return value
528
}
529
 
530
func (s *state) evalArg(dot reflect.Value, typ reflect.Type, n parse.Node) reflect.Value {
531
        switch arg := n.(type) {
532
        case *parse.DotNode:
533
                return s.validateType(dot, typ)
534
        case *parse.FieldNode:
535
                return s.validateType(s.evalFieldNode(dot, arg, []parse.Node{n}, zero), typ)
536
        case *parse.VariableNode:
537
                return s.validateType(s.evalVariableNode(dot, arg, nil, zero), typ)
538
        }
539
        switch typ.Kind() {
540
        case reflect.Bool:
541
                return s.evalBool(typ, n)
542
        case reflect.Complex64, reflect.Complex128:
543
                return s.evalComplex(typ, n)
544
        case reflect.Float32, reflect.Float64:
545
                return s.evalFloat(typ, n)
546
        case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
547
                return s.evalInteger(typ, n)
548
        case reflect.Interface:
549
                if typ.NumMethod() == 0 {
550
                        return s.evalEmptyInterface(dot, n)
551
                }
552
        case reflect.String:
553
                return s.evalString(typ, n)
554
        case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
555
                return s.evalUnsignedInteger(typ, n)
556
        }
557
        s.errorf("can't handle %s for arg of type %s", n, typ)
558
        panic("not reached")
559
}
560
 
561
func (s *state) evalBool(typ reflect.Type, n parse.Node) reflect.Value {
562
        if n, ok := n.(*parse.BoolNode); ok {
563
                value := reflect.New(typ).Elem()
564
                value.SetBool(n.True)
565
                return value
566
        }
567
        s.errorf("expected bool; found %s", n)
568
        panic("not reached")
569
}
570
 
571
func (s *state) evalString(typ reflect.Type, n parse.Node) reflect.Value {
572
        if n, ok := n.(*parse.StringNode); ok {
573
                value := reflect.New(typ).Elem()
574
                value.SetString(n.Text)
575
                return value
576
        }
577
        s.errorf("expected string; found %s", n)
578
        panic("not reached")
579
}
580
 
581
func (s *state) evalInteger(typ reflect.Type, n parse.Node) reflect.Value {
582
        if n, ok := n.(*parse.NumberNode); ok && n.IsInt {
583
                value := reflect.New(typ).Elem()
584
                value.SetInt(n.Int64)
585
                return value
586
        }
587
        s.errorf("expected integer; found %s", n)
588
        panic("not reached")
589
}
590
 
591
func (s *state) evalUnsignedInteger(typ reflect.Type, n parse.Node) reflect.Value {
592
        if n, ok := n.(*parse.NumberNode); ok && n.IsUint {
593
                value := reflect.New(typ).Elem()
594
                value.SetUint(n.Uint64)
595
                return value
596
        }
597
        s.errorf("expected unsigned integer; found %s", n)
598
        panic("not reached")
599
}
600
 
601
func (s *state) evalFloat(typ reflect.Type, n parse.Node) reflect.Value {
602
        if n, ok := n.(*parse.NumberNode); ok && n.IsFloat {
603
                value := reflect.New(typ).Elem()
604
                value.SetFloat(n.Float64)
605
                return value
606
        }
607
        s.errorf("expected float; found %s", n)
608
        panic("not reached")
609
}
610
 
611
func (s *state) evalComplex(typ reflect.Type, n parse.Node) reflect.Value {
612
        if n, ok := n.(*parse.NumberNode); ok && n.IsComplex {
613
                value := reflect.New(typ).Elem()
614
                value.SetComplex(n.Complex128)
615
                return value
616
        }
617
        s.errorf("expected complex; found %s", n)
618
        panic("not reached")
619
}
620
 
621
func (s *state) evalEmptyInterface(dot reflect.Value, n parse.Node) reflect.Value {
622
        switch n := n.(type) {
623
        case *parse.BoolNode:
624
                return reflect.ValueOf(n.True)
625
        case *parse.DotNode:
626
                return dot
627
        case *parse.FieldNode:
628
                return s.evalFieldNode(dot, n, nil, zero)
629
        case *parse.IdentifierNode:
630
                return s.evalFunction(dot, n.Ident, nil, zero)
631
        case *parse.NumberNode:
632
                return s.idealConstant(n)
633
        case *parse.StringNode:
634
                return reflect.ValueOf(n.Text)
635
        case *parse.VariableNode:
636
                return s.evalVariableNode(dot, n, nil, zero)
637
        }
638
        s.errorf("can't handle assignment of %s to empty interface argument", n)
639
        panic("not reached")
640
}
641
 
642
// indirect returns the item at the end of indirection, and a bool to indicate if it's nil.
643
// We indirect through pointers and empty interfaces (only) because
644
// non-empty interfaces have methods we might need.
645
func indirect(v reflect.Value) (rv reflect.Value, isNil bool) {
646
        for ; v.Kind() == reflect.Ptr || v.Kind() == reflect.Interface; v = v.Elem() {
647
                if v.IsNil() {
648
                        return v, true
649
                }
650
                if v.Kind() == reflect.Interface && v.NumMethod() > 0 {
651
                        break
652
                }
653
        }
654
        return v, false
655
}
656
 
657
// printValue writes the textual representation of the value to the output of
658
// the template.
659
func (s *state) printValue(n parse.Node, v reflect.Value) {
660
        if v.Kind() == reflect.Ptr {
661
                v, _ = indirect(v) // fmt.Fprint handles nil.
662
        }
663
        if !v.IsValid() {
664
                fmt.Fprint(s.wr, "")
665
                return
666
        }
667
 
668
        if !v.Type().Implements(errorType) && !v.Type().Implements(fmtStringerType) {
669
                if v.CanAddr() && (reflect.PtrTo(v.Type()).Implements(errorType) || reflect.PtrTo(v.Type()).Implements(fmtStringerType)) {
670
                        v = v.Addr()
671
                } else {
672
                        switch v.Kind() {
673
                        case reflect.Chan, reflect.Func:
674
                                s.errorf("can't print %s of type %s", n, v.Type())
675
                        }
676
                }
677
        }
678
        fmt.Fprint(s.wr, v.Interface())
679
}
680
 
681
// Types to help sort the keys in a map for reproducible output.
682
 
683
type rvs []reflect.Value
684
 
685
func (x rvs) Len() int      { return len(x) }
686
func (x rvs) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
687
 
688
type rvInts struct{ rvs }
689
 
690
func (x rvInts) Less(i, j int) bool { return x.rvs[i].Int() < x.rvs[j].Int() }
691
 
692
type rvUints struct{ rvs }
693
 
694
func (x rvUints) Less(i, j int) bool { return x.rvs[i].Uint() < x.rvs[j].Uint() }
695
 
696
type rvFloats struct{ rvs }
697
 
698
func (x rvFloats) Less(i, j int) bool { return x.rvs[i].Float() < x.rvs[j].Float() }
699
 
700
type rvStrings struct{ rvs }
701
 
702
func (x rvStrings) Less(i, j int) bool { return x.rvs[i].String() < x.rvs[j].String() }
703
 
704
// sortKeys sorts (if it can) the slice of reflect.Values, which is a slice of map keys.
705
func sortKeys(v []reflect.Value) []reflect.Value {
706
        if len(v) <= 1 {
707
                return v
708
        }
709
        switch v[0].Kind() {
710
        case reflect.Float32, reflect.Float64:
711
                sort.Sort(rvFloats{v})
712
        case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
713
                sort.Sort(rvInts{v})
714
        case reflect.String:
715
                sort.Sort(rvStrings{v})
716
        case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
717
                sort.Sort(rvUints{v})
718
        }
719
        return v
720
}

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