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599 lines
14 KiB
599 lines
14 KiB
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package template
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import (
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"bytes"
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"errors"
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"fmt"
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"io"
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"net/url"
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"reflect"
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"strings"
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"unicode"
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"unicode/utf8"
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)
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// FuncMap is the type of the map defining the mapping from names to functions.
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// Each function must have either a single return value, or two return values of
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// which the second has type error. In that case, if the second (error)
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// return value evaluates to non-nil during execution, execution terminates and
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// Execute returns that error.
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type FuncMap map[string]interface{}
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var builtins = FuncMap{
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"and": and,
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"call": call,
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"html": HTMLEscaper,
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"index": index,
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"js": JSEscaper,
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"len": length,
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"not": not,
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"or": or,
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"print": fmt.Sprint,
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"printf": fmt.Sprintf,
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"println": fmt.Sprintln,
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"urlquery": URLQueryEscaper,
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// Comparisons
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"eq": eq, // ==
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"ge": ge, // >=
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"gt": gt, // >
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"le": le, // <=
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"lt": lt, // <
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"ne": ne, // !=
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}
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var builtinFuncs = createValueFuncs(builtins)
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// createValueFuncs turns a FuncMap into a map[string]reflect.Value
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func createValueFuncs(funcMap FuncMap) map[string]reflect.Value {
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m := make(map[string]reflect.Value)
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addValueFuncs(m, funcMap)
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return m
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}
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// addValueFuncs adds to values the functions in funcs, converting them to reflect.Values.
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func addValueFuncs(out map[string]reflect.Value, in FuncMap) {
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for name, fn := range in {
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v := reflect.ValueOf(fn)
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if v.Kind() != reflect.Func {
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panic("value for " + name + " not a function")
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}
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if !goodFunc(v.Type()) {
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panic(fmt.Errorf("can't install method/function %q with %d results", name, v.Type().NumOut()))
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}
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out[name] = v
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}
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}
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// addFuncs adds to values the functions in funcs. It does no checking of the input -
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// call addValueFuncs first.
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func addFuncs(out, in FuncMap) {
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for name, fn := range in {
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out[name] = fn
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}
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}
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// goodFunc checks that the function or method has the right result signature.
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func goodFunc(typ reflect.Type) bool {
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// We allow functions with 1 result or 2 results where the second is an error.
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switch {
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case typ.NumOut() == 1:
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return true
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case typ.NumOut() == 2 && typ.Out(1) == errorType:
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return true
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}
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return false
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}
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// findFunction looks for a function in the template, and global map.
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func findFunction(name string, tmpl *Template) (reflect.Value, bool) {
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if tmpl != nil && tmpl.common != nil {
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if fn := tmpl.execFuncs[name]; fn.IsValid() {
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return fn, true
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}
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}
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if fn := builtinFuncs[name]; fn.IsValid() {
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return fn, true
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}
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return reflect.Value{}, false
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}
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// Indexing.
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// index returns the result of indexing its first argument by the following
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// arguments. Thus "index x 1 2 3" is, in Go syntax, x[1][2][3]. Each
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// indexed item must be a map, slice, or array.
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func index(item interface{}, indices ...interface{}) (interface{}, error) {
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v := reflect.ValueOf(item)
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for _, i := range indices {
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index := reflect.ValueOf(i)
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var isNil bool
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if v, isNil = indirect(v); isNil {
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return nil, fmt.Errorf("index of nil pointer")
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}
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switch v.Kind() {
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case reflect.Array, reflect.Slice, reflect.String:
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var x int64
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switch index.Kind() {
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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x = index.Int()
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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x = int64(index.Uint())
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default:
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return nil, fmt.Errorf("cannot index slice/array with type %s", index.Type())
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}
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if x < 0 || x >= int64(v.Len()) {
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return nil, fmt.Errorf("index out of range: %d", x)
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}
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v = v.Index(int(x))
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case reflect.Map:
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if !index.IsValid() {
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index = reflect.Zero(v.Type().Key())
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}
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if !index.Type().AssignableTo(v.Type().Key()) {
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return nil, fmt.Errorf("%s is not index type for %s", index.Type(), v.Type())
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}
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if x := v.MapIndex(index); x.IsValid() {
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v = x
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} else {
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v = reflect.Zero(v.Type().Elem())
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}
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default:
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return nil, fmt.Errorf("can't index item of type %s", v.Type())
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}
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}
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return v.Interface(), nil
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}
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// Length
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// length returns the length of the item, with an error if it has no defined length.
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func length(item interface{}) (int, error) {
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v, isNil := indirect(reflect.ValueOf(item))
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if isNil {
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return 0, fmt.Errorf("len of nil pointer")
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}
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switch v.Kind() {
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case reflect.Array, reflect.Chan, reflect.Map, reflect.Slice, reflect.String:
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return v.Len(), nil
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}
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return 0, fmt.Errorf("len of type %s", v.Type())
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}
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// Function invocation
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// call returns the result of evaluating the first argument as a function.
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// The function must return 1 result, or 2 results, the second of which is an error.
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func call(fn interface{}, args ...interface{}) (interface{}, error) {
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v := reflect.ValueOf(fn)
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typ := v.Type()
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if typ.Kind() != reflect.Func {
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return nil, fmt.Errorf("non-function of type %s", typ)
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}
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if !goodFunc(typ) {
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return nil, fmt.Errorf("function called with %d args; should be 1 or 2", typ.NumOut())
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}
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numIn := typ.NumIn()
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var dddType reflect.Type
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if typ.IsVariadic() {
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if len(args) < numIn-1 {
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return nil, fmt.Errorf("wrong number of args: got %d want at least %d", len(args), numIn-1)
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}
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dddType = typ.In(numIn - 1).Elem()
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} else {
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if len(args) != numIn {
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return nil, fmt.Errorf("wrong number of args: got %d want %d", len(args), numIn)
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}
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}
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argv := make([]reflect.Value, len(args))
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for i, arg := range args {
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value := reflect.ValueOf(arg)
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// Compute the expected type. Clumsy because of variadics.
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var argType reflect.Type
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if !typ.IsVariadic() || i < numIn-1 {
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argType = typ.In(i)
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} else {
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argType = dddType
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}
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if !value.IsValid() && canBeNil(argType) {
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value = reflect.Zero(argType)
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}
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if !value.Type().AssignableTo(argType) {
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return nil, fmt.Errorf("arg %d has type %s; should be %s", i, value.Type(), argType)
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}
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argv[i] = value
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}
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result := v.Call(argv)
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if len(result) == 2 && !result[1].IsNil() {
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return result[0].Interface(), result[1].Interface().(error)
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}
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return result[0].Interface(), nil
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}
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// Boolean logic.
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func truth(a interface{}) bool {
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t, _ := isTrue(reflect.ValueOf(a))
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return t
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}
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// and computes the Boolean AND of its arguments, returning
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// the first false argument it encounters, or the last argument.
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func and(arg0 interface{}, args ...interface{}) interface{} {
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if !truth(arg0) {
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return arg0
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}
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for i := range args {
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arg0 = args[i]
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if !truth(arg0) {
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break
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}
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}
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return arg0
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}
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// or computes the Boolean OR of its arguments, returning
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// the first true argument it encounters, or the last argument.
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func or(arg0 interface{}, args ...interface{}) interface{} {
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if truth(arg0) {
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return arg0
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}
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for i := range args {
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arg0 = args[i]
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if truth(arg0) {
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break
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}
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}
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return arg0
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}
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// not returns the Boolean negation of its argument.
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func not(arg interface{}) (truth bool) {
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truth, _ = isTrue(reflect.ValueOf(arg))
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return !truth
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}
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// Comparison.
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// TODO: Perhaps allow comparison between signed and unsigned integers.
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var (
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errBadComparisonType = errors.New("invalid type for comparison")
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errBadComparison = errors.New("incompatible types for comparison")
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errNoComparison = errors.New("missing argument for comparison")
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)
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type kind int
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const (
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invalidKind kind = iota
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boolKind
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complexKind
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intKind
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floatKind
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integerKind
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stringKind
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uintKind
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)
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func basicKind(v reflect.Value) (kind, error) {
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switch v.Kind() {
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case reflect.Bool:
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return boolKind, nil
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return intKind, nil
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return uintKind, nil
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case reflect.Float32, reflect.Float64:
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return floatKind, nil
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case reflect.Complex64, reflect.Complex128:
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return complexKind, nil
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case reflect.String:
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return stringKind, nil
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}
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return invalidKind, errBadComparisonType
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}
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// eq evaluates the comparison a == b || a == c || ...
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func eq(arg1 interface{}, arg2 ...interface{}) (bool, error) {
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v1 := reflect.ValueOf(arg1)
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k1, err := basicKind(v1)
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if err != nil {
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return false, err
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}
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if len(arg2) == 0 {
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return false, errNoComparison
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}
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for _, arg := range arg2 {
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v2 := reflect.ValueOf(arg)
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k2, err := basicKind(v2)
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if err != nil {
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return false, err
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}
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truth := false
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if k1 != k2 {
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// Special case: Can compare integer values regardless of type's sign.
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switch {
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case k1 == intKind && k2 == uintKind:
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truth = v1.Int() >= 0 && uint64(v1.Int()) == v2.Uint()
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case k1 == uintKind && k2 == intKind:
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truth = v2.Int() >= 0 && v1.Uint() == uint64(v2.Int())
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default:
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return false, errBadComparison
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}
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} else {
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switch k1 {
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case boolKind:
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truth = v1.Bool() == v2.Bool()
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case complexKind:
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truth = v1.Complex() == v2.Complex()
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case floatKind:
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truth = v1.Float() == v2.Float()
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case intKind:
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truth = v1.Int() == v2.Int()
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case stringKind:
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truth = v1.String() == v2.String()
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case uintKind:
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truth = v1.Uint() == v2.Uint()
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default:
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panic("invalid kind")
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}
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}
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if truth {
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return true, nil
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}
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}
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return false, nil
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}
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// ne evaluates the comparison a != b.
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func ne(arg1, arg2 interface{}) (bool, error) {
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// != is the inverse of ==.
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equal, err := eq(arg1, arg2)
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return !equal, err
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}
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// lt evaluates the comparison a < b.
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func lt(arg1, arg2 interface{}) (bool, error) {
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v1 := reflect.ValueOf(arg1)
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k1, err := basicKind(v1)
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if err != nil {
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return false, err
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}
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v2 := reflect.ValueOf(arg2)
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k2, err := basicKind(v2)
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if err != nil {
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return false, err
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}
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truth := false
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if k1 != k2 {
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// Special case: Can compare integer values regardless of type's sign.
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switch {
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case k1 == intKind && k2 == uintKind:
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truth = v1.Int() < 0 || uint64(v1.Int()) < v2.Uint()
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case k1 == uintKind && k2 == intKind:
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truth = v2.Int() >= 0 && v1.Uint() < uint64(v2.Int())
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default:
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return false, errBadComparison
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}
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} else {
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switch k1 {
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case boolKind, complexKind:
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return false, errBadComparisonType
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case floatKind:
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truth = v1.Float() < v2.Float()
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case intKind:
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truth = v1.Int() < v2.Int()
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case stringKind:
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truth = v1.String() < v2.String()
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case uintKind:
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truth = v1.Uint() < v2.Uint()
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default:
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panic("invalid kind")
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}
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}
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return truth, nil
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}
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// le evaluates the comparison <= b.
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func le(arg1, arg2 interface{}) (bool, error) {
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// <= is < or ==.
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lessThan, err := lt(arg1, arg2)
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if lessThan || err != nil {
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return lessThan, err
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}
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return eq(arg1, arg2)
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}
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// gt evaluates the comparison a > b.
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func gt(arg1, arg2 interface{}) (bool, error) {
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// > is the inverse of <=.
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lessOrEqual, err := le(arg1, arg2)
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if err != nil {
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return false, err
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}
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return !lessOrEqual, nil
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}
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// ge evaluates the comparison a >= b.
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func ge(arg1, arg2 interface{}) (bool, error) {
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// >= is the inverse of <.
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lessThan, err := lt(arg1, arg2)
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if err != nil {
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return false, err
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}
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return !lessThan, nil
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}
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// HTML escaping.
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var (
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htmlQuot = []byte(""") // shorter than """
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htmlApos = []byte("'") // shorter than "'" and apos was not in HTML until HTML5
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htmlAmp = []byte("&")
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htmlLt = []byte("<")
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htmlGt = []byte(">")
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)
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// HTMLEscape writes to w the escaped HTML equivalent of the plain text data b.
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func HTMLEscape(w io.Writer, b []byte) {
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last := 0
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for i, c := range b {
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var html []byte
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switch c {
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case '"':
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html = htmlQuot
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case '\'':
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html = htmlApos
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case '&':
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html = htmlAmp
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case '<':
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html = htmlLt
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case '>':
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html = htmlGt
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default:
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continue
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}
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w.Write(b[last:i])
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w.Write(html)
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last = i + 1
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}
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w.Write(b[last:])
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}
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// HTMLEscapeString returns the escaped HTML equivalent of the plain text data s.
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func HTMLEscapeString(s string) string {
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// Avoid allocation if we can.
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if strings.IndexAny(s, `'"&<>`) < 0 {
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return s
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}
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var b bytes.Buffer
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HTMLEscape(&b, []byte(s))
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return b.String()
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}
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// HTMLEscaper returns the escaped HTML equivalent of the textual
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// representation of its arguments.
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func HTMLEscaper(args ...interface{}) string {
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return HTMLEscapeString(evalArgs(args))
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}
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// JavaScript escaping.
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var (
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jsLowUni = []byte(`\u00`)
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hex = []byte("0123456789ABCDEF")
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jsBackslash = []byte(`\\`)
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jsApos = []byte(`\'`)
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jsQuot = []byte(`\"`)
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jsLt = []byte(`\x3C`)
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jsGt = []byte(`\x3E`)
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)
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// JSEscape writes to w the escaped JavaScript equivalent of the plain text data b.
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func JSEscape(w io.Writer, b []byte) {
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last := 0
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for i := 0; i < len(b); i++ {
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c := b[i]
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if !jsIsSpecial(rune(c)) {
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// fast path: nothing to do
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continue
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}
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w.Write(b[last:i])
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if c < utf8.RuneSelf {
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// Quotes, slashes and angle brackets get quoted.
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// Control characters get written as \u00XX.
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switch c {
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case '\\':
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w.Write(jsBackslash)
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case '\'':
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w.Write(jsApos)
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case '"':
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w.Write(jsQuot)
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case '<':
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w.Write(jsLt)
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case '>':
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w.Write(jsGt)
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default:
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w.Write(jsLowUni)
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t, b := c>>4, c&0x0f
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w.Write(hex[t : t+1])
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w.Write(hex[b : b+1])
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}
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} else {
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// Unicode rune.
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r, size := utf8.DecodeRune(b[i:])
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if unicode.IsPrint(r) {
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w.Write(b[i : i+size])
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} else {
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fmt.Fprintf(w, "\\u%04X", r)
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}
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i += size - 1
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}
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last = i + 1
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}
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w.Write(b[last:])
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}
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// JSEscapeString returns the escaped JavaScript equivalent of the plain text data s.
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|
func JSEscapeString(s string) string {
|
|
// Avoid allocation if we can.
|
|
if strings.IndexFunc(s, jsIsSpecial) < 0 {
|
|
return s
|
|
}
|
|
var b bytes.Buffer
|
|
JSEscape(&b, []byte(s))
|
|
return b.String()
|
|
}
|
|
|
|
func jsIsSpecial(r rune) bool {
|
|
switch r {
|
|
case '\\', '\'', '"', '<', '>':
|
|
return true
|
|
}
|
|
return r < ' ' || utf8.RuneSelf <= r
|
|
}
|
|
|
|
// JSEscaper returns the escaped JavaScript equivalent of the textual
|
|
// representation of its arguments.
|
|
func JSEscaper(args ...interface{}) string {
|
|
return JSEscapeString(evalArgs(args))
|
|
}
|
|
|
|
// URLQueryEscaper returns the escaped value of the textual representation of
|
|
// its arguments in a form suitable for embedding in a URL query.
|
|
func URLQueryEscaper(args ...interface{}) string {
|
|
return url.QueryEscape(evalArgs(args))
|
|
}
|
|
|
|
// evalArgs formats the list of arguments into a string. It is therefore equivalent to
|
|
// fmt.Sprint(args...)
|
|
// except that each argument is indirected (if a pointer), as required,
|
|
// using the same rules as the default string evaluation during template
|
|
// execution.
|
|
func evalArgs(args []interface{}) string {
|
|
ok := false
|
|
var s string
|
|
// Fast path for simple common case.
|
|
if len(args) == 1 {
|
|
s, ok = args[0].(string)
|
|
}
|
|
if !ok {
|
|
for i, arg := range args {
|
|
a, ok := printableValue(reflect.ValueOf(arg))
|
|
if ok {
|
|
args[i] = a
|
|
} // else left fmt do its thing
|
|
}
|
|
s = fmt.Sprint(args...)
|
|
}
|
|
return s
|
|
}
|