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// Copyright 2011 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

import (
        "fmt"
        "io"
        "reflect"
        "runtime"
        "sort"
        "strings"
        "text/template/parse"
)

// state represents the state of an execution. It's not part of the
// template so that multiple executions of the same template
// can execute in parallel.
type state struct {
        tmpl *Template
        wr   io.Writer
        line int        // line number for errors
        vars []variable // push-down stack of variable values.
}

// variable holds the dynamic value of a variable such as $, $x etc.
type variable struct {
        name  string
        value reflect.Value
}

// push pushes a new variable on the stack.
func (s *state) push(name string, value reflect.Value) {
        s.vars = append(s.vars, variable{name, value})
}

// mark returns the length of the variable stack.
func (s *state) mark() int {
        return len(s.vars)
}

// pop pops the variable stack up to the mark.
func (s *state) pop(mark int) {
        s.vars = s.vars[0:mark]
}

// setVar overwrites the top-nth variable on the stack. Used by range iterations.
func (s *state) setVar(n int, value reflect.Value) {
        s.vars[len(s.vars)-n].value = value
}

// varValue returns the value of the named variable.
func (s *state) varValue(name string) reflect.Value {
        for i := s.mark() - 1; i >= 0; i-- {
                if s.vars[i].name == name {
                        return s.vars[i].value
                }
        }
        s.errorf("undefined variable: %s", name)
        return zero
}

var zero reflect.Value

// errorf formats the error and terminates processing.
func (s *state) errorf(format string, args ...interface{}) {
        format = fmt.Sprintf("template: %s:%d: %s", s.tmpl.Name(), s.line, format)
        panic(fmt.Errorf(format, args...))
}

// error terminates processing.
func (s *state) error(err error) {
        s.errorf("%s", err)
}

// errRecover is the handler that turns panics into returns from the top
// level of Parse.
func errRecover(errp *error) {
        e := recover()
        if e != nil {
                switch err := e.(type) {
                case runtime.Error:
                        panic(e)
                case error:
                        *errp = err
                default:
                        panic(e)
                }
        }
}

// ExecuteTemplate applies the template associated with t that has the given name
// to the specified data object and writes the output to wr.
func (t *Template) ExecuteTemplate(wr io.Writer, name string, data interface{}) error {
        tmpl := t.tmpl[name]
        if tmpl == nil {
                return fmt.Errorf("template: no template %q associated with template %q", name, t.name)
        }
        return tmpl.Execute(wr, data)
}

// Execute applies a parsed template to the specified data object,
// and writes the output to wr.
func (t *Template) Execute(wr io.Writer, data interface{}) (err error) {
        defer errRecover(&err)
        value := reflect.ValueOf(data)
        state := &state{
                tmpl: t,
                wr:   wr,
                line: 1,
                vars: []variable{{"$", value}},
        }
        if t.Tree == nil || t.Root == nil {
                state.errorf("%q is an incomplete or empty template", t.name)
        }
        state.walk(value, t.Root)
        return
}

// Walk functions step through the major pieces of the template structure,
// generating output as they go.
func (s *state) walk(dot reflect.Value, n parse.Node) {
        switch n := n.(type) {
        case *parse.ActionNode:
                s.line = n.Line
                // Do not pop variables so they persist until next end.
                // Also, if the action declares variables, don't print the result.
                val := s.evalPipeline(dot, n.Pipe)
                if len(n.Pipe.Decl) == 0 {
                        s.printValue(n, val)
                }
        case *parse.IfNode:
                s.line = n.Line
                s.walkIfOrWith(parse.NodeIf, dot, n.Pipe, n.List, n.ElseList)
        case *parse.ListNode:
                for _, node := range n.Nodes {
                        s.walk(dot, node)
                }
        case *parse.RangeNode:
                s.line = n.Line
                s.walkRange(dot, n)
        case *parse.TemplateNode:
                s.line = n.Line
                s.walkTemplate(dot, n)
        case *parse.TextNode:
                if _, err := s.wr.Write(n.Text); err != nil {
                        s.error(err)
                }
        case *parse.WithNode:
                s.line = n.Line
                s.walkIfOrWith(parse.NodeWith, dot, n.Pipe, n.List, n.ElseList)
        default:
                s.errorf("unknown node: %s", n)
        }
}

// walkIfOrWith walks an 'if' or 'with' node. The two control structures
// are identical in behavior except that 'with' sets dot.
func (s *state) walkIfOrWith(typ parse.NodeType, dot reflect.Value, pipe *parse.PipeNode, list, elseList *parse.ListNode) {
        defer s.pop(s.mark())
        val := s.evalPipeline(dot, pipe)
        truth, ok := isTrue(val)
        if !ok {
                s.errorf("if/with can't use %v", val)
        }
        if truth {
                if typ == parse.NodeWith {
                        s.walk(val, list)
                } else {
                        s.walk(dot, list)
                }
        } else if elseList != nil {
                s.walk(dot, elseList)
        }
}

// isTrue returns whether the value is 'true', in the sense of not the zero of its type,
// and whether the value has a meaningful truth value.
func isTrue(val reflect.Value) (truth, ok bool) {
        if !val.IsValid() {
                // Something like var x interface{}, never set. It's a form of nil.
                return false, true
        }
        switch val.Kind() {
        case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
                truth = val.Len() > 0
        case reflect.Bool:
                truth = val.Bool()
        case reflect.Complex64, reflect.Complex128:
                truth = val.Complex() != 0
        case reflect.Chan, reflect.Func, reflect.Ptr, reflect.Interface:
                truth = !val.IsNil()
        case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
                truth = val.Int() != 0
        case reflect.Float32, reflect.Float64:
                truth = val.Float() != 0
        case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
                truth = val.Uint() != 0
        case reflect.Struct:
                truth = true // Struct values are always true.
        default:
                return
        }
        return truth, true
}

func (s *state) walkRange(dot reflect.Value, r *parse.RangeNode) {
        defer s.pop(s.mark())
        val, _ := indirect(s.evalPipeline(dot, r.Pipe))
        // mark top of stack before any variables in the body are pushed.
        mark := s.mark()
        oneIteration := func(index, elem reflect.Value) {
                // Set top var (lexically the second if there are two) to the element.
                if len(r.Pipe.Decl) > 0 {
                        s.setVar(1, elem)
                }
                // Set next var (lexically the first if there are two) to the index.
                if len(r.Pipe.Decl) > 1 {
                        s.setVar(2, index)
                }
                s.walk(elem, r.List)
                s.pop(mark)
        }
        switch val.Kind() {
        case reflect.Array, reflect.Slice:
                if val.Len() == 0 {
                        break
                }
                for i := 0; i < val.Len(); i++ {
                        oneIteration(reflect.ValueOf(i), val.Index(i))
                }
                return
        case reflect.Map:
                if val.Len() == 0 {
                        break
                }
                for _, key := range sortKeys(val.MapKeys()) {
                        oneIteration(key, val.MapIndex(key))
                }
                return
        case reflect.Chan:
                if val.IsNil() {
                        break
                }
                i := 0
                for ; ; i++ {
                        elem, ok := val.Recv()
                        if !ok {
                                break
                        }
                        oneIteration(reflect.ValueOf(i), elem)
                }
                if i == 0 {
                        break
                }
                return
        case reflect.Invalid:
                break // An invalid value is likely a nil map, etc. and acts like an empty map.
        default:
                s.errorf("range can't iterate over %v", val)
        }
        if r.ElseList != nil {
                s.walk(dot, r.ElseList)
        }
}

func (s *state) walkTemplate(dot reflect.Value, t *parse.TemplateNode) {
        tmpl := s.tmpl.tmpl[t.Name]
        if tmpl == nil {
                s.errorf("template %q not defined", t.Name)
        }
        // Variables declared by the pipeline persist.
        dot = s.evalPipeline(dot, t.Pipe)
        newState := *s
        newState.tmpl = tmpl
        // No dynamic scoping: template invocations inherit no variables.
        newState.vars = []variable{{"$", dot}}
        newState.walk(dot, tmpl.Root)
}

// Eval functions evaluate pipelines, commands, and their elements and extract
// values from the data structure by examining fields, calling methods, and so on.
// The printing of those values happens only through walk functions.

// evalPipeline returns the value acquired by evaluating a pipeline. If the
// pipeline has a variable declaration, the variable will be pushed on the
// stack. Callers should therefore pop the stack after they are finished
// executing commands depending on the pipeline value.
func (s *state) evalPipeline(dot reflect.Value, pipe *parse.PipeNode) (value reflect.Value) {
        if pipe == nil {
                return
        }
        for _, cmd := range pipe.Cmds {
                value = s.evalCommand(dot, cmd, value) // previous value is this one's final arg.
                // If the object has type interface{}, dig down one level to the thing inside.
                if value.Kind() == reflect.Interface && value.Type().NumMethod() == 0 {
                        value = reflect.ValueOf(value.Interface()) // lovely!
                }
        }
        for _, variable := range pipe.Decl {
                s.push(variable.Ident[0], value)
        }
        return value
}

func (s *state) notAFunction(args []parse.Node, final reflect.Value) {
        if len(args) > 1 || final.IsValid() {
                s.errorf("can't give argument to non-function %s", args[0])
        }
}

func (s *state) evalCommand(dot reflect.Value, cmd *parse.CommandNode, final reflect.Value) reflect.Value {
        firstWord := cmd.Args[0]
        switch n := firstWord.(type) {
        case *parse.FieldNode:
                return s.evalFieldNode(dot, n, cmd.Args, final)
        case *parse.IdentifierNode:
                // Must be a function.
                return s.evalFunction(dot, n.Ident, cmd.Args, final)
        case *parse.VariableNode:
                return s.evalVariableNode(dot, n, cmd.Args, final)
        }
        s.notAFunction(cmd.Args, final)
        switch word := firstWord.(type) {
        case *parse.BoolNode:
                return reflect.ValueOf(word.True)
        case *parse.DotNode:
                return dot
        case *parse.NumberNode:
                return s.idealConstant(word)
        case *parse.StringNode:
                return reflect.ValueOf(word.Text)
        }
        s.errorf("can't evaluate command %q", firstWord)
        panic("not reached")
}

// idealConstant is called to return the value of a number in a context where
// we don't know the type. In that case, the syntax of the number tells us
// its type, and we use Go rules to resolve.  Note there is no such thing as
// a uint ideal constant in this situation - the value must be of int type.
func (s *state) idealConstant(constant *parse.NumberNode) reflect.Value {
        // These are ideal constants but we don't know the type
        // and we have no context.  (If it was a method argument,
        // we'd know what we need.) The syntax guides us to some extent.
        switch {
        case constant.IsComplex:
                return reflect.ValueOf(constant.Complex128) // incontrovertible.
        case constant.IsFloat && strings.IndexAny(constant.Text, ".eE") >= 0:
                return reflect.ValueOf(constant.Float64)
        case constant.IsInt:
                n := int(constant.Int64)
                if int64(n) != constant.Int64 {
                        s.errorf("%s overflows int", constant.Text)
                }
                return reflect.ValueOf(n)
        case constant.IsUint:
                s.errorf("%s overflows int", constant.Text)
        }
        return zero
}

func (s *state) evalFieldNode(dot reflect.Value, field *parse.FieldNode, args []parse.Node, final reflect.Value) reflect.Value {
        return s.evalFieldChain(dot, dot, field.Ident, args, final)
}

func (s *state) evalVariableNode(dot reflect.Value, v *parse.VariableNode, args []parse.Node, final reflect.Value) reflect.Value {
        // $x.Field has $x as the first ident, Field as the second. Eval the var, then the fields.
        value := s.varValue(v.Ident[0])
        if len(v.Ident) == 1 {
                return value
        }
        return s.evalFieldChain(dot, value, v.Ident[1:], args, final)
}

// evalFieldChain evaluates .X.Y.Z possibly followed by arguments.
// dot is the environment in which to evaluate arguments, while
// receiver is the value being walked along the chain.
func (s *state) evalFieldChain(dot, receiver reflect.Value, ident []string, args []parse.Node, final reflect.Value) reflect.Value {
        n := len(ident)
        for i := 0; i < n-1; i++ {
                receiver = s.evalField(dot, ident[i], nil, zero, receiver)
        }
        // Now if it's a method, it gets the arguments.
        return s.evalField(dot, ident[n-1], args, final, receiver)
}

func (s *state) evalFunction(dot reflect.Value, name string, args []parse.Node, final reflect.Value) reflect.Value {
        function, ok := findFunction(name, s.tmpl)
        if !ok {
                s.errorf("%q is not a defined function", name)
        }
        return s.evalCall(dot, function, name, args, final)
}

// evalField evaluates an expression like (.Field) or (.Field arg1 arg2).
// The 'final' argument represents the return value from the preceding
// value of the pipeline, if any.
func (s *state) evalField(dot reflect.Value, fieldName string, args []parse.Node, final, receiver reflect.Value) reflect.Value {
        if !receiver.IsValid() {
                return zero
        }
        typ := receiver.Type()
        receiver, _ = indirect(receiver)
        // Unless it's an interface, need to get to a value of type *T to guarantee
        // we see all methods of T and *T.
        ptr := receiver
        if ptr.Kind() != reflect.Interface && ptr.CanAddr() {
                ptr = ptr.Addr()
        }
        if method := ptr.MethodByName(fieldName); method.IsValid() {
                return s.evalCall(dot, method, fieldName, args, final)
        }
        hasArgs := len(args) > 1 || final.IsValid()
        // It's not a method; is it a field of a struct?
        receiver, isNil := indirect(receiver)
        if receiver.Kind() == reflect.Struct {
                tField, ok := receiver.Type().FieldByName(fieldName)
                if ok {
                        field := receiver.FieldByIndex(tField.Index)
                        if hasArgs {
                                s.errorf("%s is not a method but has arguments", fieldName)
                        }
                        if tField.PkgPath == "" { // field is exported
                                return field
                        }
                }
        }
        // If it's a map, attempt to use the field name as a key.
        if receiver.Kind() == reflect.Map {
                nameVal := reflect.ValueOf(fieldName)
                if nameVal.Type().AssignableTo(receiver.Type().Key()) {
                        if hasArgs {
                                s.errorf("%s is not a method but has arguments", fieldName)
                        }
                        return receiver.MapIndex(nameVal)
                }
        }
        if isNil {
                s.errorf("nil pointer evaluating %s.%s", typ, fieldName)
        }
        s.errorf("can't evaluate field %s in type %s", fieldName, typ)
        panic("not reached")
}

var (
        errorType       = reflect.TypeOf((*error)(nil)).Elem()
        fmtStringerType = reflect.TypeOf((*fmt.Stringer)(nil)).Elem()
)

// evalCall executes a function or method call. If it's a method, fun already has the receiver bound, so
// it looks just like a function call.  The arg list, if non-nil, includes (in the manner of the shell), arg[0]
// as the function itself.
func (s *state) evalCall(dot, fun reflect.Value, name string, args []parse.Node, final reflect.Value) reflect.Value {
        if args != nil {
                args = args[1:] // Zeroth arg is function name/node; not passed to function.
        }
        typ := fun.Type()
        numIn := len(args)
        if final.IsValid() {
                numIn++
        }
        numFixed := len(args)
        if typ.IsVariadic() {
                numFixed = typ.NumIn() - 1 // last arg is the variadic one.
                if numIn < numFixed {
                        s.errorf("wrong number of args for %s: want at least %d got %d", name, typ.NumIn()-1, len(args))
                }
        } else if numIn < typ.NumIn()-1 || !typ.IsVariadic() && numIn != typ.NumIn() {
                s.errorf("wrong number of args for %s: want %d got %d", name, typ.NumIn(), len(args))
        }
        if !goodFunc(typ) {
                s.errorf("can't handle multiple results from method/function %q", name)
        }
        // Build the arg list.
        argv := make([]reflect.Value, numIn)
        // Args must be evaluated. Fixed args first.
        i := 0
        for ; i < numFixed; i++ {
                argv[i] = s.evalArg(dot, typ.In(i), args[i])
        }
        // Now the ... args.
        if typ.IsVariadic() {
                argType := typ.In(typ.NumIn() - 1).Elem() // Argument is a slice.
                for ; i < len(args); i++ {
                        argv[i] = s.evalArg(dot, argType, args[i])
                }
        }
        // Add final value if necessary.
        if final.IsValid() {
                argv[i] = final
        }
        result := fun.Call(argv)
        // If we have an error that is not nil, stop execution and return that error to the caller.
        if len(result) == 2 && !result[1].IsNil() {
                s.errorf("error calling %s: %s", name, result[1].Interface().(error))
        }
        return result[0]
}

// validateType guarantees that the value is valid and assignable to the type.
func (s *state) validateType(value reflect.Value, typ reflect.Type) reflect.Value {
        if !value.IsValid() {
                switch typ.Kind() {
                case reflect.Interface, reflect.Ptr, reflect.Chan, reflect.Map, reflect.Slice, reflect.Func:
                        // An untyped nil interface{}. Accept as a proper nil value.
                        value = reflect.Zero(typ)
                default:
                        s.errorf("invalid value; expected %s", typ)
                }
        }
        if !value.Type().AssignableTo(typ) {
                // Does one dereference or indirection work? We could do more, as we
                // do with method receivers, but that gets messy and method receivers
                // are much more constrained, so it makes more sense there than here.
                // Besides, one is almost always all you need.
                switch {
                case value.Kind() == reflect.Ptr && value.Type().Elem().AssignableTo(typ):
                        value = value.Elem()
                case reflect.PtrTo(value.Type()).AssignableTo(typ) && value.CanAddr():
                        value = value.Addr()
                default:
                        s.errorf("wrong type for value; expected %s; got %s", typ, value.Type())
                }
        }
        return value
}

func (s *state) evalArg(dot reflect.Value, typ reflect.Type, n parse.Node) reflect.Value {
        switch arg := n.(type) {
        case *parse.DotNode:
                return s.validateType(dot, typ)
        case *parse.FieldNode:
                return s.validateType(s.evalFieldNode(dot, arg, []parse.Node{n}, zero), typ)
        case *parse.VariableNode:
                return s.validateType(s.evalVariableNode(dot, arg, nil, zero), typ)
        }
        switch typ.Kind() {
        case reflect.Bool:
                return s.evalBool(typ, n)
        case reflect.Complex64, reflect.Complex128:
                return s.evalComplex(typ, n)
        case reflect.Float32, reflect.Float64:
                return s.evalFloat(typ, n)
        case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
                return s.evalInteger(typ, n)
        case reflect.Interface:
                if typ.NumMethod() == 0 {
                        return s.evalEmptyInterface(dot, n)
                }
        case reflect.String:
                return s.evalString(typ, n)
        case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
                return s.evalUnsignedInteger(typ, n)
        }
        s.errorf("can't handle %s for arg of type %s", n, typ)
        panic("not reached")
}

func (s *state) evalBool(typ reflect.Type, n parse.Node) reflect.Value {
        if n, ok := n.(*parse.BoolNode); ok {
                value := reflect.New(typ).Elem()
                value.SetBool(n.True)
                return value
        }
        s.errorf("expected bool; found %s", n)
        panic("not reached")
}

func (s *state) evalString(typ reflect.Type, n parse.Node) reflect.Value {
        if n, ok := n.(*parse.StringNode); ok {
                value := reflect.New(typ).Elem()
                value.SetString(n.Text)
                return value
        }
        s.errorf("expected string; found %s", n)
        panic("not reached")
}

func (s *state) evalInteger(typ reflect.Type, n parse.Node) reflect.Value {
        if n, ok := n.(*parse.NumberNode); ok && n.IsInt {
                value := reflect.New(typ).Elem()
                value.SetInt(n.Int64)
                return value
        }
        s.errorf("expected integer; found %s", n)
        panic("not reached")
}

func (s *state) evalUnsignedInteger(typ reflect.Type, n parse.Node) reflect.Value {
        if n, ok := n.(*parse.NumberNode); ok && n.IsUint {
                value := reflect.New(typ).Elem()
                value.SetUint(n.Uint64)
                return value
        }
        s.errorf("expected unsigned integer; found %s", n)
        panic("not reached")
}

func (s *state) evalFloat(typ reflect.Type, n parse.Node) reflect.Value {
        if n, ok := n.(*parse.NumberNode); ok && n.IsFloat {
                value := reflect.New(typ).Elem()
                value.SetFloat(n.Float64)
                return value
        }
        s.errorf("expected float; found %s", n)
        panic("not reached")
}

func (s *state) evalComplex(typ reflect.Type, n parse.Node) reflect.Value {
        if n, ok := n.(*parse.NumberNode); ok && n.IsComplex {
                value := reflect.New(typ).Elem()
                value.SetComplex(n.Complex128)
                return value
        }
        s.errorf("expected complex; found %s", n)
        panic("not reached")
}

func (s *state) evalEmptyInterface(dot reflect.Value, n parse.Node) reflect.Value {
        switch n := n.(type) {
        case *parse.BoolNode:
                return reflect.ValueOf(n.True)
        case *parse.DotNode:
                return dot
        case *parse.FieldNode:
                return s.evalFieldNode(dot, n, nil, zero)
        case *parse.IdentifierNode:
                return s.evalFunction(dot, n.Ident, nil, zero)
        case *parse.NumberNode:
                return s.idealConstant(n)
        case *parse.StringNode:
                return reflect.ValueOf(n.Text)
        case *parse.VariableNode:
                return s.evalVariableNode(dot, n, nil, zero)
        }
        s.errorf("can't handle assignment of %s to empty interface argument", n)
        panic("not reached")
}

// indirect returns the item at the end of indirection, and a bool to indicate if it's nil.
// We indirect through pointers and empty interfaces (only) because
// non-empty interfaces have methods we might need.
func indirect(v reflect.Value) (rv reflect.Value, isNil bool) {
        for ; v.Kind() == reflect.Ptr || v.Kind() == reflect.Interface; v = v.Elem() {
                if v.IsNil() {
                        return v, true
                }
                if v.Kind() == reflect.Interface && v.NumMethod() > 0 {
                        break
                }
        }
        return v, false
}

// printValue writes the textual representation of the value to the output of
// the template.
func (s *state) printValue(n parse.Node, v reflect.Value) {
        if v.Kind() == reflect.Ptr {
                v, _ = indirect(v) // fmt.Fprint handles nil.
        }
        if !v.IsValid() {
                fmt.Fprint(s.wr, "<no value>")
                return
        }

        if !v.Type().Implements(errorType) && !v.Type().Implements(fmtStringerType) {
                if v.CanAddr() && (reflect.PtrTo(v.Type()).Implements(errorType) || reflect.PtrTo(v.Type()).Implements(fmtStringerType)) {
                        v = v.Addr()
                } else {
                        switch v.Kind() {
                        case reflect.Chan, reflect.Func:
                                s.errorf("can't print %s of type %s", n, v.Type())
                        }
                }
        }
        fmt.Fprint(s.wr, v.Interface())
}

// Types to help sort the keys in a map for reproducible output.

type rvs []reflect.Value

func (x rvs) Len() int      { return len(x) }
func (x rvs) Swap(i, j int) { x[i], x[j] = x[j], x[i] }

type rvInts struct{ rvs }

func (x rvInts) Less(i, j int) bool { return x.rvs[i].Int() < x.rvs[j].Int() }

type rvUints struct{ rvs }

func (x rvUints) Less(i, j int) bool { return x.rvs[i].Uint() < x.rvs[j].Uint() }

type rvFloats struct{ rvs }

func (x rvFloats) Less(i, j int) bool { return x.rvs[i].Float() < x.rvs[j].Float() }

type rvStrings struct{ rvs }

func (x rvStrings) Less(i, j int) bool { return x.rvs[i].String() < x.rvs[j].String() }

// sortKeys sorts (if it can) the slice of reflect.Values, which is a slice of map keys.
func sortKeys(v []reflect.Value) []reflect.Value {
        if len(v) <= 1 {
                return v
        }
        switch v[0].Kind() {
        case reflect.Float32, reflect.Float64:
                sort.Sort(rvFloats{v})
        case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
                sort.Sort(rvInts{v})
        case reflect.String:
                sort.Sort(rvStrings{v})
        case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
                sort.Sort(rvUints{v})
        }
        return v
}