[dev.power64] code review 152570049: all: merge default into dev.power64

src/encoding/gob/decgen.go

Index: src/encoding/gob/decgen.go
===================================================================
new file mode 100644
--- /dev/null
+++ b/src/encoding/gob/decgen.go
@@ -0,0 +1,240 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build ignore
+
+// encgen writes the helper functions for encoding. Intended to be
+// used with go generate; see the invocation in encode.go.
+
+// TODO: We could do more by being unsafe. Add a -unsafe flag?
+
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"go/format"
+	"log"
+	"os"
+)
+
+var output = flag.String("output", "dec_helpers.go", "file name to write")
+
+type Type struct {
+	lower   string
+	upper   string
+	decoder string
+}
+
+var types = []Type{
+	{
+		"bool",
+		"Bool",
+		`slice[i] = state.decodeUint() != 0`,
+	},
+	{
+		"complex64",
+		"Complex64",
+		`real := float32FromBits(state.decodeUint(), ovfl)
+		imag := float32FromBits(state.decodeUint(), ovfl)
+		slice[i] = complex(float32(real), float32(imag))`,
+	},
+	{
+		"complex128",
+		"Complex128",
+		`real := float64FromBits(state.decodeUint())
+		imag := float64FromBits(state.decodeUint())
+		slice[i] = complex(real, imag)`,
+	},
+	{
+		"float32",
+		"Float32",
+		`slice[i] = float32(float32FromBits(state.decodeUint(), ovfl))`,
+	},
+	{
+		"float64",
+		"Float64",
+		`slice[i] = float64FromBits(state.decodeUint())`,
+	},
+	{
+		"int",
+		"Int",
+		`x := state.decodeInt()
+		// MinInt and MaxInt
+		if x < ^int64(^uint(0)>>1) || int64(^uint(0)>>1) < x {
+			error_(ovfl)
+		}
+		slice[i] = int(x)`,
+	},
+	{
+		"int16",
+		"Int16",
+		`x := state.decodeInt()
+		if x < math.MinInt16 || math.MaxInt16 < x {
+			error_(ovfl)
+		}
+		slice[i] = int16(x)`,
+	},
+	{
+		"int32",
+		"Int32",
+		`x := state.decodeInt()
+		if x < math.MinInt32 || math.MaxInt32 < x {
+			error_(ovfl)
+		}
+		slice[i] = int32(x)`,
+	},
+	{
+		"int64",
+		"Int64",
+		`slice[i] = state.decodeInt()`,
+	},
+	{
+		"int8",
+		"Int8",
+		`x := state.decodeInt()
+		if x < math.MinInt8 || math.MaxInt8 < x {
+			error_(ovfl)
+		}
+		slice[i] = int8(x)`,
+	},
+	{
+		"string",
+		"String",
+		`u := state.decodeUint()
+		n := int(u)
+		if n < 0 || uint64(n) != u || n > state.b.Len() {
+			errorf("length of string exceeds input size (%d bytes)", u)
+		}
+		if n > state.b.Len() {
+			errorf("string data too long for buffer: %d", n)
+		}
+		// Read the data.
+		data := make([]byte, n)
+		if _, err := state.b.Read(data); err != nil {
+			errorf("error decoding string: %s", err)
+		}
+		slice[i] = string(data)`,
+	},
+	{
+		"uint",
+		"Uint",
+		`x := state.decodeUint()
+		/*TODO if math.MaxUint32 < x {
+			error_(ovfl)
+		}*/
+		slice[i] = uint(x)`,
+	},
+	{
+		"uint16",
+		"Uint16",
+		`x := state.decodeUint()
+		if math.MaxUint16 < x {
+			error_(ovfl)
+		}
+		slice[i] = uint16(x)`,
+	},
+	{
+		"uint32",
+		"Uint32",
+		`x := state.decodeUint()
+		if math.MaxUint32 < x {
+			error_(ovfl)
+		}
+		slice[i] = uint32(x)`,
+	},
+	{
+		"uint64",
+		"Uint64",
+		`slice[i] = state.decodeUint()`,
+	},
+	{
+		"uintptr",
+		"Uintptr",
+		`x := state.decodeUint()
+		if uint64(^uintptr(0)) < x {
+			error_(ovfl)
+		}
+		slice[i] = uintptr(x)`,
+	},
+	// uint8 Handled separately.
+}
+
+func main() {
+	log.SetFlags(0)
+	log.SetPrefix("decgen: ")
+	flag.Parse()
+	if flag.NArg() != 0 {
+		log.Fatal("usage: decgen [--output filename]")
+	}
+	var b bytes.Buffer
+	fmt.Fprintf(&b, "// Created by decgen --output %s; DO NOT EDIT\n", *output)
+	fmt.Fprint(&b, header)
+	printMaps(&b, "Array")
+	fmt.Fprint(&b, "\n")
+	printMaps(&b, "Slice")
+	for _, t := range types {
+		fmt.Fprintf(&b, arrayHelper, t.lower, t.upper)
+		fmt.Fprintf(&b, sliceHelper, t.lower, t.upper, t.decoder)
+	}
+	source, err := format.Source(b.Bytes())
+	if err != nil {
+		log.Fatal("source format error:", err)
+	}
+	fd, err := os.Create(*output)
+	_, err = fd.Write(source)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func printMaps(b *bytes.Buffer, upperClass string) {
+	fmt.Fprintf(b, "var dec%sHelper = map[reflect.Kind]decHelper{\n", upperClass)
+	for _, t := range types {
+		fmt.Fprintf(b, "reflect.%s: dec%s%s,\n", t.upper, t.upper, upperClass)
+	}
+	fmt.Fprintf(b, "}\n")
+}
+
+const header = `
+// Copyright 2014 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 gob
+
+import (
+	"math"
+	"reflect"
+)
+
+`
+
+const arrayHelper = `
+func dec%[2]sArray(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	// Can only slice if it is addressable.
+	if !v.CanAddr() {
+		return false
+	}
+	return dec%[2]sSlice(state, v.Slice(0, v.Len()), length, ovfl)
+}
+`
+
+const sliceHelper = `
+func dec%[2]sSlice(state *decoderState, v reflect.Value, length int, ovfl error) bool {
+	slice, ok := v.Interface().([]%[1]s)
+	if !ok {
+		// It is kind %[1]s but not type %[1]s. TODO: We can handle this unsafely.
+		return false
+	}
+	for i := 0; i < length; i++ {
+		if state.b.Len() == 0 {
+			errorf("decoding %[1]s array or slice: length exceeds input size (%%d elements)", length)
+		}
+		%[3]s
+	}
+	return true
+}
+`