ugorji__go/codec/gen-fast-path.go

//+build ignore

// Copyright (c) 2012, 2013 Ugorji Nwoke. All rights reserved.
// Use of this source code is governed by a BSD-style license found in the LICENSE file.

package main

import (
	"bytes"
	"go/format"
	"os"
	"strings"
	"text/template"
)

const tmplstr = `
// Copyright (c) 2012, 2013 Ugorji Nwoke. All rights reserved.
// Use of this source code is governed by a BSD-style license found in the LICENSE file.

// ************************************************************
// DO NOT EDIT. 
// THIS FILE IS GENERATED BY RUNNING: go run gen-fast-path.go
// ************************************************************

package codec

// Fast path functions try to create a fast path encode or decode implementation
// for common maps and slices.
//
// We define the functions and register then in this single file
// so as not to pollute the encode.go and decode.go, and create a dependency in there.
// This file can be omitted without causing a build failure.
//
// The advantage of fast paths is:
//    - Many calls bypass reflection altogether
// 
// Currently support
//    - slice of all builtin types,
//    - map of all builtin types to string or interface value
//    - symetrical maps of all builtin types (e.g. str-str, uint8-uint8)
// This should provide adequate "typical" implementations.
// 
// Note that fast track decode functions must handle values for which an address cannot be obtained.
// For example: 
//   m2 := map[string]int{}
//   p2 := []interface{}{m2}
//   // decoding into p2 will bomb if fast track functions do not treat like unaddressable.
// 

import (
	"reflect"
)

func init() {
	if !fastpathEnabled {
		return // basically disable the fast path checks (since accessing empty map is basically free)
	}
	fx := func(i interface{}, fe func(*encFnInfo, reflect.Value), fd func(*decFnInfo, reflect.Value)) {
		xrt := reflect.TypeOf(i)
		xptr := reflect.ValueOf(xrt).Pointer()
		fastpathsTyp[xptr] = xrt
		fastpathsEnc[xptr] = fe
		fastpathsDec[xptr] = fd
	}
	
	{{range .Values}}{{if .Slice }}
	fx([]{{ .Elem }}(nil), (*encFnInfo).{{ .MethodName true }}, (*decFnInfo).{{ .MethodName false}}){{end}}{{end}}

	{{range .Values}}{{if not .Slice }}
	fx(map[{{ .MapKey }}]{{ .Elem }}(nil), (*encFnInfo).{{ .MethodName true }}, (*decFnInfo).{{ .MethodName false}}){{end}}{{end}}

}

// -- encode

{{range .Values}}{{if .Slice }}

func (f *encFnInfo) {{ .MethodName true }}(rv reflect.Value) {
	v := rv.Interface().([]{{ .Elem }})
	if v == nil {
		f.ee.encodeNil()
		return
	}
	f.ee.encodeArrayPreamble(len(v))
	for _, v2 := range v {
		{{ encmd .Elem "v2"}}
	}
}

{{end}}{{end}}

{{range .Values}}{{if not .Slice }}

func (f *encFnInfo) {{ .MethodName true }}(rv reflect.Value) {
	v := rv.Interface().(map[{{ .MapKey }}]{{ .Elem }})
	if v == nil {
		f.ee.encodeNil()
		return
	}
	f.ee.encodeMapPreamble(len(v))
	{{if eq .MapKey "string"}}asSymbols := f.e.h.AsSymbols&AsSymbolMapStringKeysFlag != 0{{end}}
	for k2, v2 := range v {
		{{if eq .MapKey "string"}}if asSymbols {
			f.ee.encodeSymbol(k2)
		} else {
			f.ee.encodeString(c_UTF8, k2)
		}{{else}}{{ encmd .MapKey "k2"}}{{end}}
		{{ encmd .Elem "v2"}}
	}
}

{{end}}{{end}}

// -- decode

{{range .Values}}{{if .Slice }}

func (f *decFnInfo) {{ .MethodName false }}(rv reflect.Value) {
	xaddr := rv.CanAddr()
	var vp *[]{{ .Elem }}
	var v []{{ .Elem }}
	if xaddr {
		vp = rv.Addr().Interface().(*[]{{ .Elem }})
		v = *vp
	} else {
		v = rv.Interface().([]{{ .Elem }})
	}
	vtype := f.dd.currentEncodedType()
	if vtype == valueTypeNil {
		if xaddr {
			v = nil
			*vp = v
		} // else do nothing. 
		return
	}

	_, containerLenS := decContLens(f.dd, vtype)
	if containerLenS == 0 {
		return
	}
	if v == nil {
		if containerLenS > 0 {
			v = make([]{{ .Elem }}, containerLenS, containerLenS)
		} else {
			v = make([]{{ .Elem }}, 0, 4)
		}
	} else if containerLenS > cap(v) {
		if f.array {
			decErr(msgDecCannotExpandArr, cap(v), containerLenS)
		}
		s := make([]{{ .Elem }}, containerLenS, containerLenS)
		copy(s, v)
		v = s
	} else if containerLenS > len(v) {
		v = v[:containerLenS]
	}
	// for j := 0; j < containerLenS; j++ {
	for j := 0; ; j++ {
		if containerLenS >= 0 {
			if j >= containerLenS {
				break
			}
		} else if f.dd.checkBreak() {
			break
		}
		if j >= len(v) {
			v = append(v, {{ zerocmd .Elem }})
		}
		{{ if eq .Elem "interface{}" }}f.d.decode(&v[j])
		{{ else }}f.dd.initReadNext()
		v[j] = {{ decmd .Elem }}
		{{ end }}
	}
	if xaddr {
		*vp = v
	}
}

{{end}}{{end}}


{{range .Values}}{{if not .Slice }}

func (f *decFnInfo) {{ .MethodName false }}(rv reflect.Value) {
	xaddr := rv.CanAddr()
	var vp (*map[{{ .MapKey }}]{{ .Elem }})
	var v map[{{ .MapKey }}]{{ .Elem }}
	if xaddr {
		vp = rv.Addr().Interface().(*map[{{ .MapKey }}]{{ .Elem }})
		v = *vp
	} else {
		v = rv.Interface().(map[{{ .MapKey }}]{{ .Elem }})
	}
	vtype := f.dd.currentEncodedType()
	if vtype == valueTypeNil {
		if xaddr {
			v = nil
			*vp = v
		} // else do nothing. We never remove from a map.
		return
	}

	containerLen := f.dd.readMapLen()
	if containerLen == 0 {
		return
	}
	if xaddr && v == nil {
		if containerLen > 0 {
			v = make(map[{{ .MapKey }}]{{ .Elem }}, containerLen)
		} else {
			v = make(map[{{ .MapKey }}]{{ .Elem }}) // supports indefinite-length, etc
		}
		*vp = v
	}
	// for j := 0; j < containerLen; j++ {
	for j := 0; ; j++ {
		if containerLen >= 0 {
			if j >= containerLen {
				break
			}
		} else if f.dd.checkBreak() {
			break
		}
		{{ if eq .MapKey "interface{}" }}var mk interface{}
		f.d.decode(&mk)
		// special case if a byte array.
		if bv, bok := mk.([]byte); bok {
			mk = string(bv)
		}
		{{ else }}f.dd.initReadNext()
		mk := {{ decmd .MapKey }}
		{{ end }}
        mv := v[mk]
		{{ if eq .Elem "interface{}" }}f.d.decode(&mv)
		{{ else }}f.dd.initReadNext()
		mv = {{ decmd .Elem }}
		{{ end }}
		if v != nil {
			v[mk] = mv
		}
	}
}

{{end}}{{end}}

`

type genInfo struct {
	Slice  bool
	MapKey string
	Elem   string
}

func EncCommandAsString(s string, vname string) string {
	switch s {
	case "uint", "uint8", "uint16", "uint32", "uint64":
		return "f.ee.encodeUint(uint64(" + vname + "))"
	case "int", "int8", "int16", "int32", "int64":
		return "f.ee.encodeInt(int64(" + vname + "))"
	case "string":
		return "f.ee.encodeString(c_UTF8, " + vname + ")"
	case "float32":
		return "f.ee.encodeFloat32(" + vname + ")"
	case "float64":
		return "f.ee.encodeFloat64(" + vname + ")"
	case "bool":
		return "f.ee.encodeBool(" + vname + ")"
	case "symbol":
		return "f.ee.encodeSymbol(" + vname + ")"
	default:
		return "f.e.encode(" + vname + ")"
	}
}

func DecCommandAsString(s string) string {
	switch s {
	case "uint":
		return "uint(f.dd.decodeUint(uintBitsize))"
	case "uint8":
		return "uint8(f.dd.decodeUint(8))"
	case "uint16":
		return "uint16(f.dd.decodeUint(16))"
	case "uint32":
		return "uint32(f.dd.decodeUint(32))"
	case "uint64":
		return "f.dd.decodeUint(64)"
	case "int":
		return "int(f.dd.decodeInt(intBitsize))"
	case "int8":
		return "int8(f.dd.decodeInt(8))"
	case "int16":
		return "int16(f.dd.decodeInt(16))"
	case "int32":
		return "int32(f.dd.decodeInt(32))"
	case "int64":
		return "f.dd.decodeInt(64)"

	case "string":
		return "f.dd.decodeString()"
	case "float32":
		return "float32(f.dd.decodeFloat(true))"
	case "float64":
		return "f.dd.decodeFloat(false)"
	case "bool":
		return "f.dd.decodeBool()"
	default:
		panic("unknown type for decode: " + s)
	}

}

func (x *genInfo) MethodName(encode bool) string {
	var name []byte
	name = append(name, "fast"...)
	if encode {
		name = append(name, "Enc"...)
	} else {
		name = append(name, "Dec"...)
	}
	if x.Slice {
		name = append(name, "Slice"...)
	} else {
		name = append(name, "Map"...)
		name = append(name, titleCaseName(x.MapKey)...)
	}

	name = append(name, titleCaseName(x.Elem)...)
	return string(name)
}

func titleCaseName(s string) string {
	switch s {
	case "interface{}":
		return "Intf"
	default:
		return strings.ToUpper(s[0:1]) + s[1:]
	}
}

func ZeroValue(s string) string {
	switch s {
	case "interface{}":
		return "nil"
	case "bool":
		return "false"
	case "string":
		return `""`
	default:
		return "0"
	}
}

type genTmpl struct {
	Values []genInfo
}

func main() {
	types := []string{
		"interface{}",
		"string",
		"float32",
		"float64",
		"uint",
		"uint8",
		"uint16",
		"uint32",
		"uint64",
		"int",
		"int8",
		"int16",
		"int32",
		"int64",
		"bool",
	}
	// keep as slice, so it is in specific iteration order.
	// Initial order was uint64, string, interface{}, int, int64
	mapvaltypes := []string{
		"interface{}",
		"string",
		"uint",
		"uint32",
		"uint64",
		"int",
		"int32",
		"int64",
	}
	mapvaltypes2 := make(map[string]bool)
	for _, s := range mapvaltypes {
		mapvaltypes2[s] = true
	}
	var gt genTmpl
	// For each slice or map type, there must be a (symetrical) Encode and Decode fast-path function
	for _, s := range types {
		if s != "uint8" { // do not generate fast path for slice of bytes. Treat specially already.
			gt.Values = append(gt.Values, genInfo{true, "", s})
		}
		if !mapvaltypes2[s] {
			gt.Values = append(gt.Values, genInfo{false, s, s})
		}
		for _, ms := range mapvaltypes {
			gt.Values = append(gt.Values, genInfo{false, s, ms})
		}
	}

	funcs := make(template.FuncMap)
	// funcs["haspfx"] = strings.HasPrefix
	funcs["encmd"] = EncCommandAsString
	funcs["decmd"] = DecCommandAsString
	funcs["zerocmd"] = ZeroValue

	t := template.New("")
	t = t.Funcs(funcs)

	t, err := t.Parse(tmplstr)
	if err != nil {
		panic(err)
	}

	var out bytes.Buffer
	err = t.Execute(&out, &gt)
	if err != nil {
		panic(err)
	}
	// os.Stdout.Write(out.Bytes())
	bout, err := format.Source(out.Bytes())
	if err != nil {
		panic(err)
	}
	os.Stdout.Write(bout)
}