github.com/ugorji/go/codec@v1.2.13-0.20240307214044-07c54c229a5a/fast-path.go.tmpl

// +build !notfastpath
// +build !codec.notfastpath

// Copyright (c) 2012-2020 Ugorji Nwoke. All rights reserved.
// Use of this source code is governed by a MIT license found in the LICENSE file.

// Code generated from fast-path.go.tmpl - DO NOT EDIT.

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 them 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 (numeric, bool, string, []byte)
//    - maps of builtin types to builtin or interface{} type, EXCEPT FOR
//      keys of type uintptr, int8/16/32, uint16/32, float32/64, bool, interface{}
//      AND values of type type int8/16/32, uint16/32
// 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.
// 

{{/*
fastpathEncMapStringUint64R  (called by fastpath...switch)
EncMapStringUint64V (called by codecgen)

fastpathEncSliceBoolR: (called by fastpath...switch) (checks f.ti.mbs and calls one of them below)
EncSliceBoolV  (also called by codecgen)
EncAsMapSliceBoolV (delegate when mapbyslice=true)

fastpathDecSliceIntfR (called by fastpath...switch) (calls Y or N below depending on if it can be updated)
DecSliceIntfX  (called by codecgen) (calls Y below)
DecSliceIntfY  (delegate when slice CAN be updated)
DecSliceIntfN  (delegate when slice CANNOT be updated e.g. from array or non-addressable slice)

fastpathDecMap...R (called by fastpath...switch) (calls L or X? below)
DecMap...X  (called by codecgen)
DecMap...L  (delegated to by both above)
*/ -}}

import (
	"reflect"
	"sort"
)

const fastpathEnabled = true

{{/*
const fastpathMapBySliceErrMsg = "mapBySlice requires even slice length, but got %v"
*/ -}}

type fastpathT struct {}

var fastpathTV fastpathT

type fastpathE struct {
	{{/* rtid uintptr */ -}}
	rt reflect.Type 
	encfn func(*Encoder, *codecFnInfo, reflect.Value)
	decfn func(*Decoder, *codecFnInfo, reflect.Value)
}

type fastpathA [{{ .FastpathLen }}]fastpathE
type fastpathARtid [{{ .FastpathLen }}]uintptr

var fastpathAv fastpathA
var fastpathAvRtid fastpathARtid

type fastpathAslice struct{}

func (fastpathAslice) Len() int { return {{ .FastpathLen }} }
func (fastpathAslice) Less(i, j int) bool {
	return fastpathAvRtid[uint(i)] < fastpathAvRtid[uint(j)]
}
func (fastpathAslice) Swap(i, j int) {
	fastpathAvRtid[uint(i)], fastpathAvRtid[uint(j)] = fastpathAvRtid[uint(j)], fastpathAvRtid[uint(i)]
	fastpathAv[uint(i)], fastpathAv[uint(j)] = fastpathAv[uint(j)], fastpathAv[uint(i)]
}

func fastpathAvIndex(rtid uintptr) int {
	// use binary search to grab the index (adapted from sort/search.go)
	// Note: we use goto (instead of for loop) so this can be inlined.
 	// h, i, j := 0, 0, {{ .FastpathLen }}
	var h, i uint
	var j uint = {{ .FastpathLen }}
LOOP:
	if i < j {
		h = (i + j) >> 1 // avoid overflow when computing h // h = i + (j-i)/2
		if fastpathAvRtid[h] < rtid {
			i = h + 1
		} else {
			j = h
		}
		goto LOOP
	}
	if i < {{ .FastpathLen }} && fastpathAvRtid[i] == rtid {
		return int(i)
	}
	return -1
}


// due to possible initialization loop error, make fastpath in an init()
func init() {
	var i uint = 0
	fn := func(v interface{},
		fe func(*Encoder, *codecFnInfo, reflect.Value),
		fd func(*Decoder, *codecFnInfo, reflect.Value)) {
		xrt := reflect.TypeOf(v)
		xptr := rt2id(xrt)
        fastpathAvRtid[i] = xptr
		fastpathAv[i] = fastpathE{xrt, fe, fd}
		i++
	}
	{{/* do not register []byte in fast-path */}}
	{{range .Values}}{{if not .Primitive}}{{if not .MapKey -}}
	fn([]{{ .Elem }}(nil), (*Encoder).{{ .MethodNamePfx "fastpathEnc" false }}R, (*Decoder).{{ .MethodNamePfx "fastpathDec" false }}R)
	{{end}}{{end}}{{end}}
	
	{{range .Values}}{{if not .Primitive}}{{if .MapKey -}}
	fn(map[{{ .MapKey }}]{{ .Elem }}(nil), (*Encoder).{{ .MethodNamePfx "fastpathEnc" false }}R, (*Decoder).{{ .MethodNamePfx "fastpathDec" false }}R)
	{{end}}{{end}}{{end}}
	
	sort.Sort(fastpathAslice{})
}

// -- encode

// -- -- fast path type switch
func fastpathEncodeTypeSwitch(iv interface{}, e *Encoder) bool {
	switch v := iv.(type) {
{{range .Values}}{{if not .Primitive}}{{if not .MapKey -}}
	case []{{ .Elem }}:
		fastpathTV.{{ .MethodNamePfx "Enc" false }}V(v, e)
	case *[]{{ .Elem }}:
		if *v == nil {
			e.e.EncodeNil()
		} else {
			fastpathTV.{{ .MethodNamePfx "Enc" false }}V(*v, e)
		}
{{end}}{{end}}{{end -}}

{{range .Values}}{{if not .Primitive}}{{if .MapKey -}}
	case map[{{ .MapKey }}]{{ .Elem }}:
		fastpathTV.{{ .MethodNamePfx "Enc" false }}V(v, e)
	case *map[{{ .MapKey }}]{{ .Elem }}:
		if *v == nil {
			e.e.EncodeNil()
		} else {
			fastpathTV.{{ .MethodNamePfx "Enc" false }}V(*v, e)
		}
{{end}}{{end}}{{end -}}

	default:
		_ = v // workaround https://github.com/golang/go/issues/12927 seen in go1.4
		return false
	}
	return true
}

// -- -- fast path functions
{{range .Values}}{{if not .Primitive}}{{if not .MapKey -}} 
func (e *Encoder) {{ .MethodNamePfx "fastpathEnc" false }}R(f *codecFnInfo, rv reflect.Value) {
	var v  []{{ .Elem }}
	if rv.Kind() == reflect.Array {
		rvGetSlice4Array(rv, &v)
	} else {
		v = rv2i(rv).([]{{ .Elem }})
	}
	if f.ti.mbs {
		fastpathTV.{{ .MethodNamePfx "EncAsMap" false }}V(v, e)
	} else {
		fastpathTV.{{ .MethodNamePfx "Enc" false }}V(v, e)
	}
}
func (fastpathT) {{ .MethodNamePfx "Enc" false }}V(v []{{ .Elem }}, e *Encoder) {
	{{/* if v == nil { e.e.EncodeNil(); return } */ -}}
	{{ if eq .Elem "uint8" "byte" -}}
	e.e.EncodeStringBytesRaw(v)
	{{ else -}}
	e.arrayStart(len(v))
	for j := range v {
		e.arrayElem()
		{{ encmd .Elem "v[j]"}}
	} 
	e.arrayEnd()
	{{ end -}}
}
func (fastpathT) {{ .MethodNamePfx "EncAsMap" false }}V(v []{{ .Elem }}, e *Encoder) {
	{{/* if v == nil { e.e.EncodeNil() } else */ -}}
	e.haltOnMbsOddLen(len(v))
	{{/*
	if len(v)&1 != 0 { // similar to &1==1 or %2 == 1
		e.errorf(fastpathMapBySliceErrMsg, len(v))
	}
	*/ -}}
	e.mapStart(len(v) >> 1) // e.mapStart(len(v) / 2)
	for j := range v {
		if j&1 == 0 { // if j%2 == 0 {
			e.mapElemKey()
		} else {
			e.mapElemValue()
		}
		{{ encmd .Elem "v[j]"}}
	}
	e.mapEnd()
}
{{end}}{{end}}{{end -}}

{{range .Values}}{{if not .Primitive}}{{if .MapKey -}}
func (e *Encoder) {{ .MethodNamePfx "fastpathEnc" false }}R(f *codecFnInfo, rv reflect.Value) {
	fastpathTV.{{ .MethodNamePfx "Enc" false }}V(rv2i(rv).(map[{{ .MapKey }}]{{ .Elem }}), e)
}
func (fastpathT) {{ .MethodNamePfx "Enc" false }}V(v map[{{ .MapKey }}]{{ .Elem }}, e *Encoder) {
	{{/* if v == nil { e.e.EncodeNil(); return } */ -}}
	e.mapStart(len(v))
	if e.h.Canonical { {{/* need to figure out .NoCanonical */}}
		{{if eq .MapKey "interface{}"}}{{/* out of band */ -}}
		var mksv []byte = make([]byte, 0, len(v)*16) // temporary byte slice for the encoding
		e2 := NewEncoderBytes(&mksv, e.hh)
		v2 := make([]bytesIntf, len(v))
		var i, l uint {{/* put loop variables outside. seems currently needed for better perf */}}
		var vp *bytesIntf
		for k2 := range v {
			l = uint(len(mksv))
			e2.MustEncode(k2)
			vp = &v2[i]
			vp.v = mksv[l:]
			vp.i = k2 
			i++
		}
		sort.Sort(bytesIntfSlice(v2))
		for j := range v2 {
			e.mapElemKey()
			e.asis(v2[j].v)
			e.mapElemValue()
			e.encode(v[v2[j].i])
		} {{else}}{{ $x := sorttype .MapKey true}}v2 := make([]{{ $x }}, len(v))
		var i uint
		for k := range v {
			v2[i] = {{if eq $x .MapKey}}k{{else}}{{ $x }}(k){{end}}
			i++
		}
		sort.Sort({{ sorttype .MapKey false}}(v2))
		for _, k2 := range v2 {
			e.mapElemKey()
			{{if eq .MapKey "string"}} e.e.EncodeString(k2) {{else}}{{ $y := printf "%s(k2)" .MapKey }}{{if eq $x .MapKey }}{{ $y = "k2" }}{{end}}{{ encmd .MapKey $y }}{{end}}
			e.mapElemValue()
			{{ $y := printf "v[%s(k2)]" .MapKey }}{{if eq $x .MapKey }}{{ $y = "v[k2]" }}{{end}}{{ encmd .Elem $y }}
		} {{end}}
	} else { 
		for k2, v2 := range v {
			e.mapElemKey()
			{{if eq .MapKey "string"}} e.e.EncodeString(k2) {{else}}{{ encmd .MapKey "k2"}}{{end}}
			e.mapElemValue()
			{{ encmd .Elem "v2"}}
		}
	}
	e.mapEnd()
}
{{end}}{{end}}{{end -}}

// -- decode

// -- -- fast path type switch
func fastpathDecodeTypeSwitch(iv interface{}, d *Decoder) bool {
	var changed bool
	var containerLen int
	switch v := iv.(type) {
{{range .Values}}{{if not .Primitive}}{{if not .MapKey -}}
	case []{{ .Elem }}:
		fastpathTV.{{ .MethodNamePfx "Dec" false }}N(v, d)
	case *[]{{ .Elem }}:
		var v2 []{{ .Elem }}
		if v2, changed = fastpathTV.{{ .MethodNamePfx "Dec" false }}Y(*v, d); changed {
			*v = v2
		}
{{end}}{{end}}{{end -}}
{{range .Values}}{{if not .Primitive}}{{if .MapKey }}{{/*
// maps only change if nil, and in that case, there's no point copying
*/ -}}
	case map[{{ .MapKey }}]{{ .Elem }}:
		containerLen = d.mapStart(d.d.ReadMapStart())
		if containerLen != containerLenNil {
			if containerLen != 0 {
				fastpathTV.{{ .MethodNamePfx "Dec" false }}L(v, containerLen, d)
			}
			d.mapEnd()
		}
	case *map[{{ .MapKey }}]{{ .Elem }}:
		{{/*
		containerLen = d.mapStart(d.d.ReadMapStart())
		if containerLen == 0 {
			d.mapEnd()
		} else if containerLen == containerLenNil {
			*v = nil
		} else {
			if *v == nil {
				*v = make(map[{{ .MapKey }}]{{ .Elem }}, decInferLen(containerLen, d.h.MaxInitLen, {{ .Size }}))
			}
			fastpathTV.{{ .MethodNamePfx "Dec" false }}L(*v, containerLen, d)
		}
		// consider delegating fully to X - encoding *map is uncommon, so ok to pay small function call cost
		*/ -}}
		fastpathTV.{{ .MethodNamePfx "Dec" false }}X(v, d)
{{end}}{{end}}{{end -}}
	default:
		_ = v // workaround https://github.com/golang/go/issues/12927 seen in go1.4
		return false
	}
	return true
}

func fastpathDecodeSetZeroTypeSwitch(iv interface{}) bool {
	switch v := iv.(type) {
{{range .Values}}{{if not .Primitive}}{{if not .MapKey -}}
	case *[]{{ .Elem }}: 
		*v = nil
{{end}}{{end}}{{end}}
{{range .Values}}{{if not .Primitive}}{{if .MapKey -}}
	case *map[{{ .MapKey }}]{{ .Elem }}: 
		*v = nil 
{{end}}{{end}}{{end}}
	default:
		_ = v // workaround https://github.com/golang/go/issues/12927 seen in go1.4
		return false
	}
	return true
}

// -- -- fast path functions
{{range .Values}}{{if not .Primitive}}{{if not .MapKey -}}
{{/*
Slices can change if they
- did not come from an array
- are addressable (from a ptr)
- are settable (e.g. contained in an interface{})
*/}}
func (d *Decoder) {{ .MethodNamePfx "fastpathDec" false }}R(f *codecFnInfo, rv reflect.Value) {
	{{/*
    // seqTypeArray=true means that we are not getting a pointer, so no need to check that.
    if f.seq != seqTypeArray && rv.Kind() == reflect.Ptr {
    */ -}}
	var v  []{{ .Elem }}
	switch rv.Kind() {
	case reflect.Ptr:
		vp := rv2i(rv).(*[]{{ .Elem }})
		var changed bool
		if v, changed = fastpathTV.{{ .MethodNamePfx "Dec" false }}Y(*vp, d); changed {
			*vp = v
		}
	case reflect.Array:
		rvGetSlice4Array(rv, &v)
		fastpathTV.{{ .MethodNamePfx "Dec" false }}N(v, d)
	default:
		fastpathTV.{{ .MethodNamePfx "Dec" false }}N(rv2i(rv).([]{{ .Elem }}), d)
	}
}
func (f fastpathT) {{ .MethodNamePfx "Dec" false }}X(vp *[]{{ .Elem }}, d *Decoder) {
	if v, changed := f.{{ .MethodNamePfx "Dec" false }}Y(*vp, d); changed { *vp = v }
}
func (fastpathT) {{ .MethodNamePfx "Dec" false }}Y(v []{{ .Elem }}, d *Decoder) (v2 []{{ .Elem }}, changed bool) {
	{{ if eq .Elem "uint8" "byte" -}}
	switch d.d.ContainerType() {
	case valueTypeNil, valueTypeMap:
		break
	default:
		v2 = d.decodeBytesInto(v[:len(v):len(v)])
		changed = !(len(v2) > 0 && len(v2) == len(v) && &v2[0] == &v[0]) // not same slice
		return
	}
	{{ end -}}
	slh, containerLenS := d.decSliceHelperStart()
	if slh.IsNil {
		if v == nil { return }
		return nil, true
	}
	if containerLenS == 0 {
		if v == nil { v = []{{ .Elem }}{} } else if len(v) != 0 { v = v[:0] }
		slh.End()
		return v, true
	}
	hasLen := containerLenS > 0
	var xlen int 
	if hasLen {
		if containerLenS > cap(v) {
			xlen = decInferLen(containerLenS, d.h.MaxInitLen, {{ .Size }})
			if xlen <= cap(v) {
				v = v[:uint(xlen)]
			} else {
				v = make([]{{ .Elem }}, uint(xlen))
			}
			changed = true 
		} else if containerLenS != len(v) {
			v = v[:containerLenS]
			changed = true
		}
	}
	var j int
    for j = 0; d.containerNext(j, containerLenS, hasLen); j++ {
		if j == 0 && len(v) == 0 { // means hasLen == false
			xlen = decInferLen(containerLenS, d.h.MaxInitLen, {{ .Size }}) {{/* xlen = decDefSliceCap */}}
			v = make([]{{ .Elem }}, uint(xlen))
			changed = true
		}
		{{/* // if indefinite, etc, then expand the slice if necessary */ -}}
		if j >= len(v) {
			v = append(v, {{ zerocmd .Elem }})
			changed = true
		} 
		slh.ElemContainerState(j)
		{{ if eq .Elem "interface{}" }}d.decode(&v[uint(j)]){{ else }}v[uint(j)] = {{ decmd .Elem false }}{{ end }}
	}
	if j < len(v) {
		v = v[:uint(j)]
		changed = true
	} else if j == 0 && v == nil {
		v = []{{ .Elem }}{}
		changed = true
	}
	slh.End()
	return v, changed
}
func (fastpathT) {{ .MethodNamePfx "Dec" false }}N(v []{{ .Elem }}, d *Decoder) {
	{{ if eq .Elem "uint8" "byte" -}}
	switch d.d.ContainerType() {
	case valueTypeNil, valueTypeMap:
		break
	default:
		v2 := d.decodeBytesInto(v[:len(v):len(v)])
		if !(len(v2) > 0 && len(v2) == len(v) && &v2[0] == &v[0]) { // not same slice
			copy(v, v2)
		}
		return
	}
	{{ end -}}
	slh, containerLenS := d.decSliceHelperStart()
	if slh.IsNil {
		return
	}
	if containerLenS == 0 {
		slh.End()
		return
	}
	hasLen := containerLenS > 0
    for j := 0; d.containerNext(j, containerLenS, hasLen); j++ {
		{{/* // if indefinite, etc, then expand the slice if necessary */ -}}
		if j >= len(v) {
			slh.arrayCannotExpand(hasLen, len(v), j, containerLenS)
			return
		} 
		slh.ElemContainerState(j)
		{{ if eq .Elem "interface{}" -}}
		d.decode(&v[uint(j)])
		{{- else -}}
		v[uint(j)] = {{ decmd .Elem false }}
		{{- end }}
	}
	slh.End()
}
{{end}}{{end}}{{end -}}

{{range .Values}}{{if not .Primitive}}{{if .MapKey -}}
{{/*
Maps can change if they are
- addressable (from a ptr)
- settable (e.g. contained in an interface{})

Also, these methods are called by decodeValue directly, after handling a TryNil.
Consequently, there's no need to check for containerLenNil here.
*/ -}}
func (d *Decoder) {{ .MethodNamePfx "fastpathDec" false }}R(f *codecFnInfo, rv reflect.Value) {
	containerLen := d.mapStart(d.d.ReadMapStart())
    {{/*
	if containerLen == containerLenNil {
		if rv.Kind() == reflect.Ptr {
			*(rv2i(rv).(*map[{{ .MapKey }}]{{ .Elem }})) = nil
		}
        return
	}
    */ -}}
	if rv.Kind() == reflect.Ptr {
		vp, _ := rv2i(rv).(*map[{{ .MapKey }}]{{ .Elem }})
		if *vp == nil {
			*vp = make(map[{{ .MapKey }}]{{ .Elem }}, decInferLen(containerLen, d.h.MaxInitLen, {{ .Size }}))
		}
		if containerLen != 0 {
			fastpathTV.{{ .MethodNamePfx "Dec" false }}L(*vp, containerLen, d)
		}
	} else if containerLen != 0 {
		fastpathTV.{{ .MethodNamePfx "Dec" false }}L(rv2i(rv).(map[{{ .MapKey }}]{{ .Elem }}), containerLen, d)
	}
	d.mapEnd()
}
func (f fastpathT) {{ .MethodNamePfx "Dec" false }}X(vp *map[{{ .MapKey }}]{{ .Elem }}, d *Decoder) {
	containerLen := d.mapStart(d.d.ReadMapStart())
	if containerLen == containerLenNil {
		*vp = nil
	} else {
		if *vp == nil {
			*vp = make(map[{{ .MapKey }}]{{ .Elem }}, decInferLen(containerLen, d.h.MaxInitLen, {{ .Size }}))
		}
		if containerLen != 0 {
			f.{{ .MethodNamePfx "Dec" false }}L(*vp, containerLen, d)
		}
		d.mapEnd()
	}
}
func (fastpathT) {{ .MethodNamePfx "Dec" false }}L(v map[{{ .MapKey }}]{{ .Elem }}, containerLen int, d *Decoder) {
	{{/* No need to check if containerLen == containerLenNil, as that is checked by R and L above  */ -}}
	if v == nil {
		d.errorf("cannot decode into nil map[{{ .MapKey }}]{{ .Elem }} given stream length: %v", containerLen)
        {{/* d.swallowMapContents(containerLen) */ -}}
		return
	}
	{{if eq .Elem "interface{}" }}mapGet := v != nil && !d.h.MapValueReset && !d.h.InterfaceReset
    {{else if eq .Elem "bytes" "[]byte" }}mapGet := v != nil && !d.h.MapValueReset
    {{end -}}
    var mk {{ .MapKey }}
	var mv {{ .Elem }}
	hasLen := containerLen > 0
    for j := 0; d.containerNext(j, containerLen, hasLen); j++ {
		d.mapElemKey()
		{{ if eq .MapKey "interface{}" }}mk = nil 
		d.decode(&mk)
		if bv, bok := mk.([]byte); bok {
			mk = d.stringZC(bv) {{/* // maps cannot have []byte as key. switch to string. */}}
		}{{ else }}mk = {{ decmd .MapKey true }}{{ end }}
		d.mapElemValue()
		{{ if eq .Elem "interface{}" "[]byte" "bytes" -}}
		if mapGet { mv = v[mk] } else { mv = nil }
		{{ end -}}
		{{ if eq .Elem "interface{}" -}}
		d.decode(&mv)
		{{ else if eq .Elem "[]byte" "bytes" -}}
		mv = d.decodeBytesInto(mv)
		{{ else -}}
		mv = {{ decmd .Elem false }}
		{{ end -}}
		v[mk] = mv
	}
}
{{end}}{{end}}{{end}}