Add type addrShift to enable bigger encoder/decoder cache

Change-Id: I630fa501f3b96702b69a40bc0b2f79f4db2a57eb

codec.go

@@ -3,6 +3,7 @@ package json
 import (
 	"fmt"
 	"reflect"
+	"sort"
 	"sync/atomic"
 	"unsafe"
 )
@@ -16,6 +17,7 @@ var (
 	cachedDecoderMap unsafe.Pointer // map[uintptr]decoder
 	baseTypeAddr     uintptr
 	maxTypeAddr      uintptr
+	typeAddrShift    uintptr
 )
 
 //go:linkname typelinks reflect.typelinks
@@ -35,8 +37,9 @@ func setupCodec() error {
 	section := sections[0]
 	offset := offsets[0]
 	var (
-		min uintptr = uintptr(^uint(0))
-		max uintptr = 0
+		min   uintptr = uintptr(^uint(0))
+		max   uintptr = 0
+		addrs         = make([]int, 0, 4*1024)
 	)
 	for i := 0; i < len(offset); i++ {
 		typ := (*rtype)(rtypeOff(section, offset[i]))
@@ -56,20 +59,43 @@ func setupCodec() error {
 				max = addr
 			}
 		}
+		addrs = append(addrs, int(addr))
 	}
 	addrRange := max - min
 	if addrRange == 0 {
 		return fmt.Errorf("failed to get address range of types")
 	}
-	if addrRange > maxAcceptableTypeAddrRange {
+	sort.Ints(addrs)
+	typeAddrShift = calcTypeOffsetShift(addrs)
+	cacheSize := addrRange >> typeAddrShift
+	if cacheSize > maxAcceptableTypeAddrRange {
 		return fmt.Errorf("too big address range %d", addrRange)
 	}
-	cachedDecoder = make([]decoder, addrRange)
+	cachedDecoder = make([]decoder, cacheSize)
 	baseTypeAddr = min
 	maxTypeAddr = max
 	return nil
 }
 
+func calcTypeOffsetShift(addrs []int) uintptr {
+	offset64 := true
+	offset32 := true
+	for i := 1; i < len(addrs); i++ {
+		if incr := addrs[i] - addrs[i-1]; incr&63 != 0 {
+			offset64 = false
+		} else if incr&31 != 0 {
+			offset32 = false
+		}
+	}
+	if offset64 {
+		return 6
+	}
+	if offset32 {
+		return 5
+	}
+	return 0
+}
+
 func init() {
 	_ = setupCodec()
 }

decode_compile_norace.go

@@ -10,7 +10,7 @@ func decodeCompileToGetDecoder(typ *rtype) (decoder, error) {
 		return decodeCompileToGetDecoderSlowPath(typeptr, typ)
 	}
 
-	index := typeptr - baseTypeAddr
+	index := (typeptr - baseTypeAddr) >> typeAddrShift
 	if dec := cachedDecoder[index]; dec != nil {
 		return dec, nil
 	}

decode_compile_race.go

@@ -15,7 +15,7 @@ func decodeCompileToGetDecoder(typ *rtype) (decoder, error) {
 		return decodeCompileToGetDecoderSlowPath(typeptr, typ)
 	}
 
-	index := typeptr - baseTypeAddr
+	index := (typeptr - baseTypeAddr) >> typeAddrShift
 	decMu.RLock()
 	if dec := cachedDecoder[index]; dec != nil {
 		decMu.RUnlock()

internal/encoder/compiler.go

@@ -27,7 +27,7 @@ func init() {
 	if typeAddr == nil {
 		typeAddr = &runtime.TypeAddr{}
 	}
-	cachedOpcodeSets = make([]*OpcodeSet, typeAddr.AddrRange)
+	cachedOpcodeSets = make([]*OpcodeSet, typeAddr.AddrRange>>typeAddr.AddrShift)
 }
 
 func loadOpcodeMap() map[uintptr]*OpcodeSet {

internal/encoder/compiler_norace.go

@@ -12,7 +12,7 @@ func CompileToGetCodeSet(typeptr uintptr) (*OpcodeSet, error) {
 	if typeptr > typeAddr.MaxTypeAddr {
 		return compileToGetCodeSetSlowPath(typeptr)
 	}
-	index := typeptr - typeAddr.BaseTypeAddr
+	index := (typeptr - typeAddr.BaseTypeAddr) >> typeAddr.AddrShift
 	if codeSet := cachedOpcodeSets[index]; codeSet != nil {
 		return codeSet, nil
 	}

internal/encoder/compiler_race.go

@@ -15,7 +15,7 @@ func CompileToGetCodeSet(typeptr uintptr) (*OpcodeSet, error) {
 	if typeptr > typeAddr.MaxTypeAddr {
 		return compileToGetCodeSetSlowPath(typeptr)
 	}
-	index := typeptr - typeAddr.BaseTypeAddr
+	index := (typeptr - typeAddr.BaseTypeAddr) >> typeAddr.AddrShift
 	setsMu.RLock()
 	if codeSet := cachedOpcodeSets[index]; codeSet != nil {
 		setsMu.RUnlock()

internal/runtime/type.go

@@ -2,6 +2,7 @@ package runtime
 
 import (
 	"reflect"
+	"sort"
 	"unsafe"
 )
 
@@ -19,6 +20,7 @@ type TypeAddr struct {
 	BaseTypeAddr uintptr
 	MaxTypeAddr  uintptr
 	AddrRange    uintptr
+	AddrShift    uintptr
 }
 
 var (
@@ -49,8 +51,9 @@ func AnalyzeTypeAddr() *TypeAddr {
 	section := sections[0]
 	offset := offsets[0]
 	var (
-		min uintptr = uintptr(^uint(0))
-		max uintptr = 0
+		min   uintptr = uintptr(^uint(0))
+		max   uintptr = 0
+		addrs         = make([]int, 0, 4*1024)
 	)
 	for i := 0; i < len(offset); i++ {
 		typ := (*Type)(rtypeOff(section, offset[i]))
@@ -70,18 +73,42 @@ func AnalyzeTypeAddr() *TypeAddr {
 				max = addr
 			}
 		}
+		addrs = append(addrs, int(addr))
 	}
 	addrRange := max - min
 	if addrRange == 0 {
 		return nil
 	}
-	if addrRange > maxAcceptableTypeAddrRange {
+	sort.Ints(addrs)
+	addrShift := calcTypeOffsetShift(addrs)
+	cacheSize := addrRange >> addrShift
+	if cacheSize > maxAcceptableTypeAddrRange {
 		return nil
 	}
 	typeAddr = &TypeAddr{
 		BaseTypeAddr: min,
 		MaxTypeAddr:  max,
 		AddrRange:    addrRange,
+		AddrShift:    addrShift,
 	}
 	return typeAddr
 }
+
+func calcTypeOffsetShift(addrs []int) uintptr {
+	offset64 := true
+	offset32 := true
+	for i := 1; i < len(addrs); i++ {
+		if incr := addrs[i] - addrs[i-1]; incr&63 != 0 {
+			offset64 = false
+		} else if incr&31 != 0 {
+			offset32 = false
+		}
+	}
+	if offset64 {
+		return 6
+	}
+	if offset32 {
+		return 5
+	}
+	return 0
+}