split files

feature_reflect_array.go

@@ -0,0 +1,104 @@
+package jsoniter
+
+import (
+	"unsafe"
+	"reflect"
+	"io"
+	"fmt"
+)
+
+type sliceDecoder struct {
+	sliceType   reflect.Type
+	elemType    reflect.Type
+	elemDecoder Decoder
+}
+
+// sliceHeader is a safe version of SliceHeader used within this package.
+type sliceHeader struct {
+	Data unsafe.Pointer
+	Len  int
+	Cap  int
+}
+
+func (decoder *sliceDecoder) decode(ptr unsafe.Pointer, iter *Iterator) {
+	decoder.doDecode(ptr, iter)
+	if iter.Error != nil && iter.Error != io.EOF {
+		iter.Error = fmt.Errorf("%v: %s", decoder.sliceType, iter.Error.Error())
+	}
+}
+
+func (decoder *sliceDecoder) doDecode(ptr unsafe.Pointer, iter *Iterator) {
+	slice := (*sliceHeader)(ptr)
+	reuseSlice(slice, decoder.sliceType, 4)
+	if !iter.ReadArray() {
+		return
+	}
+	offset := uintptr(0)
+	decoder.elemDecoder.decode(unsafe.Pointer(uintptr(slice.Data) + offset), iter)
+	if !iter.ReadArray() {
+		slice.Len = 1
+		return
+	}
+	offset += decoder.elemType.Size()
+	decoder.elemDecoder.decode(unsafe.Pointer(uintptr(slice.Data) + offset), iter)
+	if !iter.ReadArray() {
+		slice.Len = 2
+		return
+	}
+	offset += decoder.elemType.Size()
+	decoder.elemDecoder.decode(unsafe.Pointer(uintptr(slice.Data) + offset), iter)
+	if !iter.ReadArray() {
+		slice.Len = 3
+		return
+	}
+	offset += decoder.elemType.Size()
+	decoder.elemDecoder.decode(unsafe.Pointer(uintptr(slice.Data) + offset), iter)
+	slice.Len = 4
+	for iter.ReadArray() {
+		growOne(slice, decoder.sliceType, decoder.elemType)
+		offset += decoder.elemType.Size()
+		decoder.elemDecoder.decode(unsafe.Pointer(uintptr(slice.Data) + offset), iter)
+	}
+}
+
+// grow grows the slice s so that it can hold extra more values, allocating
+// more capacity if needed. It also returns the old and new slice lengths.
+func growOne(slice *sliceHeader, sliceType reflect.Type, elementType reflect.Type) {
+	newLen := slice.Len + 1
+	if newLen <= slice.Cap {
+		slice.Len = newLen
+		return
+	}
+	newCap := slice.Cap
+	if newCap == 0 {
+		newCap = 1
+	} else {
+		for newCap < newLen {
+			if slice.Len < 1024 {
+				newCap += newCap
+			} else {
+				newCap += newCap / 4
+			}
+		}
+	}
+	dst := unsafe.Pointer(reflect.MakeSlice(sliceType, newLen, newCap).Pointer())
+	// copy old array into new array
+	originalBytesCount := uintptr(slice.Len) * elementType.Size()
+	srcPtr := (*[1 << 30]byte)(slice.Data)
+	dstPtr := (*[1 << 30]byte)(dst)
+	for i := uintptr(0); i < originalBytesCount; i++ {
+		dstPtr[i] = srcPtr[i]
+	}
+	slice.Len = newLen
+	slice.Cap = newCap
+	slice.Data = dst
+}
+
+func reuseSlice(slice *sliceHeader, sliceType reflect.Type, expectedCap int) {
+	if expectedCap <= slice.Cap {
+		return
+	}
+	dst := unsafe.Pointer(reflect.MakeSlice(sliceType, 0, expectedCap).Pointer())
+	slice.Cap = expectedCap
+	slice.Data = dst
+}