whatcanGOwrong
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@@ -0,0 +1,249 @@
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package ebpf
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import (
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"bytes"
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"encoding"
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"encoding/binary"
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"errors"
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"fmt"
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"reflect"
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"runtime"
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"sync"
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"unsafe"
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"github.com/cilium/ebpf/internal"
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"github.com/cilium/ebpf/internal/sys"
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)
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// marshalPtr converts an arbitrary value into a pointer suitable
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// to be passed to the kernel.
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//
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// As an optimization, it returns the original value if it is an
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// unsafe.Pointer.
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func marshalPtr(data interface{}, length int) (sys.Pointer, error) {
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if ptr, ok := data.(unsafe.Pointer); ok {
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return sys.NewPointer(ptr), nil
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}
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buf, err := marshalBytes(data, length)
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if err != nil {
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return sys.Pointer{}, err
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}
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return sys.NewSlicePointer(buf), nil
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}
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// marshalBytes converts an arbitrary value into a byte buffer.
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//
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// Prefer using Map.marshalKey and Map.marshalValue if possible, since
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// those have special cases that allow more types to be encoded.
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//
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// Returns an error if the given value isn't representable in exactly
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// length bytes.
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func marshalBytes(data interface{}, length int) (buf []byte, err error) {
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if data == nil {
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return nil, errors.New("can't marshal a nil value")
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}
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switch value := data.(type) {
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case encoding.BinaryMarshaler:
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buf, err = value.MarshalBinary()
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case string:
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buf = []byte(value)
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case []byte:
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buf = value
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case unsafe.Pointer:
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err = errors.New("can't marshal from unsafe.Pointer")
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case Map, *Map, Program, *Program:
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err = fmt.Errorf("can't marshal %T", value)
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default:
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wr := internal.NewBuffer(make([]byte, 0, length))
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defer internal.PutBuffer(wr)
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err = binary.Write(wr, internal.NativeEndian, value)
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if err != nil {
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err = fmt.Errorf("encoding %T: %v", value, err)
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}
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buf = wr.Bytes()
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}
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if err != nil {
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return nil, err
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}
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if len(buf) != length {
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return nil, fmt.Errorf("%T doesn't marshal to %d bytes", data, length)
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}
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return buf, nil
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}
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func makeBuffer(dst interface{}, length int) (sys.Pointer, []byte) {
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if ptr, ok := dst.(unsafe.Pointer); ok {
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return sys.NewPointer(ptr), nil
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}
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buf := make([]byte, length)
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return sys.NewSlicePointer(buf), buf
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}
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var bytesReaderPool = sync.Pool{
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New: func() interface{} {
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return new(bytes.Reader)
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},
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}
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// unmarshalBytes converts a byte buffer into an arbitrary value.
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//
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// Prefer using Map.unmarshalKey and Map.unmarshalValue if possible, since
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// those have special cases that allow more types to be encoded.
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//
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// The common int32 and int64 types are directly handled to avoid
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// unnecessary heap allocations as happening in the default case.
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func unmarshalBytes(data interface{}, buf []byte) error {
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switch value := data.(type) {
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case unsafe.Pointer:
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dst := unsafe.Slice((*byte)(value), len(buf))
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copy(dst, buf)
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runtime.KeepAlive(value)
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return nil
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case Map, *Map, Program, *Program:
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return fmt.Errorf("can't unmarshal into %T", value)
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case encoding.BinaryUnmarshaler:
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return value.UnmarshalBinary(buf)
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case *string:
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*value = string(buf)
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return nil
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case *[]byte:
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*value = buf
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return nil
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case *int32:
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if len(buf) < 4 {
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return errors.New("int32 requires 4 bytes")
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}
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*value = int32(internal.NativeEndian.Uint32(buf))
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return nil
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case *uint32:
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if len(buf) < 4 {
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return errors.New("uint32 requires 4 bytes")
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}
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*value = internal.NativeEndian.Uint32(buf)
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return nil
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case *int64:
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if len(buf) < 8 {
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return errors.New("int64 requires 8 bytes")
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}
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*value = int64(internal.NativeEndian.Uint64(buf))
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return nil
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case *uint64:
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if len(buf) < 8 {
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return errors.New("uint64 requires 8 bytes")
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}
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*value = internal.NativeEndian.Uint64(buf)
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return nil
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case string:
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return errors.New("require pointer to string")
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case []byte:
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return errors.New("require pointer to []byte")
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default:
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rd := bytesReaderPool.Get().(*bytes.Reader)
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rd.Reset(buf)
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defer bytesReaderPool.Put(rd)
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if err := binary.Read(rd, internal.NativeEndian, value); err != nil {
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return fmt.Errorf("decoding %T: %v", value, err)
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}
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return nil
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}
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}
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// marshalPerCPUValue encodes a slice containing one value per
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// possible CPU into a buffer of bytes.
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//
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// Values are initialized to zero if the slice has less elements than CPUs.
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//
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// slice must have a type like []elementType.
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func marshalPerCPUValue(slice interface{}, elemLength int) (sys.Pointer, error) {
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sliceType := reflect.TypeOf(slice)
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if sliceType.Kind() != reflect.Slice {
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return sys.Pointer{}, errors.New("per-CPU value requires slice")
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}
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possibleCPUs, err := internal.PossibleCPUs()
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if err != nil {
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return sys.Pointer{}, err
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}
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sliceValue := reflect.ValueOf(slice)
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sliceLen := sliceValue.Len()
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if sliceLen > possibleCPUs {
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return sys.Pointer{}, fmt.Errorf("per-CPU value exceeds number of CPUs")
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}
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alignedElemLength := internal.Align(elemLength, 8)
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buf := make([]byte, alignedElemLength*possibleCPUs)
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for i := 0; i < sliceLen; i++ {
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elem := sliceValue.Index(i).Interface()
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elemBytes, err := marshalBytes(elem, elemLength)
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if err != nil {
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return sys.Pointer{}, err
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}
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offset := i * alignedElemLength
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copy(buf[offset:offset+elemLength], elemBytes)
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}
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return sys.NewSlicePointer(buf), nil
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}
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// unmarshalPerCPUValue decodes a buffer into a slice containing one value per
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// possible CPU.
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//
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// valueOut must have a type like *[]elementType
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func unmarshalPerCPUValue(slicePtr interface{}, elemLength int, buf []byte) error {
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slicePtrType := reflect.TypeOf(slicePtr)
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if slicePtrType.Kind() != reflect.Ptr || slicePtrType.Elem().Kind() != reflect.Slice {
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return fmt.Errorf("per-cpu value requires pointer to slice")
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}
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possibleCPUs, err := internal.PossibleCPUs()
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if err != nil {
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return err
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}
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sliceType := slicePtrType.Elem()
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slice := reflect.MakeSlice(sliceType, possibleCPUs, possibleCPUs)
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sliceElemType := sliceType.Elem()
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sliceElemIsPointer := sliceElemType.Kind() == reflect.Ptr
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if sliceElemIsPointer {
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sliceElemType = sliceElemType.Elem()
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}
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step := len(buf) / possibleCPUs
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if step < elemLength {
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return fmt.Errorf("per-cpu element length is larger than available data")
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}
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for i := 0; i < possibleCPUs; i++ {
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var elem interface{}
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if sliceElemIsPointer {
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newElem := reflect.New(sliceElemType)
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slice.Index(i).Set(newElem)
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elem = newElem.Interface()
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} else {
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elem = slice.Index(i).Addr().Interface()
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}
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// Make a copy, since unmarshal can hold on to itemBytes
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elemBytes := make([]byte, elemLength)
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copy(elemBytes, buf[:elemLength])
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err := unmarshalBytes(elem, elemBytes)
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if err != nil {
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return fmt.Errorf("cpu %d: %w", i, err)
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}
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buf = buf[step:]
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}
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reflect.ValueOf(slicePtr).Elem().Set(slice)
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return nil
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}
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