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https://github.com/nspcc-dev/neo-go.git
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96 lines
2.6 KiB
Go
96 lines
2.6 KiB
Go
package io
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import (
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"fmt"
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"reflect"
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)
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// This structure is used to calculate the wire size of the serializable
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// structure. It's an io.Writer that doesn't do any real writes, but instead
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// just counts the number of bytes to be written.
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type counterWriter struct {
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counter int
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}
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// Write implements the io.Writer interface.
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func (cw *counterWriter) Write(p []byte) (int, error) {
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n := len(p)
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cw.counter += n
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return n, nil
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}
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// getVarIntSize returns the size in number of bytes of a variable integer.
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// (reference: GetVarSize(int value), https://github.com/neo-project/neo/blob/master/neo/IO/Helper.cs)
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func getVarIntSize(value int) int {
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var size uintptr
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if value < 0xFD {
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size = 1 // unit8
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} else if value <= 0xFFFF {
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size = 3 // byte + uint16
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} else {
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size = 5 // byte + uint32
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}
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return int(size)
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}
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// GetVarSize returns the number of bytes in a serialized variable. It supports ints/uints (estimating
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// them with variable-length encoding that is used in NEO), strings, pointers to Serializable structures,
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// slices and arrays of ints/uints or Serializable structures. It's similar to GetVarSize<T>(this T[] value)
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// used in C#, but differs in that it also supports things like Uint160 or Uint256.
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func GetVarSize(value interface{}) int {
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v := reflect.ValueOf(value)
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switch v.Kind() {
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case reflect.String:
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valueSize := len([]byte(v.String()))
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return getVarIntSize(valueSize) + valueSize
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case reflect.Int,
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reflect.Int8,
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reflect.Int16,
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reflect.Int32,
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reflect.Int64:
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return getVarIntSize(int(v.Int()))
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case reflect.Uint,
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reflect.Uint8,
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reflect.Uint16,
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reflect.Uint32,
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reflect.Uint64:
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return getVarIntSize(int(v.Uint()))
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case reflect.Ptr:
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vser, ok := v.Interface().(Serializable)
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if !ok {
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panic("unable to calculate GetVarSize for a non-Serializable pointer")
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}
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cw := counterWriter{}
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w := NewBinWriterFromIO(&cw)
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vser.EncodeBinary(w)
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if w.Err != nil {
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panic(fmt.Sprintf("error serializing %s: %s", reflect.TypeOf(value), w.Err.Error()))
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}
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return cw.counter
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case reflect.Slice, reflect.Array:
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valueLength := v.Len()
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valueSize := 0
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if valueLength != 0 {
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switch reflect.ValueOf(value).Index(0).Interface().(type) {
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case Serializable:
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for i := 0; i < valueLength; i++ {
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valueSize += GetVarSize(v.Index(i).Interface())
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}
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case uint8, int8:
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valueSize = valueLength
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case uint16, int16:
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valueSize = valueLength * 2
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case uint32, int32:
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valueSize = valueLength * 4
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case uint64, int64:
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valueSize = valueLength * 8
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}
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}
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return getVarIntSize(valueLength) + valueSize
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default:
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panic(fmt.Sprintf("unable to calculate GetVarSize, %s", reflect.TypeOf(value)))
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}
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}
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