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unpack.go
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unpack.go
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//<developer>
// <name>linapex 曹一峰</name>
// <email>linapex@163.com</email>
// <wx>superexc</wx>
// <qqgroup>128148617</qqgroup>
// <url>https://jsq.ink</url>
// <role>pku engineer</role>
// <date>2019-03-16 12:09:26</date>
//</624342584155705344>
package abi
import (
"encoding/binary"
"fmt"
"math/big"
"reflect"
"github.com/ethereum/go-ethereum/common"
)
//根据整数的类型读取整数
func readInteger(kind reflect.Kind, b []byte) interface{} {
switch kind {
case reflect.Uint8:
return b[len(b)-1]
case reflect.Uint16:
return binary.BigEndian.Uint16(b[len(b)-2:])
case reflect.Uint32:
return binary.BigEndian.Uint32(b[len(b)-4:])
case reflect.Uint64:
return binary.BigEndian.Uint64(b[len(b)-8:])
case reflect.Int8:
return int8(b[len(b)-1])
case reflect.Int16:
return int16(binary.BigEndian.Uint16(b[len(b)-2:]))
case reflect.Int32:
return int32(binary.BigEndian.Uint32(b[len(b)-4:]))
case reflect.Int64:
return int64(binary.BigEndian.Uint64(b[len(b)-8:]))
default:
return new(big.Int).SetBytes(b)
}
}
//读BoL
func readBool(word []byte) (bool, error) {
for _, b := range word[:31] {
if b != 0 {
return false, errBadBool
}
}
switch word[31] {
case 0:
return false, nil
case 1:
return true, nil
default:
return false, errBadBool
}
}
//函数类型只是在末尾带有函数选择签名的地址。
//这通过始终将其显示为24个数组(address+sig=24字节)来强制执行该标准。
func readFunctionType(t Type, word []byte) (funcTy [24]byte, err error) {
if t.T != FunctionTy {
return [24]byte{}, fmt.Errorf("abi: invalid type in call to make function type byte array")
}
if garbage := binary.BigEndian.Uint64(word[24:32]); garbage != 0 {
err = fmt.Errorf("abi: got improperly encoded function type, got %v", word)
} else {
copy(funcTy[:], word[0:24])
}
return
}
//通过反射,创建要从中读取的固定数组
func readFixedBytes(t Type, word []byte) (interface{}, error) {
if t.T != FixedBytesTy {
return nil, fmt.Errorf("abi: invalid type in call to make fixed byte array")
}
//转换
array := reflect.New(t.Type).Elem()
reflect.Copy(array, reflect.ValueOf(word[0:t.Size]))
return array.Interface(), nil
}
func getFullElemSize(elem *Type) int {
//所有其他元素都应计为32(切片有指向各个元素的指针)
size := 32
//数组将其包装,每个元素的大小相同
for elem.T == ArrayTy {
size *= elem.Size
elem = elem.Elem
}
return size
}
//迭代解包元素
func forEachUnpack(t Type, output []byte, start, size int) (interface{}, error) {
if size < 0 {
return nil, fmt.Errorf("cannot marshal input to array, size is negative (%d)", size)
}
if start+32*size > len(output) {
return nil, fmt.Errorf("abi: cannot marshal in to go array: offset %d would go over slice boundary (len=%d)", len(output), start+32*size)
}
//此值将成为切片或数组,具体取决于类型
var refSlice reflect.Value
if t.T == SliceTy {
//申报我们的切片
refSlice = reflect.MakeSlice(t.Type, size, size)
} else if t.T == ArrayTy {
//声明我们的数组
refSlice = reflect.New(t.Type).Elem()
} else {
return nil, fmt.Errorf("abi: invalid type in array/slice unpacking stage")
}
//数组具有压缩元素,从而导致较长的解包步骤。
//每个元素的切片只有32个字节(指向内容)。
elemSize := 32
if t.T == ArrayTy {
elemSize = getFullElemSize(t.Elem)
}
for i, j := start, 0; j < size; i, j = i+elemSize, j+1 {
inter, err := toGoType(i, *t.Elem, output)
if err != nil {
return nil, err
}
//将项目附加到反射切片
refSlice.Index(j).Set(reflect.ValueOf(inter))
}
//返回接口
return refSlice.Interface(), nil
}
//togotype解析输出字节并递归地分配这些字节的值
//符合ABI规范的GO类型。
func toGoType(index int, t Type, output []byte) (interface{}, error) {
if index+32 > len(output) {
return nil, fmt.Errorf("abi: cannot marshal in to go type: length insufficient %d require %d", len(output), index+32)
}
var (
returnOutput []byte
begin, end int
err error
)
//如果需要长度前缀,请查找返回的起始单词和大小。
if t.requiresLengthPrefix() {
begin, end, err = lengthPrefixPointsTo(index, output)
if err != nil {
return nil, err
}
} else {
returnOutput = output[index : index+32]
}
switch t.T {
case SliceTy:
return forEachUnpack(t, output, begin, end)
case ArrayTy:
return forEachUnpack(t, output, index, t.Size)
case StringTy: //变量数组写在返回字节的末尾
return string(output[begin : begin+end]), nil
case IntTy, UintTy:
return readInteger(t.Kind, returnOutput), nil
case BoolTy:
return readBool(returnOutput)
case AddressTy:
return common.BytesToAddress(returnOutput), nil
case HashTy:
return common.BytesToHash(returnOutput), nil
case BytesTy:
return output[begin : begin+end], nil
case FixedBytesTy:
return readFixedBytes(t, returnOutput)
case FunctionTy:
return readFunctionType(t, returnOutput)
default:
return nil, fmt.Errorf("abi: unknown type %v", t.T)
}
}
//将一个32字节的切片解释为一个偏移量,然后确定要寻找哪一个指示来解码该类型。
func lengthPrefixPointsTo(index int, output []byte) (start int, length int, err error) {
bigOffsetEnd := big.NewInt(0).SetBytes(output[index : index+32])
bigOffsetEnd.Add(bigOffsetEnd, common.Big32)
outputLength := big.NewInt(int64(len(output)))
if bigOffsetEnd.Cmp(outputLength) > 0 {
return 0, 0, fmt.Errorf("abi: cannot marshal in to go slice: offset %v would go over slice boundary (len=%v)", bigOffsetEnd, outputLength)
}
if bigOffsetEnd.BitLen() > 63 {
return 0, 0, fmt.Errorf("abi offset larger than int64: %v", bigOffsetEnd)
}
offsetEnd := int(bigOffsetEnd.Uint64())
lengthBig := big.NewInt(0).SetBytes(output[offsetEnd-32 : offsetEnd])
totalSize := big.NewInt(0)
totalSize.Add(totalSize, bigOffsetEnd)
totalSize.Add(totalSize, lengthBig)
if totalSize.BitLen() > 63 {
return 0, 0, fmt.Errorf("abi length larger than int64: %v", totalSize)
}
if totalSize.Cmp(outputLength) > 0 {
return 0, 0, fmt.Errorf("abi: cannot marshal in to go type: length insufficient %v require %v", outputLength, totalSize)
}
start = int(bigOffsetEnd.Uint64())
length = int(lengthBig.Uint64())
return
}