如何发起链上交易

Step1: 构造交易

{
  "ref_block_num": 54701, // an exist block num
  "ref_block_prefix": 2861949695, // The exist block id
  "expiration": "2019-01-18T03:35:54", // transaction expiration date, max expiration = current + 24hours
  "operations": [
   [
      0, // operation id
      { // operation
        "fee": {
          "amount": 1179,
          "asset_id": "1.3.1"
        },
        "from": "1.2.937396",
        "to": "1.2.19645",
        "amount": {
          "amount": 173600000,
          "asset_id": "1.3.1"
        },
        "memo": { // memo
          "from": "GXC6cUP6LvdpcfC9G4TMre4yxB3PxttUjVK1ybybgt63ZtEKCXamC", // memo_key of from account
          "to": "GXC7o71VExYFoFJKtduFXEF15jgPdbmC1tdyT8BPCpnzCTeFiXEog", // memo_key of to account
          "nonce": 1, // nonce of encryption key
          "message": "15e06e19346d8f9c2d5355abcf5fffaa" // ECIES encrypted message
        },
        "extensions": []
      }
    ]
  ],
  "extensions": [],
  "signatures": []
}

从上面的交易结构中我们看到,整个交易主要分为三部分: 区块头信息操作数组签名

区块头信息包含3个字段:

  • ref_block_num = head_block_num & 0xFFFF (head_block_num mod 65535)
  • ref_block_prefix = hex2Num(head_block_id.substring(12,14)+head_block_id.substring(10,12)+head_block_id.substring(8,10))

其中head_block_numref_block_prefix可以通过get_dynamic_global_properties来获得

curl -XPOST --data '{
    "jsonrpc": "2.0",
    "method": "call",
    "params": [0, "get_dynamic_global_properties", []],
    "id": 1
}' https://node1.gxb.io/rpc

参考代码:

上面的交易是未完成签名的,这样的交易无法在区块链上进行广播,接下来我们需要对交易进行序列化签名

Step2: 交易序列化

GXChain链上一共76种不同的交易消息体结构,交易序列化采用一种自定义的Protocol Buffer协议,实现了以下基础类型序列化(toByteBuffer)和反序列化(fromByteBuffer):

类型 描述
uint8 单字节无符号整型
uint16 2字节无符号整型
uint32 4字节无符号整型
uint64 8字节无符号整型
int64 8字节整型
bool 布尔类型
string 字符串
bytes 字节数组
array 数组类型(仅支持自定义类型)
protocol_id_type 协议id类型(如1.3.1, 1.2.1)
vote_id 投票id类型(如0:11, 1:13)
map key-value类型
set 集合类型(和array的区别是仅支持整形和字符串类型)
public_key 公钥类型
time_point_second 时间戳类型
name_type base32类型
optional 可空类型
future_extensions 扩展类型

我们来看一下常见的转账操作,是这样定义的:

export const transfer = new Serializer (
    "transfer",
    {
        fee: asset,
        from: protocol_id_type ("account"),
        to: protocol_id_type ("account"),
        amount: asset,
        memo: optional (memo_data),
        extensions: set (future_extensions)
    }
);

Serializer实例提供fromBuffer和toBuffer方法,可以将一个JSON根据所定义的结构进行序列化和反序列化。Serializer可以相互嵌套,序列化过程中,在碰到非基础类型时,会进行递归序列化, 如转账消息体中的memo字段是这样定义的:

export const memo_data = new Serializer (
    "memo_data",
    {
        from: public_key,
        to: public_key,
        nonce: uint64,
        message: bytes ()
    }
);

序列化和反序列化的细节,可以参考以下源码:

假如你是一个开发者,在交易封装的过程中,序列化的过程是比较头疼的,不用担心,我们已经为你准备好了现成的tx_serializer

tx_serializer.js提供了两个方法

  1. 智能合约参数序列化
var serializeCallData = function serializeCallData(action, params, abi)
  1. 交易序列化
var serializeTransaction = function serializeTransaction(transaction)

所以问题回归到如何在程序中调用tx_serializer.js对交易消息体进行序列化,可以参考gxclient-ios的实现:

首先我们构造了一个JS执行环境(jsContext),加载tx_serializer.js

+(JSContext*)jsContext{
    static dispatch_once_t onceToken;
    static JSContext* instance;
    dispatch_once(&onceToken, ^{
        NSBundle* bundle = [NSBundle bundleForClass:[GXUtil class]];
        NSString * path = [bundle pathForResource:@"gxclient.bundle/tx_serializer.min" ofType:@"js"];
        NSData * jsData = [[NSData alloc]initWithContentsOfFile:path];
        NSString * jsCode = [[NSString alloc]initWithData:jsData encoding:NSUTF8StringEncoding];
        instance=[[JSContext alloc] init];
        [instance evaluateScript:jsCode];
    });

    return instance;
}

然后我们就可以调用jsContext的两个方法对合约调用参数和交易进行序列化了

+(NSString*) serialize_action_data:(NSString*)action params:(NSDictionary*)params abi:(NSDictionary*)abi{
    NSString* jsCode = [NSString stringWithFormat:@"serializer.serializeCallData('%@',%@,%@).toString('hex')",action, [params json],[abi json]];
    NSString* result = [[[GXUtil jsContext] evaluateScript:jsCode] toString];
    return result;
}

+(NSString*) serialize_transaction:(NSDictionary*)transaction{
    NSString* jsCode = [NSString stringWithFormat:@"serializer.serializeTransaction(%@).toString('hex')", [transaction json]];
    NSString* result = [[[GXUtil jsContext] evaluateScript:jsCode] toString];
    return result;
}

通过序列化,我们把一个json结构的交易压缩成了一个byte数组,接下来就是对这个byte数组进行签名

Step3: 交易签名

let tx_buffer = serializer.serializeTransaction(tx);
let privateKey = ecc.PrivateKey.fromWif(private_key);
let signature = ecc.Signature.signBuffer(tx_buffer, privateKey).toHex();
tx.signatures=[signature];

于是我们得到了签名好的交易

{
  "ref_block_num": 54701, // an exist block num
  "ref_block_prefix": 2861949695, // The exist block id
  "expiration": "2019-01-18T03:35:54", // transaction expiration date, max expiration = current + 24hours
  "operations": [
   [
      0, // operation id
      { // operation
        "fee": {
          "amount": 1179,
          "asset_id": "1.3.1"
        },
        "from": "1.2.937396",
        "to": "1.2.19645",
        "amount": {
          "amount": 173600000,
          "asset_id": "1.3.1"
        },
        "memo": {
          "from": "GXC6cUP6LvdpcfC9G4TMre4yxB3PxttUjVK1ybybgt63ZtEKCXamC", // memo_key of from account
          "to": "GXC7o71VExYFoFJKtduFXEF15jgPdbmC1tdyT8BPCpnzCTeFiXEog", // memo_key of to account
          "nonce": 1, // nonce of encryption key
          "message": "15e06e19346d8f9c2d5355abcf5fffaa" // ECIES encrypted message
        },
        "extensions": []
      }
    ]
  ],
  "extensions": [],
  "signatures": [
    "1b4a899ab4831ee6c0e7bb3825cfbbf47947d5861671cd8f8e6c61436c7f71b0336622e98b2e29b1fa1f00ca697baa1a797e280c619cc04bab1645db19c87f78aa"
  ]
}

Step4: 广播交易

通过调用broadcast_transaction_synchronous,我们就可以把交易推送到接入点上向整个网络广播了

curl --data '{
    "jsonrpc": "2.0",
    "method": "call",
    "params": [2,"broadcast_transaction_synchronous",[tx]],
    "id": 1
}' https://node23.gxb.io/rpc
上次更新: 2019-2-15 17:59:10