如何确认交易

不可逆区块和不可逆交易

在GXChain上，被2/3以上公信节点确认的区块，我们定义为不可逆区块，即最终确认区块(相当于Bitcoin的6个区块确认)。所有在不可逆区块中的交易，则成为不可逆交易。因此，判断某一笔交易是否不可逆，是通过判断这笔交易是否出现在不可逆区块中来实现的。

不可逆交易的意义重大，可以用于转账确认、交易所充值确认等场景。主要的思路是通过遍历不可逆区块来查询相关的交易。

Step1: 获取最后不可逆区块号

获取动态全局属性对象

request:

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

response:

{
    "id":1,
    "jsonrpc":"2.0",
    "result":{
        "id":"2.1.0",
        "head_block_number":16757465, // 最新区块号
        "head_block_id":"00ffb2d9f6e344f2190a8dfba58baaadd49e76c4", // 最新区块id
        "time":"2019-01-28T06:08:00", // 区块头时间
        "current_witness":"1.6.52",
        "next_maintenance_time":"2019-01-28T06:40:00",
        "last_budget_time":"2019-01-28T05:40:00",
        "witness_budget":3065824,
        "accounts_registered_this_interval":2,
        "recently_missed_count":0,
        "current_aslot":16958091,
        "recent_slots_filled":"340282366920938463463374607431768211455",
        "dynamic_flags":0,
        "last_irreversible_block_num":16757449 // 最后不可逆区块号
    }
}

其中last_irreversible_block_num为最后不可逆区块号，当前区块链中所有小于last_irreversible_block_num的区块，都是不可逆区块，即最终确认的区块。

Step2: 遍历不可逆区块

例如：判断某个txid为9df2d2a2804c235bb16428c44f71de9468409ae7的交易是否在不可逆区块中，我们会从交易发起的某个区块高度开始进行查询，一直到不可逆区块高度为止，如果发现返回的 transaction_ids数组中查询到这个txid，则证明该交易不可逆了，即交易被网络最终确认了。

request:

curl --data '{
    "jsonrpc": "2.0",
    "method": "call",
    "params": [0, "get_block", [17136876]],
    "id": 1
}' https://node1.gxb.io/rpc

response:

{
  "previous": "01057cebdee3cf922d8fa54c2f6a7e0f01e4528a",
  "timestamp": "2019-02-10T18:25:42",
  "witness": "1.6.83",
  "transaction_merkle_root": "e8fdfcbd168ae9da64826d93c2fb88d19ac5f9fc",
  "extensions": [],
  "witness_signature": "1f4aa0526cf96d40f1b7c971b9bd39c72818b5dce421b3ec4e730d2f720e4a3a8e2f6dfe2696f8a52e221f4bfb4f828eff8488d6c6131933fc85a01437893564db",
  "transactions": [
    {
      "ref_block_num": 31978,
      "ref_block_prefix": 301877440,
      "expiration": "2019-02-10T18:26:08",
      "operations": [
        [
          73,
          {
            "proxy_memo": "QmcPwEMDdceMqzGNc7CCuffG7GvQnCFDJGteZMhTNtSYaA",
            "fee": {
              "amount": 1,
              "asset_id": "1.3.5"
            },
            "request_params": {
              "from": "1.2.17539",
              "to": "1.2.46",
              "proxy_account": "1.2.693712",
              "amount": {
                "amount": 10000,
                "asset_id": "1.3.5"
              },
              "percentage": 1000,
              "memo": "0ddad68dcb985a8031ff1a60c7984d36",
              "expiration": "2019-02-10T18:55:38",
              "signatures": [
                "2016918af85ee94ce72cf46f0dd8c0dec3e55eba9cf7b892e582f15b10f2949a3f7a6e4f9bdb1470414da2098032132c2ceb7725a9183fe2fe0eaa2b87c087ab88"
              ]
            },
            "extensions": []
          }
        ]
      ],
      "extensions": [],
      "signatures": [
        "1b0a289b4322ea6f522f7400bc368673a60aec7c28da463fcebf338a591cf7d8c8081ca39533a7ae28346cea503745804064f3d9f946f9bb2a13d5a04a3f751cfc"
      ],
      "operation_results": [
        [
          0,
          {}
        ]
      ]
    },
    {
      "ref_block_num": 31979,
      "ref_block_prefix": 2463097822,
      "expiration": "2019-02-10T18:26:09",
      "operations": [
        [
          0,
          {
            "fee": {
              "amount": 1000,
              "asset_id": "1.3.1"
            },
            "from": "1.2.19643",
            "to": "1.2.1061995",
            "amount": {
              "amount": "20916437581",
              "asset_id": "1.3.1"
            },
            "extensions": []
          }
        ]
      ],
      "extensions": [],
      "signatures": [
        "1f1918828badce7d0f0a05ee5890aba48dafe1e59f9ceb3a680f8abdaa17546c827f4302988d51857d1b89188bb2ba426410015c2d627cfa2dfa44c441348d3105"
      ],
      "operation_results": [
        [
          0,
          {}
        ]
      ]
    },
    {
      "ref_block_num": 31979,
      "ref_block_prefix": 2463097822,
      "expiration": "2019-02-10T18:26:09",
      "operations": [
        [
          73,
          {
            "proxy_memo": "QmTK6dHnEixSNoWgB14j1ZujKhT1RjEgXvUVJtcdWwJoTX",
            "fee": {
              "amount": 1,
              "asset_id": "1.3.5"
            },
            "request_params": {
              "from": "1.2.3840",
              "to": "1.2.46",
              "proxy_account": "1.2.693712",
              "amount": {
                "amount": 10000,
                "asset_id": "1.3.5"
              },
              "percentage": 1000,
              "memo": "5bfa26ee65ddc08558a8bf0f01dfe93a",
              "expiration": "2019-02-10T18:55:41",
              "signatures": [
                "2041dafb5c38ecc885f730af79cf741f5fc50c0f5b24c4f2d9fbfca7a34009394b3efea5ef426f4f7eb864431c8f9462b31a0e08af7fa6367b99d5673c502fe473"
              ]
            },
            "extensions": []
          }
        ]
      ],
      "extensions": [],
      "signatures": [
        "1b15649c701dad9aa38fc14ef85e28de849637a390fd46765c2960073f3993522d6d2a0e795f5c30005877cddafbcd926a9d94be6a763607d24b5fbf9e2b03fef2"
      ],
      "operation_results": [
        [
          0,
          {}
        ]
      ]
    }
  ],
  "block_id": "01057cecdc861a10a7c52052a1f681212fd99547",
  "signing_key": "GXC7iFA4ejkfbYQ8f7xR8rQ6dEANLqqFHKm3evo9NgCbtbx9aivXd",
  "transaction_ids": [
    "b53c8626bae9e17a07457fccca350c8edac42888",
    "9df2d2a2804c235bb16428c44f71de9468409ae7",
    "26a893ed6f6fd1b9781262c750dc8905a9af2add"
  ]
}