Android Web3j OOM解決詳解

更新時間：2018年07月16日 09:11:05 作者：沉默的范大叔

這篇文章主要介紹了Android Web3j OOM解決詳解，小編覺得挺不錯的，現(xiàn)在分享給大家，也給大家做個參考。一起跟隨小編過來看看吧

在Android客戶端使用Web3j創(chuàng)建錢包、導入錢包時都可能會產(chǎn)生OOM，相關issue在Github上已經(jīng)有所提及： https://github.com/web3j/web3j/issues/299 。這個問題在Web3j 3.0版本以前是沒有的，由于新版的Web3j使用spongycastle庫替換了lambdaworks庫，雖然在效率上提升了速度，但存在Android端的兼容性問題。

本項目代碼地址： https://github.com/uncleleonfan/WalletOOM.git

創(chuàng)建錢包OOM解決

在創(chuàng)建錢包時，如果創(chuàng)建一個Full Wallet，則會導致OOM：

public void onCreateFullWallet(View view) {
  String filePath = Environment.getExternalStorageDirectory().getAbsolutePath() + "/full";
  File file = new File(filePath);
  file.mkdirs();
  try {
    WalletUtils.generateFullNewWalletFile("a12345678", file);
  } catch (NoSuchAlgorithmException e) {
    e.printStackTrace();
  } catch (NoSuchProviderException e) {
    e.printStackTrace();
  } catch (InvalidAlgorithmParameterException e) {
    e.printStackTrace();
  } catch (CipherException e) {
    e.printStackTrace();
  } catch (IOException e) {
    e.printStackTrace();
  }
}

Log如下：

"Caused by: java.lang.OutOfMemoryError: Failed to allocate a 1036 byte allocation with 16777216 free bytes and 48MB until OOM; failed due to fragmentation (required continguous free 16384 bytes for a new buffer where largest contiguous free 8192 bytes)",
"\tat org.spongycastle.util.Arrays.clone(Arrays.java:602)",
"\tat org.spongycastle.crypto.generators.SCrypt.SMix(SCrypt.java:126)",
"\tat org.spongycastle.crypto.generators.SCrypt.MFcrypt(SCrypt.java:87)",
"\tat org.spongycastle.crypto.generators.SCrypt.generate(SCrypt.java:66)",
"\tat org.web3j.crypto.Wallet.generateDerivedScryptKey(Wallet.java:136)",
"\tat org.web3j.crypto.Wallet.create(Wallet.java:74)",
"\tat org.web3j.crypto.Wallet.createStandard(Wallet.java:93)",
"\tat org.web3j.crypto.WalletUtils.generateWalletFile(WalletUtils.java:61)"

generateFullNewWalletFile里面會調用createStandard創(chuàng)建錢包，使用N_STANDARD，P_STANDARD來配置加密強度，直接影響需使用的內存大小，最終導致OOM的發(fā)生。

public static WalletFile createStandard(String password, ECKeyPair ecKeyPair)
    throws CipherException {
  return create(password, ecKeyPair, N_STANDARD, P_STANDARD);
}

解決方法非常簡單，創(chuàng)建一個Light Wallet即可：

public void onCreateLightWallet(View view) {
  String filePath = Environment.getExternalStorageDirectory().getAbsolutePath() + "/light";
  File file = new File(filePath);
  file.mkdirs();
  try {
    WalletUtils.generateLightNewWalletFile("a12345678", file);
  } catch (NoSuchAlgorithmException e) {
    e.printStackTrace();
  } catch (NoSuchProviderException e) {
    e.printStackTrace();
  } catch (InvalidAlgorithmParameterException e) {
    e.printStackTrace();
  } catch (CipherException e) {
    e.printStackTrace();
  } catch (IOException e) {
    e.printStackTrace();
  }
}

generateLightNewWalletFile會調用createLight來創(chuàng)建一個輕錢包，使用N_LIGHT，P_LIGHT，他們在數(shù)值上相對較小，所以不會OOM。

public static WalletFile createLight(String password, ECKeyPair ecKeyPair)
    throws CipherException {
  return create(password, ecKeyPair, N_LIGHT, P_LIGHT);
}

我們可以對比一下N_STANDARD和P_STANDARD， N_LIGHT和P_LIGHT的大?。?/p>

private static final int N_LIGHT = 1 << 12;
private static final int P_LIGHT = 6;

private static final int N_STANDARD = 1 << 18;
private static final int P_STANDARD = 1;

導入錢包OOM解決

當我們導入一個輕錢包時，不會產(chǎn)生OOM，但導入不是一個輕錢包時，則有可能產(chǎn)生OOM。例如，我們使用Imtoken創(chuàng)建一個錢包并導出Keystore，Keystore如下：

{"address":"9a2e2419f3af050d4730f80e7a65b9f8deb5e16f","crypto":{"cipher":"aes-128-ctr","cipherparams":{"iv":"eaccea79c27a91e307f24988186ef21a"},"ciphertext":"a163e532edf2d76beaee5c26fd2c2fab071a9cb37627aa185ac89e223e41ab97","kdf":"scrypt","kdfparams":{"dklen":32,"n":65536,"p":1,"r":8,"salt":"6a847392a029553f4152dea7bb0b6fb0ac9eec29f55e572fe94603182f5ed7f1"},"mac":"3fad2a31e18c611b10df84db9ae368ce2e189b5c35e9f111e40ca4b4bfb02491"},"id":"032c47c2-c7b7-46f8-a3f7-f526580f6f09","version":3}

可以看到，其中n為65536，p為1，而輕錢包的n為1<<12,即2的12次方，4096，所以這不是一個輕錢包。

我們將該Keystore作為一個json文件push到SD卡中，然后使用Web3j進行導入：

public void onImportWallet(View view) {
  try {
    //需提前將assets目錄下的keystore.json文件推送到手機SD里面
    String filePath = Environment.getExternalStorageDirectory().getAbsolutePath() + "/keystore.json";
    File file = new File(filePath);
    WalletUtils.loadCredentials("a12345678", file);
  } catch (IOException e) {
    e.printStackTrace();
  } catch (CipherException e) {
    e.printStackTrace();
  }
}

發(fā)現(xiàn)同樣會OOM：

Caused by: java.lang.OutOfMemoryError: Failed to allocate a 1036 byte allocation with 13588800 free bytes and 12MB until OOM; failed due to fragmentation (required continguous free 16384 bytes for a new buffer where largest contiguous free 12288 bytes)
    at org.spongycastle.util.Arrays.clone(Arrays.java:602)
    at org.spongycastle.crypto.generators.SCrypt.SMix(SCrypt.java:126)
    at org.spongycastle.crypto.generators.SCrypt.MFcrypt(SCrypt.java:87)
    at org.spongycastle.crypto.generators.SCrypt.generate(SCrypt.java:66)
    at org.web3j.crypto.Wallet.generateDerivedScryptKey(Wallet.java:136)
    at org.web3j.crypto.Wallet.decrypt(Wallet.java:214)
    at org.web3j.crypto.WalletUtils.loadCredentials(WalletUtils.java:112)

通過log可以看出來，這里和創(chuàng)建錢包的OOM是一樣的，都是最后調用generateDerivedScryptKey后導致:

private static byte[] generateDerivedScryptKey(
    byte[] password, byte[] salt, int n, int r, int p, int dkLen) throws CipherException {
  return SCrypt.generate(password, salt, n, r, p, dkLen);
}

創(chuàng)建錢包可以創(chuàng)建一個輕錢包，導入錢包總不能讓用戶換一個輕錢包來導入吧。這里，我們只能還是換回lambda庫來完成keystore的編解碼, 即我們可以自己寫一個generateDerivedScryptKey方法，將spongycastle的SCrypt換成lambda的SCrypt。我們使用MyWalletUtils和MyWallet共同完成該任務。

public void onImportWallet(View view) {
  try {
    //需提前將assets目錄下的keystore.json文件推送到手機SD里面
    String filePath = Environment.getExternalStorageDirectory().getAbsolutePath() + "/keystore.json";
    File file = new File(filePath);
    Credentials credentials = MyWalletUtils.loadCredentials("a12345678", file);
    Log.d(TAG, "address:" + credentials.getAddress());
  } catch (IOException e) {
    e.printStackTrace();
  } catch (CipherException e) {
    e.printStackTrace();
  }
}

public class MyWalletUtils {
  public static Credentials loadCredentials(String password, File source)
      throws IOException, CipherException {
    WalletFile walletFile = objectMapper.readValue(source, WalletFile.class);
    return Credentials.create(MyWallet.decrypt(password, walletFile));
  }
}

public class MyWallet {

  private static final int CURRENT_VERSION = 3;
  private static final String CIPHER = "aes-128-ctr";
  static final String AES_128_CTR = "pbkdf2";
  static final String SCRYPT = "scrypt";

  private static byte[] generateDerivedScryptKey(
      byte[] password, byte[] salt, int n, int r, int p, int dkLen) {
    try {
      return SCrypt.scrypt(password, salt, n, r, p, dkLen);
    } catch (GeneralSecurityException e) {
      e.printStackTrace();
    }
    return null;
  }
}

按照以上方法處理之后，就可以解決OOM，但是用戶等待的時間會稍微長一點，另外，最好還是添加一下Android平臺的libscrpt.so庫，大家可在本項目的jniLibs中找到。

以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持腳本之家。

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