com.google.common.io.ByteSource#copyTo ( )源码实例Demo

private static void addFile(JarOutputStream jarFile, JavaFile javaFile) throws IOException {
  initNextEntry(javaFile.getFilePath(), jarFile);
  ByteSource byteSource =
      CharSource.wrap(javaFile.getFileContent()).asByteSource(StandardCharsets.UTF_8);
  byteSource.copyTo(jarFile);
}
 

private void copyResource(final ByteSource source, final File target) throws IOException {
    try (final OutputStream out = createFile(target)) {
        source.copyTo(out);
    }
}
 

@VisibleForTesting
static byte[] createMetadataHeader(
    ImmutableSet<RuleKey> ruleKeys, ImmutableMap<String, String> metadata, ByteSource data)
    throws IOException {

  ByteArrayOutputStream rawOut = new ByteArrayOutputStream();
  Hasher hasher = HASH_FUNCTION.newHasher();
  try (DataOutputStream out = new DataOutputStream(new HasherOutputStream(hasher, rawOut))) {

    // Write the rule keys to the raw metadata, including them in the end-to-end checksum.
    out.writeInt(ruleKeys.size());
    for (RuleKey ruleKey : ruleKeys) {
      out.writeUTF(ruleKey.toString());
    }

    // Write out the metadata map to the raw metadata, including it in the end-to-end checksum.
    out.writeInt(metadata.size());
    for (Map.Entry<String, String> ent : metadata.entrySet()) {
      out.writeUTF(ent.getKey());
      byte[] val = ent.getValue().getBytes(Charsets.UTF_8);
      out.writeInt(val.length);
      out.write(val);
      if (out.size() > MAX_METADATA_HEADER_SIZE) {
        throw new IOException("Metadata header too big.");
      }
    }
  }

  // Add the file data contents to the end-to-end checksum.
  data.copyTo(new HasherOutputStream(hasher, ByteStreams.nullOutputStream()));

  // Finish the checksum, adding it to the raw metadata
  rawOut.write(hasher.hash().asBytes());

  // Finally, base64 encode the raw bytes to make usable in a HTTP header.
  byte[] bytes = rawOut.toByteArray();
  if (bytes.length > MAX_METADATA_HEADER_SIZE) {
    throw new IOException("Metadata header too big.");
  }
  return bytes;
}