在 TOIT 中压缩数据

Question

TOIT库包含zip.toit模块，希望系统支持数据压缩和解压。不幸的是，没有例子。能否给出最简单的数据压缩解压的例子，比如字符串或者二进制数组？

Answer 1

zlib 库目前仅支持压缩。

基本上你必须：

创建压缩器（zlib 或 gzip）。
在一个任务中提供数据
read/use另一个任务中的压缩数据。

这是一个例子：

import zlib
import bytes
import monitor

main:
  // We use a semaphore to let the main task know when all the
  // compressed data has been handled.
  // If the data is just sent over the network, then the semaphore
  // wouldn't be necessary. The second task (`t`) would just finish
  // once all data has been processed.
  done := monitor.Semaphore

  // We use a byte-buffer to accumulate all the data. If the data is
  // to be sent somewhere, then it's better to just do that directly,
  // instead of using memory here.
  accumulator := bytes.Buffer

  // There are other encoders as well, but the gzip-encoder has
  // the advantage that it produces `.gz` compatible data.
  compressor := zlib.RunLengthGzipEncoder

  // We create a second task that takes out the already compressed
  // data of the compressor.
  t := task::
    while data := compressor.read:
      accumulator.write data
    // We increment the semaphore, so that the other (original) task
    // knows that we are done processing the data.
    done.up

  // In this task we now add data. As example, it's just "foo", but any
  // string or byte-array would work.
  // Can be called multiple times.
  compressor.write "foo"

  // The compressor must be closed.
  // This flushes the last remaining data, and lets the reading
  // task know that it is done.
  compressor.close

  // We wait for the reading task to signal that all data is handled.
  done.down

  // Show the data that was accumulated.
  // You would normally just send it somewhere, and not print it.
  print accumulator.buffer.size
  print accumulator.buffer

Answer 2

小NB。您还可以在 android 中解码生成的二进制数组。我通过编写一个小的 java 应用程序来测试这个：

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

public class MainActivity extends AppCompatActivity {
//  byte array from toit:
    byte[] bytes = { 31, -117, 8, 0, 0, 0, 0, 0, 0, -1, 75, -53, -49, 7, 0, 33, 101, 115, -116, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

    static final String TAG = "GZip";
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        String foo = null;
        try {
            foo = decompress(bytes);
        }
        catch(IOException exception) {
            Log.d(TAG, exception.toString());
        }
        Log.d(TAG, "decompress->[" + foo + "]");
    }

    public static String decompress(byte[] compressed) throws IOException {
        final int BUFFER_SIZE = 32;
        ByteArrayInputStream is = new ByteArrayInputStream(compressed);
        GZIPInputStream gis = new GZIPInputStream(is, BUFFER_SIZE);
        StringBuilder string = new StringBuilder();
        byte[] data = new byte[BUFFER_SIZE];
        int bytesRead;
        while ((bytesRead = gis.read(data)) != -1) {
            string.append(new String(data, 0, bytesRead));
        }
        gis.close();
        is.close();
        return string.toString();
    }

在 TOIT 中压缩数据

Compressing data in TOIT

zip

compression

toit