java - 使用 GZIPOutputStream 时的当前文件大小

Question

我正在使用 GZIPOutputStream 以异步方式将压缩数据写入磁盘

我想知道已经写入的数据大小，以便在达到限制后关闭文件

ByteBuffer src;
//..
//data added to src here
//..
File theFile = new File("hello.gz");
FileOutputStream fos = new FileOutputStream(theFile);
GZIPOutputStream zs = new GZIPOutputStream(fos);
BufferedWriter zipwriter = new BufferedWriter(new OutputStreamWriter(zs, "UTF-8"));

(while_more_data)
{
   zipwriter.write(src.get());
   // check current file size here and close file if limit is reached
}

Answer 1

将您的 FileOutputStream 包装到另一个能够计算写入字节数的输出流中，例如 CountingOutputStream第三方图书馆提供Jakarta Commons IO , 或 CountingOutputStream来自 Guava .

实现可能是这样的:

ByteBuffer src;
//..
//data added to src here
//..
File theFile = new File("hello.gz");
try (FileOutputStream fos = new FileOutputStream(theFile);
     CountingOutputStream cos = new CountingOutputStream(fos);
     GZIPOutputStream zs = new GZIPOutputStream(cos);
     BufferedWriter zipwriter = new BufferedWriter(new OutputStreamWriter(zs, "UTF-8"))) {

    (while_more_data) {
        zipwriter.write(src.get());
        zipwriter.flush(); // make sure, data passes cos
        if (cos.getByteCount() >= limit) {
            // limit reached
        }
    }
}