blocks|key|12143|text|是否有类似于ZipEntry.getSize()的GZIPInputStream方法|type|blockquote|depth|inlineStyleRanges|entityRanges|data|12144|不是的。它不在Javadoc+=>中，它不存在。|unstyled|offset|length|12145|你要长度做什么？|12146|entityMap|0|LINK|mutability|MUTABLE|url|http://download.oracle.com/javase/6/docs/api/java/util/zip/GZIPInputStream.html^0|0|7|7|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@$E|S|F|T|1|U]]|A|$]]|$1|G|3|H|5|D|7|V|8|@]|9|@]|A|$]]|$1|I|3|-4|5|D|7|W|8|@]|9|@]|A|$]]]|J|$K|$5|L|M|N|A|$O|P]]]]

<blockquote>
 Is there a similiar method like ZipEntry.getSize() for
 GZIPInputStream
</blockquote>

No. It's not in the <a href="http://download.oracle.com/javase/6/docs/api/java/util/zip/GZIPInputStream.html" rel="nofollow">Javadoc</a> => it doesn't exist.

What do you need the length for?

blocks|key|1874147|text|可以通过读取gzipped文件的最后四个字节来确定未压缩大小。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1874148|我在这里找到了这个解决方案：|1874149|http://www.abeel.be/content/determine-uncompressed-size-gzip-file|offset|length|1874150|另外，在这个链接中还有一些示例代码(更正为使用long而不是int，以处理2GB到4GB之间的大小，这将使int包装起来)：|style|CODE|1874151|RandomAccessFile+raf+=+new+RandomAccessFile(file,+"r");
raf.seek(raf.length()+-+4);
byte+b4+=+raf.read();
byte+b3+=+raf.read();
byte+b2+=+raf.read();
byte+b1+=+raf.read();
long+val+=+((long)b1+<<+24)+%7C+((long)b2+<<+16)+%7C+((long)b3+<<+8)+%7C+(long)b4;
raf.close();|code-block|syntax|javascript|1874152|val是以字节为单位的长度。注意:当未压缩文件大于4GB时，无法确定正确的未压缩大小！|1874153|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|1T|0|0|N|4|U|3|1H|3|0|0|0|3|0^^$0|@$1|2|3|4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|10|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|11|8|@]|9|@$F|12|G|13|1|14]]|A|$]]|$1|H|3|I|5|6|7|15|8|@$F|16|G|17|J|K]|$F|18|G|19|J|K]|$F|1A|G|1B|J|K]]|9|@]|A|$]]|$1|L|3|M|5|N|7|1C|8|@]|9|@]|A|$O|P]]|$1|Q|3|R|5|6|7|1D|8|@$F|1E|G|1F|J|K]]|9|@]|A|$]]|$1|S|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|E]]]]

It is possible to determine the uncompressed size by reading the last four bytes of the gzipped file.

I found this solution here:

<a href="http://www.abeel.be/content/determine-uncompressed-size-gzip-file" rel="noreferrer">http://www.abeel.be/content/determine-uncompressed-size-gzip-file</a>

Also from this link there is some example code (corrected to use <code>long</code> instead of <code>int</code>, to cope with sizes between 2GB and 4GB which would make an <code>int</code> wrap around):

<pre><code>RandomAccessFile raf = new RandomAccessFile(file, "r");
raf.seek(raf.length() - 4);
byte b4 = raf.read();
byte b3 = raf.read();
byte b2 = raf.read();
byte b1 = raf.read();
long val = ((long)b1 &lt;&lt; 24) | ((long)b2 &lt;&lt; 16) | ((long)b3 &lt;&lt; 8) | (long)b4;
raf.close();
</code></pre>

<code>val</code> is the length in bytes. Beware: you can not determine the correct uncompressed size, when the uncompressed file was greater than 4GB!

blocks|key|1874155|text|基于@Alexander的回答：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1874156|RandomAccessFile+raf+=+new+RandomAccessFile(inputFilePath+%2B+".gz",+"r");
raf.seek(raf.length()+-+4);
byte[]+bytes+=+new+byte[4];
raf.read(bytes);
fileSize+=+ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN).getInt();
if+(fileSize+<+0)
++fileSize+%2B=+(1L+<<+32);
raf.close();|code-block|syntax|javascript|1874157|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Based on @Alexander's answer:


<pre><code>RandomAccessFile raf = new RandomAccessFile(inputFilePath + ".gz", "r");
raf.seek(raf.length() - 4);
byte[] bytes = new byte[4];
raf.read(bytes);
fileSize = ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN).getInt();
if (fileSize &lt; 0)
 fileSize += (1L &lt;&lt; 32);
raf.close();
</code></pre>

blocks|key|12163|text|除了解压整件事外，没有其他可靠的方法来获得长度。见使用zlib的gzip文件访问函数解压缩文件大小。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|12164|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/9209138/uncompressed-file-size-using-zlibs-gzip-file-access-function/9213826#9213826^0|P|O|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

There is no reliable way to get the length other than decompressing the whole thing. See <a href="https://stackoverflow.com/questions/9209138/uncompressed-file-size-using-zlibs-gzip-file-access-function/9213826#9213826">Uncompressed file size using zlib&#39;s gzip file access function</a> .

blocks|key|11723|text|如果您可以猜到压缩比(如果数据与您已经处理过的其他数据相似的话，这是一个合理的期望)，那么您可以计算出任意大文件的大小(有一些错误)。同样，这假设一个文件包含一个gzip流。以下假设的第一个大小大于估计大小的90%25+(根据估计比率)是真实大小：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|11724|estCompRatio+=+6.1;
RandomAccessFile+raf+=+new+RandomAccessFile(inputFilePath+%2B+".gz",+"r");
compLength+=+raf.length();
byte[]+bytes+=+new+byte[4];
raf.read(bytes);
uncLength+=+ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN).getInt();
raf.seek(compLength+-+4);
uncLength+=+raf.readInt();
while(uncLength+<+(compLength+*+estCompRatio+*+0.9)){
++uncLength+%2B=+(1L+<<+32);
}|code-block|syntax|javascript|11725|将estCompRatio设置为0等于@Alexander的回答|11726|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

If you can guess at the compression ratio (a reasonable expectation if the data is similar to other data you've already processed), then you can work out the size of arbitrarily large files (with some error). Again, this assumes a file containing a single gzip stream. The following assumes the first size greater than 90% of the estimated size (based on estimated ratio) is the true size:

<pre><code>estCompRatio = 6.1;
RandomAccessFile raf = new RandomAccessFile(inputFilePath + ".gz", "r");
compLength = raf.length();
byte[] bytes = new byte[4];
raf.read(bytes);
uncLength = ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN).getInt();
raf.seek(compLength - 4);
uncLength = raf.readInt();
while(uncLength &lt; (compLength * estCompRatio * 0.9)){
 uncLength += (1L &lt;&lt; 32);
}
</code></pre>

[setting estCompRatio to 0 is equivalent to @Alexander's answer]

blocks|key|1874244|text|一个基于4个尾字节的更紧凑的计算版本(避免使用字节缓冲区，调用Integer.reverseBytes来反转读取字节的字节顺序)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1874245|private+static+long+getUncompressedSize(Path+inputPath)+throws+IOException
{
++++long+size+=+-1;
++++try+(RandomAccessFile+fp+=+new+RandomAccessFile(inputPath.toFile(),+"r"))+{++++++++
++++++++fp.seek(fp.length()+-+Integer.BYTES);
++++++++int+n+=+fp.readInt();
++++++++size+=+Integer.toUnsignedLong(Integer.reverseBytes(n));
++++}
++++return+size;
}|code-block|syntax|javascript|1874246|entityMap^0|V|K|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

A more compact version of the calculation based on the 4 tail bytes (avoids using a byte buffer, calls <code>Integer.reverseBytes</code> to reverse the byte order of read bytes). 

<pre><code>private static long getUncompressedSize(Path inputPath) throws IOException
{
 long size = -1;
 try (RandomAccessFile fp = new RandomAccessFile(inputPath.toFile(), "r")) { 
 fp.seek(fp.length() - Integer.BYTES);
 int n = fp.readInt();
 size = Integer.toUnsignedLong(Integer.reverseBytes(n));
 }
 return size;
}
</code></pre>

blocks|key|1874259|text|而是从底层的FileChannel获取FileInputStream。它告诉您文件大小和压缩文件的当前位置。示例：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1874260|@Override
public+void+produce(final+DataConsumer+consumer,+final+boolean+skipData)+throws+IOException+{
++++try+(FileInputStream+fis+=+new+FileInputStream(tarFile))+{
++++++++FileChannel+channel+=+fis.getChannel();
++++++++final+Eta<Long>+eta+=+new+Eta<>(channel.size());
++++++++try+(InputStream+is+=+tarFile.getName().toLowerCase().endsWith("gz")
++++++++++++?+new+GZIPInputStream(fis)+:+fis)+{
++++++++++++try+(TarArchiveInputStream+tais+=+(TarArchiveInputStream)+new+ArchiveStreamFactory()
++++++++++++++++.createArchiveInputStream("tar",+new+BufferedInputStream(is)))+{

++++++++++++++++TarArchiveEntry+tae;
++++++++++++++++boolean+done+=+false;
++++++++++++++++while+(!done+&&+(tae+=+tais.getNextTarEntry())+!=+null)+{
++++++++++++++++++++if+(tae.getName().startsWith("docs/")+&&+tae.getName().endsWith(".html"))+{
++++++++++++++++++++++++String+data+=+null;
++++++++++++++++++++++++if+(!skipData)+{
++++++++++++++++++++++++++++data+=+new+String(tais.readNBytes((int)+tae.getSize()),+StandardCharsets.UTF_8);
++++++++++++++++++++++++}
++++++++++++++++++++++++done+=+!consumer.consume(data);
++++++++++++++++++++}

++++++++++++++++++++String+progress+=+eta.toStringPeriodical(channel.position());
++++++++++++++++++++if+(progress+!=+null)+{
++++++++++++++++++++++++System.out.println(progress);
++++++++++++++++++++}
++++++++++++++++}
++++++++++++++++System.out.println("tar+bytes+read:+"+%2B+tais.getBytesRead());
++++++++++++}+catch+(ArchiveException+ex)+{
++++++++++++++++throw+new+IOException(ex);
++++++++++++}
++++++++}
++++}
}|code-block|syntax|javascript|1874261|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Get the FileChannel from the underlying FileInputStream instead. It tells you both file size and current position of the compressed file. Example:

<pre><code>@Override
public void produce(final DataConsumer consumer, final boolean skipData) throws IOException {
 try (FileInputStream fis = new FileInputStream(tarFile)) {
 FileChannel channel = fis.getChannel();
 final Eta&lt;Long&gt; eta = new Eta&lt;&gt;(channel.size());
 try (InputStream is = tarFile.getName().toLowerCase().endsWith("gz")
 ? new GZIPInputStream(fis) : fis) {
 try (TarArchiveInputStream tais = (TarArchiveInputStream) new ArchiveStreamFactory()
 .createArchiveInputStream("tar", new BufferedInputStream(is))) {

 TarArchiveEntry tae;
 boolean done = false;
 while (!done &amp;&amp; (tae = tais.getNextTarEntry()) != null) {
 if (tae.getName().startsWith("docs/") &amp;&amp; tae.getName().endsWith(".html")) {
 String data = null;
 if (!skipData) {
 data = new String(tais.readNBytes((int) tae.getSize()), StandardCharsets.UTF_8);
 }
 done = !consumer.consume(data);
 }

 String progress = eta.toStringPeriodical(channel.position());
 if (progress != null) {
 System.out.println(progress);
 }
 }
 System.out.println("tar bytes read: " + tais.getBytesRead());
 } catch (ArchiveException ex) {
 throw new IOException(ex);
 }
 }
 }
}
</code></pre>

blocks|key|46763|text|不，不幸的是，如果您想获得未压缩的大小，您将不得不读取整个流并增加一个计数器，就像您在问题中提到的那样。你为什么要知道尺寸？对尺寸的估计对你的目的有用吗？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|46764|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

No, unfortunately if you wanted to get the uncompressed size, you would have to read the entire stream and increment a counter like you mention in your question. Why do you need to know the size? Could an estimation of the size work for your purposes?

I have a <code>GZIPInputStream</code> that I constructed from another <code>ByteArrayInputStream</code>. I want to know the original (uncompressed) length for the gzip data. Although I can read to the end of the <code>GZIPInputStream</code>, then count the number, it will cost much time and waste CPU. I would like to know the size before read it.

Is there a similiar method like <code>ZipEntry.getSize()</code> for <code>GZIPInputStream</code>:

<blockquote>
 <code>public long getSize ()</code> 
 Since: API Level 1 
 Gets the uncompressed size of this ZipEntry.
</blockquote>

Gets the uncompressed size of this GZIPInputStream?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我有一个GZIPInputStream，我是从另一个ByteArrayInputStream构建的。我想知道gzip数据的原始(未压缩)长度。虽然我可以读到GZIPInputStream的末尾，然后数数数字，但这将花费大量的时间和浪费CPU。我想在读之前知道它的尺寸。是否有类似于ZipEntry.getSize()的GZIPInputStream方法public long getSize ()自:

问获取此GZIPInputStream的未压缩大小？
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问获取此GZIPInputStream的未压缩大小？
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