[英]java GZIPInputStream and GZIPOutputStream not working as expected
我試圖將一系列Long
寫入GZIPOutputStream
,以期稍后解壓縮數字。
當我嘗試使用少量Long
時,以下程序可以正常工作,但是它將拋出許多Long
的異常,例如(10240)。
請查看並運行以下代碼:
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.nio.ByteBuffer;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;
public class GzipTest {
private static final String filename = "data.gz";
public static void main(String... args) throws Exception {
test(32); // OK
test(10240); // Why won't this work? (unexpected read: 6)
}
public static void test(int max) throws Exception {
System.out.println("testing with " + max);
FileOutputStream fos = new FileOutputStream(filename);
GZIPOutputStream gos = new GZIPOutputStream(fos, 4096);
long num = 10241000L;
for (int i = 0; i < max; ++i) {
gos.write(long2bytes(num + i));
}
gos.close();
fos.close();
GZIPInputStream gis = new GZIPInputStream(new FileInputStream(filename), 4096);
byte[] buf = new byte[Long.BYTES];
for (int i = 0; i < max; ++i) {
int nread = gis.read(buf);
if (nread != Long.BYTES) {
throw new RuntimeException("unexpected read: " + nread);
}
long value = bytes2long(buf);
if (value != num + i) {
throw new RuntimeException("unexpected value: " + value);
}
}
gis.close();
}
static byte[] long2bytes(long num) {
ByteBuffer buf = ByteBuffer.allocate(Long.BYTES);
buf.putLong(num);
return buf.array();
}
static long bytes2long(byte[] bytes) {
return ByteBuffer.wrap(bytes).getLong();
}
}
輸出:
testing with 32
testing with 10240
Exception in thread "main" java.lang.RuntimeException: unexpected read: 6
at GzipTest.test(GzipTest.java:31)
at GzipTest.main(GzipTest.java:12)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
如果您進行了彼得·勞瑞(Peter Lawrey)提出的更改,則代碼可以正常工作:
try (DataInputStream in = new DataInputStream(new GZIPInputStream(new FileInputStream(filename), 4096))) {
byte[] buf = new byte[Long.BYTES];
for (int i = 0; i < max; ++i) {
in.readFully(buf);
long value = bytes2long(buf);
if (value != num + i) {
throw new RuntimeException("unexpected value: " + value);
}
}
}
或者,您可以將所有內容簡化為:
try (DataInputStream in = new DataInputStream(new GZIPInputStream(new FileInputStream(filename), 4096))) {
for (int i = 0; i < max; ++i) {
long value = in.readLong();
if (value != num + i) {
throw new RuntimeException("unexpected value: " + value);
}
}
}
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.