我从here获得了一个代码将 Int 数组写入文件。但是，我正在尝试对其进行转换，以便它可以将长数组写入文件。但是，它给出了错误(代码如下)。任何人都可以帮助我为什么它会给出错误以及正确的代码应该是什么。谢谢。
import java.io.*;
import java.util.ArrayList;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.util.Random;
import java.util.zip.DataFormatException;
import java.util.zip.Deflater;
import java.util.zip.Inflater;
public class Test {
private static final int bucketSize = 1<<17;//in real world should not be const, but we bored horribly
static final int zipLevel = 2;//feel free to experiement, higher compression (5+)is likely to be total waste
static void writes(long[] a, File file, boolean sync) throws IOException{
byte[] bucket = new byte[Math.min(bucketSize, Math.max(1<<13, Integer.highestOneBit(a.length >>3)))];//128KB bucket
byte[] zipOut = new byte[bucket.length];
final FileOutputStream fout = new FileOutputStream(file);
FileChannel channel = fout.getChannel();
try{
ByteBuffer buf = ByteBuffer.wrap(bucket);
//unfortunately java.util.zip doesn't support Direct Buffer - that would be the perfect fit
ByteBuffer out = ByteBuffer.wrap(zipOut);
out.putLong(a.length);//write length aka header
if (a.length==0){
doWrite(channel, out, 0);
return;
}
Deflater deflater = new Deflater(zipLevel, false);
try{
for (int i=0;i<a.length;){
i = puts(a, buf, i);
buf.flip();
deflater.setInput(bucket, buf.position(), buf.limit());
if (i==a.length)
deflater.finish();
//hacking and using bucket here is tempting since it's copied twice but well
for (int n; (n= deflater.deflate(zipOut, out.position(), out.remaining()))>0;){
doWrite(channel, out, n);
}
buf.clear();
}
}finally{
deflater.end();
}
}finally{
if (sync)
fout.getFD().sync();
channel.close();
}
}
static long[] reads(File file) throws IOException, DataFormatException{
FileChannel channel = new FileInputStream(file).getChannel();
try{
byte[] in = new byte[(int)Math.min(bucketSize, channel.size())];
ByteBuffer buf = ByteBuffer.wrap(in);
channel.read(buf);
buf.flip();
long[] a = new long[(int)buf.getLong()];
if (a.length==0)
return a;
int i=0;
byte[] inflated = new byte[Math.min(1<<17, a.length*4)];
ByteBuffer intBuffer = ByteBuffer.wrap(inflated);
Inflater inflater = new Inflater(false);
try{
do{
if (!buf.hasRemaining()){
buf.clear();
channel.read(buf);
buf.flip();
}
inflater.setInput(in, buf.position(), buf.remaining());
buf.position(buf.position()+buf.remaining());//simulate all read
for (;;){
int n = inflater.inflate(inflated,intBuffer.position(), intBuffer.remaining());
if (n==0)
break;
intBuffer.position(intBuffer.position()+n).flip();
for (;intBuffer.remaining()>3 && i<a.length;i++){//need at least 4 bytes to form an int
a[i] = intBuffer.getInt();
}
intBuffer.compact();
}
}while (channel.position()<channel.size() && i<a.length);
}finally{
inflater.end();
}
// System.out.printf("read ints: %d - channel.position:%d %n", i, channel.position());
return a;
}finally{
channel.close();
}
}
private static void doWrite(FileChannel channel, ByteBuffer out, int n) throws IOException {
out.position(out.position()+n).flip();
while (out.hasRemaining())
channel.write(out);
out.clear();
}
private static int puts(long[] a, ByteBuffer buf, int i) {
for (;buf.hasRemaining() && i<a.length;){
buf.putLong(a[i++]);
}
return i;
}
private static long[] generateRandom(int len){
Random r = new Random(17);
long[] n = new long [len];
for (int i=0;i<len;i++){
n[i]= r.nextBoolean()?0: r.nextInt(1<<23);//limit bounds to have any sensible compression
}
return n;
}
public static void main(String[] args) throws Throwable{
File file = new File("xxx.xxx");
long[] n = generateRandom(3000000); //{0,2,4,1,2,3};
long start = System.nanoTime();
writes(n, file, false);
long elapsed = System.nanoTime() - start;//elapsed will be fairer if the sync is true
System.out.printf("File length: %d, for %d ints, ratio %.2f in %.2fms %n", file.length(), n.length, ((double)file.length())/4/n.length, java.math.BigDecimal.valueOf(elapsed, 6) );
long[] m = reads(file);
//compare, Arrays.equals doesn't return position, so it sucks/kinda
for (int i=0; i<n.length; i++){
if (m[i]!=n[i]){
System.err.printf("Failed at %d%n",i);
break;
}
}
System.out.printf("All done!");
};
}
最佳答案
所以我花了几分钟来实际运行代码，并且对您发布的代码进行了一些调整，但就是这样。
我所做的一件事是 - 不必要的 - 是将 intBuffer 更改为 longBuffer，只是为了清楚起见。这是第一个区别的一部分
75 - byte[] inflated = new byte[Math.min(1<<17, a.length*4)];
76 - ByteBuffer intBuffer = ByteBuffer.wrap(inflated);
76 + byte[] inflated = new byte[Math.min(1<<17, a.length*8)];
77 + ByteBuffer longBuffer = ByteBuffer.wrap(inflated);
在上面的代码片段中，我将膨胀缓冲区的长度更改为 a.length*8 以反射(reflect)它是一个 long 数组而不是 int 数组。
89 - int n = inflater.inflate(inflated,intBuffer.position(), intBuffer.remaining());
90 + int n = inflater.inflate(inflated,longBuffer.position(), longBuffer.remaining());
这只是对变量名称的更改。
92 - intBuffer.position(intBuffer.position()+n).flip();
93 - for (;intBuffer.remaining()>3 && i<a.length;i++){//need at least 4 bytes to form an int
94 - a[i] = intBuffer.getInt();
93 + longBuffer.position(longBuffer.position()+n).flip();
94 + for (;longBuffer.remaining()>7 && i<a.length;i++){//need at least 4 bytes to form an int
95 + a[i] = longBuffer.getLong();
这是一个非常重要的变化。首先更改了名称，但这不是重要的部分。其次，正如 bestsss 指出的那样，remaining() 是 7，而不是 3。最后，a[i] 现在得到的是 long 而不是 int。。这无疑是最大的问题。
96 - intBuffer.compact();
97 + longBuffer.compact();
这里只是重命名。
142 - System.out.printf("File length: %d, for %d ints, ratio %.2f in %.2fms %n", file.length(), n.length, ((double)file.length())/4/n.length, java.math.BigDecimal.valueOf(elapsed, 6) );
143 + System.out.printf("File length: %d, for %d ints, ratio %.2f in %.2fms %n", file.length(), n.length, ((double)file.length())/8/n.length, java.math.BigDecimal.valueOf(elapsed, 6) );
这只是通过文件输出来了解压缩情况，它现在计算文件的结果数量。length/8 而不是超过 4。
这些是我必须进行的唯一必要的编辑才能使其正常工作。基本上只是在所有地方从 int 转移到 long。
完整的代码位于粘贴箱中，以防您弄乱差异符号或其他内容:http://pastebin.com/emY14Ji4
注意:我的副本 (+) 中的行号比您的副本 (-) 高 1，因为我没有删除调试语句...哎呀...
关于将长数组写入文件的Java代码，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/11368343/