我正在尝试使用java代码在android设备中写入和读取 float 组(实际上相当大,640*480)。 像this one
DataOutputStream out = ...;
for (int i=0; i<floatarray.length; ++i)
out.writeFloat(floatarray[i]);
非常慢,我已经尝试过了。
写:
float[] test=new float[3];
test[0]=1.0f;
test[1]=1.2f;
test[2]=1.5f;
//long timeBeforeWrite = System.nanoTime();
try {
BufferedOutputStream dataOut = new BufferedOutputStream (
new FileOutputStream("/sdcard/DCIM/Camera/Dual/demo.bin"));
byte buf[]=new byte[4*test.length];
long timeBeforeWrite = System.nanoTime();
for (int i=0; i<test.length; ++i)
{
int val = Float.floatToRawIntBits(test[i]);
buf[4 * i] = (byte) (val >> 24);
buf[4 * i + 1] = (byte) (val >> 16) ;
buf[4 * i + 2] = (byte) (val >> 8);
buf[4 * i + 3] = (byte) (val);
}
dataOut.write(buf);
long ct_write = System.nanoTime();
long offset_write = ct_write - timeBeforeWrite;
float mOffsetInMs_write = (float)(offset_write)/1000000;
Log.e("ETA", "write float[] " + Float.toString(mOffsetInMs_write));
dataOut.flush();
dataOut.close();
} catch (IOException ex) {
System.err.println(ex.getMessage());
}
阅读:
float[] read=new float[3];
try{
BufferedInputStream dataIn=new BufferedInputStream (new FileInputStream("/sdcard/DCIM/Camera/Dual/demo.txt"));
byte buf[]=new byte[4*read.length];
long timeBeforeWrite = System.nanoTime();
dataIn.read(buf);
for (int i=0; i<read.length; ++i)
{
int val;
val = buf[4 * i] << 24;
val += buf[4 * i + 1] << 16;
val += buf[4 * i + 2] << 8;
val += buf[4 * i + 3];
read[i]=Float.valueOf(Integer.toBinaryString(val));
//int val = Float.floatToRawIntBits(disparityMap[i]);
}
long ct_write = System.nanoTime();
long offset_write = ct_write - timeBeforeWrite;
float mOffsetInMs_write = (float)(offset_write)/1000000;
Log.e("ETA", "read float[] " + Float.toString(mOffsetInMs_write));
dataIn.close();
}catch (IOException ex) {
System.err.println(ex.getMessage());
}
读回的东西是非常奇怪的浮点值,这有什么问题?顺便说一句,读回运行得很慢,不知道为什么。 或者还有其他快速读/写 float 组的好主意吗?
谢谢!
//感谢 Larry,我尝试了 bytebuffer.asfloatbuffer() 方法,例如:
//WRITE
float[] test = new float[3];
test[0]=1.1f;
test[1]=1.2f;
test[2]=1.5f;
try{
RandomAccessFile aFile = new RandomAccessFile("/sdcard/demo.data", "rw");
FileChannel outChannel = aFile.getChannel();
//one float 3 bytes
ByteBuffer buf = ByteBuffer.allocate(12);
buf.clear();
buf.asFloatBuffer().put(test);
//while(buf.hasRemaining())
{
outChannel.write(buf);
}
outChannel.close();
}
catch (IOException ex) {
System.err.println(ex.getMessage());
}
//READ
float[] readback=new float[3];
try{
RandomAccessFile rFile = new RandomAccessFile("/sdcard/demo.data", "rw");
FileChannel inChannel = rFile.getChannel();
ByteBuffer buf_in = ByteBuffer.allocate(12);
buf_in.clear();
inChannel.read(buf_in);
buf_in.asFloatBuffer().get(readback);
inChannel.close();
}
catch (IOException ex) {
System.err.println(ex.getMessage());
}
并且程序在buf_in.asFloatBuffer().get(readback);
中崩溃
有什么想法吗?有没有好的方法可以在java中进行内部调试,抱歉,在java世界中是全新的。再次感谢
最佳答案
感谢 Larry,我只是分享我的代码,希望对其他人有帮助。
我刚刚弄清楚,我们需要在读/写文件 channel 后倒回缓冲区。以下代码可以正常工作,并且运行速度相当快。
float[] disparity=new float[640*480];
disparity[1]=1.5f;
disparity[2]=4.566f;
//WRITE
try{
RandomAccessFile aFile = new RandomAccessFile("/sdcard/demo.data", "rw");
FileChannel outChannel = aFile.getChannel();
//one float 4 bytes
ByteBuffer buf = ByteBuffer.allocate(4*640*480);
buf.clear();
buf.asFloatBuffer().put(disparity);
//while(buf.hasRemaining())
{
outChannel.write(buf);
}
//outChannel.close();
buf.rewind();
float[] out=new float[3];
buf.asFloatBuffer().get(out);
outChannel.close();
}
catch (IOException ex) {
System.err.println(ex.getMessage());
}
//READ
float[] readback=new float[640*480];
try{
RandomAccessFile rFile = new RandomAccessFile("/sdcard/demo.data", "rw");
FileChannel inChannel = rFile.getChannel();
ByteBuffer buf_in = ByteBuffer.allocate(640*480*4);
buf_in.clear();
inChannel.read(buf_in);
buf_in.rewind();
buf_in.asFloatBuffer().get(readback);
inChannel.close();
}
catch (IOException ex) {
System.err.println(ex.getMessage());
}
再次感谢。
关于java - 以java快速方式写入/读取 float 组,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22249483/