从一个C/C++语言生成的二进制文件中读出一个float数据
// 参见java.io.DataInputStream
// C++写入的字节顺序是从低到高（左低到右高），
而java.io.DataInputStream读取的数据是从高到低（左高到右低)
// 所以需要自己改写一下
// 功能和java.io.DataInputStream类似的
public class CppInputStream extends FilterInputStream {
public CppInputStream(InputStream in) {
super(in);
}
public final int read(byte b[]) throws IOException {
return in.read(b, 0, b.length);
}
public final int read(byte b[], int off, int len) throws IOException {
return in.read(b, off, len);
}
public final void readFully(byte b[]) throws IOException {
readFully(b, 0, b.length);
}
public final void readFully(byte b[], int off, int len) throws IOException {
if (len < 0)
throw new IndexOutOfBoundsException();
int n = 0;
while (n < len) {
int count = in.read(b, off + n, len - n);
if (count < 0)
throw new EOFException();
n += count;
}
}
public final int skipBytes(int n) throws IOException {
int total = 0;
int cur = 0;
while ((total < n) && ((cur = (int) in.skip(n - total)) > 0)) {
total += cur;
}
return total;
}
public final byte readByte() throws IOException {
int ch = in.read();
if (ch < 0)
throw new EOFException();
return (byte) (ch);
}
public final int readUnsignedByte() throws IOException {
int ch = in.read();
if (ch < 0)
throw new EOFException();
return ch;
}
public final short readShort() throws IOException {
int ch2 = in.read();
int ch1 = in.read();
if ((ch1 | ch2) < 0)
throw new EOFException();
return (short) ((ch1 << 8) + (ch2 << 0));
}
public final int readUnsignedShort() throws IOException {
int ch2 = in.read();
int ch1 = in.read();
if ((ch1 | ch2) < 0)
throw new EOFException();
return (ch1 << 8) + (ch2 << 0);
}
public final char readChar() throws IOException {
int ch2 = in.read();
int ch1 = in.read();
if ((ch1 | ch2) < 0)
throw new EOFException();
return (char) ((ch1 << 8) + (ch2 << 0));
}
public final int readInt() throws IOException {
int ch4 = in.read();
int ch3 = in.read();
int ch2 = in.read();
int ch1 = in.read();
if ((ch1 | ch2 | ch3 | ch4) < 0)
throw new EOFException();
return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
}
private byte readBuffer[] = new byte[8];
public final long readLong() throws IOException {
readFully(readBuffer, 0, 8);
return (((long) readBuffer[7] << 56) + ((long) (readBuffer[6] & 255) << 48)
+ ((long) (readBuffer[5] & 255) << 40) + ((long) (readBuffer[4] & 255) << 32)
+ ((long) (readBuffer[3] & 255) << 24) + ((readBuffer[2] & 255) << 16)
+ ((readBuffer[1] & 255) << 8) + ((readBuffer[0] & 255) << 0));
}
public final float readFloat() throws IOException {
return Float.intBitsToFloat(readInt());
}
public final double readDouble() throws IOException {
return Double.longBitsToDouble(readLong());
}
}
也可以先用Java读取一个Int进来，然后处理
// Java读取后，顺序已经反了
int javaReadInt = ;
// 将每个字节取出来
byte byte4 = (byte) (javaReadInt & 0xff);
byte byte3 = (byte) ((javaReadInt & 0xff00) >> 8);
byte byte2 = (byte) ((javaReadInt & 0xff0000) >> 16);
byte byte1 = (byte) ((javaReadInt & 0xff000000) >> 24);
// 拼装成 正确的int
int realint = (byte1& 0xff)<<0 + (byte2& 0xff)<<8 + (byte3& 0xff)<< 16 +(byte4& 0xff)<<24 ;
另外可以使用ByteBuffer来完成,而不需要自己考虑,如何将字节数组转换为其他数据类型. 使用ByteBuffer,可以设置字节顺序.
ByteBuffer简单的例子
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
public class ByteBufferTest {
public static void main(String[] args) {
//将字节数组转换为int类型
byte[] bytes = {0,0,0,1};
ByteBuffer buffer = ByteBuffer.wrap(bytes);
System.out.println(buffer.getInt());
ByteBuffer buffer2 = ByteBuffer.wrap(bytes);
buffer2.order(ByteOrder.LITTLE_ENDIAN);
System.out.println(buffer2.getInt());
}
}
