java - 将 uintN 数据类型从 C 传输到 Java(套接字编程)

Question

我有一个要求，通过套接字，即winsock接口(interface)，从用C编写的 native 程序发送数据。然后该数据由 Java 程序接收。 Java 程序接收一个它知道顺序的数据包并进行一些处理。它采用从 socket.Read() 接收的 int，如 client_socket.getInputStream().read()

解析从 Read() 返回的 int 数据的处理以获得预期的数据类型。基本上它是接收到的大量数据的切片。我只能假设 read() 函数一次读取 4 个字节(32 位 java int 大小)。所以我继续将这 4 个字节(8 位不是 Java 类型)分成 4 个 Java 短裤，这样我就可以正确地表示它们所代表的无符号值。 在我有 4 条短裤之后，如果我知道我想要一个 uint16，我只需连接 2 条短裤

问题是我在某个地方做了一些错误的位操作，结果没有像我想象的那样工作。 下面是 C 代码和 Java 代码，虽然它不起作用，但它非常简单。输出是我无法理解的原因。

0 0   0 0    0 1     0 0     0 2     0 0     0 3     0 0     0 4 {...}

C 代码编辑了初始化部分:

uint16_t buffer[255] = {};
uint16_t *current_pointer = buffer;
for(uint16_t index = 0; index < 255; index++) {
    *current_pointer = index;
    current_pointer++;
}
Write(client_socket, (char *)buffer, sizeof(buffer));

Java 代码也经过编辑:

public final short[] JavaIntToUint8Array(int unsigned_int) {
    return new short[] { (short)((unsigned_int & 0xFF000000L) >> 24),
                (short)((unsigned_int & 0x00FF0000L) >> 16),
                (short)((unsigned_int & 0x0000FF00L) >> 8),
                (short)((unsigned_int & 0x000000FFL))};
}
public final int[] JavaIntToUint16(int unsigned_int) {
    short uint8_array[] = JavaIntToUint8Array(unsigned_int);
    return new int[] { (int)(uint8_array[0] << 8) | (int)uint8_array[1],            
        (int)(uint8_array[2] << 8) | (int)(uint8_array[3]) };
}

...

while (index < 255) {
        read_data = data_input.read();
        System.out.print(" ");
        System.out.print(JavaIntToUint16(read_data)[0]);
        System.out.print(" ");
        System.out.print(JavaIntToUint16(read_data)[1]);
        System.out.print("\t");
        index++;

}

Answer 1

I can only assume that the read() functions reads 4 bytes at a time (the 32 bit java int size)

不，你不能这样假设。 documentation for InputStream.read()说:

public abstract int read() throws IOException

Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

A subclass must provide an implementation of this method.

Returns:
    the next byte of data, or -1 if the end of the stream is reached.