使用java中的字節數組填充數據流中的數據

Question

我想從字節數組中提取特定位和字節。該字節數組使用文件輸入流填充，並且在特定長度的流中包含連續的重複數據分組格式，例如，首部的時間戳的數據類型 - 數據CRC。我需要填充數據包的列表，並能夠從中提取數據。

Packet() 
{ 
    byte header; // 1 BYTE: split into bit flags, and extracted using masks 
    int timestamp; // 4 BYTES 
    int dataType; // 1 BYTE 
    string data; // 10 BYTES 
    int crc; // 1 BYTE 
} 

static final int PACKET_SIZE 17 // BYTES 
Packet[] packets; 
byte[] input = new byte[(int)file.length()]; 
InputStream is = new BufferedInputStream(new FileInputStream(file)); 
int totalBytesRead = 0; 
int totalPacketsRead = 0; 
while(totalBytesRead < input.length) 
{ 
    int bytesRemaining = input.length - totalBytesRead;   
    int bytesRead = input.read(result, totalBytesRead, PACKET_SIZE); 
    totalBytesRead = totalBytesRead + bytesRead; 

    packet aPacket; 
    // How to populate a single packet in each iteration ??? 
    ... 
    packets[totalPacketsRead] = aPacket; 
    totalPacketsRead++; 
} 

Answer 1

你可以使用ByteBuffer：

ByteBuffer buffer = ByteBuffer.wrap(packetBuffer); 

Packet packet = new Packet(); 
packet.header = buffer.get(); 
packet.timestamp = buffer.getInt(); 
... 

或者如果你喜歡：生成從單字節這樣的整數：

public int readInt(byte[] b , int at) 
{ 
    int result = 0; 

    for(int i = 0 ; i < 4 ; i++) 
     result |= ((int) b[at + i]) << ((3 - i) * 8); 

    return result; 
}