将打包值打包为位片段
内存性能通常将多个值压缩为单个原始值。这可能有助于将各种信息传递到单个变量中。
例如,可以将 3 个字节(例如 RGB 中的颜色代码)打包到单个 int 中。
打包值
// Raw bytes as input
byte[] b = {(byte)0x65, (byte)0xFF, (byte)0x31};
// Packed in big endian: x == 0x65FF31
int x = (b[0] & 0xFF) << 16 // Red
| (b[1] & 0xFF) << 8 // Green
| (b[2] & 0xFF) << 0; // Blue
// Packed in little endian: y == 0x31FF65
int y = (b[0] & 0xFF) << 0
| (b[1] & 0xFF) << 8
| (b[2] & 0xFF) << 16;
解包值
// Raw int32 as input
int x = 0x31FF65;
// Unpacked in big endian: {0x65, 0xFF, 0x31}
byte[] c = {
(byte)(x >> 16),
(byte)(x >> 8),
(byte)(x & 0xFF)
};
// Unpacked in little endian: {0x31, 0xFF, 0x65}
byte[] d = {
(byte)(x & 0xFF),
(byte)(x >> 8),
(byte)(x >> 16)
};