unsigned

c++ uint , unsigned int , int

由 穿精又带淫゛_ 提交于 2020-08-22 07:15:21
问题 Hi I have a program that deals alot with vectors and indexes of the elements of these vectors, and I was wondering: is there a difference between uint and unsigned int which is better to use one of the above types or just use int as I read some people say compiler does handle int values more efficiently, but if I used int I will have to check always for negative idxs which is pain. do you think iterators to be better? is it more efficient than normal indexing vectorx[idx] ? p.s the software

c++ uint , unsigned int , int

由 江枫思渺然 提交于 2020-08-22 07:15:12
问题 Hi I have a program that deals alot with vectors and indexes of the elements of these vectors, and I was wondering: is there a difference between uint and unsigned int which is better to use one of the above types or just use int as I read some people say compiler does handle int values more efficiently, but if I used int I will have to check always for negative idxs which is pain. do you think iterators to be better? is it more efficient than normal indexing vectorx[idx] ? p.s the software

C++ reverse 'for' loop

由 元气小坏坏 提交于 2020-06-27 08:38:42
问题 I have a vector: std::vector<int> vec = {1, 2, 3}; And I want to make a reverse for loop. It works, when I write: for(int i = vec.size() - 1; i >= 0; --i) { std::cout << i << std::endl; // 2, 1, 0 } But I get a very large number (like 18446744073709223794) if I write: for(size_t i = vec.size() - 1; i >= 0; --i) { std::cout << i << std::endl; } But they both work when I write: for(int i = 0; i < vec.size() - 1; ++i) { std::cout << i << std::endl; // 1, 2, 3 } // Or for(size_t i = 0; i < vec

C++ reverse 'for' loop

由 只愿长相守 提交于 2020-06-27 08:38:17
问题 I have a vector: std::vector<int> vec = {1, 2, 3}; And I want to make a reverse for loop. It works, when I write: for(int i = vec.size() - 1; i >= 0; --i) { std::cout << i << std::endl; // 2, 1, 0 } But I get a very large number (like 18446744073709223794) if I write: for(size_t i = vec.size() - 1; i >= 0; --i) { std::cout << i << std::endl; } But they both work when I write: for(int i = 0; i < vec.size() - 1; ++i) { std::cout << i << std::endl; // 1, 2, 3 } // Or for(size_t i = 0; i < vec

Interpret a negative number as unsigned with BigInteger

由 我只是一个虾纸丫 提交于 2020-05-29 07:15:01
问题 Is it possible to parse a negative number into an unsigned value with Java's BigInteger ? So for instance, I'd to interpret -1 as FFFFFFFFFFFFFFFF . 回答1: If you are thinking of a two's complement, you must specify a working bit length. A Java long has 64 bits, but a BigInteger is not bounded. You could do something as this: // Two's complement reference: 2^n . // In this case, 2^64 (so as to emulate a unsigned long) private static final BigInteger TWO_COMPL_REF = BigInteger.ONE.shiftLeft(64);

Interpret a negative number as unsigned with BigInteger

由 ぐ巨炮叔叔 提交于 2020-05-29 07:13:12
问题 Is it possible to parse a negative number into an unsigned value with Java's BigInteger ? So for instance, I'd to interpret -1 as FFFFFFFFFFFFFFFF . 回答1: If you are thinking of a two's complement, you must specify a working bit length. A Java long has 64 bits, but a BigInteger is not bounded. You could do something as this: // Two's complement reference: 2^n . // In this case, 2^64 (so as to emulate a unsigned long) private static final BigInteger TWO_COMPL_REF = BigInteger.ONE.shiftLeft(64);

python解析网络封包方法

由 百般思念 提交于 2020-04-07 08:39:08
在使用Python解析网络数据包时，使用网络字节序解析，参见下表。 C语言的数据类型和Python的数据类型对照表请参见下表。 接下来对封包与解包进行举例说明。 version type id content unsigned short unsigned short unsigned int unsigned int 封包 package = "" # 初始化字符串变量 vertsion = 0x0001 type = 0x0003 id = 0x12345678 content = 0xab12ef45 package += struct.pack('!H', vertsion) package += struct.pack('!H', type) package += struct.pack('!I', id) package += struct.pack('!I', content) 解包 package = receive() # 接收网络数据包 vertsion = 0x0001 type = 0x0003 id = 0x12345678 content = 0xab12ef45 vertsion = struct.unpack('!H', package[0:2]) type = struct.unpack('!H', package[2:4]) id =

信息的表示和处理（整数部分）

由 别等时光非礼了梦想. 提交于 2020-04-06 13:50:09
这里通过分析一个练习题来总结： 考虑下列代码，这段代码试图计算数组a中所有元素的和，其中元素的数量由参数length给出。 /* WARNING: This is buggy code */ float sum_elements(float a[], unsigned length) { int i; float result = 0; for (i = 0; i <= length - 1; i++) result += a[j]; return result; } 当参数length等于0时，运行这段代码应该返回0.0。但实际上，运行时会遇到一个内存错误。请解释为什么会发生这样的情况，并且说明如何修改代码。 解： 首先我们发现参数length的形式参数的类型为unsigned，是一个无符号数，而无符号数是非负的，比如一个字节可以表示的无符号数范围是0~255，在代码中如果参数length等于0，则在循环中会首先对length减1来判断，而这个结果并不是一个负数，而是一个很大的正数。举个例子，对于一个字节，我们这里用十六进制来表示方便一点，0的十六进制为0x00，而0 - 1会得到0xFF，这个数表示为无符号数的大小为255，也就是一个字节所能表示的最大无符号数，这就产生了错误，但是如果我们用有符号数来解读0xFF，此时这个数的大小为-1，就正确了

linux Tasklet 实现

由 你。 提交于 2020-04-06 06:09:00
记住 tasklet 是一个特殊的函数, 可能被调度来运行, 在软中断上下文, 在一个系统决 定的安全时间中. 它们可能被调度运行多次, 但是 tasklet 调度不累积; ; tasklet 只 运行一次, 即便它在被投放前被重复请求. 没有 tasklet 会和它自己并行运行, 因为它 只运行一次, 但是 tasklet 可以与 SMP 系统上的其他 tasklet 并行运行. 因此, 如果 你的驱动有多个 tasklet, 它们必须采取某类加锁来避免彼此冲突. tasklet 也保证作为函数运行在第一个调度它们的同一个 CPU 上. 因此, 一个中断处理 可以确保一个 tasklet 在处理者结束前不会开始执行. 但是, 另一个中断当然可能在 tasklet 在运行时被递交, 因此, tasklet 和中断处理之间加锁可能仍然需要. tasklet 必须使用 DECLARE_TASKLET 宏来声明: DECLARE_TASKLET(name, function, data); name 是给 tasklet 的名子, function 是调用来执行 tasklet (它带一个 unsigned long 参数并且返回 void )的函数, 以及 data 是一个 unsigned long 值来传递给 tasklet 函数. short 驱动声明它的 tasklet 如下:
订阅 unsigned