unsigned

Python struct模块

由 人盡茶涼 提交于 2020-01-03 23:03:15
由于Python没有专门处理字节的数据类型，Python提供了一个struct模块来解决bytes和其他二进制数据类型的转换。 struct的pack函数把任意数据类型变成bytes import struct r = struct . pack ( '>l' , 99999999 ) print ( r ) pack的第一个参数是处理指令 > 表示字节顺序是大端序 < 表示小端序 ! 网络序列, 也是大端序 格式 类型 字节 i int 4 c char 1 f float 4 d double 8 s char[] 1 I unsigned int h short 2 ? bool 1 q long long 8 Q unsigned long long 8 L unsigned long 4 H unsigned short 2 常用的两个api就是 pack() 与 unpack() uppack返回一个tuple, import struct s = 'moddemod' . encode ( ) r1 = struct . pack ( '>8s' , s ) r2 , = struct . unpack ( '>8s' , r1 ) print ( r2 . decode ( ) ) # moddemod 这里其实是对应c语言的数据类型,因为数据传输都是字节流传输的

MySQL integer unsigned arithmetic problems?

由 折月煮酒 提交于 2020-01-03 16:44:20
问题 Does MySQL (5.0.45) like to do strange internal typecasts with unsigned maths? I am storing integers unsigned but when selecting basic arithmetic I get outrageous numbers: mysql> create table tt ( a integer unsigned , b integer unsigned , c float ); Query OK, 0 rows affected (0.41 sec) mysql> insert into tt values (215731,216774,1.58085); Query OK, 1 row affected (0.00 sec) mysql> select a,b,c from tt; +--------+--------+---------+ | a | b | c | +--------+--------+---------+ | 215731 | 216774

MySQL integer unsigned arithmetic problems?

由 匆匆过客 提交于 2020-01-03 16:44:13
问题 Does MySQL (5.0.45) like to do strange internal typecasts with unsigned maths? I am storing integers unsigned but when selecting basic arithmetic I get outrageous numbers: mysql> create table tt ( a integer unsigned , b integer unsigned , c float ); Query OK, 0 rows affected (0.41 sec) mysql> insert into tt values (215731,216774,1.58085); Query OK, 1 row affected (0.00 sec) mysql> select a,b,c from tt; +--------+--------+---------+ | a | b | c | +--------+--------+---------+ | 215731 | 216774

MySQL integer unsigned arithmetic problems?

由 风格不统一 提交于 2020-01-03 16:43:05
问题 Does MySQL (5.0.45) like to do strange internal typecasts with unsigned maths? I am storing integers unsigned but when selecting basic arithmetic I get outrageous numbers: mysql> create table tt ( a integer unsigned , b integer unsigned , c float ); Query OK, 0 rows affected (0.41 sec) mysql> insert into tt values (215731,216774,1.58085); Query OK, 1 row affected (0.00 sec) mysql> select a,b,c from tt; +--------+--------+---------+ | a | b | c | +--------+--------+---------+ | 215731 | 216774

unsigned overflow with modulus operator in C

由 你离开我真会死。 提交于 2020-01-03 12:02:26
问题 i encountered a bug in some c code i wrote, and while it was relatively easy to fix, i want to be able to understand the issue underlying it better. essentially what happened is i had two unsigned integers (uint32_t, in fact) that, when the modulus operation was applied, yielded the unsigned equivalent of a negative number, a number that had been wrapped and was thus "big". here is an example program to demonstrate: #include <stdio.h> #include <stdint.h> int main(int argc, char* argv[]) {

Convert int to unsigned short java

由 浪子不回头ぞ 提交于 2020-01-03 10:56:05
问题 I have written a .obj parser in java to modelize 3D objects on iPhone. I would like to export the data as a binary file, which must be as small as possible. I have plenty of indices that would fit a unsigned short, but they are represented as int in java. I would like to use the ByteBuffer class to do the conversion just before writing the data in a file. I suppose I will have to manipulate bytes before pushing them into the ByteBuffer but I have no idea how to do so. Thank you in advance if

Is INT_MAX+1 = INT_MIN in signed integer? [duplicate]

由 痞子三分冷 提交于 2020-01-03 06:51:10
问题 This question already has answers here : for every int x: x+1 > x … is this always true? (4 answers) Closed 6 years ago . for (i = 0; i <= N; ++i) { ... } This particular statement will cause an infinite loop if N is INT_MAX . Having known that Unsigned Overflows are wrapping overflows, assuming i and N to unsigned, compiler can assume that the loop will iterate exactly N+1 times if i is undefined on overflow. The thing to note here is: if I make the loops as, for (i = 0; i < N; ++i) { ... }

mysql中的unsigned和signed

由 空扰寡人 提交于 2020-01-03 04:08:24
第一：拿tinyint字段来举例，unsigned后，字段的取值范围是0-255，而signed的范围是-128 - 127。 第二：unsigned的性能更好，当只存储正整数的情况下。 因为，当unsigned时，假设查询值在500以下的数据，那么MySQL会将范围定义为：0-500，而如果是signed，则查询范围为：-2147483648 - 500。 来源： CSDN 作者： 南山以南青如山 链接： https://blog.csdn.net/qq_42615032/article/details/103798589

VC编程规范

由 会有一股神秘感。 提交于 2020-01-03 01:34:34
1. 基本要求 1.1 程序结构清析，简单易懂，单个函数的程序行数不得超过100行。 1.2 打算干什么，要简单，直接了当，代码精简，避免垃圾程序。 1.3 尽量使用标准库函数和公共函数。 1.4 不要随意定义全局变量，尽量使用局部变量。 1.5 使用括号以避免二义性。 2.可读性要求 2.1 可读性第一，效率第二。 2.2 保持注释与代码完全一致。 2.3 每个源程序文件，都有文件头说明，说明规格见规范。 2.4 每个函数，都有函数头说明，说明规格见规范。 2.5 主要变量（结构、联合、类或对象）定义或引用时，注释能反映其含义。 2.7 常量定义（DEFINE）有相应说明。 2.8 处理过程的每个阶段都有相关注释说明。 2.9 在典型算法前都有注释。 2.10 利用缩进来显示程序的逻辑结构，缩进量一致并以Tab键为单位，定义Tab为 6个 字节。 2.11 循环、分支层次不要超过五层。 2.12 注释可以与语句在同一行，也可以在上行。 2.13 空行和空白字符也是一种特殊注释。 2.14 一目了然的语句不加注释。 2.15 注释的作用范围可以为：定义、引用、条件分支以及一段代码。 2.16 注释行数（不包括程序头和函数头说明部份）应占总行数的 1/5 到 1/3 。 3. 结构化要求 3.1 禁止出现两条等价的支路。 3.2 禁止GOTO语句。 3.3 用 IF

在C语言中，double、long、unsigned、int、char类型数据所占字节数

由 北战南征 提交于 2020-01-01 09:06:31
和机器字长及编译器有关系： 所以，int，long int，short int的宽度都可能随编译器而异。但有几条铁定的原则（ANSI/ISO制订的）： 1 sizeof(short int)<=sizeof(int) 2 sizeof(int)<=sizeof(long int) 3 short int至少应为16位（2字节） 4 long int至少应为32位。 unsigned 是无符号的意思。 例如： 16位编译器 char ：1个字节 char*(即指针变量): 2个字节 short int : 2个字节 int： 2个字节 unsigned int : 2个字节 float: 4个字节 double: 8个字节 long: 4个字节 long long: 8个字节 unsigned long: 4个字节 32位编译器 char ：1个字节 char*（即指针变量）: 4个字节（32位的寻址空间是2^32, 即32个bit，也就是4个字节。同理64位编译器） short int : 2个字节 int： 4个字节 unsigned int : 4个字节 float: 4个字节 double: 8个字节 long: 4个字节 long long: 8个字节 unsigned long: 4个字节 64位编译器 char ：1个字节 char*(即指针变量): 8个字节
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