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Is multiplication and division using shift operators in C actually faster?
... back, I benchmarked two
versions of my hashing algorithm:
unsigned
hash( char const* s )
{
unsigned h = 0;
while ( *s != '\0' ) {
h = 127 * h + (unsigned char)*s;
++ s;
}
return h;
}
and
unsigned
hash( char const* s )
{
unsigned h = 0;
while ( *s != '\0' ...
C语言判断文件是否存在 - C/C++ - 清泛网 - 专注C/C++及内核技术
...是否存在用函数access，头文件是io.h，原型：int access(const char *filename, int amode);amode参数为0时表示检查文件的存在性，如果文件存...用函数access，头文件是io.h，原型：
int access(const char *filename, int amode);
amode参数为0时表示检查文...
C: Run a System Command and Get Output? [duplicate]
...
#include <stdio.h>
#include <stdlib.h>
int main( int argc, char *argv[] )
{
FILE *fp;
char path[1035];
/* Open the command for reading. */
fp = popen("/bin/ls /etc/", "r");
if (fp == NULL) {
printf("Failed to run command\n" );
exit(1);
}
/* Read the output a ...
Why is C so fast, and why aren't other languages as fast or faster? [closed]
...what the machine does can be seen in the rules that govern the widening of char objects for use in expressions: whether the values of char objects widen to signed or unsigned quantities typically depends on which byte operation is more efficient on the target machine.
...
What is the difference between currying and partial application?
...m,_){1+accum})(empty-list);
function reverse = curry(fold)(lambda(accum,e){concat(e,accum)})(empty-list);
/* ... */
@list = [1, 2, 3, 4]
sum(list) //returns 10
@f = fold(lambda(accum,e){e+accum}) //f = lambda(accumulator,list) {/*...*/}
f(0,list) //returns 10
@g = f(0) //same as sum
g(list) //retu...
What is the difference between CHARACTER VARYING and VARCHAR in PostgreSQL?
John uses CHARACTER VARYING in the places where I use VARCHAR .
I am a beginner, while he is an expert.
This suggests me that there is something which I do not know.
...
半个汉字的校验与处理(C++) - C/C++ - 清泛网 - 专注C/C++及内核技术
...
// strSrc: 原始字符串
// nMaxLen: 截断后的最大长度
char *GetTruncate(char *strSrc, int nMaxLen)
{
if (strSrc == NULL || nMaxLen == 0)
{
return NULL;
}
int len = strlen(strSrc);
if (len == 0)
{
...
msvcr110d.dll!_CrtIsValidHeapPointer(const void * pUserData) 行 2036 ...
...出现问题了。
可能原因2：delete释放了常字符串。如 char *p = "abc"; delete p;
可能原因3：
CString m_strTest;
...
GetPrivateProfileString(INI_SECTION, "test", "", m_strTest.GetBuffer(), MAX_PATH, INI_FILE);
以上代码对话框资源释放的时候会崩溃，...
What's the best way to check if a String represents an integer in Java?
... if (length == 0) {
return false;
}
int i = 0;
if (str.charAt(0) == '-') {
if (length == 1) {
return false;
}
i = 1;
}
for (; i < length; i++) {
char c = str.charAt(i);
if (c < '0' || c > '9') {
retu...
How to generate and validate a software license key?
...hen:
Generate yourself a secret key for the product
Take the user's name
Concatentate the users name and the secret key and hash with (for example) SHA1
Unpack the SHA1 hash as an alphanumeric string. This is the individual user's "Product Key"
Within the program, do the same hash, and compare wit...