获取数组长度
/// Obtain the number of elements in the given C array
#define GET_ARRAY_LEN( arrayName ) (sizeof( arrayName ) / sizeof(( arrayName)[ 0 ] ))使用例子：
#include <stdio.h>
/// Obtain the number of elements in the given C array
#define GET_ARRAY_LEN( arrayName ) (sizeof( arrayName ) / sizeof(( arrayName)[ 0 ] ))
int main()
{
int iarray[20] = {0};
printf("iarray len = %d\n",GET_ARRAY_LEN(iarray));
char carray[40] = {0};
printf("carray len = %d\n",GET_ARRAY_LEN(carray));
return 0;
}
比较数字大小
/// Return min of two numbers. Commonly used but never defined as part of standard headers
#ifndef MIN
#define MIN( n1, n2 ) ((n1) > (n2) ? (n2) : (n1))
#endif
/// Return max of two numbers. Commonly used but never defined as part of standard headers
#ifndef MAX
#define MAX( n1, n2 ) ((n1) > (n2) ? (n1) : (n2))
#endif使用例子：
#include <stdio.h>
/// Return min of two numbers. Commonly used but never defined as part of standard headers
#ifndef MIN
#define MIN( n1, n2 ) ((n1) > (n2) ? (n2) : (n1))
#endif
/// Return max of two numbers. Commonly used but never defined as part of standard headers
#ifndef MAX
#define MAX( n1, n2 ) ((n1) > (n2) ? (n1) : (n2))
#endif
int main()
{
printf("MIN(3,5) = %d\n",MIN(3,5));
printf("MAX(3,5) = %d\n",MAX(3,5));
printf("MIN(3,MAX(3,5)) = %d\n",MIN(3,MAX(3,5)));
printf("MIN(MIN(3,5),5) = %d\n",MIN(MIN(3,5),5));
return 0;
}判断奇偶数和数字是否在区间内
/// Determine whether the given signed or unsigned integer is odd.
#define IS_ODD( num ) ((num) & 1)
/// Determine whether the given signed or unsigned integer is even.
#define IS_EVEN( num ) (!IS_ODD( (num) ))
/**
Determine whether the given number is between the other two numbers
(both inclusive).
*/
#define IS_BETWEEN( numToTest, numLow, numHigh ) \
((unsigned char)((numToTest) >= (numLow) && (numToTest) <= (numHigh)))结构体成员偏移量
判断大端小端
/**
Determines whether the memory architecture of current processor is LittleEndian.
*/
#define IS_LITTLE_ENDIAN() (((*(short *)"21") & 0xFF) == '2')
/**
Determines whether the memory architecture of current processor is BigEndian.
*/
#define IS_BIG_ENDIAN() (((*(short *)"21") & 0xFF) == '1')
/**
Change this macro to change the default endian format. In this example,
the default endian format is Little Endian.
*/
#define IS_DEFAULT_ENDIAN() IS_LITTLE_ENDIAN()
计算给定数字下一个能被n整除的数
开发中需要判断给定数字是否能被n整除，如果不能被n整除则计算下一个能被n整除的数字。
例子：
#include <stdio.h>
int main()
{
int myint = 16;
int result = (myint + 7) & ~0x07;
printf("%d\n",result);
int mynum = 17;
result = (mynum + 7) & ~0x07;
printf("%d\n",result);
return 0;
}
参考：
我最初使用的版本如下：
#include <stdio.h>
int main()
{
int myint = 16;
int result = (myint + 7)/8 * 8;
printf("%d\n",result);
int mynum = 17;
result = (mynum + 7)/8 * 8;
printf("%d\n",result);
return 0;
}
对比位运算版本效率较低，计算机的世界里位运算要远远比除法高效的多。
free内存
#define SAFE_FREE(p) if(p != NULL) {free(p); p = NULL;}
节省了代码的体量，减少重复代码。
常规写法：
if(p)
{
free(p);
p = NULL;
}
extern c宏
#ifdef __cplusplus
#define DECLS_BEGIN extern "C" {
#define DECLS_END }
#else
#define DECLS_BEGIN
#define DECLS_END
#endif/*__cplusplus*/
用法示例：
在c/c++混合编程中，我们通常在c头文件中使用如下方式
ifdef __cplusplus
extern "C"{
#endif
some code stuff
#ifdef __cplusplus
}
#endif
使用我们的宏的化用法：
DECLS_BEGIN
some code stuff
DECLS_END
c语言简单单元测试框架
源代码
/* file: minunit.h */
#define mu_assert(message, test) do { if (!(test)) return message; } while (0)
#define mu_run_test(test) do { char *message = test(); tests_run++; \
if (message) return message; } while (0)
extern int tests_run;
/* file minunit_example.c */
#include <stdio.h>
#include "minunit.h"
int tests_run = 0;
int foo = 7;
int bar = 4;
static char * test_foo() {
mu_assert("error, foo != 7", foo == 7);
return 0;
}
static char * test_bar() {
mu_assert("error, bar != 5", bar == 5);
return 0;
}
static char * all_tests() {
mu_run_test(test_foo);
mu_run_test(test_bar);
return 0;
}
int main(int argc, char **argv) {
char *result = all_tests();
if (result != 0) {
printf("%s\n", result);
}
else {
printf("ALL TESTS PASSED\n");
}
printf("Tests run: %d\n", tests_run);
return result != 0;
}执行结果:
[root minunit]#gcc -g -o minunit minunit_example.c
[root minunit]#./minunit
error, bar != 5
Tests run: 2
非技术的路过。