C语言容易被忽视的函数设计原则是什么

这篇文章主要介绍了C语言容易被忽视的函数设计原则是什么的相关知识，内容详细易懂，操作简单快捷，具有一定借鉴价值，相信大家阅读完这篇C语言容易被忽视的函数设计原则是什么文章都会有所收获，下面我们一起来看看吧。

函数设计原则

• 函数从意义上应该是一个独立的功能模块

• 函数名要在一定程度上反映函数的功能

• 函数参数名要能够体现参数的意义

• 尽量避免在函数中使用全局变量

• 当函数参数不应该在函数体内部被修改时，应加上 const 声明

• 如果参数是指针，且仅作输入参数，则应加上 const 声明，如下：

• 不能省略返回值的类型

• 如果函数没有返回值，那么应声明为 void

• 类型对参数进行有效性检查

• 对于指针参数的检查尤为重要

• 不要返回指向"栈内存"的指针

• 栈内存在函数体结束时被自动释放

• 函数体的规模要小，尽量控制在 80 行代码之内

• 相同的输入对应相同的输出，避免函数带有"记忆"功能

• 避免函数有过多的参数，参数个数尽量控制在 4 个以内

• 有时候函数不需要返回值，但为了增加灵活性，如支持链式表达，可以附加返回值

• 函数名与返回值类型在语义上不可冲突

下面来欣赏一份优秀的代码：

/******************************************************************************* * Copyright (c) 2000, 2005 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at  * http://www.eclipse.org/legal/epl-v10.html *  * Contributors: *     IBM Corporation - initial API and implementation *     Kevin Cornell (Rational Software Corporation) *******************************************************************************//* Eclipse Launcher Utility Methods */#include "eclipseOS.h"#include "eclipseCommon.h"#include "eclipseUtil.h"#include #include #include #include #ifdef _WIN32#include #else#include #include #endif#define MAX_LINE_LENGTH 256/* Is the given VM J9 */int isJ9VM( _TCHAR* vm ){        _TCHAR * ch = NULL, *ch3 = NULL;        int res = 0;        if (vm == NULL)                return 0;        ch = lastDirSeparator( vm );        if (isVMLibrary(vm)) {                /* a library, call it j9 if the parent dir is j9vm */                if(ch == NULL)                        return 0;                ch[0] = 0;                ch3 = lastDirSeparator(vm);                if(ch3 != NULL) {                        res = (_tcsicmp(ch3 + 1, _T_ECLIPSE("j9vm")) == 0);                }                ch[0] = dirSeparator;                return res;        } else {                if (ch == NULL)                    ch = vm;                else                    ch++;                return (_tcsicmp( ch, _T_ECLIPSE("j9") ) == 0);        }}int checkProvidedVMType( _TCHAR* vm ) {        _TCHAR* ch = NULL;        struct _stat stats;        if (vm == NULL) return VM_NOTHING;        if (_tstat(vm, &stats) == 0 && (stats.st_mode & S_IFDIR) != 0) {                /* directory */                return VM_DIRECTORY;        }        ch = _tcsrchr( vm, _T_ECLIPSE('.') );        if(ch == NULL)                return VM_OTHER;#ifdef _WIN32        if (_tcsicmp(ch, _T_ECLIPSE(".dll")) == 0)#else        if ((_tcsicmp(ch, _T_ECLIPSE(".so")) == 0) || (_tcsicmp(ch, _T_ECLIPSE(".jnilib")) == 0) || (_tcsicmp(ch, _T_ECLIPSE(".dylib")) == 0))#endif        {                return VM_LIBRARY;        }        if (_tcsicmp(ch, _T_ECLIPSE(".ee")) == 0)                return VM_EE_PROPS;        return VM_OTHER;}/* * pathList is a pathSeparator separated list of paths, run each through * checkPath and recombine the results. * New memory is always allocated for the result */_TCHAR * checkPathList( _TCHAR* pathList, _TCHAR* programDir, int reverseOrder) {        _TCHAR * c1, *c2;        _TCHAR * checked, *result;        size_t checkedLength = 0, resultLength = 0;        size_t bufferLength = _tcslen(pathList);        result = malloc(bufferLength * sizeof(_TCHAR));        c1 = pathList;    while (c1 != NULL && *c1 != _T_ECLIPSE('\0'))    {            c2 = _tcschr(c1, pathSeparator);                if (c2 != NULL)                        *c2 = 0;                checked = checkPath(c1, programDir, reverseOrder);                checkedLength = _tcslen(checked);                if (resultLength + checkedLength + 1> bufferLength) {                        bufferLength += checkedLength + 1;                        result = realloc(result, bufferLength * sizeof(_TCHAR));                }                if(resultLength > 0) {                        result[resultLength++] = pathSeparator;                        result[resultLength] = _T_ECLIPSE('\0');                }                _tcscpy(result + resultLength, checked);                resultLength += checkedLength;                if(checked != c1)                        free(checked);                if(c2 != NULL)                        *(c2++) = pathSeparator;                c1 = c2;        }    return result;}_TCHAR * concatStrings(_TCHAR**strs) {        return concatPaths(strs, 0);}_TCHAR * concatPaths(_TCHAR** strs, _TCHAR separator) {        _TCHAR separatorString[] = { separator, 0 };        _TCHAR * result;        int i = -1;        size_t length = 0;        /* first count how large a buffer we need */        while (strs[++i] != NULL) {                length += _tcslen(strs[i]) + (separator != 0 ? 1 : 0);        }        result = malloc((length + 1) * sizeof(_TCHAR));        result[0] = 0;        i = -1;        while (strs[++i] != NULL) {                result = _tcscat(result, strs[i]);                if (separator != 0)                        result = _tcscat(result, separatorString);        }        return result;}/* * buffer contains a pathSeparator separated list of paths, check  * that it contains all the paths given.  Each path is expected to be * terminated with a pathSeparator character. */int containsPaths(_TCHAR * str, _TCHAR** paths) {        _TCHAR * buffer;        _TCHAR * c;        int i;        /* terminate the string with a pathSeparator */        buffer = malloc((_tcslen(str) + 2) * sizeof(_TCHAR));        _stprintf(buffer, _T_ECLIPSE("%s%c"), str, pathSeparator);        for (i = 0; paths[i] != NULL; i++) {                c = _tcsstr(buffer, paths[i]);                if ( c == NULL || !(c == buffer || *(c - 1) == pathSeparator))                {                        /* entry not found */                        free(buffer);                        return 0;                }        }        free(buffer);        return 1;}int isVMLibrary( _TCHAR* vm ){        _TCHAR *ch = NULL;        if (vm == NULL) return 0;        ch = _tcsrchr( vm, '.' );        if(ch == NULL)                return 0;#ifdef _WIN32        return (_tcsicmp(ch, _T_ECLIPSE(".dll")) == 0);#else        return (_tcsicmp(ch, _T_ECLIPSE(".so")) == 0) || (_tcsicmp(ch, _T_ECLIPSE(".jnilib")) == 0) || (_tcsicmp(ch, _T_ECLIPSE(".dylib")) == 0);#endif}#ifdef AIX#include #include /* Return the JVM version in the format x.x.x  */char* getVMVersion( char *vmPath ){    char   cmd[MAX_LINE_LENGTH];    char   lineString[MAX_LINE_LENGTH];    char*  firstChar;    char   fileName[MAX_LINE_LENGTH];    time_t curTime;    FILE*  fp;    int    numChars = 0;    char*  version  = NULL;        /* Define a unique filename for the java output. */    (void) time(&curTime);    (void) sprintf(fileName, "/tmp/tmp%ld.txt", curTime);    /* Write java -version output to a temp file */    (void) sprintf(cmd,"%s -version 2> %s", vmPath, fileName);    (void) system(cmd);     fp = fopen(fileName, "r");    if (fp != NULL)    {            /* Read java -version output from a temp file */            if (fgets(lineString, MAX_LINE_LENGTH, fp) == NULL)                    lineString[0] = '\0';            fclose(fp);            unlink(fileName);            /* Extract version number */            firstChar = (char *) (strchr(lineString, '"') + 1);            if (firstChar != NULL)                    numChars = (int)  (strrchr(lineString, '"') - firstChar);            /* Allocate a buffer and copy the version string into it. */            if (numChars > 0)            {                    version = malloc( numChars + 1 );                    strncpy(version, firstChar, numChars);                        version[numChars] = '\0';                }        }      return version;}/* Compare JVM Versions of the form "x.x.x..." *      *    Returns -1 if ver1 < ver2 *    Returns  0 if ver1 = ver2  *    Returns  1 if ver1 > ver2 */     int versionCmp(char *ver1, char *ver2){    char*  dot1;    char*  dot2;    int    num1;    int    num2;    dot1 = strchr(ver1, '.');    dot2 = strchr(ver2, '.');    num1 = atoi(ver1);    num2 = atoi(ver2);    if (num1 > num2)            return 1;        if (num1 < num2)                return -1;        if (dot1 && !dot2)   /* x.y > x */        return 1;    if (!dot1 && dot2)   /* x < x.y */        return -1;    if (!dot1 && !dot2)  /* x == x */        return 0;    return versionCmp((char*)(dot1 + 1), (char*)(dot2 + 1) );}#endif /* AIX */

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