1. 函数设计原则
（1）函数从意义上应该是一个独立的功能模块
（2）函数名要在一定程度上反映函数的功能
（3）函数参数名要能够体现参数的意义
（4）尽量避免在函数中使用全局变量
void sc(char *s1, char* s1);×
void str_copy(char* dest, char* src); √
（5）当函数参数不应该在函数体内部被修改时，应加上const声明
（6）如果参数是指针，且仅作输入参数，则应加上const声明
void str_copy(char* dest, const char* src);
（7）不能省略返回值的类型。如果没有返回值，应声明为void。
（8）对参数进行有效性检查，特别是指针参数的检查尤为重要
（9）不要返回指向“栈内存”的指针，因为栈内存在函数体结束时被自动释放
（10）函数体的规模要小，尽量控制在80行代码之内
（11）相同的输入对应相同的输出，避免函数带有“记忆”功能
（12）避免函数有过多的参数，参数个数尽量控制在4个以内
（13）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
char s[64];
int len = strlen(strcpy(s, "Hello")); //当中的strcpy返回缓冲区s的地址。
（14）函数名和返回值类型在语义上不可冲突
char c = getchar(); //getchar的返回值实际上是int类型，而不是char。与函数名不符。
2. 课程总结
（1）C语言的学习需要勤思考、勤动手才能得到提高
（2）难点部分为指针（指针的本质、指针的运算、指针和数组）
（3）学习过程可以采用各个击破的方法，在一个特定的时间段只重点学习和练习某个主题
【实例分析】优秀代码赏析eclipseUtil.c
/******************************************************************************* * 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 <string.h> #include <stdlib.h> #include <stdio.h> #include <sys/stat.h> #ifdef _WIN32 #include <direct.h> #else #include <unistd.h> #include <strings.h> #endif #define MAX_LINE_LENGTH 256 /* Is the given VM J9 */ int isJ9VM(_TCHAR* vm) { _TCHAR * ch = NULL, *ch2 = 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; ch2 = lastDirSeparator(vm); if (ch2 != NULL) { res = (_tcsicmp(ch2 + 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(' ')) { 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(' '); } _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 <sys/types.h> #include <time.h> /* 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] = ' '; 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] = ' '; } } 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 */