单片机下实现的部分经典C库函数，包括printf,memset等，可以用来学习printf源码实现方法

#include "myinclude.h" /* ********************************************************************************************************* * 复制 ********************************************************************************************************* */ void gmemcpy(void *pDst, const void *pSrc, unsigned long iNum) { unsigned long i; char *ucdst; char *ucsrc; ucdst = (char *)pDst; ucsrc = (char *)pSrc; for(i=0; i<iNum; ++i) { *ucdst++ = *ucsrc++; } } /* ********************************************************************************************************* * 设置 ********************************************************************************************************* */ void gmemset(void *pDst, unsigned char value, unsigned long iNum) { unsigned long i; char *ucdst; ucdst = (char*)pDst; for(i=0; i<iNum; ++i) { *ucdst++ = value; } } /* ********************************************************************************************************* * 比较 ********************************************************************************************************* */ char gmemcmp(const void *buf1, const void *buf2, unsigned long count) { if(!count) return(0); while ( --count && *(char *)buf1 == *(char *)buf2) { buf1 = (char *)buf1 + 1; buf2 = (char *)buf2 + 1; } return( *((unsigned char *)buf1) - *((unsigned char *)buf2) ); } /* ********************************************************************************************************* * 取字符串长度 ********************************************************************************************************* */ unsigned short gstrlen(const char *strbuf) { unsigned short i; for(i=0; strbuf[i]; i++); return i; } /* ********************************************************************************************************* * 字符串截取(参数const char*) ********************************************************************************************************* */ char *gstrtok(char *strbuf, const char *dm) { static char *last; char *tok; if(strbuf == NULL) strbuf = last; if(strbuf == NULL) return NULL; tok = (char *)strbuf; while((*strbuf) != '\0') { while(*dm) { if(*strbuf == *dm) { *strbuf = '\0'; last = strbuf + 1; break; } strbuf++; } } return tok; } /* ********************************************************************************************************* * 字符串截取(参数char) ********************************************************************************************************* */ char *gstrtokc(char *strbuf, char dm) { static char *last; char *tok; if(strbuf == NULL) strbuf = last; if(strbuf == NULL) return NULL; tok = (char *)strbuf; while((*strbuf) != '\0') { while(dm) { if(*strbuf == dm) { *strbuf = '\0'; last = strbuf + 1; break; } strbuf++; } } return tok; } /* ********************************************************************************************************* * 字符串数字转 ********************************************************************************************************* */ char isspace(char x) { if((x==' ')||(x=='\t')||(x=='\n')||(x=='\f')||(x=='\b')||(x=='\r')) return 1; else return 0; } char isdigit(char x) { if((x<='9') && (x>='0')) return 1; else return 0; } long gatoi(const char *nptr) { unsigned char c; // current char unsigned char sign; // if '-', then negative, otherwise positive long total; // current total // skip whitespace while(isspace((char)*nptr)) ++nptr; c = (unsigned char)*nptr++; sign = c; // save sign indication if (c == '-' || c == '+') c = (unsigned char)*nptr++; // skip sign total = 0; while (isdigit((char)c)) { total = 10 * total + (c - '0');// accumulate digit c = (unsigned char)*nptr++; // get next char } if (sign == '-') return -total; else return total; // return result, negated if necessary } /* ********************************************************************************************************* * printf函数 ********************************************************************************************************* */ //#include <stdarg.h> //使用可变参数必须要加的头文件 #ifdef _M_ALPHA typedef struct { char *a0; // pointer to first homed integer argument int offset; // byte offset of next parameter } va_list; #else typedef char * va_list; #endif //_INTSIZEOF 宏，获取类型占用的空间长度，最小占用长度为int的整数倍： #define _INTSIZEOF(n) ( (sizeof(n) + sizeof(int) - 1) & ~(sizeof(int) - 1) ) //VA_START宏，获取可变参数列表的第一个参数的地址（ap是类型为va_list的指针，v是可变参数最左边的参数）： #define va_start(ap,v) ( ap = (va_list)&v + _INTSIZEOF(v) ) //VA_ARG宏，获取可变参数的当前参数，返回指定类型并将指针指向下一参数（t参数描述了当前参数的类型）： #define va_arg(ap,t) ( *(t *)((ap += _INTSIZEOF(t)) - _INTSIZEOF(t)) ) //VA_END宏，清空va_list可变参数列表： #define va_end(ap) ( ap = (va_list)0 ) /********************************************************************/ typedef struct { int dest; void (*func)(char); char *loc; } PRINTK_INFO; int printk (PRINTK_INFO *, const char *, va_list); /********************************************************************/ #define FLAGS_MINUS (0x01) #define FLAGS_PLUS (0x02) #define FLAGS_SPACE (0x04) #define FLAGS_ZERO (0x08) #define FLAGS_POUND (0x10) #define IS_FLAG_MINUS(a) (a & FLAGS_MINUS) #define IS_FLAG_PLUS(a) (a & FLAGS_PLUS) #define IS_FLAG_SPACE(a) (a & FLAGS_SPACE) #define IS_FLAG_ZERO(a) (a & FLAGS_ZERO) #define IS_FLAG_POUND(a) (a & FLAGS_POUND) #define LENMOD_h (0x01) #define LENMOD_l (0x02) #define LENMOD_L (0x04) #define IS_LENMOD_h(a) (a & LENMOD_h) #define IS_LENMOD_l(a) (a & LENMOD_l) #define IS_LENMOD_L(a) (a & LENMOD_L) #define FMT_d (0x0001) #define FMT_o (0x0002) #define FMT_x (0x0004) #define FMT_X (0x0008) #define FMT_u (0x0010) #define FMT_c (0x0020) #define FMT_s (0x0040) #define FMT_p (0x0080) #define FMT_n (0x0100) #define IS_FMT_d(a) (a & FMT_d) #define IS_FMT_o(a) (a & FMT_o) #define IS_FMT_x(a) (a & FMT_x) #define IS_FMT_X(a) (a & FMT_X) #define IS_FMT_u(a) (a & FMT_u) #define IS_FMT_c(a) (a & FMT_c) #define IS_FMT_s(a) (a & FMT_s) #define IS_FMT_p(a) (a & FMT_p) #define IS_FMT_n(a) (a & FMT_n) /********************************************************************/ static void printk_putc (char c, int *count, PRINTK_INFO *info) { switch (info->dest) { case DEST_CONSOLE: info->func((unsigned char)c); break; case DEST_STRING: info->func((unsigned char)c); break; case DEST_BUFFER: *info->loc = (unsigned char)c;