조각코드 : glibc 함수의 유저 구현

#include "small_libc_conf.h"
#define NULL            0x0
 
#if _USE_STRCPY_                        
char *strcpy(char *dst, const char *src) {
        char *dstSave=dst;
        int c;
 
        do {
                c = *dst++ = *src++;
        } while(c);
 
        return dstSave;
}
#endif
 
#if _USE_STRNCPY_                       
char *strncpy(char *dst, const char *src, int count) {
        int c = 1;
        char *dstSave = dst;
 
        while(count-- > 0 && c)
                c = *dst++ = *src++;
 
        *dst = 0;
        return dstSave;
}
#endif
 
 
#if _USE_STRCAT_                        
char *strcat(char *dst, const char *src) {
        int c;
        char *dstSave=dst;
 
        while(*dst)
                ++dst;
 
        do {
                c = *dst++ = *src++;
        } while(c);
 
        return dstSave;
}
#endif
 
 
#if _USE_STRNCAT_                       
char *strncat(char *dst, const char *src, int count) {
        int c = 1;
        char *dstSave = dst;
 
        while(*dst && --count > 0)
                ++dst;
        while(--count > 0 && c)
                c = *dst++ = *src++;
        *dst = 0;
        return dstSave;
}
#endif
 
 
#if _USE_STRCMP_                        
int strcmp(const char *string1, const char *string2) {
        int diff, c;
        for(;;) {
                diff = *string1++ - (c = *string2++);
 
                if(diff) return diff;
                if(c == 0) return 0;
        }
}
#endif
 
 
#if _USE_STRNCMP_                       
int strncmp(const char *string1, const char *string2, int count) {
        int diff, c;
        while(count-- > 0) {
                diff = *string1++ - (c = *string2++);
 
                if(diff) return diff;
                if(c == 0) return 0;
        }
        return 0;
}
#endif
 
 
#if _USE_STRSTR_                        
char *strstr(const char *string, const char *find) {
        int i;
        for(;;) {
                for(i = 0; string[i] == find[i] && find[i]; ++i) ;
 
                if(find[i] == 0) return (char*)string;
                if(*string++ == 0) return NULL;
        }
}
#endif
 
 
#if _USE_STRLEN_                        
int strlen(const char *string) {
        const char *base=string;
        while(*string++) ;
        return string - base - 1;
}
#endif
 
 
#if _USE_MEMCPY_                        
void *memcpy(void *dst, const void *src, unsigned long bytes) {
        if(((unsigned long)dst | (unsigned long)src | bytes) & 3) {
                unsigned char *Dst = (unsigned char*)dst, *Src = (unsigned char*)src;
                while((int)bytes-- > 0)
                        *Dst++ = *Src++;
        } else {
                unsigned long *Dst32 = (unsigned long*)dst, *Src32 = (unsigned long*)src;
                bytes >>= 2;
                while((int)bytes-- > 0)
                        *Dst32++ = *Src32++;
        }
 
        return dst;
}
#endif
 
 
#if _USE_MEMMOVE_                       
void *memmove(void *dst, const void *src, unsigned long bytes) {
        unsigned char *Dst = (unsigned char*)dst;
        unsigned char *Src = (unsigned char*)src;
 
        if(Dst < Src) {
                while((int)bytes-- > 0)
                        *Dst++ = *Src++;
        } else {
                Dst += bytes;
                Src += bytes;
                while((int)bytes-- > 0)
                        *--Dst = *--Src;
        }
        return dst;
}
#endif
 
 
#if _USE_MEMCMP_                        
int memcmp(const void *cs, const void *ct, unsigned long bytes) {
        unsigned char *Dst = (unsigned char*)cs;
        unsigned char *Src = (unsigned char*)ct;
        int diff;
 
        while((int)bytes-- > 0) {
                diff = *Dst++ - *Src++;
                if(diff) return diff;
        }
 
        return 0;
}
#endif
 
 
#if _USE_MEMSET_
void *memset(void *dst, int c, unsigned long bytes) {
        unsigned char *Dst = (unsigned char*)dst;
        while((int)bytes-- > 0)
                *Dst++ = (unsigned char)c;
        return dst;
}
#endif
 
 
#if _USE_ABS_                           
int abs(int n) {
        return n>=0 ? n : -n;
}
#endif
 
 
#if _USE_RAND_                          
static unsigned int Rand1=0x1f2bcda3;
int rand(void) {
        Rand1 = 1664525 * Rand1 + 1013904223;  //from D.E. Knuth and H.W. Lewis
        return Rand1;
}
 
 
void srand(unsigned int seed) {
        Rand1 = seed;
}
#endif
 
 
#if _USE_STRTOL_                        
long strtol(const char *s, char **end, int base) {
        int i;
        unsigned long ch, value=0, neg=0;
 
        if(s[0] == '-') {
                neg = 1;
                ++s;
        }
 
        if(s[0] == '0' && s[1] == 'x') {
                base = 16;
                s += 2;
        }
 
        for(i = 0; i <= 8; ++i) {
                ch = *s++;
                if('0' <= ch && ch <= '9')
                        ch -= '0';
                else if('A' <= ch && ch <= 'Z')
                        ch = ch - 'A' + 10;
                else if('a' <= ch && ch <= 'z')
                        ch = ch - 'a' + 10;
                else
                        break;
                value = value * base + ch;
        }
 
        if(end) *end = (char*)s - 1;
        if(neg) value = -(int)value;
        return value;
}
#endif
 
 
#if _USE_ATOI_                          
int atoi(const char *s) {
        return strtol(s, NULL, 10);
}
#endif
 
 
#if _USE_ITOA_                          
char *itoa(int num, char *dst, int base) {
        int digit, negate=0, place;
        char c, text[20];
 
        if(base == 10 && num < 0) {
                num = -num;
                negate = 1;
        }
 
        text[16] = 0;
 
        for(place = 15; place >= 0; --place) {
                digit = (unsigned int)num % (unsigned int)base;
 
                if(num == 0 && place < 15 && base == 10 && negate) {
                        c = '-';
                        negate = 0;
                } else if(digit < 10)
                        c = (char)('0' + digit);
                else
                        c = (char)('a' + digit - 10);
                text[place] = c;
                num = (unsigned int)num / (unsigned int)base;
                if(num == 0 && negate == 0)
                        break;
        }
        strcpy(dst, text + place);
        return dst;
}
#endif
 
 
#if _USE_ISLOWER_                       
int islower(int c) {
        return (c >= 'a'  &&  c <= 'z');
}
#endif
 
 
#if _USE_ISUPPER_                       
int isupper(int c) {
        return (c >= 'A' && c <= 'Z');
}
#endif
 
 
#if _USE_TOUPPER_                       
int toupper(int c) {
        return (c & ~' ');
}
#endif
 
 
#if _USE_TOLOWER_                       
int tolower(int c) {
        return (c | ' ');
}
#endif
 
////////////////////////////// small_libc.h /////////////////////////////////////
#ifndef __SMALL_LIBC_H_
#define __SMALL_LIBC_H_
 
char *strcpy(char *dst, const char *src);
char *strncpy(char *dst, const char *src, int count);
char *strcat(char *dst, const char *src);
char *strncat(char *dst, const char *src, int count);
int strcmp(const char *string1, const char *string2);
int strncmp(const char *string1, const char *string2, int count);
char *strstr(const char *string, const char *find);
int strlen(const char *string);
void *memcpy(void *dst, const void *src, unsigned long bytes);
void *memmove(void *dst, const void *src, unsigned long bytes);
int memcmp(const void *cs, const void *ct, unsigned long bytes);
void *memset(void *dst, int c, unsigned long bytes);
int abs(int n);
int rand(void);
void srand(unsigned int seed);
long strtol(const char *s, char **end, int base);
int atoi(const char *s);
char *itoa(int num, char *dst, int base);
int islower(int c);
int isupper(int c);
int toupper(int c);
int tolower(int c);
 
#endif
 
////////////////////////////// small_libc_conf.h /////////////////////////////////////
#ifndef __SMALL_LIBC_CONF_H__
#define __SMALL_LIBC_CONF_H__
 
#define _USE_STRCPY_                    1
#define _USE_STRNCPY_                   1
#define _USE_STRNCAT_                   1
#define _USE_STRCMP_                    1
#define _USE_STRNCMP_                   1
#define _USE_STRSTR_                    1
#define _USE_STRLEN_                    1
#define _USE_MEMCPY_                    1
#define _USE_MEMMOVE_                   1
#define _USE_MEMCMP_                    1
#define _USE_MEMSET_                    1
#define _USE_ABS_                               1
#define _USE_RAND_                              1
#define _USE_SRAND_                             1
#define _USE_STRTOL_                    1
#define _USE_ATOI_                              1
#define _USE_ITOA_                              1
#define _USE_ISLOWER_                   1
#define _USE_ISUPPER_                   1
#define _USE_TOUPPER_                   1
#define _USE_TOLOWER_                   1
 
#endif