109 lines
2.9 KiB
C
109 lines
2.9 KiB
C
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#include "string.h"
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size_t strlen(const char *s)
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{
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register int __res = 0;
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while (s[__res] != '\0')
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{
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++__res;
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}
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return __res;
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}
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int strcmp(const char *FirstPart, const char *SecondPart)
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{
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register int __res;
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__asm__ __volatile__("cld \n\t"
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"1: \n\t"
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"lodsb \n\t"
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"scasb \n\t"
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"jne 2f \n\t"
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"testb %%al, %%al \n\t"
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"jne 1b \n\t"
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"xorl %%eax, %%eax \n\t"
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"jmp 3f \n\t"
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"2: \n\t"
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"movl $1, %%eax \n\t"
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"jl 3f \n\t"
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"negl %%eax \n\t"
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"3: \n\t"
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: "=a"(__res)
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: "D"(FirstPart), "S"(SecondPart)
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:);
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return __res;
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}
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void *memset(void *dst, unsigned char C, uint64_t size)
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{
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int d0, d1;
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unsigned long tmp = C * 0x0101010101010101UL;
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__asm__ __volatile__("cld \n\t"
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"rep \n\t"
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"stosq \n\t"
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"testb $4, %b3 \n\t"
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"je 1f \n\t"
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"stosl \n\t"
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"1:\ttestb $2, %b3 \n\t"
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"je 2f\n\t"
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"stosw \n\t"
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"2:\ttestb $1, %b3 \n\t"
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"je 3f \n\t"
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"stosb \n\t"
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"3: \n\t"
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: "=&c"(d0), "=&D"(d1)
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: "a"(tmp), "q"(size), "0"(size / 8), "1"(dst)
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: "memory");
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return dst;
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}
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/**
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* @brief 拷贝指定字节数的字符串
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*
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* @param dst 目标地址
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* @param src 源字符串
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* @param Count 字节数
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* @return char*
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*/
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char *strncpy(char *dst, char *src, long Count)
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{
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__asm__ __volatile__("cld \n\t"
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"1: \n\t"
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"decq %2 \n\t"
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"js 2f \n\t"
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"lodsb \n\t"
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"stosb \n\t"
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"testb %%al, %%al \n\t"
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"jne 1b \n\t"
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"rep \n\t"
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"stosb \n\t"
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"2: \n\t"
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:
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: "S"(src), "D"(dst), "c"(Count)
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: "ax", "memory");
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return dst;
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}
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/**
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* @brief 拼接两个字符串（将src接到dest末尾）
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*
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* @param dest 目标串
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* @param src 源串
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* @return char*
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*/
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char *strcat(char *dest, const char *src)
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{
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unsigned int dest_size = strlen(dest);
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unsigned int src_size = strlen(src);
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char *d = dest;
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for (size_t i = 0; i < src_size; i++)
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{
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d[dest_size + i] = src[i];
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}
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d[dest_size + src_size] = '\0';
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return dest;
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}
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