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user/libs/libc/string.c

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