Move string functions/utils from HAL to std/string

kernel/std/string.c

@@ -1,39 +1,151 @@
 #include <stddef.h>
-#include "hal/hal.h"
+#include <stdint.h>
 
 void *memset(void *p, int c, size_t n) {
-  return hal_memset(p,c,n);
+  char *cp = p;
+  for (size_t i = 0; i < n; i++) cp[i] = c;
+  return p;
 }
 
 void *memcpy(void *dst, const void *src, size_t n) {
-  return hal_memcpy(dst,src,n);
+  char *a = dst;
+  const char *b = src;
+  for (size_t i = 0; i < n; i++) a[i] = b[i];
+  return dst;
 }
 
 size_t strlen(char *s) {
-  return hal_strlen(s);
+  char *s2;
+  for (s2 = s; *s2; ++s2);
+  return (s2 - s);
+}
+
+// https://aticleworld.com/memcmp-in-c/
+int memcmp(const void *s1, const void *s2, int len)
+{
+    unsigned char *p = (unsigned char *)s1;
+    unsigned char *q = (unsigned char *)s2;
+    int charCompareStatus = 0;
+    //If both pointer pointing same memory block
+    if (s1 == s2)
+    {
+        return charCompareStatus;
+    }
+    while (len > 0)
+    {
+        if (*p != *q)
+        {  //compare the mismatching character
+            charCompareStatus = (*p >*q)?1:-1;
+            break;
+        }
+        len--;
+        p++;
+        q++;
+    }
+    return charCompareStatus;
 }
 
 int strcmp(const char *a, const char *b) {
-  return hal_strcmp(a, b);
+  while (*a && (*a == *b)) {
+    a++, b++;
+  }
+  return (unsigned char)*a - (unsigned char)*b;
 }
 
 size_t strcspn(const char *s, const char *reject) {
-  return hal_strcspn(s, reject);
+    size_t count = 0;
+    for (; *s != '\0'; ++s) {
+        const char *r = reject;
+        while (*r != '\0') {
+            if (*s == *r) {
+                return count;
+            }
+            r++;
+        }
+        count++;
+    }
+    return count;
 }
 
 size_t strspn(const char *s, const char *accept) {
-  return hal_strspn(s, accept);
+    size_t count = 0;
+    for (; *s != '\0'; ++s) {
+        const char *a = accept;
+        int matched = 0;
+        while (*a != '\0') {
+            if (*s == *a) {
+                matched = 1;
+                break;
+            }
+            a++;
+        }
+        if (!matched) {
+            return count;
+        }
+        count++;
+    }
+    return count;
 }
 
-
 char *strcpy(char *dest, const char *src) {
-  return hal_strcpy(dest, src);
+    char *d = dest;
+    while ((*d++ = *src++) != '\0') {
+        ;
+    }
+    return dest;
 }
 
 char *strchr(const char *s, int c) {
-  return hal_strchr(s, c);
+    char ch = (char)c;
+    while (*s != '\0') {
+        if (*s == ch) {
+            return (char *)s;
+        }
+        s++;
+    }
+    if (ch == '\0') {
+        return (char *)s;
+    }
+    return NULL;
 }
 
-int memcmp(const void *s1, const void *s2, int len) {
-  return hal_memcmp(s1, s2, len);
+char *strstr(const char *str, const char *substring)
+{
+    const char *a;
+    const char *b;
+
+    b = substring;
+
+    if (*b == 0) {
+        return (char *) str;
+    }
+
+    for ( ; *str != 0; str += 1) {
+        if (*str != *b) {
+            continue;
+        }
+
+        a = str;
+        while (1) {
+            if (*b == 0) {
+                return (char *) str;
+            }
+            if (*a++ != *b++) {
+                break;
+            }
+        }
+        b = substring;
+    }
+
+    return NULL;
+}
+
+char *strcat(char *dest, const char *src) {
+  size_t i, j;
+  for(i = 0; dest[i] != '\0'; i++);
+  for(j = 0; src[j] != '\0'; j++) {
+    dest[i+j] = src[j];
+  }
+  dest[i+j] = '\0';
+  return dest;
 }

kernel/std/string.h

@@ -12,5 +12,7 @@ size_t strspn(const char *s, const char *accept);
 char *strcpy(char *dest, const char *src);
 char *strchr(const char *s, int c);
 int memcmp(const void *s1, const void *s2, int len);
+char *strstr(const char *str, const char *substring);
+char *strcat(char *dest, const char *src);
 
 #endif // STD_STRING_H_