feat: some extensions to kernel standard c library. Other minor

improvements and formats

kernel/libc/string.c

@@ -4,6 +4,7 @@
 
 #include <string.h>
 #include <sys/param.h>
+#include <sys/types.h>
 
 int memcpy(void *dst, const void *src, size_t amount) {
     for (size_t i = 0; i < amount; i++) {
@@ -24,6 +25,10 @@ int strcpy(char *dst, const char *src) {
     return memcpy(dst, src, strlen(src) + 1);
 }
 
+int strncpy(char *dst, const char *src, size_t n) {
+    return memcpy(dst, src, MIN(strlen(src), n) + 1);
+}
+
 size_t strlen(const char *str) {
     int length = 0;
     while (str[length] != 0) {
@@ -51,6 +56,17 @@ const char *strchr(const char *s, char c) {
     }
 }
 
+int memcmp(const void *s1, const void *s2, size_t n) {
+    uint8_t a, b;
+    for (size_t i = 0; i < n; ++i) {
+        a = ((uint8_t *) s1)[i];
+        b = ((uint8_t *) s2)[i];
+        if (a > b) return 1;
+        if (b < a) return -1;
+    }
+    return 0;
+}
+
 int strncmp(const char *s1, const char *s2, int n) {
     for (int i = 0; i < n; ++i) {
         if (s1[i] == 0 && s2[i] == 0) {
@@ -71,3 +87,21 @@ int strncmp(const char *s1, const char *s2, int n) {
     }
     return 0;
 }
+
+char *strcat(char *dest, const char *src) {
+    size_t count = strlen(src);
+    return strncat(dest, src, count);
+}
+
+char *strncat(char *dest, const char *src, size_t n) {
+    size_t start = strlen(dest);
+    for (size_t index = 0; index < n; index++) {
+        char val = src[index];
+        dest[start + index] = val;
+        if (val == 0) {
+            dest[start + index] = 0;
+            break;
+        }
+    }
+    return dest;
+}