Kernel: Copy strrchr, dirname and basename over from libc

kernel/include/std/libgen.h

@@ -0,0 +1,4 @@
+#pragma once
+
+char* basename(char* path);
+char* dirname(char* path);

kernel/include/std/string.h

@@ -20,3 +20,4 @@ int memcmp(const void* a, const void* b, size_t n);
 void* memmove(void* dest, void* src, size_t n);
 
 char* strdup(const char* src);
+char* strrchr(const char* str, int c);

kernel/src/std/libgen.cpp

@@ -0,0 +1,47 @@
+#include "std/libgen.h"
+#include "std/string.h"
+
+static char dot[] = ".";
+
+char* basename(char* path)
+{
+    // If path is NULL, or the string's length is 0, return .
+    if (!path) return dot;
+    size_t len = strlen(path);
+    if (!len) return dot;
+
+    // Strip trailing slashes.
+    char* it = path + len - 1;
+    while (*it == '/' && it != path) { it--; }
+    *(it + 1) = 0;
+    if (it == path) return path;
+
+    // Return path from the first character if there are no more slashes, or from the first character after the last
+    // slash.
+    char* beg = strrchr(path, '/');
+    if (!beg) return path;
+    return beg + 1;
+}
+
+char* dirname(char* path)
+{
+    // If path is NULL, or the string's length is 0, return .
+    if (!path) return dot;
+    size_t len = strlen(path);
+    if (!len) return dot;
+
+    // Strip trailing slashes.
+    char* it = path + len - 1;
+    while (*it == '/' && it != path) { it--; }
+    *(char*)(it + 1) = 0;
+    if (it == path) return path;
+
+    // Search for the last slash. If there is none, return .
+    // Otherwise, we end the string there and return.
+    char* end = strrchr(path, '/');
+    if (!end) return dot;
+    if (end != path) *end = 0;
+    else
+        *(end + 1) = 0;
+    return path;
+}

kernel/src/std/string.cpp

@@ -149,3 +149,11 @@ char* strdup(const char* src)
     memcpy(duplicated, src, length + 1);
     return duplicated;
 }
+
+char* strrchr(const char* str, int c)
+{
+    const char* s = str + strlen(str);
+    while (s != str && *s != (char)c) s--;
+    if (*s == (char)c) return const_cast<char*>(s);
+    return NULL;
+}