Libraries: Create top level directory for libraries.

Things were getting a little crowded in the project root, so this patch
moves the Lib*/ directories into Libraries/.

Libraries/LibC/dirent.cpp

@@ -0,0 +1,94 @@
+#include <AK/Assertions.h>
+#include <AK/StdLibExtras.h>
+#include <Kernel/Syscall.h>
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+extern "C" {
+
+DIR* opendir(const char* name)
+{
+    int fd = open(name, O_RDONLY | O_DIRECTORY);
+    if (fd == -1)
+        return nullptr;
+    DIR* dirp = (DIR*)malloc(sizeof(DIR));
+    dirp->fd = fd;
+    dirp->buffer = nullptr;
+    dirp->buffer_size = 0;
+    dirp->nextptr = nullptr;
+    return dirp;
+}
+
+int closedir(DIR* dirp)
+{
+    if (!dirp || dirp->fd == -1)
+        return -EBADF;
+    if (dirp->buffer)
+        free(dirp->buffer);
+    int rc = close(dirp->fd);
+    if (rc == 0)
+        dirp->fd = -1;
+    free(dirp);
+    return rc;
+}
+
+struct [[gnu::packed]] sys_dirent
+{
+    ino_t ino;
+    u8 file_type;
+    size_t namelen;
+    char name[];
+    size_t total_size()
+    {
+        return sizeof(ino_t) + sizeof(u8) + sizeof(size_t) + sizeof(char) * namelen;
+    }
+};
+
+dirent* readdir(DIR* dirp)
+{
+    if (!dirp)
+        return nullptr;
+    if (dirp->fd == -1)
+        return nullptr;
+
+    if (!dirp->buffer) {
+        struct stat st;
+        int rc = fstat(dirp->fd, &st);
+        if (rc < 0)
+            return nullptr;
+        size_t size_to_allocate = max(st.st_size, 4096);
+        dirp->buffer = (char*)malloc(size_to_allocate);
+        ssize_t nread = syscall(SC_get_dir_entries, dirp->fd, dirp->buffer, size_to_allocate);
+        dirp->buffer_size = nread;
+        dirp->nextptr = dirp->buffer;
+    }
+
+    if (dirp->nextptr >= (dirp->buffer + dirp->buffer_size))
+        return nullptr;
+
+    auto* sys_ent = (sys_dirent*)dirp->nextptr;
+    dirp->cur_ent.d_ino = sys_ent->ino;
+    dirp->cur_ent.d_type = sys_ent->file_type;
+    dirp->cur_ent.d_off = 0;
+    dirp->cur_ent.d_reclen = sys_ent->total_size();
+    for (size_t i = 0; i < sys_ent->namelen; ++i)
+        dirp->cur_ent.d_name[i] = sys_ent->name[i];
+    // FIXME: I think this null termination behavior is not supposed to be here.
+    dirp->cur_ent.d_name[sys_ent->namelen] = '\0';
+
+    dirp->nextptr += sys_ent->total_size();
+    return &dirp->cur_ent;
+}
+
+int dirfd(DIR* dirp)
+{
+    ASSERT(dirp);
+    return dirp->fd;
+}
+}