libos: Add FileSystem::stat()

apps/ls.cpp

@@ -1,10 +1,59 @@
-#include <fcntl.h>
+#include <grp.h>
 #include <os/ArgumentParser.h>
 #include <os/Directory.h>
 #include <os/File.h>
 #include <os/FileSystem.h>
-#include <stdio.h>
-#include <sys/stat.h>
+#include <pwd.h>
+
+struct UsernameCache
+{
+    uid_t uid;
+    String name;
+};
+
+struct GroupCache
+{
+    gid_t gid;
+    String name;
+};
+
+Vector<UsernameCache> g_user_cache;
+Vector<GroupCache> g_group_cache;
+
+Result<void> find_user_and_group(struct stat& st, StringView& owner, StringView& group)
+{
+    for (const auto& user : g_user_cache)
+    {
+        if (user.uid == st.st_uid) owner = user.name.view();
+    }
+    if (owner.is_empty())
+    {
+        auto* pw = getpwuid(st.st_uid);
+        if (!pw) owner = "???";
+        else
+            owner = pw->pw_name;
+
+        auto name = TRY(String::from_string_view(owner));
+        TRY(g_user_cache.try_append({ st.st_uid, move(name) }));
+    }
+
+    for (const auto& grp : g_group_cache)
+    {
+        if (grp.gid == st.st_gid) group = grp.name.view();
+    }
+    if (group.is_empty())
+    {
+        auto* grp = getgrgid(st.st_gid);
+        if (!grp) group = "???";
+        else
+            group = grp->gr_name;
+
+        auto name = TRY(String::from_string_view(group));
+        TRY(g_group_cache.try_append({ st.st_gid, move(name) }));
+    }
+
+    return {};
+}
 
 Result<int> luna_main(int argc, char** argv)
 {
@@ -56,13 +105,14 @@ Result<int> luna_main(int argc, char** argv)
         for (const auto& file : files)
         {
             struct stat st;
-            if (fstatat(dirfd, file.chars(), &st, 0) < 0)
-            {
-                perror(file.chars());
-                return 1;
-            }
+            TRY(os::FileSystem::stat({ dirfd, file.view() }, st));
 
-            os::println("%6o %u %4u %4u %10lu %s", st.st_mode, st.st_nlink, st.st_uid, st.st_gid, st.st_size,
+            StringView owner;
+            StringView group;
+
+            TRY(find_user_and_group(st, owner, group));
+
+            os::println("%6o %u %4s %4s %10lu %s", st.st_mode, st.st_nlink, owner.chars(), group.chars(), st.st_size,
                         file.chars());
         }
     }

apps/stat.cpp

@@ -1,4 +1,5 @@
 #include <os/ArgumentParser.h>
+#include <os/FileSystem.h>
 #include <stdio.h>
 #include <sys/stat.h>
 
@@ -24,11 +25,7 @@ Result<int> luna_main(int argc, char** argv)
     parser.parse(argc, argv);
 
     struct stat st;
-    if (stat(path.chars(), &st) < 0)
-    {
-        perror("stat");
-        return 1;
-    }
+    TRY(os::FileSystem::stat(path, st));
 
     printf(" File: %s\n", path.chars());
     printf(" Size: %zu (%s)\n", st.st_size, file_type(st.st_mode));

libos/include/os/FileSystem.h

@@ -1,4 +1,5 @@
 #pragma once
+#include <bits/struct_stat.h>
 #include <luna/Result.h>
 #include <luna/StringView.h>
 #include <os/Path.h>
@@ -12,6 +13,8 @@ namespace os
 
         bool is_directory(const Path& path);
 
+        Result<void> stat(const Path& path, struct stat& st);
+
         Result<void> create_directory(StringView path, mode_t mode);
 
         Result<void> remove(const Path& path);

libos/src/FileSystem.cpp

@@ -1,3 +1,4 @@
+#include <bits/modes.h>
 #include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
@@ -6,7 +7,6 @@
 #include <os/FileSystem.h>
 #include <pwd.h>
 #include <stdlib.h>
-#include <sys/stat.h>
 #include <sys/syscall.h>
 #include <unistd.h>
 
@@ -16,7 +16,7 @@ namespace os::FileSystem
     {
         struct stat st;
 
-        if (fstatat(path.dirfd(), path.name().chars(), &st, path.is_empty_path()) < 0) return false;
+        if (stat(path, st).has_error()) return false;
 
         return true;
     }
@@ -25,11 +25,19 @@ namespace os::FileSystem
     {
         struct stat st;
 
-        if (fstatat(path.dirfd(), path.name().chars(), &st, path.is_empty_path()) < 0) return false;
+        if (stat(path, st).has_error()) return false;
 
         return S_ISDIR(st.st_mode);
     }
 
+    Result<void> stat(const Path& path, struct stat& st)
+    {
+        long rc =
+            syscall(SYS_fstatat, path.dirfd(), path.name().chars(), &st, path.is_empty_path() ? AT_EMPTY_PATH : 0);
+
+        return Result<void>::from_syscall(rc);
+    }
+
     Result<void> create_directory(StringView path, mode_t mode)
     {
         long rc = syscall(SYS_mkdir, path.chars(), mode);