libos: Add a very bare-bones C++ RAII File class

apps/edit.cpp

@@ -1,4 +1,5 @@
 #include <os/ArgumentParser.h>
+#include <os/File.h>
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -6,19 +7,13 @@
 
 int main(int argc, char** argv)
 {
-    FILE* f;
     StringView pathname;
 
     os::ArgumentParser parser;
-    parser.add_positional_argument(pathname, "file"_sv, true);
+    parser.add_positional_argument(pathname, "path"_sv, true);
     parser.parse(argc, argv);
 
-    f = fopen(pathname.chars(), "w");
+    auto file = os::File::open_or_create(pathname, os::File::WriteOnly).release_value();
-    if (!f)
-    {
-        perror(pathname.chars());
-        return 1;
-    }
 
     char buffer[4096];
 
@@ -26,10 +21,8 @@ int main(int argc, char** argv)
     {
         char* rc = fgets(buffer, sizeof(buffer), stdin);
         if (rc == 0) break;
-        fputs(buffer, f);
+        file->write(StringView { buffer });
     }
 
-    fclose(f);
-
     return 0;
 }

libos/CMakeLists.txt

@@ -5,6 +5,7 @@ file(GLOB HEADERS include/os/*.h)
 set(SOURCES
     ${HEADERS}
     src/ArgumentParser.cpp
+    src/File.cpp
 )
 
 add_library(os ${SOURCES})

libos/include/os/File.h

@@ -0,0 +1,42 @@
+#pragma once
+#include <bits/open-flags.h>
+#include <luna/Buffer.h>
+#include <luna/Result.h>
+#include <luna/SharedPtr.h>
+#include <luna/StringView.h>
+#include <sys/types.h>
+
+namespace os
+{
+    class File
+    {
+      public:
+        enum OpenMode
+        {
+            ReadOnly = O_RDONLY,
+            WriteOnly = O_WRONLY | O_TRUNC,
+            ReadWrite = O_RDWR | O_TRUNC,
+            Append = O_WRONLY | O_APPEND,
+            ReadAppend = O_RDWR | O_APPEND,
+        };
+
+        static Result<SharedPtr<File>> open(StringView path, OpenMode flags);
+        static Result<SharedPtr<File>> open_or_create(StringView path, OpenMode flags, mode_t mode = 0644);
+        static Result<SharedPtr<File>> create(StringView path, OpenMode flags, mode_t mode = 0644);
+
+        void set_close_on_exec();
+
+        Result<void> write(StringView str);
+
+        File(Badge<File>);
+        ~File();
+
+      private:
+        static Result<SharedPtr<File>> construct(StringView path, int flags, mode_t mode);
+
+        Result<usize> raw_read(u8* buf, usize length);
+        Result<usize> raw_write(const u8* buf, usize length);
+
+        int m_fd { -1 };
+    };
+}

libos/src/File.cpp

@@ -0,0 +1,67 @@
+#include <fcntl.h>
+#include <os/File.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+namespace os
+{
+    File::File(Badge<File>)
+    {
+    }
+
+    File::~File()
+    {
+        if (m_fd >= 0) close(m_fd);
+    }
+
+    Result<SharedPtr<File>> File::construct(StringView path, int flags, mode_t mode)
+    {
+        auto file = TRY(adopt_shared(new (std::nothrow) File({})));
+
+        long rc = syscall(SYS_open, path.chars(), flags, mode);
+        int fd = TRY(Result<int>::from_syscall(rc));
+
+        file->m_fd = fd;
+
+        return file;
+    }
+
+    Result<SharedPtr<File>> File::open(StringView path, OpenMode flags)
+    {
+        return construct(path, (int)flags, 0);
+    }
+
+    Result<SharedPtr<File>> File::open_or_create(StringView path, OpenMode flags, mode_t mode)
+    {
+        return construct(path, (int)flags | O_CREAT, mode);
+    }
+
+    Result<SharedPtr<File>> File::create(StringView path, OpenMode flags, mode_t mode)
+    {
+        return construct(path, (int)flags | (O_CREAT | O_EXCL), mode);
+    }
+
+    Result<usize> File::raw_read(u8* buf, usize length)
+    {
+        long rc = syscall(SYS_read, m_fd, buf, length);
+        return Result<usize>::from_syscall(rc);
+    }
+
+    Result<usize> File::raw_write(const u8* buf, usize length)
+    {
+        long rc = syscall(SYS_write, m_fd, buf, length);
+        return Result<usize>::from_syscall(rc);
+    }
+
+    Result<void> File::write(StringView str)
+    {
+        TRY(raw_write((const u8*)str.chars(), str.length()));
+
+        return {};
+    }
+
+    void File::set_close_on_exec()
+    {
+        fcntl(m_fd, F_SETFD, FD_CLOEXEC);
+    }
+}