1 files changed, 185 insertions, 0 deletions
diff --git a/Userland/Libraries/LibCore/File.cpp b/Userland/Libraries/LibCore/File.cpp
new file mode 100644
index 0000000000..d9eba43da0
--- /dev/null
+++ b/Userland/Libraries/LibCore/File.cpp
@@ -0,0 +1,185 @@
+/*
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021, sin-ack <sin-ack@protonmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibCore/File.h>
+#include <LibCore/System.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+namespace Core {
+
+ErrorOr<NonnullOwnPtr<File>> File::open(StringView filename, OpenMode mode, mode_t permissions)
+{
+    auto file = TRY(adopt_nonnull_own_or_enomem(new (nothrow) File(mode)));
+    TRY(file->open_path(filename, permissions));
+    return file;
+}
+
+ErrorOr<NonnullOwnPtr<File>> File::adopt_fd(int fd, OpenMode mode, ShouldCloseFileDescriptor should_close_file_descriptor)
+{
+    if (fd < 0) {
+        return Error::from_errno(EBADF);
+    }
+
+    if (!has_any_flag(mode, OpenMode::ReadWrite)) {
+        dbgln("Core::File::adopt_fd: Attempting to adopt a file with neither Read nor Write specified in mode");
+        return Error::from_errno(EINVAL);
+    }
+
+    auto file = TRY(adopt_nonnull_own_or_enomem(new (nothrow) File(mode, should_close_file_descriptor)));
+    file->m_fd = fd;
+    return file;
+}
+
+ErrorOr<NonnullOwnPtr<File>> File::standard_input()
+{
+    return File::adopt_fd(STDIN_FILENO, OpenMode::Read, ShouldCloseFileDescriptor::No);
+}
+ErrorOr<NonnullOwnPtr<File>> File::standard_output()
+{
+    return File::adopt_fd(STDOUT_FILENO, OpenMode::Write, ShouldCloseFileDescriptor::No);
+}
+ErrorOr<NonnullOwnPtr<File>> File::standard_error()
+{
+    return File::adopt_fd(STDERR_FILENO, OpenMode::Write, ShouldCloseFileDescriptor::No);
+}
+
+ErrorOr<NonnullOwnPtr<File>> File::open_file_or_standard_stream(StringView filename, OpenMode mode)
+{
+    if (!filename.is_empty() && filename != "-"sv)
+        return File::open(filename, mode);
+
+    switch (mode) {
+    case OpenMode::Read:
+        return standard_input();
+    case OpenMode::Write:
+        return standard_output();
+    default:
+        VERIFY_NOT_REACHED();
+    }
+}
+
+int File::open_mode_to_options(OpenMode mode)
+{
+    int flags = 0;
+    if (has_flag(mode, OpenMode::ReadWrite)) {
+        flags |= O_RDWR | O_CREAT;
+    } else if (has_flag(mode, OpenMode::Read)) {
+        flags |= O_RDONLY;
+    } else if (has_flag(mode, OpenMode::Write)) {
+        flags |= O_WRONLY | O_CREAT;
+        bool should_truncate = !has_any_flag(mode, OpenMode::Append | OpenMode::MustBeNew);
+        if (should_truncate)
+            flags |= O_TRUNC;
+    }
+
+    if (has_flag(mode, OpenMode::Append))
+        flags |= O_APPEND;
+    if (has_flag(mode, OpenMode::Truncate))
+        flags |= O_TRUNC;
+    if (has_flag(mode, OpenMode::MustBeNew))
+        flags |= O_EXCL;
+    if (!has_flag(mode, OpenMode::KeepOnExec))
+        flags |= O_CLOEXEC;
+    if (!has_flag(mode, OpenMode::Nonblocking))
+        flags |= O_NONBLOCK;
+    return flags;
+}
+
+ErrorOr<void> File::open_path(StringView filename, mode_t permissions)
+{
+    VERIFY(m_fd == -1);
+    auto flags = open_mode_to_options(m_mode);
+
+    m_fd = TRY(System::open(filename, flags, permissions));
+    return {};
+}
+
+ErrorOr<Bytes> File::read(Bytes buffer)
+{
+    if (!has_flag(m_mode, OpenMode::Read)) {
+        // NOTE: POSIX says that if the fd is not open for reading, the call
+        //       will return EBADF. Since we already know whether we can or
+        //       can't read the file, let's avoid a syscall.
+        return Error::from_errno(EBADF);
+    }
+
+    ssize_t nread = TRY(System::read(m_fd, buffer));
+    m_last_read_was_eof = nread == 0;
+    return buffer.trim(nread);
+}
+
+ErrorOr<ByteBuffer> File::read_until_eof(size_t block_size)
+{
+    // Note: This is used as a heuristic, it's not valid for devices or virtual files.
+    auto const potential_file_size = TRY(System::fstat(m_fd)).st_size;
+
+    return read_until_eof_impl(block_size, potential_file_size);
+}
+
+ErrorOr<size_t> File::write(ReadonlyBytes buffer)
+{
+    if (!has_flag(m_mode, OpenMode::Write)) {
+        // NOTE: Same deal as Read.
+        return Error::from_errno(EBADF);
+    }
+
+    return TRY(System::write(m_fd, buffer));
+}
+
+bool File::is_eof() const { return m_last_read_was_eof; }
+bool File::is_open() const { return m_fd >= 0; }
+
+void File::close()
+{
+    if (!is_open()) {
+        return;
+    }
+
+    // NOTE: The closing of the file can be interrupted by a signal, in which
+    // case EINTR will be returned by the close syscall. So let's try closing
+    // the file until we aren't interrupted by rude signals. :^)
+    ErrorOr<void> result;
+    do {
+        result = System::close(m_fd);
+    } while (result.is_error() && result.error().code() == EINTR);
+
+    VERIFY(!result.is_error());
+    m_fd = -1;
+}
+
+ErrorOr<size_t> File::seek(i64 offset, SeekMode mode)
+{
+    int syscall_mode;
+    switch (mode) {
+    case SeekMode::SetPosition:
+        syscall_mode = SEEK_SET;
+        break;
+    case SeekMode::FromCurrentPosition:
+        syscall_mode = SEEK_CUR;
+        break;
+    case SeekMode::FromEndPosition:
+        syscall_mode = SEEK_END;
+        break;
+    default:
+        VERIFY_NOT_REACHED();
+    }
+
+    size_t seek_result = TRY(System::lseek(m_fd, offset, syscall_mode));
+    m_last_read_was_eof = false;
+    return seek_result;
+}
+
+ErrorOr<void> File::truncate(size_t length)
+{
+    if (length > static_cast<size_t>(NumericLimits<off_t>::max()))
+        return Error::from_string_literal("Length is larger than the maximum supported length");
+
+    return System::ftruncate(m_fd, length);
+}
+
+}