Open new log file after every fork() where necessary

Signed-off-by: AnErrupTion <anerruption@disroot.org>

src/LogFile.zig

@@ -0,0 +1,51 @@
+const std = @import("std");
+
+const LogFile = @This();
+
+path: []const u8,
+could_open_log_file: bool = undefined,
+file: std.fs.File = undefined,
+buffer: []u8,
+file_writer: std.fs.File.Writer = undefined,
+
+pub fn init(path: []const u8, buffer: []u8) !LogFile {
+    var log_file = LogFile{ .path = path, .buffer = buffer };
+    log_file.could_open_log_file = try openLogFile(path, &log_file);
+    return log_file;
+}
+
+pub fn reinit(self: *LogFile) !void {
+    self.could_open_log_file = try openLogFile(self.path, self);
+}
+
+pub fn deinit(self: *LogFile) void {
+    self.file_writer.interface.flush() catch {};
+    self.file.close();
+}
+
+fn openLogFile(path: []const u8, log_file: *LogFile) !bool {
+    var could_open_log_file = true;
+    open_log_file: {
+        log_file.file = std.fs.cwd().openFile(path, .{ .mode = .write_only }) catch std.fs.cwd().createFile(path, .{ .mode = 0o666 }) catch {
+            // If we could neither open an existing log file nor create a new
+            // one, abort.
+            could_open_log_file = false;
+            break :open_log_file;
+        };
+    }
+
+    if (!could_open_log_file) {
+        log_file.file = try std.fs.openFileAbsolute("/dev/null", .{ .mode = .write_only });
+    }
+
+    var log_file_writer = log_file.file.writer(log_file.buffer);
+
+    // Seek to the end of the log file
+    if (could_open_log_file) {
+        const stat = try log_file.file.stat();
+        try log_file_writer.seekTo(stat.size);
+    }
+
+    log_file.file_writer = log_file_writer;
+    return could_open_log_file;
+}