More work on extraction, especially for regular files

src/util/offset_file.zig

@@ -1,7 +1,8 @@
 //! A File where it's meaningful (to us) content starts at a given offset.
 
 const std = @import("std");
-const File = std.Io.File;
+const Io = std.Io;
+const File = Io.File;
 const Reader = File.Reader;
 
 const OffsetFile = @This();
@@ -13,8 +14,16 @@ pub fn init(fil: File, init_offset: u64) OffsetFile {
     return .{ .fil = fil, .offset = init_offset };
 }
 
-pub fn readerAt(self: OffsetFile, io: std.Io, offset: u64, buffer: []u8) !Reader {
+pub fn readerAt(self: OffsetFile, io: Io, offset: u64, buffer: []u8) !Reader {
     var rdr = self.fil.reader(io, buffer);
     try rdr.seekTo(self.offset + offset);
     return rdr;
 }
+pub fn readAt(self: OffsetFile, io: Io, offset: u64, buf: []u8) !void {
+    _ = try self.fil.readPositionalAll(io, buf, self.offset + offset);
+}
+pub fn readValueAt(self: OffsetFile, comptime T: anytype, io: Io, offset: u64) !void {
+    //TODO: check for endianess and decode accordingly.
+    var new: T = undefined;
+    _ = try self.fil.readPositionalAll(io, @ptrCast(&new), self.offset + offset);
+}