Re-adding stuff

src/archive.zig

@@ -5,12 +5,56 @@ const Archive = @This();
 
 map: Io.File.MemoryMap,
 
+super: Superblock,
+
 pub fn open(io: Io, file: Io.File, offset: u64) !Archive {
-    return .{
-        .map = try file.createMemoryMap(io, .{
-            .len = super.size,
+    var map = try file.createMemoryMap(io, .{
+        .len = try file.length(io) - offset,
         .offset = offset,
         .protection = .{ .read = true },
-        }),
+    });
+
+    var super: Superblock = std.mem.bytesToValue(Superblock, map.memory[0..@sizeOf(Superblock)]);
+    try super.check();
+
+    return .{
+        .map = map,
+
+        .super = super,
     };
 }
+
+// Superblock
+
+pub const Superblock = extern struct {
+    pub const MAGIC: u32 = 0x73717368;
+
+    magic: u32,
+    inode_count: u32,
+    mod_time: u32,
+    block_size: u32,
+    frag_count: u32,
+    compression: u16,
+    block_log: u16,
+    flags: u16, // TODO: break out into packed struct.
+    id_count: u16,
+    version_major: u16,
+    version_minor: u16,
+    root_inode_ref: u64, // TODO: Change to inode reference packed struct.
+    size: u64,
+    id_table_start: u64,
+    xattr_table_start: u64,
+    inode_table_start: u64,
+    dir_table_start: u64,
+    frag_table_start: u64,
+    export_table_start: u64,
+
+    fn check(self: Superblock) !void {
+        if (self.magic != MAGIC)
+            return error.InvalidMagic;
+        if (self.version_major != 4 or self.version_minor != 0)
+            return error.IncompatibleVersion;
+        if (std.math.log2(self.block_size) != self.block_log)
+            return error.BadBlockLog;
+    }
+};

src/inode.zig

@@ -0,0 +1,89 @@
+const std = @import("std");
+const Io = std.Io;
+
+const Inode = @This();
+
+header: Header,
+data: Data,
+
+// Types
+
+pub const Reference = packed struct(u64) {
+    _: u16,
+    block: u32,
+    offset: u16,
+};
+
+pub const Type = enum(u16) {
+    dir,
+    file,
+    symlink,
+    block_dev,
+    char_dev,
+    fifo,
+    socket,
+    ext_dir,
+    ext_file,
+    ext_symlink,
+    ext_block_dev,
+    ext_char_dev,
+    ext_fifo,
+    ext_socket,
+};
+
+pub const Header = extern struct {
+    type: Type, // TODO: enum
+    permission: u16,
+    uid_idx: u16,
+    gid_idx: u16,
+    mod_time: u32,
+    inode_num: u32,
+};
+
+pub const Data = union(Type) {
+    dir: Dir,
+    file: File,
+    symlink: Symlink,
+    block_dev: Dev,
+    char_dev: Dev,
+    fifo: Fifo,
+    socket: Fifo,
+    ext_dir: ExtDir,
+    ext_file: ExtFile,
+    ext_symlink: ExtSymlink,
+    ext_block_dev: ExtDev,
+    ext_char_dev: ExtDev,
+    ext_fifo: ExtFifo,
+    ext_socket: ExtFifo,
+};
+
+// Inode data types
+
+pub const Dir = extern struct {
+    block: u32,
+    hard_links: u32,
+    size: u16,
+    offset: u16,
+    parent_inode_num: u32,
+};
+pub const ExtDir = extern struct {
+    hard_links: u32,
+    size: u32,
+    block: u32,
+    parent_inode_num: u32,
+    idx_count: u16,
+    offset: u16,
+    xattr_idx: u32,
+};
+
+pub const File = struct {};
+pub const ExtFile = struct {};
+
+pub const Symlink = struct {};
+pub const ExtSymlink = struct {};
+
+pub const Dev = extern struct {};
+pub const ExtDev = extern struct {};
+
+pub const Fifo = extern struct {};
+pub const ExtFifo = extern struct {};