Proper zig project organization

build.zig

@@ -0,0 +1,23 @@
+const std = @import("std");
+
+pub fn build(b: *std.Build) void {
+    const target = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{});
+    const lib_mod = b.createModule(.{
+        .root_source_file = b.path("src/root.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+    const lib = b.addLibrary(.{
+        .linkage = .static,
+        .name = "zig_squashfs",
+        .root_module = lib_mod,
+    });
+    b.installArtifact(lib);
+    const lib_unit_tests = b.addTest(.{
+        .root_module = lib_mod,
+    });
+    const run_lib_unit_tests = b.addRunArtifact(lib_unit_tests);
+    const test_step = b.step("test", "Run unit tests");
+    test_step.dependOn(&run_lib_unit_tests.step);
+}

build.zig.zon

@@ -0,0 +1,61 @@
+.{
+    .name = .zig_squashfs,
+    .version = "0.0.0",
+    .fingerprint = 0x527960c72c03ffe3, // Changing this has security and trust implications.
+
+    .minimum_zig_version = "0.14.0",
+
+    // This field is optional.
+    // Each dependency must either provide a `url` and `hash`, or a `path`.
+    // `zig build --fetch` can be used to fetch all dependencies of a package, recursively.
+    // Once all dependencies are fetched, `zig build` no longer requires
+    // internet connectivity.
+    .dependencies = .{
+        // See `zig fetch --save <url>` for a command-line interface for adding dependencies.
+        //.example = .{
+        //    // When updating this field to a new URL, be sure to delete the corresponding
+        //    // `hash`, otherwise you are communicating that you expect to find the old hash at
+        //    // the new URL. If the contents of a URL change this will result in a hash mismatch
+        //    // which will prevent zig from using it.
+        //    .url = "https://example.com/foo.tar.gz",
+        //
+        //    // This is computed from the file contents of the directory of files that is
+        //    // obtained after fetching `url` and applying the inclusion rules given by
+        //    // `paths`.
+        //    //
+        //    // This field is the source of truth; packages do not come from a `url`; they
+        //    // come from a `hash`. `url` is just one of many possible mirrors for how to
+        //    // obtain a package matching this `hash`.
+        //    //
+        //    // Uses the [multihash](https://multiformats.io/multihash/) format.
+        //    .hash = "...",
+        //
+        //    // When this is provided, the package is found in a directory relative to the
+        //    // build root. In this case the package's hash is irrelevant and therefore not
+        //    // computed. This field and `url` are mutually exclusive.
+        //    .path = "foo",
+        //
+        //    // When this is set to `true`, a package is declared to be lazily
+        //    // fetched. This makes the dependency only get fetched if it is
+        //    // actually used.
+        //    .lazy = false,
+        //},
+    },
+
+    // Specifies the set of files and directories that are included in this package.
+    // Only files and directories listed here are included in the `hash` that
+    // is computed for this package. Only files listed here will remain on disk
+    // when using the zig package manager. As a rule of thumb, one should list
+    // files required for compilation plus any license(s).
+    // Paths are relative to the build root. Use the empty string (`""`) to refer to
+    // the build root itself.
+    // A directory listed here means that all files within, recursively, are included.
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+        // For example...
+        //"LICENSE",
+        //"README.md",
+    },
+}

file.zig

@@ -1,14 +0,0 @@
-const inode = @import("inode.zig");
-const Reader = @import("squashfs.zig").Reader;
-const MetadataReader = @import("metadata_reader.zig").MetadataReader;
-
-pub const File = struct {
-    rdr: *Reader,
-    inode: inode.Inode,
-    name: []const u8,
-    dir_entries: []const void = undefined, //TODO
-
-    pub fn fromRef(ref: inode.InodeRef, rdr: *Reader) !File {
-        var meta_rdr: MetadataReader = .init(rdr.super.comp, rdr: io.AnyReader, alloc: std.mem.Allocator)
-    }
-};

file_offset_reader.zig

@@ -1,7 +0,0 @@
-const std = @import("std");
-
-const FileOffsetReader = struct {
-    file: std.fs.File,
-
-    pub fn any(self: *FileOffsetReader) !std.io.AnyReader {}
-};

src/directory.zig

@@ -0,0 +1,45 @@
+const std = @import("std");
+
+const DirHeader = packed struct {
+    count: u32,
+    inode_block_start: u32,
+    inode_num: u32,
+};
+
+const RawDirEntry = struct {
+    inode_offset: u16,
+    inode_num_difference: i16,
+    inode_type: u16,
+    name_size: u16,
+    name: []u8,
+
+    fn init(rdr: std.io.AnyReader, alloc: std.mem.Allocator) !DirEntry {
+        var out: DirEntry = .{
+            .inode_offset = try rdr.readInt(u16, std.builtin.Endian.little),
+            .inode_num_difference = try rdr.readInt(i16, std.builtin.Endian.little),
+            .inode_type = try rdr.readInt(u16, std.builtin.Endian.little),
+            .name_size = try rdr.readInt(u16, std.builtin.Endian.little),
+            .name = undefined,
+        };
+        out.name = try alloc.alloc(u8, out.name_size);
+        _ = try rdr.readAll(out.name);
+        return out;
+    }
+};
+
+pub const DirEntry = struct {
+    inode_offset: u16,
+    inode_block_start: u32,
+    inode_num: u32,
+    name: []u8,
+
+    fn init(raw: RawDirEntry, hdr: DirHeader) DirEntry {
+        return .{
+            .inode_offset = raw.inode_offset,
+            .inode_block_start = hdr.inode_block_start,
+            .inode_num = hdr.inode_num - raw.inode_num_difference,
+            .name = raw.name,
+        };
+    }
+};
+

src/file.zig

@@ -0,0 +1,23 @@
+const inode = @import("inode.zig");
+const Reader = @import("squashfs.zig").Reader;
+const MetadataReader = @import("metadata_reader.zig").MetadataReader;
+const FileOffsetReader = @import("file_offset_reader.zig").FileOffsetReader;
+
+pub const File = struct {
+    rdr: *Reader,
+    inode: inode.Inode,
+    name: []const u8,
+    dir_entries: []const void = undefined, //TODO
+
+    pub fn fromRef(ref: inode.InodeRef, name: []const u8, rdr: *Reader) !File {
+        var offset_rdr: FileOffsetReader = .init(rdr.file, rdr.super.inode_table + ref.block_start);
+        var meta_rdr: MetadataReader = .init(rdr.super.comp, offset_rdr.any(), rdr.alloc.allocator());
+        try meta_rdr.skip(ref.offset);
+        const in = try inode.readInode(meta_rdr, rdr.super.block_size, rdr.alloc.allocator());
+        return .{
+            .rdr = rdr,
+            .inode = in,
+            .name = name,
+        };
+    }
+};

src/file_offset_reader.zig

@@ -0,0 +1,31 @@
+const std = @import("std");
+
+pub const FileOffsetReader = struct {
+    file: std.fs.File,
+    offset: u64,
+
+    pub fn init(file: std.fs.File, initial_offset: u64) FileOffsetReader {
+        return .{
+            .file = file,
+            .offset = initial_offset,
+        };
+    }
+
+    pub fn read(self: *FileOffsetReader, bytes: []u8) anyerror!usize {
+        const red = try self.file.preadAll(bytes, self.offset);
+        self.offset += @intCast(red);
+        return red;
+    }
+
+    pub fn any(self: *FileOffsetReader) std.io.AnyReader {
+        return .{
+            .context = @ptrCast(self),
+            .readFn = readOpaque,
+        };
+    }
+
+    fn readOpaque(context: *const anyopaque, buf: []u8) anyerror!usize {
+        var self: *FileOffsetReader = @constCast(@ptrCast(@alignCast(context)));
+        return self.read(buf);
+    }
+};

src/squashfs.zig

@@ -5,6 +5,7 @@ const Superblock = @import("superblock.zig").Superblock;
 const inode = @import("inode.zig");
 const MetadataReader = @import("metadata_reader.zig").MetadataReader;
 const File = @import("file.zig").File;
+const FileOffsetReader = @import("file_offset_reader.zig").FileOffsetReader;
 
 pub const Reader = struct {
     super: Superblock,
@@ -25,15 +26,24 @@ pub fn newReader(filename: []const u8) !Reader {
     errdefer _ = alloc.deinit();
     const super = try file.reader().readStruct(Superblock);
     try super.valid();
-    try file.seekTo(super.inode_table + super.root_inode.block_start);
-    var root_reader: MetadataReader = try .init(super.comp, file.reader().any(), alloc.allocator());
+    var offset_rdr: FileOffsetReader = .init(file, super.inode_table + super.root_inode.block_start);
+    var root_reader: MetadataReader = try .init(
+        super.comp,
+        offset_rdr.any(),
+        alloc.allocator(),
+    );
     defer root_reader.deinit();
     try root_reader.skip(super.root_inode.offset);
-    const root_inode = try inode.readInode(root_reader.any(), super.block_size, alloc.allocator());
-    return Reader{
+    var out: Reader = undefined;
+    out = Reader{
         .super = super,
         .rdr = file,
-        .root = root_inode,
+        .root = .{
+            .inode = try inode.readInode(root_reader.any(), super.block_size, alloc.allocator()),
+            .name = "",
+            .rdr = &out,
+        },
         .alloc = alloc,
     };
+    return out;
 }