Split archive-specific logic into own module

src/oar.zig

@@ -1,29 +1,16 @@
 const std = @import("std");
 const sys = @import("./sys.zig");
+const table = @import("./table.zig");
 
 ///
-/// An entry block of an Oar archive file.
 ///
-/// Typically, following this block in memory is the file data it holds the meta-information for.
 ///
-pub const Entry = extern struct {
-    signature: [3]u8 = signature_magic,
-    revision: u8,
-    name_buffer: [255]u8 = std.mem.zeroes([255]u8),
-    name_length: u8 = 0,
-    file_size: u64,
-    file_offset: u64,
-    padding: [232]u8 = std.mem.zeroes([232]u8),
-
-    comptime {
-        const entry_size = @sizeOf(Entry);
-
-        if (entry_size != 512)
-            @compileError("Entry is " ++ std.fmt.comptimePrint("{d}", .{entry_size}) ++ " bytes");
-    }
+pub const Archive = struct {
+    file_access: sys.FileAccess,
+    index_cache: IndexCache,
 
     ///
-    /// [FindError.EntryNotFound] happens when an entry could not be found.
+    /// [OpenError.EntryNotFound] happens when an entry could not be found.
     ///
     pub const FindError = sys.FileAccess.Error || error {
         EntryNotFound,
@@ -32,15 +19,110 @@ pub const Entry = extern struct {
     ///
     ///
     ///
-    pub fn find(file_access: sys.FileAccess, entry_name: []const u8) FindError!Entry {
-        _ = file_access;
-        _ = entry_name;
+    pub const InitError = std.mem.Allocator.Error;
 
-        return error.EntryNotFound;
+    ///
+    ///
+    ///
+    const IndexCache = table.Hashed([]const u8, Entry.Header, table.string_context);
+
+    ///
+    /// Finds an entry matching `entry_path` in `archive`.
+    ///
+    /// The found [Entry] value is returned or a [FindError] if it failed to be found.
+    ///
+    pub fn find(archive: *Archive, entry_path: []const u8) FindError!Entry {
+        return Entry{
+            .header = find_header: {
+                if (archive.index_cache.lookup(entry_path)) |entry_header|
+                    break: find_header entry_header.*;
+
+                // Start from beginning of archive.
+                try archive.file_access.seek(0);
+
+                var entry_header = Entry.Header{
+                    .revision = 0,
+                    .file_size = 0,
+                    .file_offset = 0
+                };
+
+                const read_buffer = std.mem.asBytes(&entry_header);
+
+                // Read first entry.
+                while ((try archive.file_access.read(read_buffer)) == @sizeOf(Entry.Header)) {
+                    if (std.mem.eql(u8, entry_path, entry_header.
+                        name_buffer[0 .. entry_header.name_length])) {
+
+                        // If caching fails... oh well...
+                        archive.index_cache.insert(entry_path, entry_header) catch {};
+
+                        break: find_header entry_header;
+                    }
+
+                    // Move over file data following the entry.
+                    var to_skip = entry_header.file_size;
+
+                    while (to_skip != 0) {
+                        const skipped = std.math.min(to_skip, std.math.maxInt(i64));
+
+                        try archive.file_access.skip(@intCast(i64, skipped));
+
+                        to_skip -= skipped;
+                    }
+                }
+
+                return error.EntryNotFound;
+            },
+
+            .owner = &archive.file_access,
+            .cursor = 0,
+        };
     }
 
     ///
-    /// Magic identifier used to validate [Entry] data.
     ///
-    const signature_magic = [3]u8{'o', 'a', 'r'};
+    ///
+    pub fn init(allocator: std.mem.Allocator, archive_file_access: sys.FileAccess) InitError!Archive {
+        return Archive{
+            .index_cache = try IndexCache.init(allocator),
+            .file_access = archive_file_access,
+        };
+    }
+};
+
+///
+/// Handles the state of an opened archive entry.
+///
+pub const Entry = struct {
+    owner: ?*sys.FileAccess,
+    cursor: u64,
+    header: Header,
+
+    ///
+    /// An entry block of an Oar archive file.
+    ///
+    /// Typically, following the block in memory is the file data it holds the meta-information for.
+    ///
+    pub const Header = extern struct {
+        signature: [signature_magic.len]u8 = signature_magic,
+        revision: u8,
+        name_buffer: [255]u8 = std.mem.zeroes([255]u8),
+        name_length: u8 = 0,
+        file_size: u64,
+        file_offset: u64,
+        padding: [232]u8 = std.mem.zeroes([232]u8),
+
+        comptime {
+            const entry_size = @sizeOf(Header);
+
+            if (entry_size != 512)
+                @compileError("Entry is " ++
+                    std.fmt.comptimePrint("{d}", .{entry_size}) ++ " bytes");
+        }
+
+        ///
+        /// Magic identifier used to validate [Entry] data.
+        ///
+        pub const signature_magic = [3]u8{'o', 'a', 'r'};
+    };
 };

src/sys.zig

@@ -8,7 +8,6 @@ const meta = @import("./meta.zig");
 const oar = @import("./oar.zig");
 const stack = @import("./stack.zig");
 const std = @import("std");
-const table = @import("./table.zig");
 
 ///
 /// A thread-safe platform abstraction over multiplexing system I/O processing and event handling.
@@ -131,28 +130,25 @@ pub const AppContext = opaque {
         }
 
         ///
-        /// Initializes a new [Implemenation] with `data_archive_file_access` as the data archive to
-        /// read from and `user_path_prefix` as the native writable user data directory.
+        /// Initializes a new [Implemenation] with `data_access` as the data archive to read from
+        /// and `user_path_prefix` as the native writable user data directory.
         ///
         /// Returns the created [Implementation] value on success or [InitError] on failure.
         ///
-        fn init(allocator: std.mem.Allocator,
-            data_archive_file_access: FileAccess) InitError!Implementation {
-
+        fn init(allocator: std.mem.Allocator, data_access: FileAccess) InitError!Implementation {
             const user_path_prefix = ext.SDL_GetPrefPath("ona", "ona") orelse
                 return error.OutOfMemory;
 
             return Implementation{
-                .user_file_system = .{.native = .{.path_prefix =
-                    user_path_prefix[0 .. std.mem.len(user_path_prefix)]}},
+                .user_file_system = .{.native =
+                    user_path_prefix[0 .. std.mem.len(user_path_prefix)]},
 
                 .message_semaphore = ext.SDL_CreateSemaphore(0) orelse return error.OutOfSemaphores,
                 .message_mutex = ext.SDL_CreateMutex() orelse return error.OutOfMutexes,
                 .user_path_prefix = user_path_prefix,
 
                 .data_file_system = .{.archive = .{
-                    .file_access = data_archive_file_access,
-                    .index_cache = try FileSystem.ArchiveIndexCache.init(allocator),
+                    .instance = try oar.Archive.init(allocator, data_access),
                 }},
 
                 .message_thread = null,
@@ -283,6 +279,7 @@ pub const FileAccess = struct {
         read: fn (*anyopaque, []u8) Error!usize,
         seek: fn (*anyopaque, u64) Error!void,
         seekToEnd: fn (*anyopaque) Error!void,
+        skip: fn (*anyopaque, i64) Error!void,
     };
 
     ///
@@ -343,14 +340,22 @@ pub const FileAccess = struct {
     }
 
     ///
-    /// Attempts to seek `file_access` to the end of the file while using `app_context` as the execution
-    /// context.
+    /// Attempts to seek `file_access` to the end of the file.
     ///
     /// Returns [Error] on failure.
     ///
     pub fn seekToEnd(file_access: *FileAccess) Error!void {
         return file_access.implementation.seekToEnd(file_access.context);
     }
+
+    ///
+    /// Attempts to seek `file_access` by `offset` from the current file position.
+    ///
+    /// Returns [Error] on failure;
+    ///
+    pub fn skip(file_access: *FileAccess, offset: i64) Error!void {
+        return file_access.implementation.skip(file_access.context, offset);
+    }
 };
 
 ///
@@ -358,31 +363,15 @@ pub const FileAccess = struct {
 /// available to the application in a sandboxed environment.
 ///
 pub const FileSystem = union(enum) {
-    native: struct {
-        path_prefix: []const u8,
-    },
+    native: []const u8,
 
     archive: struct {
-        file_access: FileAccess,
-        index_cache: ArchiveIndexCache,
+        instance: oar.Archive,
+        entry_table: [max_open_entries]oar.Entry = std.mem.zeroes([max_open_entries]oar.Entry),
 
-        entry_table: [max_open_entries]ArchiveEntry =
-            std.mem.zeroes([max_open_entries]ArchiveEntry),
-
-        const max_open_entries = 16;
+        pub const max_open_entries = 16;
     },
 
-    ///
-    /// Handles the state of an opened archive entry.
-    ///
-    const ArchiveEntry = struct {
-        using: ?*FileAccess,
-        header: oar.Entry,
-        cursor: u64,
-    };
-
-    const ArchiveIndexCache = table.Hashed([]const u8, oar.Entry, table.string_context);
-
     ///
     /// Platform-agnostic mechanism for referencing files and directories on a [FileSystem].
     ///
@@ -462,57 +451,37 @@ pub const FileSystem = union(enum) {
                 .archive => |*archive| {
                     if (mode != .readonly) return error.ModeUnsupported;
 
-                    for (archive.entry_table) |*entry| if (entry.using == null) {
-                        const entry_path = path.buffer[0 .. path.length];
-
-                        entry.* = .{
-                            .header = find_header: {
-                                if (archive.index_cache.lookup(entry_path)) |header|
-                                    break: find_header header.*;
-
-                                const header = oar.Entry.find(archive.file_access,
-                                    entry_path) catch return error.FileNotFound;
-
-                                // If caching fails... oh well...
-                                archive.index_cache.insert(entry_path, header) catch {};
-
-                                break: find_header header;
-                            },
-
-                            .using = &archive.file_access,
-                            .cursor = 0,
-                        };
-
+                    for (archive.entry_table) |*entry| if (entry.owner == null) {
                         const Implementation = struct {
-                            fn archiveEntryCast(context: *anyopaque) *ArchiveEntry {
-                                return @ptrCast(*ArchiveEntry, @alignCast(
-                                    @alignOf(ArchiveEntry), context));
+                            fn close(context: *anyopaque) void {
+                                entryCast(context).owner = null;
                             }
 
-                            fn close(context: *anyopaque) void {
-                                archiveEntryCast(context).using = null;
+                            fn entryCast(context: *anyopaque) *oar.Entry {
+                                return @ptrCast(*oar.Entry, @alignCast(
+                                    @alignOf(oar.Entry), context));
                             }
 
                             fn queryCursor(context: *anyopaque) FileAccess.Error!u64 {
-                                const archive_entry = archiveEntryCast(context);
+                                const archive_entry = entryCast(context);
 
-                                if (archive_entry.using == null) return error.FileInaccessible;
+                                if (archive_entry.owner == null) return error.FileInaccessible;
 
                                 return archive_entry.cursor;
                             }
 
                             fn queryLength(context: *anyopaque) FileAccess.Error!u64 {
-                                const archive_entry = archiveEntryCast(context);
+                                const archive_entry = entryCast(context);
 
-                                if (archive_entry.using == null) return error.FileInaccessible;
+                                if (archive_entry.owner == null) return error.FileInaccessible;
 
                                 return archive_entry.header.file_size;
                             }
 
                             fn read(context: *anyopaque, buffer: []u8) FileAccess.Error!usize {
-                                const archive_entry = archiveEntryCast(context);
+                                const archive_entry = entryCast(context);
 
-                                const file_access = archive_entry.using orelse
+                                const file_access = archive_entry.owner orelse
                                     return error.FileInaccessible;
 
                                 if (archive_entry.cursor >= archive_entry.header.file_size)
@@ -525,22 +494,42 @@ pub const FileSystem = union(enum) {
                             }
 
                             fn seek(context: *anyopaque, cursor: usize) FileAccess.Error!void {
-                                const archive_entry = archiveEntryCast(context);
+                                const archive_entry = entryCast(context);
 
-                                if (archive_entry.using == null) return error.FileInaccessible;
+                                if (archive_entry.owner == null) return error.FileInaccessible;
 
                                 archive_entry.cursor = cursor;
                             }
 
                             fn seekToEnd(context: *anyopaque) FileAccess.Error!void {
-                                const archive_entry = archiveEntryCast(context);
+                                const archive_entry = entryCast(context);
 
-                                if (archive_entry.using == null) return error.FileInaccessible;
+                                if (archive_entry.owner == null) return error.FileInaccessible;
 
                                 archive_entry.cursor = archive_entry.header.file_size;
                             }
+
+                            fn skip(context: *anyopaque, offset: i64) FileAccess.Error!void {
+                                const math = std.math;
+                                const archive_entry = entryCast(context);
+
+                                if (archive_entry.owner == null) return error.FileInaccessible;
+
+                                if (offset < 0) {
+                                    archive_entry.cursor = math.max(0,
+                                        archive_entry.cursor - math.absCast(offset));
+                                } else {
+                                    archive_entry.cursor += @intCast(u64, offset);
+                                }
+                            }
                         };
 
+                        entry.* = archive.instance.find(path.buffer[0 .. path.length]) catch |err|
+                            return switch (err) {
+                                error.FileInaccessible => error.FileNotFound,
+                                error.EntryNotFound => error.FileNotFound,
+                            };
+
                         return FileAccess{
                             .context = entry,
 
@@ -551,6 +540,7 @@ pub const FileSystem = union(enum) {
                                 .read = Implementation.read,
                                 .seek = Implementation.seek,
                                 .seekToEnd = Implementation.seekToEnd,
+                                .skip = Implementation.skip,
                             },
                         };
                     };
@@ -559,22 +549,19 @@ pub const FileSystem = union(enum) {
                 },
 
                 .native => |native| {
-                    if (native.path_prefix.len == 0) return error.FileNotFound;
+                    if (native.len == 0) return error.FileNotFound;
 
                     var path_buffer = std.mem.zeroes([4096]u8);
+                    const seperator_length = @boolToInt(native[native.len - 1] != seperator);
 
-                    const seperator_length = @boolToInt(native.path_prefix[
-                        native.path_prefix.len - 1] != seperator);
-
-                    if ((native.path_prefix.len + seperator_length + path.length) >=
+                    if ((native.len + seperator_length + path.length) >=
                         path_buffer.len) return error.FileNotFound;
 
-                    std.mem.copy(u8, path_buffer[0 ..], native.path_prefix);
+                    std.mem.copy(u8, path_buffer[0 ..], native);
 
-                    if (seperator_length != 0)
-                        path_buffer[native.path_prefix.len] = seperator;
+                    if (seperator_length != 0) path_buffer[native.len] = seperator;
 
-                    std.mem.copy(u8, path_buffer[native.path_prefix.len ..
+                    std.mem.copy(u8, path_buffer[native.len ..
                         path_buffer.len], path.buffer[0 .. path.length]);
 
                     ext.SDL_ClearError();
@@ -629,15 +616,14 @@ pub const FileSystem = union(enum) {
 
                             while (to_seek != 0) {
                                 const math = std.math;
-                                const sought = @intCast(i64, math.min(to_seek, math.maxInt(i64)));
+                                const sought = math.min(to_seek, math.maxInt(i64));
 
                                 ext.SDL_ClearError();
 
-                                if (ext.SDL_RWseek(rwOpsCast(context), sought, ext.RW_SEEK_CUR) < 0)
-                                    return error.FileInaccessible;
+                                if (ext.SDL_RWseek(rwOpsCast(context), @intCast(i64, sought),
+                                    ext.RW_SEEK_CUR) < 0) return error.FileInaccessible;
 
-                                // Cannot be less than zero because it is derived from `read`.
-                                to_seek -= @intCast(u64, sought);
+                                to_seek -= sought;
                             }
                         }
 
@@ -647,6 +633,13 @@ pub const FileSystem = union(enum) {
                             if (ext.SDL_RWseek(rwOpsCast(context), 0, ext.RW_SEEK_END) < 0)
                                 return error.FileInaccessible;
                         }
+
+                        fn skip(context: *anyopaque, offset: i64) FileAccess.Error!void {
+                            ext.SDL_ClearError();
+
+                            if (ext.SDL_RWseek(rwOpsCast(context), offset, ext.RW_SEEK_SET) < 0)
+                                return error.FileInaccessible;
+                        }
                     };
 
                     return FileAccess{
@@ -663,6 +656,7 @@ pub const FileSystem = union(enum) {
                             .read = Implementation.read,
                             .seek = Implementation.seek,
                             .seekToEnd = Implementation.seekToEnd,
+                            .skip = Implementation.skip,
                         },
                     };
                 },
@@ -855,7 +849,7 @@ pub fn runGraphics(comptime Error: anytype,
 
     defer ext.SDL_DestroyRenderer(renderer);
 
-    var cwd_file_system = FileSystem{.native =.{.path_prefix = "./"}};
+    var cwd_file_system = FileSystem{.native ="./"};
     var data_access = try (try cwd_file_system.joinedPath(&.{"./data.oar"})).open(.readonly);
 
     defer data_access.close();