tiny.filigree.font.directory

1const std = @import("std");2const binary = @import("binary.zig");3const model = @import("model.zig");45const FontError = model.FontError;6const Table = binary.Table;7const Tag = model.Tag;8const readU16 = binary.readU16;9const readU32 = binary.readU32;10const tag = model.tag;1112pub fn table(data: []const u8, comptime name: []const u8) FontError!Table {13    return tableAt(data, 0, name);14}1516pub fn tableAt(data: []const u8, directory_offset: usize, comptime name: []const u8) FontError!Table {17    return tableAtTag(data, directory_offset, tag(name));18}1920pub fn tableAtTag(data: []const u8, directory_offset: usize, wanted: Tag) FontError!Table {21    if (directory_offset > data.len or data.len - directory_offset < 12) return error.InvalidFont;22    const num_tables = try readU16(data, directory_offset + 4);23    if (@as(usize, num_tables) > (data.len - directory_offset - 12) / 16) return error.InvalidFont;24    for (0..num_tables) |i| {25        const record = directory_offset + 12 + i * 16;26        if (try readU32(data, record) != wanted) continue;27        const offset = try readU32(data, record + 8);28        const len = try readU32(data, record + 12);29        const start: usize = @intCast(offset);30        const size: usize = @intCast(len);31        if (start > data.len or size > data.len - start) return error.InvalidFont;32        return .{ .offset = start, .len = size };33    }34    return error.MissingTable;35}3637pub fn optional(data: []const u8, comptime name: []const u8) ?Table {38    return table(data, name) catch null;39}4041pub fn optionalAt(data: []const u8, directory_offset: usize, comptime name: []const u8) ?Table {42    return tableAt(data, directory_offset, name) catch null;43}4445pub fn optionalAtTag(data: []const u8, directory_offset: usize, table_tag: Tag) ?Table {46    return tableAtTag(data, directory_offset, table_tag) catch null;47}4849pub fn fontDirectoryOffset(data: []const u8, face_index: u32) FontError!usize {50    if (data.len < 12) return error.InvalidFont;51    if (try readU32(data, 0) != tag("ttcf")) {52        if (face_index != 0) return error.InvalidFont;53        return 0;54    }5556    const version = try readU32(data, 4);57    if (version != 0x00010000 and version != 0x00020000) return error.InvalidFont;58    const face_count = try readU32(data, 8);59    if (face_count == 0 or face_index >= face_count) return error.InvalidFont;60    const face_count_usize: usize = @intCast(face_count);61    if (face_count_usize > (data.len - 12) / 4) return error.InvalidFont;62    const record = 12 + @as(usize, @intCast(face_index)) * 4;63    const offset = try readU32(data, record);64    const directory_offset: usize = @intCast(offset);65    if (directory_offset > data.len or data.len - directory_offset < 12) return error.InvalidFont;66    return directory_offset;67}6869test "table lookup rejects empty directory" {70    try std.testing.expectError(error.InvalidFont, table(&.{}, "head"));71}

1pub const directory = @import("directory.zig");