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LibGfx: Read OpenType TTCHeaderV1 as a struct

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Also check that the requested font index actually exists in the font
collection.
This commit is contained in:
Sam Atkins 2023-10-26 10:55:28 +01:00 committed by Andreas Kling
parent 1a6da4fbf2
commit 984a2c314b
1 changed files with 30 additions and 6 deletions
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36
Userland/Libraries/LibGfx/Font/OpenType/Font.cpp
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@ -23,6 +23,26 @@
namespace OpenType {
// https://learn.microsoft.com/en-us/typography/opentype/spec/otff#ttc-header
struct [[gnu::packed]] TTCHeaderV1 {
Tag ttc_tag; // Font Collection ID string: 'ttcf' (used for fonts with CFF or CFF2 outlines as well as TrueType outlines)
BigEndian<u16> major_version; // Major version of the TTC Header, = 1.
BigEndian<u16> minor_version; // Minor version of the TTC Header, = 0.
BigEndian<u32> num_fonts; // Number of fonts in TTC
Offset32 table_directory_offsets; // Array of offsets to the TableDirectory for each font from the beginning of the file
};
static_assert(AssertSize<TTCHeaderV1, 16>());
}
template<>
class AK::Traits<OpenType::TTCHeaderV1> : public GenericTraits<OpenType::TTCHeaderV1> {
public:
static constexpr bool is_trivially_serializable() { return true; }
};
namespace OpenType {
u16 be_u16(u8 const*);
u32 be_u32(u8 const*);
i16 be_i16(u8 const*);
@ -63,16 +83,20 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_resource(Core::Resource const&
ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_externally_owned_memory(ReadonlyBytes buffer, unsigned index)
{
if (buffer.size() < 4)
return Error::from_string_literal("Font file too small");
FixedMemoryStream stream { buffer };
u32 tag = be_u32(buffer.data());
auto tag = TRY(stream.read_value<Tag>());
if (tag == tag_from_str("ttcf")) {
// It's a font collection
if (buffer.size() < (u32)Sizes::TTCHeaderV1 + sizeof(u32) * (index + 1))
return Error::from_string_literal("Font file too small");
TRY(stream.seek(0, SeekMode::SetPosition));
auto ttc_header_v1 = TRY(stream.read_in_place<TTCHeaderV1>());
// FIXME: Check for major_version == 2.
u32 offset = be_u32(buffer.offset((u32)Sizes::TTCHeaderV1 + sizeof(u32) * index));
if (index >= ttc_header_v1->num_fonts)
return Error::from_string_literal("Requested font index is too large");
TRY(stream.seek(ttc_header_v1->table_directory_offsets + sizeof(u32) * index, SeekMode::SetPosition));
auto offset = TRY(stream.read_value<BigEndian<u32>>());
return try_load_from_offset(buffer, offset);
}
if (tag == tag_from_str("OTTO"))