LibGfx: Add initial ISO BMFF parsing and a utility to print file info

Currently, the `isobmff` utility will only print the media file type
info from the FileTypeBox (major brand and compatible brands), as well
as the names and sizes of top-level boxes.

Userland/Libraries/LibGfx/ImageFormats/ISOBMFF/Boxes.cpp

@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2023, Gregory Bertilson <Zaggy1024@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "Boxes.h"
+
+namespace Gfx::ISOBMFF {
+
+ErrorOr<BoxHeader> read_box_header(Stream& stream)
+{
+    BoxHeader header;
+    u64 total_size = TRY(stream.read_value<BigEndian<u32>>());
+    header.type = TRY(stream.read_value<BoxType>());
+
+    u64 data_size_read = sizeof(u32) + sizeof(BoxType);
+
+    if (total_size == 1) {
+        total_size = TRY(stream.read_value<BigEndian<u64>>());
+        data_size_read += sizeof(u64);
+    }
+
+    header.contents_size = total_size - data_size_read;
+    return header;
+}
+
+void Box::dump(String const& prepend) const
+{
+    outln("{}{}", prepend, box_type());
+}
+
+ErrorOr<void> FullBox::read_from_stream(BoxStream& stream)
+{
+    u32 data = TRY(stream.read_value<BigEndian<u32>>());
+    // unsigned int(8) version
+    version = static_cast<u8>(data >> 24);
+    // unsigned int(24) flags
+    flags = data & 0xFFF;
+    return {};
+}
+
+void FullBox::dump(String const& prepend) const
+{
+    outln("{}{} (version = {}, flags = 0x{:x})", prepend, box_type(), version, flags);
+}
+
+static String add_indent(String const& string)
+{
+    return MUST(String::formatted("{}  ", string));
+}
+
+ErrorOr<void> UnknownBox::read_from_stream(BoxStream& stream)
+{
+    m_contents_size = stream.remaining();
+    TRY(stream.discard_remaining());
+    return {};
+}
+
+void UnknownBox::dump(String const& prepend) const
+{
+    Box::dump(prepend);
+
+    auto indented_prepend = add_indent(prepend);
+    outln("{}[ {} bytes ]", prepend, m_contents_size);
+}
+
+ErrorOr<void> FileTypeBox::read_from_stream(BoxStream& stream)
+{
+    // unsigned int(32) major_brand;
+    major_brand = TRY(stream.read_value<BrandIdentifier>());
+    // unsigned int(32) minor_version;
+    minor_version = TRY(stream.read_value<BigEndian<u32>>());
+
+    // unsigned int(32) compatible_brands[]; // to end of the box
+    if (stream.remaining() % sizeof(BrandIdentifier) != 0)
+        return Error::from_string_literal("FileTypeBox compatible_brands contains a partial brand");
+
+    for (auto minor_brand_count = stream.remaining() / sizeof(BrandIdentifier); minor_brand_count > 0; minor_brand_count--)
+        TRY(compatible_brands.try_append(TRY(stream.read_value<BrandIdentifier>())));
+
+    return {};
+}
+
+void FileTypeBox::dump(String const& prepend) const
+{
+    FullBox::dump(prepend);
+
+    auto indented_prepend = add_indent(prepend);
+
+    outln("{}- major_brand = {}", prepend, major_brand);
+    outln("{}- minor_version = {}", prepend, minor_version);
+
+    StringBuilder compatible_brands_string;
+    compatible_brands_string.append("- compatible_brands = { "sv);
+    for (size_t i = 0; i < compatible_brands.size() - 1; i++)
+        compatible_brands_string.appendff("{}, ", compatible_brands[i]);
+    compatible_brands_string.appendff("{} }}", compatible_brands[compatible_brands.size() - 1]);
+    outln("{}{}", prepend, compatible_brands_string.string_view());
+}
+
+}