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AK+Kernel: Implement UUID mixed endianness support

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This is being used by GUID partitions so the first three dash-delimited
fields of the GUID are stored in little endian order but the last two
fields are stored in big endian order, hence it's a representation which
is mixed.
This commit is contained in:
Liav A 2022-01-28 20:21:40 +02:00 committed by Idan Horowitz
parent 2d67d141e6
commit 308e54bc19
Notes: sideshowbarker 2024-07-17 20:02:47 +09:00 
Author: https://github.com/supercomputer7
Commit: https://github.com/SerenityOS/serenity/commit/308e54bc196
Pull-request: https://github.com/SerenityOS/serenity/pull/12187
Reviewed-by: https://github.com/IdanHo
3 changed files with 47 additions and 6 deletions
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41
AK/UUID.cpp
View File

@ -16,7 +16,7 @@ UUID::UUID(Array<u8, 16> uuid_buffer)
uuid_buffer.span().copy_to(m_uuid_buffer);
}
void UUID::convert_string_view_to_uuid(StringView uuid_string_view)
void UUID::convert_string_view_to_little_endian_uuid(StringView uuid_string_view)
{
VERIFY(uuid_string_view.length() == 36);
auto first_unit = MUST(decode_hex(uuid_string_view.substring_view(0, 8)));
@ -36,9 +36,44 @@ void UUID::convert_string_view_to_uuid(StringView uuid_string_view)
m_uuid_buffer.span().overwrite(10, fifth_unit.data(), fifth_unit.size());
}
UUID::UUID(StringView uuid_string_view)
void UUID::convert_string_view_to_mixed_endian_uuid(StringView uuid_string_view)
{
convert_string_view_to_uuid(uuid_string_view);
VERIFY(uuid_string_view.length() == 36);
auto first_unit = MUST(decode_hex(uuid_string_view.substring_view(0, 8)));
auto second_unit = MUST(decode_hex(uuid_string_view.substring_view(9, 4)));
auto third_unit = MUST(decode_hex(uuid_string_view.substring_view(14, 4)));
auto fourth_unit = MUST(decode_hex(uuid_string_view.substring_view(19, 4)));
auto fifth_unit = MUST(decode_hex(uuid_string_view.substring_view(24, 12)));
VERIFY(first_unit.size() == 4 && second_unit.size() == 2
&& third_unit.size() == 2 && fourth_unit.size() == 2
&& fifth_unit.size() == 6);
// Revert endianness for first 4 bytes
for (size_t index = 0; index < 4; index++) {
m_uuid_buffer[3 - index] = first_unit[index];
}
// Revert endianness for second 2 bytes and again for 2 bytes
for (size_t index = 0; index < 2; index++) {
m_uuid_buffer[3 + 2 - index] = second_unit[index];
m_uuid_buffer[5 + 2 - index] = third_unit[index];
}
m_uuid_buffer.span().overwrite(8, fourth_unit.data(), fourth_unit.size());
m_uuid_buffer.span().overwrite(10, fifth_unit.data(), fifth_unit.size());
}
UUID::UUID(StringView uuid_string_view, Endianness endianness)
{
if (endianness == Endianness::Little) {
convert_string_view_to_little_endian_uuid(uuid_string_view);
return;
} else if (endianness == Endianness::Mixed) {
convert_string_view_to_mixed_endian_uuid(uuid_string_view);
return;
}
VERIFY_NOT_REACHED();
}
String UUID::to_string() const

10
AK/UUID.h
View File

@ -15,9 +15,14 @@ namespace AK {
class UUID {
public:
enum class Endianness {
Mixed,
Little
};
UUID() = default;
UUID(Array<u8, 16> uuid_buffer);
UUID(StringView);
UUID(StringView, Endianness endianness = Endianness::Little);
~UUID() = default;
bool operator==(const UUID&) const;
@ -31,7 +36,8 @@ public:
bool is_zero() const;
private:
void convert_string_view_to_uuid(StringView);
void convert_string_view_to_little_endian_uuid(StringView);
void convert_string_view_to_mixed_endian_uuid(StringView);
Array<u8, 16> m_uuid_buffer {};
};

2
Kernel/Storage/StorageManagement.cpp
View File

@ -219,7 +219,7 @@ UNMAP_AFTER_INIT void StorageManagement::determine_boot_device_with_partition_uu
VERIFY(!m_storage_devices.is_empty());
VERIFY(m_boot_argument.starts_with(partition_uuid_prefix));
auto partition_uuid = UUID(m_boot_argument.substring_view(partition_uuid_prefix.length()));
auto partition_uuid = UUID(m_boot_argument.substring_view(partition_uuid_prefix.length()), UUID::Endianness::Mixed);
if (partition_uuid.to_string().length() != 36) {
// FIXME: It would be helpful to output the specified and detected UUIDs in this case,