Need clarification about UEFI Strings

Need clarification about UEFI Strings

[Ayush Singh]

Hello everyone, I am trying to write an implementation for UEFI
strings in Rust and just wanted clarification about some things.

Are UEFI Strings UTF-16 encoded? I have looked at some previous Rust
implementations for this and it seems UEFI does not support the whole
UTF-16 but rather only UCS-2
(https://en.wikipedia.org/wiki/Universal_Coded_Character_Set) which is
a subset of UTF-16.

There is also something called WTF-8
(https://en.wikipedia.org/wiki/UTF-8#WTF-8) which Rust uses to
represent OsStrings in Windows which is supposed to use UTF-16 (?).

Anyway, if someone can point me to the resources/specifications of
UEFI Strings, it would be a great help.

Ayush Singh

Re: [edk2-devel] Need clarification about UEFI Strings

[Pedro Falcato]

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Hi Ayush,

In the latest UEFI 2.9 spec, it's specified under 2.3.1 that CHAR8
strings/characters are (usually) ASCII, and CHAR16 strings/characters are
(usually) UCS-2 (*not* UTF-16).

On Tue, Jun 7, 2022 at 7:02 AM Ayush Singh <ayushdevel1325@gmail.com> wrote:

> Hello everyone, I am trying to write an implementation for UEFI
> strings in Rust and just wanted clarification about some things.
>
> Are UEFI Strings UTF-16 encoded? I have looked at some previous Rust
> implementations for this and it seems UEFI does not support the whole
> UTF-16 but rather only UCS-2
> (https://en.wikipedia.org/wiki/Universal_Coded_Character_Set) which is
> a subset of UTF-16.
>
> There is also something called WTF-8
> (https://en.wikipedia.org/wiki/UTF-8#WTF-8) which Rust uses to
> represent OsStrings in Windows which is supposed to use UTF-16 (?).
>
> Anyway, if someone can point me to the resources/specifications of
> UEFI Strings, it would be a great help.
>
> Ayush Singh
>
>
> 
>
>
>

-- 
Pedro Falcato

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Re: [edk2-devel] Need clarification about UEFI Strings

[Ayush Singh]

Thanks, Pedro,

However, according to the specs, it is possible to construct ASCII
Strings as well. So when would ASCII Strings be used over normal UCS-2
Strings?

Ayush Singh

On Tue, Jun 7, 2022 at 1:13 PM Pedro Falcato <pedro.falcato@gmail.com> wrote:
>
> Hi Ayush,
>
> In the latest UEFI 2.9 spec, it's specified under 2.3.1 that CHAR8 strings/characters are (usually) ASCII, and CHAR16 strings/characters are (usually) UCS-2 (*not* UTF-16).
>
> On Tue, Jun 7, 2022 at 7:02 AM Ayush Singh <ayushdevel1325@gmail.com> wrote:
>>
>> Hello everyone, I am trying to write an implementation for UEFI
>> strings in Rust and just wanted clarification about some things.
>>
>> Are UEFI Strings UTF-16 encoded? I have looked at some previous Rust
>> implementations for this and it seems UEFI does not support the whole
>> UTF-16 but rather only UCS-2
>> (https://en.wikipedia.org/wiki/Universal_Coded_Character_Set) which is
>> a subset of UTF-16.
>>
>> There is also something called WTF-8
>> (https://en.wikipedia.org/wiki/UTF-8#WTF-8) which Rust uses to
>> represent OsStrings in Windows which is supposed to use UTF-16 (?).
>>
>> Anyway, if someone can point me to the resources/specifications of
>> UEFI Strings, it would be a great help.
>>
>> Ayush Singh
>>
>>
>> 
>>
>>
>
>
> --
> Pedro Falcato

Re: [edk2-devel] Need clarification about UEFI Strings

[Pedro Falcato]

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I'd say that it depends. But 98% of the strings you'll find in UEFI
(including APIs) are UCS-2 CHAR16 strings.

On Tue, Jun 7, 2022 at 9:19 AM Ayush Singh <ayushdevel1325@gmail.com> wrote:

> Thanks, Pedro,
>
> However, according to the specs, it is possible to construct ASCII
> Strings as well. So when would ASCII Strings be used over normal UCS-2
> Strings?
>
> Ayush Singh
>
> On Tue, Jun 7, 2022 at 1:13 PM Pedro Falcato <pedro.falcato@gmail.com>
> wrote:
> >
> > Hi Ayush,
> >
> > In the latest UEFI 2.9 spec, it's specified under 2.3.1 that CHAR8
> strings/characters are (usually) ASCII, and CHAR16 strings/characters are
> (usually) UCS-2 (*not* UTF-16).
> >
> > On Tue, Jun 7, 2022 at 7:02 AM Ayush Singh <ayushdevel1325@gmail.com>
> wrote:
> >>
> >> Hello everyone, I am trying to write an implementation for UEFI
> >> strings in Rust and just wanted clarification about some things.
> >>
> >> Are UEFI Strings UTF-16 encoded? I have looked at some previous Rust
> >> implementations for this and it seems UEFI does not support the whole
> >> UTF-16 but rather only UCS-2
> >> (https://en.wikipedia.org/wiki/Universal_Coded_Character_Set) which is
> >> a subset of UTF-16.
> >>
> >> There is also something called WTF-8
> >> (https://en.wikipedia.org/wiki/UTF-8#WTF-8) which Rust uses to
> >> represent OsStrings in Windows which is supposed to use UTF-16 (?).
> >>
> >> Anyway, if someone can point me to the resources/specifications of
> >> UEFI Strings, it would be a great help.
> >>
> >> Ayush Singh
> >>
> >>
> >> 
> >>
> >>
> >
> >
> > --
> > Pedro Falcato
>


-- 
Pedro Falcato

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Re: [edk2-devel] Need clarification about UEFI Strings

[Ayush Singh]

Ok, Thanks for all the help.

On Tue, Jun 7, 2022 at 3:28 PM Pedro Falcato <pedro.falcato@gmail.com> wrote:
>
> I'd say that it depends. But 98% of the strings you'll find in UEFI (including APIs) are UCS-2 CHAR16 strings.
>
> On Tue, Jun 7, 2022 at 9:19 AM Ayush Singh <ayushdevel1325@gmail.com> wrote:
>>
>> Thanks, Pedro,
>>
>> However, according to the specs, it is possible to construct ASCII
>> Strings as well. So when would ASCII Strings be used over normal UCS-2
>> Strings?
>>
>> Ayush Singh
>>
>> On Tue, Jun 7, 2022 at 1:13 PM Pedro Falcato <pedro.falcato@gmail.com> wrote:
>> >
>> > Hi Ayush,
>> >
>> > In the latest UEFI 2.9 spec, it's specified under 2.3.1 that CHAR8 strings/characters are (usually) ASCII, and CHAR16 strings/characters are (usually) UCS-2 (*not* UTF-16).
>> >
>> > On Tue, Jun 7, 2022 at 7:02 AM Ayush Singh <ayushdevel1325@gmail.com> wrote:
>> >>
>> >> Hello everyone, I am trying to write an implementation for UEFI
>> >> strings in Rust and just wanted clarification about some things.
>> >>
>> >> Are UEFI Strings UTF-16 encoded? I have looked at some previous Rust
>> >> implementations for this and it seems UEFI does not support the whole
>> >> UTF-16 but rather only UCS-2
>> >> (https://en.wikipedia.org/wiki/Universal_Coded_Character_Set) which is
>> >> a subset of UTF-16.
>> >>
>> >> There is also something called WTF-8
>> >> (https://en.wikipedia.org/wiki/UTF-8#WTF-8) which Rust uses to
>> >> represent OsStrings in Windows which is supposed to use UTF-16 (?).
>> >>
>> >> Anyway, if someone can point me to the resources/specifications of
>> >> UEFI Strings, it would be a great help.
>> >>
>> >> Ayush Singh
>> >>
>> >>
>> >> 
>> >>
>> >>
>> >
>> >
>> > --
>> > Pedro Falcato
>
>
>
> --
> Pedro Falcato

Re: [edk2-devel] Need clarification about UEFI Strings

[Ayush Singh]

Just for clarification, UCS2 and not UTF-16 means there are no
surrogate pairs right?

Ayush Singh

On Tue, Jun 7, 2022 at 5:15 PM Ayush Singh via groups.io
<ayushdevel1325=gmail.com@groups.io> wrote:
>
> Ok, Thanks for all the help.
>
> On Tue, Jun 7, 2022 at 3:28 PM Pedro Falcato <pedro.falcato@gmail.com> wrote:
> >
> > I'd say that it depends. But 98% of the strings you'll find in UEFI (including APIs) are UCS-2 CHAR16 strings.
> >
> > On Tue, Jun 7, 2022 at 9:19 AM Ayush Singh <ayushdevel1325@gmail.com> wrote:
> >>
> >> Thanks, Pedro,
> >>
> >> However, according to the specs, it is possible to construct ASCII
> >> Strings as well. So when would ASCII Strings be used over normal UCS-2
> >> Strings?
> >>
> >> Ayush Singh
> >>
> >> On Tue, Jun 7, 2022 at 1:13 PM Pedro Falcato <pedro.falcato@gmail.com> wrote:
> >> >
> >> > Hi Ayush,
> >> >
> >> > In the latest UEFI 2.9 spec, it's specified under 2.3.1 that CHAR8 strings/characters are (usually) ASCII, and CHAR16 strings/characters are (usually) UCS-2 (*not* UTF-16).
> >> >
> >> > On Tue, Jun 7, 2022 at 7:02 AM Ayush Singh <ayushdevel1325@gmail.com> wrote:
> >> >>
> >> >> Hello everyone, I am trying to write an implementation for UEFI
> >> >> strings in Rust and just wanted clarification about some things.
> >> >>
> >> >> Are UEFI Strings UTF-16 encoded? I have looked at some previous Rust
> >> >> implementations for this and it seems UEFI does not support the whole
> >> >> UTF-16 but rather only UCS-2
> >> >> (https://en.wikipedia.org/wiki/Universal_Coded_Character_Set) which is
> >> >> a subset of UTF-16.
> >> >>
> >> >> There is also something called WTF-8
> >> >> (https://en.wikipedia.org/wiki/UTF-8#WTF-8) which Rust uses to
> >> >> represent OsStrings in Windows which is supposed to use UTF-16 (?).
> >> >>
> >> >> Anyway, if someone can point me to the resources/specifications of
> >> >> UEFI Strings, it would be a great help.
> >> >>
> >> >> Ayush Singh
> >> >>
> >> >>
> >> >>
> >> >>
> >> >>
> >> >
> >> >
> >> > --
> >> > Pedro Falcato
> >
> >
> >
> > --
> > Pedro Falcato
>
>
> 
>
>