Bill -
The expression evaluator must use the actual string values, as you expect.
Section 28.2.5.7.4 says that a string value in an expression is a
"Null-terminated string" not a string ID.
Furthermore, some operations, like Mid() and Token() actually create new string
values. Which string id should hold them? It appears that the current EDK2
browser attempts to create new strings each time. While this might seem like a
clever way to get around the difference and re-use EFI_HII_VALUE (where strings
are a string-id), it actually leads to HII database errors if you play around
in the browser for too long because after the expression is evaluated too many
times, you will eventually run out of string ids (yes, 64k is a large number,
but ...)
Tim
From: bill_mun...@dell.com [mailto:bill_mun...@dell.com]
Sent: Monday, January 07, 2013 4:36 PM
To: edk2-devel@lists.sourceforge.net
Subject: [edk2] strings on HII expression stack
HII has a number of opcodes which can push/pop string values on the HII
expression stack (like the opcodes in the list below). The language in the UEFI
spec made me think that form processors push/pop the actual strings (not HII
string IDs). However, after looking at the EDK2 browser code I get the idea
that these opcodes push/pop string IDs instead of strings. Does the EDK2
browser need to be updated to match the spec in this regard?
EFI_IFR_STRING_REF
EFI_IFR_QUESTION_REF
EFI_IFR_THIS
EFI_IFR_MATCH
EFI_IFR_SPAN
EFI_IFR_TOKEN
Etc.
Thanks for your feedback -
Bill
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