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diff --git a/Lessons/Lesson_71/README.md b/Lessons/Lesson_71/README.md new file mode 100644 index 0000000..43a5c84 --- /dev/null +++ b/Lessons/Lesson_71/README.md @@ -0,0 +1,128 @@ +# stringref + +https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/212_vfr_expression_statement_definition#2.12.11.4.7-stringref + +`stringref` statement helps to get string values to the VFR code: +``` +EFI_IFR_STRING_REF1 + +Summary: +Push a string on the expression stack. + +Prototype: + +#define EFI_IFR_STRING_REF1_OP 0x4e + +typedef struct _EFI_IFR_STRING_REF1 { + EFI_IFR_OP_HEADER Header; + EFI_STRING_ID StringId; +} EFI_IFR_STRING_REF1; + +Members: +Header The byte sequence that defines the type of opcode as well as the length of the opcode being defined. + Header.OpCode = EFI_IFR_STRING_REF1_OP. +StringId The string’s identifier, which must be unique within the package list. + +Description: +Push the string specified by StringId on to the expression stack. If the string does not exist, then push an empty string. +``` + +For example this condition in a `suppressif` statement is TRUE only if a string element has a specific data in itself: +``` +string + name = StringQuestion, + ... +endstring; + +suppressif questionref(StringQuestion) == stringref(STRING_TOKEN(TEST_STRING)); + ... +endif; +``` + +Off course you need to define this new token that we use here for comparision: +``` +#string TEST_STRING #language en-US "EDKII" +``` + +Another example of potential `stringref` usage: +``` +string + varid = FormData.StringValue, + prompt = STRING_TOKEN(STRING_PROMPT), + help = STRING_TOKEN(STRING_HELP), + minsize = 5, + maxsize = 10, + warningif + prompt = STRING_TOKEN(WARNING_IF_PROMPT), + pushthis == stringref(STRING_TOKEN(TEST_STRING)) + endif; +endstring; +``` + +This code outputs a warning message if input string is equal to "EDKII". + +# toupper/tolower + +https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/212_vfr_expression_statement_definition#2.12.11.6.8-toupper + +https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/212_vfr_expression_statement_definition#2.12.11.6.9-tolower + +The `toupper` and `tolower` builtin functions are encoded in `EFI_IFR_TO_UPPER` (=0x21) and `EFI_IFR_TO_LOWER` (=0x20) opcodes and help to change case-register of the string data. + +For example this code will output warning on "EDKII" input as well as on "Edkii", "EDkii", "EDKii", "eDKii" and so on: +``` +string + varid = FormData.StringValue, + prompt = STRING_TOKEN(STRING_PROMPT), + help = STRING_TOKEN(STRING_HELP), + minsize = 5, + maxsize = 10, + warningif + prompt = STRING_TOKEN(WARNING_IF_PROMPT), + toupper(pushthis) == stringref(STRING_TOKEN(TEST_STRING)) + endif; +endstring; +``` + +And this code outputs warning only on "edkii" input: +``` +string + name = StringQuestion, + varid = FormData.StringValue, + prompt = STRING_TOKEN(STRING_PROMPT), + help = STRING_TOKEN(STRING_HELP), + minsize = 5, + maxsize = 10, + warningif + prompt = STRING_TOKEN(WARNING_IF_PROMPT), + pushthis == tolower(stringref(STRING_TOKEN(TEST_STRING))) + endif; +endstring; +``` + +# length + +https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/212_vfr_expression_statement_definition#2.12.11.6.1-length + +The `length` keyword help get length of a buffer or a string. It is encoded with the `EFI_IFR_LENGTH_OP = 0x56` opcode. + +For example here the code suppressed only if the string question data is a string exactly of 7 symbols: +``` +suppressif length(questionref(StringQuestion)) == 7; + ... +endif; +``` + +# More advanced atring builtins + + +| keyword | IFR opcode | link | +| ------------- | ------------- | +| `catenate` | `EFI_IFR_CATENATE` | https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/212_vfr_expression_statement_definition#2.12.11.1-catenate | +| `match` | `EFI_IFR_MATCH` | https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/212_vfr_expression_statement_definition#2.12.11.2-match | +| `match2` | `EFI_IFR_MATCH2` | https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/212_vfr_expression_statement_definition#2.12.11.9-match2 | +| `find` | `EFI_IFR_FIND` | https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/212_vfr_expression_statement_definition#2.12.11.7.2-find | +| `mid` | `EFI_IFR_MID` | https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/212_vfr_expression_statement_definition#2.12.11.7.3-mid | +| `token` | `EFI_IFR_TOKEN` | https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/212_vfr_expression_statement_definition#2.12.11.7.4-tok | +| `span` | `EFI_IFR_SPAN` | https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/212_vfr_expression_statement_definition#2.12.11.7.5-span | + |