tuxji commented on code in PR #98: URL: https://github.com/apache/daffodil-site/pull/98#discussion_r1029321583
########## site/dev/design-notes/runtime2-todos.adoc: ########## @@ -36,7 +36,108 @@ If someone wants to help please let the mailto:[email protected][dev] list know in order to avoid duplication. -=== Report hanging problem running sbt (really dev.dirs) from MSYS2 on Windows +=== Anonymous/multiple choice groups + +We already handle elements having xs:choice complex types. +In addition, we should support anonymous/multiple choice groups. +We may need to refine the choice runtime structure +in order to allow multiple choice groups +to be inlined into parent elements. +Here is an example schema +and corresponding C code to demonstrate: + +[source,xml] +---- + <xs:complexType name="NestedUnionType"> + <xs:sequence> + <xs:element name="first_tag" type="idl:int32"/> + <xs:choice dfdl:choiceDispatchKey="{xs:string(./first_tag)}"> + <xs:element name="foo" type="idl:FooType" dfdl:choiceBranchKey="1 2"/> + <xs:element name="bar" type="idl:BarType" dfdl:choiceBranchKey="3 4"/> + </xs:choice> + <xs:element name="second_tag" type="idl:int32"/> + <xs:choice dfdl:choiceDispatchKey="{xs:string(./second_tag)}"> + <xs:element name="fie" type="idl:FieType" dfdl:choiceBranchKey="1"/> + <xs:element name="fum" type="idl:FumType" dfdl:choiceBranchKey="2"/> + </xs:choice> + </xs:sequence> + </xs:complexType> +---- + +[source,c] +---- +typedef struct NestedUnion +{ + InfosetBase _base; + int32_t first_tag; + size_t _choice_1; // choice of which union field to use + union + { + foo foo; + bar bar; + }; + int32_t second_tag; + size_t _choice_2; // choice of which union field to use + union + { + fie fie; + fum fum; + }; +} NestedUnion; +---- + +=== Arrays + +Instead of expanding arrays inline within childrenERDs, +we may want to store a single entry +for an array in childrenERDs +giving the array's offset and size of all its elements. +We would have to write code +for special case treatment of array member fields +versus scalar member fields +but we could save space/memory in childrenERDs +for use cases with very large arrays. +An array element's ERD should have minOccurs and maxOccurs +where minOccurs is unsigned +and maxOccurs is signed with -1 meaning "unbounded". +The actual number of children in an array instance +would have to be stored with the array instance +in the C struct or the ERD. +An array node has to be a different kind of infoset node +with a place for this number of actual children to be stored. +Probably all ERDs should just get minOccurs and maxOccurs +and a scalar is just one with 1, 1 as those values, +an optional element is 0, 1, +and an array is all other legal combinations +like N, -1 and N, and M with N<=M. +A restriction that minOccurs is 0, 1, +or equal to maxOccurs (which is not -1) +is acceptable. +A restriction that maxOccurs is 1, -1, +or equal to minOccurs +is also fine +(means variable-length arrays always have unbounded number of elements). Review Comment: Hmm, I must have written that down with the intention of simplifying the C code. However, I now think that all Daffodil implementations should enforce minOccurs <= count <= maxOccurs if the schema author picks a non-zero maxOccurs for security. If a network protocol wants to say this element array can hold from 0 to 16 integers, we should check these bounds if the runtime2 DFDL subset supports variable length arrays at all, yes? ########## site/dev/design-notes/runtime2-todos.adoc: ########## @@ -36,7 +36,108 @@ If someone wants to help please let the mailto:[email protected][dev] list know in order to avoid duplication. -=== Report hanging problem running sbt (really dev.dirs) from MSYS2 on Windows +=== Anonymous/multiple choice groups + +We already handle elements having xs:choice complex types. +In addition, we should support anonymous/multiple choice groups. +We may need to refine the choice runtime structure +in order to allow multiple choice groups +to be inlined into parent elements. +Here is an example schema +and corresponding C code to demonstrate: + +[source,xml] +---- + <xs:complexType name="NestedUnionType"> + <xs:sequence> + <xs:element name="first_tag" type="idl:int32"/> + <xs:choice dfdl:choiceDispatchKey="{xs:string(./first_tag)}"> + <xs:element name="foo" type="idl:FooType" dfdl:choiceBranchKey="1 2"/> + <xs:element name="bar" type="idl:BarType" dfdl:choiceBranchKey="3 4"/> + </xs:choice> + <xs:element name="second_tag" type="idl:int32"/> + <xs:choice dfdl:choiceDispatchKey="{xs:string(./second_tag)}"> + <xs:element name="fie" type="idl:FieType" dfdl:choiceBranchKey="1"/> + <xs:element name="fum" type="idl:FumType" dfdl:choiceBranchKey="2"/> + </xs:choice> + </xs:sequence> + </xs:complexType> +---- + +[source,c] +---- +typedef struct NestedUnion +{ + InfosetBase _base; + int32_t first_tag; + size_t _choice_1; // choice of which union field to use + union + { + foo foo; + bar bar; + }; + int32_t second_tag; + size_t _choice_2; // choice of which union field to use + union + { + fie fie; + fum fum; + }; +} NestedUnion; +---- + +=== Arrays + +Instead of expanding arrays inline within childrenERDs, +we may want to store a single entry +for an array in childrenERDs +giving the array's offset and size of all its elements. Review Comment: Yes, total size of all its elements makes more sense. ########## site/dev/design-notes/runtime2-todos.adoc: ########## @@ -36,7 +36,108 @@ If someone wants to help please let the mailto:[email protected][dev] list know in order to avoid duplication. -=== Report hanging problem running sbt (really dev.dirs) from MSYS2 on Windows +=== Anonymous/multiple choice groups + +We already handle elements having xs:choice complex types. +In addition, we should support anonymous/multiple choice groups. Review Comment: I'm fine with that interpretation too. I've revised this todo to say if you write your schema with anonymous choices, it won't be allowed, and you will have to replace your anonymous choices with named elements holding choice groups instead. ########## site/dev/design-notes/runtime2-todos.adoc: ########## @@ -52,7 +153,8 @@ coursier picks up the new directories version, sbt picks up the new coursier version, and daffodil picks up the new sbt version, before we can remove the "echo >> $GITHUB_ENV" lines -from .github/workflows/main.yml. +from .github/workflows/main.yml +which prevent the sbt hanging problem. Review Comment: No, I believe you're right that a deterministic subset of DFDL is still the target for runtime2. I don't think we are ever going to need backtracking or forward speculation for typical binary network protocols, since these protocols are designed for programs to read them easily. It seems only certain text and binary file formats will need DFDL's full power (especially text since text can be more ambiguous than binary). ########## site/dev/design-notes/runtime2-todos.adoc: ########## @@ -36,7 +36,108 @@ If someone wants to help please let the mailto:[email protected][dev] list know in order to avoid duplication. -=== Report hanging problem running sbt (really dev.dirs) from MSYS2 on Windows +=== Anonymous/multiple choice groups + +We already handle elements having xs:choice complex types. +In addition, we should support anonymous/multiple choice groups. +We may need to refine the choice runtime structure +in order to allow multiple choice groups +to be inlined into parent elements. +Here is an example schema +and corresponding C code to demonstrate: + +[source,xml] +---- + <xs:complexType name="NestedUnionType"> + <xs:sequence> + <xs:element name="first_tag" type="idl:int32"/> + <xs:choice dfdl:choiceDispatchKey="{xs:string(./first_tag)}"> + <xs:element name="foo" type="idl:FooType" dfdl:choiceBranchKey="1 2"/> + <xs:element name="bar" type="idl:BarType" dfdl:choiceBranchKey="3 4"/> + </xs:choice> + <xs:element name="second_tag" type="idl:int32"/> + <xs:choice dfdl:choiceDispatchKey="{xs:string(./second_tag)}"> + <xs:element name="fie" type="idl:FieType" dfdl:choiceBranchKey="1"/> + <xs:element name="fum" type="idl:FumType" dfdl:choiceBranchKey="2"/> + </xs:choice> + </xs:sequence> + </xs:complexType> +---- + +[source,c] +---- +typedef struct NestedUnion +{ + InfosetBase _base; + int32_t first_tag; + size_t _choice_1; // choice of which union field to use + union + { + foo foo; + bar bar; + }; + int32_t second_tag; + size_t _choice_2; // choice of which union field to use + union + { + fie fie; + fum fum; + }; +} NestedUnion; +---- + +=== Arrays + +Instead of expanding arrays inline within childrenERDs, +we may want to store a single entry +for an array in childrenERDs +giving the array's offset and size of all its elements. +We would have to write code +for special case treatment of array member fields +versus scalar member fields +but we could save space/memory in childrenERDs Review Comment: Do you think array ERDs might also help us implement dynamically sized arrays with dfdl:lengthKind = "expression" and dfdl:count = { ../count } in generated C code? ########## site/dev/design-notes/runtime2-todos.adoc: ########## @@ -109,141 +211,26 @@ and try the parse call again as an attempt to resynchronize with a correct data stream after a bunch of failures. -Note that we actually run the generated code in an embedded processor +Note that we sometimes run the generated code in an embedded processor and call our own fread/frwrite functions which replace the stdio fread/fwrite functions since the C code runs bare metal without OS functions. -We can implement fseek but we should have a good use case. - -=== Javadoc-like tool for C code - -We should consider adopting one of the javadoc-like tools for C code -and structuring our comments that way. +We can implement the fseek function on the embedded processor too +but we would need a good use case requiring recovering after errors. === Validate "fixed" values in runtime1 too If we change runtime1 to validate "fixed" values like runtime2 does, then we can resolve https://issues.apache.org/jira/browse/DAFFODIL-117[DAFFODIL-117]. -=== Improve TDML Runner - -We want to improve the TDML Runner -to make it easier to run TDML tests -with both runtime1 and runtime2. -We want to eliminate the need -to configure a `daf:tdmlImplementation` tunable -in the TDML test using 12 lines of code. - -I had an initial idea which was that -the TDML Runner could run both runtime1 and runtime2 -automatically (in parallel or serially) -if it sees a TDML root attribute -saying `defaultImplementations="daffodil daffodil-runtime2"` -or a parser/unparseTestCase attribute -saying `implementations="daffodil daffodil-runtime2"`. -To make running the same test on runtime1/runtime2 easier -we also could add an implementation attribute -to tdml:errors/warnings elements -saying which implementation they are for -and tell the TDML Runner to check errors/warnings -for runtime2 as well as runtime1. - -Then I had another idea which might be easier to implement. -If we could find a way to set Daffodil's tdmlImplementation tunable -using a command line option or environment variable -or some other way to change TDML Runner's behavior -when running both "sbt test" and "daffodil test" -then we could simply run "sbt test" or "daffodil test" twice -(first using runtime1 and then using runtime2) -in order to verify all the cross tests work on both. -I think this way would be easier than making TDML Runner -automatically run all the implementations it can find -in parallel or serially when running cross tests. - -If the second idea works as I hope it does, -then we can start the process of adding "daffodil-runtime2" -to some of the cross tests we have for daffodil and ibm. -We also chould change ibm's ProcessFactory class -to have a different name than daffodil's ProcessFactory class -and update TDML Runner's match expression to use the new class name. -Then some developers could add the ibmDFDLCrossTester plugin -to their daffodil checkout permanently -instead of having to do & undo that change -each time they want to run daffodil/ibm cross tests. - -=== C struct/field name collisions - -To avoid possible name collisions, -we should prepend struct names and field names with namespace prefixes -if their infoset elements have non-null namespace prefixes. -Alternatively, we may need to use enclosing elements' names -as prefixes to avoid name collisions without namespaces. - -=== Anonymous/multiple choice groups - -We already handle elements having xs:choice complex types. -In addition, we should support anonymous/multiple choice groups. -We may need to refine the choice runtime structure -in order to allow multiple choice groups -to be inlined into parent elements. -Here is an example schema -and corresponding C code to demonstrate: - -[source,xml] ----- - <xs:complexType name="NestedUnionType"> - <xs:sequence> - <xs:element name="first_tag" type="idl:int32"/> - <xs:choice dfdl:choiceDispatchKey="{xs:string(./first_tag)}"> - <xs:element name="foo" type="idl:FooType" dfdl:choiceBranchKey="1 2"/> - <xs:element name="bar" type="idl:BarType" dfdl:choiceBranchKey="3 4"/> - </xs:choice> - <xs:element name="second_tag" type="idl:int32"/> - <xs:choice dfdl:choiceDispatchKey="{xs:string(./second_tag)}"> - <xs:element name="fie" type="idl:FieType" dfdl:choiceBranchKey="1"/> - <xs:element name="fum" type="idl:FumType" dfdl:choiceBranchKey="2"/> - </xs:choice> - </xs:sequence> - </xs:complexType> ----- - -[source,c] ----- -typedef struct NestedUnion -{ - InfosetBase _base; - int32_t first_tag; - size_t _choice_1; // choice of which union field to use - union - { - foo foo; - bar bar; - }; - int32_t second_tag; - size_t _choice_2; // choice of which union field to use - union - { - fie fie; - fum fum; - }; -} NestedUnion; ----- - -=== Choice dispatch key expressions - -We currently support only a very restricted -and simple subset of choice dispatch key expressions. -We would like to refactor the DPath expression compiler -and make it generate C code -in order to support arbitrary choice dispatch key expressions. - === No match between choice dispatch key and choice branch keys -Right now c-daffodil is more strict than scala-daffodil +Right now c/daffodil is more strict than daffodil when unparsing infoset XML files with no matches (or mismatches) between choice dispatch keys and branch keys. -Perhaps c-daffodil should load such an XML file +Such a situation always makes c/daffodil exit with an error. +Perhaps c/daffodil should load such an XML file Review Comment: I take it that you agree the C unparse code should process an XML infoset without any "no match" errors, even if the choiceDispatchKey is invalid. I also take it that the C unparse code should not modify the choiceDispatchKey either. If the schema writer wants to enforce that the choiceDispatchKey is the right one matching the unparsed choice branch, the writer must write the dfdl:outputValueCalc to ensure this. ########## site/dev/design-notes/runtime2-todos.adoc: ########## @@ -36,7 +36,108 @@ If someone wants to help please let the mailto:[email protected][dev] list know in order to avoid duplication. -=== Report hanging problem running sbt (really dev.dirs) from MSYS2 on Windows +=== Anonymous/multiple choice groups + +We already handle elements having xs:choice complex types. +In addition, we should support anonymous/multiple choice groups. +We may need to refine the choice runtime structure +in order to allow multiple choice groups +to be inlined into parent elements. +Here is an example schema +and corresponding C code to demonstrate: + +[source,xml] +---- + <xs:complexType name="NestedUnionType"> + <xs:sequence> + <xs:element name="first_tag" type="idl:int32"/> + <xs:choice dfdl:choiceDispatchKey="{xs:string(./first_tag)}"> + <xs:element name="foo" type="idl:FooType" dfdl:choiceBranchKey="1 2"/> + <xs:element name="bar" type="idl:BarType" dfdl:choiceBranchKey="3 4"/> + </xs:choice> + <xs:element name="second_tag" type="idl:int32"/> + <xs:choice dfdl:choiceDispatchKey="{xs:string(./second_tag)}"> + <xs:element name="fie" type="idl:FieType" dfdl:choiceBranchKey="1"/> + <xs:element name="fum" type="idl:FumType" dfdl:choiceBranchKey="2"/> + </xs:choice> + </xs:sequence> + </xs:complexType> +---- + +[source,c] +---- +typedef struct NestedUnion +{ + InfosetBase _base; + int32_t first_tag; + size_t _choice_1; // choice of which union field to use Review Comment: Yes, you're right that it's actually not obvious whether an index (which is what _choice represents) should be signed or unsigned. I had thought _choice should be unsigned to avoid cutting the usable range in half and it should be size_t because size_t is the maximum allowable length of any type of C array. However, I've googled and found out that people have equally compelling reasons why indices should be signed instead of unsigned as well (<https://www.quora.com/Why-is-size_t-sometimes-used-instead-of-int-for-declaring-an-array-index-in-C-Is-there-any-difference>). There appears to be no One Right Answer what type _choice should have and using `choice_t` would allow us to change the definition in one place if we needed to. I've added a todo about using `choice_t` instead of `size_t`. ########## site/dev/design-notes/runtime2-todos.adoc: ########## @@ -36,7 +36,108 @@ If someone wants to help please let the mailto:[email protected][dev] list know in order to avoid duplication. -=== Report hanging problem running sbt (really dev.dirs) from MSYS2 on Windows +=== Anonymous/multiple choice groups + +We already handle elements having xs:choice complex types. +In addition, we should support anonymous/multiple choice groups. +We may need to refine the choice runtime structure +in order to allow multiple choice groups +to be inlined into parent elements. +Here is an example schema +and corresponding C code to demonstrate: + +[source,xml] +---- + <xs:complexType name="NestedUnionType"> + <xs:sequence> + <xs:element name="first_tag" type="idl:int32"/> + <xs:choice dfdl:choiceDispatchKey="{xs:string(./first_tag)}"> + <xs:element name="foo" type="idl:FooType" dfdl:choiceBranchKey="1 2"/> + <xs:element name="bar" type="idl:BarType" dfdl:choiceBranchKey="3 4"/> + </xs:choice> + <xs:element name="second_tag" type="idl:int32"/> + <xs:choice dfdl:choiceDispatchKey="{xs:string(./second_tag)}"> + <xs:element name="fie" type="idl:FieType" dfdl:choiceBranchKey="1"/> + <xs:element name="fum" type="idl:FumType" dfdl:choiceBranchKey="2"/> + </xs:choice> + </xs:sequence> + </xs:complexType> +---- + +[source,c] +---- +typedef struct NestedUnion +{ + InfosetBase _base; + int32_t first_tag; + size_t _choice_1; // choice of which union field to use + union + { + foo foo; + bar bar; + }; + int32_t second_tag; + size_t _choice_2; // choice of which union field to use + union + { + fie fie; + fum fum; + }; +} NestedUnion; +---- + +=== Arrays + +Instead of expanding arrays inline within childrenERDs, +we may want to store a single entry +for an array in childrenERDs +giving the array's offset and size of all its elements. +We would have to write code +for special case treatment of array member fields +versus scalar member fields +but we could save space/memory in childrenERDs +for use cases with very large arrays. +An array element's ERD should have minOccurs and maxOccurs +where minOccurs is unsigned +and maxOccurs is signed with -1 meaning "unbounded". +The actual number of children in an array instance +would have to be stored with the array instance +in the C struct or the ERD. +An array node has to be a different kind of infoset node +with a place for this number of actual children to be stored. +Probably all ERDs should just get minOccurs and maxOccurs +and a scalar is just one with 1, 1 as those values, Review Comment: What do you mean by storing more ERD pointers in parent ERDs? I've been thinking of minOccurs, maxOccurs, count, but pointers to where? Dynamically sized arrays instance info, if more than a handful, won't fit into C structs and would have to be dynamically allocated, but that's instance info, not ERD metadata. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
