EPICS: dbdClasses - IOC record

June 17 2005

Overview

UNDER CONSTRUCTION

This document describes the C++ class definitions for code that implements the semantics for records created from Database Definitions. The definitions are intended for code that:

includes header files generated from dbd definitions. Header files are generated from the following dbd definitions:
- record - Should only be included by record support.
- struct - Included by code that understands the struct.
- menu - Included by code that understands the menu.
does not include the header files.

The following headers files are described:

dbfTypes.h - Type definitions for field definitions in struct or record> DBD definitions.
dbdStatements.h - Type definitions for DBD statements.
dbdInterfaces.h - Type definitions for interfaces related to DBD definitions.

dbfTypes

File dbfTypes.h describes types and classes that are used in header files generated from dbd struct or record field definitions. The following naming conventions are used:

C++ struct vs class: A C++ class is used for a class that has methods and struct is used for a class that has only data.
Dbf: any class starting with Dbf describes a field in a generated header file. For example DbfString describes a field generated from field(name,string).
Dbd: A class name starting with Dbd describes something related to dbd definitions. For example DbdLinkSupport describes a dbd link definition.

`dbfTypes.h`

Every field in the header files generated from DBD struct and record definitions has one on the following types:

    enum dbfType {
        dbfTypeBoolean,     // epicsBoolean
        dbfTypeOctet,       // epicsOctet
        dbfTypeInt16,       // epicsInt16
        dbfTypeInt32,       // epicsInt32
        dbfTypeInt64,       // epicsInt64
        dbfTypeFloat32,     // epicsFloat32
        dbfTypeFloat64,     // epicsFloat64
        dbfTypeString,      // EpicsString
        dbfTypeArray,       // DbfArray
        dbfTypeMDArray      // DbfMDArray
        dbfMenuT,           // DbfMenu
        dbfEnumT,           // DbfEnum
        dbfLinkT,           // DbfLink
        dbfDeviceT          // DbfDevice
        dbfTypeStruct,      // DbfStruct
    };

Discussion of dbfTypes

DBD type

bool,...,string all become an epicsType , i.e. epicsBoolean,...EpicsString
array becomes a DbfArray or DbfMDArray.
struct becomes a DbfStruct
menu becomes DbfMenu
enum becomes DbfEnum
link becomes DbfLink
device becomes DbfDevice

If a record is defined as:

    struct(displayLimits) {
        field(low,double)
        field(high,double)
    }
    record(xxx) extends iocRecord {
        ...
        field(fbool,bool)
        field(foctet,octet)
        field(fint,int16)
        ...
        field(ffloat,float64)
        field(fstring,string)
        field(array,array(double[])
        field(mdarray,array(double[,])
        field(fmenu,menu(name))
        field(fenum,enum)
        field(flink,link(in))
        field(fdevice,link(in,analogIO))
        field(displayLimits,struct(displayLimits))
    }

Then the generated header file will be

    class xxxRecord : public iocRecord {
    public:
        epicsBoolean fbool;
        epicsOctet   foctet;
        epicsInt16   fint;
        ...
        epicsFloat64 ffloat;
        EpicsString  fstring;
        DbfArray     array;
        DbfMDArray   mdarray;
        DbfMenu      fmenu;
        DbfEnum      fenum;
        DbfLink      flink;
        DbfDevice    fdevice;
        DbfStruct    displayLimits;
   };

epicsTypes

Fields of type epicsBoolean, epicsOctet, epicsInt16, epicsInt32, epicsInt64, epicsFloat32, or epicsFloat64 are all a C++ fundamental type. When a record instance is created these are all initialized to 0.

A field of type EpicsString is initialized via the default constructor for EpicsString, which means that no EpicsBuffer is created. Record support must call createBuffer.

DbfArray

DbfArray is:

    class DbfArray : protected EpicsArray {
    public:
        DbfArray(dbfType type = dbfTypeOctet);
        DbfArray(const char *bufferType,
                  dbfType type = dbfTypeOctet, epicsInt32 capacity = 0);
        DbfArray(DbfBufferCreator *creator,
                  dbfType type = dbfTypeOctet, epicsInt32 capacity = 0);
        ~DbfArray();
        void setType(dbfType type);
        dbfType getType() const;
        void createBuffer(const char *bufferType, epicsInt32 capacity = 0);
        void createBuffer(DbfBufferCreator *creator, epicsInt32 capacity = 0);
        DbfBufferCreator *creator() const;
        void destroyBuffer();
        epicsOctet *element(epicsInt32 index);
        const epicsOctet *element(epicsInt32 index) const;
        epicsInt32 get(epicsInt32 offset, epicsInt32 len,
                       epicsOctet *pto) const;
        epicsInt32 put(epicsInt32 offset, epicsInt32 len,
                       const epicsOctet *pfrom);
        bool mutable() const;
        // These are similar to DbfBuffer, measured in elements not octets
        void reserve(epicsInt32 capacity);
        epicsInt32 capacity() const;
        void resize(epicsInt32 newsize);
        epicsInt32 size() const;
        epicsInt32 maxSize() const;
        void expose(epicsInt32 offset, epicsInt32 &len,
                    epicsOctet *&pdata);
        void expose(epicsInt32 offset, epicsInt32 &len,
                    const epicsOctet *&pdata) const;
    protected:
        dbfType type;
    private:
        DbfArray(const DbfArray &);            // No copy constructor
        DbfArray& operator=(const DbfArray &); // No assignment operator
    };

QUESTIONS:

# should operator = be allowed?
# should EpicsArray provide convience wrappers for basic types

In addition convenience classes are available for each dbfType. They provide a type safe wrapper the has a reference to a DbfArray. The convience classes are:

    class Int16Array {
    public:
        Int16Array(DbfArray &array);
        Int16Array(DbfArray &array,
                   const char *bufferType, epicsInt32 capacity = 0);
        Int16Array(DbfArray &array
                   EpicsBufferCreator *creator, epicsInt32 capacity = 0);
        ~Int16Array();
        void createBuffer(const char *bufferType, epicsInt32 capacity = 0);
        void createBuffer(DbfBufferCreator *creator, epicsInt32 capacity = 0);
        DbfBufferCreator *creator() const;
        epicsInt16 *element(epicsInt32 index);
        const epicsInt16 *element(epicsInt32 index) const;
        epicsInt32 get(epicsInt32 offset, epicsInt32 len,
                       epicsInt16 *pto) const;
        epicsInt32 put(epicsInt32 offset, epicsInt32 len,
                       const epicsInt16 *pfrom);
        bool mutable() const;
        void reserve(epicsInt32 capacity);
        epicsInt32 capacity() const;
        void resize(epicsInt32 newsize);
        epicsInt32 size() const;
        epicsInt32 maxSize() const;
        void expose(epicsInt32 offset, epicsInt32 &len,
                    epicsInt16 *&pdata);
        void expose(epicsInt32 offset, epicsInt32 &len,
                    const epicsInt16 *&pdata) const;
    private:
        DbfArray &array;
        Int16Array(); // No default constructor
        Int16Array(const EpicsInt16Array &); // No copy constructor
        Int16Array& operator=(const EpicsInt16Array &); // No assignment operator
    };

    // The following are like Int16Array except for type
    class OctetArray ;
    class Int32Array ;
    class Int64Array ;
    class Float32Array ;
    class Float64Array ;
    class StringArray ;
    class StructArray ;

As an example of how the convience classes are used is:

    DbfArray  dbfArray;
    ...
    Float64Array floatArray(dbfArray);

    epicsFloat64 *pdata = new epicsFloat64[10];
    ...
    floatArray.put(0,10,pdata);

DbfMDArray

DbfMDArray is:

Need something like for DbfArray except that convenience classes will be

    class BasicTypeMDArray;
    class OctetMDArray ;
    class Int32MDArray ;
    class Int64MDArray ;
    class Float32MDArray ;
    class Float64MDArray ;

DbfMenu

DbfMenu is described as:

    class DbfMenu{
    public:
        DbfMenu(DbdMenu &menu);
        epicsInt16 nChoices();
        EpicsString &choice() const;
        EpicsString &choice(epicsInt16 index) const;
        epicsInt16 getIndex() const;
        void setIndex(epicsInt16 index) const;
        EpicsEnumChoices &choices() const;
        DbdMenu &menu() const;
    private:
        epicsInt16    index;
        DbdMenu  &menuDef;
        DbfMenu(); // no default constructor
    };

DbfMenu provides the current menu index and also a reference to the associated DbDMenu.

Questions

Is this how we want to do this?

The constructor for the record type must also construct a DbfMenu.

DbfEnum

DbfEnum is described as:

    class DbfEnum{
    public:
        DbfEnum(DbfArray &field);
        epicsInt16 nChoices();
        EpicsString &choice() const;
        EpicsString &choice(epicsInt16 index) const;
        epicsInt16 getIndex() const;
        void setIndex(epicsInt16 index) const;
        EpicsEnumChoices &choices() const;
    private:
        epicsInt16    index;
        EpicsEnumChoices *pEpicsEnumChoices;
        DbfEnum(); // no default constructor
    };

The only way to create a DbfEnum is to pass it a reference to a field that is a DbfArray with type EpicsString.

DbfLink and DbdDevice

DbfLink is described as

    enum LinkDir {
        LinkDirNone,
        LinkDirForward,
        LinkDirIn,
        LinkDirOut,
        LinkDirInOut
    };
   
    struct DbfLink{ 
        LinkDir   dir;
        DbdLink   *plinkDef;
        DbfStruct dataStruct;
    };
   
    struct DbfDevice{
        LinkDir   dir;
        DbdDevice *pDbdDevice;
        DbfStruct dataStruct;
    };

The fields of DbfLink are initialized by dbLoadRecords as follows:

dir: This is taken from either the field definition or from the DbdLink definition and is the most restrictive. For example if one says inout and the other says in then dir will be in.
plinkDef: This is the address of the DbdLink.
dataStruct: The describes the data structure specified in the dbd link definition. It contains data used by the link support.

Link support always implements interface DbdLinkSupport

A DbfDevice is similar to a DbfLink except that the interface implemented by the device support is also specified, i.e. instead of implementing interface DbdLinkSupport, the device support implements an interface that both record support and device support understand.

DbfStruct

DbfStruct is described as

    struct DbfStruct {
        DbdStruct *pdescription;
        void      *pstorage;
    };

The fields of DbfStruct are initialized by dbLoadRecords as follows:

pdescription: This is initialized via the structure name specified in field definition.
pstorage: This is initialized by calling DbdStructLifetime:allocate

dbdStatementsThe definitions in dbdStatements.h allow introspection of ioc records. They describe everything defined in DBD definitions. NODE and LIST specify a doubly linked list. An implementation is not specified.dbdStatements.hclass Interface {}; // Must be an interface, i.e. pure abstract classclass DbdMenu{ public: DbdMenu(EpicsEnumChoices &choices); epicsInt16 nChoices(); EpicsString &choice(epicsInt16 index); EpicsEnumChoices &choices() const { return choices;} private: ~DbdMenu(); // Who can call this? NODE node; // for DbdBase:menuList EpicsEnumChoices &choices; DbdMenu(); // No default constructor }; class DbdLink{ //describes dbd link statement public: DbdLink(LinkDir,EpicsString &choice,EpicsString &dataStruct); static registerInterface(const EpicsString &choice,LinkDir dir, DbdLinkSupport &support); LinkDir dir(); EpicsString &choiceName(); EpicsString &dataStructName(); DbdLinkSupport *pinterface(); private: NODE node; // For DbdBase:linkList LinkDir dir; EpicsString choiceName; EpicsString dataStructName; DbdLinkSupport *pinterface; }; struct DbdDevice { //describes dbd device statement NODE node; // For DbdBase:deviceList LinkDir dir; EpicsString choiceName; EpicsString dataStructName; EpicsString interfaceName; Interface *pinterface; };// Beginning of definitions for DbdStruct struct DbdAttribute { EpicsString default; epicsBoolean readonly; epicsBoolean design; epicsBoolean special; epicsBoolean dynamic; epicsInt16 asl; };struct DbdStringDefaults { // defaults for string const char *bufferType; epicsInt32 capacity; };struct DbdArrayDefaults { // defaults for array dbfType type; const char *bufferType; epicsInt32 capacity; epicsInt32 nelements; };struct DbdMDArrayDefaults { // defaults for mdarray dbfType type; epicsInt16 ndim const char *bufferType; epicsInt32 capacity; };struct DbdStructDefaults { // defaults for struct DbdStruct *pdescription; };struct DbdField { const char *name; dbfType type; union { DbdStringDefaults *pstring; DbdArrayDefaults *parray; DbdMDArrayDefaults *pmdarray; DbdStructDefaults *pstruct; } defaults; DbdAttribute attribute; };struct DbdStruct{ // describes a struct NODE node; // for DbdBase:structList const char *name; epicsInt16 nfields; DbdField *pafield;//ptr to array of DbdField DbdStructLifetime *plifetime; };struct DbdRecord { // describes a record NODE node; // for DbdBase:recordList LIST instanceList; const char *name; epicsInt16 nfields; DbdField *pafield;//ptr to array of DbdField DbdRecordSupport *psupport; DbdRecordLifetime *plifetime; }; struct DbdUserField{ // describes a dbd userField statement NODE node; // For DbdBase:userFieldList EpicsString choiceName; epicsType type; EpicsString dataStructName; DbdUserFieldHandler *pinterface; }; // The following describes a record instance struct DbdUserFieldInstance { NODE node; // for DbdRecordInstance.userField EpicsString name; // user field name dbfType sourceType; void *psource; DbdUserField *pDbdUserField; void *pstorage; // for DbdUserField.type DbfStruct dataStruct; }; struct DbdRecordInstance { NODE node; // for DbdRecord.instanceList DbdRecord *pDbdRecord; void *pstorage; EpicsString name; LIST userField; // of DbdUserFieldInstance }; struct DbdBase { LIST structList; LIST recordList; LIST menuList; LIST linkList; LIST deviceList; LIST userFieldList; };Discussion of dbdStatementsGENERIC QUESTIONS:NODE - how should we handle lists?MenuA dbd menu is described by DbdMenu The methods of DbdMenu are:DbdMenu The only way to create a DbdMenu is via a reference to the EpicsEnumChoices for the menu. Thus the choices must be created first. ~DbdMenu destructor. Who can call this? nchoices returns the number of choices. choice returns a reference to the choice. choices returns a reference to the EpicsEnumChoicesQUESTIONS about DbdMenuThe current definition does not allow the choices to be modified. Is it required that we can change them? Can they be changed AFTER a database is loaded and initialized? Who can call destructor?LinkA dbd link definition is described by DbdLinknode This is a node for DbdLinkList dir The link direction choiceName The name that connects a DbdLink to a DbfLink instance. dataStructName The class name of an DbdStruct for the Interface implementation pinterface The address of the DbdLinkSupport Interface implementation.DeviceEach dbd device definition is described by DbdDevicenode This is a node for DbdDeviceList dir The link direction choiceName The name that matches a DbdDevice to a DbfDevice instance. dataStructName The class name of an EpicsStruct for the Interface implementation interfaceName The name of the interface type implemented by the device support pinterface The address of the Interface implementation.struct and recordThe following describe the fields in a dbd struct or record definition: DbdStruct, DbdRecord, DbdField,and DbdAttribute The fields of DbdStruct are:node node for DbdBase:structList name The name of the struct. nfields The number of fields, e.g. fields in the structure. pafields pointer to an array of DbdField. plifetime The address of an implementation of interface DbdStructLifetime. The implementation is automatically generated from the dbd struct. See below for a description of the Lifetime methods.The fields of DbdRecord are;node node for DbdBase:recordList instanceList list of instances of this record type name The name of the record type. nfields The number of fields, e.g. fields in the record. pafields pointer to an array of DbdField. psupport The address of the DbdRecordSupport for this record type. plifetime The address of an implementation of interface DbdRecordLifetime. The implementation is automatically generated from the dbd record statement. See below for a description of the Lifetime methods.The fields of DbdField are:name The name of the field type The dbfType of the field. defaults a union of default values. The default values depend on the record type definitions. Most types do not have associated default values. Note that these are defaults for the description of the field NOT for values to put in the field. attribute DbdAttribute for the fieldThe fields of DbdAttribute are:default An EpicsString providing a default value for the field. readonly Is the field readonly? design Is the field a design fields for DCTs? special Should DbdRecordSupport:special be called if the field is modified. dynamic Can the field change because of record processing? asl The access security level.User Defined FieldsEach dbd userField definition has an associated class DbdUserField with fields:node This is a node for DbdUserFieldList choiceName The name that matches a DbdUserField to a DbdUserFieldInstance type The epicsType for the user field dataStructName The class name of an EpicsStruct for the DbdUserFieldHandler pinterface The address of the DbdUserFieldHandler implementation.Record InstanceA record instance has two associated classes:DbdUserFieldInstance and DbdRecordInstance. DbdUserFieldInstance contains information for a user defined field:node A node for list DbdRecordInstance.userField name The name of the user defined field, i.e. the psuedo field name sourceType the type of the field of the record that DbdUserFieldHandler accesses. psource The address of the field that DbdUserFieldHandler accesses. pDbdUserField The DbdUserField that describes the field pstorage Address of storage for the dbfType. dataStruct An DbfStruct that holds the private data for the DbdUserFieldHandler.The fields of DbdRecordInstance are:node A node for list DbdRecord.instanceList pDbdRecord address of the DbdRecord describing the record pstorage address of the storage for the record instance name The name of the record instance userField DbdUserFieldInstance list for the record instance.DbdBaseThe following provide lists of various things:structList The list of each struct definition recordList The list of each record type definition menuList The list of each menu definition linkList The list of each link definition deviceList The list of each device definition userFieldList The list of each DbdUserField definitiondbdInterfaces dbdInterfaces describes standard interfaces implemented by code that supports runtime database access.dbdInterfaces.hdbdInterfaces.h contains the following:// The following is implemented by database access class DbdFieldPutString { virtual void primitive(EpicsString *pfrom, dbfType type, void *pstorage) = 0; virtual void string(EpicsString *pfrom, EpicsString *pEpicsString) = 0; virtual void array(EpicsString *pfrom, DbfArray *parray) = 0; virtual void dbfStruct(EpicsString *pfrom, DbfStruct *pstruct) = 0; virtual void dbfMDArray(EpicsString *pfrom, DbfMDArray *parray) = 0; }// For struct definitions // An DbdStructLifetime interface is automatically generated. class DbdStructLifetime { public: virtual void allocate(DbfStruct &struct) = 0; virtual void destroy(DbfStruct &struct) = 0; virtual bool initialize(DbfStruct *pDbfStruct) = 0; virtual bool finalize(DbfStruct *pDbfStruct) = 0; virtual void *exposeField(DbfStruct &struct, epicsInt16 index) = 0; };// For record definitions a DbdRecordLifetime is automatically generated. class DbdRecordLifetime{ public: virtual void allocate(DbdRecordInstance *pDbdRecordInstance) = 0; virtual void destroy(DbdRecordInstance *pDbdRecordInstance) = 0; virtual bool initialize(DbdRecordInstance *pDbdRecordInstance) = 0; virtual bool finalize(DbdRecordInstance *pDbdRecordInstance) = 0; virtual void *exposeField(DbdRecordInstance *pDbdRecordInstance) = 0; };// link support modules implement the following interface class DbdLinkSupport { public: virtual void report(iocRecord *precord, DbfLink *pdbfLink) = 0; virtual bool initialize(iocRecord *precord, DbfLink *pdbfLink) = 0; virtual bool finalize(iocRecord *precord, DbfLink *pdbfLink) = 0; virtual bool connect(iocRecord *precord, DbfLink *pdbfLink) = 0; virtual bool disconnect(iocRecord *precord, DbffLink *pdbfLink) = 0; virtual bool get(iocRecord *precord, DbffLink *pdbfLink, epicsType type, void *pfield) = 0; virtual bool put(iocRecord *precord, DbfLink *pdbfLink, epicsType type, void *pfield) = 0; };/* record support implements the following*/ class DbdRecordSupport { public: virtual bool initBuffers(DbdRecordInstance *pDbdRecordInstance) = 0; virtual bool initConnections(DbdRecordInstance *pDbdRecordInstance) = 0; virtual bool breakConnections(DbdRecordInstance *pDbdRecordInstance) = 0; virtual bool process(DbdRecordInstance *pDbdRecordInstance) = 0; virtual void special(DbdRecordInstance *pDbdRecordInstance, bool after, epicsInt16 nlevels, // number of elements in fieldIndex epicsInt16 fieldIndex[] // array of field indices ) = 0; };class DbdUserFieldHandler { public: virtual bool initialize( iocRecord *precord,DbdUserFieldInstance *puserField) = 0; virtual bool finalize( iocRecord *precord,DbdUserFieldInstance *puserField) = 0; virtual bool process( iocRecord *precord,DbdUserFieldInstance *puserField) = 0; };Discussion of dbdInterfacesDbdFieldPutStringThis is an interface, which has an implementation provided by iocCore, that convert an EpicsString to an dbfType. The methods are:primitive This convert a string to one of the types: epicsBoolean, ..., epicsFloat64 string Copies an EpicsString to an EpicsString array Accepts a string that has the DBD array initialization syntax, locates the string value for each element and calls either DbdFieldPutString:primitive or DbdFieldPutString:string to convert the value and put it into the correct element of DbfArray dbfStruct Accepts a string that has the DBD struct initialialization syntax, locates the string value associated with each field and calls primitive, string, or array to convert the value and put the result of the correct field of DbfStruct dbfMDArray Accepts a string that has the DBD array initialization syntax, locates the string value for each element and calls either DbdFieldPutString:primitive or DbdFieldPutString:string to convert the value and put it into the correct element of DbfMDArrayDbdStructLifetime and DbdRecordLifetimeEvery dbd struct and record has an associated Lifetime interface implementation. A tool is provided that automatically generates the implementation from the dbd definition. DbdStructLifetime and DbdRecordLifetime each has the following fields:allocate Creates storage for the struct or record. destroy frees storage exposeField Given an index it returns the address of the storage for the field. Note the the generated header files assign an index to each field. initialize initializes the struct or record finalize cleans up but does not free storageDbdLinkSupportThis is the interface implemented by the support associated with each DBD link. DbdLinkSupport has the following methods:report generate a report about the link instance initialize perform initialization but do not connect finalize undo initialization. It is assumed that disconnect has already been called. connect connect to external source of data disconnect disconnect from external source of data get get a value from the external source. type specified the field type and pfield is the address of where to store the data. put put a value from the external source. type specified the field type and pfield is the address of where to obtain the data.DbdRecordSupportThis is the interface implemented by each record support module. DbdRecordSupport has the following methods:initBuffers This is called during record initialization. It is responsible for creating the buffers associated with each string and array field. It may call associated support to do the initialization. initConnections This is called to connect to external sources. It may call associated support to make the connections. breakConnections This is called to disconnect to external sources. It may call associated support to break the connections. process Process the record. special This is called whenever an external source modifies a field with attribute special set to true.DbdUserFieldHandlerThis is the interface implemented by code for user extensible fields. DbdUserFieldHandler has the following fields:initialize Initialize the user field. finalize undo what was done during initialization process Called near the end of record processing just before monitors are handled.Device Support InterfacesMultiple interface definitions for device support will be defined. Record Support and device support must agree on which interface type is used for communication.

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V4 Design: dbdClass

EPICS: dbdClasses - IOC record

Overview

dbfTypes

dbfTypes.h

Discussion of dbfTypes

epicsTypes

DbfArray

DbfMDArray

DbfMenu

DbfEnum

DbfLink and DbdDevice

DbfStruct

dbdStatements

dbdStatements.h

Discussion of dbdStatements

Menu

Link

Device

struct and record

User Defined Fields

Record Instance

DbdBase

dbdInterfaces

dbdInterfaces.h

Discussion of dbdInterfaces

DbdFieldPutString

DbdStructLifetime and DbdRecordLifetime

DbdLinkSupport

DbdRecordSupport

DbdUserFieldHandler

Device Support Interfaces

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`dbfTypes.h`

`dbdStatements.h`

`dbdInterfaces.h`

`DbdFieldPutString`

`DbdStructLifetime` and `DbdRecordLifetime`

`DbdLinkSupport`

`DbdRecordSupport`

`DbdUserFieldHandler`