#include <DataType.h>
Part of API
DataType enumerates possible data types. While this enum is primarily used in the table system, some use of it is made elsewhere. Besides the enum itself, operator<< is defined for DataType; it prints a DataType in the form DataType=Bool.
Also, global functions are written which take a "const pointer to type" and return its DataType (TpOther if unknown). These functions can occasionally allow one to avoid a switch on type, and can be useful in constructing templated classes which are only valid for certain types.
Global functions are also provided which allow one to convert an array type to the equivalent scalar type and vice versa.
Warning: New data types should be added just before TpNumberOfTypes, and after all the existing enumerations, to avoid changing the number of an existing type which would cause misinterpretation of data types stored in existing files. Note also that if any new scalar and array types are added that this will break the exising isScalar, isArray, asScalar and asArray functions.
Tip: Data types long and unsigned long are not possible. The types Int and uInt are always 4 bytes, so long is not needed and may only cause confusion.
The simplest uses of the DataType enumeration and functions are fairly obvious, for example:
Double d; DataType type = whatType(&d); cout << type << endl; switch(type) { case TpChar: .\.. .\.. case TpDouble: .\.. }
A less obvious use is for "attaching" a templated object or function to a non-templated object in a safe way. For example:
class IntFloatContainer { public: Int intval; Float floatval; void *ptr(DataType type) { if (type == whatType(&intval)) return &intval; else if (type == whatType(&floatval)) return &floatval; else return 0; // Illegal type } }; template<class T> class ValueAccessor { public: ValueAccessor(IntFloatContainer *container) : container_p(container) { if (container_p->ptr(whatType(static_cast<T *>(0))) == 0) throw(AipsError("Illegal type.\..")); } T &value() { return *((T*)container_p->ptr(whatType(static_cast<T *>(0)))); } private: IntFloatContainer *container_p; };
So, this example provides a typesafe interface to values of only a small number of types (and it fairly gracefully allows additional types to be added; in particular the accessor class needs no modification). Techniques such as this are appropriate for situations where one needs to deal with many (but finite) numbers of types. For example, with FITS.
<linkfrom anchor="DataType" modules="Tables"> Enumeration of the <here>data types</here> in the table system </linkfrom>
Enumeration of the possible data types for keywords and table columns:
enum DataType {TpBool, TpChar, TpUChar, TpShort, TpUShort, TpInt, TpUInt, TpFloat, TpDouble, TpComplex, TpDComplex, TpString, TpTable, TpArrayBool, TpArrayChar, TpArrayUChar, TpArrayShort, TpArrayUShort, TpArrayInt, TpArrayUInt, TpArrayFloat, TpArrayDouble, TpArrayComplex, TpArrayDComplex, TpArrayString, TpRecord, TpOther, TpNumberOfTypes };
Definition at line 155 of file DataType.h.
Public Types | |
| enum | DataType |
Public Member Functions | |
| ostream & | operator<< (ostream &os, DataType type) |
| Write a formated representation (e.g., Type=Bool) of the given data type. | |
| Bool | isReal (DataType type) |
| It is sometimes useful to discover if a DataType represents a real numeric value (i.e., can it be cast to a Double?) This returns True for both real scalar and array type. | |
| Bool | isComplex (DataType type) |
| Returns True for Complex or DComplex scalar or array types. | |
| Bool | isNumeric (DataType type) |
| Returns True if the type is either Real or Complex/DComplex. | |
| DataType | whatType (const void *) |
| These (overloaded) functions return DataType that corresponds to to the type that is being pointed at. | |
| DataType | whatType (const Bool *) |
| DataType | whatType (const Char *) |
| DataType | whatType (const uChar *) |
| DataType | whatType (const Short *) |
| DataType | whatType (const uShort *) |
| DataType | whatType (const Int *) |
| DataType | whatType (const uInt *) |
| DataType | whatType (const float *) |
| DataType | whatType (const double *) |
| DataType | whatType (const Complex *) |
| DataType | whatType (const DComplex *) |
| DataType | whatType (const String *) |
| DataType | whatType (const Table *) |
| DataType | whatType (const Array< Bool > *) |
| DataType | whatType (const Array< Char > *) |
| DataType | whatType (const Array< uChar > *) |
| DataType | whatType (const Array< Short > *) |
| DataType | whatType (const Array< uShort > *) |
| DataType | whatType (const Array< Int > *) |
| DataType | whatType (const Array< uInt > *) |
| DataType | whatType (const Array< float > *) |
| DataType | whatType (const Array< double > *) |
| DataType | whatType (const Array< Complex > *) |
| DataType | whatType (const Array< DComplex > *) |
| DataType | whatType (const Array< String > *) |
| DataType | whatType (const Record *) |
| DataType | whatType (const Quantum< Double > *) |
| DataType | whatType (const Array< Quantum< Double > > *) |
| DataType | asScalar (DataType type) |
| It is sometimes useful to discover what the corresponding scalar (or array) type is for a given array (or scalar) type. | |
| DataType | asArray (DataType type) |
| Bool | isScalar (DataType type) |
| It is occasionally useful to discover whether or not a DataType represents an array or scalar value. | |
| Bool | isArray (DataType type) |
| Bool | isScalarFun (DataType type) |
Definition at line 156 of file DataType.h.
| ostream& casa::DataType_global_functions_DataType::operator<< | ( | ostream & | os, | |
| DataType | type | |||
| ) |
Write a formated representation (e.g., Type=Bool) of the given data type.
| DataType casa::DataType_global_functions_DataType::whatType | ( | const void * | ) | [inline] |
These (overloaded) functions return DataType that corresponds to to the type that is being pointed at.
A pointer is used to avoid to avoid having to create the object if it is of Array or Table types. At least for CFront, it also avoids those types from being instantiated (they are forward declared). The void* function matches any type (if none other will), and returns TpOther.
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| DataType casa::DataType_global_functions_DataType::whatType | ( | const float * | ) | [inline] |
Definition at line 192 of file DataType.h.
| DataType casa::DataType_global_functions_DataType::whatType | ( | const double * | ) | [inline] |
Definition at line 193 of file DataType.h.
| DataType casa::DataType_global_functions_DataType::whatType | ( | const Complex * | ) | [inline] |
Definition at line 194 of file DataType.h.
| DataType casa::DataType_global_functions_DataType::whatType | ( | const DComplex * | ) | [inline] |
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| DataType casa::DataType_global_functions_DataType::whatType | ( | const Array< Quantum< Double > > * | ) | [inline] |
Definition at line 212 of file DataType.h.
It is sometimes useful to discover what the corresponding scalar (or array) type is for a given array (or scalar) type.
Calling these with TpOther, TpTable, and TpRecord results in an exception being thrown.
It is occasionally useful to discover whether or not a DataType represents an array or scalar value.
Note that TpTable, TpRecord, and TpOther are neither scalar nor array types.
It is sometimes useful to discover if a DataType represents a real numeric value (i.e., can it be cast to a Double?) This returns True for both real scalar and array type.
Returns True for Complex or DComplex scalar or array types.
Returns True if the type is either Real or Complex/DComplex.
1.5.1