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BDE 4.39.x Production Release
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#include <bdld_datum.h>
This class implements a mechanism that provides a space-efficient discriminated union that holds the value of ether scalar type or an aggregate of Datum objects. The size of Datum is 8 bytes (same as a double) on 32-bit platforms and 16 bytes on 64-bit platforms. Separate representation are needed on 32 and 64 bit platforms because of the differing size of a pointer (a 64-bit pointer cannot reasonably be held in a 32-bit footprint).
Representation on a 32-bit Platforms: Values are stored inside an 8-byte unsigned char array (d_data). Any double value (including NaN and infinity values) can be stored inside Datum. When storing a value of a type other than double, the bits in d_data that correspond to the exponent part of a double value are set to 1, with the 4 bits in the fraction part used to indicate the type of value stored.
Representation on 64-bit platforms: Values are stored inside a 16 byte unsigned char array (d_data) to store values. The type information is stored in the upper 2 bytes of the character array. Remaining 14 bytes are used to store the actual value or the pointer to the external memory that holds the value.
For details on the internal representations that are used for various types on 32 and 64 bit platforms, please see the implementation notes in bdld_datum.cpp.
Datum objects are bitwise copyable and have trivial initialization, assignment and destruction. Only one of the copies of the same Datum object can be passed to destroy. The rest of those copies then become invalid and it is undefined behavior to deep-copy or destroy them. Although, these copies can be used on the left hand side of assignment.
See bdld_datum
Public Types | |
| enum | DataType { e_NIL = 0 , e_INTEGER = 1 , e_DOUBLE = 2 , e_STRING = 3 , e_BOOLEAN = 4 , e_ERROR = 5 , e_DATE = 6 , e_TIME = 7 , e_DATETIME = 8 , e_DATETIME_INTERVAL = 9 , e_INTEGER64 = 10 , e_USERDEFINED = 11 , e_ARRAY = 12 , e_MAP = 13 , e_BINARY = 14 , e_DECIMAL64 = 15 , e_INT_MAP = 16 , e_REAL = e_DOUBLE , e_ERROR_VALUE = e_ERROR } |
| enum | { k_NUM_TYPES = 17 } |
| typedef bsl::allocator | AllocatorType |
| typedef bsls::Types::size_type | SizeType |
Friends | |
| bool | operator== (const Datum &lhs, const Datum &rhs) |
| bool | operator!= (const Datum &lhs, const Datum &rhs) |
| bsl::ostream & | operator<< (bsl::ostream &stream, const Datum &rhs) |
SizeType is an alias for an unsigned integral value, representing the capacity of a datum array, the capacity of a datum map, the capacity of the keys-capacity of a datum-key-owning map or the length of a string.
Enumeration used to discriminate among the different externally- exposed types of values that can be stored inside bdld::Datum.
| Enumerator | |
|---|---|
| e_NIL | |
| e_INTEGER | |
| e_DOUBLE | |
| e_STRING | |
| e_BOOLEAN | |
| e_ERROR | |
| e_DATE | |
| e_TIME | |
| e_DATETIME | |
| e_DATETIME_INTERVAL | |
| e_INTEGER64 | |
| e_USERDEFINED | |
| e_ARRAY | |
| e_MAP | |
| e_BINARY | |
| e_DECIMAL64 | |
| e_INT_MAP | |
| e_REAL | |
| e_ERROR_VALUE | |
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default |
Create a datum having an uninitialized value. The behavior for every accessor method is undefined until this object is assigned a value.
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default |
Create a datum having the value of the specified original.
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default |
Destroy this object.
destroy).
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inlinestatic |
Return, by value, a datum that refers to the specified array.
array was created using createUninitializedArray method. The behavior is also undefined unless each element in the held datum array has been assigned a value and the array's length has been set accordingly. Datum::destroy is called on the returned object.
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inlinestatic |
Return, by value, a datum that refers to the specified intMap.
map was created using createUninitializedIntMap method. The behavior is also undefined unless each element in the held map has been assigned a value and the size of the map has been set accordingly. Datum::destroy is called on the returned object.
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inlinestatic |
Return, by value, a datum that refers to the specified map.
map was created using createUninitializedMapOwningKeys method. The behavior is also undefined unless each element in the held map has been assigned a value and the size of the map has been set accordingly. The behavior is also undefined unless keys have been copied into the map. Datum::destroy is called on the returned object.
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inlinestatic |
Return, by value, a datum that refers to the specified map.
map was created using createUninitializedMap method. The behavior is also undefined unless each element in the held map has been assigned a value and the size of the map has been set accordingly. Datum::destroy is called on the returned object.
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inlinestatic |
| void bdld::Datum::apply | ( | t_VISITOR & | visitor | ) | const |
Apply the specified visitor to the current value represented by this object by passing held value to the visitor object's operator() overload.
| bdld::Datum::BSLMF_NESTED_TRAIT_DECLARATION | ( | Datum | , |
| bdlb::HasPrintMethod | |||
| ) |
| bdld::Datum::BSLMF_NESTED_TRAIT_DECLARATION | ( | Datum | , |
| bsl::is_trivially_copyable | |||
| ) |
| bdld::Datum::BSLMF_NESTED_TRAIT_DECLARATION | ( | Datum | , |
| bsl::is_trivially_default_constructible | |||
| ) |
| bdld::Datum::BSLMF_NESTED_TRAIT_DECLARATION | ( | Datum | , |
| bslmf::IsBitwiseMoveable | |||
| ) |
| Datum bdld::Datum::clone | ( | const AllocatorType & | allocator | ) | const |
Return a datum holding a "deep-copy" of this object, using the specified allocator to supply memory. This method creates an independent deep-copy of the data of this object, including any referenced data, with the exception of {User Defined Types}. For further information see {Deep Copying}.
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static |
Return, by value, a datum referring to the copy of the specified value of the specified size, using the specified allocator to supply memory (if needed).
size <= UINT_MAX. Datum::destroy is called on the returned object.
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inlinestatic |
Return, by value, a datum having the copy of the specified StringRef value, using the specified allocator to supply memory (if needed).
value.length() <= UINT_MAX. Datum::destroy is called on the returned object.
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static |
Return, by value, a datum that refers to the copy of the specified string having the specified length, using the specified allocator to supply memory (if needed).
0 != string || 0 == length. The behavior is also undefined unless length <= UINT_MAX. Datum::destroy is called on the returned object.
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inlinestatic |
Return, by value, a datum referring to the specified array, having the specified length, using the specified allocator to supply memory (if needed). array is not copied, and is not freed when the returned object is destroyed with Datum::destroy.
array contains at least length elements. The behavior is also undefined unless length <= UINT_MAX.
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inlinestatic |
Return, by value, a datum having the specified value, using the specified allocator to supply memory (if needed). The array referenced by value is not copied, and is not freed if Datum::destroy is called on the returned object.
value.length() <= UINT_MAX.
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inlinestatic |
Return, by value, a datum having the specified bool value.
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inlinestatic |
Return, by value, a datum having the specified Date value.
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inlinestatic |
Return, by value, a datum having the specified Datetime value, using the specified allocator to supply memory (if needed).
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inlinestatic |
Return, by value, a datum holding the specified DatetimeInterval value, using the specified allocator to supply memory (if needed).
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static |
Return, by value, a datum having the specified Decimal64 value, using the specified allocator to supply memory (if needed).
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inlinestatic |
Return, by value, a datum having the specified double value. When value is NaN this method guarantees only that a NaN value is stored. The sign and NaN payload bits of a NaN value later retrieved by the theDouble method are unspecified (see also {Special Floating Point Values}.
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inlinestatic |
Return, by value, a datum having a DatumError value with the specified code.
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static |
Return, by value, a datum having a DatumError value with the specified code and the specified message, using the specified allocator to supply memory (if needed).
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inlinestatic |
Return, by value, a datum having the specified int value.
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inlinestatic |
Return, by value, a datum having the specified Integer64 value, using the specified allocator to supply memory (if needed).
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inlinestatic |
Return, by value, a datum having no value.
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inlinestatic |
Return, by value, a datum having the specified StringRef value, using the specified allocator to supply memory (if needed).
value.length() <= UINT_MAX. string is not copied, and is not freed if Datum::destroy is called on the returned object.
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inlinestatic |
Return, by value, a datum that refers to the specified string, using the specified allocator to supply memory (if needed).
string points to a UTF-8 encoded c-string. The behavior is also undefined unless 'strlen(string) <= UINT_MAX'. string is not copied, and is not freed if Datum::destroy is called on the returned object.
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inlinestatic |
Return, by value, a datum that refers to the specified string having the specified length, using the specified allocator to supply memory (if needed).
0 != string || 0 == length. The behavior is also undefined unless length <= UINT_MAX. string is not copied, and is not freed if Datum::destroy is called on the returned object.
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inlinestatic |
Return, by value, a datum having the specified Time value.
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inlinestatic |
Return, by value, a datum having the DatumUdt value with the specified data and the specified type values.
0 <= type <= 65535. data is held, not owned. Also note that the content pointed to by data object is not copied.
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static |
Load the specified result with a reference to a newly created datum array having the specified capacity, using the specified allocator to supply memory.
capacity Datum objects would exceed the addressable memory for the platform. capacity. Also note that any elements in the datum array that need dynamic memory must be allocated with allocator.
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Load the specified result with a reference to a newly created binary buffer of the specified size, using the specified allocator to supply memory, and return the address of this buffer.
size <= UINT_MAX.
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static |
Load the specified result with a reference to a newly created datum int-map having the specified capacity, using the specified allocator to supply memory.
capacity DatumIntMapEntry objects would exceed the addressable memory for the platform. capacity. Also note that any elements in the datum int-map that need dynamic memory, should also be allocated with allocator.
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Load the specified result with a reference to a newly created datum-key-owning map having the specified capacity and keysCapacity, using the specified allocator to supply memory.
capacity DatumMapEntry object plus keysCapacity would exceed the addressable memory for the platform.capacity and total size of all the keys cannot exceed keysCapacity. Also note that any elements in the datum-key-owning map that need dynamic memory, should also be allocated with allocator.
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Load the specified result with a reference to a newly created datum map having the specified capacity, using the specified allocator to supply memory.
capacity DatumMapEntry objects would exceed the addressable memory for the platform. capacity. Also note that any elements in the datum map that need dynamic memory, should also be allocated with allocator.
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inlinestatic |
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static |
Load the specified result with a reference to a newly created character buffer of the specified length, using the specified allocator to supply memory, and return the address of this buffer.
length <= UINT_MAX.
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static |
Return the non-modifiable string representation corresponding to the specified type, if it exists, and a unique (error) string otherwise. The string representation of type matches its corresponding enumerator name with the e_ prefix elided.
For example:
will print the following on standard output:
type that does not match any of the enumerators will result in a string representation that is distinct from any of those corresponding to the enumerators, but is otherwise unspecified.
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static |
Deallocate any memory that was previously allocated within the specified value using the specified allocator. If the value contains an adopted array of datums, destroy is called on each array element. If the value contains an adopted map of datums, destroy is called on each map element.
value was allocated using allocator, and has not previously been released by a call to destroy, either on this object, or on another object referring to same contents as this object (i.e., only one copy of a Datum object can be destroyed). The behavior is also undefined if value has an uninitialized or partially initialized array or map (created using createUninitializedArray, createUninitializedMap or createUninitializeMapOwningKeys). value is left in an uninitialized state, and must be assigned a new value before being accessed again.
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inlinestatic |
Deallocate the memory used by the specified array (but not memory allocated for its contained elements) using the specified allocator. This method does not destroy individual array elements and the memory allocated for those elements must be explicitly deallocated before calling this method.
array was created with createUninitializedArray using allocator.
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inlinestatic |
Deallocate the memory used by the specified intMap (but not memory allocated for its contained elements) using the specified allocator. This method does not destroy individual map elements and the memory allocated for those elements must be explicitly deallocated before calling this method.
map was created with createUninitializedIntMap using allocator.
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inlinestatic |
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inlinestatic |
Deallocate the memory used by the specified map (but not memory allocated for its contained elements) using the specified allocator. This method does not destroy individual map elements and the memory allocated for those elements must be explicitly deallocated before calling this method.
map was created with createUninitializedMap using allocator.
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inlinestatic |
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inline |
Return true if this object represents an array of Datums and false otherwise.
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inline |
Return true if this object represents a binary value and false otherwise.
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Return true if this object represents a boolean value and false otherwise.
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Return true if this object represents a bdlt::Date value and false otherwise.
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Return true if this object represents a bdlt::Datetime value and false otherwise.
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Return true if this object represents a bdlt::DatetimeInterval value and false otherwise.
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Return true if this object represents a bdlfpd::Decimal64 value and false otherwise.
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Return true if this object represents a double value and false otherwise.
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Return true if this object represents a DatumError value and false otherwise.
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inline |
Return true if this object represents a reference to an externally managed array, string or user-defined object and false otherwise. If this method returns false, calling destroy on this object will release the memory used by the array, string, or used-defined object as well as any meta-data directly used by this datum (e.g., length information); otherwise (if this method returns true) calling destroy on this object will release any allocated meta-data, but will not impact the externally managed array, string, or user-defined object.
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Return true if this object represents an integer value and false otherwise.
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Return true if this object represents a Int64 value and false otherwise.
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Return true if this object represents a map of datums that are keyed by 32-bit int values and false otherwise.
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Return true if this object represents a map of datums that are keyed by string values and false otherwise.
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Return true if this object represents no value and false otherwise.
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Return true if this object represents a string value and false otherwise.
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Return true if this object represents a bdlt::Time value and false otherwise.
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Return true if this object represents a DatumUdt value and false otherwise.
| bsl::ostream & bdld::Datum::print | ( | bsl::ostream & | stream, |
| int | level = 0, |
||
| int | spacesPerLevel = 4 |
||
| ) | const |
Write the value of this object to the specified output stream in a human-readable format, and return a reference to the modifiable stream. Optionally specify an initial indentation level, whose absolute value is incremented recursively for nested objects. If level is specified, optionally specify spacesPerLevel, whose absolute value indicates the number of spaces per indentation level for this and all of its nested objects. If level is negative, suppress indentation of the first line. If spacesPerLevel is negative, format the entire output on one line, suppressing all but the initial indentation (as governed by level). If stream is not valid on entry, this operation has no effect.
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Return the array value represented by this object as a DatumArrayRef object.
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Return the binary reference represented by this object as a DatumBinaryRef object.
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Return the boolean value represented by this object.
bool value.
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Return the date value represented by this object as a bdlt::Date object.
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Return the date+time value represented by this object as a bdlt::Datetime object.
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Return the date+time interval value represented by this object as a bdlt::DatetimeInterval.
| bdldfp::Decimal64 bdld::Datum::theDecimal64 | ( | ) | const |
Return the decimal floating point value represented by this object as a bdlfpd::Decimal64 value.
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Return the double value represented by this object.
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Return the error value represented by this object as a DatumError value.
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Return the integer value represented by this object.
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Return the 64-bit integer value represented by this object as a Int64 value.
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Return the int-map value represented by this object as a DatumIntMapRef object.
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Return the map value represented by this object as a DatumMapRef object.
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Return the string value represented by this object as a bslstl::StringRef object.
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Return the time value represented by this object as a bdlt::Time object.
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Return the user-defined object represented by this object as a DatumUdt object.
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Return the type of value represented by this object as one of the enumeration values defined in DataType.
Return true if the specified lhs and rhs datums do not represent the same value, and false otherwise. Two datums do not represent the same value if they do not hold values of the same type, or they hold values of the same type but invoking == operator on the stored values returns false. Two strings do not have the same value if they have different lengths or values at one of the respective character position are not the same. Two DatumUdt objects are not equal if they have different pointer or type values. Two bslmf::Nil values are always equal. Two datums with NaN values are never equal. Two datums that hold arrays of datums have different values if the underlying arrays have different lengths or invoking == operator on at least one of the corresponding pair of contained elements returns false. Two datums that hold maps of datums have different values if the underlying maps have different sizes or at least one of the corresponding pair of elements in the maps have different keys or invoking == operator on the values returns false.
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Write the specified rhs value to the specified output stream in the format shown in the second column in the table below (based on the type of value stored, indicated by the first column):
and return a reference to the modifiable stream. The function will have no effect if the specified stream is not valid.
Return true if the specified lhs and rhs represent the same value, and false otherwise. Two datums (not holding strings and user- defined objects) represent the same value if they have the same type of value stored inside them and invoking == operator on the stored values returns true. Two datums holding strings are equal if the strings have the same length and and values at each respective character position are also same. Two datums holding user-defined objects are equal if the user-defined objects have the same pointer and type values. Two nil datums are always equal. Two Datum objects holding NaN values are never equal. Two datums that hold arrays of datums have the same value if the underlying arrays have the same length and invoking == operator on each corresponding element returns true. Two datums that hold maps of datums have the same value if the underlying maps have the same size and each corresponding pair of elements in the maps have the same keys and invoking == operator on the values returns true.
| TypedAccess bdld::Datum::d_as |
| bsls::AlignedBuffer<16> bdld::Datum::d_data |