The
Decompression Data Source Structure
The
CDSequenceDataSource
structure contains a linked list of all data sources for a decompression sequence. Because each data source contains a link to the next data source, a codec can access all data sources from this field. The
CDSequenceDataSource
structure is defined as follows:
struct CDSequenceDataSource {
long recordSize;
void * next;
ImageSequence seqID;
ImageSequenceDataSource sourceID;
OSType sourceType;
long sourceInputNumber;
void * dataPtr;
Handle dataDescription;
long changeSeed;
ICMConvertDataFormatUPP transferProc;
void * transferRefcon;
long dataSize;
};
typedef struct CDSequenceDataSource CDSequenceDataSource;
typedef CDSequenceDataSource *CDSequenceDataSourcePtr;
Field descriptions
-
recordSize
-
Specifies the size of the record.
-
next
-
Contains a pointer to the next source entry. If it is
nil
, there are no more entries.
-
seqID
-
Specifies the image sequence that this source is associated with.
-
sourceID
-
Specifies the source reference identifying this source.
-
sourceType
-
A four-character code describing how the input will be used. This value is passed to this parameter by the
CDSequenceNewDataSource
function when the source is created.
-
sourceInputNumber
-
This value is passed to this parameter by the
CDSequenceNewDataSource
function when the source is created.
-
dataPtr
-
Contains a pointer to the actual source data.
-
dataDescription
-
Contains a handle to a data structure describing the data format. This is often a Image Description Handle.
-
changeSeed
-
Contains an integer that is incremented each time the
dataPtr
field changes or that data that the
dataPtr
field points to changes. By remembering the value of this field and comparing to the value the next time the decompressor or compressor component is called, the component can determine if new data is present.
-
transferProc
-
Reserved
-
transferRefcon
-
Reserved
-
datasize
-
Specifies the size of the
data
pointer to the
dataPtr
field.
© 1997 Apple Computer, Inc.Previous | Chapter Top | Chapter Contents | Next
