Changes between Version 77 and Version 78 of rfc24_progressive_data_support


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Timestamp:
Mar 11, 2010, 5:00:18 PM (14 years ago)
Author:
warmerdam
Comment:

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  • rfc24_progressive_data_support

    v77 v78  
    5858    int GetBandSpace() {return nBandSpace;}
    5959
    60     int GetNDataRead(){return nDataRead;}
    61 
    6260    virtual GDALAsyncStatusType GetNextUpdatedRegion(int nTimeout,
    6361                                                     int* pnBufXOff,
    … …  
    6765
    6866    virtual void LockBuffer() = 0;
    69     virtual void LockBuffer(int nBufXOff, int nBufYOff,
    70                             int nBufXSize, int nBufYSize) = 0;
    7167    virtual void UnlockBuffer() = 0;
    7268
    … …  
    7470};
    7571}}}
    76 
    77 The async status list is as follows, and will be declared in gdal.h.
    78 
    79 {{{
    80 typedef enum
    81 {       
    82         GARIO_PENDING = 0,
    83         GARIO_UPDATE = 1,
    84         GARIO_ERROR = 2,
    85         GARIO_COMPLETE = 3,
    86         GARIO_TypeCount = 4
    87 } GDALAsyncStatusType;
    88 }}}
    89 
    90 === GDALDataset ===
    91 
    92 The GDALDataset class is extended with methods to create an asynchronous reader, and to cleanup the asynchronous reader.  It is intended that these methods would be subclassed by drivers implementing asynchronous data access.
    93 
    94 {{{
    95 Status: Development
    96 
    97 == Summary ==
    98 
    99 Provide an interface for asynchronous/streaming data access in GDAL.  The initial implementation is for JPIP, but should be generic enough to apply to other streaming / progressive approaches.  Background on the JPIP (Kakadu) implementation can be found in [wiki:rfc24_jpipkak].
    100 
    101 == Interfaces ==
    102 
    103 === GDALAsyncRasterIO ===
    104 
    105 This new class is intended to represent an active asynchronous raster imagery request.  The request includes information on a source window on the dataset, a target buffer size (implies level of decimation or replication), the buffer type, buffer interleaving, data buffer and bands being requested.  Essentially the same sort of information that is passed in a GDALDataset::!RasterIO() request. 
    106 
    107 While an implementation of the simple accessors is provided as part of the class, it is intended that the class be subclassed as part of implementation of a particular driver, and custom implementations of !GetNextUpdatedRegion(), !LockBuffer() and !UnlockBuffer() provided.
    108 
    109 {{{
    110 class CPL_DLL GDALAsyncRasterIO
    111 {
    112   protected:
    113     GDALDataset* poDS;
    114     int          nXOff;
    115     int          nYOff;
    116     int          nXSize;
    117     int          nYSize;
    118     void *       pBuf;
    119     int          nBufXSize;
    120     int          nBufYSize;
    121     GDALDataType eBufType;
    122     int          nBandCount;
    123     int*         panBandMap;
    124     int          nPixelSpace;
    125     int          nLineSpace;
    126     int          nBandSpace;
    127 
    128   public:
    129     GDALAsyncRasterIO();
    130     virtual ~GDALAsyncRasterIO();
    131 
    132     GDALDataset* GetGDALDataset() {return poDS;}
    133     int GetXOffset() {return nXOff;}
    134     int GetYOffset() {return nYOff;}
    135     int GetXSize() {return nXSize;}
    136     int GetYSize() {return nYSize;}
    137     void * GetBuffer() {return pBuf;}
    138     int GetBufferXSize() {return nBufXSize;}
    139     int GetBufferYSize() {return nBufYSize;}
    140     GDALDataType GetBufferType() {return eBufType;}
    141     int GetBandCount() {return nBandCount;}
    142     int* GetBandMap() {return panBandMap;}
    143     int GetPixelSpace() {return nPixelSpace;}
    144     int GetLineSpace() {return nLineSpace;}
    145     int GetBandSpace() {return nBandSpace;}
    146 
    147     virtual GDALAsyncStatusType
    148         GetNextUpdatedRegion(int nTimeout,
    149                              int* pnBufXOff, int* pnBufYOff,
    150                              int* pnBufXSize, int* pnBufXSize) = 0;
    151     virtual void LockBuffer() {}
    152     virtual void LockBuffer(int nBufXOff, int nBufYOff,
    153                             int nBufXSize, int nBufYSize) {}
    154     virtual void UnlockBuffer() {}
    155 };
    156 
    157 }}}
    158 
    159 The !GetNextUpdatedRegion() method can be used to wait for an update to the imagery buffer, and to find out what area was updated.   The !LockBuffer() and !UnlockBuffer() methods can be used to temporarily disable updates to the buffer while application code accesses the buffer.  The GetNextUpdatedRegion() method is described in more detail below.
    16072
    16173==== !GetNextUpdatedRegion() ====
    … …  
    16880
    16981int nTimeout;
    170       The amount of time to wait for results measured in milliseconds.  If this is
    171       zero available work may be processed but no waiting for the arrival of more
    172       imagery should be done.  Processing available imagery may still take an arbitrary
    173       amount of time.
     82  The amount of time to wait for results measured in milliseconds.  If this is
     83  zero available work may be processed but no waiting for the arrival of more
     84  imagery should be done.  Processing available imagery may still take an
     85  arbitrary amount of time.
    17486
    17587int *pnBufXOff, *pnBufYOff, *pnBufXSize, *pnBufYSize;
    176       The window of data updated within the async io imagery buffer is returned in
    177       these variables. This information can be used to limit screen redraws or other
    178       processing to the portion of the imagery that may have changed.
     88  The window of data updated within the async io imagery buffer is returned in
     89  these variables. This information can be used to limit screen redraws or other
     90  processing to the portion of the imagery that may have changed.
    17991}}}
    18092