added DropCache to GDALDataset

DropCache() release cache blocks but does not write cache to disk. It is similar tp FlushCache(true) but does not assume that the dataset will be closed.
chacha21 · Dec 8, 2023 · 27c6a37 · 27c6a37
1 parent ffd100b
commit 27c6a37
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Showing 6 changed files with 127 additions and 5 deletions.
diff --git a/gcore/gdal.h b/gcore/gdal.h
@@ -1545,6 +1545,7 @@ CPLErr CPL_DLL CPL_STDCALL GDALComputeRasterMinMax(GDALRasterBandH hBand,
                                                    int bApproxOK,
                                                    double adfMinMax[2]);
 CPLErr CPL_DLL CPL_STDCALL GDALFlushRasterCache(GDALRasterBandH hBand);
+CPLErr CPL_DLL CPL_STDCALL GDALDropRasterCache(GDALRasterBandH hBand);
 CPLErr CPL_DLL CPL_STDCALL GDALGetRasterHistogram(
     GDALRasterBandH hBand, double dfMin, double dfMax, int nBuckets,
     int *panHistogram, int bIncludeOutOfRange, int bApproxOK,

diff --git a/gcore/gdal_priv.h b/gcore/gdal_priv.h
@@ -537,6 +537,7 @@ class CPL_DLL GDALDataset : public GDALMajorObject
     Bands GetBands();
 
     virtual CPLErr FlushCache(bool bAtClosing = false);
+    virtual CPLErr DropCache();
 
     virtual GIntBig GetEstimatedRAMUsage();
 
@@ -1188,7 +1189,7 @@ class GDALAbstractBandBlockCache
 
     int m_nInitialDirtyBlocksInFlushCache = 0;
     int m_nLastTick = -1;
-    bool m_bWriteDirtyBlocks = true;
+    size_t m_bWriteDirtyBlocksDisabled = 0;
 
     void FreeDanglingBlocks();
     void UnreferenceBlockBase();
@@ -1205,9 +1206,13 @@ class GDALAbstractBandBlockCache
     void AddBlockToFreeList(GDALRasterBlock *);
     void IncDirtyBlocks(int nInc);
     void WaitCompletionPendingTasks();
+    void EnableDirtyBlockWriting()
+    {
+        --m_bWriteDirtyBlocksDisabled;
+    }
     void DisableDirtyBlockWriting()
     {
-        m_bWriteDirtyBlocks = false;
+        ++m_bWriteDirtyBlocksDisabled;
     }
     bool HasDirtyBlocks() const
     {
@@ -1412,6 +1417,7 @@ class CPL_DLL GDALRasterBand : public GDALMajorObject
     // New OpengIS CV_SampleDimension stuff.
 
     virtual CPLErr FlushCache(bool bAtClosing = false);
+    virtual CPLErr DropCache();
     virtual char **GetCategoryNames();
     virtual double GetNoDataValue(int *pbSuccess = nullptr);
     virtual int64_t GetNoDataValueAsInt64(int *pbSuccess = nullptr);

diff --git a/gcore/gdalarraybandblockcache.cpp b/gcore/gdalarraybandblockcache.cpp
@@ -442,7 +442,7 @@ CPLErr GDALArrayBandBlockCache::FlushBlock(int nXBlockOff, int nYBlockOff,
 
     CPLErr eErr = CE_None;
 
-    if (m_bWriteDirtyBlocks && bWriteDirtyBlock && poBlock->GetDirty())
+    if (!m_bWriteDirtyBlocksDisabled && bWriteDirtyBlock && poBlock->GetDirty())
     {
         UpdateDirtyBlockFlushingLog();
 

diff --git a/gcore/gdaldataset.cpp b/gcore/gdaldataset.cpp
@@ -613,6 +613,59 @@ CPLErr CPL_STDCALL GDALFlushCache(GDALDatasetH hDS)
     return GDALDataset::FromHandle(hDS)->FlushCache(false);
 }
 
+/************************************************************************/
+/*                             DropCache()                              */
+/************************************************************************/
+
+/**
+* \brief Drop all write cached data
+*
+* This method is the same as the C function GDALDropCache().
+*
+* @return CE_None in case of success
+*/
+
+CPLErr GDALDataset::DropCache()
+
+{
+    CPLErr eErr = CE_None;
+    // This sometimes happens if a dataset is destroyed before completely
+    // built.
+
+    if (papoBands)
+    {
+        for (int i = 0; i < nBands; ++i)
+        {
+            if (papoBands[i])
+            {
+                if (papoBands[i]->DropCache() != CE_None)
+                    eErr = CE_Failure;
+            }
+        }
+    }
+
+    return eErr;
+}
+
+/************************************************************************/
+/*                           GDALDropCache()                           */
+/************************************************************************/
+
+/**
+* \brief Drop all write cached data
+*
+* @see GDALDataset::DropCache().
+* @return CE_None in case of success
+*/
+
+CPLErr CPL_STDCALL GDALDropCache(GDALDatasetH hDS)
+
+{
+    VALIDATE_POINTER1(hDS, "GDALDropCache", CE_Failure);
+
+    return GDALDataset::FromHandle(hDS)->DropCache();
+}
+
 /************************************************************************/
 /*                      GetEstimatedRAMUsage()                          */
 /************************************************************************/

diff --git a/gcore/gdalhashsetbandblockcache.cpp b/gcore/gdalhashsetbandblockcache.cpp
@@ -170,7 +170,7 @@ CPLErr GDALHashSetBandBlockCache::FlushCache()
         {
             CPLErr eErr = CE_None;
 
-            if (m_bWriteDirtyBlocks && eGlobalErr == CE_None &&
+            if (!m_bWriteDirtyBlocksDisabled && eGlobalErr == CE_None &&
                 poBlock->GetDirty())
             {
                 UpdateDirtyBlockFlushingLog();
@@ -227,7 +227,7 @@ CPLErr GDALHashSetBandBlockCache::FlushBlock(int nXBlockOff, int nYBlockOff,
 
     CPLErr eErr = CE_None;
 
-    if (m_bWriteDirtyBlocks && bWriteDirtyBlock && poBlock->GetDirty())
+    if (!m_bWriteDirtyBlocksDisabled && bWriteDirtyBlock && poBlock->GetDirty())
         eErr = poBlock->Write();
 
     delete poBlock;

diff --git a/gcore/gdalrasterband.cpp b/gcore/gdalrasterband.cpp
@@ -1140,6 +1140,68 @@ CPLErr CPL_STDCALL GDALFlushRasterCache(GDALRasterBandH hBand)
     return GDALRasterBand::FromHandle(hBand)->FlushCache(false);
 }
 
+/************************************************************************/
+/*                             DropCache()                              */
+/************************************************************************/
+
+/**
+* \brief Drop raster data cache : data in cache will be lost.
+*
+* This call will recover memory used to cache data blocks for this raster
+* band, and ensure that new requests are referred to the underlying driver.
+*
+* This method is the same as the C function GDALDropRasterCache().
+*
+* @return CE_None on success.
+*/
+
+CPLErr GDALRasterBand::DropCache()
+
+{
+    CPLErr result = CE_None;
+
+    if (poBandBlockCache)
+        poBandBlockCache->DisableDirtyBlockWriting();
+
+    CPLErr eGlobalErr = eFlushBlockErr;
+
+    if (eFlushBlockErr != CE_None)
+    {
+        ReportError(
+            eFlushBlockErr, CPLE_AppDefined,
+            "An error occurred while writing a dirty block from DropCache");
+        eFlushBlockErr = CE_None;
+    }
+
+    if (poBandBlockCache == nullptr || !poBandBlockCache->IsInitOK())
+        result = eGlobalErr;
+    else
+        result = poBandBlockCache->FlushCache();
+
+    if (poBandBlockCache)
+        poBandBlockCache->EnableDirtyBlockWriting();
+
+    return result;
+}
+
+/************************************************************************/
+/*                        GDALDropRasterCache()                         */
+/************************************************************************/
+
+/**
+* \brief Drop raster data cache.
+*
+* @see GDALRasterBand::DropCache()
+*/
+
+CPLErr CPL_STDCALL GDALDropRasterCache(GDALRasterBandH hBand)
+
+{
+    VALIDATE_POINTER1(hBand, "GDALDropRasterCache", CE_Failure);
+
+    return GDALRasterBand::FromHandle(hBand)->DropCache();
+}
+
 /************************************************************************/
 /*                        UnreferenceBlock()                            */
 /*                                                                      */