avoid creating compression object just to compute numLinesInBuffer

Signed-off-by: Peter Hillman <[email protected]>

OpenEXR/IlmImf/ImfMisc.cpp

@@ -269,6 +269,7 @@ defaultFormat (Compressor * compressor)
 }
 
 
+//obsolete
 int
 numLinesInBuffer (Compressor * compressor)
 {
@@ -1842,6 +1843,39 @@ usesLongNames (const Header &header)
     return false;
 }
 
+namespace
+{
+// for a given compression type, return the number of scanlines
+// compressed into a single chunk
+// TODO add to API and move to ImfCompressor.cpp
+int
+numLinesInBuffer(Compression comp)
+{
+    switch(comp)
+    {
+        case NO_COMPRESSION :
+        case RLE_COMPRESSION:
+        case ZIPS_COMPRESSION:
+            return 1;
+        case ZIP_COMPRESSION:
+            return 16;
+        case PIZ_COMPRESSION:
+            return 32;
+        case PXR24_COMPRESSION:
+            return 16;
+        case B44_COMPRESSION:
+        case B44A_COMPRESSION:
+        case DWAA_COMPRESSION:
+            return 32;
+        case DWAB_COMPRESSION:
+            return 256;
+
+        default:
+	        throw IEX_NAMESPACE::ArgExc ("Unknown compression type");
+    }
+}
+}
+
 int
 getScanlineChunkOffsetTableSize(const Header& header)
 {
@@ -1851,17 +1885,11 @@ getScanlineChunkOffsetTableSize(const Header& header)
     size_t maxBytesPerLine = bytesPerLineTable (header,
                                                 bytesPerLine);
 
-    Compressor* compressor = newCompressor(header.compression(),
-                                           maxBytesPerLine,
-                                           header);
-
-    int linesInBuffer = numLinesInBuffer (compressor);
+    int linesInBuffer = numLinesInBuffer ( header.compression() );
 
     int lineOffsetSize = (dataWindow.max.y - dataWindow.min.y +
                           linesInBuffer) / linesInBuffer;
 
-    delete compressor;
-
     return lineOffsetSize;
 }