(SQL Server) Transition from Compression.BeginCompressBytes to FirstChunk/LastChunk

Provides instructions for replacing deprecated BeginCompressBytes method calls with using FirstChunk and LastChunk properties.

Note: This example requires Chilkat v11.0.0 or greater.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

    DECLARE @facSrc int
    EXEC @hr = sp_OACreate 'Chilkat.FileAccess', @facSrc OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    DECLARE @facDest int
    EXEC @hr = sp_OACreate 'Chilkat.FileAccess', @facDest OUT

    -- Open a large binary file for reading.
    EXEC sp_OAMethod @facSrc, 'OpenForRead', @success OUT, 'qa_data/bmp/big.bmp'
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @facSrc, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @facSrc
        EXEC @hr = sp_OADestroy @facDest
        RETURN
      END

    -- If we compress in 64K chunks, find out how many blocks there will be.
    DECLARE @blockSize int
    SELECT @blockSize = 65536
    DECLARE @numBlocks int
    EXEC sp_OAMethod @facSrc, 'GetNumBlocks', @numBlocks OUT, @blockSize

    -- Open an output file for the compressed data.
    EXEC sp_OAMethod @facDest, 'OpenForWrite', @success OUT, 'c:/temp/qa_output/compressedBmp.dat'
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @facDest, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @facSrc
        EXEC @hr = sp_OADestroy @facDest
        RETURN
      END

    DECLARE @compress int
    EXEC @hr = sp_OACreate 'Chilkat.Compression', @compress OUT

    EXEC sp_OASetProperty @compress, 'Algorithm', 'deflate'

    -- ----------------------------------------------------------------------------------
    -- This is the deprecated way of compressing in chunks using Begin/More/End methods..
    -- ----------------------------------------------------------------------------------
    DECLARE @i int
    SELECT @i = 0
    WHILE @i < @numBlocks
      BEGIN
        EXEC sp_OAMethod @facSrc, 'ReadBlock', @fileBytes OUT, @i, @blockSize
        IF @i = 0
          BEGIN
            EXEC sp_OAMethod @compress, 'BeginCompressBytes', @compressedBytes OUT, @fileBytes
          END
        ELSE
          BEGIN
            EXEC sp_OAMethod @compress, 'MoreCompressBytes', @compressedBytes OUT, @fileBytes
          END

        EXEC sp_OAMethod @facDest, 'FileWrite', @success OUT, @compressedBytes

        SELECT @i = @i + 1
      END

    -- At the very end, flush any remaining compressed bytes, if any.
    EXEC sp_OAMethod @compress, 'EndCompressBytes', @compressedBytes OUT
    EXEC sp_OAMethod @facDest, 'FileWrite', @success OUT, @compressedBytes

    EXEC sp_OAMethod @facSrc, 'FileClose', NULL
    EXEC sp_OAMethod @facDest, 'FileClose', NULL


    PRINT 'Finished compressing file.'

    -- ----------------------------------------------------------------------------------
    -- This is new way of compressing in chunks using FirstChunk and LastChunk properties
    -- ----------------------------------------------------------------------------------

    EXEC sp_OAMethod @facSrc, 'OpenForRead', @success OUT, 'qa_data/bmp/big.bmp'
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @facSrc, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @facSrc
        EXEC @hr = sp_OADestroy @facDest
        EXEC @hr = sp_OADestroy @compress
        RETURN
      END

    EXEC sp_OAMethod @facDest, 'OpenForWrite', @success OUT, 'c:/temp/qa_output/compressedBmp2.dat'
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @facDest, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @facSrc
        EXEC @hr = sp_OADestroy @facDest
        EXEC @hr = sp_OADestroy @compress
        RETURN
      END

    -- Assuming numBlocks > 1
    EXEC sp_OASetProperty @compress, 'FirstChunk', 1
    EXEC sp_OASetProperty @compress, 'LastChunk', 0

    SELECT @i = 0
    WHILE @i < @numBlocks
      BEGIN
        EXEC sp_OAMethod @facSrc, 'ReadBlock', @fileBytes OUT, @i, @blockSize
        EXEC sp_OAMethod @compress, 'CompressBytes', @compressedBytes OUT, @fileBytes

        EXEC sp_OAMethod @facDest, 'FileWrite', @success OUT, @compressedBytes

        SELECT @i = @i + 1

        EXEC sp_OASetProperty @compress, 'FirstChunk', 0
        IF @i = (@numBlocks - 1)
          BEGIN
            EXEC sp_OASetProperty @compress, 'LastChunk', 1
          END
      END

    EXEC sp_OAMethod @facSrc, 'FileClose', NULL
    EXEC sp_OAMethod @facDest, 'FileClose', NULL


    PRINT 'Finished compressing file 2.'

    EXEC @hr = sp_OADestroy @facSrc
    EXEC @hr = sp_OADestroy @facDest
    EXEC @hr = sp_OADestroy @compress


END
GO