SQL Server

File Read Blocks

Demonstrates how to read a file in fixed-size blocks (except for the very last block). SQL Server

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @iTmp0 int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

    -- Demonstrates how to read a file in blocks,
    -- which can be useful when uploading to cloud storage
    -- services such as Azure, S3, Google, etc.

    -- For this example, we're simply writing the blocks
    -- to an output file, and then checking to see if the
    -- resulting file contents equals the original file contents.

    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

    DECLARE @srcPath nvarchar(4000)
    SELECT @srcPath = 'qa_data/xml/hamlet.xml'
    DECLARE @destPath nvarchar(4000)
    SELECT @destPath = 'qa_output/hamletOut.xml'

    EXEC sp_OAMethod @facSrc, 'OpenForRead', @success OUT, @srcPath
    EXEC sp_OAMethod @facDest, 'OpenForWrite', @success OUT, @destPath
    -- Assuming success for the example..

    -- How many 1024-byte blocks?  (Including 1 for the last partial block)
    DECLARE @numBlocks int
    EXEC sp_OAMethod @facSrc, 'GetNumBlocks', @numBlocks OUT, 1024

    DECLARE @i int
    SELECT @i = 0
    WHILE (@i < @numBlocks)
      BEGIN
        EXEC sp_OAMethod @facSrc, 'ReadBlock', @dataBlock OUT, @i, 1024
        EXEC sp_OAGetProperty @facSrc, 'LastMethodSuccess', @iTmp0 OUT
        IF @iTmp0 <> 1
          BEGIN
            EXEC sp_OAGetProperty @facSrc, 'LastErrorText', @sTmp0 OUT
            PRINT @sTmp0
            EXEC @hr = sp_OADestroy @facSrc
            EXEC @hr = sp_OADestroy @facDest
            RETURN
          END
        EXEC sp_OAMethod @facDest, 'FileWrite', @success OUT, @dataBlock
        IF @success <> 1
          BEGIN
            EXEC sp_OAGetProperty @facDest, 'LastErrorText', @sTmp0 OUT
            PRINT @sTmp0
            EXEC @hr = sp_OADestroy @facSrc
            EXEC @hr = sp_OADestroy @facDest
            RETURN
          END
        SELECT @i = @i + 1
      END

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

    DECLARE @bEqual int
    EXEC sp_OAMethod @facSrc, 'FileContentsEqual', @bEqual OUT, @srcPath, @destPath
    IF @bEqual <> 1
      BEGIN

        PRINT 'Something went wrong!'
        EXEC @hr = sp_OADestroy @facSrc
        EXEC @hr = sp_OADestroy @facDest
        RETURN
      END


    PRINT 'File successfully copied by blocks.'

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


END
GO