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(C#) Decompress Large Text File in BlocksDecompresses a large text file in blocks, and compares the restored (decompressed) file with the original to make sure it's correct.
// This example requires the Chilkat API to have been previously unlocked. // See Global Unlock Sample for sample code. // First, let's compress a text file. // We'll then decompress in blocks, and compare the decompressed with the original file. // Compress a text file: Chilkat.Compression compress = new Chilkat.Compression(); compress.Algorithm = "deflate"; bool success = compress.CompressFile("qa_data/hamlet.xml","qa_data/hamlet_compressed.dat"); if (success != true) { Debug.WriteLine(compress.LastErrorText); return; } Chilkat.FileAccess fac = new Chilkat.FileAccess(); // Examine the uncompressed and compressed sizes: string originalPath = "qa_data/hamlet.xml"; // Note: The FileSize method returns a signed 32-bit integer. If the file is potentially larger than 2GB, call FileSizeStr instead to return // the size of the file as a string, then convert to an integer value. Debug.WriteLine("uncompressed size: " + Convert.ToString(fac.FileSize(originalPath))); Debug.WriteLine("compressed size: " + Convert.ToString(fac.FileSize("qa_data/hamlet_compressed.dat"))); // Decompress in blocks.. Chilkat.FileAccess facSrc = new Chilkat.FileAccess(); Chilkat.FileAccess facDest = new Chilkat.FileAccess(); facSrc.OpenForRead("qa_data/hamlet_compressed.dat"); // If we compress in 32K chunks, find out how many blocks there will be. int blockSize = 32768; int numBlocks = facSrc.GetNumBlocks(blockSize); // Open an output file for the decompressed data. string restoredPath = "qa_output/hamlet_restored.xml"; success = facDest.OpenForWrite(restoredPath); if (success != true) { Debug.WriteLine(facDest.LastErrorText); return; } string decompressedStr; byte[] compressedBytes = null; int i = 0; while (i < numBlocks) { compressedBytes = facSrc.ReadBlock(i,blockSize); if (i == 0) { decompressedStr = compress.BeginDecompressString(compressedBytes); } else { decompressedStr = compress.MoreDecompressString(compressedBytes); } facDest.AppendText(decompressedStr,"utf-8"); i = i + 1; } // At the very end, flush any remaining content, if any. decompressedStr = compress.EndDecompressString(); facDest.AppendText(decompressedStr,"utf-8"); facSrc.FileClose(); facDest.FileClose(); // Examine the size of the restored file. Debug.WriteLine("restored size: " + Convert.ToString(fac.FileSize(restoredPath))); // Compare the contents of the original with the restored. bool bEqualContents = fac.FileContentsEqual(restoredPath,originalPath); Debug.WriteLine("Contents Equal: " + Convert.ToString(bEqualContents)); |
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