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(Node.js) 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. Note: This example requires Chilkat v11.0.0 or greater.
var os = require('os'); if (os.platform() == 'win32') { var chilkat = require('@chilkat/ck-node23-win64'); } else if (os.platform() == 'linux') { if (os.arch() == 'arm') { var chilkat = require('@chilkat/ck-node23-linux-arm'); } else if (os.arch() == 'arm64') { var chilkat = require('@chilkat/ck-node23-linux-arm64'); } else { var chilkat = require('@chilkat/ck-node23-linux-x64'); } } else if (os.platform() == 'darwin') { var chilkat = require('@chilkat/ck-node23-mac-universal'); } function chilkatExample() { var success = false; // 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: var compress = new chilkat.Compression(); compress.Algorithm = "deflate"; success = compress.CompressFile("qa_data/hamlet.xml","qa_data/hamlet_compressed.dat"); if (success == false) { console.log(compress.LastErrorText); return; } var fac = new chilkat.FileAccess(); // Examine the uncompressed and compressed sizes: var 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. console.log("uncompressed size: " + fac.FileSize(originalPath)); console.log("compressed size: " + fac.FileSize("qa_data/hamlet_compressed.dat")); // Decompress in blocks.. var facSrc = new chilkat.FileAccess(); var 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. var blockSize = 32768; var numBlocks = facSrc.GetNumBlocks(blockSize); // Open an output file for the decompressed data. var restoredPath = "qa_output/hamlet_restored.xml"; success = facDest.OpenForWrite(restoredPath); if (success == false) { console.log(facDest.LastErrorText); return; } var decompressedStr; // Assuming numBlocks > 1 compress.FirstChunk = true; compress.LastChunk = false; var i = 0; while (i < numBlocks) { compressedBytes = facSrc.ReadBlock(i,blockSize); decompressedStr = compress.DecompressString(compressedBytes); facDest.AppendText(decompressedStr,"utf-8"); i = i+1; compress.FirstChunk = false; if (i == (numBlocks - 1)) { compress.LastChunk = true; } } facSrc.FileClose(); facDest.FileClose(); // Examine the size of the restored file. console.log("restored size: " + fac.FileSize(restoredPath)); // Compare the contents of the original with the restored. var bEqualContents = fac.FileContentsEqual(restoredPath,originalPath); console.log("Contents Equal: " + bEqualContents); } chilkatExample(); |
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