(Swift 3,4,5...) Decompress Large Text File in Blocks

Decompresses a large text file in blocks, and compares the restored (decompressed) file with the original to make sure it's correct.

Chilkat Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

func chilkatTest() {
    // 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:
    let compress = CkoCompression()!
    compress.algorithm = "deflate"

    var success: Bool = compress.compressFile("qa_data/hamlet.xml", destPath: "qa_data/hamlet_compressed.dat")
    if success != true {
        print("\(compress.lastErrorText!)")
        return
    }

    let fac = CkoFileAccess()!

    // Examine the uncompressed and compressed sizes:
    var originalPath: String? = "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.
    print("uncompressed size: \(fac.fileSize(originalPath).intValue)")
    print("compressed size: \(fac.fileSize("qa_data/hamlet_compressed.dat").intValue)")

    // Decompress in blocks..
    let facSrc = CkoFileAccess()!
    let facDest = CkoFileAccess()!

    facSrc.open(forRead: "qa_data/hamlet_compressed.dat")

    // If we compress in 32K chunks, find out how many blocks there will be.
    var blockSize: Int = 32768
    var numBlocks: Int = facSrc.getNumBlocks(blockSize).intValue

    // Open an output file for the decompressed data.
    var restoredPath: String? = "qa_output/hamlet_restored.xml"
    success = facDest.open(forWrite: restoredPath)
    if success != true {
        print("\(facDest.lastErrorText!)")
        return
    }

    var decompressedStr: String?
    var compressedBytes: NSData

    var i: Int = 0
    while i < numBlocks {
        compressedBytes = facSrc.readBlock(i, blockSize: blockSize)
        if i == 0 {
            decompressedStr = compress.beginDecompressString(compressedBytes)
        }
        else {
            decompressedStr = compress.moreDecompressString(compressedBytes)
        }

        facDest.appendText(decompressedStr, charset: "utf-8")

        i = i + 1
    }

    // At the very end, flush any remaining content, if any.
    decompressedStr = compress.endDecompressString()
    facDest.appendText(decompressedStr, charset: "utf-8")

    facSrc.fileClose()
    facDest.fileClose()

    // Examine the size of the restored file.
    print("restored size: \(fac.fileSize(restoredPath).intValue)")

    // Compare the contents of the original with the restored.
    var bEqualContents: Bool = fac.fileContentsEqual(restoredPath, path2: originalPath)
    print("Contents Equal: \(bEqualContents)")

}