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Question:

Read last n lines using Chilkat FileAccess library

Jul 11 '17 at 10:51

I need to read only the last n lines from the file using Chilkat library (FileAccess) - https://www.chilkatsoft.com/refdoc/xCkFileAccessRef.html. Because the file size would be large(upto 5GB). I can able to read the last few records by using FileStream. But I want to do the same kind of parsing in Chilkat.

Parsing last few records in FileStream:

int sizeOfChar = 1;
Encoding _selectedEncoding = Encoding.ASCII;

using (FileStream fs = new FileStream(filePath, FileMode.Open))
{
    long endPosition = 1024;

    for (long position = sizeOfChar; position < endPosition; position += sizeOfChar)
    {
        fs.Seek(-position, SeekOrigin.End);
    }

    byte[] extractedBuffer = new byte[fs.Length - fs.Position];
    fs.Read(extractedBuffer, 0, extractedBuffer.Length);
    string strTokens = _selectedEncoding.GetString(extractedBuffer);
}

This code is working fine as expected and returns last few lines. I have tried to achieve the same using Chilkat FileAccess class and it returns only empty array.

Parsing last few records in Chilkat.FileAccess:

int sizeOfChar = 1;

Chilkat.FileAccess fa = new Chilkat.FileAccess();
bool isFileOpened = fa.FileOpen(filePath, 0x80000000, 0x00000001, 4, 0x00000080);

int endPosition = 1024;

for (int position = sizeOfChar; position < endPosition; position += sizeOfChar)
{
    fa.FileSeek(-position, (int)SeekOrigin.End);
}

byte[] extractedBuffer = fa.FileRead(endPosition);
string strTokens = _selectedEncoding.GetString(extractedBuffer);

I can able to fetch first few lines using Chilkat but I want to get last few lines. Please check the above code block and anyone help me to parse the last few lines using Chilkat.

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Answer

Thanks! The bug in LastNLines was discovered after the v9.5.0.68 release. I can create an ActiveX pre-release of .69 and post it here later today.

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Answer

This new build should fix the problem:

32-bit: https://chilkatdownload.com/prerelease/chilkatax-9.5.0-win32-168.zip
64-bit: https://chilkatdownload.com/prerelease/chilkatax-9.5.0-x64-169.zip

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Answer

For the FileSeek method, passing SeekOrigin.End is only valid if in fact SeekOrigin.End equals 2. Just pass the number 2. Chilkat is cross-platform/cross-language, so we can't use "SeekOrigin.End" because it doesn't apply across languages. We really need a specific number (i.e. 2 in this case).

Also, I don't quite understand the logic of using a loop. Just seek -1024 from the end if that's what you want..