DataFlex

Determine File Type from Binary Content of File

Note: This example requires Chilkat v9.5.0.64 or later.

Many file types have "signatures" (leading bytes) that signify the type of file. It allows for programs to identify the likely type of file given the first few bytes contained within the file. This example shows how to identify a few common types files. For other file types, you can do a short bit of investigative work by examining the first few bytes of an sample file, and searching the Internet for information about the file type. Use this same technique for handling other file types that have leading "signature" bytes.

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Handle hoFac
    Variant vJpgData
    Handle hoJpgData
    Boolean iSuccess
    Variant vPngData
    Handle hoPngData
    Variant vPdfData
    Handle hoPdfData
    Variant vZipData
    Handle hoZipData
    String sTemp1

    // Note: This example requires Chilkat v9.5.0.64 or later.

    // To identify a file by the first few bytes, we'll load a few bytes from the start
    // of the file, and then examine the bytes as both hex and quoted-printable.

    Get Create (RefClass(cComCkFileAccess)) To hoFac
    If (Not(IsComObjectCreated(hoFac))) Begin
        Send CreateComObject of hoFac
    End

    // A JPG file.
    Get Create (RefClass(cComChilkatBinData)) To hoJpgData
    If (Not(IsComObjectCreated(hoJpgData))) Begin
        Send CreateComObject of hoJpgData
    End
    Get ComOpenForRead Of hoFac "qa_data/jpg/starfish.jpg" To iSuccess
    // The the first 8 bytes of the JPG file.
    Get pvComObject of hoJpgData to vJpgData
    Get ComFileReadBd Of hoFac 8 vJpgData To iSuccess
    Send ComFileClose To hoFac

    // JPG hex: FFD8FFE000104A46
    // JPG qp: =FF=D8=FF=E0=00=10JF
    Get ComGetEncoded Of hoJpgData "hex" To sTemp1
    Showln "JPG hex: " sTemp1
    Get ComGetEncoded Of hoJpgData "qp" To sTemp1
    Showln "JPG qp: " sTemp1

    // A JPG begins with the following two bytes: 0xFF, 0xD8
    // Your program can check to see if the hex string begins with "FFD8", or if the qp string begins with "=FF=D8".

    // ----------------------------------------
    // A PNG file.
    Get Create (RefClass(cComChilkatBinData)) To hoPngData
    If (Not(IsComObjectCreated(hoPngData))) Begin
        Send CreateComObject of hoPngData
    End
    Get ComOpenForRead Of hoFac "qa_data/png/anemone.png" To iSuccess
    // The the first 8 bytes of the PNG file.
    Get pvComObject of hoPngData to vPngData
    Get ComFileReadBd Of hoFac 8 vPngData To iSuccess
    Send ComFileClose To hoFac

    // PNG hex: 89504E470D0A1A0A
    // PNG qp: =89PNG=1A=0A
    Get ComGetEncoded Of hoPngData "hex" To sTemp1
    Showln "PNG hex: " sTemp1
    Get ComGetEncoded Of hoPngData "qp" To sTemp1
    Showln "PNG qp: " sTemp1
    // A PNG file begins with the byte 0x89, followed by the us-ascii bytes "PNG".

    // ----------------------------------------
    // A PDF file.
    Get Create (RefClass(cComChilkatBinData)) To hoPdfData
    If (Not(IsComObjectCreated(hoPdfData))) Begin
        Send CreateComObject of hoPdfData
    End
    Get ComOpenForRead Of hoFac "qa_data/pdf/fishing.pdf" To iSuccess
    // The the first 8 bytes of the PDF file.
    Get pvComObject of hoPdfData to vPdfData
    Get ComFileReadBd Of hoFac 8 vPdfData To iSuccess
    Send ComFileClose To hoFac

    // PDF hex: 255044462D312E33
    // PDF qp: %PDF-1.3
    Get ComGetEncoded Of hoPdfData "hex" To sTemp1
    Showln "PDF hex: " sTemp1
    Get ComGetEncoded Of hoPdfData "qp" To sTemp1
    Showln "PDF qp: " sTemp1
    // A PDF file begins with the us-ascii chars "%PDF"

    // ----------------------------------------
    // A Zip file.
    Get Create (RefClass(cComChilkatBinData)) To hoZipData
    If (Not(IsComObjectCreated(hoZipData))) Begin
        Send CreateComObject of hoZipData
    End
    Get ComOpenForRead Of hoFac "qa_data/zips/test.zip" To iSuccess
    // The the first 8 bytes of the Zip file.
    Get pvComObject of hoZipData to vZipData
    Get ComFileReadBd Of hoFac 8 vZipData To iSuccess
    Send ComFileClose To hoFac

    // PDF hex: 504B030414000000
    // PDF qp: PK=03=04=14=00=00=00
    Get ComGetEncoded Of hoZipData "hex" To sTemp1
    Showln "PDF hex: " sTemp1
    Get ComGetEncoded Of hoZipData "qp" To sTemp1
    Showln "PDF qp: " sTemp1
    // A Zip archive begins with the us-ascii chars "PK" followed by the bytes 0x03, 0x04.


End_Procedure