Get a Header Attribute of a Related Item

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Demonstrates the Chilkat Email.GetRelatedAttr method, which returns a header-field attribute value from a header field of the Nth related item. The first argument is the zero-based related-item index, the second names a header field, and the third names an attribute within it. This example loads an image from a file into a BinData object, adds it as a related item with AddRelatedBd (capturing the generated Content-ID and referencing it from the HTML), then reads the name attribute of the related item's Content-Type header.

Background: Related items (inline images, style sheets) are MIME parts whose headers may carry named parameters — for instance Content-Type: image/png; name="logo.png". Because an image is binary, it is loaded into a BinData object (here from a file) and added with AddRelatedBd, rather than being treated as text. GetRelatedAttr then extracts one named attribute from a chosen header of a specific related part, the related-item analogue of GetAttachmentAttr, so you don't have to parse the raw header yourself.

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#include <C_CkEmail.h>
#include <C_CkBinData.h>
#include <C_CkStringBuilder.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkEmail email;
    HCkBinData bdImage;
    const char *cid;
    HCkStringBuilder sbHtml;
    int numReplaced;
    const char *val;

    success = FALSE;

    //  Demonstrates the GetRelatedAttr method, which returns a header-field attribute value
    //  from a header field of the Nth related item.  The first argument is the zero-based related-item
    //  index, the second is the header field name, and the third is the attribute name.

    email = CkEmail_Create();
    CkEmail_putSubject(email,"GetRelatedAttr example");

    //  Load the image data from a file into a BinData object.
    bdImage = CkBinData_Create();
    success = CkBinData_LoadFile(bdImage,"qa_data/images/logo.png");
    if (success == FALSE) {
        printf("%s\n",CkBinData_lastErrorText(bdImage));
        CkEmail_Dispose(email);
        CkBinData_Dispose(bdImage);
        return;
    }

    //  Add the image as a related item from the BinData; capture its generated Content-ID.
    cid = CkEmail_addRelatedBd(email,"logo.png",bdImage);
    if (CkEmail_getLastMethodSuccess(email) == FALSE) {
        printf("%s\n",CkEmail_lastErrorText(email));
        CkEmail_Dispose(email);
        CkBinData_Dispose(bdImage);
        return;
    }

    //  Reference the related item in the HTML body by its Content-ID.
    sbHtml = CkStringBuilder_Create();
    CkStringBuilder_Append(sbHtml,"<html><body><img src=\"cid:PLACEHOLDER_CID\"/></body></html>");
    numReplaced = CkStringBuilder_Replace(sbHtml,"PLACEHOLDER_CID",cid);
    CkEmail_SetHtmlBody(email,CkStringBuilder_getAsString(sbHtml));

    //  Get the "name" attribute of the related item's Content-Type header (index 0).
    val = CkEmail_getRelatedAttr(email,0,"Content-Type","name");
    printf("Related item Content-Type name attribute: %s\n",val);

    //  Note: The path "qa_data/images/logo.png" is a relative local filesystem path,
    //  relative to the current working directory of the running application.


    CkEmail_Dispose(email);
    CkBinData_Dispose(bdImage);
    CkStringBuilder_Dispose(sbHtml);

    }