如何在libexif

Question

libexif保存标签字符串数据时遇到问题。我正在使用strcpy为字符串值分配内存，然后仅将assiggn指针指向特定标签entry-> data。问题是-使用exif_data_save_data和fwrite保存时，我将字符串值切成7个字符。如果我首先从具有较长字符串值的文件中为此特定的exif标记（尤其是EXIF_TAG_NAME）加载所有这些数据，则最大字符串len coud会有所不同。

static char* get_c_str(QString qs)
{
    QByteArray *qba = new QByteArray(qs.toLatin1());
    char* str = (char *)malloc(qba->count());
    strcpy(str,qba->data());

    return str;
}


static ExifEntry *init_tag(ExifData *exif, ExifIfd ifd, ExifTag tag)
{
    ExifEntry *entry;

    if (!((entry = exif_content_get_entry (exif->ifd[ifd], tag)))) {

        entry = exif_entry_new ();
        assert(entry != NULL); 
        entry->tag = tag;

        exif_content_add_entry (exif->ifd[ifd], entry);

        exif_entry_initialize (entry, tag);

        exif_entry_unref(entry);
    }
    return entry;
}

void MainWindow::on_writeButton_clicked()
{
    if(!buf)
        return;

    ent = init_tag(ed,ExifIfd::EXIF_IFD_0,ExifTag::EXIF_TAG_MODEL);
    ent->data = (unsigned char*)get_c_str(ui->modelL->text());

    ................................................

    exif_data_save_data(ed, &exifData, &exifDatLen);

    f = fopen(path, "wb");

    fwrite(exif_header,exif_header_len,1,f);

    fputc((exifDatLen+2)>>8,f);
    fputc((exifDatLen+2) & 0xff, f);

    fwrite(exifData,exifDatLen,1,f);
    fwrite(buf+image_data_offset,flen,1,f);

    fclose(f);
}

预计相机型号为“ Canon EOS 5D Mark II”，但为“ Canon E”