Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>It seems you are misunderstanding pointer arithmetic</p> <pre><code>cb-&gt;buffer_end = (DataFragment *)cb-&gt;buffer + (capacity-1)*sz; cb-&gt;head = (DataFragment*)cb-&gt;head + cb-&gt;sz; cb-&gt;tail = (DataFragment*)cb-&gt;tail + cb-&gt;sz; </code></pre> <p>Pointer arithmetic already takes into account the size of the underlying type. All you really need is</p> <pre><code>++cb-&gt;head; ++cb-&gt;tail; </code></pre> <hr> <p>If the idea is to hack around <code>sizeof(DataFragment)</code> - perhaps to allocate more storage for one item than the struct's size - for some evil purpose - you'll need to first cast the pointer to a <code>char*</code> (because <code>sizeof(char) == 1</code>).</p> <pre><code>cb-&gt;tail = (DataFragment*)((char*)cb-&gt;tail + cb-&gt;sz); </code></pre> <hr> <p>Design-wise the struct appears to have too many members: <code>buffer_end</code> and <code>capacity</code> duplicate each other (given one you can always find the other), and the <code>sz</code> member is not necessary (it should always be <code>sizeof(DataFragment)</code>.</p> <p>Also, I believe you can just assign structs</p> <pre><code>*(cb-&gt;head) = *item; </code></pre> <p>there seem to be completely unnecessary casts (probably resulting from the misunderstanding of pointer arithmetic):</p> <pre><code>cb-&gt;buffer_end = (DataFragment *)cb-&gt;buffer + (capacity-1)*sz; </code></pre> <p>And if it is supposed to be C++, then it contains lots of "C-isms" (typedeffing structs, using <code>struct XXX var;</code> - despite having it typedeffed, etc), and the code is generally designed in a purely C style (not taking advantage of C++'s greatest strength, automatic resource management with RAII).</p> <hr> <p>May I also point out that <code>clock()</code> hardly gives you a <em>date</em> :)</p>
    singulars
    1. This table or related slice is empty.
    1. POend pointer problem of a circular buffer
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USvisitor
    1. USvisitor
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POend pointer problem of a circular buffer
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    1. COYes I did misunderstood the pointer arithmetic... But, I can't just assign structs like *(cb->head) = *item I need to copy data not addresses from a temporary buffer to the circular buffer, so I have to use memcpy..
      singulars
      1. PO
      1. USfsidiosidi
    2. CO@fsidiosidi: Assigning the address would look like this: `cb->head = item;`. What I have shown dereferences the pointers, so you'll be assigning the struct objects themselves.
      singulars
      1. PO
      1. USvisitor
    3. COmmm...ok, but don't you think a binary copy does the job...I don't want to bother myself with casting type...also, the data i'm putting in the item is a raw data comming from the network...
      singulars
      1. PO
      1. USfsidiosidi
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload