Databases
StackOverflow2013
Postsdbo
POHow can I safely make a float *x into a const float *const *y?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow can I safely make a float *x into a const float *const *y?
    primarykey
    data
    text
    <p>I have a function <code>audioReceived (float * input, int bufferSize, int nChannels)</code> inside of which I want to call a function from a library that needs <code>const float *const *inputBuffers</code>.</p> <p>Obviously casting <code>const float *const *inputBuffers = (const float* const*)input;</code> compiles but is a terrible idea, crashes the program, kills kittens, etc. Nobody ever needs to modify the original <code>float* input</code>, it's incoming audio data that's being processed.</p> <p>How do I do it the right way?</p> <p><strong>EDIT: Here's some more code.</strong> <code>audioReceived</code> is:</p> <pre><code>void testApp::audioReceived (float * input, int bufferSize, int nChannels){ Vamp::RealTime rt = Vamp::RealTime::fromMilliseconds(ofGetSystemTime()); float const *const tmp[] = { input, 0 }; Vamp::Plugin::FeatureSet fs = myPlugin-&gt;process(tmp, rt); } </code></pre> <p>Library function <code>process</code> is virtually defined in base class:</p> <pre><code> /** * Process a single block of input data. * * If the plugin's inputDomain is TimeDomain, inputBuffers will * point to one array of floats per input channel, and each of * these arrays will contain blockSize consecutive audio samples * (the host will zero-pad as necessary). The timestamp in this * case will be the real time in seconds of the start of the * supplied block of samples. * * If the plugin's inputDomain is FrequencyDomain, inputBuffers * will point to one array of floats per input channel, and each * of these arrays will contain blockSize/2+1 consecutive pairs of * real and imaginary component floats corresponding to bins * 0..(blockSize/2) of the FFT output. That is, bin 0 (the first * pair of floats) contains the DC output, up to bin blockSize/2 * which contains the Nyquist-frequency output. There will * therefore be blockSize+2 floats per channel in total. The * timestamp will be the real time in seconds of the centre of the * FFT input window (i.e. the very first block passed to process * might contain the FFT of half a block of zero samples and the * first half-block of the actual data, with a timestamp of zero). * * Return any features that have become available after this * process call. (These do not necessarily have to fall within * the process block, except for OneSamplePerStep outputs.) */ virtual FeatureSet process(const float *const *inputBuffers, RealTime timestamp) = 0; </code></pre> <p>and here in the actual header:</p> <pre><code>FeatureSet process(const float *const *inputBuffers, Vamp::RealTime timestamp); </code></pre> <p>I think the <code>EXC_BAD_ACCESS</code> may be stemming from the library function wanting a zero-padded array, and my not giving it one. (a) Does that sound reasonable, and (b) If so, is it time to ask a different SO question?</p> <p>Thanks all for your help so far, it's very enlightening/clarifying/educational/interesting.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USbuildsucceeded
    1. USbuildsucceeded
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POHow can I safely make a float *x into a const float *const *y?
      1. This table or related slice is empty.
      1. VTUpMod
    1. COThis doesn't make much sense. You start with a pointer-to-float, and you want to get out of it a pointer-to-pointer-to-float with lots of constness bunged in. Huh?
      singulars
      1. POHow can I safely make a float *x into a const float *const *y?
      1. USLightness Races in Orbit
    2. COWhy does this even have a `c++` tag? Isn't it a pure C question?
      singulars
      1. POHow can I safely make a float *x into a const float *const *y?
      1. USsbi
    3. COTo be honest, when it comes to the `const`s I'm asking "Huh?" as well-- but it's what the feature-extraction library wants and I'm trying to start by giving it what it wants before I start trying to rewrite the library. (Which would probably just lead to more confusion, anyway; my working assumption is that the guy who wrote that code knows a bit more than me-- though perhaps not more than some of you.)
      singulars
      1. POHow can I safely make a float *x into a const float *const *y?
      1. USbuildsucceeded
 

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