/[svn]/libgig/trunk/src/gig.cpp
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revision 23 by schoenebeck, Thu Dec 25 01:09:08 2003 UTC revision 24 by schoenebeck, Fri Dec 26 16:15:31 2003 UTC
# Line 315  namespace gig { Line 315  namespace gig {
315      }      }
316    
317      /**      /**
318         * Reads \a SampleCount number of sample points from the position stored
319         * in \a pPlaybackState into the buffer pointed by \a pBuffer and moves
320         * the position within the sample respectively, this method honors the
321         * looping informations of the sample (if any). The sample wave stream
322         * will be decompressed on the fly if using a compressed sample. Use this
323         * method if you don't want to load the sample into RAM, thus for disk
324         * streaming. All this methods needs to know to proceed with streaming
325         * for the next time you call this method is stored in \a pPlaybackState.
326         * You have to allocate and initialize the playback_state_t structure by
327         * yourself before you use it to stream a sample:
328         *
329         * <i>
330         * gig::playback_state_t playbackstate;                           <br>
331         * playbackstate.position         = 0;                            <br>
332         * playbackstate.reverse          = false;                        <br>
333         * playbackstate.loop_cycles_left = pSample->LoopPlayCount;       <br>
334         * </i>
335         *
336         * You don't have to take care of things like if there is actually a loop
337         * defined or if the current read position is located within a loop area.
338         * The method already handles such cases by itself.
339         *
340         * @param pBuffer          destination buffer
341         * @param SampleCount      number of sample points to read
342         * @param pPlaybackState   will be used to store and reload the playback
343         *                         state for the next ReadAndLoop() call
344         * @returns                number of successfully read sample points
345         */
346        unsigned long Sample::ReadAndLoop(void* pBuffer, unsigned long SampleCount, playback_state_t* pPlaybackState) {
347            unsigned long samplestoread = SampleCount, totalreadsamples = 0, readsamples, samplestoloopend;
348            uint8_t* pDst = (uint8_t*) pBuffer;
349    
350            SetPos(pPlaybackState->position); // recover position from the last time
351    
352            if (this->Loops && GetPos() <= this->LoopEnd) { // honor looping if there are loop points defined
353    
354                switch (this->LoopType) {
355    
356                    case loop_type_bidirectional: { //TODO: not tested yet!
357                        do {
358                            // if not endless loop check if max. number of loop cycles have been passed
359                            if (this->LoopPlayCount && !pPlaybackState->loop_cycles_left) break;
360    
361                            if (!pPlaybackState->reverse) { // forward playback
362                                do {
363                                    samplestoloopend  = this->LoopEnd - GetPos();
364                                    readsamples       = Read(&pDst[totalreadsamples * this->FrameSize], Min(samplestoread, samplestoloopend));
365                                    samplestoread    -= readsamples;
366                                    totalreadsamples += readsamples;
367                                    if (readsamples == samplestoloopend) {
368                                        pPlaybackState->reverse = true;
369                                        break;
370                                    }
371                                } while (samplestoread && readsamples);
372                            }
373                            else { // backward playback
374    
375                                // as we can only read forward from disk, we have to
376                                // determine the end position within the loop first,
377                                // read forward from that 'end' and finally after
378                                // reading, swap all sample frames so it reflects
379                                // backward playback
380    
381                                unsigned long swapareastart       = totalreadsamples;
382                                unsigned long loopoffset          = GetPos() - this->LoopStart;
383                                unsigned long samplestoreadinloop = Min(samplestoread, loopoffset);
384                                unsigned long reverseplaybackend  = GetPos() - samplestoreadinloop;
385    
386                                SetPos(reverseplaybackend);
387    
388                                // read samples for backward playback
389                                do {
390                                    readsamples          = Read(&pDst[totalreadsamples * this->FrameSize], samplestoreadinloop);
391                                    samplestoreadinloop -= readsamples;
392                                    samplestoread       -= readsamples;
393                                    totalreadsamples    += readsamples;
394                                } while (samplestoreadinloop && readsamples);
395    
396                                SetPos(reverseplaybackend); // pretend we really read backwards
397    
398                                if (reverseplaybackend == this->LoopStart) {
399                                    pPlaybackState->loop_cycles_left--;
400                                    pPlaybackState->reverse = false;
401                                }
402    
403                                // reverse the sample frames for backward playback
404                                SwapMemoryArea(&pDst[swapareastart * this->FrameSize], (totalreadsamples - swapareastart) * this->FrameSize, this->FrameSize);
405                            }
406                        } while (samplestoread && readsamples);
407                        break;
408                    }
409    
410                    case loop_type_backward: { // TODO: not tested yet!
411                        // forward playback (not entered the loop yet)
412                        if (!pPlaybackState->reverse) do {
413                            samplestoloopend  = this->LoopEnd - GetPos();
414                            readsamples       = Read(&pDst[totalreadsamples * this->FrameSize], Min(samplestoread, samplestoloopend));
415                            samplestoread    -= readsamples;
416                            totalreadsamples += readsamples;
417                            if (readsamples == samplestoloopend) {
418                                pPlaybackState->reverse = true;
419                                break;
420                            }
421                        } while (samplestoread && readsamples);
422    
423                        if (!samplestoread) break;
424    
425                        // as we can only read forward from disk, we have to
426                        // determine the end position within the loop first,
427                        // read forward from that 'end' and finally after
428                        // reading, swap all sample frames so it reflects
429                        // backward playback
430    
431                        unsigned long swapareastart       = totalreadsamples;
432                        unsigned long loopoffset          = GetPos() - this->LoopStart;
433                        unsigned long samplestoreadinloop = (this->LoopPlayCount) ? Min(samplestoread, pPlaybackState->loop_cycles_left * LoopSize - loopoffset)
434                                                                                  : samplestoread;
435                        unsigned long reverseplaybackend  = this->LoopStart + Abs((loopoffset - samplestoreadinloop) % this->LoopSize);
436    
437                        SetPos(reverseplaybackend);
438    
439                        // read samples for backward playback
440                        do {
441                            // if not endless loop check if max. number of loop cycles have been passed
442                            if (this->LoopPlayCount && !pPlaybackState->loop_cycles_left) break;
443                            samplestoloopend     = this->LoopEnd - GetPos();
444                            readsamples          = Read(&pDst[totalreadsamples * this->FrameSize], Min(samplestoreadinloop, samplestoloopend));
445                            samplestoreadinloop -= readsamples;
446                            samplestoread       -= readsamples;
447                            totalreadsamples    += readsamples;
448                            if (readsamples == samplestoloopend) {
449                                pPlaybackState->loop_cycles_left--;
450                                SetPos(this->LoopStart);
451                            }
452                        } while (samplestoreadinloop && readsamples);
453    
454                        SetPos(reverseplaybackend); // pretend we really read backwards
455    
456                        // reverse the sample frames for backward playback
457                        SwapMemoryArea(&pDst[swapareastart * this->FrameSize], (totalreadsamples - swapareastart) * this->FrameSize, this->FrameSize);
458                        break;
459                    }
460    
461                    default: case loop_type_normal: {
462                        do {
463                            // if not endless loop check if max. number of loop cycles have been passed
464                            if (this->LoopPlayCount && !pPlaybackState->loop_cycles_left) break;
465                            samplestoloopend  = this->LoopEnd - GetPos();
466                            readsamples       = Read(&pDst[totalreadsamples * this->FrameSize], Min(samplestoread, samplestoloopend));
467                            samplestoread    -= readsamples;
468                            totalreadsamples += readsamples;
469                            if (readsamples == samplestoloopend) {
470                                pPlaybackState->loop_cycles_left--;
471                                SetPos(this->LoopStart);
472                            }
473                        } while (samplestoread && readsamples);
474                        break;
475                    }
476                }
477            }
478    
479            // read on without looping
480            if (samplestoread) do {
481                readsamples = Read(&pDst[totalreadsamples * this->FrameSize], samplestoread);
482                samplestoread    -= readsamples;
483                totalreadsamples += readsamples;
484            } while (readsamples && samplestoread);
485    
486            // store current position
487            pPlaybackState->position = GetPos();
488    
489            return totalreadsamples;
490        }
491    
492        /**
493       * Reads \a SampleCount number of sample points from the current       * Reads \a SampleCount number of sample points from the current
494       * position into the buffer pointed by \a pBuffer and increments the       * position into the buffer pointed by \a pBuffer and increments the
495       * position within the sample. The sample wave stream will be       * position within the sample. The sample wave stream will be

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