Ichthyostega
3bfe8f33e0
Since each `TestFrame` now has a metadata header, we can store an additional data checksum there, so that it is now possible both to detect if data is in pristine state, or if it matches a changed state recorded in the additional checksum. So we have now three different levels of verification isSane:: consistent metadata header found isValid:: metadata header found and checksum there matches data isPristine:: in addition, the data is exactly as generated from the `(frameNr,family)`
466 lines
14 KiB
C++
466 lines
14 KiB
C++
/*
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TestFrame - test data frame (stub) for checking Render engine functionality
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Copyright (C)
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2011, Hermann Vosseler <Ichthyostega@web.de>
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**Lumiera** is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the
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Free Software Foundation; either version 2 of the License, or (at your
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option) any later version. See the file COPYING for further details.
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* *****************************************************************/
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/** @file testframe.cpp
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** Implementation of fake data frames to support unit testing.
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** The data generation is based on a _discriminator seed value,_
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** which is computed as a linear combination of a statically fixed anchor-seed
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** combined with the family-number and sequence number. Based on this seed,
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** the contents are then filled by a pseudo-random sequence.
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** @note while initially drawn from real entropy, the anchor-seed can be
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** reset from the default PRNG, which allows to establish a totally
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** deterministically setup from test code, because the test itself
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** can seed the default PRNG and thus establish a reproducible state.
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**
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** Additionally, beyond this basic test-data feature, the contents can be
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** manipulated freely, and a new checksum can be stored in the metadata,
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** which allows to build pseudo media computation functions with a
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** reproducible effect — so that the proper invocation of several
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** computation steps invoked deep down in the render engine can
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** be verified after completing a test invocation.
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*/
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#include "lib/error.hpp"
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#include "lib/random.hpp"
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#include "lib/hash-standard.hpp"
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#include "lib/hash-combine.hpp"
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#include "steam/engine/testframe.hpp"
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#include "lib/nocopy.hpp"
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#include "lib/util.hpp"
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#include <climits>
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#include <memory>
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#include <vector>
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namespace steam {
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namespace engine{
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namespace test {
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namespace err = lumiera::error;
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using util::unConst;
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using std::vector;
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/** @note using a random-congruential engine to generate the payload data */
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using PseudoRandom = lib::RandomSequencer<std::minstd_rand>;
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namespace error = lumiera::error;
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namespace { // hidden local support facilities....
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/**
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* Offset to set the seed values of »families« apart.
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* The data in the test frames is generated from a distinctive ID-seed,
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* which is controlled by the _family_ and the _seq-No_ within each family.
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* The seeds for consecutive frames are spread apart by the #dataSeed,
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* and the SEQUENCE_SPREAD constant acts as minimum spread. While seed
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* values can wrap within the 64bit number range, this generation scheme
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* makes it very unlikely that neighbouring frames end up with the same seed.
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*/
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const size_t SEQUENCE_SPREAD = 100;
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HashVal
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drawSeed (lib::Random& srcGen)
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{
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return srcGen.distribute(
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std::uniform_int_distribution<HashVal>{SEQUENCE_SPREAD
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,std::numeric_limits<HashVal>::max()-SEQUENCE_SPREAD});
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}
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/** @internal a static seed hash used to anchor the data distinction ID-seeds */
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HashVal dataSeed{drawSeed(lib::entropyGen)};
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/** @internal helper for generating unique test frames.
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* This »discriminator« is used as a random seed when filling the test frame data buffers.
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* It is generated to be very likely different on adjacent frames of the same series,
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* as well as to differ to all nearby neighbouring channels.
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* @note the #dataSeed hash is limited by #SEQUENCE_SPREAD to prevent „risky“ families;
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* the extreme case would be dataSeed+family ≡ 0 (all frames would be equal then)
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* @param seq the sequence number of the frame within the channel
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* @param family the channel this frame belongs to
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*/
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uint64_t
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generateDiscriminator(uint seq, uint family)
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{
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// use the family as stepping
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return (seq+1) * (dataSeed+family);
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}
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class DistinctNucleus
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: public lib::SeedNucleus
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, util::MoveOnly
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{
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uint64_t const& fixPoint_;
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public:
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DistinctNucleus(uint64_t const& anchor)
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: fixPoint_{anchor}
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{ }
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uint64_t
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getSeed() override
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{
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return fixPoint_;
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}
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};
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/** @return a stable characteristic memory marker for the metadata record */
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HashVal
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stampHeader()
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{
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static const HashVal MARK = lib::entropyGen.hash()
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| 0b1000'1000'1000'1000'1000'1000'1000'1000; //////////////////////////////TICKET #722 : not portable because HashVal ≡ size_t — should it be?
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return MARK;
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}
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/** @internal build a PRNG starting from the referred fixed seed */
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auto
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buildDataGenFrom (uint64_t const& anchor)
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{
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DistinctNucleus seed{anchor};
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return PseudoRandom{seed};
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}
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TestFrame&
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accessAsTestFrame (void* memoryLocation)
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{
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REQUIRE (memoryLocation);
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return *reinterpret_cast<TestFrame*> (memoryLocation);
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}
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/**
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* @internal table to hold test data frames.
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* These frames are built on demand, but retained thereafter.
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* Some tests might rely on the actual memory locations, using the
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* test frames to simulate a real input frame data stream.
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* @param CHA the maximum number of channels to expect
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* @param FRA the maximum number of frames to expect per channel
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* @warning choose the maximum number parameters wisely.
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* We're allocating memory to hold a table of test frames
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* e.g. sizeof(TestFrame) * 20channels * 100frames ≈ 2 MiB
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* The table uses vectors, and thus will grow on demand,
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* but this might cause existing frames to be relocated in memory;
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* some tests might rely on fixed memory locations. Just be cautious!
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*/
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template<uint CHA, uint FRA>
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struct TestFrameTable
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: vector<vector<TestFrame>>
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{
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typedef vector<vector<TestFrame>> VECT;
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TestFrameTable()
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: VECT(CHA)
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{
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for (uint i=0; i<CHA; ++i)
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at(i).reserve(FRA);
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}
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TestFrame&
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getFrame (uint seqNr, uint chanNr=0)
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{
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if (chanNr >= this->size())
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{
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WARN (test, "Growing table of test frames to %d channels, "
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"which is > the default (%d)", chanNr, CHA);
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resize(chanNr+1);
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}
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ENSURE (chanNr < this->size());
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vector<TestFrame>& channel = at(chanNr);
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if (seqNr >= channel.size())
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{
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WARN_IF (seqNr >= FRA, test,
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"Growing channel #%d of test frames to %d elements, "
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"which is > the default (%d)", chanNr, seqNr, FRA);
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for (uint i=channel.size(); i<=seqNr; ++i)
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channel.push_back (TestFrame (i,chanNr));
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}
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ENSURE (seqNr < channel.size());
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return channel[seqNr];
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}
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};
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const uint INITIAL_CHAN = 20;
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const uint INITIAL_FRAMES = 100;
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typedef TestFrameTable<INITIAL_CHAN,INITIAL_FRAMES> TestFrames;
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std::unique_ptr<TestFrames> testFrames;
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TestFrame&
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accessTestFrame (uint seqNr, uint chanNr)
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{
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if (!testFrames) testFrames.reset (new TestFrames);
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return testFrames->getFrame(seqNr,chanNr);
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}
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} // (End) hidden impl details
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TestFrame&
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testData (uint seqNr, uint chanNr)
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{
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return accessTestFrame (seqNr,chanNr);
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}
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/**
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* @remark this function should be invoked at the start of any test
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* which requires reproducible data values in the TestFrame.
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* It generates a new base seed to distinguish individual data frames.
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* The seed is drawn from the \ref lib::defaultGen, and thus will be
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* reproducible if the latter has been reseeded beforehand.
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* @warning after invoking reseed(), the validity of previously generated
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* frames can no longer be verified.
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*/
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void
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TestFrame::reseed()
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{
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testFrames.reset();
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dataSeed = drawSeed (lib::defaultGen);
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}
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/* ===== TestFrame class ===== */
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TestFrame::Meta::Meta (uint seq, uint family)
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: _MARK_{stampHeader()}
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, checksum{0}
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, distinction{generateDiscriminator (seq,family)}
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, stage{CREATED}
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{ }
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TestFrame::~TestFrame()
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{
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header_.stage = DISCARDED;
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}
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TestFrame::TestFrame (uint seq, uint family)
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: header_{seq,family}
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{
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buildData();
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ASSERT (0 < header_.distinction);
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ENSURE (CREATED == header_.stage);
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ENSURE (isPristine());
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}
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TestFrame::TestFrame (TestFrame const& o)
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: header_{o.header_}
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{
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data() = o.data();
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header_.stage = CREATED;
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}
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TestFrame&
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TestFrame::operator= (TestFrame const& o)
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{
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if (not isAlive())
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throw err::Logic ("target TestFrame already dead or unaccessible");
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if (not util::isSameAdr (this, o))
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{
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data() = o.data();
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header_ = o.header_;
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header_.stage = CREATED;
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}
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return *this;
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}
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/**
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* Sanity check on the metadata header.
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* @remark Relevant to detect memory corruption or when accessing some
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* arbitrary memory location, which may or may not actually hold a TestFrame.
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* Based on the assumption that it is unlikely that some random memory location
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* just happens to hold our [marker word](\ref stampHeader()).
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* @note this is only the base level of verification, because in addition
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* \ref isValid verifies the checksum and \ref isPristine additionally
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* recomputes the data generation to see if it matches the Meta::distinction
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*/
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bool
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TestFrame::Meta::isPlausible() const
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{
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return _MARK_ == stampHeader()
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and stage <= DISCARDED;
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}
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TestFrame::Meta&
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TestFrame::accessHeader()
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{
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if (not header_.isPlausible())
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throw err::Invalid{"TestFrame: missing or corrupted metadata"};
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return header_;
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}
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TestFrame::Meta const&
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TestFrame::accessHeader() const
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{
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return unConst(this)->accessHeader();
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}
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TestFrame::StageOfLife
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TestFrame::currStage() const
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{
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return header_.isPlausible()? header_.stage
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: DISCARDED;
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}
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bool
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TestFrame::operator== (void* memLocation) const
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{
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TestFrame& candidate (accessAsTestFrame (memLocation));
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return candidate.isSane()
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&& candidate == *this;
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}
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bool
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TestFrame::Meta::operator== (Meta const&o) const
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{
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return isPlausible() and o.isPlausible()
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and stage == o.stage
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and checksum == o.checksum
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and distinction == o.distinction;
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}
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bool
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TestFrame::contentEquals (TestFrame const& o) const
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{
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return header_ == o.header_
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and data() == o.data();
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}
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/**
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* Generate baseline data content based on the Meta::distinction seed.
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* @remark the seed is a [discriminator](\ref buildDiscriminator) based
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* on both the »family« and the frameNo within this family;
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* thus closely related frames are very unlikely to hold the same
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* baseline data. Of course, follow-up manipulations could change
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* the data, which should be documented by \ref markChecksum().
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*/
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void
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TestFrame::buildData()
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{
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auto gen = buildDataGenFrom (accessHeader().distinction);
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for (char& dat : data())
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dat = char(gen.i(CHAR_MAX));
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markChecksum();
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}
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/** verify the current data was not touched since initialisation
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* @remark implemented by regenerating the data sequence deterministically,
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* based on the Meta::distinction mark recorded in the metadata.
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*/
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bool
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TestFrame::matchDistinction() const
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{
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auto gen = buildDataGenFrom (accessHeader().distinction);
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for (char const& dat : data())
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if (dat != char(gen.i(CHAR_MAX)))
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return false;
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return true;
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}
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/** @return a hash checksum computed over current data content */
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HashVal
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TestFrame::computeChecksum() const
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{
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HashVal checksum{0};
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std::hash<char> getHash;
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for (char const& dat : data())
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lib::hash::combine (checksum, getHash (dat));
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return checksum;
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}
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/** @remark can be used to mark a manipulated new content as _valid_ */
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HashVal
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TestFrame::markChecksum()
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{
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return accessHeader().checksum = computeChecksum();
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}
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bool
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TestFrame::hasValidChecksum() const
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{
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return accessHeader().checksum == computeChecksum();
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}
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bool
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TestFrame::isSane() const
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{
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return header_.isPlausible();
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}
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bool
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TestFrame::isValid() const
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{
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return isSane()
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and hasValidChecksum();
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}
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bool
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TestFrame::isPristine() const
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{
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return isValid()
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and matchDistinction();
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}
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bool
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TestFrame::isAlive() const
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{
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return isSane()
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and not isDead();
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}
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bool
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TestFrame::isDead() const
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{
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return isSane()
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and (DISCARDED == currStage());
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}
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/** @note performing an unchecked conversion of the given
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* memory location to be accessed as TestFrame.
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* The sanity of the data found at that location
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* is checked as well, not only the lifecycle flag.
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*/
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bool
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TestFrame::isAlive (void* memLocation)
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{
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TestFrame& candidate (accessAsTestFrame (memLocation));
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return candidate.isAlive();
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}
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bool
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TestFrame::isDead (void* memLocation)
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{
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TestFrame& candidate (accessAsTestFrame (memLocation));
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return candidate.isDead();
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}
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}}} // namespace steam::engine::test
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