Move Courgette...

courgette/ensemble_create.cc

+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// The main idea in Courgette is to do patching *under a tranformation*.  The
+// input is transformed into a new representation, patching occurs in the new
+// repesentation, and then the tranform is reversed to get the patched data.
+//
+// The idea is applied to pieces (or 'elements') of the whole (or 'ensemble').
+// Each of the elements has to go through the same set of steps in lock-step.
+
+// This file contains the code to create the patch.
+
+
+#include "courgette/ensemble.h"
+
+#include <vector>
+#include <limits>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "base/time.h"
+
+#include "courgette/third_party/bsdiff.h"
+#include "courgette/crc.h"
+#include "courgette/difference_estimator.h"
+#include "courgette/image_info.h"
+#include "courgette/streams.h"
+#include "courgette/region.h"
+#include "courgette/simple_delta.h"
+
+#include "courgette/win32_x86_patcher.h"
+#include "courgette/win32_x86_generator.h"
+
+namespace courgette {
+
+TransformationPatchGenerator::TransformationPatchGenerator(
+    Element* old_element,
+    Element* new_element,
+    TransformationPatcher* patcher)
+    : old_element_(old_element),
+      new_element_(new_element),
+      patcher_(patcher) {
+}
+
+TransformationPatchGenerator::~TransformationPatchGenerator() {
+  delete patcher_;
+}
+
+// The default implementation of PredictTransformParameters delegates to the
+// patcher.
+Status TransformationPatchGenerator::PredictTransformParameters(
+    SinkStreamSet* prediction) {
+  return patcher_->PredictTransformParameters(prediction);
+}
+
+// The default implementation of Reform delegates to the patcher.
+Status TransformationPatchGenerator::Reform(
+    SourceStreamSet* transformed_element,
+    SinkStream* reformed_element) {
+  return patcher_->Reform(transformed_element, reformed_element);
+}
+
+// Makes a TransformationPatchGenerator of the appropriate variety for the
+// Element kind.
+TransformationPatchGenerator* MakeGenerator(Element* old_element,
+                                            Element* new_element) {
+  if (new_element->kind() == Element::WIN32_X86_WITH_CODE) {
+    CourgetteWin32X86PatchGenerator* generator =
+        new CourgetteWin32X86PatchGenerator(
+            old_element,
+            new_element,
+            new CourgetteWin32X86Patcher(old_element->region()));
+    return generator;
+  } else {
+    LOG(WARNING) << "Unexpected Element::Kind " << old_element->kind();
+    return NULL;
+  }
+}
+
+// FindGenerators finds TransformationPatchGenerators for the elements of
+// |new_ensemble|.  For each element of |new_ensemble| we find the closest
+// matching element from |old_ensemble| and use that as the basis for
+// differential compression.  The elements have to be the same kind so as to
+// support transformation into the same kind of 'new representation'.
+//
+Status FindGenerators(Ensemble* old_ensemble, Ensemble* new_ensemble,
+                      std::vector<TransformationPatchGenerator*>* generators) {
+  base::Time start_find_time = base::Time::Now();
+  old_ensemble->FindEmbeddedElements();
+  new_ensemble->FindEmbeddedElements();
+  LOG(INFO) << "done FindEmbeddedElements "
+            << (base::Time::Now() - start_find_time).InSecondsF();
+
+  std::vector<Element*> old_elements(old_ensemble->elements());
+  std::vector<Element*> new_elements(new_ensemble->elements());
+
+  LOG(INFO) << "old has " << old_elements.size() << " elements";
+  LOG(INFO) << "new has " << new_elements.size() << " elements";
+
+  DifferenceEstimator difference_estimator;
+  std::vector<DifferenceEstimator::Base*> bases;
+
+  base::Time start_bases_time = base::Time::Now();
+  for (size_t i = 0;  i < old_elements.size();  ++i) {
+    bases.push_back(
+        difference_estimator.MakeBase(old_elements[i]->region()));
+  }
+  LOG(INFO) << "done make bases "
+            << (base::Time::Now() - start_bases_time).InSecondsF()
+            << "s";
+
+  for (size_t new_index = 0;  new_index < new_elements.size();  ++new_index) {
+    Element* new_element = new_elements[new_index];
+    DifferenceEstimator::Subject* new_subject =
+        difference_estimator.MakeSubject(new_element->region());
+
+    // Search through old elements to find the best match.
+    //
+    // TODO(sra): This is O(N x M), i.e. O(N^2) since old_ensemble and
+    // new_ensemble probably have a very similar structure.  We can make the
+    // search faster by making the comparison provided by DifferenceEstimator
+    // more nuanced, returning early if the measured difference is greater than
+    // the current best.  This will be most effective if we can arrange that the
+    // first elements we try to match are likely the 'right' ones.  We could
+    // prioritize elements that are of a similar size or similar position in the
+    // sequence of elements.
+    //
+    Element* best_old_element = NULL;
+    size_t best_difference = std::numeric_limits<size_t>::max();
+    for (size_t old_index = 0;  old_index < old_elements.size();  ++old_index) {
+      Element* old_element = old_elements[old_index];
+      // Elements of different kinds are incompatible.
+      if (old_element->kind() != new_element->kind())
+        continue;
+
+      base::Time start_compare = base::Time::Now();
+      DifferenceEstimator::Base* old_base = bases[old_index];
+      size_t difference = difference_estimator.Measure(old_base, new_subject);
+
+      LOG(INFO) << "Compare " << old_element->Name()
+                << " to " << new_element->Name()
+                << " --> " << difference
+                << " in " << (base::Time::Now() - start_compare).InSecondsF()
+                << "s";
+      if (difference == 0) {
+        LOG(INFO) << "Skip " << new_element->Name()
+                  << " - identical to " << old_element->Name();
+        best_difference = 0;
+        best_old_element = NULL;
+        break;
+      }
+      if (difference < best_difference) {
+        best_difference = difference;
+        best_old_element = old_element;
+      }
+    }
+
+    if (best_old_element) {
+      LOG(INFO) << "Matched " << best_old_element->Name()
+                << " to " << new_element->Name()
+                << " --> " << best_difference;
+      TransformationPatchGenerator* generator =
+          MakeGenerator(best_old_element, new_element);
+      if (generator)
+        generators->push_back(generator);
+    }
+  }
+
+  LOG(INFO) << "done FindGenerators "
+            << "found " << generators->size() << " in "
+            << (base::Time::Now() - start_find_time).InSecondsF() << "s";
+
+  return C_OK;
+}
+
+void FreeGenerators(std::vector<TransformationPatchGenerator*>* generators) {
+  for (size_t i = 0;  i < generators->size();  ++i) {
+    delete (*generators)[i];
+  }
+  generators->clear();
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+Status GenerateEnsemblePatch(SourceStream* base,
+                             SourceStream* update,
+                             SinkStream* final_patch) {
+  Region old_region(base->Buffer(), base->Remaining());
+  Region new_region(update->Buffer(), update->Remaining());
+  Ensemble old_ensemble(old_region, "old");
+  Ensemble new_ensemble(new_region, "new");
+  std::vector<TransformationPatchGenerator*> generators;
+  Status generators_status = FindGenerators(&old_ensemble, &new_ensemble,
+                                            &generators);
+  if (generators_status != C_OK)
+    return generators_status;
+
+  SinkStreamSet patch_streams;
+
+  SinkStream* tranformation_descriptions      = patch_streams.stream(0);
+  SinkStream* parameter_correction            = patch_streams.stream(1);
+  SinkStream* transformed_elements_correction = patch_streams.stream(2);
+  SinkStream* ensemble_correction             = patch_streams.stream(3);
+
+  uint32 number_of_transformations = generators.size();
+  tranformation_descriptions->WriteVarint32(number_of_transformations);
+
+  for (size_t i = 0;  i < number_of_transformations;  ++i) {
+    CourgettePatchFile::TransformationMethodId kind = generators[i]->Kind();
+    tranformation_descriptions->WriteVarint32(kind);
+  }
+
+  for (size_t i = 0;  i < number_of_transformations;  ++i) {
+    Status status =
+        generators[i]->WriteInitialParameters(tranformation_descriptions);
+    if (status != C_OK)
+      return status;
+  }
+
+  //
+  // Generate sub-patch for parameters.
+  //
+  SinkStreamSet predicted_parameters_sink;
+  SinkStreamSet corrected_parameters_sink;
+
+  for (size_t i = 0;  i < number_of_transformations;  ++i) {
+    SinkStreamSet single_predicted_parameters;
+    Status status;
+    status = generators[i]->PredictTransformParameters(
+        &single_predicted_parameters);
+    if (status != C_OK)
+      return status;
+    if (!predicted_parameters_sink.WriteSet(&single_predicted_parameters))
+      return C_STREAM_ERROR;
+
+    SinkStreamSet single_corrected_parameters;
+    status = generators[i]->CorrectedTransformParameters(
+        &single_corrected_parameters);
+    if (status != C_OK)
+      return status;
+    if (!corrected_parameters_sink.WriteSet(&single_corrected_parameters))
+      return C_STREAM_ERROR;
+  }
+
+  SinkStream linearized_predicted_parameters;
+  SinkStream linearized_corrected_parameters;
+
+  if (!predicted_parameters_sink.CopyTo(&linearized_predicted_parameters))
+    return C_STREAM_ERROR;
+  if (!corrected_parameters_sink.CopyTo(&linearized_corrected_parameters))
+    return C_STREAM_ERROR;
+
+  SourceStream predicted_parameters_source;
+  SourceStream corrected_parameters_source;
+  predicted_parameters_source.Init(linearized_predicted_parameters);
+  corrected_parameters_source.Init(linearized_corrected_parameters);
+
+  Status delta1_status = GenerateSimpleDelta(&predicted_parameters_source,
+                                             &corrected_parameters_source,
+                                             parameter_correction);
+  if (delta1_status != C_OK)
+    return delta1_status;
+
+  //
+  // Generate sub-patch for elements.
+  //
+  corrected_parameters_source.Init(linearized_corrected_parameters);
+  SourceStreamSet corrected_parameters_source_set;
+  if (!corrected_parameters_source_set.Init(&corrected_parameters_source))
+    return C_STREAM_ERROR;
+
+  SinkStreamSet predicted_transformed_elements;
+  SinkStreamSet corrected_transformed_elements;
+
+  for (size_t i = 0;  i < number_of_transformations;  ++i) {
+    SourceStreamSet single_parameters;
+    if (!corrected_parameters_source_set.ReadSet(&single_parameters))
+      return C_STREAM_ERROR;
+    SinkStreamSet single_predicted_transformed_element;
+    SinkStreamSet single_corrected_transformed_element;
+    Status status = generators[i]->Transform(
+        &single_parameters,
+        &single_predicted_transformed_element,
+        &single_corrected_transformed_element);
+    if (status != C_OK)
+      return status;
+    if (!single_parameters.Empty())
+      return C_STREAM_NOT_CONSUMED;
+    if (!predicted_transformed_elements.WriteSet(
+            &single_predicted_transformed_element))
+      return C_STREAM_ERROR;
+    if (!corrected_transformed_elements.WriteSet(
+            &single_corrected_transformed_element))
+      return C_STREAM_ERROR;
+  }
+
+  if (!corrected_parameters_source_set.Empty())
+    return C_STREAM_NOT_CONSUMED;
+
+  SinkStream linearized_predicted_transformed_elements;
+  SinkStream linearized_corrected_transformed_elements;
+
+  if (!predicted_transformed_elements.CopyTo(
+          &linearized_predicted_transformed_elements))
+    return C_STREAM_ERROR;
+  if (!corrected_transformed_elements.CopyTo(
+          &linearized_corrected_transformed_elements))
+    return C_STREAM_ERROR;
+
+  SourceStream predicted_transformed_elements_source;
+  SourceStream corrected_transformed_elements_source;
+  predicted_transformed_elements_source
+      .Init(linearized_predicted_transformed_elements);
+  corrected_transformed_elements_source
+      .Init(linearized_corrected_transformed_elements);
+
+  Status delta2_status =
+      GenerateSimpleDelta(&predicted_transformed_elements_source,
+                          &corrected_transformed_elements_source,
+                          transformed_elements_correction);
+  if (delta2_status != C_OK)
+    return delta2_status;
+
+  //
+  // Generate sub-patch for whole enchilada.
+  //
+  SinkStream predicted_ensemble;
+
+  predicted_ensemble.Write(base->Buffer(), base->Remaining());
+
+  SourceStreamSet corrected_transformed_elements_source_set;
+  corrected_transformed_elements_source
+      .Init(linearized_corrected_transformed_elements);
+  if (!corrected_transformed_elements_source_set
+      .Init(&corrected_transformed_elements_source))
+    return C_STREAM_ERROR;
+
+  for (size_t i = 0;  i < number_of_transformations;  ++i) {
+    SourceStreamSet single_corrected_transformed_element;
+    if (!corrected_transformed_elements_source_set.ReadSet(
+            &single_corrected_transformed_element))
+      return C_STREAM_ERROR;
+    Status status = generators[i]->Reform(&single_corrected_transformed_element,
+                                          &predicted_ensemble);
+    if (status != C_OK)
+      return status;
+    if (!single_corrected_transformed_element.Empty())
+      return C_STREAM_NOT_CONSUMED;
+  }
+
+  if (!corrected_transformed_elements_source_set.Empty())
+    return C_STREAM_NOT_CONSUMED;
+
+  FreeGenerators(&generators);
+
+  SourceStream predicted_ensemble_source;
+  predicted_ensemble_source.Init(predicted_ensemble);
+  Status delta3_status = GenerateSimpleDelta(&predicted_ensemble_source,
+                                             update,
+                                             ensemble_correction);
+  if (delta3_status != C_OK)
+    return delta3_status;
+
+  //
+  // Final output stream has a header followed by a StreamSet.
+  //
+  final_patch->WriteVarint32(CourgettePatchFile::kMagic);
+  final_patch->WriteVarint32(CourgettePatchFile::kVersion);
+
+  final_patch->WriteVarint32(
+      CalculateCrc(old_region.start(), old_region.length()));
+  final_patch->WriteVarint32(
+      CalculateCrc(new_region.start(), new_region.length()));
+
+  if (!patch_streams.CopyTo(final_patch))
+    return C_STREAM_ERROR;
+
+  return C_OK;
+}
+
+}  // namespace