Reduce PatchWriterInterface functionality.

The recently introduced PatchWriterInterface had both the patch file
format logic and the diff/extra streams selection from the control
entries. While this simplifies the bsdiff main algorithm and makes
invalid usages of the BsdiffPatchWriter evident, writing alternative
PatchWriterInterface classes required to replicate the diff/extra
stream selection logic.

This patch splits out the diff/extra stream generation and all the
checks around those to a new helper class DiffEncoder. The public
interface PatchWriterInterface now has two methods to accept the diff
and extra stream data, and does not compute them.

Bug: 34220646
Test: Added unittests. Ran bsdiff on some pairs of files obtaining the same result as before.
Change-Id: I5f303c06f1e10910eb00dcfda38c6811977a91cf

1 files changed, 15 insertions, 12 deletions

diff --git a/fake_patch_writer.h b/fake_patch_writer.h
index bfbc1e1..4c99928 100644
--- a/fake_patch_writer.h
+++ b/fake_patch_writer.h
@@ -20,14 +20,9 @@ class FakePatchWriter : public PatchWriterInterface {
   ~FakePatchWriter() override = default;
 
   // PatchWriterInterface overrides.
-  bool InitializeBuffers(const uint8_t* old_buf,
-                         uint64_t old_size,
-                         const uint8_t* new_buf,
-                         uint64_t new_size) override {
+  bool Init() override {
     EXPECT_FALSE(initialized_);
     initialized_ = true;
-    new_size_ = new_size;
-    old_size_ = old_size;
     return true;
   }
 
@@ -38,6 +33,16 @@ class FakePatchWriter : public PatchWriterInterface {
     return true;
   }
 
+  bool WriteDiffStream(const uint8_t* data, size_t size) override {
+    diff_stream_.insert(diff_stream_.end(), data, data + size);
+    return true;
+  }
+
+  bool WriteExtraStream(const uint8_t* data, size_t size) override {
+    extra_stream_.insert(extra_stream_.end(), data, data + size);
+    return true;
+  }
+
   bool Close() override {
     EXPECT_FALSE(closed_) << "Close() already called";
     closed_ = true;
@@ -46,22 +51,20 @@ class FakePatchWriter : public PatchWriterInterface {
 
   // Fake getter methods.
   const std::vector<ControlEntry>& entries() const { return entries_; }
-
-  uint64_t new_size() const { return new_size_; }
-  uint64_t old_size() const { return old_size_; }
+  const std::vector<uint8_t>& diff_stream() const { return diff_stream_; }
+  const std::vector<uint8_t>& extra_stream() const { return extra_stream_; }
 
  private:
   // The list of ControlEntry passed to this class.
   std::vector<ControlEntry> entries_;
+  std::vector<uint8_t> diff_stream_;
+  std::vector<uint8_t> extra_stream_;
 
   // Whether this class was initialized.
   bool initialized_{false};
 
   // Whether the patch was closed.
   bool closed_{false};
-
-  uint64_t new_size_;
-  uint64_t old_size_;
 };
 
 }  // namespace bsdiff