From bf89e9876f50487ba87752f0a0cd48a041e08102 Mon Sep 17 00:00:00 2001
From: Jendrik Weise <jewe37@gmail.com>
Date: Fri, 25 Aug 2023 20:51:12 +0200
Subject: [PATCH] Allow not copying the dictionary

---
 src/google/vcencoder.h | 3 ++-
 src/vcdiffengine.cc    | 9 +++++----
 src/vcdiffengine.h     | 4 +++-
 src/vcencoder.cc       | 5 +++--
 4 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/src/google/vcencoder.h b/src/google/vcencoder.h
index 37d6fd6..b04df5b 100644
--- a/src/google/vcencoder.h
+++ b/src/google/vcencoder.h
@@ -38,7 +38,8 @@ class CodeTableWriterInterface;
 class HashedDictionary {
  public:
   HashedDictionary(const char* dictionary_contents,
-                   size_t dictionary_size);
+                   size_t dictionary_size,
+                   bool copy = true);
   ~HashedDictionary();
 
   // Init() must be called before using the HashedDictionary as an argument
diff --git a/src/vcdiffengine.cc b/src/vcdiffengine.cc
index 0060867..5a5a052 100644
--- a/src/vcdiffengine.cc
+++ b/src/vcdiffengine.cc
@@ -23,20 +23,21 @@
 
 namespace open_vcdiff {
 
-VCDiffEngine::VCDiffEngine(const char* dictionary, size_t dictionary_size)
+VCDiffEngine::VCDiffEngine(const char* dictionary, size_t dictionary_size, bool copy)
     // If dictionary_size == 0, then dictionary could be NULL.  Guard against
     // using a NULL value.
-    : dictionary_((dictionary_size > 0) ? new char[dictionary_size] : ""),
+    : dictionary_((dictionary_size > 0) ? (copy ? new char[dictionary_size] : dictionary) : ""),
+      owns_dictionary_(copy),
       dictionary_size_(dictionary_size),
       hashed_dictionary_(NULL) {
-  if (dictionary_size > 0) {
+  if (dictionary_size > 0 && copy) {
     memcpy(const_cast<char*>(dictionary_), dictionary, dictionary_size);
   }
 }
 
 VCDiffEngine::~VCDiffEngine() {
   delete hashed_dictionary_;
-  if (dictionary_size_ > 0) {
+  if (dictionary_size_ > 0 && owns_dictionary_) {
     delete[] dictionary_;
   }
 }
diff --git a/src/vcdiffengine.h b/src/vcdiffengine.h
index 02ede2a..78ed326 100644
--- a/src/vcdiffengine.h
+++ b/src/vcdiffengine.h
@@ -37,7 +37,7 @@ class VCDiffEngine {
   // aligned on block boundaries in the dictionary text.
   static const size_t kMinimumMatchSize = 32;
 
-  VCDiffEngine(const char* dictionary, size_t dictionary_size);
+  VCDiffEngine(const char* dictionary, size_t dictionary_size, bool copy = true);
 
   ~VCDiffEngine();
 
@@ -107,6 +107,8 @@ class VCDiffEngine {
 
   const char* dictionary_;  // A copy of the dictionary contents
 
+  bool owns_dictionary_;
+
   const size_t dictionary_size_;
 
   // A hash that contains one element for every kBlockSize bytes of dictionary_.
diff --git a/src/vcencoder.cc b/src/vcencoder.cc
index 7fe5a6a..8ad7201 100644
--- a/src/vcencoder.cc
+++ b/src/vcencoder.cc
@@ -57,8 +57,9 @@ CodeTableWriterInterface* create_writer(
 }  // namespace
 
 HashedDictionary::HashedDictionary(const char* dictionary_contents,
-                                   size_t dictionary_size)
-    : engine_(new VCDiffEngine(dictionary_contents, dictionary_size)) { }
+                                   size_t dictionary_size,
+                                   bool copy)
+    : engine_(new VCDiffEngine(dictionary_contents, dictionary_size, copy)) { }
 
 HashedDictionary::~HashedDictionary() { delete engine_; }