Refactor modification of Contents in CPDF_PageContentGenerator.

This is a pure refactor, there should be no change in behavior. It
prepares for the next CL, which will allow modification of content
streams.

Bug: pdfium:1051
Change-Id: I01ca3e897efe423e89df75e1f31cd67539cc3d08
Reviewed-on: https://pdfium-review.googlesource.com/34470
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>

1 files changed, 87 insertions, 0 deletions

diff --git a/core/fpdfapi/edit/cpdf_pagecontentmanager.cpp b/core/fpdfapi/edit/cpdf_pagecontentmanager.cpp
new file mode 100644
index 0000000000..e9ade27bf8
--- /dev/null
+++ b/core/fpdfapi/edit/cpdf_pagecontentmanager.cpp
@@ -0,0 +1,87 @@
+// Copyright 2018 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/fpdfapi/edit/cpdf_pagecontentmanager.h"
+
+#include "core/fpdfapi/parser/cpdf_array.h"
+#include "core/fpdfapi/parser/cpdf_dictionary.h"
+#include "core/fpdfapi/parser/cpdf_document.h"
+#include "core/fpdfapi/parser/cpdf_reference.h"
+#include "core/fpdfapi/parser/cpdf_stream.h"
+
+CPDF_PageContentManager::CPDF_PageContentManager(
+    CPDF_PageObjectHolder* obj_holder)
+    : obj_holder_(obj_holder), doc_(obj_holder_->GetDocument()) {
+  CPDF_Dictionary* page_dict = obj_holder_->GetDict();
+  CPDF_Object* contents_obj = page_dict->GetObjectFor("Contents");
+  CPDF_Array* contents_array = ToArray(contents_obj);
+  if (contents_array) {
+    contents_array_ = contents_array;
+    return;
+  }
+
+  CPDF_Reference* contents_reference = ToReference(contents_obj);
+  if (contents_reference) {
+    CPDF_Object* indirect_obj = contents_reference->GetDirect();
+    if (!indirect_obj)
+      return;
+
+    contents_array = indirect_obj->AsArray();
+    if (contents_array)
+      contents_array_ = contents_array;
+    else if (indirect_obj->IsStream())
+      contents_stream_ = indirect_obj->AsStream();
+  }
+}
+
+CPDF_PageContentManager::~CPDF_PageContentManager() = default;
+
+CPDF_Stream* CPDF_PageContentManager::GetStreamByIndex(size_t stream_index) {
+  if (contents_stream_)
+    return stream_index == 0 ? contents_stream_.Get() : nullptr;
+
+  if (contents_array_) {
+    CPDF_Reference* stream_reference =
+        ToReference(contents_array_->GetObjectAt(stream_index));
+    if (!stream_reference)
+      return nullptr;
+
+    return stream_reference->GetDirect()->AsStream();
+  }
+
+  return nullptr;
+}
+
+size_t CPDF_PageContentManager::AddStream(std::ostringstream* buf) {
+  CPDF_Stream* new_stream = doc_->NewIndirect<CPDF_Stream>();
+  new_stream->SetData(buf);
+
+  // If there is one Content stream (not in an array), now there will be two, so
+  // create an array with the old and the new one. The new one's index is 1.
+  if (contents_stream_) {
+    CPDF_Array* new_contents_array = doc_->NewIndirect<CPDF_Array>();
+    new_contents_array->Add(contents_stream_->MakeReference(doc_.Get()));
+    new_contents_array->Add(new_stream->MakeReference(doc_.Get()));
+
+    CPDF_Dictionary* page_dict = obj_holder_->GetDict();
+    page_dict->SetFor("Contents",
+                      new_contents_array->MakeReference(doc_.Get()));
+    contents_array_ = new_contents_array;
+    contents_stream_ = nullptr;
+    return 1;
+  }
+
+  // If there is an array, just add the new stream to it, at the last position.
+  if (contents_array_) {
+    contents_array_->Add(new_stream->MakeReference(doc_.Get()));
+    return contents_array_->GetCount() - 1;
+  }
+
+  // There were no Contents, so add the new stream as the single Content stream.
+  // Its index is 0.
+  CPDF_Dictionary* page_dict = obj_holder_->GetDict();
+  page_dict->SetFor("Contents", new_stream->MakeReference(doc_.Get()));
+  contents_stream_ = new_stream;
+  return 0;
+}