PDF: Yet another stab at getting WriteInto() buffer sizes correct.

pdf/pdfium/pdfium_api_string_buffer_adapter.h

Index: pdf/pdfium/pdfium_api_string_buffer_adapter.h
diff --git a/pdf/pdfium/pdfium_api_string_buffer_adapter.h b/pdf/pdfium/pdfium_api_string_buffer_adapter.h
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+// Copyright 2015 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.
+
+#ifndef PDF_PDFIUM_PDFIUM_API_STRING_BUFFER_ADAPTER_H_
+#define PDF_PDFIUM_PDFIUM_API_STRING_BUFFER_ADAPTER_H_
+
+#include "base/basictypes.h"
+
+namespace chrome_pdf {
+
+// Helper to deal with the fact that many PDFium APIs write the null-terminator
+// into string buffers that are passed to them, but the PDF plugin likes to pass
+// in std::strings / base::string16s, where one should not count on the internal
+// string buffers to be null-terminated.
+
+template <class StringType>
+class PDFiumAPIStringBufferAdapter {
+ public:
+  // |str| is the string to write into.
+  // |expected_size| is the number of characters the PDFium API will write,
+  // including the null-terminator. It should be at least 1.
+  // |check_expected_size| whether to check the actual number of characters
+  // written into |str| against |expected_size| when calling Close().
+  PDFiumAPIStringBufferAdapter(StringType* str,
+                               size_t expected_size,
+                               bool check_expected_size);
+  ~PDFiumAPIStringBufferAdapter();
+
+  // Returns a pointer to |str_|'s buffer. The buffer's size is large enough to
+  // hold |expected_size_| + 1 characters, so the PDFium API that uses the
+  // pointer has space to write a null-terminator.
+  void* GetData();
+
+  // Resizes |str_| to |actual_size| - 1 characters, thereby removing the extra
+  // null-terminator. This must be called prior to the adapter's destruction.
+  // The pointer returned by GetData() should be considered invalid.
+  void Close(int actual_size);
+  void Close(size_t actual_size);
+
+ private:
+  StringType* const str_;
+  void* const data_;
+  const size_t expected_size_;
+  const bool check_expected_size_;
+  bool is_closed_;
+
+  DISALLOW_COPY_AND_ASSIGN(PDFiumAPIStringBufferAdapter);
+};
+
+}  // namespace chrome_pdf
+
+#endif  // PDF_PDFIUM_PDFIUM_API_STRING_BUFFER_ADAPTER_H_