Re-land "Return pdfium::span<char> from ByteString::GetBuffer().""

This reverts commit 3d523e3cf89440e2ffc6571b1c687ad5e3f0318f.
Fixes bounding errors now caught by tests.

Change-Id: I4d0f1791bdcc45a10615a62abf7a4d20e7e538f2
Reviewed-on: https://pdfium-review.googlesource.com/30799
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/core/fxcrt/bytestring.h b/core/fxcrt/bytestring.h
index ccb539b2ef..247238573d 100644
--- a/core/fxcrt/bytestring.h
+++ b/core/fxcrt/bytestring.h
@@ -17,6 +17,7 @@
 #include "core/fxcrt/string_data_template.h"
 #include "core/fxcrt/string_view_template.h"
 #include "third_party/base/optional.h"
+#include "third_party/base/span.h"
 
 namespace fxcrt {
 
@@ -153,7 +154,10 @@ class ByteString {
   size_t Delete(size_t index, size_t count = 1);
 
   void Reserve(size_t len);
-  char* GetBuffer(size_t len);
+
+  // Note: any modification of the string (including ReleaseBuffer()) may
+  // invalidate the span, which must not outlive its buffer.
+  pdfium::span<char> GetBuffer(size_t len);
   void ReleaseBuffer(size_t len);
 
   ByteString Mid(size_t first, size_t count) const;