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, 9 insertions, 5 deletions

diff --git a/core/fxge/cfx_folderfontinfo.cpp b/core/fxge/cfx_folderfontinfo.cpp
index 532824d248..b39c57637f 100644
--- a/core/fxge/cfx_folderfontinfo.cpp
+++ b/core/fxge/cfx_folderfontinfo.cpp
@@ -44,11 +44,15 @@ const struct {
 };
 
 ByteString FPDF_ReadStringFromFile(FILE* pFile, uint32_t size) {
-  ByteString buffer;
-  if (!fread(buffer.GetBuffer(size), size, 1, pFile))
-    return ByteString();
-  buffer.ReleaseBuffer(size);
-  return buffer;
+  ByteString result;
+  {
+    // Span's lifetime must end before ReleaseBuffer() below.
+    pdfium::span<char> buffer = result.GetBuffer(size);
+    if (!fread(buffer.data(), size, 1, pFile))
+      return ByteString();
+  }
+  result.ReleaseBuffer(size);
+  return result;
 }
 
 ByteString FPDF_LoadTableFromTT(FILE* pFile,