Revert "Return pdfium::span<wchar_t> from WideString::GetBuffer()."

This reverts commit 154e18f9a862975abecebe77b8f5fb418418d14c.

Reason for revert: Generate CL to merge to beta branch

Original change's description:
> Return pdfium::span<wchar_t> from WideString::GetBuffer().
> 
> Adds bounds checking "for free", but beware of span outliving
> a ReleaseBuffer() call.  Scoping as such avoids the possibility
> of using an invalid span (and it is flagged as a lifetime issue).
> 
> Change-Id: Ica63f4b1429823d0254ec6951aeaeb08160cb93c
> Reviewed-on: https://pdfium-review.googlesource.com/30310
> Reviewed-by: dsinclair <dsinclair@chromium.org>
> Commit-Queue: Tom Sepez <tsepez@chromium.org>

TBR=tsepez@chromium.org,dsinclair@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: Ie1ec9434215584a024538ca8edeb59dea555af48
Reviewed-on: https://pdfium-review.googlesource.com/30830
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

1 files changed, 26 insertions, 29 deletions

diff --git a/core/fxcrt/cfx_blockbuffer.cpp b/core/fxcrt/cfx_blockbuffer.cpp
index 6a7d98aa18..13134f0e7b 100644
--- a/core/fxcrt/cfx_blockbuffer.cpp
+++ b/core/fxcrt/cfx_blockbuffer.cpp
@@ -77,39 +77,36 @@ WideString CFX_BlockBuffer::GetTextData(size_t start, size_t length) const {
   size_t maybeDataLength = m_BufferSize - 1 - m_StartPosition;
   if (start > maybeDataLength)
     return WideString();
-
   length = std::min(length, maybeDataLength);
-  if (!length)
-    return WideString();
 
   WideString wsTextData;
-  {
-    // Span's lifetime must end before ReleaseBuffer() below.
-    pdfium::span<wchar_t> pBuf = wsTextData.GetBuffer(length);
-    size_t startBlock = 0;
-    size_t startInner = 0;
-    std::tie(startBlock, startInner) = TextDataIndex2BufIndex(start);
-
-    size_t endBlock = 0;
-    size_t endInner = 0;
-    std::tie(endBlock, endInner) = TextDataIndex2BufIndex(start + length);
-
-    size_t pointer = 0;
-    for (size_t i = startBlock; i <= endBlock; ++i) {
-      size_t bufferPointer = 0;
-      size_t copyLength = kAllocStep;
-      if (i == startBlock) {
-        copyLength -= startInner;
-        bufferPointer = startInner;
-      }
-      if (i == endBlock)
-        copyLength -= ((kAllocStep - 1) - endInner);
-
-      wchar_t* pBlockBuf = m_BlockArray[i].get();
-      memcpy(&pBuf[pointer], pBlockBuf + bufferPointer,
-             copyLength * sizeof(wchar_t));
-      pointer += copyLength;
+  wchar_t* pBuf = wsTextData.GetBuffer(length);
+  if (!pBuf)
+    return WideString();
+
+  size_t startBlock = 0;
+  size_t startInner = 0;
+  std::tie(startBlock, startInner) = TextDataIndex2BufIndex(start);
+
+  size_t endBlock = 0;
+  size_t endInner = 0;
+  std::tie(endBlock, endInner) = TextDataIndex2BufIndex(start + length);
+
+  size_t pointer = 0;
+  for (size_t i = startBlock; i <= endBlock; ++i) {
+    size_t bufferPointer = 0;
+    size_t copyLength = kAllocStep;
+    if (i == startBlock) {
+      copyLength -= startInner;
+      bufferPointer = startInner;
     }
+    if (i == endBlock)
+      copyLength -= ((kAllocStep - 1) - endInner);
+
+    wchar_t* pBlockBuf = m_BlockArray[i].get();
+    memcpy(pBuf + pointer, pBlockBuf + bufferPointer,
+           copyLength * sizeof(wchar_t));
+    pointer += copyLength;
   }
   wsTextData.ReleaseBuffer(length);
   return wsTextData;