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, 52 insertions, 55 deletions

diff --git a/fxjs/cfxjse_resolveprocessor.cpp b/fxjs/cfxjse_resolveprocessor.cpp
index 46163b55fc..2ca0838a7f 100644
--- a/fxjs/cfxjse_resolveprocessor.cpp
+++ b/fxjs/cfxjse_resolveprocessor.cpp
@@ -499,69 +499,66 @@ int32_t CFXJSE_ResolveProcessor::GetFilter(const WideStringView& wsExpression,
 
   WideString& wsName = rnd.m_wsName;
   WideString& wsCondition = rnd.m_wsCondition;
+  wchar_t* pNameBuf = wsName.GetBuffer(iLength - nStart);
+  wchar_t* pConditionBuf = wsCondition.GetBuffer(iLength - nStart);
   int32_t nNameCount = 0;
   int32_t nConditionCount = 0;
-  {
-    // Span's lifetime must end before ReleaseBuffer() below.
-    pdfium::span<wchar_t> pNameBuf = wsName.GetBuffer(iLength - nStart);
-    pdfium::span<wchar_t> pConditionBuf =
-        wsCondition.GetBuffer(iLength - nStart);
-    std::vector<int32_t> stack;
-    int32_t nType = -1;
-    const wchar_t* pSrc = wsExpression.unterminated_c_str();
-    wchar_t wPrev = 0;
-    wchar_t wCur;
-    bool bIsCondition = false;
-    while (nStart < iLength) {
-      wCur = pSrc[nStart++];
-      if (wCur == '.') {
-        if (wPrev == '\\') {
-          pNameBuf[nNameCount - 1] = wPrev = '.';
-          continue;
-        }
-        if (nNameCount == 0) {
-          rnd.m_dwStyles |= XFA_RESOLVENODE_AnyChild;
-          continue;
-        }
-
-        wchar_t wLookahead = nStart < iLength ? pSrc[nStart] : 0;
-        if (wLookahead != '[' && wLookahead != '(' && nType < 0)
-          break;
-      }
-      if (wCur == '[' || wCur == '(') {
-        bIsCondition = true;
-      } else if (wCur == '.' && nStart < iLength &&
-                 (pSrc[nStart] == '[' || pSrc[nStart] == '(')) {
-        bIsCondition = true;
+  std::vector<int32_t> stack;
+  int32_t nType = -1;
+  const wchar_t* pSrc = wsExpression.unterminated_c_str();
+  wchar_t wPrev = 0;
+  wchar_t wCur;
+  bool bIsCondition = false;
+  while (nStart < iLength) {
+    wCur = pSrc[nStart++];
+    if (wCur == '.') {
+      if (wPrev == '\\') {
+        pNameBuf[nNameCount - 1] = wPrev = '.';
+        continue;
       }
-      if (bIsCondition)
-        pConditionBuf[nConditionCount++] = wCur;
-      else
-        pNameBuf[nNameCount++] = wCur;
-
-      if ((nType == 0 && wCur == ']') || (nType == 1 && wCur == ')') ||
-          (nType == 2 && wCur == '"')) {
-        nType = stack.empty() ? -1 : stack.back();
-        if (!stack.empty())
-          stack.pop_back();
-      } else if (wCur == '[') {
-        stack.push_back(nType);
-        nType = 0;
-      } else if (wCur == '(') {
-        stack.push_back(nType);
-        nType = 1;
-      } else if (wCur == '"') {
-        stack.push_back(nType);
-        nType = 2;
+      if (nNameCount == 0) {
+        rnd.m_dwStyles |= XFA_RESOLVENODE_AnyChild;
+        continue;
       }
-      wPrev = wCur;
+
+      wchar_t wLookahead = nStart < iLength ? pSrc[nStart] : 0;
+      if (wLookahead != '[' && wLookahead != '(' && nType < 0)
+        break;
+    }
+    if (wCur == '[' || wCur == '(') {
+      bIsCondition = true;
+    } else if (wCur == '.' && nStart < iLength &&
+               (pSrc[nStart] == '[' || pSrc[nStart] == '(')) {
+      bIsCondition = true;
+    }
+    if (bIsCondition)
+      pConditionBuf[nConditionCount++] = wCur;
+    else
+      pNameBuf[nNameCount++] = wCur;
+
+    if ((nType == 0 && wCur == ']') || (nType == 1 && wCur == ')') ||
+        (nType == 2 && wCur == '"')) {
+      nType = stack.empty() ? -1 : stack.back();
+      if (!stack.empty())
+        stack.pop_back();
+    } else if (wCur == '[') {
+      stack.push_back(nType);
+      nType = 0;
+    } else if (wCur == '(') {
+      stack.push_back(nType);
+      nType = 1;
+    } else if (wCur == '"') {
+      stack.push_back(nType);
+      nType = 2;
     }
-    if (!stack.empty())
-      return -1;
+    wPrev = wCur;
   }
+  if (!stack.empty())
+    return -1;
+
   wsName.ReleaseBuffer(nNameCount);
-  wsCondition.ReleaseBuffer(nConditionCount);
   wsName.Trim();
+  wsCondition.ReleaseBuffer(nConditionCount);
   wsCondition.Trim();
   rnd.m_uHashName =
       static_cast<XFA_HashCode>(FX_HashCode_GetW(wsName.AsStringView(), false));