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>

1 files changed, 23 insertions, 21 deletions

diff --git a/xfa/fxfa/parser/cxfa_localevalue.cpp b/xfa/fxfa/parser/cxfa_localevalue.cpp
index 8ef67e5183..b129960f7d 100644
--- a/xfa/fxfa/parser/cxfa_localevalue.cpp
+++ b/xfa/fxfa/parser/cxfa_localevalue.cpp
@@ -682,32 +682,34 @@ void CXFA_LocaleValue::GetNumericFormat(WideString& wsFormat,
                                         int32_t nDecLen) {
   ASSERT(wsFormat.IsEmpty());
   ASSERT(nIntLen >= -1 && nDecLen >= -1);
-
   int32_t nTotalLen = (nIntLen >= 0 ? nIntLen : 2) + 1 +
                       (nDecLen >= 0 ? nDecLen : 2) + (nDecLen == 0 ? 0 : 1);
-  wchar_t* lpBuf = wsFormat.GetBuffer(nTotalLen);
-  int32_t nPos = 0;
-  lpBuf[nPos++] = L's';
-
-  if (nIntLen == -1) {
-    lpBuf[nPos++] = L'z';
-    lpBuf[nPos++] = L'*';
-  } else {
-    while (nIntLen) {
+  {
+    // Span's lifetime must end before ReleaseBuffer() below.
+    pdfium::span<wchar_t> lpBuf = wsFormat.GetBuffer(nTotalLen);
+    int32_t nPos = 0;
+    lpBuf[nPos++] = L's';
+
+    if (nIntLen == -1) {
       lpBuf[nPos++] = L'z';
-      nIntLen--;
+      lpBuf[nPos++] = L'*';
+    } else {
+      while (nIntLen) {
+        lpBuf[nPos++] = L'z';
+        nIntLen--;
+      }
     }
-  }
-  if (nDecLen != 0) {
-    lpBuf[nPos++] = L'.';
-  }
-  if (nDecLen == -1) {
-    lpBuf[nPos++] = L'z';
-    lpBuf[nPos++] = L'*';
-  } else {
-    while (nDecLen) {
+    if (nDecLen != 0) {
+      lpBuf[nPos++] = L'.';
+    }
+    if (nDecLen == -1) {
       lpBuf[nPos++] = L'z';
-      nDecLen--;
+      lpBuf[nPos++] = L'*';
+    } else {
+      while (nDecLen) {
+        lpBuf[nPos++] = L'z';
+        nDecLen--;
+      }
     }
   }
   wsFormat.ReleaseBuffer(nTotalLen);