Use unsigned page indexes in CPDF_HintTables.

fpdfsdk/fpdf_dataavail.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "public/fpdf_dataavail.h"
 
 #include "core/fpdfapi/fpdf_parser/include/cpdf_data_avail.h"
 #include "core/fpdfapi/fpdf_parser/include/cpdf_document.h"
@@ skipping 144 matching lines @@
 DLLEXPORT int STDCALL FPDFAvail_GetFirstPageNum(FPDF_DOCUMENT doc) {
   CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(doc);
   return pDoc ? pDoc->GetParser()->GetFirstPageNo() : 0;
 }
 
 DLLEXPORT int STDCALL FPDFAvail_IsPageAvail(FPDF_AVAIL avail,
                                             int page_index,
                                             FX_DOWNLOADHINTS* hints) {
   if (!avail || !hints)
     return PDF_DATA_ERROR;
+  if (page_index < 0)
+    return PDF_DATA_NOTAVAIL;
   CFPDF_DownloadHintsWrap hints_wrap(hints);
   return CFPDFDataAvailFromFPDFAvail(avail)->m_pDataAvail->IsPageAvail(
       page_index, &hints_wrap);
 }
 
 DLLEXPORT int STDCALL FPDFAvail_IsFormAvail(FPDF_AVAIL avail,
                                             FX_DOWNLOADHINTS* hints) {
   if (!avail || !hints)
     return PDF_FORM_ERROR;
   CFPDF_DownloadHintsWrap hints_wrap(hints);
   return CFPDFDataAvailFromFPDFAvail(avail)->m_pDataAvail->IsFormAvail(
       &hints_wrap);
 }
 
 DLLEXPORT int STDCALL FPDFAvail_IsLinearized(FPDF_AVAIL avail) {
   if (!avail)
     return PDF_LINEARIZATION_UNKNOWN;
   return CFPDFDataAvailFromFPDFAvail(avail)->m_pDataAvail->IsLinearizedPDF();
 }