Catch internal BadSizedFile exception in BuildFileCompound.

And try with multi parts compound only if file is not found or file
is too small.

We can now fix the tests as we have a clear (new) message thrown.

src/fileimpl.cpp

@@ -164,15 +164,25 @@ class BadSizedFile: public std::exception {};
   //////////////////////////////////////////////////////////////////////
   // FileImpl
   //
-  std::shared_ptr<FileImpl> FileImpl::openSinglePieceOrSplitZimFile(const std::string& filename) {
+  std::shared_ptr<FileImpl> FileImpl::openSinglePieceOrSplitZimFile(std::string fname) {
+    std::shared_ptr<FileCompound> fileCompound;
+    if (fname.size() > 6 && fname.substr(fname.size()-6) == ".zimaa") {
+      fname.resize(fname.size()-2);
+    } else {
+      try {
+        fileCompound = std::make_shared<FileCompound>(fname);
+      } catch(...) { }
+    }
+
+    if ( !fileCompound ) {
+      fileCompound = std::make_shared<FileCompound>(fname, FileCompound::MultiPartToken::Multi);
+    }
+
     try {
-      return std::shared_ptr<FileImpl>(
-        new FileImpl(std::make_shared<FileCompound>(filename))
-      );
-    } catch (...) {
-      return std::shared_ptr<FileImpl>(
-        new FileImpl(std::make_shared<FileCompound>(filename, FileCompound::MultiPartToken::Multi))
-      );
+      return std::shared_ptr<FileImpl>(new FileImpl(fileCompound));
+    } catch (BadSizedFile& e) {
+      // BadSizedFile is internal error.
+      throw ZimFileFormatError("Zim file(s) is of bad size or corrupted.");
     }
   }
 

src/fileimpl.h

@@ -97,7 +97,7 @@ namespace zim
       using FindxResult = std::pair<bool, entry_index_t>;
       using FindxTitleResult = std::pair<bool, title_index_t>;
 
-      static std::shared_ptr<FileImpl> openSinglePieceOrSplitZimFile(const std::string& fname);
+      static std::shared_ptr<FileImpl> openSinglePieceOrSplitZimFile(std::string fname);
 #ifndef _WIN32
       explicit FileImpl(int fd);
       explicit FileImpl(FdInput fd);

test/archive.cpp

@@ -264,6 +264,31 @@ TEST(ZimArchive, openRealZimArchive)
   }
 }
 
+TEST(ZimArchive, openSplitZimArchive)
+{
+  const char* fname = "wikibooks_be_all_nopic_2017-02_splitted.zim";
+
+  for (auto& testfile: getDataFilePath(fname)) {
+    const TestContext ctx{ {"path", testfile.path+"aa" } };
+    std::unique_ptr<zim::Archive> archive;
+    EXPECT_NO_THROW( archive.reset(new zim::Archive(testfile.path+"aa")) ) << ctx;
+    if ( archive ) {
+      EXPECT_TRUE( archive->check() ) << ctx;
+    }
+  }
+}
+
+TEST(ZimArchive, openDontFallbackOnNonSplitZimArchive)
+{
+  const char* fname = "wikibooks_be_all_nopic_2017-02.zim";
+
+  for (auto& testfile: getDataFilePath(fname)) {
+    const TestContext ctx{ {"path", testfile.path+"aa" } };
+    std::unique_ptr<zim::Archive> archive;
+    EXPECT_THROW( archive.reset(new zim::Archive(testfile.path+"aa")), std::runtime_error) << ctx;
+  }
+}
+
 TEST(ZimArchive, randomEntry)
 {
   const char* const zimfiles[] = {
@@ -404,7 +429,7 @@ TEST(ZimArchive, validate)
 
   TEST_BROKEN_ZIM_NAME(
     "invalid.smaller_than_header.zim",
-    "zim-file is too small to contain a header\n"
+    "Zim file(s) is of bad size or corrupted.\n"
   );
 
   TEST_BROKEN_ZIM_NAME(
@@ -434,7 +459,7 @@ TEST(ZimArchive, validate)
 
   TEST_BROKEN_ZIM_NAME(
     "invalid.invalid_checksumpos.zim",
-    "Checksum position is not valid\n"
+    "Zim file(s) is of bad size or corrupted.\n"
   );
 
   TEST_BROKEN_ZIM_NAME(