Add filesystem helper: read_file_by_lines()

Author: franzpoeschel

include/openPMD/auxiliary/Filesystem.hpp

@@ -100,5 +100,20 @@ std::string
 collective_file_read( std::string const & path, MPI_Comm );
 
 #endif
-} // namespace auxiliary
-} // namespace openPMD
+
+struct no_such_file_error
+{
+};
+
+/**
+ * @brief Read a file line by line.
+ *
+ * @param path Path to the file.
+ * @return Lines of the read file, excluding newline characters.
+ *
+ * @throws no_such_file_error
+ */
+std::vector< std::string >
+read_file_by_lines( std::string const & path );
+} // auxiliary
+} // openPMD

src/auxiliary/Filesystem.cpp

@@ -35,6 +35,8 @@
 #include <iostream>
 #include <stdexcept>
 #include <system_error>
+#include <fstream>
+#include <sstream>
 
 
 namespace openPMD
@@ -258,5 +260,22 @@ collective_file_read( std::string const & path, MPI_Comm comm )
 
 #endif
 
-} // namespace auxiliary
-} // namespace openPMD
+std::vector< std::string >
+read_file_by_lines( std::string const & path )
+{
+    std::vector< std::string > res;
+    std::ifstream file( path, std::ios_base::in );
+    if ( file.fail( ) )
+    {
+        throw no_such_file_error( );
+    }
+    std::string line;
+    while( std::getline( file, line ) )
+    {
+        res.push_back( std::move( line ) );
+        line = std::string( );
+    }
+    return res;
+}
+} // auxiliary
+} // openPMD