[IO] Add readRasters() for reading all rasters.

FileIO/AsciiRasterInterface.cpp

@@ -14,6 +14,7 @@
 #include "AsciiRasterInterface.h"
 
 #include <logog/include/logog.hpp>
+#include <boost/optional.hpp>
 
 #include "BaseLib/FileTools.h"
 #include "BaseLib/StringTools.h"
@@ -226,4 +227,16 @@ bool allRastersExist(std::vector<std::string> const& raster_paths)
 	}
 	return true;
 }
+
+boost::optional<std::vector<GeoLib::Raster const*>> readRasters(
+    std::vector<std::string> const& raster_paths)
+{
+	if (!allRastersExist(raster_paths)) return boost::none;
+
+	std::vector<GeoLib::Raster const*> rasters;
+	rasters.reserve(raster_paths.size());
+	for (auto const& path : raster_paths)
+		rasters.push_back(FileIO::AsciiRasterInterface::readRaster(path));
+    return boost::make_optional(rasters);
+}
 }

FileIO/AsciiRasterInterface.h

@@ -15,6 +15,9 @@
 #define ASCIIRASTERINTERFACE_H_
 
 #include <fstream>
+#include <vector>
+#include <string>
+#include <boost/optional.hpp>
 
 #include "GeoLib/Raster.h"
 
@@ -49,6 +52,11 @@ private:
                                  double &min, double &max);
 };
 
+/// Reads a vector of rasters given by file names. On error nothing is returned,
+/// otherwise the returned vector contains pointers to the read rasters.
+boost::optional<std::vector<GeoLib::Raster const*>> readRasters(
+    std::vector<std::string> const& raster_paths);
+
 /// Checks if all raster files actually exist
 bool allRastersExist(std::vector<std::string> const& raster_paths);