Code Modified to remove use of C++11 features.

Tested compilation with VS2012, clang++ 3.4 and g++.

test.cc

@@ -3,12 +3,9 @@
 #include <cstdio>
 #include <cstdlib>
 #include <cassert>
-#include <cstddef>
 #include <iostream>
 #include <sstream>
 #include <fstream>
-#include <functional>
-#include <memory>
 
 static void PrintInfo(const std::vector<tinyobj::shape_t>& shapes)
 {
@@ -45,8 +42,8 @@ static void PrintInfo(const std::vector<tinyobj::shape_t>& shapes)
     printf("  material.map_Kd = %s\n", shapes[i].material.diffuse_texname.c_str());
     printf("  material.map_Ks = %s\n", shapes[i].material.specular_texname.c_str());
     printf("  material.map_Ns = %s\n", shapes[i].material.normal_texname.c_str());
-    auto it = shapes[i].material.unknown_parameter.begin();
-    auto itEnd = shapes[i].material.unknown_parameter.end();
+    std::map<std::string, std::string>::const_iterator it(shapes[i].material.unknown_parameter.begin());
+    std::map<std::string, std::string>::const_iterator itEnd(shapes[i].material.unknown_parameter.end());
     for (; it != itEnd; it++) {
       printf("  material.%s = %s\n", it->first.c_str(), it->second.c_str());
     }
@@ -113,48 +110,54 @@ TestStreamLoadObj()
     "usemtl white\n"
     "f 2 6 7 3\n"
     "# 6 elements";
-   
-  auto getMatFileIStreamFunc = 
-    [](const std::string& matId)
-    {           
-      if (matId == "cube.mtl") {
-      
-        std::unique_ptr<std::stringstream> matStream( 
-          new std::stringstream(
-            "newmtl white\n"
-            "Ka 0 0 0\n"
-            "Kd 1 1 1\n"
-            "Ks 0 0 0\n"
-            "\n"
-            "newmtl red\n"
-            "Ka 0 0 0\n"
-            "Kd 1 0 0\n"
-            "Ks 0 0 0\n"
-            "\n"
-            "newmtl green\n"
-            "Ka 0 0 0\n"
-            "Kd 0 1 0\n"
-            "Ks 0 0 0\n"
-            "\n"
-            "newmtl blue\n"
-            "Ka 0 0 0\n"
-            "Kd 0 0 1\n"
-            "Ks 0 0 0\n"
-            "\n"
-            "newmtl light\n"
-            "Ka 20 20 20\n"
-            "Kd 1 1 1\n"
-            "Ks 0 0 0"));
 
-        return matStream;
-      }
+std::string matStream( 
+    "newmtl white\n"
+    "Ka 0 0 0\n"
+    "Kd 1 1 1\n"
+    "Ks 0 0 0\n"
+    "\n"
+    "newmtl red\n"
+    "Ka 0 0 0\n"
+    "Kd 1 0 0\n"
+    "Ks 0 0 0\n"
+    "\n"
+    "newmtl green\n"
+    "Ka 0 0 0\n"
+    "Kd 0 1 0\n"
+    "Ks 0 0 0\n"
+    "\n"
+    "newmtl blue\n"
+    "Ka 0 0 0\n"
+    "Kd 0 0 1\n"
+    "Ks 0 0 0\n"
+    "\n"
+    "newmtl light\n"
+    "Ka 20 20 20\n"
+    "Kd 1 1 1\n"
+    "Ks 0 0 0");
 
-      std::unique_ptr<std::stringstream> emptyUP( nullptr );
-      return emptyUP;
-    };
-    
+    using namespace tinyobj;
+    class MaterialStringStreamReader:
+        public MaterialReader
+    {
+        public:
+            MaterialStringStreamReader(const std::string& matSStream): m_matSStream(matSStream) {}
+            virtual ~MaterialStringStreamReader() {}
+            virtual std::string operator() (
+              const std::string& matId,
+              std::map<std::string, material_t>& matMap)
+            {
+                return LoadMtl(matMap, m_matSStream);
+            }
+
+        private:
+            std::stringstream m_matSStream;
+    };  
+
+  MaterialStringStreamReader matSSReader(matStream);
   std::vector<tinyobj::shape_t> shapes;
-  std::string err = tinyobj::LoadObj(shapes, objStream, getMatFileIStreamFunc);    
+  std::string err = tinyobj::LoadObj(shapes, objStream, matSSReader);    
   
   if (!err.empty()) {
     std::cerr << err << std::endl;

tiny_obj_loader.cc

@@ -478,6 +478,22 @@ std::string LoadMtl (
   return err.str();
 }
 
+std::string MaterialFileReader::operator() (
+    const std::string& matId,
+    std::map<std::string, material_t>& matMap)
+{
+  std::string filepath;
+
+  if (!m_mtlBasePath.empty()) {
+    filepath = std::string(m_mtlBasePath) + matId;
+  } else {
+    filepath = matId;
+  }
+
+  std::ifstream matIStream(filepath.c_str());
+  return LoadMtl(matMap, matIStream);
+}
+
 std::string
 LoadObj(
   std::vector<shape_t>& shapes,
@@ -495,28 +511,19 @@ LoadObj(
     return err.str();
   }
 
-  auto getMatFileIStreamFunc = 
-    [&](const std::string& matId)
-    {
-      std::string filepath;
-
-      if (mtl_basepath) {
-        filepath = std::string(mtl_basepath) + matId;
-      } else {
-        filepath = matId;
-      }
-
-      std::unique_ptr<std::ifstream> ifs( new std::ifstream(filepath.c_str()) );
-      return ifs;      
-    };
+  std::string basePath;
+  if (mtl_basepath) {
+    basePath = mtl_basepath;
+  }
+  MaterialFileReader matFileReader( basePath );
   
-  return LoadObj(shapes, ifs, getMatFileIStreamFunc);
+  return LoadObj(shapes, ifs, matFileReader);
 }
 
 std::string LoadObj(
   std::vector<shape_t>& shapes,
   std::istream& inStream,
-  GetMtlIStreamFn getMatFn)
+  MaterialReader& readMatFn)
 {
   std::stringstream err;
 
@@ -633,19 +640,11 @@ std::string LoadObj(
       char namebuf[4096];
       token += 7;
       sscanf(token, "%s", namebuf);
-
-      if (!getMatFn) {
-          err << "Could not read material, no callable function target.";
-          return err.str();
-      }
         
-      std::unique_ptr<std::istream> matIStream = getMatFn(namebuf);
-      if (matIStream) {
-        std::string err_mtl = LoadMtl(material_map, *matIStream);
-        if (!err_mtl.empty()) {
-          faceGroup.clear();  // for safety
-          return err_mtl;
-        }
+      std::string err_mtl = readMatFn(namebuf, material_map);
+      if (!err_mtl.empty()) {
+        faceGroup.clear();  // for safety
+        return err_mtl;
       }
       
       continue;

tiny_obj_loader.h

@@ -9,8 +9,6 @@
 #include <string>
 #include <vector>
 #include <map>
-#include <functional>
-#include <memory>
 
 namespace tinyobj {
 
@@ -51,12 +49,30 @@ typedef struct
     mesh_t       mesh;
 } shape_t;
 
-/// typedef for a function that returns a pointer to an istream for
-/// the material identified by the const std::string&
-typedef std::function< 
-    std::unique_ptr<std::istream>(
-        const std::string&) 
-    > GetMtlIStreamFn;
+class MaterialReader
+{
+public:
+    MaterialReader(){}
+    virtual ~MaterialReader(){}
+
+    virtual std::string operator() (
+        const std::string& matId,
+        std::map<std::string, material_t>& matMap) = 0;
+};
+
+class MaterialFileReader:
+  public MaterialReader
+{
+    public:
+        MaterialFileReader(const std::string& mtl_basepath): m_mtlBasePath(mtl_basepath) {}
+        virtual ~MaterialFileReader() {}
+        virtual std::string operator() (
+          const std::string& matId,
+          std::map<std::string, material_t>& matMap);
+
+    private:
+        std::string m_mtlBasePath;
+};
 
 /// Loads .obj from a file.
 /// 'shapes' will be filled with parsed shape data
@@ -74,7 +90,13 @@ std::string LoadObj(
 std::string LoadObj(
     std::vector<shape_t>& shapes,   // [output]
     std::istream& inStream,
-    GetMtlIStreamFn getMatFn);
+    MaterialReader& readMatFn);
+
+/// Loads materials into std::map
+/// Returns an empty string if successful
+std::string LoadMtl (
+  std::map<std::string, material_t>& material_map,
+  std::istream& inStream);
 };
 
 #endif  // _TINY_OBJ_LOADER_H