Merged branch 'dev_native' into lm_sla_supports_auto

Added igl library files

src/igl/is_stl.cpp

@@ -0,0 +1,64 @@
+#include "is_stl.h"
+#include <string>
+IGL_INLINE bool igl::is_stl(FILE * stl_file, bool & is_ascii)
+{
+
+  //      solid?
+  //   YES      NO
+  //   /         if .stl, definitely binary
+  //  /
+  // perfect size?
+  //      YES     NO
+  //
+  const auto perfect_size = [](FILE * stl_file)->bool
+  {
+    //stl_file = freopen(NULL,"rb",stl_file);
+    // Read 80 header
+    char header[80];
+    if(fread(header,sizeof(char),80,stl_file)!=80)
+    {
+      return false;
+    }
+    // Read number of triangles
+    unsigned int num_tri;
+    if(fread(&num_tri,sizeof(unsigned int),1,stl_file)!=1)
+    {
+      return false;
+    }
+    fseek(stl_file,0,SEEK_END);
+    int file_size = ftell(stl_file);
+    fseek(stl_file,0,SEEK_SET);
+    //stl_file = freopen(NULL,"r",stl_file);
+    return (file_size == 80 + 4 + (4*12 + 2) * num_tri);
+  };
+  // Specifically 80 character header
+  char header[80];
+  char solid[80];
+  is_ascii = true;
+  bool f = true;
+  if(fread(header,1,80,stl_file) != 80)
+  {
+    f = false;
+    goto finish;
+  }
+
+  sscanf(header,"%s",solid);
+  if(std::string("solid") == solid)
+  {
+    f = true;
+    is_ascii = !perfect_size(stl_file);
+  }else
+  {
+    is_ascii = false;
+    f = perfect_size(stl_file);
+  }
+finish:
+  rewind(stl_file);
+  return f;
+}
+
+IGL_INLINE bool igl::is_stl(FILE * stl_file)
+{
+  bool is_ascii;
+  return is_stl(stl_file,is_ascii);
+}