If function find(keyword) fails to locate specified keyword in the he…

…ader of the numpy file it returns -1. This indicates problems with header and therefore should be caught properly by raising runtime error.

cnpy.cpp

@@ -68,12 +68,18 @@ void cnpy::parse_npy_header(FILE* fp, unsigned int& word_size, unsigned int*& sh
     int loc1, loc2;
 
     //fortran order
-    loc1 = header.find("fortran_order")+16;
+    loc1 = header.find("fortran_order");
+    if (loc1 < 0)
+        throw std::runtime_error("parse_npy_header: failed to find header keyword: 'fortran_order'");
+    loc1 += 16;
     fortran_order = (header.substr(loc1,5) == "True" ? true : false);
 
     //shape
     loc1 = header.find("(");
     loc2 = header.find(")");
+    if (loc1 < 0 || loc2 < 0)
+        throw std::runtime_error("parse_npy_header: failed to find header keyword: '(' or ')'");
+
     std::string str_shape = header.substr(loc1+1,loc2-loc1-1);
     if(str_shape[str_shape.size()-1] == ',') ndims = 1;
     else ndims = std::count(str_shape.begin(),str_shape.end(),',')+1;
@@ -87,7 +93,10 @@ void cnpy::parse_npy_header(FILE* fp, unsigned int& word_size, unsigned int*& sh
     //endian, word size, data type
     //byte order code | stands for not applicable. 
     //not sure when this applies except for byte array
-    loc1 = header.find("descr")+9;
+    loc1 = header.find("descr");
+    if (loc1 < 0)
+        throw std::runtime_error("parse_npy_header: failed to find header keyword: 'descr'");
+    loc1 += 9;
     bool littleEndian = (header[loc1] == '<' || header[loc1] == '|' ? true : false);
     assert(littleEndian);