fixed example code in README

README.md

@@ -12,7 +12,7 @@ A simple header-only cross-platform C++14 memory mapping library.
 using offset_type = mio::mmap_source::size_type;
 using length_type = mio::mmap_source::size_type;
 
-int handle_error(const std::error_code& ec)
+int handle_error(const std::error_code& error)
 {
     const auto& errmsg = error.message();
     std::printf("error mapping file: %s, exiting...\n", errmsg.c_str());
@@ -25,7 +25,7 @@ int main()
     // length of the mapping would otherwise be expected, with the factory method.
     std::error_code error;
     mio::mmap_source mmap1 = mio::make_mmap_source("log.txt",
-        offset_type(0), mio::mmap_source::use_full_file_size, error);
+        offset_type(0), mio::use_full_file_size, error);
     if(error) { return handle_error(error); }
 
     // Read-write memory map the beginning of some file using the `map` member function.
@@ -42,10 +42,12 @@ int main()
     // Or just change one value with the subscript operator.
     mmap2[mmap2.size() / 2] = 42;
 
-    // Or map using the constructor, which throws a std::error_code upon failure.
+    // You can also create a mapping using the constructor, which throws a
+    // std::error_code upon failure.
     try {
         const auto page_size = mio::page_size();
-        mio::mmap_sink mmap3("another/path/to/file", offset_type(4096), length_type(4096));
+        mio::mmap_sink mmap3("another/path/to/file",
+            offset_type(page_size), length_type(page_size));
         // ...
     } catch(const std::error_code& error) {
         return handle_error(error);

include/mio/mmap.hpp

@@ -24,6 +24,7 @@
 #include "detail/basic_mmap.hpp"
 
 #include <system_error>
+#include <string> // std::char_traits
 
 namespace mio {
 
@@ -41,12 +42,12 @@ template<
     typename CharTraits = std::char_traits<CharT>
 > class basic_mmap
 {
-    using impl_type = detail::basic_mmap<CharT, CharTraits>;
-    impl_type impl_;
-
     static_assert(AccessMode == access_mode::read_only
         || AccessMode == access_mode::read_write,
         "AccessMode must be either read_only or read_write");
+
+    using impl_type = detail::basic_mmap<CharT, CharTraits>;
+    impl_type impl_;
 public:
 
     using value_type = typename impl_type::value_type;
@@ -58,8 +59,8 @@ public:
     using difference_type = typename impl_type::difference_type;
     using iterator = typename impl_type::iterator;
     using const_iterator = typename impl_type::const_iterator;
-    using reverse_iterator = std::reverse_iterator<iterator>;
-    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+    using reverse_iterator = typename impl_type::reverse_iterator;
+    using const_reverse_iterator = typename impl_type::const_reverse_iterator;
     using iterator_category = typename impl_type::iterator_category;
     using handle_type = typename impl_type::handle_type;
 
@@ -70,6 +71,25 @@ public:
      */
     basic_mmap() = default;
 
+    /**
+     * `handle` must be a valid file handle, which is then used to memory map the
+     * requested region. Upon failure a `std::error_code` is thrown, detailing the
+     * cause of the error, and the object remains in an unmapped state.
+     *
+     * When specifying `offset`, there is no need to worry about providing
+     * a value that is aligned with the operating system's page allocation granularity.
+     * This is adjusted by the implementation such that the first requested byte (as
+     * returned by `data` or `begin`), so long as `offset` is valid, will be at `offset`
+     * from the start of the file.
+     */
+    template<typename String>
+    basic_mmap(const String& path, const size_type offset, const size_type length)
+    {
+        std::error_code error;
+        map(path, offset, length, error);
+        if(error) { throw error; }
+    }
+
     /**
      * `handle` must be a valid file handle, which is then used to memory map the
      * requested region. Upon failure a `std::error_code` is thrown, detailing the