1 files changed, 78 insertions, 0 deletions
diff --git a/attic/example/readwrite_example.cpp b/attic/example/readwrite_example.cpp
new file mode 100644
index 00000000..5a94c561
--- /dev/null
+++ b/attic/example/readwrite_example.cpp
@@ -0,0 +1,78 @@
+#include "afio_pch.hpp"
+
+int main(void)
+{        
+    try
+    {
+        //[readwrite_example
+        namespace afio = BOOST_AFIO_V2_NAMESPACE;
+        namespace asio = BOOST_AFIO_V2_NAMESPACE::asio;
+
+        // Set a dispatcher as current for this thread
+        afio::current_dispatcher_guard h(afio::make_dispatcher().get());
+
+        // Schedule an opening of a file called example_file.txt
+        afio::future<> openfile = afio::async_file("example_file.txt",
+          afio::file_flags::create | afio::file_flags::read_write);
+        
+        // Something a bit surprising for many people is that writing off
+        // the end of a file in AFIO does NOT extend the file and writes
+        // which go past the end will simply fail instead. Why not?
+        // Simple: that's the convention with async file i/o, because
+        // synchronising multiple processes concurrently adjusting a
+        // file's length has significant overhead which is wasted if you
+        // don't need that functionality. Luckily, there is an easy
+        // workaround: either open a file for append-only access, in which
+        // case all writes extend the file for you, or else you explicitly
+        // extend files before writing, like this:
+        afio::future<> resizedfile = afio::async_truncate(openfile, 12);
+    
+        // Config a write gather. You could do this of course as a batch
+        // of writes, but a write gather has optimised host OS support in most
+        // cases, so it's one syscall instead of many.
+        std::vector<asio::const_buffer> buffers;
+        buffers.push_back(asio::const_buffer("He", 2));
+        buffers.push_back(asio::const_buffer("ll", 2));
+        buffers.push_back(asio::const_buffer("o ", 2));
+        buffers.push_back(asio::const_buffer("Wo", 2));
+        buffers.push_back(asio::const_buffer("rl", 2));
+        buffers.push_back(asio::const_buffer("d\n", 2));
+        // Schedule the write gather to offset zero after the resize file
+        afio::future<> written(afio::async_write(resizedfile, buffers, 0));
+        
+        // Have the compiler config the exact same write gather as earlier for you
+        // The compiler assembles an identical sequence of ASIO write gather
+        // buffers for you
+        std::vector<std::string> buffers2={ "He", "ll", "o ", "Wo", "rl", "d\n" };
+        // Schedule this to occur after the previous write completes
+        afio::future<> written2(afio::async_write(written, buffers2, 0));
+        
+        // Schedule making sure the previous batch has definitely reached physical storage
+        // This won't complete until the write is on disc
+        afio::future<> stored(afio::async_sync(written2));
+                
+        // Schedule filling this array from the file. Note how convenient std::array
+        // is and completely replaces C style char buffer[bytes]
+        std::array<char, 12> buffer;
+        afio::future<> read(afio::async_read(stored, buffer, 0));
+            
+        // Schedule the closing and deleting of example_file.txt after the contents read
+        afio::future<> deletedfile(afio::async_rmfile(afio::async_close(read)));
+        
+        // Wait until the buffer has been filled, checking all steps for errors
+        afio::when_all_p(openfile, resizedfile, written, written2, stored, read).get(); /*< waits for file open, resize, write, sync and read to complete, throwing any exceptions encountered >*/
+        
+        // There is actually a io_req<std::string> specialisation you
+        // can use to skip this bit by reading directly into a string ...
+        std::string contents(buffer.begin(), buffer.end());
+        std::cout << "Contents of file is '" << contents << "'" << std::endl;
+
+        // Check remaining ops for errors
+        deletedfile.get();
+        //]
+    }
+    catch(const BOOST_AFIO_V2_NAMESPACE::system_error &e) { std::cerr << "ERROR: program exits via system_error code " << e.code().value() << " (" << e.what() << ")" << std::endl; return 1; }
+    catch(const std::exception &e) { std::cerr << "ERROR: program exits via exception (" << e.what() << ")" << std::endl; return 1; }
+    catch(...) { std::cerr << "ERROR: program exits via " << boost::current_exception_diagnostic_information(true) << std::endl; return 1; }
+    return 0;
+}