Add range adapter for streams that allows using range-based for loops

include/stxxl/bits/stream/range.h

@@ -0,0 +1,140 @@
+/***************************************************************************
+ * include/stxxl/bits/stream/range.h
+ *
+ * Part of the STXXL. See http://stxxl.org
+ *
+ * Copyright (C) 2018 Michael Hamann <michael.hamann@kit.edu>
+ *
+ * Distributed under the Boost Software License, Version 1.0.
+ * (See accompanying file LICENSE_1_0.txt or copy at
+ * http://www.boost.org/LICENSE_1_0.txt)
+ **************************************************************************/
+
+#ifndef STXXL_STREAM_RANGE_HEADER
+#define STXXL_STREAM_RANGE_HEADER
+
+#include <tlx/define/likely.hpp>
+
+#include <functional>
+
+namespace stxxl {
+
+//! Stream package subnamespace.
+namespace stream {
+
+//! \addtogroup streampack
+//! \{
+
+//! An output range adapter for a stream, to be used in range-based for loops.
+template <typename InputStream>
+class stream2range
+{
+private:
+ InputStream& m_input;
+
+public:
+ //! Type of the elements of the stream and range
+ using value_type = typename InputStream::value_type;
+
+ class range {
+ private:
+ InputStream* m_stream;
+
+ public:
+ //! Construct a range for the given stream.
+ range(InputStream* stream) : m_stream(stream)
+ { }
+
+ //! Copy constructor: delete as the semantics are broken,
+ //! copies would not be independent.
+ range(const range&) = delete;
+
+ //! Copy assignment: delete as the semantics are broken,
+ //! copies would not be independent.
+ range& operator=(const range&) = delete;
+
+ //! Move constructor
+ range(range&&) = default;
+
+ //! Move assignment
+ range& operator=(range&&) = default;
+
+ //! Increment underlying stream.
+ range& operator ++ ()
+ {
+ ++(*m_stream);
+
+ if (TLX_UNLIKELY(m_stream->empty())) {
+ m_stream = nullptr;
+ }
+
+ return *this;
+ }
+
+ //! Check equality with another range
+ //!
+ //! All ranges pointing to the same stream are equal.
+ //! Ranges pointing past the end are all equal.
+ bool operator == (const range& other)
+ {
+ return m_stream == other.m_stream;
+ }
+
+ //! Check inequality with another range
+ //!
+ //! All ranges pointing to the same stream are equal.
+ //! Ranges pointing past the end are all equal.
+ bool operator != (const range& other)
+ {
+ return m_stream != other.m_stream;
+ }
+
+ //! Dereference the underlying stream.
+ //!
+ //! Dereferencing a range that is past the end is a null
+ //! pointer dereference.
+ const value_type& operator * ()
+ {
+ return *(*m_stream);
+ }
+
+ const value_type* operator -> () const
+ {
+ return &(*(*m_stream));
+ }
+ };
+
+ //! Initialize the stream2range container
+ //!
+ //! Stores a reference to the given input.
+ stream2range(InputStream& input)
+ : m_input(input)
+ { }
+
+ //! Return a range pointing to the current position of the underlying stream.
+ range begin() const
+ {
+ return range(&this->m_input);
+ }
+
+ //! Return a range pointing past the end of any stream.
+ range end() const
+ {
+ return range(nullptr);
+ }
+};
+
+//! Utility function to construct a stream2range container from the given stream.
+template <typename InputStream>
+stream2range<InputStream> range(InputStream& input)
+{
+ return stream2range<InputStream>(input);
+}
+
+
+//! \}
+
+} // namespace stream
+} // namespace stxxl
+
+#endif // !STXXL_STREAM_RANGE_HEADER

include/stxxl/bits/stream/stream.h

@@ -1238,6 +1238,7 @@ class make_tuple<Input1, Input2, Input3, Input4, Input5, Stopper>
 #include <stxxl/bits/stream/choose.h>
 #include <stxxl/bits/stream/materialize.h>
 #include <stxxl/bits/stream/unique.h>
+#include <stxxl/bits/stream/range.h>
 
 #endif // !STXXL_STREAM_STREAM_HEADER
 // vim: et:ts=4:sw=4

tests/stream/CMakeLists.txt

@@ -17,6 +17,7 @@ stxxl_build_test(test_push_sort)
 stxxl_build_test(test_sorted_runs)
 stxxl_build_test(test_stream)
 stxxl_build_test(test_stream1)
+stxxl_build_test(test_range)
 
 add_define(test_stream1 "STXXL_VERBOSE_LEVEL=1")
 add_define(test_push_sort "STXXL_VERBOSE_LEVEL=0")
@@ -32,3 +33,4 @@ stxxl_test(test_push_sort)
 stxxl_test(test_sorted_runs)
 stxxl_test(test_stream)
 stxxl_test(test_stream1)
+stxxl_test(test_range)

tests/stream/test_range.cpp

@@ -0,0 +1,45 @@
+/***************************************************************************
+ * tests/stream/test_range.cpp
+ *
+ * Part of the STXXL. See http://stxxl.org
+ *
+ * Copyright (C) 2018 Michael Hamann <michael.hamann@kit.edu>
+ *
+ * Distributed under the Boost Software License, Version 1.0.
+ * (See accompanying file LICENSE_1_0.txt or copy at
+ * http://www.boost.org/LICENSE_1_0.txt)
+ **************************************************************************/
+
+#include <algorithm>
+#include <cstdint>
+#include <random>
+
+#include <tlx/die.hpp>
+
+#include <stxxl/stream>
+
+int main()
+{
+ constexpr size_t num_values = 1024;
+ using value_type = uint64_t;
+
+ std::vector<value_type> values;
+ values.reserve(num_values);
+
+ for (size_t i = 0; i < num_values; ++i) {
+ values.push_back(i);
+ }
+
+ auto stream = stxxl::stream::streamify(values.begin(), values.end());
+
+ size_t i = 0;
+ for (size_t v : stxxl::stream::range(stream))
+ {
+ die_unequal(i, v);
+ ++i;
+ }
+
+ die_unequal(i, num_values);
+
+ return 0;
+}