Add LexIO::Copy

Copies a buffered reader into a writer.

include/lexio/bufreader.hpp

@@ -108,6 +108,11 @@ class GenericBufReader
         return *this;
     }
 
+    /**
+     * @brief Return underlying Reader.
+     */
+    const READER &Reader() const { return m_wrapped; }
+
     size_t LexRead(uint8_t *outDest, const size_t count)
     {
         BufferView data = LexFillBuffer(count);

include/lexio/core.hpp

@@ -610,4 +610,38 @@ inline size_t Length(SEEKABLE &seekable)
     return len;
 }
 
+//******************************************************************************
+//
+// Utility functions.
+//
+//******************************************************************************
+
+/**
+ * @brief Copy the contents of a buffered reader to a writer until EOF is hit
+ *        on the reader.
+ *
+ * @param writer Writer to copy to.
+ * @param bufReader Buffered read to read from.
+ * @param bufSize Number of bytes to buffer per individual copy.
+ * @return Number of bytes copied.
+ */
+template <typename WRITER, typename BUFFERED_READER, typename = std::enable_if_t<IsWriterV<WRITER>>,
+          typename = std::enable_if_t<IsReaderV<BUFFERED_READER>>>
+inline size_t Copy(WRITER &writer, BUFFERED_READER &bufReader, const size_t bufSize = 8192)
+{
+    size_t count = 0;
+    for (;;)
+    {
+        const BufferView buffer = FillBuffer<BUFFERED_READER>(bufReader, bufSize);
+        if (buffer.second == 0)
+        {
+            return count;
+        }
+
+        const size_t written = Write<WRITER>(writer, buffer.first, buffer.second);
+        ConsumeBuffer<BUFFERED_READER>(bufReader, written);
+        count += written;
+    }
+}
+
 } // namespace LexIO

tests/test_core.cpp

@@ -14,6 +14,8 @@
 //  limitations under the License.
 //
 
+#include <algorithm>
+
 #include "./test.h"
 #include "catch2/catch_all.hpp"
 
@@ -288,3 +290,23 @@ TEST_CASE("Test Length")
 
     REQUIRE(LexIO::Length(basic) == BUFFER_LENGTH);
 }
+
+TEST_CASE("Test Copy")
+{
+    VectorBufReader src = VectorBufReader(GetStream());
+    LexIO::VectorStream dest;
+    const LexIO::VectorStream &cDest = dest;
+
+    REQUIRE(BUFFER_LENGTH == LexIO::Copy(dest, src));
+    REQUIRE(src.Reader().Container() == cDest.Container());
+}
+
+TEST_CASE("Test Copy with a small buffer")
+{
+    VectorBufReader src = VectorBufReader(GetStream());
+    LexIO::VectorStream dest;
+    const LexIO::VectorStream &cDest = dest;
+
+    REQUIRE(BUFFER_LENGTH == LexIO::Copy(dest, src, 4));
+    REQUIRE(src.Reader().Container() == cDest.Container());
+}