Add rw_ops::Reverse.

coding/coding.pro

@@ -27,6 +27,7 @@ SOURCES += \
     zip_reader.cpp \
     mmap_reader.cpp \
     reader_streambuf.cpp \
+    reader_writer_ops.cpp
 
 HEADERS += \
     internal/xmlparser.h \
@@ -81,3 +82,6 @@ HEADERS += \
     file_reader_stream.hpp \
     file_writer_stream.hpp \
     reader_streambuf.hpp \
+    reader_writer_ops.hpp
+
+

coding/coding_tests/coding_tests.pro

@@ -37,7 +37,9 @@ SOURCES += ../../testing/testingmain.cpp \
     file_data_test.cpp \
     zip_reader_test.cpp \
     trie_test.cpp \
+    reader_writer_ops_test.cpp
 
 HEADERS += \
     reader_test.hpp \
     coder_test.hpp \
+

coding/coding_tests/reader_writer_ops_test.cpp

@@ -0,0 +1,78 @@
+#include "../../base/SRC_FIRST.hpp"
+
+#include "../../testing/testing.hpp"
+
+#include "../../coding/reader_writer_ops.hpp"
+#include "../../coding/file_reader.hpp"
+#include "../../coding/file_writer.hpp"
+
+#include "../../std/algorithm.hpp"
+
+
+namespace
+{
+  void GetReverseForReaderAndTmpFile(Reader const & src, vector<char> & buffer)
+  {
+    char const * tmpFile = "reversed_file.tmp";
+
+    {
+      FileWriter writer(tmpFile);
+      rw_ops::Reverse(src, writer);
+    }
+
+    {
+      FileReader reader(tmpFile);
+      buffer.clear();
+      MemWriter<vector<char> > writer(buffer);
+      rw_ops::Reverse(reader, writer);
+    }
+
+    FileWriter::DeleteFileX(tmpFile);
+  }
+
+  void FillRandFile(string const & fName, size_t count)
+  {
+    FileWriter writer(fName);
+
+    srand(666);
+
+    while (count-- > 0)
+    {
+      char const c = rand();
+      writer.Write(&c, 1);
+    }
+  }
+}
+
+UNIT_TEST(Reverse_Smoke)
+{
+  {
+    char arr[] = { 0xA, 0xB, 0xC, 0xD, 0xF };
+    size_t const sz = ARRAY_SIZE(arr);
+
+    MemReader reader(&arr[0], sz);
+
+    vector<char> buffer;
+    GetReverseForReaderAndTmpFile(reader, buffer);
+
+    TEST_EQUAL(buffer.size(), ARRAY_SIZE(arr), ());
+    TEST(equal(arr, arr + ARRAY_SIZE(arr), buffer.begin()), ());
+  }
+
+  char const * tmpFile = "random_file.tmp";
+
+  {
+    FillRandFile(tmpFile, 10 * 1024 + 527);
+    FileReader reader(tmpFile);
+
+    vector<char> buffer;
+    GetReverseForReaderAndTmpFile(reader, buffer);
+
+    string str;
+    reader.ReadAsString(str);
+    TEST_EQUAL(str.size(), buffer.size(), ());
+    TEST(equal(str.begin(), str.end(), buffer.begin()), ());
+
+    FileWriter::DeleteFileX(tmpFile);
+  }
+}

coding/reader_writer_ops.cpp

@@ -0,0 +1,27 @@
+#include "reader_writer_ops.hpp"
+
+namespace rw_ops
+{
+  void Reverse(Reader const & src, Writer & dest)
+  {
+    // Read from end, reverse and write directly.
+
+    size_t const bufSz = 1024;
+    vector<char> buffer(bufSz);
+
+    uint64_t pos = src.Size();
+    while (pos > 0)
+    {
+      size_t const sz = pos > bufSz ? bufSz : pos;
+      ASSERT_GREATER_OR_EQUAL(pos, sz, ());
+
+      src.Read(pos - sz, &buffer[0], sz);
+
+      std::reverse(buffer.begin(), buffer.begin() + sz);
+
+      dest.Write(&buffer[0], sz);
+
+      pos -= sz;
+    }
+  }
+}

coding/reader_writer_ops.hpp

@@ -0,0 +1,11 @@
+#pragma once
+
+#include "reader.hpp"
+#include "writer.hpp"
+
+namespace rw_ops
+{
+  /// Do reverse bytes.
+  /// Note! src and dest should be for different entities.
+  void Reverse(Reader const & src, Writer & dest);
+}