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+/*
+ * Copyright (c) 2003-2009, John Wiegley.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ *
+ * - Neither the name of New Artisans LLC nor the names of its
+ *   contributors may be used to endorse or promote products derived from
+ *   this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * @addtogroup util
+ */
+
+/**
+ * @file   stream.h
+ * @author John Wiegley, Omari Norman
+ *
+ * @ingroup util
+ *
+ * @brief A utility class for abstracting an output stream.
+ *
+ * Because Ledger might send output to a file, the console, or a pager
+ * child process, different cleanup is needed for each scenario.  This
+ * file abstracts those various needs.
+ */
+#ifndef _STREAM_H
+#define _STREAM_H
+
+#include "utils.h"
+
+namespace ledger {
+
+/**
+ * @brief An output stream
+ *
+ * A stream to output in Ledger may be going to one of three places:
+ * to stdout, to a file, or to a pager. Construct an output_stream_t and
+ * the stream will automatically be cleaned up upon destruction.
+ *
+ * This class suffers from "else-if-heimer's disease," see Marshall
+ * Cline's "C++ FAQ Lite". Arguably this should be three different
+ * classes, but that introduces additional unneeded complications.
+ */
+class output_stream_t
+{
+  output_stream_t& operator=(const output_stream_t&);
+
+private:
+  int pipe_to_pager_fd;
+
+public:
+  /**
+   * A pointer to the ostream.  Don't delete this; the output_stream_t
+   * class takes care of this.
+   */
+  std::ostream * os;
+
+  /**
+   * Construct a new output_stream_t.
+   */
+  output_stream_t() : pipe_to_pager_fd(-1), os(&std::cout) {
+    TRACE_CTOR(output_stream_t, "");
+  }
+
+  /**
+   * When copy-constructed, make the copy just be a new output stream.  This
+   * allows large classes to rely on their default copy-constructor without
+   * worrying about pointer copying within output_stream_t.
+   */
+  output_stream_t(const output_stream_t&)
+    : pipe_to_pager_fd(-1), os(&std::cout) {
+    TRACE_CTOR(output_stream_t, "copy");
+  }
+
+  /**
+   * Destroys an output_stream_t.  This deletes the dynamically
+   * allocated ostream, if necessary. It also closes output file
+   * descriptor, if necessary.
+   */
+  ~output_stream_t() {
+    TRACE_DTOR(output_stream_t);
+    close();
+  }
+
+  /**
+   * Initialize the output stream object.
+   *
+   * @param output_file File to which to send output. If both this
+   * and pager are set, output_file takes priority.
+   *
+   * @param pager_path Path to a pager. To not use a pager, leave this
+   * empty.
+   */
+  void initialize(const optional<path>& output_file = none,
+		  const optional<path>& pager_path  = none);
+
+  /**
+   * Convertor to a standard ostream.  This is used so that we can
+   * stream directly to an object of type output_stream_t.
+   */
+  operator std::ostream&() {
+    return *os;
+  }
+
+  /**
+   * Flushing function.  A simple proxy for ostream's flush.
+   */
+  void flush() {
+    os->flush();
+  }
+
+  /**
+   * Close the output stream, waiting on the pager process if necessary.
+   */
+  void close();
+};
+
+} // namespace ledger
+
+#endif // _STREAM_H