src/base/PackableStream.h

   1 /*
   2  * Copyright (C) 1996-2019 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 #ifndef SQUID_SRC_BASE_PACKABLESTREAM_H
  10 #define SQUID_SRC_BASE_PACKABLESTREAM_H
  11
  12 #include "base/Packable.h"
  13
  14 #include <ostream>
  15
  16 /**
  17  * Provides a streambuf interface for writing to Packable objects.
  18  * Typical use is via a PackableStream rather than direct manipulation
  19  */
  20 class PackableStreamBuf : public std::streambuf
  21 {
  22 public:
  23     explicit PackableStreamBuf(Packable &p) : buf_(p) { buf_.buffer(); }
  24     virtual ~PackableStreamBuf() = default;
  25
  26 protected:
  27     /** flush the current buffer and the character that is overflowing
  28      * to the Packable.
  29      */
  30     virtual int_type overflow(int_type aChar = traits_type::eof()) override {
  31         std::streamsize pending(pptr() - pbase());
  32
  33         if (pending && sync())
  34             return traits_type::eof();
  35
  36         if (aChar != traits_type::eof()) {
  37             const char C = static_cast<char>(aChar);
  38             lowAppend(&C, 1);
  39         }
  40
  41         pbump(-pending);  // Reset pptr().
  42         return aChar;
  43     }
  44
  45     /** push the buffer to the Packable */
  46     virtual int sync() override {
  47         std::streamsize pending(pptr() - pbase());
  48         lowAppend(pbase(), pending);
  49         buf_.flush();
  50         return 0;
  51     }
  52
  53     /** write multiple characters to the Packable
  54      * - this is an optimisation method.
  55      */
  56     virtual std::streamsize xsputn(const char * chars, std::streamsize number) override {
  57         lowAppend(chars, number);
  58         return number;
  59     }
  60
  61 private:
  62     void lowAppend(const char *s, const std::streamsize n) {buf_.append(s,n);}
  63
  64     Packable &buf_;
  65 };
  66
  67 class PackableStream : public std::ostream
  68 {
  69 public:
  70     /* create a stream for writing text etc into theBuffer */
  71     // See http://www.codecomments.com/archive292-2005-2-396222.html
  72     explicit PackableStream(Packable &p) : std::ostream(0), theBuffer(p) {
  73         rdbuf(&theBuffer); // set the buffer to now-initialized theBuffer
  74         clear(); //clear badbit set by calling init(0)
  75     }
  76
  77 private:
  78     PackableStreamBuf theBuffer;
  79 };
  80
  81 #endif /* SQUID_SRC_BASE_PACKABLESTREAM_H */
  82