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amzn-kf8{#header,#content,#footnotes,#footer{padding:0}} 432</style> 433</head> 434<body class="article toc2 toc-left"> 435<div id="header"> 436<h1>Boost.IO</h1> 437<div class="details"> 438<span id="author" class="author">Daryle Walker, Beman Dawes, Glen Joseph Fernandes <glenjofe@gmail.com></span><br> 439</div> 440<div id="toc" class="toc2"> 441<div id="toctitle">Table of Contents</div> 442<ul class="sectlevel1"> 443<li><a href="#io_state_savers_boostioios_state_hpp">IO State Savers, <boost/io/ios_state.hpp></a> 444<ul class="sectlevel2"> 445<li><a href="#description">Description</a></li> 446<li><a href="#rationale">Rationale</a></li> 447<li><a href="#header_synopsis">Header Synopsis</a></li> 448<li><a href="#savers_for_basic_standard_attributes">Savers for Basic Standard Attributes</a></li> 449<li><a href="#savers_for_advanced_standard_attributes">Savers for Advanced Standard Attributes</a></li> 450<li><a href="#savers_for_user_defined_attributes">Savers for User-Defined Attributes</a></li> 451<li><a href="#example">Example</a></li> 452<li><a href="#credits">Credits</a></li> 453<li><a href="#history">History</a></li> 454</ul> 455</li> 456<li><a href="#quoted_manipulators_boostioquoted_hpp">Quoted Manipulators, <boost/io/quoted.hpp></a> 457<ul class="sectlevel2"> 458<li><a href="#introduction">Introduction</a></li> 459<li><a href="#header_synopsis_2">Header synopsis</a></li> 460<li><a href="#acknowledgements">Acknowledgements</a></li> 461</ul> 462</li> 463<li><a href="#delimited_iterators_boostioostream_joiner_hpp">Delimited Iterators, <boost/io/ostream_joiner.hpp></a> 464<ul class="sectlevel2"> 465<li><a href="#description_2">Description</a></li> 466<li><a href="#example_2">Example</a></li> 467<li><a href="#reference">Reference</a></li> 468<li><a href="#acknowledgments">Acknowledgments</a></li> 469</ul> 470</li> 471<li><a href="#insert_formatted_output_boostioostream_put_hpp">Insert Formatted Output, <boost/io/ostream_put.hpp></a> 472<ul class="sectlevel2"> 473<li><a href="#description_3">Description</a></li> 474<li><a href="#example_3">Example</a></li> 475<li><a href="#reference_2">Reference</a></li> 476<li><a href="#acknowledgments_2">Acknowledgments</a></li> 477</ul> 478</li> 479<li><a href="#copyright_and_license">Copyright and License</a></li> 480</ul> 481</div> 482</div> 483<div id="content"> 484<div id="preamble"> 485<div class="sectionbody"> 486<div class="paragraph"> 487<p>This library contains various utilities for the standard I/O library.</p> 488</div> 489</div> 490</div> 491<div class="sect1"> 492<h2 id="io_state_savers_boostioios_state_hpp">IO State Savers, <boost/io/ios_state.hpp></h2> 493<div class="sectionbody"> 494<div class="sect2"> 495<h3 id="description">Description</h3> 496<div class="paragraph"> 497<p>The header <code><boost/io/ios_state.hpp></code> covers saving the stream state of objects 498in the C++ IOStreams system.</p> 499</div> 500</div> 501<div class="sect2"> 502<h3 id="rationale">Rationale</h3> 503<div class="paragraph"> 504<p>Sometimes a certain value has to change only for a limited scope. Saver classes 505save a copy of the current state of some object (or an aspect of an object), 506and reset the object’s state at destruction time, undoing any change the object 507may have gone through.</p> 508</div> 509<div class="paragraph"> 510<p>The saver class strategy is helpful when using I/O stream objects. Manipulator 511objects can change some aspect of a stream during input or output. The state 512changed by the manipulator usually sticks to its new value after the I/O 513transaction. This can be a problem if manipulators are used in a function that 514is not supposed to externally change a stream’s state.</p> 515</div> 516<div class="listingblock"> 517<div class="content"> 518<pre class="highlight"><code class="language-cpp" data-lang="cpp">#include <ostream> 519#include <ios> 520 521void hex_my_byte(std::ostream& os, char byte) 522{ 523 os << std::hex << static_cast<unsigned>(byte); 524}</code></pre> 525</div> 526</div> 527<div class="paragraph"> 528<p>The <code>os</code> stream will retain its new hexadecimal printing mode after the call to 529<code>hex_my_byte</code>. The stream’s printing mode can be saved and restored with manual 530calls to the stream’s state inspecting and mutating member functions. The 531manual method becomes unwieldy if the main functionality is complex and/or 532needs to be exception safe. A saver class can implement the better 533"resource acquisition is initialization" strategy.</p> 534</div> 535<div class="paragraph"> 536<p>See the example below for better code, using saver classes.</p> 537</div> 538</div> 539<div class="sect2"> 540<h3 id="header_synopsis">Header Synopsis</h3> 541<div class="listingblock"> 542<div class="content"> 543<pre class="highlight"><code class="language-cpp" data-lang="cpp">namespace boost { 544namespace io { 545 546class ios_flags_saver; 547class ios_precision_saver; 548class ios_width_saver; 549class ios_base_all_saver; 550 551template<class Ch, class Tr = std::char_traits<Ch> > 552class basic_ios_iostate_saver; 553 554template<class Ch, class Tr = std::char_traits<Ch> > 555class basic_ios_exception_saver; 556 557template<class Ch, class Tr = std::char_traits<Ch> > 558class basic_ios_tie_saver; 559 560template<class Ch, class Tr = std::char_traits<Ch> > 561class basic_ios_rdbuf_saver; 562 563template<class Ch, class Tr = std::char_traits<Ch> > 564class basic_ios_fill_saver; 565 566template<class Ch, class Tr = std::char_traits<Ch> > 567class basic_ios_locale_saver; 568 569template<class Ch, class Tr = std::char_traits<Ch> > 570class basic_ios_all_saver; 571 572typedef basic_ios_iostate_saver<char> ios_iostate_saver; 573typedef basic_ios_iostate_saver<wchar_t> wios_iostate_saver; 574typedef basic_ios_exception_saver<char> ios_exception_saver; 575typedef basic_ios_exception_saver<wchar_t> wios_exception_saver; 576typedef basic_ios_tie_saver<char> ios_tie_saver; 577typedef basic_ios_tie_saver<wchar_t> wios_tie_saver; 578typedef basic_ios_rdbuf_saver<char> ios_rdbuf_saver; 579typedef basic_ios_rdbuf_saver<wchar_t> wios_rdbuf_saver; 580typedef basic_ios_fill_saver<char> ios_fill_saver; 581typedef basic_ios_fill_saver<wchar_t> wios_fill_saver; 582typedef basic_ios_locale_saver<char> ios_locale_saver; 583typedef basic_ios_locale_saver<wchar_t> wios_locale_saver; 584typedef basic_ios_all_saver<char> ios_all_saver; 585typedef basic_ios_all_saver<wchar_t> wios_all_saver; 586 587class ios_iword_saver; 588class ios_pword_saver; 589class ios_all_word_saver; 590 591} // io 592} // boost</code></pre> 593</div> 594</div> 595</div> 596<div class="sect2"> 597<h3 id="savers_for_basic_standard_attributes">Savers for Basic Standard Attributes</h3> 598<div class="paragraph"> 599<p>The basic saver classes have this format:</p> 600</div> 601<div class="listingblock"> 602<div class="content"> 603<pre class="highlight"><code class="language-cpp" data-lang="cpp">class saver { 604public: 605 typedef std::ios_base state_type; 606 typedef <code>implementation_defined</code> aspect_type; 607 608 explicit saver(state_type& s); 609 saver(state_type& s, const aspect_type& new_value); 610 ~saver(); 611 612 void restore(); 613};</code></pre> 614</div> 615</div> 616<div class="paragraph"> 617<p>The <code>state_type</code> is the IOStreams base class <code>std::ios_base</code>. The user would 618usually place an actual input, output, or combined stream object for the 619state-type parameter, and not a base class object. The first constructor takes 620a stream object and saves a reference to the stream and the current value of a 621particular stream attribute. The second constructor works like the first, and 622uses its second argument to change the stream’s attribute to the new 623<code>aspect_type</code> value given. The destructor restores the stream’s attribute to 624the saved value. The restoration can be activated early (and often) with the 625<code>restore</code> member function.</p> 626</div> 627<table class="tableblock frame-all grid-all stretch"> 628<caption class="title">Table 1. Basic IOStreams State Saver Classes</caption> 629<colgroup> 630<col style="width: 20%;"> 631<col style="width: 20%;"> 632<col style="width: 20%;"> 633<col style="width: 20%;"> 634<col style="width: 20%;"> 635</colgroup> 636<thead> 637<tr> 638<th class="tableblock halign-left valign-top">Class</th> 639<th class="tableblock halign-left valign-top">Saved Attribute</th> 640<th class="tableblock halign-left valign-top">Attribute Type</th> 641<th class="tableblock halign-left valign-top">Reading Method</th> 642<th class="tableblock halign-left valign-top">Writing Method</th> 643</tr> 644</thead> 645<tbody> 646<tr> 647<td class="tableblock halign-left valign-top"><p class="tableblock"><code>ios_flags_saver</code></p></td> 648<td class="tableblock halign-left valign-top"><p class="tableblock">Format control flags</p></td> 649<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::ios_base::fmtflags</code></p></td> 650<td class="tableblock halign-left valign-top"><p class="tableblock"><code>flags</code></p></td> 651<td class="tableblock halign-left valign-top"><p class="tableblock"><code>flags</code></p></td> 652</tr> 653<tr> 654<td class="tableblock halign-left valign-top"><p class="tableblock"><code>ios_precision_saver</code></p></td> 655<td class="tableblock halign-left valign-top"><p class="tableblock">Number of digits to print after decimal point</p></td> 656<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::streamsize</code></p></td> 657<td class="tableblock halign-left valign-top"><p class="tableblock"><code>precision</code></p></td> 658<td class="tableblock halign-left valign-top"><p class="tableblock"><code>precision</code></p></td> 659</tr> 660<tr> 661<td class="tableblock halign-left valign-top"><p class="tableblock"><code>ios_width_saver</code></p></td> 662<td class="tableblock halign-left valign-top"><p class="tableblock">Minimum field width for printing objects</p></td> 663<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::streamsize</code></p></td> 664<td class="tableblock halign-left valign-top"><p class="tableblock"><code>width</code></p></td> 665<td class="tableblock halign-left valign-top"><p class="tableblock"><code>width</code></p></td> 666</tr> 667</tbody> 668</table> 669</div> 670<div class="sect2"> 671<h3 id="savers_for_advanced_standard_attributes">Savers for Advanced Standard Attributes</h3> 672<div class="paragraph"> 673<p>The saver class templates have this format:</p> 674</div> 675<div class="listingblock"> 676<div class="content"> 677<pre class="highlight"><code class="language-cpp" data-lang="cpp">template<class Ch, class Tr> 678class saver { 679public: 680 typedef std::basic_ios<Ch, Tr> state_type; 681 typedef <code>implementation-defined</code> aspect_type; 682 683 explicit saver(state_type& s); 684 saver(state_type& s, const aspect_type& new_value); 685 ~saver(); 686 687 void restore(); 688};</code></pre> 689</div> 690</div> 691<div class="paragraph"> 692<p>The <code>state_type</code> is a version of the IOStreams base class template 693<code>std::basic_ios<Ch, Tr></code>, where <code>Ch</code> is a character type and <code>Tr</code> is a 694character traits class. The user would usually place an actual input, 695output, or combined stream object for the state-type parameter, and not a base 696class object. The first constructor takes a stream object and saves a reference 697to the stream and the current value of a particular stream attribute. The 698second constructor works like the first, and uses its second argument to change 699the stream’s attribute to the new <code>aspect_type</code> value given. The destructor 700restores the stream’s attribute to the saved value. The restoration can be 701activated early (and often) with the <code>restore</code> member function.</p> 702</div> 703<table class="tableblock frame-all grid-all stretch"> 704<caption class="title">Table 2. Advanced IOStreams State Saver Class Templates</caption> 705<colgroup> 706<col style="width: 20%;"> 707<col style="width: 20%;"> 708<col style="width: 20%;"> 709<col style="width: 20%;"> 710<col style="width: 20%;"> 711</colgroup> 712<thead> 713<tr> 714<th class="tableblock halign-left valign-top">Class</th> 715<th class="tableblock halign-left valign-top">Saved Attribute</th> 716<th class="tableblock halign-left valign-top">Attribute Type</th> 717<th class="tableblock halign-left valign-top">Reading Method</th> 718<th class="tableblock halign-left valign-top">Writing Method</th> 719</tr> 720</thead> 721<tbody> 722<tr> 723<td class="tableblock halign-left valign-top"><p class="tableblock"><code>basic_ios_iostate_saver<Ch, Tr></code></p></td> 724<td class="tableblock halign-left valign-top"><p class="tableblock">Failure state of the stream [1], [2]</p></td> 725<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::ios_base::iostate</code></p></td> 726<td class="tableblock halign-left valign-top"><p class="tableblock"><code>rdstate</code></p></td> 727<td class="tableblock halign-left valign-top"><p class="tableblock"><code>clear</code></p></td> 728</tr> 729<tr> 730<td class="tableblock halign-left valign-top"><p class="tableblock"><code>basic_ios_exception_saver<Ch, Tr></code></p></td> 731<td class="tableblock halign-left valign-top"><p class="tableblock">Which failure states trigger an exception [1]</p></td> 732<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::ios_base::iostate</code></p></td> 733<td class="tableblock halign-left valign-top"><p class="tableblock"><code>exceptions</code></p></td> 734<td class="tableblock halign-left valign-top"><p class="tableblock"><code>exceptions</code></p></td> 735</tr> 736<tr> 737<td class="tableblock halign-left valign-top"><p class="tableblock"><code>basic_ios_tie_saver<Ch, Tr></code></p></td> 738<td class="tableblock halign-left valign-top"><p class="tableblock">Output stream synchronized with the stream</p></td> 739<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::basic_ostream<Ch, Tr>*</code></p></td> 740<td class="tableblock halign-left valign-top"><p class="tableblock"><code>tie</code></p></td> 741<td class="tableblock halign-left valign-top"><p class="tableblock"><code>tie</code></p></td> 742</tr> 743<tr> 744<td class="tableblock halign-left valign-top"><p class="tableblock"><code>basic_ios_rdbuf_saver<Ch, Tr></code></p></td> 745<td class="tableblock halign-left valign-top"><p class="tableblock">Stream buffer associated with the stream [2]</p></td> 746<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::basic_streambuf<Ch, Tr>*</code></p></td> 747<td class="tableblock halign-left valign-top"><p class="tableblock"><code>rdbuf</code></p></td> 748<td class="tableblock halign-left valign-top"><p class="tableblock"><code>rdbuf</code></p></td> 749</tr> 750<tr> 751<td class="tableblock halign-left valign-top"><p class="tableblock"><code>basic_ios_fill_saver<Ch, Tr></code></p></td> 752<td class="tableblock halign-left valign-top"><p class="tableblock">Character used to pad oversized field widths</p></td> 753<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Ch</code></p></td> 754<td class="tableblock halign-left valign-top"><p class="tableblock"><code>fill</code></p></td> 755<td class="tableblock halign-left valign-top"><p class="tableblock"><code>fill</code></p></td> 756</tr> 757<tr> 758<td class="tableblock halign-left valign-top"><p class="tableblock"><code>basic_ios_locale_saver<Ch, Tr></code></p></td> 759<td class="tableblock halign-left valign-top"><p class="tableblock">Locale information associated with the stream [3]</p></td> 760<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::locale</code></p></td> 761<td class="tableblock halign-left valign-top"><p class="tableblock"><code>getloc</code> (from <code>std::ios_base</code>)</p></td> 762<td class="tableblock halign-left valign-top"><p class="tableblock"><code>imbue</code> (from <code>std::basic_ios<Ch, Tr></code>)</p></td> 763</tr> 764</tbody> 765</table> 766<div class="sect3"> 767<h4 id="notes">Notes</h4> 768<div class="olist arabic"> 769<ol class="arabic"> 770<li> 771<p>When the failure state flags and/or the failure state exception watching 772flags are changed, an exception is thrown if a match occurs among the two sets 773of flags. This could mean that the constructor or destructor of these class 774templates may throw.</p> 775</li> 776<li> 777<p>When the associated stream buffer is changed, the stream’s failure state set 778is reset to "good" if the given stream buffer’s address is non-NULL, but the 779"bad" failure state is set if that address is NULL. This means that a saved 780failure state of "good" may be restored as "bad" if the stream is stripped of 781an associated stream buffer. Worse, given a NULL stream buffer address, an 782exception is thrown if the "bad" failure state is being watched. This could 783mean that the constructor or destructor of these class templates may throw.</p> 784</li> 785<li> 786<p>The saver for the locale uses the <code>std::basic_ios<Ch, Tr></code> class to extract 787their information, although it could have used the functionality in 788<code>std::ios_base</code>. The problem is that the versions of the needed member 789functions in <code>ios_base</code> are not polymorphically related to the ones in 790<code>basic_ios</code>. The stream classes that will be used with the saver classes should 791use the versions of the member functions closest to them by inheritance, which 792means the ones in <code>basic_ios</code>.</p> 793</li> 794</ol> 795</div> 796</div> 797</div> 798<div class="sect2"> 799<h3 id="savers_for_user_defined_attributes">Savers for User-Defined Attributes</h3> 800<div class="paragraph"> 801<p>There are three class (templates) for combined attribute savers. The 802<code>ios_base_all_saver</code> saver class combines the functionality of all the basic 803attribute saver classes. It has a constructor that takes the stream to have its 804state preserved. The <code>basic_ios_all_saver</code> combines the functionality of all 805the advanced attribute saver class templates and the combined basic attribute 806saver class. It has a constructor that takes the stream to have its state 807preserved. The <code>ios_all_word_saver</code> saver class combines the saver classes that 808preserve user-defined formatting information. Its constructor takes the stream 809to have its attributes saved and the index of the user-defined attributes. The 810destructor for each class restores the saved state. Restoration can be 811activated early (and often) for a class with the restore member function.</p> 812</div> 813</div> 814<div class="sect2"> 815<h3 id="example">Example</h3> 816<div class="paragraph"> 817<p>The code used in the rationale can be improved at two places. The printing 818function could use a saver around the code that changes the formatting state. 819Or the calling function can surround the call with a saver. Or both can be 820done, especially if the user does not know if the printing function uses a 821state saver. If the user wants a series of changes back and forth, without 822surrounding each change within a separate block, the restore member function 823can be called between each trial.</p> 824</div> 825<div class="listingblock"> 826<div class="content"> 827<pre class="highlight"><code class="language-cpp" data-lang="cpp">#include <boost/io/ios_state.hpp> 828#include <ios> 829#include <iostream> 830#include <ostream> 831 832void new_hex_my_byte(std::ostream& os, char byte) 833{ 834 boost::io::ios_flags_saver ifs(os); 835 os << std::hex << static_cast<unsigned>(byte); 836} 837 838int main() 839{ 840 // ... 841 { 842 boost::io::ios_all_saver ias(std::cout); 843 new_hex_my_byte(std::cout, 'A'); 844 } 845 // ... 846 { 847 boost::io::ios_all_saver ias(std::cerr); 848 new_hex_my_byte(std::cerr, 'b'); 849 ias.restore(); 850 new_hex_my_byte(std::cerr, 'C'); 851 } 852 // ... 853}</code></pre> 854</div> 855</div> 856</div> 857<div class="sect2"> 858<h3 id="credits">Credits</h3> 859<div class="sect3"> 860<h4 id="daryle_walker">Daryle Walker</h4> 861<div class="paragraph"> 862<p>Started the library. Contributed the initial versions of the format flags, 863precision, width, and user-defined format flags saver classes. Contributed the 864initial versions of the success state, success state exception flags, output 865stream tie, stream buffer, character fill, and locale saver class templates. 866Contributed the combined attribute classes and class template. Contributed the 867test file <code>ios_state_test.cpp</code>.</p> 868</div> 869</div> 870</div> 871<div class="sect2"> 872<h3 id="history">History</h3> 873<div class="sect3"> 874<h4 id="20_dec_2019">20 Dec 2019</h4> 875<div class="paragraph"> 876<p>Glen Fernandes made all the saver classes non-copyable.</p> 877</div> 878</div> 879<div class="sect3"> 880<h4 id="28_feb_2005">28 Feb 2005</h4> 881<div class="paragraph"> 882<p>Daryle Walker added the restore member functions, based on suggestions by 883Gennadiy Rozental and Rob Stewart.</p> 884</div> 885</div> 886<div class="sect3"> 887<h4 id="13_mar_2002">13 Mar 2002</h4> 888<div class="paragraph"> 889<p>Daryle Walker implemented the initial version.</p> 890</div> 891</div> 892</div> 893</div> 894</div> 895<div class="sect1"> 896<h2 id="quoted_manipulators_boostioquoted_hpp">Quoted Manipulators, <boost/io/quoted.hpp></h2> 897<div class="sectionbody"> 898<div class="sect2"> 899<h3 id="introduction">Introduction</h3> 900<div class="paragraph"> 901<p>C++ Standard library stream I/O for strings that contain embedded spaces can 902produce unexpected results. For example,</p> 903</div> 904<div class="listingblock"> 905<div class="content"> 906<pre class="highlight"><code class="language-cpp" data-lang="cpp">std::stringstream ss; 907std::string original = "fooled you"; 908std::string roundtrip; 909 910ss << original; 911ss >> roundtrip; 912 913std::cout << original; // outputs: fooled you 914std::cout << roundtrip; // outputs: fooled 915 916assert(original == roundtrip); // assert will fire</code></pre> 917</div> 918</div> 919<div class="paragraph"> 920<p>The Boost quoted stream I/O manipulator places delimiters, defaulted to the 921double-quote ("), around strings on output, and strips off the delimiters on 922input. This ensures strings with embedded spaces round-trip as desired. For 923example,</p> 924</div> 925<div class="listingblock"> 926<div class="content"> 927<pre class="highlight"><code class="language-cpp" data-lang="cpp">std::stringstream ss; 928std::string original = "fooled you"; 929std::string roundtrip; 930 931ss << quoted(original); 932ss >> quoted(roundtrip); 933 934std::cout << quoted(original); // outputs: "fooled you" 935std::cout << roundtrip; // outputs: fooled you 936 937assert(original == roundtrip); // assert will not fire</code></pre> 938</div> 939</div> 940<div class="paragraph"> 941<p>If the string contains the delimiter character, on output that character will 942be preceded by an escape character, as will the escape character itself:</p> 943</div> 944<div class="listingblock"> 945<div class="content"> 946<pre class="highlight"><code class="language-cpp" data-lang="cpp">std::cout << quoted("'Jack & Jill'", '&', '\''); // outputs: '&'Jack && Jill&''</code></pre> 947</div> 948</div> 949</div> 950<div class="sect2"> 951<h3 id="header_synopsis_2">Header synopsis</h3> 952<div class="listingblock"> 953<div class="content"> 954<pre class="highlight"><code class="language-cpp" data-lang="cpp">namespace boost { 955namespace io { 956 957template<class Char, class Traits, class Alloc> 958<code>unspecified-type1</code> 959quoted(const std::basic_string<Char, Traits, Alloc>& string, 960 Char escape='\\', Char delim='\"'); 961 962template<class Char> 963<code>unspecified-type2</code> 964quoted(const Char* string, Char escape='\\', Char delim='\"'); 965 966template<class Char, class Traits, class Alloc> 967<code>unspecified-type3</code> 968quoted(std::basic_string<Char, Traits, Alloc>& string, 969 Char escape='\\', Char delim='\"'); 970 971} // io 972} // boost</code></pre> 973</div> 974</div> 975<div class="paragraph"> 976<p><strong>unspecified-type1</strong>, <strong>unspecified-type2</strong>, and <strong>unspecified-type3</strong> are 977implementation supplied types with implementation supplied <code>operator<<</code>:</p> 978</div> 979<div class="listingblock"> 980<div class="content"> 981<pre class="highlight"><code class="language-cpp" data-lang="cpp">template<class Char, class Traits> 982std::basic_ostream<Char, Traits>& 983operator<<(std::basic_ostream<Char, Traits>& os, 984 const <code>unspecified-typeN</code>& proxy);</code></pre> 985</div> 986</div> 987<div class="dlist"> 988<dl> 989<dt class="hdlist1">Effects</dt> 990<dd> 991<p>Inserts characters into <code>os</code>:</p> 992<div class="ulist"> 993<ul> 994<li> 995<p><code>delim</code></p> 996</li> 997<li> 998<p>Each character in <code>string</code>. If the character to be output is equal to 999<code>escape</code> or <code>delim</code>, as determined by <code>operator==</code>, first output <code>escape</code>.</p> 1000</li> 1001<li> 1002<p><code>delim</code></p> 1003</li> 1004</ul> 1005</div> 1006</dd> 1007<dt class="hdlist1">Remarks</dt> 1008<dd> 1009<p><code>string</code>, <code>escape</code>, and <code>delim</code> have the type and value of the 1010corresponding arguments of the call to the <code>quoted</code> function that constructed 1011<code>proxy</code>.</p> 1012</dd> 1013<dt class="hdlist1">Returns</dt> 1014<dd> 1015<p><code>os</code>.</p> 1016</dd> 1017</dl> 1018</div> 1019<div class="paragraph"> 1020<p><strong>unspecified-type3</strong> is an implementation supplied type with an implementation 1021supplied <code>operator>></code>:</p> 1022</div> 1023<div class="listingblock"> 1024<div class="content"> 1025<pre class="highlight"><code class="language-cpp" data-lang="cpp">template<class Char, class Traits> 1026std::basic_istream<Char, Traits>& 1027operator>>(std::basic_istream<Char, Traits>& is, 1028 const <code>unspecified-type3</code>& proxy);</code></pre> 1029</div> 1030</div> 1031<div class="dlist"> 1032<dl> 1033<dt class="hdlist1">Effects</dt> 1034<dd> 1035<p>Extracts characters from <code>os</code>:</p> 1036<div class="ulist"> 1037<ul> 1038<li> 1039<p>If the first character extracted is equal to <code>delim</code>, as determined by 1040<code>operator==</code>, then:</p> 1041<div class="ulist"> 1042<ul> 1043<li> 1044<p>Turn off the <code>skipws</code> flag.</p> 1045</li> 1046<li> 1047<p><code>string.clear()</code></p> 1048</li> 1049<li> 1050<p>Until an unescaped <code>delim</code> character is reached or <code>is.not_good()</code>, extract 1051characters from <code>os</code> and append them to string, except that if an escape is 1052reached, ignore it and append the next character to string.</p> 1053</li> 1054<li> 1055<p>Discard the final <code>delim</code> character.</p> 1056</li> 1057<li> 1058<p>Restore the <code>skipws</code> flag to its original value.</p> 1059</li> 1060</ul> 1061</div> 1062</li> 1063<li> 1064<p>Otherwise, <code>os >> string</code>.</p> 1065</li> 1066</ul> 1067</div> 1068</dd> 1069<dt class="hdlist1">Remarks</dt> 1070<dd> 1071<p><code>string</code>, <code>escape</code>, and <code>delim</code> have the type and value of the 1072corresponding arguments of the call to the <code>quoted</code> function that constructed 1073<code>proxy</code>.</p> 1074</dd> 1075<dt class="hdlist1">Returns</dt> 1076<dd> 1077<p><code>is</code>.</p> 1078</dd> 1079</dl> 1080</div> 1081</div> 1082<div class="sect2"> 1083<h3 id="acknowledgements">Acknowledgements</h3> 1084<div class="paragraph"> 1085<p>The <code>quoted()</code> stream manipulator emerged from discussions on the Boost 1086developers mailing list. Participants included Beman Dawes, Rob Stewart, 1087Alexander Lamaison, Eric Niebler, Vicente Botet, Andrey Semashev, 1088Phil Richards, and Rob Murray. Eric Niebler’s suggestions provided the basis 1089for the name and form of the templates.</p> 1090</div> 1091<div class="paragraph"> 1092<p>Beman Dawes started the implementation of <code>quoted()</code> as a private detail 1093header. Glen Fernandes updated the implementation and also made it public.</p> 1094</div> 1095<div class="paragraph"> 1096<p>Glen Fernandes corrected the implementation to properly account for stream 1097width and fill, and optimized it to write directly to the stream buffer.</p> 1098</div> 1099</div> 1100</div> 1101</div> 1102<div class="sect1"> 1103<h2 id="delimited_iterators_boostioostream_joiner_hpp">Delimited Iterators, <boost/io/ostream_joiner.hpp></h2> 1104<div class="sectionbody"> 1105<div class="sect2"> 1106<h3 id="description_2">Description</h3> 1107<div class="paragraph"> 1108<p>The header <code><boost/io/ostream_joiner.hpp></code> provides the class template 1109<code>boost::io::ostream_joiner</code> which is an output iterator that writes objects to 1110a <code>std::basic_ostream</code> separated by a delimiter. It is an implementation of 1111the Library Fundamentals TS <code>std::ostream_joiner</code> which supports C++03 and 1112higher.</p> 1113</div> 1114</div> 1115<div class="sect2"> 1116<h3 id="example_2">Example</h3> 1117<div class="paragraph"> 1118<p>The following program writes the contents of a vector to standard output, with 1119each element separated by a comma.</p> 1120</div> 1121<div class="listingblock"> 1122<div class="content"> 1123<pre class="highlight"><code class="language-cpp" data-lang="cpp">#include <boost/io/ostream_joiner.hpp> 1124#include <algorithm> 1125#include <iostream> 1126#include <vector> 1127 1128int main() 1129{ 1130 std::vector<int> v; 1131 v.push_back(2); 1132 v.push_back(4); 1133 v.push_back(6); 1134 v.push_back(8); 1135 std::copy(v.begin(), v.end(), boost::make_ostream_joiner(std::cout, ',')); 1136}</code></pre> 1137</div> 1138</div> 1139</div> 1140<div class="sect2"> 1141<h3 id="reference">Reference</h3> 1142<div class="sect3"> 1143<h4 id="header_synopsis_3">Header Synopsis</h4> 1144<div class="listingblock"> 1145<div class="content"> 1146<pre class="highlight"><code class="language-cpp" data-lang="cpp">namespace boost { 1147namespace io { 1148 1149template<class Delim, class Char = char, 1150 class Traits = std::char_traits<Char> > 1151class ostream_joiner { 1152public: 1153 typedef Char char_type; 1154 typedef Traits traits_type; 1155 typedef std::basic_ostream<Char, Traits> ostream_type; 1156 typedef std::output_iterator_tag iterator_category; 1157 typedef void value_type; 1158 typedef void difference_type; 1159 typedef void pointer; 1160 typedef void reference; 1161 1162 ostream_joiner(ostream_type& output, const Delim& delim); 1163 ostream_joiner(ostream_type& output, Delim&& delim); 1164 1165 template<class T> 1166 ostream_joiner& operator=(const T& value); 1167 1168 ostream_joiner& operator*() noexcept; 1169 ostream_joiner& operator++() noexcept; 1170 ostream_joiner& operator++(int) noexcept; 1171}; 1172 1173template<class Char, class Traits, class Delim> 1174ostream_joiner<std::decay_t<Delim>, Char, Traits> 1175make_ostream_joiner(std::basic_ostream<Char, Traits>& output, Delim&& delim); 1176 1177} // io 1178} // boost</code></pre> 1179</div> 1180</div> 1181</div> 1182<div class="sect3"> 1183<h4 id="constructors">Constructors</h4> 1184<div class="listingblock"> 1185<div class="content"> 1186<pre class="highlight"><code class="language-cpp" data-lang="cpp">ostream_joiner(ostream_type& output, const Delim& delim);</code></pre> 1187</div> 1188</div> 1189<div class="dlist specification"> 1190<dl> 1191<dt class="hdlist1">EFfects</dt> 1192<dd> 1193<p>Initializes the stored reference to the stream with 1194<code>std::addressof(output)</code> and the stored delimiter with <code>delim</code>.</p> 1195</dd> 1196</dl> 1197</div> 1198<div class="listingblock"> 1199<div class="content"> 1200<pre class="highlight"><code class="language-cpp" data-lang="cpp">ostream_joiner(ostream_type& output, Delim&& delim);</code></pre> 1201</div> 1202</div> 1203<div class="dlist specification"> 1204<dl> 1205<dt class="hdlist1">EFfects</dt> 1206<dd> 1207<p>Initializes the stored reference to the stream with 1208<code>std::addressof(output)</code> and the stored delimiter with <code>std::move(delim)</code>.</p> 1209</dd> 1210</dl> 1211</div> 1212</div> 1213<div class="sect3"> 1214<h4 id="member_functions">Member functions</h4> 1215<div class="listingblock"> 1216<div class="content"> 1217<pre class="highlight"><code class="language-cpp" data-lang="cpp">template<class T> 1218ostream_joiner& operator=(const T& value);</code></pre> 1219</div> 1220</div> 1221<div class="dlist specification"> 1222<dl> 1223<dt class="hdlist1">Effects</dt> 1224<dd> 1225<p>If the is the first call to this member function, write the stored 1226delimiter to the stored stream reference. Writes <code>value</code> to the stored stream 1227reference.</p> 1228</dd> 1229<dt class="hdlist1">Returns</dt> 1230<dd> 1231<p><code>*this</code>.</p> 1232</dd> 1233</dl> 1234</div> 1235<div class="listingblock"> 1236<div class="content"> 1237<pre class="highlight"><code class="language-cpp" data-lang="cpp">ostream_joiner& operator*() noexcept;</code></pre> 1238</div> 1239</div> 1240<div class="listingblock"> 1241<div class="content"> 1242<pre class="highlight"><code class="language-cpp" data-lang="cpp">ostream_joiner& operator++() noexcept;</code></pre> 1243</div> 1244</div> 1245<div class="listingblock"> 1246<div class="content"> 1247<pre class="highlight"><code class="language-cpp" data-lang="cpp">ostream_joiner& operator++(int) noexcept;</code></pre> 1248</div> 1249</div> 1250<div class="dlist specification"> 1251<dl> 1252<dt class="hdlist1">Returns</dt> 1253<dd> 1254<p><code>*this</code>.</p> 1255</dd> 1256</dl> 1257</div> 1258</div> 1259<div class="sect3"> 1260<h4 id="free_functions">Free functions</h4> 1261<div class="listingblock"> 1262<div class="content"> 1263<pre class="highlight"><code class="language-cpp" data-lang="cpp">template<class Char, class Traits, class Delim> 1264ostream_joiner<decay_t<Delim>, Char, Traits> 1265make_ostream_joiner(std::basic_ostream<Char, Traits>& output, Delim&& delim);</code></pre> 1266</div> 1267</div> 1268<div class="dlist specification"> 1269<dl> 1270<dt class="hdlist1">Returns</dt> 1271<dd> 1272<p><code>ostream_joiner<std::decay_t<Delim>, Char, Traits>(output, 1273std::forward<Delim>(delim))</code>.</p> 1274</dd> 1275</dl> 1276</div> 1277</div> 1278</div> 1279<div class="sect2"> 1280<h3 id="acknowledgments">Acknowledgments</h3> 1281<div class="paragraph"> 1282<p>Glen Fernandes implemented <code>ostream_joiner</code> and <code>make_ostream_joiner</code>.</p> 1283</div> 1284</div> 1285</div> 1286</div> 1287<div class="sect1"> 1288<h2 id="insert_formatted_output_boostioostream_put_hpp">Insert Formatted Output, <boost/io/ostream_put.hpp></h2> 1289<div class="sectionbody"> 1290<div class="sect2"> 1291<h3 id="description_3">Description</h3> 1292<div class="paragraph"> 1293<p>The header <code><boost/io/ostream_put.hpp></code> provides the function template 1294<code>boost::io::ostream_put</code> for formatted output that satisfies the requirements 1295of [ostream.formatted.reqmts].</p> 1296</div> 1297</div> 1298<div class="sect2"> 1299<h3 id="example_3">Example</h3> 1300<div class="paragraph"> 1301<p>The inserter for class template <code>basic_string_view</code> could be implemented as 1302follows:</p> 1303</div> 1304<div class="listingblock"> 1305<div class="content"> 1306<pre class="highlight"><code class="language-cpp" data-lang="cpp">template<class charT, class traits> 1307std::basic_ostream<charT, traits>& 1308operator<<(std::basic_ostream<charT, traits>& os, 1309 const basic_string_view<charT, traits>& str) 1310{ 1311 return boost::io::ostream_put(os, str.data(), str.size()); 1312}</code></pre> 1313</div> 1314</div> 1315</div> 1316<div class="sect2"> 1317<h3 id="reference_2">Reference</h3> 1318<div class="sect3"> 1319<h4 id="header_synopsis_4">Header Synopsis</h4> 1320<div class="listingblock"> 1321<div class="content"> 1322<pre class="highlight"><code class="language-cpp" data-lang="cpp">namespace boost { 1323namespace io { 1324 1325template<class charT, class traits> 1326std::basic_ostream<charT, traits>& 1327ostream_put(std::basic_ostream<charT, traits>& os, 1328 const charT* data, std::size_t size); 1329 1330} // io 1331} // boost</code></pre> 1332</div> 1333</div> 1334</div> 1335<div class="sect3"> 1336<h4 id="free_functions_2">Free functions</h4> 1337<div class="listingblock"> 1338<div class="content"> 1339<pre class="highlight"><code class="language-cpp" data-lang="cpp">template<class charT, class traits> 1340std::basic_ostream<charT, traits>& 1341ostream_put(std::basic_ostream<charT, traits>& os, 1342 const charT* data, std::size_t size);</code></pre> 1343</div> 1344</div> 1345<div class="dlist specification"> 1346<dl> 1347<dt class="hdlist1">Effects</dt> 1348<dd> 1349<p>Behaves like a formatted inserter (as described in 1350[ostream.formatted.reqmts]) of <code>os</code>. Creates a character sequence <code>seq</code> of size 1351characters starting at <code>data</code>, each widened using <code>os.widen()</code> 1352([basic.ios.members]). Determines padding for <code>seq</code> as described in 1353[ostream.formatted.reqmts]. Inserts <code>seq</code> into <code>os</code>. Calls <code>width(0)</code>.</p> 1354</dd> 1355<dt class="hdlist1">Returns</dt> 1356<dd> 1357<p><code>os</code>.</p> 1358</dd> 1359</dl> 1360</div> 1361</div> 1362</div> 1363<div class="sect2"> 1364<h3 id="acknowledgments_2">Acknowledgments</h3> 1365<div class="paragraph"> 1366<p>Glen Fernandes updated the implementation of the <code>basic_string_ref</code> and 1367<code>basic_string_view</code> stream insertion operators to write directly to the 1368<code>basic_streambuf</code> and refactored that functionality into this common utility.</p> 1369</div> 1370</div> 1371</div> 1372</div> 1373<div class="sect1"> 1374<h2 id="copyright_and_license">Copyright and License</h2> 1375<div class="sectionbody"> 1376<div class="ulist"> 1377<ul> 1378<li> 1379<p>Copyright 2002 Daryle Walker</p> 1380</li> 1381<li> 1382<p>Copyright 2002, 2006, 2007, 2009, 2010 Beman Dawes</p> 1383</li> 1384<li> 1385<p>Copyright 2019 Glen Joseph Fernandes</p> 1386</li> 1387</ul> 1388</div> 1389<div class="paragraph"> 1390<p>Distributed under the 1391<a href="http://www.boost.org/LICENSE_1_0.txt">Boost Software License, Version 1.0</a>.</p> 1392</div> 1393</div> 1394</div> 1395</div> 1396<div id="footer"> 1397<div id="footer-text"> 1398Last updated 2020-08-11 14:56:17 UTC 1399</div> 1400</div> 1401<style> 1402.specification { 1403margin-left: 2em; 1404} 1405</style> 1406</body> 1407</html>