Progress towards a word-wrap stream helper.

word_wrap.cpp

@@ -6,6 +6,8 @@ static_assert( __cplusplus > 2020 );
 
 #include <tuple>
 #include <iostream>
+#include <iterator>
+#include <sstream>
 
 #include "evaluation_helpers.h"
 
@@ -15,7 +17,7 @@ namespace Alepha::Cavorite  ::detail::  word_wrap
 	{
 		// Returns the number of chars in the line just written to.
 		std::size_t
-		applyWordToLine( const std::size_t maximumWidth, const std::size_t nextLineOffset, const std::size_t currentLineWidth, std::string &&word, std::string &result )
+		applyWordToLine( const std::size_t maximumWidth, const std::size_t nextLineOffset, const std::size_t currentLineWidth, std::string &&word, std::ostream &result )
 		{
 			if( word.empty() ) return currentLineWidth;
 
@@ -23,25 +25,67 @@ namespace Alepha::Cavorite  ::detail::  word_wrap
 			{
 				if( currentLineWidth + word.size() > maximumWidth )
 				{
-					result+= '\n';
+					result << "\n";
-					std::fill_n( back_inserter( result ), nextLineOffset, ' ' );
+					std::fill_n( std::ostream_iterator< char >( result ), nextLineOffset, ' ' );
 					return nextLineOffset;
 				}
 				else return currentLineWidth;
 			};
 
 			const auto rv= lineWidth + word.size();
-			result+= std::move( word );
+			result << std::move( word );
 			return rv;
 		}
 	}
 
+	void
+	WordWrapStreambuf::writeChar( const char ch )
+	{
+		std::ostream outWrap{ underlying };
+		if( ch == '\n' )
+		{
+			const auto prev= currentLineLength;
+			const auto size= currentWord.size();
+			currentLineLength= applyWordToLine( maximumWidth, nextLineOffset, currentLineLength, std::move( currentWord ), outWrap );
+			currentWord.clear();
+			outWrap << '\n';
+			if( currentLineLength == prev + size )
+			{
+				std::fill_n( std::ostream_iterator< char >{ outWrap }, nextLineOffset, ' ' );
+				currentLineLength= nextLineOffset;
+			}
+			else currentLineLength= 0;
+		}
+		else if( ch == ' ' )
+		{
+			currentLineLength= applyWordToLine( maximumWidth, nextLineOffset, currentLineLength, std::move( currentWord ), outWrap );
+			currentWord.clear();
+			if( currentLineLength < maximumWidth )
+			{
+				outWrap << ' ';
+				++currentLineLength;
+			}
+		}
+		else currentWord+= ch;
+	}
+
+	void
+	WordWrapStreambuf::drain()
+	{
+		if( currentWord.empty() ) return;
+		std::ostream outWrap{ underlying };
+		applyWordToLine( maximumWidth, nextLineOffset, currentLineLength, std::move( currentWord ), outWrap );
+	}
+
 	std::string
 	exports::wordWrap( const std::string &text, const std::size_t width, const std::size_t nextLineOffset )
 	{
+		#if NEVER
 		auto putWord= [width, nextLineOffset]( std::string &&word, std::string &line, const std::size_t lineLength )
 		{
-			const auto rv= applyWordToLine( width, nextLineOffset, lineLength, std::move( word ), line );
+			std::ostringstream out;
+			const auto rv= applyWordToLine( width, nextLineOffset, lineLength, std::move( word ), out );
+			line+= std::move( out ).str();
 			return rv;
 		};
 
@@ -78,5 +122,20 @@ namespace Alepha::Cavorite  ::detail::  word_wrap
 		}
 		if( not word.empty() ) std::ignore= putWord( std::move( word ), result, lineLength );
 		return result;
+		#else
+		std::ostringstream oss;
+
+		WordWrapStreambuf buf;
+		buf.maximumWidth= width;
+		buf.nextLineOffset= nextLineOffset;
+		buf.underlying= static_cast< std::ostream & >( oss ).rdbuf();
+		static_cast< std::ostream & >( oss ).rdbuf( &buf );
+
+		oss << text;
+		buf.drain();
+
+		auto rv= std::move( oss ).str();
+		return rv;
+		#endif
 	}
 }

word_wrap.h

@@ -5,13 +5,50 @@ static_assert( __cplusplus > 2020'00 );
 #include <cstddef>
 
 #include <string>
+#include <streambuf>
 
 namespace Alepha::inline Cavorite  ::detail::  word_wrap
 {
 	inline namespace exports
 	{
 		std::string wordWrap( const std::string &text, std::size_t width, std::size_t nextLineOffset= 0 );
+
+		class WordWrapStreambuf;
 	}
+
+	class exports::WordWrapStreambuf
+		: public std::streambuf
+	{
+		public:
+			std::streambuf *underlying= nullptr;
+
+			std::size_t maximumWidth= 0;
+			std::size_t nextLineOffset= 0;
+			std::size_t currentLineLength= 0;
+
+			std::string currentWord;
+
+			void writeChar( const char ch );
+
+			void drain();
+
+		public:
+			int
+			overflow( const int ch ) override
+			{
+				if( ch == EOF ) throw std::logic_error( "EOF!" );
+				writeChar( ch );
+
+				return 1;
+			}
+
+			std::streamsize
+			xsputn( const char *const data, const std::streamsize amt ) override
+			{
+				for( std::streamsize i= 0; i< amt; ++i ) overflow( data[ i ] );
+				return amt;
+			}
+	};
 }
 
 namespace Alepha::Cavorite::inline exports::inline word_wrap

word_wrap.test/0.cc

@@ -91,19 +91,19 @@ static auto init= Alepha::Utility::enroll <=[]
 		},
 		{ "wider terminal, complex text: Hamlet's \"To Be or Not To Be\"",
 			{
-			"To be, or not to be: "
+				"To be, or not to be: "
-			"that is the question: "
+				"that is the question: "
-			"Whether 'tis nobler in the mind to suffer "
+				"Whether 'tis nobler in the mind to suffer "
-			"The slings and arrows of outrageous fortune, "
+				"The slings and arrows of outrageous fortune, "
-			"Or to take arms against a sea of troubles, "
+				"Or to take arms against a sea of troubles, "
-			"And by opposing end them?  "
+				"And by opposing end them?  "
-			"To die: to sleep; "
+				"To die: to sleep; "
-			"No more; and by a sleep to say we end "
+				"No more; and by a sleep to say we end "
-			"The heart-ache and the thousand natural shocks "
+				"The heart-ache and the thousand natural shocks "
-			"That flesh is heir to, 'tis a consummation "
+				"That flesh is heir to, 'tis a consummation "
-			"Devoutly to be wish'd.  To die, to sleep; "
+				"Devoutly to be wish'd.  To die, to sleep; "
-			"To sleep: perchance to dream: ay, there's the rub;",
+				"To sleep: perchance to dream: ay, there's the rub;",
-			80, 0
+				80, 0
 			},
 			"To be, or not to be: that is the question: Whether 'tis nobler in the mind to \n"
 			"suffer The slings and arrows of outrageous fortune, Or to take arms against a \n"