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<html><!-- #BeginTemplate "/Templates/tmpl.dwt" --><head><!-- #BeginEditable "doctitle" --> <title>PTypes: string</title><!-- #EndEditable --> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link rel="stylesheet" href="styles.css"></head><body bgcolor="#FFFFFF" leftmargin="40" marginwidth="40"><p><a href="../index.html"><img src="title-1.7.gif" width="213" height="34" alt="C++ Portable Types Library (PTypes) Version 1.7" border="0"></a> <hr noshade><!-- #BeginEditable "body" --> <p class="hpath"><a href="index.html">Top</a>: <a href="basic.html">Basic types</a>: string</p><ul><li> <h5><a href="string.constructors.html">Constructors/destructors</a></h5></li><li> <h5><a href="string.operators.html">Operators</a></h5></li><li> <h5><a href="string.typecasts.html">Typecasts</a></h5></li><li> <h5><a href="string.manipulation.html">Manipulation</a></h5></li></ul><p>The string class implements dynamically allocated reference-counted 8-bit character strings. String class is a mixture of L-type and null-terminated strings: it has both the length indicator and the terminating null-symbol. The length of a string is theoretically limited to <span class="lang">INT_MAX</span>, and practically is limited to the amount of virtual memory space available to the application. </p><p>A string object itself contains only a reference to the first character of the string buffer. A string object can be implicitly converted to a null-terminated string, either a variable or passed as an actual parameter, thus allowing to combine both PTypes strings and traditional C strings in your application. A string object converted to <span class="lang">char*</span> never returns <span class="lang">NULL</span> pointers: it guarantees to always point to some data, even if the string is zero-sized.</p><p>The reference counting mechanism works <b>transparently</b> (known also as copy-on-write) and <b>safely</b> with regard to multithreading. A user can manipulate string objects as if each object had its own copy of string data. Whenever you modify a string object the library safely detaches the buffer from all other string objects that may be using the same buffer and creates a unique copy so that changes won't affect the other "holders" of this string.</p><p><b>NOTE on multithreading</b>: the dynamic string objects themselves are NOT thread-safe. In other words, each thread can manipulate objects (variables) of type <span class="lang">string</span> only within their scope. However, it is safe to pass strings as (copy) parameters when, for example, sending a message to a concurrent thread through a message queue. When the recipient thread will try to modify the string, the shared data buffer will be safely detached.</p><p>The string class is declared in <span class="lang"><ptypes.h></span>.</p><p class="seealso">See also: <a href="string.constructors.html">Constructors/destructors</a>, <a href="string.operators.html">Operators</a>, <a href="string.typecasts.html">Typecasts</a>, <a href="string.manipulation.html">Manipulation</a></p><!-- #EndEditable --><hr size="1"><a href="../index.html" class="ns">PTypes home</a></body><!-- #EndTemplate --></html>?? 快捷鍵說明
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