📄 character_traits.html
字号:
<HTML><!-- -- Copyright (c) 1996-1999 -- Silicon Graphics Computer Systems, Inc. -- -- Permission to use, copy, modify, distribute and sell this software -- and its documentation for any purpose is hereby granted without fee, -- provided that the above copyright notice appears in all copies and -- that both that copyright notice and this permission notice appear -- in supporting documentation. Silicon Graphics makes no -- representations about the suitability of this software for any -- purpose. It is provided "as is" without express or implied warranty. -- -- Copyright (c) 1994 -- Hewlett-Packard Company -- -- Permission to use, copy, modify, distribute and sell this software -- and its documentation for any purpose is hereby granted without fee, -- provided that the above copyright notice appears in all copies and -- that both that copyright notice and this permission notice appear -- in supporting documentation. Hewlett-Packard Company makes no -- representations about the suitability of this software for any -- purpose. It is provided "as is" without express or implied warranty. -- --><Head><Title>Character Traits</Title><!-- Generated by htmldoc --></HEAD><BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b" ALINK="#ff0000"> <IMG SRC="CorpID.gif" ALT="SGI" HEIGHT="43" WIDTH="151"> <!--end header--><BR Clear><H1>Character Traits</H1><Table CellPadding=0 CellSpacing=0 width=100%><TR><TD Align=left><Img src = "utilities.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD><TD Align=right><Img src = "concept.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD></TR><TR><TD Align=left VAlign=top><b>Category</b>: utilities</TD><TD Align=right VAlign=top><b>Component type</b>: concept</TD></TR></Table><h3>Description</h3>Several library components, including <A href="basic_string.html">strings</A>, need to performoperations on characters. A Character Traits class is similar toa <A href="functors.html">function object</A>: it encapsulates some information about a particular character type, and some operations on that type. <P>Note that every member of a Character Traits class is static. There is never any need to create a Character Traits object, and, infact, there is no guarantee that creating such objects is possible.<h3>Refinement of</h3>Character Traits is not a refinement of any other concept.<h3>Associated types</h3><Table border><TR><TD VAlign=top>Value type</TD><TD VAlign=top><tt>X::char_type</tt></TD><TD VAlign=top>The character type described by this Character Traits type.</TD></TR><TR><TD VAlign=top>Int type</TD><TD VAlign=top><tt>X::int_type</tt></TD><TD VAlign=top>A type that is capable of representing every valid value of type <tt>char_type</tt>, and, additionally an end-of-file value. For <tt>char</tt>, for example, the int type may be <tt>int</tt>, and for <tt>wchar_t</tt> it may be <tt>wint_t</tt>.</TD></TR><TR><TD VAlign=top>Position type</TD><TD VAlign=top><tt>X::pos_type</tt></TD><TD VAlign=top>A type that can represent the position of a character of type <tt>char_type</tt> within a file. This type is usually <tt>streampos</tt>.</TD></TR><TR><TD VAlign=top>Offset type</TD><TD VAlign=top><tt>X::off_type</tt></TD><TD VAlign=top>An integer type that can represent the difference between two <tt>pos_type</tt> values. This type is usually <tt>streamoff</tt>.</TD></TR><TR><TD VAlign=top>State type</TD><TD VAlign=top><tt>X::state_type</tt></TD><TD VAlign=top>A type that can represent a state in a multibyte encoding scheme. This type, if used at all, is usually <tt>mbstate_t</tt>.</TD></tr></table><h3>Notation</h3><Table><TR><TD VAlign=top><tt>X</tt></TD><TD VAlign=top>A type that is a model of Character Traits.</TD></TR><TR><TD VAlign=top><tt>c</tt>, <tt>c1</tt>, <tt>c2</tt></TD><TD VAlign=top>A value of <tt>X</tt>'s value type, <tt>X::char_type</tt>.</TD></TR><TR><TD VAlign=top><tt>e</tt>, <tt>e1</tt>, <tt>e2</tt></TD><TD VAlign=top>A value of <tt>X</tt>'s int type, <tt>X::int_type</tt>.</TD></TR><TR><TD VAlign=top><tt>n</tt></TD><TD VAlign=top>A value of type <tt>size_t</tt>.</TD></TR><TR><TD VAlign=top><tt>p</tt>, <tt>p1</tt>, <tt>p2</tt></TD><TD VAlign=top>A non-null pointer of type <tt>const X::char_type*</tt>.</TD></TR><TR><TD VAlign=top><tt>s</tt></TD><TD VAlign=top>A non-null pointer of type <tt>X::char_type*</tt>.</TD></tr></table><h3>Valid Expressions</h3><Table border><TR><TH>Name</TH><TH>Expression</TH><TH>Type requirements</TH><TH>Return type</TH></TR><TR><TD VAlign=top>Character assignment</TD><TD VAlign=top><tt>X::assign(c1, c2)</tt></TD><TD VAlign=top><tt>c1</tt> is a modifiable lvalue.</TD><TD VAlign=top><tt>void</tt></TD></TR><TR><TD VAlign=top>Character equality</TD><TD VAlign=top><tt>X::eq(c1, c2)</tt></TD><TD VAlign=top> </TD><TD VAlign=top><tt>bool</tt></TD></TR><TR><TD VAlign=top>Character comparison</TD><TD VAlign=top><tt>X::lt(c1, c2)</tt></TD><TD VAlign=top> </TD><TD VAlign=top><tt>bool</tt></TD></TR><TR><TD VAlign=top>Range comparison</TD><TD VAlign=top><tt>X::compare(p1, p2, n)</tt></TD><TD VAlign=top> </TD><TD VAlign=top><tt>int</tt></TD></TR><TR><TD VAlign=top>Length</TD><TD VAlign=top><tt>X::length(p)</tt></TD><TD VAlign=top> </TD><TD VAlign=top><tt>size_t</tt></TD></TR><TR><TD VAlign=top>Find</TD><TD VAlign=top><tt>X::find(p, n, c)</tt></TD><TD VAlign=top> </TD><TD VAlign=top><tt>const X::char_type*</tt></TD></TR><TR><TD VAlign=top>Move</TD><TD VAlign=top><tt>X::move(s, p, n)</tt></TD><TD VAlign=top> </TD><TD VAlign=top><tt>X::char_type*</tt></TD></TR><TR><TD VAlign=top>Copy</TD><TD VAlign=top><tt>X::copy(s, p, n)</tt></TD><TD VAlign=top> </TD><TD VAlign=top><tt>X::char_type*</tt></TD></TR><TR><TD VAlign=top>Range assignment</TD><TD VAlign=top><tt>X::assign(s, n, c)</tt></TD><TD VAlign=top> </TD><TD VAlign=top><tt>X::char_type*</tt></TD></TR><TR><TD VAlign=top>EOF value</TD><TD VAlign=top><tt>X::eof()</tt></TD><TD VAlign=top> </TD><TD VAlign=top><tt>X::int_type</tt></TD></TR><TR><TD VAlign=top>Not EOF</TD><TD VAlign=top><tt>X::not_eof(e)</tt></TD><TD VAlign=top> </TD><TD VAlign=top><tt>X::int_type</tt></TD></TR><TR><TD VAlign=top>Convert to value type</TD><TD VAlign=top><tt>X::to_char_type(e)</tt></TD><TD VAlign=top> </TD><TD VAlign=top><tt>X::char_type</tt></TD></TR><TR><TD VAlign=top>Convert to int type</TD><TD VAlign=top><tt>X::to_int_type(c)</tt></TD><TD VAlign=top> </TD><TD VAlign=top><tt>X::int_type</tt></TD></TR><TR><TD VAlign=top>Equal int type values</TD><TD VAlign=top><tt>X::eq_int_type(e1, e2)</tt></TD><TD VAlign=top> </TD><TD VAlign=top><tt>bool</tt></TD></tr></table><h3>Expression semantics</h3><Table border><TR><TH>Name</TH><TH>Expression</TH><TH>Precondition</TH><TH>Semantics</TH><TH>Postcondition</TH></TR><TR><TD VAlign=top>Character assignment</TD><TD VAlign=top><tt>X::assign(c1, c2)</tt></TD><TD VAlign=top> </TD><TD VAlign=top>Performs the assignment <tt>c1 = c2</tt></TD><TD VAlign=top><tt>X::eq(c1, c2)</tt> is <tt>true</tt>.</TD></TR><TR><TD VAlign=top>Character equality</TD><TD VAlign=top><tt>X::eq(c1, c2)</tt></TD><TD VAlign=top> </TD><TD VAlign=top>Returns <tt>true</tt> if and only if <tt>c1</tt> and <tt>c2</tt> are equal.</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top>Character comparison</TD><TD VAlign=top><tt>X::lt(c1, c2)</tt></TD><TD VAlign=top> </TD><TD VAlign=top>Returns <tt>true</tt> if and only if <tt>c1</tt> is less than <tt>c2</tt>. Note that for any two value values <tt>c1</tt> and <tt>c2</tt>, exactly one of <tt>X::lt(c1, c2)</tt>, <tt>X::lt(c2, c1)</tt>, and <tt>X::eq(c1, c2)</tt> should be <tt>true</tt>.</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top>Range comparison</TD><TD VAlign=top><tt>X::compare(p1, p2, n)</tt></TD><TD VAlign=top><tt>[p1, p1+n)</tt> and <tt>[p2, p2+n)</tt> are valid ranges.</TD><TD VAlign=top>Generalization of <tt>strncmp</tt>. Returns <tt>0</tt> if every element in <tt>[p1, p1+n)</tt> is equal to the corresponding element in <tt>[p2, p2+n)</tt>, a negative value if there exists an element in <tt>[p1, p1+n)</tt> less than the corresponding element in <tt>[p2, p2+n)</tt> and all previous elements are equal, and a positive value if there exists an element in <tt>[p1, p1+n)</tt> greater than the corresponding element in <tt>[p2, p2+n)</tt> and all previous elements are equal.</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top>Length</TD><TD VAlign=top><tt>X::length(p)</tt></TD><TD VAlign=top> </TD><TD VAlign=top>Generalization of <tt>strlen</tt>. Returns the smallest non-negative number <tt>n</tt> such that <tt>X::eq(p+n, X::char_type())</tt> is true. Behavior is undefined if no such <tt>n</tt> exists.</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top>Find</TD><TD VAlign=top><tt>X::find(p, n, c)</tt></TD><TD VAlign=top><tt>[p, p+n)</tt> is a valid range.</TD><TD VAlign=top>Generalization of <tt>strchr</tt>. Returns the first pointer <tt>q</tt> in <tt>[p, p+n)</tt> such that <tt>X::eq(*q, c)</tt> is true. Returns a null pointer if no such pointer exists. (Note that this method for indicating a failed search differs from that is <tt><A href="find.html">find</A></tt>.)</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top>Move</TD><TD VAlign=top><tt>X::move(s, p, n)</tt></TD><TD VAlign=top><tt>[p, p+n)</tt> and <tt>[s, s+n)</tt> are valid ranges (possibly overlapping).</TD><TD VAlign=top>Generalization of <tt>memmove</tt>. Copies values from the range <tt>[p, p+n)</tt> to the range <tt>[s, s+n)</tt>, and returns <tt>s</tt>.</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top>Copy</TD><TD VAlign=top><tt>X::copy(s, p, n)</tt></TD><TD VAlign=top><tt>[p, p+n)</tt> and <tt>[s, s+n)</tt> are valid ranges which do not overlap.</TD><TD VAlign=top>Generalization of <tt>memcpy</tt>. Copies values from the range <tt>[p, p+n)</tt> to the range <tt>[s, s+n)</tt>, and returns <tt>s</tt>.</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top>Range assignment</TD><TD VAlign=top><tt>X::assign(s, n, c)</tt></TD><TD VAlign=top><tt>[s, s+n)</tt> is a valid range.</TD><TD VAlign=top>Generalization of <tt>memset</tt>. Assigns the value <tt>c</tt> to each pointer in the range <tt>[s, s+n)</tt>, and returns <tt>s</tt>.</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top>EOF value</TD><TD VAlign=top><tt>X::eof()</tt></TD><TD VAlign=top> </TD><TD VAlign=top>Returns a value that can represent EOF.</TD><TD VAlign=top><tt>X::eof()</tt> is distinct from every valid value of type <tt>X::char_type</tt>. That is, there exists no value <tt>c</tt> such that <tt>X::eq_int_type(X::to_int_type(c), X::eof())</tt> is <tt>true</tt>.</TD></TR><TR><TD VAlign=top>Not EOF</TD><TD VAlign=top><tt>X::not_eof(e)</tt></TD><TD VAlign=top> </TD><TD VAlign=top>Returns <tt>e</tt> if <tt>e</tt> represents a valid <tt>char_type</tt> value, and some non-EOF value if <tt>e</tt> is <tt>X::eof()</tt>.</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top>Convert to value type</TD><TD VAlign=top><tt>X::to_char_type(e)</tt></TD><TD VAlign=top> </TD><TD VAlign=top>Converts <tt>e</tt> to <tt>X</tt>'s int type. If <tt>e</tt> is a representation of some <tt>char_type</tt> value then it returns that value; if <tt>e</tt> is <tt>X::eof()</tt> then the return value is unspecified.</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top>Convert to int type</TD><TD VAlign=top><tt>X::to_int_type(c)</tt></TD><TD VAlign=top> </TD><TD VAlign=top>Converts <tt>c</tt> to <tt>X</tt>'s int type.</TD><TD VAlign=top><tt>X::to_char_type(X::to_int_type(c))</tt> is a null operation.</TD></TR><TR><TD VAlign=top>Equal int type values</TD><TD VAlign=top><tt>X::eq_int_type(e1, e2)</tt></TD><TD VAlign=top> </TD><TD VAlign=top>Compares two int type values. If there exist values of type <tt>X::char_type</tt> such that <tt>e1</tt> is <tt>X::to_int_type(c1))</tt> and <tt>e2</tt> is <tt>X::to_int_type(c2))</tt>, then <tt>X::eq_int_type(e1, e2)</tt> is the same as <tt>X::eq(c1, c2)</tt>. Otherwise, <tt>eq_int_type</tt> returns <tt>true</tt> if <tt>e1</tt> and <tt>e2</tt> are both EOF and <tt>false</tt> if one of <tt>e1</tt> and <tt>e2</tt> is EOF and the other is not.</TD><TD VAlign=top> </TD></tr></table><h3>Complexity guarantees</h3><tt>length</tt>, <tt>find</tt>, <tt>move</tt>, <tt>copy</tt>, and the range version of <tt>assign</tt>are linear in <tt>n</tt>.<P>All other operations are constant time.<h3>Models</h3><UL><LI><tt><A href="char_traits.html">char_traits</A><char></tt><LI><tt><A href="char_traits.html">char_traits</A><wchar_t></tt></UL><h3>Notes</h3><h3>See also</h3><tt><A href="basic_string.html">string</A></tt><!--start footer--> <HR SIZE="6"><A href="http://www.sgi.com/"><IMG SRC="surf.gif" HEIGHT="54" WIDTH="54" ALT="[Silicon Surf]"></A><A HREF="index.html"><IMG SRC="stl_home.gif" HEIGHT="54" WIDTH="54" ALT="[STL Home]"></A><BR><FONT SIZE="-2"><A href="http://www.sgi.com/Misc/sgi_info.html" TARGET="_top">Copyright © 1999 Silicon Graphics, Inc.</A> All Rights Reserved.</FONT><FONT SIZE="-3"><a href="http://www.sgi.com/Misc/external.list.html" TARGET="_top">TrademarkInformation</A></FONT><P></BODY></HTML> ⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -