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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><HTML><HEAD> <META NAME="GENERATOR" CONTENT="LinuxDoc-Tools 0.9.21"> <TITLE>libapr(apache portable runtime) programming tutorial: character string handling</TITLE> <LINK HREF="apr-tutorial-9.html" REL=next> <LINK HREF="apr-tutorial-7.html" REL=previous> <LINK HREF="apr-tutorial.html#toc8" REL=contents></HEAD><BODY><A HREF="apr-tutorial-9.html">Next</A><A HREF="apr-tutorial-7.html">Previous</A><A HREF="apr-tutorial.html#toc8">Contents</A><HR><H2><A NAME="s8">8.</A> <A HREF="apr-tutorial.html#toc8">character string handling</A></H2><P>I assume you are familiar with C language's string APIs, such as strlen(3) and strcpy(3).libapr provides some string APIs. They are almost same as the common(ANSI C) APIs. Why does libapr provide a yet another string APIs? The benefit of libapr's string APIs is related to memory pool. In a common C string handling, we have to write much memory management code. The following code is an example.</P><P><BLOCKQUOTE><CODE><PRE>/* ANSI C string example (a bit naive code) *//* we concatenate three strings, s1, s2, s3 */int len1 = strlen(s1);int len2 = strlen(s2);int len3 = strlen(s3);int total_len = len1 + len2 + len3;char *cat_str = malloc(total_len + 1);strcpy(cat_str, s1);strcat(cat_str, s2);strcat(cat_str, s3);/* later, we have to free the allocated memory */free(cat_str);</PRE></CODE></BLOCKQUOTE></P><P>The same thing is written with libapr as follows:</P><P><BLOCKQUOTE><CODE><PRE>/* pseudo code about libapr string APIs */apr_pool_t *mp;apr_pool_create(&mp, NULL);/* apr_pstrcat() takes care of both memory allocation and string concatenation. * If the concatenated string is read-only, we should use 'const char*' type. */const char *cat_str = apr_pstrcat(mp, s1, s2, s3, NULL);/* later, all we have to do is to destroy the memory pool to free all the memory */apr_pool_destroy(mp);</PRE></CODE></BLOCKQUOTE></P><P>Like apr_pstrcat(), apr_psprintf() allows you to write much simpler code. You can find other string APIs in apr_strings.h.</P><HR><A HREF="apr-tutorial-9.html">Next</A><A HREF="apr-tutorial-7.html">Previous</A><A HREF="apr-tutorial.html#toc8">Contents</A></BODY></HTML>?? 快捷鍵說明
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