diff options
| author | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
|---|---|---|
| committer | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
| commit | abdaadbcae30fe0c9a66c7516798279fdfd97750 (patch) | |
| tree | 00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/gcc/Fast-enumeration-protocol.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
Change-Id: I7303388733328cd98ab9aa3c30236db67f2e9e9c
Diffstat (limited to 'share/doc/gcc/Fast-enumeration-protocol.html')
| -rw-r--r-- | share/doc/gcc/Fast-enumeration-protocol.html | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/share/doc/gcc/Fast-enumeration-protocol.html b/share/doc/gcc/Fast-enumeration-protocol.html new file mode 100644 index 0000000..abc6e12 --- /dev/null +++ b/share/doc/gcc/Fast-enumeration-protocol.html @@ -0,0 +1,157 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- This file documents the use of the GNU compilers. + +Copyright (C) 1988-2023 Free Software Foundation, Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with the +Invariant Sections being "Funding Free Software", the Front-Cover +Texts being (a) (see below), and with the Back-Cover Texts being (b) +(see below). A copy of the license is included in the section entitled +"GNU Free Documentation License". + +(a) The FSF's Front-Cover Text is: + +A GNU Manual + +(b) The FSF's Back-Cover Text is: + +You have freedom to copy and modify this GNU Manual, like GNU + software. Copies published by the Free Software Foundation raise + funds for GNU development. --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>Using the GNU Compiler Collection (GCC): Fast enumeration protocol</title> + +<meta name="description" content="Using the GNU Compiler Collection (GCC): Fast enumeration protocol"> +<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Fast enumeration protocol"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Indices.html#Indices" rel="index" title="Indices"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Fast-enumeration.html#Fast-enumeration" rel="up" title="Fast enumeration"> +<link href="Messaging-with-the-GNU-Objective_002dC-runtime.html#Messaging-with-the-GNU-Objective_002dC-runtime" rel="next" title="Messaging with the GNU Objective-C runtime"> +<link href="Fast-enumeration-details.html#Fast-enumeration-details" rel="previous" title="Fast enumeration details"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +div.smalllisp {margin-left: 3.2em} +kbd {font-style:oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en_US" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Fast-enumeration-protocol"></a> +<div class="header"> +<p> +Previous: <a href="Fast-enumeration-details.html#Fast-enumeration-details" accesskey="p" rel="previous">Fast enumeration details</a>, Up: <a href="Fast-enumeration.html#Fast-enumeration" accesskey="u" rel="up">Fast enumeration</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Fast-Enumeration-Protocol"></a> +<h4 class="subsection">8.9.4 Fast Enumeration Protocol</h4> + +<p>If you want your own collection object to be usable with fast +enumeration, you need to have it implement the method +</p> +<div class="smallexample"> +<pre class="smallexample">- (unsigned long) countByEnumeratingWithState: (NSFastEnumerationState *)state + objects: (id *)objects + count: (unsigned long)len; +</pre></div> + +<p>where <code>NSFastEnumerationState</code> must be defined in your code as follows: +</p> +<div class="smallexample"> +<pre class="smallexample">typedef struct +{ + unsigned long state; + id *itemsPtr; + unsigned long *mutationsPtr; + unsigned long extra[5]; +} NSFastEnumerationState; +</pre></div> + +<p>If no <code>NSFastEnumerationState</code> is defined in your code, the +compiler will automatically replace <code>NSFastEnumerationState *</code> +with <code>struct __objcFastEnumerationState *</code>, where that type is +silently defined by the compiler in an identical way. This can be +confusing and we recommend that you define +<code>NSFastEnumerationState</code> (as shown above) instead. +</p> +<p>The method is called repeatedly during a fast enumeration to retrieve +batches of objects. Each invocation of the method should retrieve the +next batch of objects. +</p> +<p>The return value of the method is the number of objects in the current +batch; this should not exceed <code>len</code>, which is the maximum size of +a batch as requested by the caller. The batch itself is returned in +the <code>itemsPtr</code> field of the <code>NSFastEnumerationState</code> struct. +</p> +<p>To help with returning the objects, the <code>objects</code> array is a C +array preallocated by the caller (on the stack) of size <code>len</code>. +In many cases you can put the objects you want to return in that +<code>objects</code> array, then do <code>itemsPtr = objects</code>. But you +don’t have to; if your collection already has the objects to return in +some form of C array, it could return them from there instead. +</p> +<p>The <code>state</code> and <code>extra</code> fields of the +<code>NSFastEnumerationState</code> structure allows your collection object +to keep track of the state of the enumeration. In a simple array +implementation, <code>state</code> may keep track of the index of the last +object that was returned, and <code>extra</code> may be unused. +</p> +<p>The <code>mutationsPtr</code> field of the <code>NSFastEnumerationState</code> is +used to keep track of mutations. It should point to a number; before +working on each object, the fast enumeration loop will check that this +number has not changed. If it has, a mutation has happened and the +fast enumeration will abort. So, <code>mutationsPtr</code> could be set to +point to some sort of version number of your collection, which is +increased by one every time there is a change (for example when an +object is added or removed). Or, if you are content with less strict +mutation checks, it could point to the number of objects in your +collection or some other value that can be checked to perform an +approximate check that the collection has not been mutated. +</p> +<p>Finally, note how we declared the <code>len</code> argument and the return +value to be of type <code>unsigned long</code>. They could also be declared +to be of type <code>unsigned int</code> and everything would still work. +</p> +<hr> +<div class="header"> +<p> +Previous: <a href="Fast-enumeration-details.html#Fast-enumeration-details" accesskey="p" rel="previous">Fast enumeration details</a>, Up: <a href="Fast-enumeration.html#Fast-enumeration" accesskey="u" rel="up">Fast enumeration</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |