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321 lines
9.4 KiB
321 lines
9.4 KiB
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<title>rand - The Go Programming Language</title>
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...
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<div class="top-heading" id="heading-wide"><a href="http://localhost:6060/">The Go Programming Language</a></div>
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<h1>Package rand</h1>
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<div id="nav"></div>
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<!--
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Copyright 2009 The Go Authors. All rights reserved.
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Use of this source code is governed by a BSD-style
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license that can be found in the LICENSE file.
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Note: Static (i.e., not template-generated) href and id
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</script>
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<div id="short-nav">
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<dl>
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<dd><code>import "crypto/rand"</code></dd>
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</dl>
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<dl>
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<dd><a href="index.html#pkg-overview" class="overviewLink">Overview</a></dd>
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<dd><a href="index.html#pkg-index" class="indexLink">Index</a></dd>
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<dd><a href="index.html#pkg-examples" class="examplesLink">Examples</a></dd>
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</dl>
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<!-- The package's Name is printed as title by the top-level template -->
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<div id="pkg-overview" class="toggleVisible">
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<h2 class="toggleButton" title="Click to show Overview section">Overview ▹</h2>
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</div>
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<div class="expanded">
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<h2 class="toggleButton" title="Click to hide Overview section">Overview ▾</h2>
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<p>
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Package rand implements a cryptographically secure
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pseudorandom number generator.
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</p>
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</div>
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</div>
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<div id="pkg-index" class="toggleVisible">
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<h2 class="toggleButton" title="Click to show Index section">Index ▹</h2>
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<div class="expanded">
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<h2 class="toggleButton" title="Click to hide Index section">Index ▾</h2>
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<!-- Table of contents for API; must be named manual-nav to turn off auto nav. -->
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<div id="manual-nav">
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<dl>
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<dd><a href="index.html#pkg-variables">Variables</a></dd>
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<dd><a href="index.html#Int">func Int(rand io.Reader, max *big.Int) (n *big.Int, err error)</a></dd>
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<dd><a href="index.html#Prime">func Prime(rand io.Reader, bits int) (p *big.Int, err error)</a></dd>
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<dd><a href="index.html#Read">func Read(b []byte) (n int, err error)</a></dd>
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</dl>
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</div><!-- #manual-nav -->
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<div id="pkg-examples">
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<h4>Examples</h4>
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<dl>
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<dd><a class="exampleLink" href="index.html#example_Read">Read</a></dd>
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</dl>
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</div>
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<h4>Package files</h4>
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<p>
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<span style="font-size:90%">
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<a href="http://localhost:6060/src/crypto/rand/eagain.go">eagain.go</a>
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<a href="http://localhost:6060/src/crypto/rand/rand.go">rand.go</a>
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<a href="http://localhost:6060/src/crypto/rand/rand_linux.go">rand_linux.go</a>
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<a href="http://localhost:6060/src/crypto/rand/rand_unix.go">rand_unix.go</a>
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<a href="http://localhost:6060/src/crypto/rand/util.go">util.go</a>
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</span>
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</p>
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</div><!-- .expanded -->
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</div><!-- #pkg-index -->
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<div id="pkg-callgraph" class="toggle" style="display: none">
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<div class="collapsed">
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<h2 class="toggleButton" title="Click to show Internal Call Graph section">Internal call graph ▹</h2>
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</div> <!-- .expanded -->
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<div class="expanded">
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<h2 class="toggleButton" title="Click to hide Internal Call Graph section">Internal call graph ▾</h2>
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<p>
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In the call graph viewer below, each node
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is a function belonging to this package
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and its children are the functions it
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calls—perhaps dynamically.
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</p>
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<p>
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The root nodes are the entry points of the
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package: functions that may be called from
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outside the package.
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There may be non-exported or anonymous
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functions among them if they are called
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dynamically from another package.
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</p>
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<p>
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Click a node to visit that function's source code.
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From there you can visit its callers by
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clicking its declaring <code>func</code>
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token.
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</p>
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<p>
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Functions may be omitted if they were
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determined to be unreachable in the
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particular programs or tests that were
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analyzed.
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</p>
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<!-- Zero means show all package entry points. -->
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<ul style="margin-left: 0.5in" id="callgraph-0" class="treeview"></ul>
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</div>
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</div> <!-- #pkg-callgraph -->
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<h2 id="pkg-variables">Variables</h2>
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<pre>var <span id="Reader">Reader</span> <a href="../../io/index.html">io</a>.<a href="../../io/index.html#Reader">Reader</a></pre>
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<p>
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Reader is a global, shared instance of a cryptographically
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strong pseudo-random generator.
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</p>
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<p>
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On Unix-like systems, Reader reads from /dev/urandom.
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On Linux, Reader uses getrandom(2) if available, /dev/urandom otherwise.
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On Windows systems, Reader uses the CryptGenRandom API.
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</p>
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<h2 id="Int">func <a href="http://localhost:6060/src/crypto/rand/util.go?s=3072:3134#L96">Int</a></h2>
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<pre>func Int(rand <a href="../../io/index.html">io</a>.<a href="../../io/index.html#Reader">Reader</a>, max *<a href="../../math/big/index.html">big</a>.<a href="../../math/big/index.html#Int">Int</a>) (n *<a href="../../math/big/index.html">big</a>.<a href="../../math/big/index.html#Int">Int</a>, err <a href="../../builtin/index.html#error">error</a>)</pre>
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<p>
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Int returns a uniform random value in [0, max). It panics if max <= 0.
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</p>
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<h2 id="Prime">func <a href="http://localhost:6060/src/crypto/rand/util.go?s=1126:1186#L21">Prime</a></h2>
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<pre>func Prime(rand <a href="../../io/index.html">io</a>.<a href="../../io/index.html#Reader">Reader</a>, bits <a href="../../builtin/index.html#int">int</a>) (p *<a href="../../math/big/index.html">big</a>.<a href="../../math/big/index.html#Int">Int</a>, err <a href="../../builtin/index.html#error">error</a>)</pre>
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<p>
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Prime returns a number, p, of the given size, such that p is prime
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with high probability.
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Prime will return error for any error returned by rand.Read or if bits < 2.
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</p>
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<h2 id="Read">func <a href="http://localhost:6060/src/crypto/rand/rand.go?s=714:752#L11">Read</a></h2>
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<pre>func Read(b []<a href="../../builtin/index.html#byte">byte</a>) (n <a href="../../builtin/index.html#int">int</a>, err <a href="../../builtin/index.html#error">error</a>)</pre>
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<p>
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Read is a helper function that calls Reader.Read using io.ReadFull.
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On return, n == len(b) if and only if err == nil.
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</p>
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<div id="example_Read" class="toggle">
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<div class="collapsed">
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<p class="exampleHeading toggleButton">▹ <span class="text">Example</span></p>
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</div>
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<div class="expanded">
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<p class="exampleHeading toggleButton">▾ <span class="text">Example</span></p>
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<p>This example reads 10 cryptographically secure pseudorandom numbers from
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rand.Reader and writes them to a byte slice.
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</p>
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<p>Code:</p>
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<pre class="code">c := 10
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b := make([]byte, c)
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_, err := rand.Read(b)
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if err != nil {
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fmt.Println("error:", err)
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return
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}
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<span class="comment">// The slice should now contain random bytes instead of only zeroes.</span>
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fmt.Println(bytes.Equal(b, make([]byte, c)))
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<span class="comment"></pre>
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<p>Output:</p>
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<pre class="output">false
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</pre>
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</div>
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</div>
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the content of this page is licensed under the
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Creative Commons Attribution 3.0 License,
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