105 lines
4.8 KiB
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105 lines
4.8 KiB
HTML
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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<title>Bytevector Slices (Guile Reference Manual)</title>
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<div class="subsubsection-level-extent" id="Bytevector-Slices">
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Previous: <a href="Bytevector-Procedures-in-R7RS.html" accesskey="p" rel="prev">Bytevector Procedures in R7RS</a>, Up: <a href="Bytevectors.html" accesskey="u" rel="up">Bytevectors</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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<h4 class="subsubsection" id="Bytevector-Slices-1"><span>6.6.12.10 Bytevector Slices<a class="copiable-link" href="#Bytevector-Slices-1"> ¶</a></span></h4>
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<a class="index-entry-id" id="index-subset_002c-of-a-bytevector"></a>
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<a class="index-entry-id" id="index-slice_002c-of-a-bytevector"></a>
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<a class="index-entry-id" id="index-slice_002c-of-a-uniform-vector"></a>
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<p>As an extension to the R6RS specification, the <code class="code">(rnrs bytevectors
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gnu)</code> module provides the <code class="code">bytevector-slice</code> procedure, which
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returns a bytevector aliasing part of an existing bytevector.
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</p>
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<dl class="first-deffn">
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<dt class="deffn" id="index-bytevector_002dslice"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">bytevector-slice</strong> <var class="def-var-arguments"><var class="var">bv</var> <var class="var">offset</var> [<var class="var">size</var>]</var><a class="copiable-link" href="#index-bytevector_002dslice"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fbytevector_005fslice"><span class="category-def">C Function: </span><span><strong class="def-name">scm_bytevector_slice</strong> <var class="def-var-arguments">(<var class="var">bv</var>, <var class="var">offset</var>, <var class="var">size</var>)</var><a class="copiable-link" href="#index-scm_005fbytevector_005fslice"> ¶</a></span></dt>
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<dd><p>Return the slice of <var class="var">bv</var> starting at <var class="var">offset</var> and counting
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<var class="var">size</var> bytes. When <var class="var">size</var> is omitted, the slice covers all
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of <var class="var">bv</var> starting from <var class="var">offset</var>. The returned slice shares
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storage with <var class="var">bv</var>: changes to the slice are visible in <var class="var">bv</var>
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and vice-versa.
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</p>
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<p>When <var class="var">bv</var> is actually a SRFI-4 uniform vector, its element
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type is preserved unless <var class="var">offset</var> and <var class="var">size</var> are not aligned
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on its element type size.
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</p></dd></dl>
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<p>Here is an example showing how to use it:
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(use-modules (rnrs bytevectors)
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(rnrs bytevectors gnu))
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(define bv (u8-list->bytevector (iota 10)))
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(define slice (bytevector-slice bv 2 3))
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slice
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⇒ #vu8(2 3 4)
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(bytevector-u8-set! slice 0 77)
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slice
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⇒ #vu8(77 3 4)
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bv
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⇒ #vu8(0 1 77 3 4 5 6 7 8 9)
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</pre></div>
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