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<title>Bytevector Manipulation (Guile Reference Manual)</title>
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<div class="subsubsection-level-extent" id="Bytevector-Manipulation">
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Next: <a href="Bytevectors-as-Integers.html" accesskey="n" rel="next">Interpreting Bytevector Contents as Integers</a>, Previous: <a href="Bytevector-Endianness.html" accesskey="p" rel="prev">Endianness</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="Manipulating-Bytevectors"><span>6.6.12.2 Manipulating Bytevectors<a class="copiable-link" href="#Manipulating-Bytevectors"> ¶</a></span></h4>
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<p>Bytevectors can be created, copied, and analyzed with the following
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procedures and C functions.
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</p>
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<a class="anchor" id="x_002dmake_002dbytevector"></a><dl class="first-deffn">
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<dt class="deffn" id="index-make_002dbytevector"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">make-bytevector</strong> <var class="def-var-arguments">len [fill]</var><a class="copiable-link" href="#index-make_002dbytevector"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fmake_005fbytevector"><span class="category-def">C Function: </span><span><strong class="def-name">scm_make_bytevector</strong> <var class="def-var-arguments">(len, fill)</var><a class="copiable-link" href="#index-scm_005fmake_005fbytevector"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fc_005fmake_005fbytevector"><span class="category-def">C Function: </span><span><strong class="def-name">scm_c_make_bytevector</strong> <var class="def-var-arguments">(size_t len)</var><a class="copiable-link" href="#index-scm_005fc_005fmake_005fbytevector"> ¶</a></span></dt>
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<dd><p>Return a new bytevector of <var class="var">len</var> bytes. Optionally, if <var class="var">fill</var>
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is given, fill it with <var class="var">fill</var>; <var class="var">fill</var> must be in the range
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[-128,255].
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</p></dd></dl>
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<a class="anchor" id="x_002dbytevector_003f"></a><dl class="first-deffn">
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<dt class="deffn" id="index-bytevector_003f"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">bytevector?</strong> <var class="def-var-arguments">obj</var><a class="copiable-link" href="#index-bytevector_003f"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fbytevector_005fp"><span class="category-def">C Function: </span><span><strong class="def-name">scm_bytevector_p</strong> <var class="def-var-arguments">(obj)</var><a class="copiable-link" href="#index-scm_005fbytevector_005fp"> ¶</a></span></dt>
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<dd><p>Return true if <var class="var">obj</var> is a bytevector.
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</p></dd></dl>
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<dl class="first-deftypefn">
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<dt class="deftypefn" id="index-scm_005fis_005fbytevector"><span class="category-def">C Function: </span><span><code class="def-type">int</code> <strong class="def-name">scm_is_bytevector</strong> <code class="def-code-arguments">(SCM obj)</code><a class="copiable-link" href="#index-scm_005fis_005fbytevector"> ¶</a></span></dt>
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<dd><p>Equivalent to <code class="code">scm_is_true (scm_bytevector_p (obj))</code>.
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</p></dd></dl>
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<a class="anchor" id="x_002dbytevector_002dlength"></a><dl class="first-deffn">
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<dt class="deffn" id="index-bytevector_002dlength"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">bytevector-length</strong> <var class="def-var-arguments">bv</var><a class="copiable-link" href="#index-bytevector_002dlength"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fbytevector_005flength"><span class="category-def">C Function: </span><span><strong class="def-name">scm_bytevector_length</strong> <var class="def-var-arguments">(bv)</var><a class="copiable-link" href="#index-scm_005fbytevector_005flength"> ¶</a></span></dt>
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<dd><p>Return the length in bytes of bytevector <var class="var">bv</var>.
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</p></dd></dl>
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<dl class="first-deftypefn">
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<dt class="deftypefn" id="index-scm_005fc_005fbytevector_005flength"><span class="category-def">C Function: </span><span><code class="def-type">size_t</code> <strong class="def-name">scm_c_bytevector_length</strong> <code class="def-code-arguments">(SCM bv)</code><a class="copiable-link" href="#index-scm_005fc_005fbytevector_005flength"> ¶</a></span></dt>
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<dd><p>Likewise, return the length in bytes of bytevector <var class="var">bv</var>.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-bytevector_003d_003f"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">bytevector=?</strong> <var class="def-var-arguments">bv1 bv2</var><a class="copiable-link" href="#index-bytevector_003d_003f"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fbytevector_005feq_005fp"><span class="category-def">C Function: </span><span><strong class="def-name">scm_bytevector_eq_p</strong> <var class="def-var-arguments">(bv1, bv2)</var><a class="copiable-link" href="#index-scm_005fbytevector_005feq_005fp"> ¶</a></span></dt>
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<dd><p>Return <code class="code">#t</code> if <var class="var">bv1</var> equals <var class="var">bv2</var>—i.e., if they have the same
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length and contents.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-bytevector_002dfill_0021"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">bytevector-fill!</strong> <var class="def-var-arguments">bv fill [start [end]]</var><a class="copiable-link" href="#index-bytevector_002dfill_0021"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fbytevector_005ffill_005fx"><span class="category-def">C Function: </span><span><strong class="def-name">scm_bytevector_fill_x</strong> <var class="def-var-arguments">(bv, fill)</var><a class="copiable-link" href="#index-scm_005fbytevector_005ffill_005fx"> ¶</a></span></dt>
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<dd><p>Fill positions [<var class="var">start</var> ... <var class="var">end</var>) of bytevector <var class="var">bv</var> with
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byte <var class="var">fill</var>. <var class="var">start</var> defaults to 0 and <var class="var">end</var> defaults to the
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length of <var class="var">bv</var>.<a class="footnote" id="DOCF11" href="#FOOT11"><sup>11</sup></a>
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</p></dd></dl>
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<a class="anchor" id="x_002dr6_003abytevector_002dcopy_0021"></a><dl class="first-deffn">
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<dt class="deffn" id="index-bytevector_002dcopy_0021"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">bytevector-copy!</strong> <var class="def-var-arguments">source source-start target target-start len</var><a class="copiable-link" href="#index-bytevector_002dcopy_0021"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fbytevector_005fcopy_005fx"><span class="category-def">C Function: </span><span><strong class="def-name">scm_bytevector_copy_x</strong> <var class="def-var-arguments">(source, source_start, target, target_start, len)</var><a class="copiable-link" href="#index-scm_005fbytevector_005fcopy_005fx"> ¶</a></span></dt>
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<dd><p>Copy <var class="var">len</var> bytes from <var class="var">source</var> into <var class="var">target</var>, starting
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reading from <var class="var">source-start</var> (an index index within <var class="var">source</var>)
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and writing at <var class="var">target-start</var>.
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</p>
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<p>It is permitted for the <var class="var">source</var> and <var class="var">target</var> regions to
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overlap. In that case, copying takes place as if the source is first
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copied into a temporary bytevector and then into the destination.
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</p></dd></dl>
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<a class="anchor" id="x_002dr6_003abytevector_002dcopy"></a><dl class="first-deffn">
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<dt class="deffn" id="index-bytevector_002dcopy"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">bytevector-copy</strong> <var class="def-var-arguments">bv</var><a class="copiable-link" href="#index-bytevector_002dcopy"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fbytevector_005fcopy"><span class="category-def">C Function: </span><span><strong class="def-name">scm_bytevector_copy</strong> <var class="def-var-arguments">(bv)</var><a class="copiable-link" href="#index-scm_005fbytevector_005fcopy"> ¶</a></span></dt>
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<dd><p>Return a newly allocated copy of <var class="var">bv</var>.
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</p></dd></dl>
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<dl class="first-deftypefn">
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<dt class="deftypefn" id="index-scm_005fc_005fbytevector_005fref"><span class="category-def">C Function: </span><span><code class="def-type">scm_t_uint8</code> <strong class="def-name">scm_c_bytevector_ref</strong> <code class="def-code-arguments">(SCM bv, size_t index)</code><a class="copiable-link" href="#index-scm_005fc_005fbytevector_005fref"> ¶</a></span></dt>
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<dd><p>Return the byte at <var class="var">index</var> in bytevector <var class="var">bv</var>.
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</p></dd></dl>
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<dl class="first-deftypefn">
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<dt class="deftypefn" id="index-scm_005fc_005fbytevector_005fset_005fx"><span class="category-def">C Function: </span><span><code class="def-type">void</code> <strong class="def-name">scm_c_bytevector_set_x</strong> <code class="def-code-arguments">(SCM bv, size_t index, scm_t_uint8 value)</code><a class="copiable-link" href="#index-scm_005fc_005fbytevector_005fset_005fx"> ¶</a></span></dt>
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<dd><p>Set the byte at <var class="var">index</var> in <var class="var">bv</var> to <var class="var">value</var>.
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</p></dd></dl>
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<p>Low-level C macros are available. They do not perform any
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type-checking; as such they should be used with care.
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</p>
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<dl class="first-deftypefn">
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<dt class="deftypefn" id="index-SCM_005fBYTEVECTOR_005fLENGTH"><span class="category-def">C Macro: </span><span><code class="def-type">size_t</code> <strong class="def-name">SCM_BYTEVECTOR_LENGTH</strong> <code class="def-code-arguments">(bv)</code><a class="copiable-link" href="#index-SCM_005fBYTEVECTOR_005fLENGTH"> ¶</a></span></dt>
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<dd><p>Return the length in bytes of bytevector <var class="var">bv</var>.
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</p></dd></dl>
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<dl class="first-deftypefn">
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<dt class="deftypefn" id="index-SCM_005fBYTEVECTOR_005fCONTENTS"><span class="category-def">C Macro: </span><span><code class="def-type">signed char *</code> <strong class="def-name">SCM_BYTEVECTOR_CONTENTS</strong> <code class="def-code-arguments">(bv)</code><a class="copiable-link" href="#index-SCM_005fBYTEVECTOR_005fCONTENTS"> ¶</a></span></dt>
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<dd><p>Return a pointer to the contents of bytevector <var class="var">bv</var>.
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</p></dd></dl>
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</div>
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<div class="footnotes-segment">
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<hr>
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<h4 class="footnotes-heading">Footnotes</h4>
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<h5 class="footnote-body-heading"><a id="FOOT11" href="#DOCF11">(11)</a></h5>
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<p>R6RS only defines <code class="code">(bytevector-fill! bv
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fill)</code>. Arguments <var class="var">start</var> and <var class="var">end</var> are a Guile extension
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(cf. <a class="ref" href="Vector-Accessors.html#x_002dvector_002dfill_0021"><code class="code">vector-fill!</code></a>,
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<a class="ref" href="String-Modification.html#x_002dstring_002dfill_0021"><code class="code">string-fill!</code></a>).</p>
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Next: <a href="Bytevectors-as-Integers.html">Interpreting Bytevector Contents as Integers</a>, Previous: <a href="Bytevector-Endianness.html">Endianness</a>, Up: <a href="Bytevectors.html">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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