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136 lines
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<title>Memory Ports in Guile - Debugging with GDB</title>
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<link rel="up" href="Guile-API.html#Guile-API" title="Guile API">
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<link rel="prev" href="I_002fO-Ports-in-Guile.html#I_002fO-Ports-in-Guile" title="I/O Ports in Guile">
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<body>
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<div class="node">
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<a name="Memory-Ports-in-Guile"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Iterators-In-Guile.html#Iterators-In-Guile">Iterators In Guile</a>,
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Previous: <a rel="previous" accesskey="p" href="I_002fO-Ports-in-Guile.html#I_002fO-Ports-in-Guile">I/O Ports in Guile</a>,
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Up: <a rel="up" accesskey="u" href="Guile-API.html#Guile-API">Guile API</a>
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<hr>
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</div>
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<h5 class="subsubsection">23.3.3.24 Memory Ports in Guile</h5>
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<p><span class="sc">gdb</span> provides a <code>port</code> interface to target memory.
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This allows Guile code to read/write target memory using Guile's port and
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bytevector functionality. The main routine is <code>open-memory</code> which
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returns a port object. One can then read/write memory using that object.
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<div class="defun">
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— Scheme Procedure: <b>open-memory</b> <span class="roman">[</span><var>#:mode mode</var>] <span class="roman">[</span><var>#:start address</var>] <span class="roman">[</span><var>#:size size</var>]<var><a name="index-open_002dmemory-2848"></a></var><br>
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<blockquote><p>Return a port object that can be used for reading and writing memory.
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The port will be open according to <var>mode</var>, which is the standard
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mode argument to Guile port open routines, except that the ‘<samp><span class="samp">"a"</span></samp>’
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and ‘<samp><span class="samp">"l"</span></samp>’ modes are not supported.
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See <a href="../guile/File-Ports.html#File-Ports">File Ports</a>.
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The ‘<samp><span class="samp">"b"</span></samp>’ (binary) character may be present, but is ignored:
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memory ports are binary only. If ‘<samp><span class="samp">"0"</span></samp>’ is appended then
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the port is marked as unbuffered.
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The default is ‘<samp><span class="samp">"r"</span></samp>’, read-only and buffered.
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<p>The chunk of memory that can be accessed can be bounded.
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If both <var>start</var> and <var>size</var> are unspecified, all of memory can be
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accessed. If only <var>start</var> is specified, all of memory from that point
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on can be accessed. If only <var>size</var> if specified, all memory in the
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range [0,<var>size</var>) can be accessed. If both are specified, all memory
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in the rane [<var>start</var>,<var>start</var>+<var>size</var>) can be accessed.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>memory-port?</b><var><a name="index-memory_002dport_003f-2849"></a></var><br>
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<blockquote><p>Return <code>#t</code> if <var>object</var> is an object of type <code><gdb:memory-port></code>.
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Otherwise return <code>#f</code>.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>memory-port-range</b><var> memory-port<a name="index-memory_002dport_002drange-2850"></a></var><br>
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<blockquote><p>Return the range of <code><gdb:memory-port></code> <var>memory-port</var> as a list
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of two elements: <code>(start end)</code>. The range is <var>start</var> to <var>end</var>
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inclusive.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>memory-port-read-buffer-size</b><var> memory-port<a name="index-memory_002dport_002dread_002dbuffer_002dsize-2851"></a></var><br>
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<blockquote><p>Return the size of the read buffer of <code><gdb:memory-port></code>
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<var>memory-port</var>.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>set-memory-port-read-buffer-size!</b><var> memory-port size<a name="index-set_002dmemory_002dport_002dread_002dbuffer_002dsize_0021-2852"></a></var><br>
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<blockquote><p>Set the size of the read buffer of <code><gdb:memory-port></code>
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<var>memory-port</var> to <var>size</var>. The result is unspecified.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>memory-port-write-buffer-size</b><var> memory-port<a name="index-memory_002dport_002dwrite_002dbuffer_002dsize-2853"></a></var><br>
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<blockquote><p>Return the size of the write buffer of <code><gdb:memory-port></code>
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<var>memory-port</var>.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>set-memory-port-write-buffer-size!</b><var> memory-port size<a name="index-set_002dmemory_002dport_002dwrite_002dbuffer_002dsize_0021-2854"></a></var><br>
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<blockquote><p>Set the size of the write buffer of <code><gdb:memory-port></code>
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<var>memory-port</var> to <var>size</var>. The result is unspecified.
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</p></blockquote></div>
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<p>A memory port is closed like any other port, with <code>close-port</code>.
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<p>Combined with Guile's <code>bytevectors</code>, memory ports provide a lot
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of utility. For example, to fill a buffer of 10 integers in memory,
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one can do something like the following.
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<pre class="smallexample"> ;; In the program: int buffer[10];
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(use-modules (rnrs bytevectors))
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(use-modules (rnrs io ports))
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(define addr (parse-and-eval "buffer"))
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(define n 10)
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(define byte-size (* n 4))
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(define mem-port (open-memory #:mode "r+" #:start
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(value->integer addr) #:size byte-size))
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(define byte-vec (make-bytevector byte-size))
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(do ((i 0 (+ i 1)))
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((>= i n))
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(bytevector-s32-native-set! byte-vec (* i 4) (* i 42)))
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(put-bytevector mem-port byte-vec)
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(close-port mem-port)
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</pre>
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</body></html>
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