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