Fix bug
[ 555817 ] Flawed fcntl.ioctl implementation.
with my patch that allows for an array to be mutated when passed
as the buffer argument to ioctl() (details complicated by
backwards compatibility considerations -- read the docs!).
diff --git a/Doc/lib/libfcntl.tex b/Doc/lib/libfcntl.tex
index 645a97e..6eccb4a 100644
--- a/Doc/lib/libfcntl.tex
+++ b/Doc/lib/libfcntl.tex
@@ -47,10 +47,57 @@
raised.
\end{funcdesc}
-\begin{funcdesc}{ioctl}{fd, op, arg}
- This function is identical to the \function{fcntl()} function, except
- that the operations are typically defined in the library module
- \refmodule{termios}.
+\begin{funcdesc}{ioctl}{fd, op\optional{, arg\optional{, mutate_flag}}}
+ This function is identical to the \function{fcntl()} function,
+ except that the operations are typically defined in the library
+ module \refmodule{termios} and the argument handling is even more
+ complicated.
+
+ The parameter \var{arg} can be one of an integer, absent (treated
+ identically to the integer \code{0}), an object supporting the
+ read-only buffer interface (most likely a plain Python string) or an
+ object supporting the read-write buffer interface.
+
+ In all but the last case, behaviour is as for the \function{fcntl()}
+ function.
+
+ If a mutable buffer is passed, then the behaviour is determined by
+ the value of the \var{mutate_flag} parameter.
+
+ If it is false, the buffer's mutability is ignored and behaviour is
+ as for a read-only buffer, except that the 1024 byte limit mentioned
+ above is avoided -- so long as the buffer you pass is longer than
+ what the operating system wants to put there, things should work.
+
+ If \var{mutate_flag} is true, then the buffer is (in effect) passed
+ to the underlying \function{ioctl()} system call, the latter's
+ return code is passed back to the calling Python, and the buffer's
+ new contents reflect the action of the \function{ioctl}. This is a
+ slight simplification, because if the supplied buffer is less than
+ 1024 bytes long it is first copied into a static buffer 1024 bytes
+ long which is then passed to \function{ioctl} and copied back into
+ the supplied buffer.
+
+ If \var{mutate_flag} is not supplied, then in 2.3 it defaults to
+ false. This is planned to change over the next few Python versions:
+ in 2.4 failing to supply \var{mutate_flag} will get a warning but
+ the same behavior and in versions later than 2.5 it will default to
+ true.
+
+ An example:
+
+\begin{verbatim}
+>>> import array, fnctl, struct, termios, os
+>>> os.getpgrp()
+13341
+>>> struct.unpack('h', fcntl.ioctl(0, termios.TIOCGPGRP, " "))[0]
+13341
+>>> buf = array.array('h', [0])
+>>> fcntl.ioctl(0, termios.TIOCGPGRP, buf, 1)
+0
+>>> buf
+array('h', [13341])
+\end{verbatim}
\end{funcdesc}
\begin{funcdesc}{flock}{fd, op}
@@ -122,7 +169,7 @@
\begin{seealso}
\seemodule{os}{The \function{os.open} function supports locking flags
and is available on a wider variety of platforms than
- the \function{fcntl.lockf} and \function{fcntl.flock}
- functions, providing a more platform-independent file
- locking facility.}
+ the \function{fcntl.lockf} and \function{fcntl.flock}
+ functions, providing a more platform-independent file
+ locking facility.}
\end{seealso}
diff --git a/Lib/test/test_ioctl.py b/Lib/test/test_ioctl.py
new file mode 100644
index 0000000..a6a59c5
--- /dev/null
+++ b/Lib/test/test_ioctl.py
@@ -0,0 +1,31 @@
+import unittest
+from test_support import TestSkipped, run_unittest
+import os, struct
+try:
+ import fcntl, termios
+except ImportError:
+ raise TestSkipped("No fcntl or termios module")
+if not hasattr(termios,'TIOCGPGRP'):
+ raise TestSkipped("termios module doesn't have TIOCGPGRP")
+
+class IoctlTests(unittest.TestCase):
+ def test_ioctl(self):
+ pgrp = os.getpgrp()
+ tty = open("/dev/tty", "r")
+ r = fcntl.ioctl(tty, termios.TIOCGPGRP, " ")
+ self.assertEquals(pgrp, struct.unpack("i", r)[0])
+
+ def test_ioctl_mutate(self):
+ import array
+ buf = array.array('i', [0])
+ pgrp = os.getpgrp()
+ tty = open("/dev/tty", "r")
+ r = fcntl.ioctl(tty, termios.TIOCGPGRP, buf, 1)
+ self.assertEquals(r, 0)
+ self.assertEquals(pgrp, buf[0])
+
+def test_main():
+ run_unittest(IoctlTests)
+
+if __name__ == "__main__":
+ test_main()
diff --git a/Misc/NEWS b/Misc/NEWS
index a6dc7c6..bb13310 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -24,6 +24,9 @@
Extension modules
-----------------
+- Modified the fcntl.ioctl() function to allow modification of a passed
+ mutable buffer (for details see the reference documentation).
+
- Made user requested changes to the itertools module.
Subsumed the times() function into repeat().
Added chain() and cycle().
diff --git a/Modules/fcntlmodule.c b/Modules/fcntlmodule.c
index c5d9b4d..c495a77 100644
--- a/Modules/fcntlmodule.c
+++ b/Modules/fcntlmodule.c
@@ -99,8 +99,62 @@
int ret;
char *str;
int len;
+ int mutate_arg = 0;
char buf[1024];
+ if (PyArg_ParseTuple(args, "O&iw#|i:ioctl",
+ conv_descriptor, &fd, &code,
+ &str, &len, &mutate_arg)) {
+ char *arg;
+
+ if (PyTuple_Size(args) == 3) {
+ /* warning goes here in 2.4 */
+ mutate_arg = 0;
+ }
+ if (mutate_arg) {
+ if (len <= sizeof buf) {
+ memcpy(buf, str, len);
+ arg = buf;
+ }
+ else {
+ arg = str;
+ }
+ }
+ else {
+ if (len > sizeof buf) {
+ PyErr_SetString(PyExc_ValueError,
+ "ioctl string arg too long");
+ return NULL;
+ }
+ else {
+ memcpy(buf, str, len);
+ arg = buf;
+ }
+ }
+ if (buf == arg) {
+ Py_BEGIN_ALLOW_THREADS /* think array.resize() */
+ ret = ioctl(fd, code, arg);
+ Py_END_ALLOW_THREADS
+ }
+ else {
+ ret = ioctl(fd, code, arg);
+ }
+ if (mutate_arg && (len < sizeof buf)) {
+ memcpy(str, buf, len);
+ }
+ if (ret < 0) {
+ PyErr_SetFromErrno(PyExc_IOError);
+ return NULL;
+ }
+ if (mutate_arg) {
+ return PyInt_FromLong(ret);
+ }
+ else {
+ return PyString_FromStringAndSize(buf, len);
+ }
+ }
+
+ PyErr_Clear();
if (PyArg_ParseTuple(args, "O&is#:ioctl",
conv_descriptor, &fd, &code, &str, &len)) {
if (len > sizeof buf) {
@@ -123,7 +177,7 @@
arg = 0;
if (!PyArg_ParseTuple(args,
"O&i|i;ioctl requires a file or file descriptor,"
- " an integer and optionally a third integer or a string",
+ " an integer and optionally a integer or buffer argument",
conv_descriptor, &fd, &code, &arg)) {
return NULL;
}
@@ -138,17 +192,35 @@
}
PyDoc_STRVAR(ioctl_doc,
-"ioctl(fd, opt, [arg])\n\
+"ioctl(fd, opt[, arg[, mutate_flag]])\n\
\n\
-Perform the requested operation on file descriptor fd. The operation\n\
-is defined by op and is operating system dependent. Typically these\n\
-codes can be retrieved from the library module IOCTL. The argument arg\n\
-is optional, and defaults to 0; it may be an int or a string. If arg is\n\
-given as a string, the return value of ioctl is a string of that length,\n\
-containing the resulting value put in the arg buffer by the operating system.\n\
-The length of the arg string is not allowed to exceed 1024 bytes. If the arg\n\
-given is an integer or if none is specified, the result value is an integer\n\
-corresponding to the return value of the ioctl call in the C code.");
+Perform the requested operation on file descriptor fd. The operation is\n\
+defined by op and is operating system dependent. Typically these codes are\n\
+retrieved from the fcntl or termios library modules.\n\
+\n\
+The argument arg is optional, and defaults to 0; it may be an int or a\n\
+buffer containing character data (most likely a string or an array). \n\
+\n\
+If the argument is a mutable buffer (such as an array) and if the\n\
+mutate_flag argument (which is only allowed in this case) is true then the\n\
+buffer is (in effect) passed to the operating system and changes made by\n\
+the OS will be reflected in the contents of the buffer after the call has\n\
+returned. The return value is the integer returned by the ioctl system\n\
+call.\n\
+\n\
+If the argument is a mutable buffer and the mutable_flag argument is not\n\
+passed or is false, the behavior is as if a string had been passed. This\n\
+behavior will change in future releases of Python.\n\
+\n\
+If the argument is an immutable buffer (most likely a string) then a copy\n\
+of the buffer is passed to the operating system and the return value is a\n\
+string of the same length containing whatever the operating system put in\n\
+the buffer. The length of the arg buffer in this case is not allowed to\n\
+exceed 1024 bytes.\n\
+\n\
+If the arg given is an integer or if none is specified, the result value is\n\
+an integer corresponding to the return value of the ioctl call in the C\n\
+code.");
/* flock(fd, operation) */