Issue #23708: Add _Py_read() and _Py_write() functions to factorize code handle
EINTR error and special cases for Windows.
These functions now truncate the length to PY_SSIZE_T_MAX to have a portable
and reliable behaviour. For example, read() result is undefined if counter is
greater than PY_SSIZE_T_MAX on Linux.
diff --git a/Python/fileutils.c b/Python/fileutils.c
index fa481ae..0948781 100644
--- a/Python/fileutils.c
+++ b/Python/fileutils.c
@@ -1120,6 +1120,155 @@
return f;
}
+/* Read count bytes from fd into buf.
+ *
+ * On success, return the number of read bytes, it can be lower than count.
+ * If the current file offset is at or past the end of file, no bytes are read,
+ * and read() returns zero.
+ *
+ * On error, raise an exception, set errno and return -1.
+ *
+ * When interrupted by a signal (read() fails with EINTR), retry the syscall.
+ * If the Python signal handler raises an exception, the function returns -1
+ * (the syscall is not retried).
+ *
+ * The GIL must be held. */
+Py_ssize_t
+_Py_read(int fd, void *buf, size_t count)
+{
+ Py_ssize_t n;
+ int async_err = 0;
+
+ /* _Py_read() must not be called with an exception set, otherwise the
+ * caller may think that read() was interrupted by a signal and the signal
+ * handler raised an exception. */
+ assert(!PyErr_Occurred());
+
+ if (!_PyVerify_fd(self->fd)) {
+ PyErr_SetFromErrno(PyExc_OSError);
+ assert(errno == EBADF);
+ return -1;
+ }
+
+#ifdef MS_WINDOWS
+ if (count > INT_MAX) {
+ /* On Windows, the count parameter of read() is an int */
+ count = INT_MAX;
+ }
+#else
+ if (count > PY_SSIZE_T_MAX) {
+ /* if count is greater than PY_SSIZE_T_MAX,
+ * read() result is undefined */
+ count = PY_SSIZE_T_MAX;
+ }
+#endif
+
+ do {
+ Py_BEGIN_ALLOW_THREADS
+ errno = 0;
+#ifdef MS_WINDOWS
+ n = read(fd, buf, (int)count);
+#else
+ n = read(fd, buf, count);
+#endif
+ Py_END_ALLOW_THREADS
+ } while (n < 0 && errno == EINTR &&
+ !(async_err = PyErr_CheckSignals()));
+
+ if (async_err) {
+ /* read() was interrupted by a signal (failed with EINTR)
+ * and the Python signal handler raised an exception */
+ assert(errno == EINTR && PyErr_Occurred());
+ return -1;
+ }
+ if (n < 0) {
+#ifndef NDEBUG
+ int err = errno;
+#endif
+ PyErr_SetFromErrno(PyExc_OSError);
+ assert(errno == err);
+ return -1;
+ }
+
+ return n;
+}
+
+/* Write count bytes of buf into fd.
+ *
+ * -On success, return the number of written bytes, it can be lower than count
+ * including 0
+ * - On error, raise an exception, set errno and return -1.
+ *
+ * When interrupted by a signal (write() fails with EINTR), retry the syscall.
+ * If the Python signal handler raises an exception, the function returns -1
+ * (the syscall is not retried).
+ *
+ * The GIL must be held. */
+Py_ssize_t
+_Py_write(int fd, const void *buf, size_t count)
+{
+ Py_ssize_t n;
+ int async_err = 0;
+
+ /* _Py_write() must not be called with an exception set, otherwise the
+ * caller may think that write() was interrupted by a signal and the signal
+ * handler raised an exception. */
+ assert(!PyErr_Occurred());
+
+ if (!_PyVerify_fd(fd)) {
+ PyErr_SetFromErrno(PyExc_OSError);
+ assert(errno == EBADF);
+ return -1;
+ }
+
+#ifdef MS_WINDOWS
+ if (count > 32767 && isatty(fd)) {
+ /* Issue #11395: the Windows console returns an error (12: not
+ enough space error) on writing into stdout if stdout mode is
+ binary and the length is greater than 66,000 bytes (or less,
+ depending on heap usage). */
+ count = 32767;
+ }
+ else if (count > INT_MAX)
+ count = INT_MAX;
+#else
+ if (count > PY_SSIZE_T_MAX) {
+ /* write() should truncate count to PY_SSIZE_T_MAX, but it's safer
+ * to do it ourself to have a portable behaviour. */
+ count = PY_SSIZE_T_MAX;
+ }
+#endif
+
+ do {
+ Py_BEGIN_ALLOW_THREADS
+ errno = 0;
+#ifdef MS_WINDOWS
+ n = write(fd, buf, (int)count);
+#else
+ n = write(fd, buf, count);
+#endif
+ Py_END_ALLOW_THREADS
+ } while (n < 0 && errno == EINTR &&
+ !(async_err = PyErr_CheckSignals()));
+
+ if (async_err) {
+ /* write() was interrupted by a signal (failed with EINTR)
+ * and the Python signal handler raised an exception */
+ assert(errno == EINTR && PyErr_Occurred());
+ return -1;
+ }
+ if (n < 0) {
+#ifndef NDEBUG
+ int err = errno;
+#endif
+ PyErr_SetFromErrno(PyExc_OSError);
+ assert(errno == err);
+ return -1;
+ }
+
+ return n;
+}
+
#ifdef HAVE_READLINK
/* Read value of symbolic link. Encode the path to the locale encoding, decode