bpo-41710: Add private _PyDeadline_Get() function (GH-28674)

Add a private C API for deadlines: add _PyDeadline_Init() and
_PyDeadline_Get() functions.

* Add _PyTime_Add() and _PyTime_Mul() functions which compute t1+t2
  and t1*t2 and clamp the result on overflow.
* _PyTime_MulDiv() now uses _PyTime_Add() and _PyTime_Mul().

1 files changed, 11 insertions, 9 deletions

diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index f474869..9821227 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -840,18 +840,20 @@ sock_call_ex(PySocketSockObject *s,
 
                 if (deadline_initialized) {
                     /* recompute the timeout */
-                    interval = deadline - _PyTime_GetMonotonicClock();
+                    interval = _PyDeadline_Get(deadline);
                 }
                 else {
                     deadline_initialized = 1;
-                    deadline = _PyTime_GetMonotonicClock() + timeout;
+                    deadline = _PyDeadline_Init(timeout);
                     interval = timeout;
                 }
 
-                if (interval >= 0)
+                if (interval >= 0) {
                     res = internal_select(s, writing, interval, connect);
-                else
+                }
+                else {
                     res = 1;
+                }
             }
             else {
                 res = internal_select(s, writing, timeout, connect);
@@ -4176,7 +4178,7 @@ sock_sendall(PySocketSockObject *s, PyObject *args)
     Py_buffer pbuf;
     struct sock_send ctx;
     int has_timeout = (s->sock_timeout > 0);
-    _PyTime_t interval = s->sock_timeout;
+    _PyTime_t timeout = s->sock_timeout;
     _PyTime_t deadline = 0;
     int deadline_initialized = 0;
     PyObject *res = NULL;
@@ -4195,14 +4197,14 @@ sock_sendall(PySocketSockObject *s, PyObject *args)
         if (has_timeout) {
             if (deadline_initialized) {
                 /* recompute the timeout */
-                interval = deadline - _PyTime_GetMonotonicClock();
+                timeout = _PyDeadline_Get(deadline);
             }
             else {
                 deadline_initialized = 1;
-                deadline = _PyTime_GetMonotonicClock() + s->sock_timeout;
+                deadline = _PyDeadline_Init(timeout);
             }
 
-            if (interval <= 0) {
+            if (timeout <= 0) {
                 PyErr_SetString(PyExc_TimeoutError, "timed out");
                 goto done;
             }
@@ -4211,7 +4213,7 @@ sock_sendall(PySocketSockObject *s, PyObject *args)
         ctx.buf = buf;
         ctx.len = len;
         ctx.flags = flags;
-        if (sock_call_ex(s, 1, sock_send_impl, &ctx, 0, NULL, interval) < 0)
+        if (sock_call_ex(s, 1, sock_send_impl, &ctx, 0, NULL, timeout) < 0)
             goto done;
         n = ctx.result;
         assert(n >= 0);