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select: move duplicate select preparation code into Curl_select 

Reviewed by Daniel Stenberg
Reviewed by Marcel Raad
Closes #5078
This commit is contained in:
Marc Hoersken 2020-03-15 11:07:08 +01:00
parent dbd16c3e25
commit c52b342051
No known key found for this signature in database
GPG Key ID: 61E03CBED7BC859E
2 changed files with 89 additions and 81 deletions
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164
lib/select.c
View File

@ -100,6 +100,76 @@ int Curl_wait_ms(int timeout_ms)
return r;
}
/*
* This is a wrapper around select() to aid in Windows compatibility.
* A negative timeout value makes this function wait indefinitely,
* unless no valid file descriptor is given, when this happens the
* negative timeout is ignored and the function times out immediately.
*
* Return values:
* -1 = system call error or fd >= FD_SETSIZE
* 0 = timeout
* N = number of signalled file descriptors
*/
int Curl_select(curl_socket_t maxfd,
fd_set *fds_read,
fd_set *fds_write,
fd_set *fds_err,
time_t timeout_ms) /* milliseconds to wait */
{
struct timeval pending_tv;
struct timeval *ptimeout;
int pending_ms = 0;
int r;
#ifdef USE_WINSOCK
/* WinSock select() can't handle zero events. See the comment below. */
if((!fds_read || fds_read->fd_count == 0) &&
(!fds_write || fds_write->fd_count == 0) &&
(!fds_err || fds_err->fd_count == 0)) {
r = Curl_wait_ms((int)timeout_ms);
return r;
}
#endif
ptimeout = &pending_tv;
if(timeout_ms < 0) {
ptimeout = NULL;
}
else if(timeout_ms > 0) {
pending_ms = (int)timeout_ms;
pending_tv.tv_sec = pending_ms / 1000;
pending_tv.tv_usec = (pending_ms % 1000) * 1000;
}
else if(!timeout_ms) {
pending_tv.tv_sec = 0;
pending_tv.tv_usec = 0;
}
#ifdef USE_WINSOCK
/* WinSock select() must not be called with an fd_set that contains zero
fd flags, or it will return WSAEINVAL. But, it also can't be called
with no fd_sets at all! From the documentation:
Any two of the parameters, readfds, writefds, or exceptfds, can be
given as null. At least one must be non-null, and any non-null
descriptor set must contain at least one handle to a socket.
It is unclear why WinSock doesn't just handle this for us instead of
calling this an error.
*/
r = select((int)maxfd + 1,
fds_read && fds_read->fd_count ? fds_read : NULL,
fds_write && fds_write->fd_count ? fds_write : NULL,
fds_err && fds_err->fd_count ? fds_err : NULL, ptimeout);
#else
r = select((int)maxfd + 1, fds_read, fds_write, fds_err, ptimeout);
#endif
return r;
}
/*
* Wait for read or write events on a set of file descriptors. It uses poll()
* when a fine poll() is available, in order to avoid limits with FD_SETSIZE,
@ -127,16 +197,14 @@ int Curl_socket_check(curl_socket_t readfd0, /* two sockets to read from */
{
#ifdef HAVE_POLL_FINE
struct pollfd pfd[3];
int pending_ms = 0;
int num;
#else
struct timeval pending_tv;
struct timeval *ptimeout;
fd_set fds_read;
fd_set fds_write;
fd_set fds_err;
curl_socket_t maxfd;
#endif
int pending_ms = 0;
int r;
int ret;
@ -158,10 +226,6 @@ int Curl_socket_check(curl_socket_t readfd0, /* two sockets to read from */
when function is called with a zero timeout or a negative timeout
value indicating a blocking call should be performed. */
if(timeout_ms > 0) {
pending_ms = (int)timeout_ms;
}
#ifdef HAVE_POLL_FINE
num = 0;
@ -184,7 +248,9 @@ int Curl_socket_check(curl_socket_t readfd0, /* two sockets to read from */
num++;
}
if(timeout_ms < 0)
if(timeout_ms > 0)
pending_ms = (int)timeout_ms;
else if(timeout_ms < 0)
pending_ms = -1;
else if(!timeout_ms)
pending_ms = 0;
@ -249,46 +315,17 @@ int Curl_socket_check(curl_socket_t readfd0, /* two sockets to read from */
maxfd = writefd;
}
ptimeout = (timeout_ms < 0) ? NULL : &pending_tv;
if(timeout_ms > 0) {
pending_tv.tv_sec = pending_ms / 1000;
pending_tv.tv_usec = (pending_ms % 1000) * 1000;
}
else if(!timeout_ms) {
pending_tv.tv_sec = 0;
pending_tv.tv_usec = 0;
}
/* WinSock select() must not be called with an fd_set that contains zero
fd flags, or it will return WSAEINVAL. But, it also can't be called
with no fd_sets at all! From the documentation:
Any two of the parameters, readfds, writefds, or exceptfds, can be
given as null. At least one must be non-null, and any non-null
descriptor set must contain at least one handle to a socket.
We know that we have at least one bit set in at least two fd_sets in
/* We know that we have at least one bit set in at least two fd_sets in
this case, but we may have no bits set in either fds_read or fd_write,
so check for that and handle it. Luckily, with WinSock, we can _also_
ask how many bits are set on an fd_set.
It is unclear why WinSock doesn't just handle this for us instead of
calling this an error.
Note also that WinSock ignores the first argument, so we don't worry
about the fact that maxfd is computed incorrectly with WinSock (since
curl_socket_t is unsigned in such cases and thus -1 is the largest
value).
*/
#ifdef USE_WINSOCK
r = select((int)maxfd + 1,
fds_read.fd_count ? &fds_read : NULL,
fds_write.fd_count ? &fds_write : NULL,
&fds_err, ptimeout);
#else
r = select((int)maxfd + 1, &fds_read, &fds_write, &fds_err, ptimeout);
#endif
r = Curl_select(maxfd, &fds_read, &fds_write, &fds_err, timeout_ms);
if(r < 0)
return -1;
@ -336,9 +373,9 @@ int Curl_socket_check(curl_socket_t readfd0, /* two sockets to read from */
*/
int Curl_poll(struct pollfd ufds[], unsigned int nfds, int timeout_ms)
{
#ifndef HAVE_POLL_FINE
struct timeval pending_tv;
struct timeval *ptimeout;
#ifdef HAVE_POLL_FINE
int pending_ms = 0;
#else
fd_set fds_read;
fd_set fds_write;
fd_set fds_err;
@ -346,7 +383,6 @@ int Curl_poll(struct pollfd ufds[], unsigned int nfds, int timeout_ms)
#endif
bool fds_none = TRUE;
unsigned int i;
int pending_ms = 0;
int r;
if(ufds) {
@ -367,13 +403,11 @@ int Curl_poll(struct pollfd ufds[], unsigned int nfds, int timeout_ms)
when function is called with a zero timeout or a negative timeout
value indicating a blocking call should be performed. */
if(timeout_ms > 0) {
pending_ms = timeout_ms;
}
#ifdef HAVE_POLL_FINE
if(timeout_ms < 0)
if(timeout_ms > 0)
pending_ms = timeout_ms;
else if(timeout_ms < 0)
pending_ms = -1;
else if(!timeout_ms)
pending_ms = 0;
@ -418,39 +452,7 @@ int Curl_poll(struct pollfd ufds[], unsigned int nfds, int timeout_ms)
}
}
#ifdef USE_WINSOCK
/* WinSock select() can't handle zero events. See the comment about this in
Curl_check_socket(). */
if(fds_read.fd_count == 0 && fds_write.fd_count == 0
&& fds_err.fd_count == 0) {
r = Curl_wait_ms(timeout_ms);
return r;
}
#endif
ptimeout = (timeout_ms < 0) ? NULL : &pending_tv;
if(timeout_ms > 0) {
pending_tv.tv_sec = pending_ms / 1000;
pending_tv.tv_usec = (pending_ms % 1000) * 1000;
}
else if(!timeout_ms) {
pending_tv.tv_sec = 0;
pending_tv.tv_usec = 0;
}
#ifdef USE_WINSOCK
r = select((int)maxfd + 1,
/* WinSock select() can't handle fd_sets with zero bits set, so
don't give it such arguments. See the comment about this in
Curl_check_socket().
*/
fds_read.fd_count ? &fds_read : NULL,
fds_write.fd_count ? &fds_write : NULL,
fds_err.fd_count ? &fds_err : NULL, ptimeout);
#else
r = select((int)maxfd + 1, &fds_read, &fds_write, &fds_err, ptimeout);
#endif
r = Curl_select(maxfd, &fds_read, &fds_write, &fds_err, timeout_ms);
if(r < 0)
return -1;

6
lib/select.h
View File

@ -72,6 +72,12 @@ struct pollfd
therefore defined here */
#define CURL_CSELECT_IN2 (CURL_CSELECT_ERR << 1)
int Curl_select(curl_socket_t maxfd,
fd_set *fds_read,
fd_set *fds_write,
fd_set *fds_err,
time_t timeout_ms);
int Curl_socket_check(curl_socket_t readfd, curl_socket_t readfd2,
curl_socket_t writefd,
time_t timeout_ms);