diff options
Diffstat (limited to 'src/iopoll.c')
| -rw-r--r-- | src/iopoll.c | 66 |
1 files changed, 43 insertions, 23 deletions
diff --git a/src/iopoll.c b/src/iopoll.c index ceb1b43ad..a73ce05bf 100644 --- a/src/iopoll.c +++ b/src/iopoll.c @@ -18,6 +18,8 @@ #include <config.h> +#include <assert.h> + /* poll(2) is needed on AIX (where 'select' gives a readable event immediately) and Solaris (where 'select' never gave a readable event). Also use poll(2) on systems we know work @@ -26,6 +28,12 @@ #if defined _AIX || defined __sun || defined __APPLE__ || \ defined __linux__ || defined __ANDROID__ # define IOPOLL_USES_POLL 1 + /* Check we've not enabled gnulib's poll module + as that will emulate poll() in a way not + currently compatible with our usage. */ +# if defined HAVE_POLL +# error "gnulib's poll() replacement is currently incompatible" +# endif #endif #if IOPOLL_USES_POLL @@ -39,62 +47,74 @@ #include "isapipe.h" -/* Wait for fdin to become ready for reading or fdout to become a broken pipe. - Return 0 if fdin can be read() without blocking, or IOPOLL_BROKEN_OUTPUT if - fdout becomes a broken pipe, otherwise IOPOLL_ERROR if there is a poll() +/* Wait for FDIN to become ready for reading or FDOUT to become a broken pipe. + If either of those are -1, then they're not checked. Set BLOCK to true + to wait for an event, otherwise return the status immediately. + Return 0 if not BLOCKing and there is no event on the requested descriptors. + Return 0 if FDIN can be read() without blocking, or IOPOLL_BROKEN_OUTPUT if + FDOUT becomes a broken pipe, otherwise IOPOLL_ERROR if there is a poll() or select() error. */ -#if IOPOLL_USES_POLL - extern int -iopoll (int fdin, int fdout) +iopoll (int fdin, int fdout, bool block) { +#if IOPOLL_USES_POLL + struct pollfd pfds[2] = { /* POLLRDBAND needed for illumos, macOS. */ { .fd = fdin, .events = POLLIN | POLLRDBAND, .revents = 0 }, { .fd = fdout, .events = POLLRDBAND, .revents = 0 }, }; + int ret = 0; - while (poll (pfds, 2, -1) > 0 || errno == EINTR) + while (0 <= ret || errno == EINTR) { - if (errno == EINTR) + ret = poll (pfds, 2, block ? -1 : 0); + + if (ret < 0) continue; + if (ret == 0 && ! block) + return 0; + assert (0 < ret); if (pfds[0].revents) /* input available or pipe closed indicating EOF; */ return 0; /* should now be able to read() without blocking */ if (pfds[1].revents) /* POLLERR, POLLHUP (or POLLNVAL) */ return IOPOLL_BROKEN_OUTPUT; /* output error or broken pipe */ } - return IOPOLL_ERROR; /* poll error */ -} #else /* fall back to select()-based implementation */ -extern int -iopoll (int fdin, int fdout) -{ int nfds = (fdin > fdout ? fdin : fdout) + 1; int ret = 0; /* If fdout has an error condition (like a broken pipe) it will be seen as ready for reading. Assumes fdout is not actually readable. */ - while (ret >= 0 || errno == EINTR) + while (0 <= ret || errno == EINTR) { fd_set rfds; FD_ZERO (&rfds); - FD_SET (fdin, &rfds); - FD_SET (fdout, &rfds); - ret = select (nfds, &rfds, NULL, NULL, NULL); + if (0 <= fdin) + FD_SET (fdin, &rfds); + if (0 <= fdout) + FD_SET (fdout, &rfds); + + struct timeval delay = { .tv_sec = 0, .tv_usec = 0 }; + ret = select (nfds, &rfds, NULL, NULL, block ? NULL : &delay); if (ret < 0) continue; - if (FD_ISSET (fdin, &rfds)) /* input available or EOF; should now */ - return 0; /* be able to read() without blocking */ - if (FD_ISSET (fdout, &rfds)) /* POLLERR, POLLHUP (or POLLIN) */ - return IOPOLL_BROKEN_OUTPUT; /* output error or broken pipe */ + if (ret == 0 && ! block) + return 0; + assert (0 < ret); + if (0 <= fdin && FD_ISSET (fdin, &rfds)) /* input available or EOF; */ + return 0; /* should now be able to read() without blocking */ + if (0 <= fdout && FD_ISSET (fdout, &rfds)) /* equiv to POLLERR */ + return IOPOLL_BROKEN_OUTPUT; /* output error or broken pipe */ } - return IOPOLL_ERROR; /* select error */ -} #endif + return IOPOLL_ERROR; +} + /* Return true if fdin is relevant for iopoll(). |