Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 308 insertions, 0 deletions

diff --git a/src/basic/io-util.c b/src/basic/io-util.c
new file mode 100644
index 0000000..6bcbef3
--- /dev/null
+++ b/src/basic/io-util.c
@@ -0,0 +1,308 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "errno-util.h"
+#include "io-util.h"
+#include "iovec-util.h"
+#include "string-util.h"
+#include "time-util.h"
+
+int flush_fd(int fd) {
+        int count = 0;
+
+        /* Read from the specified file descriptor, until POLLIN is not set anymore, throwing away everything
+         * read. Note that some file descriptors (notable IP sockets) will trigger POLLIN even when no data can be read
+         * (due to IP packet checksum mismatches), hence this function is only safe to be non-blocking if the fd used
+         * was set to non-blocking too. */
+
+        for (;;) {
+                char buf[LINE_MAX];
+                ssize_t l;
+                int r;
+
+                r = fd_wait_for_event(fd, POLLIN, 0);
+                if (r < 0) {
+                        if (r == -EINTR)
+                                continue;
+
+                        return r;
+                }
+                if (r == 0)
+                        return count;
+
+                l = read(fd, buf, sizeof(buf));
+                if (l < 0) {
+                        if (errno == EINTR)
+                                continue;
+
+                        if (errno == EAGAIN)
+                                return count;
+
+                        return -errno;
+                } else if (l == 0)
+                        return count;
+
+                count += (int) l;
+        }
+}
+
+ssize_t loop_read(int fd, void *buf, size_t nbytes, bool do_poll) {
+        uint8_t *p = ASSERT_PTR(buf);
+        ssize_t n = 0;
+
+        assert(fd >= 0);
+
+        /* If called with nbytes == 0, let's call read() at least once, to validate the operation */
+
+        if (nbytes > (size_t) SSIZE_MAX)
+                return -EINVAL;
+
+        do {
+                ssize_t k;
+
+                k = read(fd, p, nbytes);
+                if (k < 0) {
+                        if (errno == EINTR)
+                                continue;
+
+                        if (errno == EAGAIN && do_poll) {
+
+                                /* We knowingly ignore any return value here,
+                                 * and expect that any error/EOF is reported
+                                 * via read() */
+
+                                (void) fd_wait_for_event(fd, POLLIN, USEC_INFINITY);
+                                continue;
+                        }
+
+                        return n > 0 ? n : -errno;
+                }
+
+                if (k == 0)
+                        return n;
+
+                assert((size_t) k <= nbytes);
+
+                p += k;
+                nbytes -= k;
+                n += k;
+        } while (nbytes > 0);
+
+        return n;
+}
+
+int loop_read_exact(int fd, void *buf, size_t nbytes, bool do_poll) {
+        ssize_t n;
+
+        n = loop_read(fd, buf, nbytes, do_poll);
+        if (n < 0)
+                return (int) n;
+        if ((size_t) n != nbytes)
+                return -EIO;
+
+        return 0;
+}
+
+int loop_write_full(int fd, const void *buf, size_t nbytes, usec_t timeout) {
+        const uint8_t *p;
+        usec_t end;
+        int r;
+
+        assert(fd >= 0);
+        assert(buf || nbytes == 0);
+
+        if (nbytes == 0) {
+                static const dummy_t dummy[0];
+                assert_cc(sizeof(dummy) == 0);
+                p = (const void*) dummy; /* Some valid pointer, in case NULL was specified */
+        } else {
+                if (nbytes == SIZE_MAX)
+                        nbytes = strlen(buf);
+                else if (_unlikely_(nbytes > (size_t) SSIZE_MAX))
+                        return -EINVAL;
+
+                p = buf;
+        }
+
+        /* When timeout is 0 or USEC_INFINITY this is not used. But we initialize it to a sensible value. */
+        end = timestamp_is_set(timeout) ? usec_add(now(CLOCK_MONOTONIC), timeout) : USEC_INFINITY;
+
+        do {
+                ssize_t k;
+
+                k = write(fd, p, nbytes);
+                if (k < 0) {
+                        if (errno == EINTR)
+                                continue;
+
+                        if (errno != EAGAIN || timeout == 0)
+                                return -errno;
+
+                        usec_t wait_for;
+
+                        if (timeout == USEC_INFINITY)
+                                wait_for = USEC_INFINITY;
+                        else {
+                                usec_t t = now(CLOCK_MONOTONIC);
+                                if (t >= end)
+                                        return -ETIME;
+
+                                wait_for = usec_sub_unsigned(end, t);
+                        }
+
+                        r = fd_wait_for_event(fd, POLLOUT, wait_for);
+                        if (timeout == USEC_INFINITY || ERRNO_IS_NEG_TRANSIENT(r))
+                                /* If timeout == USEC_INFINITY we knowingly ignore any return value
+                                 * here, and expect that any error/EOF is reported via write() */
+                                continue;
+                        if (r < 0)
+                                return r;
+                        if (r == 0)
+                                return -ETIME;
+                        continue;
+                }
+
+                if (_unlikely_(nbytes > 0 && k == 0)) /* Can't really happen */
+                        return -EIO;
+
+                assert((size_t) k <= nbytes);
+
+                p += k;
+                nbytes -= k;
+        } while (nbytes > 0);
+
+        return 0;
+}
+
+int pipe_eof(int fd) {
+        int r;
+
+        r = fd_wait_for_event(fd, POLLIN, 0);
+        if (r <= 0)
+                return r;
+
+        return !!(r & POLLHUP);
+}
+
+int ppoll_usec(struct pollfd *fds, size_t nfds, usec_t timeout) {
+        int r;
+
+        assert(fds || nfds == 0);
+
+        /* This is a wrapper around ppoll() that does primarily two things:
+         *
+         *  ✅ Takes a usec_t instead of a struct timespec
+         *
+         *  ✅ Guarantees that if an invalid fd is specified we return EBADF (i.e. converts POLLNVAL to
+         *     EBADF). This is done because EBADF is a programming error usually, and hence should bubble up
+         *     as error, and not be eaten up as non-error POLLNVAL event.
+         *
+         *  ⚠️ ⚠️ ⚠️ Note that this function does not add any special handling for EINTR. Don't forget
+         *  poll()/ppoll() will return with EINTR on any received signal always, there is no automatic
+         *  restarting via SA_RESTART available. Thus, typically you want to handle EINTR not as an error,
+         *  but just as reason to restart things, under the assumption you use a more appropriate mechanism
+         *  to handle signals, such as signalfd() or signal handlers. ⚠️ ⚠️ ⚠️
+         */
+
+        if (nfds == 0)
+                return 0;
+
+        r = ppoll(fds, nfds, timeout == USEC_INFINITY ? NULL : TIMESPEC_STORE(timeout), NULL);
+        if (r < 0)
+                return -errno;
+        if (r == 0)
+                return 0;
+
+        for (size_t i = 0, n = r; i < nfds && n > 0; i++) {
+                if (fds[i].revents == 0)
+                        continue;
+                if (fds[i].revents & POLLNVAL)
+                        return -EBADF;
+                n--;
+        }
+
+        return r;
+}
+
+int fd_wait_for_event(int fd, int event, usec_t timeout) {
+        struct pollfd pollfd = {
+                .fd = fd,
+                .events = event,
+        };
+        int r;
+
+        /* ⚠️ ⚠️ ⚠️ Keep in mind you almost certainly want to handle -EINTR gracefully in the caller, see
+         * ppoll_usec() above! ⚠️ ⚠️ ⚠️ */
+
+        r = ppoll_usec(&pollfd, 1, timeout);
+        if (r <= 0)
+                return r;
+
+        return pollfd.revents;
+}
+
+static size_t nul_length(const uint8_t *p, size_t sz) {
+        size_t n = 0;
+
+        while (sz > 0) {
+                if (*p != 0)
+                        break;
+
+                n++;
+                p++;
+                sz--;
+        }
+
+        return n;
+}
+
+ssize_t sparse_write(int fd, const void *p, size_t sz, size_t run_length) {
+        const uint8_t *q, *w, *e;
+        ssize_t l;
+
+        q = w = p;
+        e = q + sz;
+        while (q < e) {
+                size_t n;
+
+                n = nul_length(q, e - q);
+
+                /* If there are more than the specified run length of
+                 * NUL bytes, or if this is the beginning or the end
+                 * of the buffer, then seek instead of write */
+                if ((n > run_length) ||
+                    (n > 0 && q == p) ||
+                    (n > 0 && q + n >= e)) {
+                        if (q > w) {
+                                l = write(fd, w, q - w);
+                                if (l < 0)
+                                        return -errno;
+                                if (l != q -w)
+                                        return -EIO;
+                        }
+
+                        if (lseek(fd, n, SEEK_CUR) < 0)
+                                return -errno;
+
+                        q += n;
+                        w = q;
+                } else if (n > 0)
+                        q += n;
+                else
+                        q++;
+        }
+
+        if (q > w) {
+                l = write(fd, w, q - w);
+                if (l < 0)
+                        return -errno;
+                if (l != q - w)
+                        return -EIO;
+        }
+
+        return q - (const uint8_t*) p;
+}