compat: add writev() replacement

compat/writev.c

@@ -0,0 +1,72 @@
+/*****************************************************************************
+ * writev.c: POSIX writev() replacement
+ *****************************************************************************
+ * Copyright © 2022 Rémi Denis-Courmont
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifdef _WIN32
+# include <io.h>
+#else
+# include <unistd.h>
+#endif
+
+ssize_t writev(int fd, const struct iovec *iov, int iovcnt)
+{
+    if (iovcnt == 1)
+        return write(fd, iov->iov_base, iov->iov_len);
+
+    size_t size = 0;
+
+    for (int i = 0; i < iovcnt; i++) {
+        /* TODO: use ckd_add() */
+        size += iov[i].iov_len;
+
+        if (iov[i].iov_len > size) {
+            errno = EINVAL;
+            return -1;
+        }
+    }
+
+    void *buf = malloc(size ? size : 1);
+    if (buf == NULL) {
+        errno = ENOBUFS;
+        return -1;
+    }
+
+    unsigned char *ptr = buf;
+
+    for (int i = 0; i < iovcnt; i++) {
+        memcpy(ptr, iov->iov_base, iov->iov_len);
+        ptr += iov->iov_len;
+        iov++;
+    }
+
+    ssize_t bytes = write(fd, buf, size);
+    int saved_errno = errno;
+
+    free(buf);
+    errno = saved_errno;
+    return bytes;
+}

configure.ac

@@ -718,7 +718,7 @@ need_libc=false
 
 dnl Check for usual libc functions
 AC_CHECK_FUNCS([accept4 dup3 fcntl flock fstatat fstatvfs fork getmntent_r getenv getpwuid_r isatty memalign mkostemp mmap open_memstream newlocale pipe2 posix_fadvise setlocale stricmp uselocale wordexp])
-AC_REPLACE_FUNCS([aligned_alloc atof atoll dirfd fdopendir flockfile fsync getdelim getpid lfind lldiv memrchr nrand48 poll posix_memalign readv recvmsg rewind sendmsg setenv strcasecmp strcasestr strdup strlcpy strndup strnlen strnstr strsep strtof strtok_r strtoll swab tdestroy tfind timegm timespec_get strverscmp])
+AC_REPLACE_FUNCS([aligned_alloc atof atoll dirfd fdopendir flockfile fsync getdelim getpid lfind lldiv memrchr nrand48 poll posix_memalign readv recvmsg rewind sendmsg setenv strcasecmp strcasestr strdup strlcpy strndup strnlen strnstr strsep strtof strtok_r strtoll swab tdestroy tfind timegm timespec_get strverscmp writev])
 AC_REPLACE_FUNCS([gettimeofday])
 AC_CHECK_FUNC(fdatasync,,
   [AC_DEFINE(fdatasync, fsync, [Alias fdatasync() to fsync() if missing.])

include/vlc_fixups.h

@@ -232,6 +232,11 @@ struct iovec;
 ssize_t readv(int, const struct iovec *, int);
 #endif
 
+#ifndef HAVE_WRITEV
+struct iovec;
+ssize_t writev(int, const struct iovec *, int);
+#endif
+
 /* time.h */
 #ifndef HAVE_GMTIME_R
 struct tm *gmtime_r (const time_t *, struct tm *);