Add preadv2/pwritev2 wrappers.
They're in glibc, though not in musl.
Also add basic doc comments to the whole of <sys/uio.h>.
Bug: http://b/203002492
Test: treehugger
Change-Id: Ic607f7f349e5b7c9bf66c25b7bd68f827da530d6
diff --git a/libc/bionic/preadv_pwritev.cpp b/libc/bionic/preadv_pwritev.cpp
new file mode 100644
index 0000000..e44d3a6
--- /dev/null
+++ b/libc/bionic/preadv_pwritev.cpp
@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/uio.h>
+
+// System calls we need.
+extern "C" int __preadv64(int, const struct iovec*, int, long, long);
+extern "C" int __preadv64v2(int, const struct iovec*, int, long, long, int);
+extern "C" int __pwritev64(int, const struct iovec*, int, long, long);
+extern "C" int __pwritev64v2(int, const struct iovec*, int, long, long, int);
+
+// There is no 32-bit off_t preadv/pwritev (even on LP32).
+// To avoid 32-bit ABI issues about which register pairs you're allowed
+// to pass 64-bit values in, the kernel just takes two `long` arguments --
+// which are int32_t for LP32, remember -- and stitches them together.
+// It even does this for LP64, taking a second unused always-zero `long`.
+// (The first long was int64_t, which is the same as off64_t.)
+// The pair is split lo-hi (not hi-lo, as llseek is).
+
+ssize_t preadv(int fd, const struct iovec* ios, int count, off_t offset) {
+ return preadv64(fd, ios, count, offset);
+}
+
+ssize_t preadv64(int fd, const struct iovec* ios, int count, off64_t offset) {
+#if defined(__LP64__)
+ return __preadv64(fd, ios, count, offset, 0);
+#else
+ return __preadv64(fd, ios, count, offset, offset >> 32);
+#endif
+}
+
+ssize_t pwritev(int fd, const struct iovec* ios, int count, off_t offset) {
+ return pwritev64(fd, ios, count, offset);
+}
+
+ssize_t pwritev64(int fd, const struct iovec* ios, int count, off64_t offset) {
+#if defined(__LP64__)
+ return __pwritev64(fd, ios, count, offset, 0);
+#else
+ return __pwritev64(fd, ios, count, offset, offset >> 32);
+#endif
+}
+
+ssize_t preadv2(int fd, const struct iovec* ios, int count, off_t offset, int flags) {
+ return preadv64v2(fd, ios, count, offset, flags);
+}
+
+ssize_t preadv64v2(int fd, const struct iovec* ios, int count, off64_t offset, int flags) {
+#if defined(__LP64__)
+ return __preadv64v2(fd, ios, count, offset, 0, flags);
+#else
+ return __preadv64v2(fd, ios, count, offset, offset >> 32, flags);
+#endif
+}
+
+ssize_t pwritev2(int fd, const struct iovec* ios, int count, off_t offset, int flags) {
+ return pwritev64v2(fd, ios, count, offset, flags);
+}
+
+ssize_t pwritev64v2(int fd, const struct iovec* ios, int count, off64_t offset, int flags) {
+#if defined(__LP64__)
+ return __pwritev64v2(fd, ios, count, offset, 0, flags);
+#else
+ return __pwritev64v2(fd, ios, count, offset, offset >> 32, flags);
+#endif
+}