user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/options/posix/generic/sys-uio.cpp

@@ -0,0 +1,80 @@
+
+#include <sys/uio.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <limits.h>
+
+#include <frg/vector.hpp>
+#include <mlibc/allocator.hpp>
+#include <mlibc/debug.hpp>
+#include <mlibc/posix-sysdeps.hpp>
+#include <bits/ensure.h>
+
+ssize_t readv(int fd, const struct iovec *iovs, int iovc) {
+	ssize_t read_bytes = 0;
+
+	auto sysdep = MLIBC_CHECK_OR_ENOSYS(mlibc::sys_readv, -1);
+
+	if (int e = sysdep(fd, iovs, iovc, &read_bytes); e) {
+		errno = e;
+		return -1;
+	}
+
+	return read_bytes;
+}
+
+ssize_t writev(int fd, const struct iovec *iovs, int iovc) {
+	__ensure(iovc);
+
+	ssize_t written = 0;
+
+	auto sysdep = mlibc::sys_writev;
+	if(sysdep) {
+		int e = sysdep(fd, iovs, iovc, &written);
+		if(e) {
+			errno = e;
+			return -1;
+		}
+		return written;
+	}
+
+	// TODO: this implementation is not safe to use in signal contexts
+	mlibc::infoLogger() << "mlibc: falling back to signal-unsafe writev implementation!" << frg::endlog;
+	size_t bytes = 0;
+	for(int i = 0; i < iovc; i++) {
+		if(SSIZE_MAX - bytes < iovs[i].iov_len) {
+			errno = EINVAL;
+			return -1;
+		}
+		bytes += iovs[i].iov_len;
+	}
+	frg::vector<char, MemoryAllocator> buffer{getAllocator()};
+	buffer.resize(bytes);
+
+	size_t to_copy = bytes;
+	char *bp = buffer.data();
+	for(int i = 0; i < iovc; i++) {
+		size_t copy = frg::min(iovs[i].iov_len, to_copy);
+
+		bp = (char *)mempcpy((void *)bp, (void *)iovs[i].iov_base, copy);
+
+		to_copy -= copy;
+		if(to_copy == 0)
+			break;
+	}
+
+	written = write(fd, buffer.data(), bytes);
+	return written;
+}
+
+ssize_t preadv(int, const struct iovec *, int, off_t) {
+	__ensure(!"Not implemented");
+	__builtin_unreachable();
+}
+
+ssize_t pwritev(int, const struct iovec *, int, off_t) {
+	__ensure(!"Not implemented");
+	__builtin_unreachable();
+}