LibC: Implement `readv` and `writev`

userspace/libraries/LibC/CMakeLists.txt

@@ -39,6 +39,7 @@ set(LIBC_SOURCES
 	sys/stat.cpp
 	sys/statvfs.cpp
 	sys/time.cpp
+	sys/uio.cpp
 	sys/utsname.cpp
 	sys/wait.cpp
 	syslog.cpp

userspace/libraries/LibC/sys/uio.cpp

@@ -0,0 +1,46 @@
+#include <sys/uio.h>
+#include <unistd.h>
+
+ssize_t readv(int fildes, const struct iovec* iov, int iovcnt)
+{
+	size_t result = 0;
+	for (int i = 0; i < iovcnt; i++)
+	{
+		uint8_t* base = static_cast<uint8_t*>(iov->iov_base);
+
+		size_t nread = 0;
+		while (nread < iov[i].iov_len)
+		{
+			const ssize_t ret = read(fildes, base + nread, iov[i].iov_len - nread);
+			if (ret == -1 && result == 0)
+				return -1;
+			if (ret <= 0)
+				return result;
+			nread += ret;
+		}
+		result += nread;
+	}
+	return result;
+}
+
+ssize_t writev(int fildes, const struct iovec* iov, int iovcnt)
+{
+	size_t result = 0;
+	for (int i = 0; i < iovcnt; i++)
+	{
+		const uint8_t* base = static_cast<const uint8_t*>(iov->iov_base);
+
+		size_t nwrite = 0;
+		while (nwrite < iov[i].iov_len)
+		{
+			const ssize_t ret = write(fildes, base + nwrite, iov[i].iov_len - nwrite);
+			if (ret == -1 && result == 0)
+				return -1;
+			if (ret <= 0)
+				return result;
+			nwrite += ret;
+		}
+		result += nwrite;
+	}
+	return result;
+}