/*

 * Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.nio.ch;

import java.io.FileDescriptor;

import java.io.IOException;

import java.nio.ByteBuffer;

/**

 * File-descriptor based I/O utilities that are shared by NIO classes.

 */

public class IOUtil {

    /**

     * Max number of iovec structures that readv/writev supports

     */

    static final int IOV_MAX;

    private IOUtil() { }                // No instantiation

    static int write(FileDescriptor fd, ByteBuffer src, long position,

                     NativeDispatcher nd)

        throws IOException

    {

        if (src instanceof DirectBuffer)

            return writeFromNativeBuffer(fd, src, position, nd);

        // Substitute a native buffer

        int pos = src.position();

        int lim = src.limit();

        assert (pos <= lim);

        int rem = (pos <= lim ? lim - pos : 0);

        ByteBuffer bb = Util.getTemporaryDirectBuffer(rem);

        try {

            bb.put(src);

            bb.flip();

            // Do not update src until we see how many bytes were written

            src.position(pos);

            int n = writeFromNativeBuffer(fd, bb, position, nd);

            if (n > 0) {

                // now update src

                src.position(pos + n);

            }

            return n;

        } finally {

            Util.offerFirstTemporaryDirectBuffer(bb);

        }

    }

    private static int writeFromNativeBuffer(FileDescriptor fd, ByteBuffer bb,

                                             long position, NativeDispatcher nd)

        throws IOException

    {

        int pos = bb.position();

        int lim = bb.limit();

        assert (pos <= lim);

        int rem = (pos <= lim ? lim - pos : 0);

        int written = 0;

        if (rem == 0)

            return 0;

        if (position != -1) {

            written = nd.pwrite(fd,

                                ((DirectBuffer)bb).address() + pos,

                                rem, position);

        } else {

            written = nd.write(fd, ((DirectBuffer)bb).address() + pos, rem);

        }

        if (written > 0)

            bb.position(pos + written);

        return written;

    }

    static long write(FileDescriptor fd, ByteBuffer[] bufs, NativeDispatcher nd)

        throws IOException

    {

        return write(fd, bufs, 0, bufs.length, nd);

    }

    static long write(FileDescriptor fd, ByteBuffer[] bufs, int offset, int length,

                      NativeDispatcher nd)

        throws IOException

    {

        IOVecWrapper vec = IOVecWrapper.get(length);

        boolean completed = false;

        int iov_len = 0;

        try {

            // Iterate over buffers to populate native iovec array.

            int count = offset + length;

            int i = offset;

            while (i < count && iov_len < IOV_MAX) {

                ByteBuffer buf = bufs[i];

                int pos = buf.position();

                int lim = buf.limit();

                assert (pos <= lim);

                int rem = (pos <= lim ? lim - pos : 0);

                if (rem > 0) {

                    vec.setBuffer(iov_len, buf, pos, rem);

                    // allocate shadow buffer to ensure I/O is done with direct buffer

                    if (!(buf instanceof DirectBuffer)) {

                        ByteBuffer shadow = Util.getTemporaryDirectBuffer(rem);

                        shadow.put(buf);

                        shadow.flip();

                        vec.setShadow(iov_len, shadow);

                        buf.position(pos);  // temporarily restore position in user buffer

                        buf = shadow;

                        pos = shadow.position();

                    }

                    vec.putBase(iov_len, ((DirectBuffer)buf).address() + pos);

                    vec.putLen(iov_len, rem);

                    iov_len++;

                }

                i++;

            }

            if (iov_len == 0)

                return 0L;

            long bytesWritten = nd.writev(fd, vec.address, iov_len);

            // Notify the buffers how many bytes were taken

            long left = bytesWritten;

            for (int j=0; j<iov_len; j++) {

                if (left > 0) {

                    ByteBuffer buf = vec.getBuffer(j);

                    int pos = vec.getPosition(j);

                    int rem = vec.getRemaining(j);

                    int n = (left > rem) ? rem : (int)left;

                    buf.position(pos + n);

                    left -= n;

                }

                // return shadow buffers to buffer pool

                ByteBuffer shadow = vec.getShadow(j);

                if (shadow != null)

                    Util.offerLastTemporaryDirectBuffer(shadow);

                vec.clearRefs(j);

            }

            completed = true;

            return bytesWritten;

        } finally {

            // if an error occurred then clear refs to buffers and return any shadow

            // buffers to cache

            if (!completed) {

                for (int j=0; j<iov_len; j++) {

                    ByteBuffer shadow = vec.getShadow(j);

                    if (shadow != null)

                        Util.offerLastTemporaryDirectBuffer(shadow);

                    vec.clearRefs(j);

                }

            }

        }

    }

    static int read(FileDescriptor fd, ByteBuffer dst, long position,

                    NativeDispatcher nd)

        throws IOException

    {

        if (dst.isReadOnly())

            throw new IllegalArgumentException("Read-only buffer");

        if (dst instanceof DirectBuffer)

            return readIntoNativeBuffer(fd, dst, position, nd);

        // Substitute a native buffer

        ByteBuffer bb = Util.getTemporaryDirectBuffer(dst.remaining());

        try {

            int n = readIntoNativeBuffer(fd, bb, position, nd);

            bb.flip();

            if (n > 0)

                dst.put(bb);

            return n;

        } finally {

            Util.offerFirstTemporaryDirectBuffer(bb);

        }

    }

    private static int readIntoNativeBuffer(FileDescriptor fd, ByteBuffer bb,

                                            long position, NativeDispatcher nd)

        throws IOException

    {

        int pos = bb.position();

        int lim = bb.limit();

        assert (pos <= lim);

        int rem = (pos <= lim ? lim - pos : 0);

        if (rem == 0)

            return 0;

        int n = 0;

        if (position != -1) {

            n = nd.pread(fd, ((DirectBuffer)bb).address() + pos,

                         rem, position);

        } else {

            n = nd.read(fd, ((DirectBuffer)bb).address() + pos, rem);

        }

        if (n > 0)

            bb.position(pos + n);

        return n;

    }

    static long read(FileDescriptor fd, ByteBuffer[] bufs, NativeDispatcher nd)

        throws IOException

    {

        return read(fd, bufs, 0, bufs.length, nd);

    }

    static long read(FileDescriptor fd, ByteBuffer[] bufs, int offset, int length,

                     NativeDispatcher nd)

        throws IOException

    {

        IOVecWrapper vec = IOVecWrapper.get(length);

        boolean completed = false;

        int iov_len = 0;

        try {

            // Iterate over buffers to populate native iovec array.

            int count = offset + length;

            int i = offset;

            while (i < count && iov_len < IOV_MAX) {

                ByteBuffer buf = bufs[i];

                if (buf.isReadOnly())

                    throw new IllegalArgumentException("Read-only buffer");

                int pos = buf.position();

                int lim = buf.limit();

                assert (pos <= lim);

                int rem = (pos <= lim ? lim - pos : 0);

                if (rem > 0) {

                    vec.setBuffer(iov_len, buf, pos, rem);

                    // allocate shadow buffer to ensure I/O is done with direct buffer

                    if (!(buf instanceof DirectBuffer)) {

                        ByteBuffer shadow = Util.getTemporaryDirectBuffer(rem);

                        vec.setShadow(iov_len, shadow);

                        buf = shadow;

                        pos = shadow.position();

                    }

                    vec.putBase(iov_len, ((DirectBuffer)buf).address() + pos);

                    vec.putLen(iov_len, rem);

                    iov_len++;

                }

                i++;

            }

            if (iov_len == 0)

                return 0L;

            long bytesRead = nd.readv(fd, vec.address, iov_len);

            // Notify the buffers how many bytes were read

            long left = bytesRead;

            for (int j=0; j<iov_len; j++) {

                ByteBuffer shadow = vec.getShadow(j);

                if (left > 0) {

                    ByteBuffer buf = vec.getBuffer(j);

                    int rem = vec.getRemaining(j);

                    int n = (left > rem) ? rem : (int)left;

                    if (shadow == null) {

                        int pos = vec.getPosition(j);

                        buf.position(pos + n);

                    } else {

                        shadow.limit(shadow.position() + n);

                        buf.put(shadow);

                    }

                    left -= n;

                }

                if (shadow != null)

                    Util.offerLastTemporaryDirectBuffer(shadow);

                vec.clearRefs(j);

            }

            completed = true;

            return bytesRead;

        } finally {

            // if an error occurred then clear refs to buffers and return any shadow

            // buffers to cache

            if (!completed) {

                for (int j=0; j<iov_len; j++) {

                    ByteBuffer shadow = vec.getShadow(j);

                    if (shadow != null)

                        Util.offerLastTemporaryDirectBuffer(shadow);

                    vec.clearRefs(j);

                }

            }

        }

    }

    public static FileDescriptor newFD(int i) {

        FileDescriptor fd = new FileDescriptor();

        setfdVal(fd, i);

        return fd;

    }

    static native boolean randomBytes(byte[] someBytes);

    /**

     * Returns two file descriptors for a pipe encoded in a long.

     * The read end of the pipe is returned in the high 32 bits,

     * while the write end is returned in the low 32 bits.

     */

    static native long makePipe(boolean blocking);

    static native boolean drain(int fd) throws IOException;

    public static native void configureBlocking(FileDescriptor fd,

                                                boolean blocking)

        throws IOException;

    public static native int fdVal(FileDescriptor fd);

    static native void setfdVal(FileDescriptor fd, int value);

    static native int fdLimit();

    static native int iovMax();

    static native void initIDs();

    static {

        IOV_MAX = iovMax();

    }

}