/*

 * Copyright (c) 2014, 2017, 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 jdk.internal.jimage;

import java.io.UTFDataFormatException;

import java.nio.ByteBuffer;

import java.util.Objects;

/**

 * @implNote This class needs to maintain JDK 8 source compatibility.

 *

 * It is used internally in the JDK to implement jimage/jrtfs access,

 * but also compiled and delivered as part of the jrtfs.jar to support access

 * to the jimage file provided by the shipped JDK by tools running on JDK 8.

 */

public class ImageStringsReader implements ImageStrings {

    public static final int HASH_MULTIPLIER = 0x01000193;

    public static final int POSITIVE_MASK = 0x7FFFFFFF;

    private final BasicImageReader reader;

    ImageStringsReader(BasicImageReader reader) {

        this.reader = Objects.requireNonNull(reader);

    }

    @Override

    public String get(int offset) {

        return reader.getString(offset);

    }

    @Override

    public int add(final String string) {

        throw new InternalError("Can not add strings at runtime");

    }

    public static int hashCode(String s) {

        return hashCode(s, HASH_MULTIPLIER);

    }

    public static int hashCode(String s, int seed) {

        return unmaskedHashCode(s, seed) & POSITIVE_MASK;

    }

    public static int hashCode(String module, String name) {

        return hashCode(module, name, HASH_MULTIPLIER);

    }

    public static int hashCode(String module, String name, int seed) {

        seed = unmaskedHashCode("/", seed);

        seed = unmaskedHashCode(module, seed);

        seed = unmaskedHashCode("/", seed);

        seed = unmaskedHashCode(name, seed);

        return seed & POSITIVE_MASK;

    }

    public static int unmaskedHashCode(String s, int seed) {

        int slen = s.length();

        byte[] buffer = null;

        for (int i = 0; i < slen; i++) {

            char ch = s.charAt(i);

            int uch = ch & 0xFFFF;

            if ((uch & ~0x7F) != 0) {

                if (buffer == null) {

                    buffer = new byte[8];

                }

                int mask = ~0x3F;

                int n = 0;

                do {

                    buffer[n++] = (byte)(0x80 | (uch & 0x3F));

                    uch >>= 6;

                    mask >>= 1;

                } while ((uch & mask) != 0);

                buffer[n] = (byte)((mask << 1) | uch);

                do {

                    seed = (seed * HASH_MULTIPLIER) ^ (buffer[n--] & 0xFF);

                } while (0 <= n);

            } else if (uch == 0) {

                seed = (seed * HASH_MULTIPLIER) ^ (0xC0);

                seed = (seed * HASH_MULTIPLIER) ^ (0x80);

            } else {

                seed = (seed * HASH_MULTIPLIER) ^ (uch);

            }

        }

        return seed;

    }

    static int charsFromMUTF8Length(byte[] bytes, int offset, int count) {

        int length = 0;

        for (int i = offset; i < offset + count; i++) {

            byte ch = bytes[i];

            if (ch == 0) {

                break;

            }

            if ((ch & 0xC0) != 0x80) {

                length++;

            }

        }

        return length;

    }

    static void charsFromMUTF8(char[] chars, byte[] bytes, int offset, int count) throws UTFDataFormatException {

        int j = 0;

        for (int i = offset; i < offset + count; i++) {

            byte ch = bytes[i];

            if (ch == 0) {

                break;

            }

            boolean is_unicode = (ch & 0x80) != 0;

            int uch = ch & 0x7F;

            if (is_unicode) {

                int mask = 0x40;

                while ((uch & mask) != 0) {

                    ch = bytes[++i];

                    if ((ch & 0xC0) != 0x80) {

                        throw new UTFDataFormatException("bad continuation 0x" + Integer.toHexString(ch));

                    }

                    uch = ((uch & ~mask) << 6) | (ch & 0x3F);

                    mask <<= 6 - 1;

                }

                if ((uch & 0xFFFF) != uch) {

                    throw new UTFDataFormatException("character out of range \\u" + Integer.toHexString(uch));

                }

            }

            chars[j++] = (char)uch;

        }

    }

    public static String stringFromMUTF8(byte[] bytes, int offset, int count) {

        int length = charsFromMUTF8Length(bytes, offset, count);

        char[] chars = new char[length];

        try {

            charsFromMUTF8(chars, bytes, offset, count);

        } catch (UTFDataFormatException ex) {

            throw new InternalError("Attempt to convert non modified UTF-8 byte sequence", ex);

        }

        return new String(chars);

    }

    public static String stringFromMUTF8(byte[] bytes) {

        return stringFromMUTF8(bytes, 0, bytes.length);

    }

    static int charsFromByteBufferLength(ByteBuffer buffer) {

        int length = 0;

        while(buffer.hasRemaining()) {

            byte ch = buffer.get();

            if (ch == 0) {

                return length;

            }

            if ((ch & 0xC0) != 0x80) {

                length++;

            }

        }

        throw new InternalError("No terminating zero byte for modified UTF-8 byte sequence");

    }

    static void charsFromByteBuffer(char[] chars, ByteBuffer buffer) {

        int j = 0;

        while(buffer.hasRemaining()) {

            byte ch = buffer.get();

            if (ch == 0) {

                return;

            }

            boolean is_unicode = (ch & 0x80) != 0;

            int uch = ch & 0x7F;

            if (is_unicode) {

                int mask = 0x40;

                while ((uch & mask) != 0) {

                    ch = buffer.get();

                    if ((ch & 0xC0) != 0x80) {

                        throw new InternalError("Bad continuation in " +

                            "modified UTF-8 byte sequence: " + ch);

                    }

                    uch = ((uch & ~mask) << 6) | (ch & 0x3F);

                    mask <<= 6 - 1;

                }

            }

            if ((uch & 0xFFFF) != uch) {

                throw new InternalError("UTF-32 char in modified UTF-8 " +

                    "byte sequence: " + uch);

            }

            chars[j++] = (char)uch;

        }

        throw new InternalError("No terminating zero byte for modified UTF-8 byte sequence");

    }

    public static String stringFromByteBuffer(ByteBuffer buffer) {

        int length = charsFromByteBufferLength(buffer);

        buffer.rewind();

        char[] chars = new char[length];

        charsFromByteBuffer(chars, buffer);

        return new String(chars);

    }

    static int mutf8FromStringLength(String s) {

        int length = 0;

        int slen = s.length();

        for (int i = 0; i < slen; i++) {

            char ch = s.charAt(i);

            int uch = ch & 0xFFFF;

            if ((uch & ~0x7F) != 0) {

                int mask = ~0x3F;

                int n = 0;

                do {

                    n++;

                    uch >>= 6;

                    mask >>= 1;

                } while ((uch & mask) != 0);

                length += n + 1;

            } else if (uch == 0) {

                length += 2;

            } else {

                length++;

            }

        }

        return length;

    }

    static void mutf8FromString(byte[] bytes, int offset, String s) {

        int j = offset;

        byte[] buffer = null;

        int slen = s.length();

        for (int i = 0; i < slen; i++) {

            char ch = s.charAt(i);

            int uch = ch & 0xFFFF;

            if ((uch & ~0x7F) != 0) {

                if (buffer == null) {

                    buffer = new byte[8];

                }

                int mask = ~0x3F;

                int n = 0;

                do {

                    buffer[n++] = (byte)(0x80 | (uch & 0x3F));

                    uch >>= 6;

                    mask >>= 1;

                } while ((uch & mask) != 0);

                buffer[n] = (byte)((mask << 1) | uch);

                do {

                    bytes[j++] = buffer[n--];

                } while (0 <= n);

            } else if (uch == 0) {

                bytes[j++] = (byte)0xC0;

                bytes[j++] = (byte)0x80;

            } else {

                bytes[j++] = (byte)uch;

            }

        }

    }

    public static byte[] mutf8FromString(String string) {

        int length = mutf8FromStringLength(string);

        byte[] bytes = new byte[length];

        mutf8FromString(bytes, 0, string);

        return bytes;

    }

}