/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2000, 2010 Oracle and/or its affiliates.  All rights reserved.
 *
 */

package com.sleepycat.util;

/**
 * UTF operations with more flexibility than is provided by DataInput and
 * DataOutput.
 *
 * @author Mark Hayes
 */
public class UtfOps {

    private static byte[] EMPTY_BYTES = {};
    private static String EMPTY_STRING = "";

    /**
     * Returns the byte length of a null terminated UTF string, not including
     * the terminator.
     *
     * @param bytes the data containing the UTF string.
     *
     * @param offset the beginning of the string the measure.
     *
     * @throws IndexOutOfBoundsException if no zero terminator is found.
     *
     * @return the number of bytes.
     */
    public static int getZeroTerminatedByteLength(byte[] bytes, int offset)
        throws IndexOutOfBoundsException {

        int len = 0;
        while (bytes[offset++] != 0) {
            len++;
        }
        return len;
    }

    /**
     * Returns the byte length of the UTF string that would be created by
     * converting the given characters to UTF.
     *
     * @param chars the characters that would be converted.
     *
     * @return the byte length of the equivalent UTF data.
     */
    public static int getByteLength(char[] chars) {

        return getByteLength(chars, 0, chars.length);
    }

    /**
     * Returns the byte length of the UTF string that would be created by
     * converting the given characters to UTF.
     *
     * @param chars the characters that would be converted.
     *
     * @param offset the first character to be converted.
     *
     * @param length the number of characters to be converted.
     *
     * @return the byte length of the equivalent UTF data.
     */
    public static int getByteLength(char[] chars, int offset, int length) {

        int len = 0;
        length += offset;
        for (int i = offset; i < length; i++) {
            int c = chars[i];
            if ((c >= 0x0001) && (c <= 0x007F)) {
                len++;
            } else if (c > 0x07FF) {
                len += 3;
            } else {
                len += 2;
            }
        }
        return len;
    }

    /**
     * Returns the number of characters represented by the given UTF string.
     *
     * @param bytes the UTF string.
     *
     * @return the number of characters.
     *
     * @throws IndexOutOfBoundsException if a UTF character sequence at the end
     * of the data is not complete.
     *
     * @throws IllegalArgumentException if an illegal UTF sequence is
     * encountered.
     */
    public static int getCharLength(byte[] bytes)
        throws IllegalArgumentException, IndexOutOfBoundsException {

        return getCharLength(bytes, 0, bytes.length);
    }

    /**
     * Returns the number of characters represented by the given UTF string.
     *
     * @param bytes the data containing the UTF string.
     *
     * @param offset the first byte to be converted.
     *
     * @param length the number of byte to be converted.
     *
     * @throws IndexOutOfBoundsException if a UTF character sequence at the end
     * of the data is not complete.
     *
     * @throws IllegalArgumentException if an illegal UTF sequence is
     * encountered.
     */
    public static int getCharLength(byte[] bytes, int offset, int length)
        throws IllegalArgumentException, IndexOutOfBoundsException {

        int charCount = 0;
        length += offset;
        while (offset < length) {
            switch ((bytes[offset] & 0xff) >> 4) {
            case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
                offset++;
                break;
            case 12: case 13:
                offset += 2;
                break;
            case 14:
                offset += 3;
                break;
            default:
                throw new IllegalArgumentException();
            }
            charCount++;
        }
        return charCount;
    }

    /**
     * Converts byte arrays into character arrays.
     *
     * @param bytes the source byte data to convert
     *
     * @param byteOffset the offset into the byte array at which
     * to start the conversion
     *
     * @param chars the destination array
     *
     * @param charOffset the offset into chars at which to begin the copy
     *
     * @param len the amount of information to copy into chars
     *
     * @param isByteLen if true then len is a measure of bytes, otherwise
     * len is a measure of characters
     *
     * @throws IndexOutOfBoundsException if a UTF character sequence at the end
     * of the data is not complete.
     *
     * @throws IllegalArgumentException if an illegal UTF sequence is
     * encountered.
     */
    public static int bytesToChars(byte[] bytes, int byteOffset,
                                   char[] chars, int charOffset,
                                   int len, boolean isByteLen)
        throws IllegalArgumentException, IndexOutOfBoundsException {

        int char1, char2, char3;
        len += isByteLen ? byteOffset : charOffset;
        while ((isByteLen ? byteOffset : charOffset) < len) {
            char1 = bytes[byteOffset++] & 0xff;
            switch ((char1 & 0xff) >> 4) {
            case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
                chars[charOffset++] = (char) char1;
                break;
            case 12: case 13:
                char2 = bytes[byteOffset++];
                if ((char2 & 0xC0) != 0x80) {
                    throw new IllegalArgumentException();
                }
                chars[charOffset++] = (char)(((char1 & 0x1F) << 6) |
                                             (char2 & 0x3F));
                break;
            case 14:
                char2 = bytes[byteOffset++];
                char3 = bytes[byteOffset++];
                if (((char2 & 0xC0) != 0x80) || ((char3 & 0xC0) != 0x80))
                    throw new IllegalArgumentException();
                chars[charOffset++] = (char)(((char1 & 0x0F) << 12) |
                                             ((char2 & 0x3F) << 6)  |
                                             ((char3 & 0x3F) << 0));
                break;
            default:
                throw new IllegalArgumentException();
            }
        }
        return byteOffset;
    }

    /**
     * Converts character arrays into byte arrays.
     *
     * @param chars the source character data to convert
     *
     * @param charOffset the offset into the character array at which
     * to start the conversion
     *
     * @param bytes the destination array
     *
     * @param byteOffset the offset into bytes at which to begin the copy
     *
     * @param charLength the length of characters to copy into bytes
     */
    public static void charsToBytes(char[] chars, int charOffset,
                                    byte[] bytes, int byteOffset,
                                    int charLength) {
        charLength += charOffset;
        for (int i = charOffset; i < charLength; i++) {
            int c = chars[i];
            if ((c >= 0x0001) && (c <= 0x007F)) {
                bytes[byteOffset++] = (byte) c;
            } else if (c > 0x07FF) {
                bytes[byteOffset++] = (byte) (0xE0 | ((c >> 12) & 0x0F));
                bytes[byteOffset++] = (byte) (0x80 | ((c >>  6) & 0x3F));
                bytes[byteOffset++] = (byte) (0x80 | ((c >>  0) & 0x3F));
            } else {
                bytes[byteOffset++] = (byte) (0xC0 | ((c >>  6) & 0x1F));
                bytes[byteOffset++] = (byte) (0x80 | ((c >>  0) & 0x3F));
            }
        }
    }

    /**
     * Converts byte arrays into strings.
     *
     * @param bytes the source byte data to convert
     *
     * @param offset the offset into the byte array at which
     * to start the conversion
     *
     * @param length the number of bytes to be converted.
     *
     * @return the string.
     *
     * @throws IndexOutOfBoundsException if a UTF character sequence at the end
     * of the data is not complete.
     *
     * @throws IllegalArgumentException if an illegal UTF sequence is
     * encountered.
     */
    public static String bytesToString(byte[] bytes, int offset, int length)
        throws IllegalArgumentException, IndexOutOfBoundsException {

        if (length == 0) return EMPTY_STRING;
        int charLen = UtfOps.getCharLength(bytes, offset, length);
        char[] chars = new char[charLen];
        UtfOps.bytesToChars(bytes, offset, chars, 0, length, true);
        return new String(chars, 0, charLen);
    }

    /**
     * Converts strings to byte arrays.
     *
     * @param string the string to convert.
     *
     * @return the UTF byte array.
     */
    public static byte[] stringToBytes(String string) {

        if (string.length() == 0) return EMPTY_BYTES;
        char[] chars = string.toCharArray();
        byte[] bytes = new byte[UtfOps.getByteLength(chars)];
        UtfOps.charsToBytes(chars, 0, bytes, 0, chars.length);
        return bytes;
    }
}