/*-------------------------------------------------------------------------
*
* Copyright (c) 2003-2008, PostgreSQL Global Development Group
*
* IDENTIFICATION
*   $PostgreSQL: pgjdbc/org/postgresql/util/PGbytea.java,v 1.17 2010/04/06 23:45:09 jurka Exp $
*
*-------------------------------------------------------------------------
*/
package org.teiid.transport.pg;

import java.sql.SQLException;

/**
 * Converts to and from the postgresql bytea datatype used by the backend.
 */
public class PGbytea
{
    private static final int MAX_3_BUFF_SIZE = 2 * 1024 * 1024;

    /*
     * Converts a PG bytea raw value (i.e. the raw binary representation
     * of the bytea data type) into a java byte[]
     */
    public static byte[] toBytes(byte[] s) throws SQLException
    {
        if (s == null)
            return null;

        // Starting with PG 9.0, a new hex format is supported
        // that starts with "\x".  Figure out which format we're
        // dealing with here.
        //
        if (s.length < 2 || s[0] != '\\' || s[1] != 'x') {
            return toBytesOctalEscaped(s);
        }
        return toBytesHexEscaped(s);
    }

    private static byte[] toBytesHexEscaped(byte[] s)
    {
        byte[] output = new byte[(s.length - 2) / 2];
        for (int i=0; i<output.length; i++) {
            byte b1 = gethex(s[2 + i*2]);
            byte b2 = gethex(s[2 + i*2 + 1]);
            output[i] = (byte)((b1 << 4) | b2);
        }
        return output;
    }

    private static byte gethex(byte b) {
        // 0-9 == 48-57
        if (b <= 57)
            return (byte)(b - 48);

        // a-f == 97-102
        if (b >= 97)
            return (byte)(b - 97 + 10);

        // A-F == 65-70
        return (byte)(b - 65 + 10);
    }

    private static byte[] toBytesOctalEscaped(byte[] s)
    {
        final int slength = s.length;
        byte[] buf = null;
        int correctSize = slength;
        if (slength > MAX_3_BUFF_SIZE)
        {
            // count backslash escapes, they will be either
            // backslashes or an octal escape \\ or \003
            //
            for (int i = 0; i < slength; ++i)
            {
                byte current = s[i];
                if (current == '\\')
                {
                    byte next = s[ ++i ];
                    if (next == '\\')
                    {
                        --correctSize;
                    }
                    else
                    {
                        correctSize -= 3;
                    }
                }
            }
            buf = new byte[correctSize];
        }
        else
        {
            buf = new byte[slength];
        }
        int bufpos = 0;
        int thebyte;
        byte nextbyte;
        byte secondbyte;
        for (int i = 0; i < slength; i++)
        {
            nextbyte = s[i];
            if (nextbyte == (byte)'\\')
            {
                secondbyte = s[++i];
                if (secondbyte == (byte)'\\')
                {
                    //escaped \
                    buf[bufpos++] = (byte)'\\';
                }
                else
                {
                    thebyte = (secondbyte - 48) * 64 + (s[++i] - 48) * 8 + (s[++i] - 48);
                    if (thebyte > 127)
                        thebyte -= 256;
                    buf[bufpos++] = (byte)thebyte;
                }
            }
            else
            {
                buf[bufpos++] = nextbyte;
            }
        }
        if (bufpos == correctSize)
        {
            return buf;
        }
        byte[] l_return = new byte[bufpos];
        System.arraycopy(buf, 0, l_return, 0, bufpos);
        return l_return;
    }

    /*
     * Converts a java byte[] into a PG bytea string (i.e. the text
     * representation of the bytea data type)
     */
    public static String toPGString(byte[] p_buf) throws SQLException
    {
        if (p_buf == null)
            return null;
        StringBuffer l_strbuf = new StringBuffer(2 * p_buf.length);
        for (int i = 0; i < p_buf.length; i++)
        {
            int l_int = (int)p_buf[i];
            if (l_int < 0)
            {
                l_int = 256 + l_int;
            }
            //we escape the same non-printable characters as the backend
            //we must escape all 8bit characters otherwise when convering
            //from java unicode to the db character set we may end up with
            //question marks if the character set is SQL_ASCII
            if (l_int < 040 || l_int > 0176)
            {
                //escape charcter with the form \000, but need two \\ because of
                //the Java parser
                l_strbuf.append("\\");
                l_strbuf.append((char)(((l_int >> 6) & 0x3) + 48));
                l_strbuf.append((char)(((l_int >> 3) & 0x7) + 48));
                l_strbuf.append((char)((l_int & 0x07) + 48));
            }
            else if (p_buf[i] == (byte)'\\')
            {
                //escape the backslash character as \\, but need four \\\\ because
                //of the Java parser
                l_strbuf.append("\\\\");
            }
            else
            {
                //other characters are left alone
                l_strbuf.append((char)p_buf[i]);
            }
        }
        return l_strbuf.toString();
    }
}