/**
*******************************************************************************
* Copyright (C) 2006, International Business Machines Corporation and    *
* others. All Rights Reserved.                                                *
*******************************************************************************
*
*******************************************************************************
*/ 
package com.ibm.icu.charset;

import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.IntBuffer;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CoderResult;

import com.ibm.icu.lang.UCharacter;
import com.ibm.icu.text.UTF16;

class CharsetASCII extends CharsetICU {
    protected byte[] fromUSubstitution = new byte[]{(byte)0x1a};
    
    public CharsetASCII(String icuCanonicalName, String javaCanonicalName, String[] aliases){
        super(icuCanonicalName, javaCanonicalName, aliases);
        maxBytesPerChar = 1;
        minBytesPerChar = 1;
        maxCharsPerByte = 1;
    }
    class CharsetDecoderASCII extends CharsetDecoderICU{

        public CharsetDecoderASCII(CharsetICU cs) {
            super(cs);
        }

        protected CoderResult decodeLoop(ByteBuffer source, CharBuffer target, IntBuffer offsets, boolean flush){
            CoderResult cr = CoderResult.UNDERFLOW;
            if(!source.hasRemaining() && toUnicodeStatus==0) {
                /* no input, nothing to do */
                return cr;
            }
            if(!target.hasRemaining()) {
                return CoderResult.OVERFLOW;
            }
        
            int sourceArrayIndex=source.position(), count=0;
            int sourceIndex = 0;
            char c=0;
            int oldTarget = target.position();

            /* conversion loop */
            c=0;
            while(sourceArrayIndex<source.limit()&&
                    (c=(char)source.get(sourceArrayIndex))<=0x7f &&
                    target.hasRemaining()){
                target.put(c);    
                sourceArrayIndex++;
            }

            if(c>0x7f) {
                /* callback(illegal); copy the current bytes to toUBytes[] */
                toUBytesArray[0]=(byte)c;
                toULength=1;
                cr = CoderResult.malformedForLength(toULength);
            } else if(sourceArrayIndex<source.limit() && !target.hasRemaining()) {
                /* target is full */
                cr = CoderResult.OVERFLOW;
            }

            /* set offsets since the start */
            if(offsets!=null) {
                count=target.position()-oldTarget;
                while(count>0) {
                    offsets.put(sourceIndex++);
                    --count;
                }
            }
            source.position(sourceArrayIndex);
            return cr;
        }
        
    }
    class CharsetEncoderASCII extends CharsetEncoderICU{

        public CharsetEncoderASCII(CharsetICU cs) {
            super(cs, fromUSubstitution);
            implReset();
        }

        private final static int NEED_TO_WRITE_BOM = 1;
        
        protected void implReset() {
            super.implReset();
            fromUnicodeStatus = NEED_TO_WRITE_BOM;
        }
        
        protected CoderResult encodeLoop(CharBuffer source, ByteBuffer target, IntBuffer offsets, boolean flush){
            CoderResult cr = CoderResult.UNDERFLOW;
            if(!source.hasRemaining()) {
                /* no input, nothing to do */
                return cr;
            }
            
            if(!target.hasRemaining()) {
                return CoderResult.OVERFLOW;
            }
            
            int sourceArrayIndex=source.position(), count=0;
            int sourceIndex = 0;
            int ch=0;
            int oldTarget = target.position();
            boolean doloop = true;
            
            if (fromUChar32 != 0 && target.hasRemaining()){
                ch = fromUChar32;
                fromUChar32 = 0;
                       
                if (sourceArrayIndex < source.limit()) {
                    /* test the following code unit */
                    char trail = source.get(sourceArrayIndex);
                    if(UTF16.isTrailSurrogate(trail)) {
                        ++sourceArrayIndex;
                        ch = UCharacter.getCodePoint((char)ch, trail);
                        /* convert this supplementary code point */
                        /* callback(unassigned) */
                        cr = CoderResult.unmappableForLength(sourceArrayIndex);
                        doloop = false;
                    } else {
                        /* this is an unmatched lead code unit (1st surrogate) */
                        /* callback(illegal) */
                        fromUChar32 = (int)ch;
                        cr = CoderResult.malformedForLength(sourceArrayIndex);
                        doloop = false;
                    }
                } else {
                    /* no more input */
                    fromUChar32 = (int)ch;
                    doloop = false;
                }                            
            }
            if(doloop){
                /* conversion loop */
                ch=0;
                int ch2=0;
                while(sourceArrayIndex<source.limit()){
                    ch=source.get(sourceArrayIndex++);
                    if(ch<=0xff) {
                        if(target.hasRemaining()){
                            target.put((byte)ch);
                        }else{
                            cr = CoderResult.OVERFLOW;
                            break;
                        }
                    }else {
                        if (UTF16.isSurrogate((char)ch)) {
                            if (UTF16.isLeadSurrogate((char)ch)) {
                                //lowsurogate:
                                if (sourceArrayIndex < source.limit()) {
                                    ch2 = source.get(sourceArrayIndex);
                                    if (UTF16.isTrailSurrogate((char)ch2)) {
                                        ch = ((ch - UConverterSharedData.SURROGATE_HIGH_START) << UConverterSharedData.HALF_SHIFT) + ch2 + UConverterSharedData.SURROGATE_LOW_BASE;
                                        sourceArrayIndex++;
                                    }
                                    else {
                                        /* this is an unmatched trail code unit (2nd surrogate) */
                                        /* callback(illegal) */
                                        fromUChar32 = ch;
                                        cr = CoderResult.OVERFLOW;
                                        break;
                                    }
                                }
                                else {
                                    /* ran out of source */
                                    fromUChar32 = ch;
                                    if (flush) {
                                        /* this is an unmatched trail code unit (2nd surrogate) */
                                        /* callback(illegal) */
                                        cr = CoderResult.malformedForLength(sourceArrayIndex);
                                    }
                                    break;
                                }
                            }
                        }
                        fromUChar32 = ch;
                        cr = CoderResult.malformedForLength(sourceArrayIndex);
                        break;                            
                    }
                }
            }
            /* set offsets since the start */
            if(offsets!=null) {
                count=target.position()-oldTarget;
                while(count>0) {
                    offsets.put(sourceIndex++);
                    --count;
                }
            } 

            source.position(sourceArrayIndex);
            return cr;
        }
    }
    public CharsetDecoder newDecoder() {
        return new CharsetDecoderASCII(this);
    }

    public CharsetEncoder newEncoder() {
        return new CharsetEncoderASCII(this);
    }

}