/* --COPYRIGHT--,EPL
 *  Copyright (c) 2008 Texas Instruments and others.
 *  All rights reserved. This program and the accompanying materials
 *  are made available under the terms of the Eclipse Public License v1.0
 *  which accompanies this distribution, and is available at
 *  http://www.eclipse.org/legal/epl-v10.html
 * 
 *  Contributors:
 *      Texas Instruments - initial implementation
 * 
 * --/COPYRIGHT--*/

/*
 *  ======== Decoder.java ========  
 */
package xdc.rta;

import xdc.rov.TargetDecoder;
import xdc.rov.TargetEncoder;

/*
 *  ======== Decoder ========
 *  This class decodes xdc.runtime.Log.Event records from raw target bytes.
 *  The records are decoded into HostEvent objects from which the event message
 *  can be retrieved.
 *  
 *  The Decoder requires a MetaData object to provide information about the
 *  target used for decoding the raw bytes, as well as for retrieving the
 *  mapping of event ids to messages. See xdc.rta.MetaData.
 *  
 */
public class Decoder
{   
    private TargetDecoder targDecoder;
    private TargetEncoder targEncoder;
    
    private MetaData meta = null;
    
    /*
     *  ======== Decoder ========
     *  If the Decoder is constructed with a MetaData instance, then it is
     *  initialized and ready to go.
     */
    public Decoder(MetaData meta)
    {
        init(meta);
    }
    
    /*
     *  ======== Decoder ========
     *  No-argument constructor.
     *
     *  If the Decoder is constructed with no arguments, it must be initialized
     *  using one of the 'parse' APIs before decoding any records.
     */
    public Decoder()
    {
    }

    /*
     *  ======== init ========
     *  Initializes the decoder for use. The Decoder can be initialized by
     *  either passing a MetaData instance to the constructor or by using one
     *  of the parse APIs. This API contains the common initialization code.
     */
    private void init(MetaData meta)
    {
        this.meta = meta;
        
        /* 
         * Create the underlying target decoder and encoder for working with
         * target bytes. 
         */
        targDecoder = new TargetDecoder(meta.getEndianess(), 
                                        meta.getBitsPerChar());
        targEncoder = new TargetEncoder(meta.getEndianess(), 
                                        meta.getBitsPerChar());
    }
    
    /*
     *  ======== getXMLFromExec ========
     *  Retrieves the path to a given application's RTA XML file.
     */
    public static String getXMLFromExec(String executable) throws Exception
    {
        return (MetaData.getXMLFromExec(executable));
    }
    
    /*
     *  ======== getTargetEventRecSize ========
     *  Returns the record size in bytes (not MAUs).
     */
    public int getTargetEventRecSize()
    {
        return (this.meta == null ? 0 : this.meta.getTargetEventRecSize());
    }

    /*
     *   ======== parseFromExec ========
     *   Initializes the Decoder for the given executable.
     */
    public String parseFromExec(String executable) throws Exception
    {
        MetaData nMeta = new MetaData();
        
        String result = nMeta.parseFromExec(executable);
        
        if (result == "") {
            init(nMeta);
        }
        
        return (result);
    }    
    
    /*
     *  ======== parse ========
     *  Initializes the Decoder for 'executable' given the path
     *  to the RTA XML file.
     */
    public String parse(String xmlFile, String executable)
    {
        MetaData nMeta = new MetaData();
        
        String result = nMeta.parse(xmlFile, executable);
        
        if (result == "") {
            init(nMeta);
        }
        
        return (result);
    }
    
    /*
     *  ======== apply ========
     *  Decodes the raw target bytes of a single event record into a HostEvent.
     */
    public HostEvent apply(byte targetEventRec[])
    {
        return (apply(targetEventRec, 0));
    }
    
    /*
     *  ======== apply ========
     *  Decodes the raw target bytes of a single event record at the given
     *  offset. Returns a HostEvent object.
     */
    public HostEvent apply(byte targetEventRec[], int offset)
    {
        /* Create a host event object to store the decoded event. */
        HostEvent res = new HostEvent(meta);
        
        /* 
         * Maintain a running offset into the buffer--update 'off' after 
         * reading each field of the record. 
         * 
         * The sizes of each field are the same across all targets, except
         * for the arguments, which are of type IArg.
         * 
         * struct EventRec {
         *   Bits32 ts_hi;
         *   Bits32 ts_lo;
         *   Bits32 serial;
         *   Bits32 evt; 
         *   IArg arg[NUMARGS];
         * }
         */
        int off = offset;        
        
        /* 
         * Read the 64-bit time-stamp. It is stored as two 32-bit values which
         * must be combined.
         */
        
        /* Decode the upper 32-bits. */
        long hi = decodeBytes(targetEventRec, off, 4, false); 
        off += 4;        
        
        /* Decode the lower 32-bits. */
        long lo = decodeBytes(targetEventRec, off, 4, false);
        off += 4;
                
        /*
         * Combine the upper and lower 32-bits to retrieve the 64-bit value.
         * 
         * The 'timestamp' field is of type 'long', which is a signed 64-bit
         * type, so it can only display a positive timestamp up to 2^63 - 1
         * (If an unsigned long existed, it could display positive values up
         * to 2^64 - 1).
         * 
         * If the MSB of the timestamp is set (if bit 32 of 'hi' is set), then
         * the timestamp value is too large, so just set the timestamp to -1.
         * This likely indicates corrupt data (at 4GHz it would take 
         * over 73 years to reach 2^63), so -1 also serves as an indication 
         * that the data is corrupt. 
         */
        if (hi >= Math.pow(2, 31)) {
            res.timestamp = -1L;
        }
        else {
            /* Java cannot perform a 32-bit shift, so we must multiply. */
            res.timestamp = (long) (hi * Math.pow(2, 32) + lo);
        }
            
        /* Read the 32-bit sequence number. */
        res.sequenceNum = decodeBytes(targetEventRec, off, 4, false);
        off += 4;
        
        /* Read the 32-bit event code. */
        long code = decodeBytes(targetEventRec, off, 4, false);
        off += 4;
        
        /* 
         * The event code contains the eventId in the upper 16-bits and the
         * moduleId in the lower 16-bits.
         */
        res.eventId = (int) code >> 16;                
        res.moduleId = (int) code & 0x0000FFFF;
        
        /* Read all IArg arguments. */
        
        /* The IArg size can vary between targets. */
        int argSize = meta.getTargetArgSize();
        
        for (int i = 0; i < 8; i++) {
            res.args[i] = (int) decodeBytes(targetEventRec, off, argSize, 
                                            true);
            off += argSize;
        }
        
        /* If this is a Log_print */
        if (res.eventId == 0) {
            /* 
             * The first argument in a Log_print record is the address of
             * the format string. 
             * res.args[0] is a signed 32-bit value, but we need the address
             * as an unsigned 32-bit value, so decode it again.  
             */
            res.formatAddr = decodeBytes(targetEventRec, offset + 16, argSize, 
                                         false);
        }
                
        return (res);
    }
    
    /*
     *  ======== decodeBytes ========
     *  This is a convenience method which exposes the TargetDecoder's
     *  'decodeBytes' API.
     */
    public long decodeBytes(byte buffer[], int offset, int size, 
                            boolean signed)
    {
        return (this.targDecoder.decodeBytes(buffer, offset, size, signed));
    }
    
    /*
     *  ======== encodeArg ========
     *  This is a convenience method which exposes the TargetEncoder's
     *  'encodeBytes' API.
     */
    public void encodeArg(byte buf[], int offset, long arg, int size) 
    {
        this.targEncoder.encodeBytes(buf, offset, arg, size);
    }
    
    /*
     *  ======== encode ========
     *  Encodes a HostEvent back into target bytes.
     */
    public void encode(HostEvent evt, byte[] buf, int offset)
    {
        int off = offset;
        int sz = 4;
        
        /* Encode 64-bit time-stamp */
        long hi = evt.timestamp / ((long) Math.pow(2, 32));
        this.targEncoder.encodeBytes(buf, off, hi, sz);
        off += sz;
        
        long lo = evt.timestamp & 0x00000000FFFFFFFFl;
        this.targEncoder.encodeBytes(buf, off, lo, sz);
        off += sz;
                
        /* Encode 32-bit sequence number */
        this.targEncoder.encodeBytes(buf, off, evt.sequenceNum, sz);
        off += sz;
        
        /* Encode 32-bit event */
        long code = (evt.eventId << 16) + evt.moduleId; 
        this.targEncoder.encodeBytes(buf, off, code, sz);
        off += sz;
        
        /* Encode all IArg arguments */
        
        /* Size of the arguments in bytes */
        sz = meta.getTargetArgSize();
        
        for (int i = 0; i < evt.args.length; i++) {
            this.targEncoder.encodeBytes(buf, off, evt.args[i], sz);
            off += sz;
        }        
    }    
}