ddfmodule.java

openmap java写的开源数字地图程序. 用applet实现,可以像google map 那样放大缩小地图.

                    subPachRecord,
                    0,
                    nFieldLength);

            paoFieldDefns.add(new DDFFieldDefinition(this, new String(szTag, 0, _sizeFieldTag), subPachRecord));
        }

        // Free the memory...
        achLeader = null;
        pachRecord = null;

        // Record the current file offset, the beginning of the first
        // data record.
        nFirstRecordOffset = fpDDF.getFilePointer();

        return fpDDF;
    }

    /**
     * Write out module info to debugging file.
     * 
     * A variety of information about the module is written to the
     * debugging file. This includes all the field and subfield
     * definitions read from the header.
     */
    public String toString() {
        StringBuffer buf = new StringBuffer("DDFModule:\n");
        buf.append("    _recLength = " + _recLength + "\n");
        buf.append("    _interchangeLevel = " + _interchangeLevel + "\n");
        buf.append("    _leaderIden = " + (char) _leaderIden + "\n");
        buf.append("    _inlineCodeExtensionIndicator = "
                + _inlineCodeExtensionIndicator + "\n");
        buf.append("    _versionNumber = " + _versionNumber + "\n");
        buf.append("    _appIndicator = " + _appIndicator + "\n");
        buf.append("    _extendedCharSet = " + _extendedCharSet + "\n");
        buf.append("    _fieldControlLength = " + _fieldControlLength + "\n");
        buf.append("    _fieldAreaStart = " + _fieldAreaStart + "\n");
        buf.append("    _sizeFieldLength = " + _sizeFieldLength + "\n");
        buf.append("    _sizeFieldPos = " + _sizeFieldPos + "\n");
        buf.append("    _sizeFieldTag = " + _sizeFieldTag + "\n");
        return buf.toString();
    }

    public String dump() {
        StringBuffer buf = new StringBuffer(toString());

        DDFRecord poRecord;
        int iRecord = 0;
        while ((poRecord = readRecord()) != null) {
            buf.append("  Record " + (iRecord++) + "(" + poRecord.getDataSize()
                    + " bytes)\n");

            for (Iterator it = poRecord.iterator(); it.hasNext(); buf.append(((DDFField) it.next()).toString())) {
            }
        }
        return buf.toString();
    }

    /**
     * Fetch the definition of the named field.
     * 
     * This function will scan the DDFFieldDefn's on this module, to
     * find one with the indicated field name.
     * 
     * @param pszFieldName The name of the field to search for. The
     *        comparison is case insensitive.
     * 
     * @return A pointer to the request DDFFieldDefn object is
     *         returned, or null if none matching the name are found.
     *         The return object remains owned by the DDFModule, and
     *         should not be deleted by application code.
     */
    public DDFFieldDefinition findFieldDefn(String pszFieldName) {

        for (Iterator it = paoFieldDefns.iterator(); it.hasNext();) {
            DDFFieldDefinition ddffd = (DDFFieldDefinition) it.next();
            String pszThisName = ddffd.getName();

            if (Debug.debugging("iso8211detail")) {
                Debug.output("DDFModule.findFieldDefn(" + pszFieldName + ":"
                        + pszFieldName.length() + ") checking against ["
                        + pszThisName + ":" + pszThisName.length() + "]");
            }

            if (pszFieldName.equalsIgnoreCase(pszThisName)) {
                return ddffd;
            }
        }

        return null;
    }

    /**
     * Read one record from the file, and return to the application.
     * The returned record is owned by the module, and is reused from
     * call to call in order to preserve headers when they aren't
     * being re-read from record to record.
     * 
     * @return A pointer to a DDFRecord object is returned, or null if
     *         a read error, or end of file occurs. The returned
     *         record is owned by the module, and should not be
     *         deleted by the application. The record is only valid
     *         untill the next ReadRecord() at which point it is
     *         overwritten.
     */
    public DDFRecord readRecord() {
        if (poRecord == null) {
            poRecord = new DDFRecord(this);
        }

        if (poRecord.read()) {
            return poRecord;
        } else {
            return null;
        }
    }

    /**
     * Method for other components to call to get the DDFModule to
     * read bytes into the provided array.
     * 
     * @param toData the bytes to put data into.
     * @param offset the byte offset to start reading from, whereever
     *        the pointer currently is.
     * @param length the number of bytes to read.
     * @return the number of bytes read.
     */
    public int read(byte[] toData, int offset, int length) {
        if (fpDDF == null) {
            reopen();
        }

        if (fpDDF != null) {
            try {
                return fpDDF.read(toData, offset, length);
            } catch (IOException ioe) {
                Debug.error("DDFModule.read(): IOException caught");
            } catch (ArrayIndexOutOfBoundsException aioobe) {
                Debug.error("DDFModule.read(): "
                        + aioobe.getMessage()
                        + " reading from "
                        + offset
                        + " to "
                        + length
                        + " into "
                        + (toData == null ? "null byte[]" : "byte["
                                + toData.length + "]"));
                aioobe.printStackTrace();
            }
        }
        return 0;
    }

    /**
     * Convenience method to read a byte from the data file. Assumes
     * that you know what you are doing based on the parameters read
     * in the data file. For DDFFields that haven't loaded their
     * subfields.
     */
    public int read() {
        if (fpDDF == null) {
            reopen();
        }

        if (fpDDF != null) {
            try {
                return fpDDF.read();
            } catch (IOException ioe) {
                Debug.error("DDFModule.read(): IOException caught");
            }
        }
        return 0;
    }

    /**
     * Convenience method to seek to a location in the data file.
     * Assumes that you know what you are doing based on the
     * parameters read in the data file. For DDFFields that haven't
     * loaded their subfields.
     * 
     * @param pos the byte position to reposition the file pointer to.
     */
    public void seek(long pos) throws IOException {
        if (fpDDF == null) {
            reopen();
        }

        if (fpDDF != null) {
            fpDDF.seek(pos);
        } else {
            throw new IOException("DDFModule doesn't have a pointer to a file");
        }
    }

    /**
     * Fetch a field definition by index.
     * 
     * @param i (from 0 to GetFieldCount() - 1.
     * @return the returned field pointer or null if the index is out
     *         of range.
     */
    public DDFFieldDefinition getField(int i) {
        if (i >= 0 || i < paoFieldDefns.size()) {
            return (DDFFieldDefinition) paoFieldDefns.elementAt(i);
        }

        return null;
    }

    /**
     * Return to first record.
     * 
     * The next call to ReadRecord() will read the first data record
     * in the file.
     * 
     * @param nOffset the offset in the file to return to. By default
     *        this is -1, a special value indicating that reading
     *        should return to the first data record. Otherwise it is
     *        an absolute byte offset in the file.
     */
    public void rewind(long nOffset) throws IOException {
        if (nOffset == -1) {
            nOffset = nFirstRecordOffset;
        }

        if (fpDDF != null) {
            fpDDF.seek(nOffset);

            // Don't know what this has to do with anything...
            if (nOffset == nFirstRecordOffset && poRecord != null) {
                poRecord.clear();
            }
        }

    }

    public void reopen() {
        try {
            if (fpDDF == null) {
                fpDDF = new BinaryBufferedFile(fileName);
            }
        } catch (IOException ioe) {

        }
    }
}