ddfrecord.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.

         * them.
         */
        /* -------------------------------------------------------------------- */
        int i;
        int nFieldEntryWidth;

        nFieldEntryWidth = _sizeFieldLength + _sizeFieldPos + _sizeFieldTag;
        nFieldCount = 0;
        for (i = 0; i < nDataSize; i += nFieldEntryWidth) {
            if (pachData[i] == DDF_FIELD_TERMINATOR)
                break;

            nFieldCount++;
        }

        /* ==================================================================== */
        /* Allocate, and read field definitions. */
        /* ==================================================================== */
        paoFields = new Vector(nFieldCount);

        for (i = 0; i < nFieldCount; i++) {
            String szTag;
            int nEntryOffset = i * nFieldEntryWidth;
            int nFieldLength, nFieldPos;

            /* -------------------------------------------------------------------- */
            /* Read the position information and tag. */
            /* -------------------------------------------------------------------- */
            szTag = new String(pachData, nEntryOffset, _sizeFieldTag);

            nEntryOffset += _sizeFieldTag;
            nFieldLength = Integer.valueOf(new String(pachData, nEntryOffset, _sizeFieldLength))
                    .intValue();

            nEntryOffset += _sizeFieldLength;
            nFieldPos = Integer.valueOf(new String(pachData, nEntryOffset, _sizeFieldPos))
                    .intValue();

            /* -------------------------------------------------------------------- */
            /* Find the corresponding field in the module directory. */
            /* -------------------------------------------------------------------- */
            DDFFieldDefinition poFieldDefn = poModule.findFieldDefn(szTag);

            if (poFieldDefn == null) {
                Debug.error("DDFRecord: Undefined field " + szTag
                        + " encountered in data record.");
                return false;
            }

            DDFField ddff = null;

            if (readSubfields) {

                /* -------------------------------------------------------------------- */
                /* Assign info the DDFField. */
                /* -------------------------------------------------------------------- */
                byte[] tempData = new byte[nFieldLength];
                System.arraycopy(pachData, _fieldAreaStart + nFieldPos
                        - DDF_LEADER_SIZE, tempData, 0, tempData.length);

                ddff = new DDFField(poFieldDefn, tempData, readSubfields);

            } else {

                // Save the info for reading later directly out of the
                // field.
                ddff = new DDFField(poFieldDefn, nFieldPos, nFieldLength);
                ddff.setHeaderOffset(poModule._recLength + _fieldAreaStart);
            }
            paoFields.add(ddff);
        }

        return true;
    }

    /**
     * Find the named field within this record.
     * 
     * @param pszName The name of the field to fetch. The comparison
     *        is case insensitive.
     * @param iFieldIndex The instance of this field to fetch. Use
     *        zero (the default) for the first instance.
     * 
     * @return Pointer to the requested DDFField. This pointer is to
     *         an internal object, and should not be freed. It remains
     *         valid until the next record read.
     */
    public DDFField findField(String pszName, int iFieldIndex) {
        for (Iterator it = paoFields.iterator(); it.hasNext();) {
            DDFField ddff = (DDFField) it.next();
            if (pszName.equalsIgnoreCase(ddff.getFieldDefn().getName())) {
                if (iFieldIndex == 0) {
                    return ddff;
                } else {
                    iFieldIndex--;
                }
            }
        }
        return null;
    }

    /**
     * Fetch field object based on index.
     * 
     * @param i The index of the field to fetch. Between 0 and
     *        GetFieldCount()-1.
     * 
     * @return A DDFField pointer, or null if the index is out of
     *         range.
     */
    public DDFField getField(int i) {
        try {
            return (DDFField) paoFields.elementAt(i);
        } catch (ArrayIndexOutOfBoundsException aioobe) {
            return null;
        }
    }

    /**
     * Get an interator over the fields.
     */
    public Iterator iterator() {
        if (paoFields != null) {
            return paoFields.iterator();
        }
        return null;
    }

    /**
     * Fetch value of a subfield as an integer. This is a convenience
     * function for fetching a subfield of a field within this record.
     * 
     * @param pszField The name of the field containing the subfield.
     * @param iFieldIndex The instance of this field within the
     *        record. Use zero for the first instance of this field.
     * @param pszSubfield The name of the subfield within the selected
     *        field.
     * @param iSubfieldIndex The instance of this subfield within the
     *        record. Use zero for the first instance.
     * @return The value of the subfield, or zero if it failed for
     *         some reason.
     */
    public int getIntSubfield(String pszField, int iFieldIndex,
                              String pszSubfield, int iSubfieldIndex) {
        DDFField poField;

        /* -------------------------------------------------------------------- */
        /* Fetch the field. If this fails, return zero. */
        /* -------------------------------------------------------------------- */
        poField = findField(pszField, iFieldIndex);
        if (poField == null) {
            return 0;
        }

        /* -------------------------------------------------------------------- */
        /* Get the subfield definition */
        /* -------------------------------------------------------------------- */

        DDFSubfieldDefinition poSFDefn = poField.getFieldDefn()
                .findSubfieldDefn(pszSubfield);

        if (poSFDefn == null) {
            return 0;
        }

        /* -------------------------------------------------------------------- */
        /* Get a pointer to the data. */
        /* -------------------------------------------------------------------- */
        MutableInt nBytesRemaining = new MutableInt();

        byte[] pachData = poField.getSubfieldData(poSFDefn,
                nBytesRemaining,
                iSubfieldIndex);

        /* -------------------------------------------------------------------- */
        /* Return the extracted value. */
        /* -------------------------------------------------------------------- */

        return poSFDefn.extractIntData(pachData, nBytesRemaining.value, null);
    }

    /**
     * Fetch value of a subfield as a float (double). This is a
     * convenience function for fetching a subfield of a field within
     * this record.
     * 
     * @param pszField The name of the field containing the subfield.
     * @param iFieldIndex The instance of this field within the
     *        record. Use zero for the first instance of this field.
     * @param pszSubfield The name of the subfield within the selected
     *        field.
     * @param iSubfieldIndex The instance of this subfield within the
     *        record. Use zero for the first instance.
     * @return The value of the subfield, or zero if it failed for
     *         some reason.
     */
    public double getFloatSubfield(String pszField, int iFieldIndex,
                                   String pszSubfield, int iSubfieldIndex) {
        DDFField poField;

        /* -------------------------------------------------------------------- */
        /* Fetch the field. If this fails, return zero. */
        /* -------------------------------------------------------------------- */
        poField = findField(pszField, iFieldIndex);
        if (poField == null) {
            return 0;
        }

        /* -------------------------------------------------------------------- */
        /* Get the subfield definition */
        /* -------------------------------------------------------------------- */
        DDFSubfieldDefinition poSFDefn = poField.getFieldDefn()
                .findSubfieldDefn(pszSubfield);

        if (poSFDefn == null) {
            return 0;
        }

        /* -------------------------------------------------------------------- */
        /* Get a pointer to the data. */
        /* -------------------------------------------------------------------- */
        MutableInt nBytesRemaining = new MutableInt();

        byte[] pachData = poField.getSubfieldData(poSFDefn,
                nBytesRemaining,
                iSubfieldIndex);

        /* -------------------------------------------------------------------- */
        /* Return the extracted value. */
        /* -------------------------------------------------------------------- */
        return poSFDefn.extractFloatData(pachData, nBytesRemaining.value, null);
    }

    /**
     * Fetch value of a subfield as a string. This is a convenience
     * function for fetching a subfield of a field within this record.
     * 
     * @param pszField The name of the field containing the subfield.
     * @param iFieldIndex The instance of this field within the
     *        record. Use zero for the first instance of this field.
     * @param pszSubfield The name of the subfield within the selected
     *        field.
     * @param iSubfieldIndex The instance of this subfield within the
     *        record. Use zero for the first instance.
     * @return The value of the subfield, or null if it failed for
     *         some reason. The returned pointer is to internal data
     *         and should not be modified or freed by the application.
     */

    String getStringSubfield(String pszField, int iFieldIndex,
                             String pszSubfield, int iSubfieldIndex) {

        DDFField poField;

        /* -------------------------------------------------------------------- */
        /* Fetch the field. If this fails, return zero. */
        /* -------------------------------------------------------------------- */
        poField = findField(pszField, iFieldIndex);
        if (poField == null) {
            return null;
        }

        /* -------------------------------------------------------------------- */
        /* Get the subfield definition */
        /* -------------------------------------------------------------------- */
        DDFSubfieldDefinition poSFDefn = poField.getFieldDefn()
                .findSubfieldDefn(pszSubfield);

        if (poSFDefn == null) {
            return null;
        }

        /* -------------------------------------------------------------------- */
        /* Get a pointer to the data. */
        /* -------------------------------------------------------------------- */
        MutableInt nBytesRemaining = new MutableInt();

        byte[] pachData = poField.getSubfieldData(poSFDefn,
                nBytesRemaining,
                iSubfieldIndex);

        /* -------------------------------------------------------------------- */
        /* Return the extracted value. */
        /* -------------------------------------------------------------------- */

        return poSFDefn.extractStringData(pachData, nBytesRemaining.value, null);
    }

}