path: root/lib/jinterface/java_src/com/ericsson/otp/erlang/OtpErlangMap.java

/*
 * %CopyrightBegin%
 *
 * Copyright Ericsson AB 2000-2013. All Rights Reserved.
 *
 * The contents of this file are subject to the Erlang Public License,
 * Version 1.1, (the "License"); you may not use this file except in
 * compliance with the License. You should have received a copy of the
 * Erlang Public License along with this software. If not, it can be
 * retrieved online at http://www.erlang.org/.
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 *
 * %CopyrightEnd%
 */
package com.ericsson.otp.erlang;

/**
 * Provides a Java representation of Erlang maps. Maps are created from one or
 * more arbitrary Erlang terms.
 *
 * <p>
 * The arity of the map is the number of elements it contains. The keys and
 * values can be retrieved as arrays and the value for a key can be queried.
 *
 */
public class OtpErlangMap extends OtpErlangObject {
    // don't change this!
    private static final long serialVersionUID = -6410770117696198497L;

    private static final OtpErlangObject[] NO_ELEMENTS = new OtpErlangObject[0];

    private OtpErlangObject[] keys = NO_ELEMENTS;
    private OtpErlangObject[] values = NO_ELEMENTS;

    /**
     * Create a map from an array of keys and an array of values.
     *
     * @param keys
     *            the array of terms to create the map keys from.
     * @param values
     *            the array of terms to create the map values from.
     *
     * @exception java.lang.IllegalArgumentException
     *                if any array is empty (null) or contains null elements.
     */
    public OtpErlangMap(final OtpErlangObject[] keys,
            final OtpErlangObject[] values) {
        this(keys, 0, keys.length, values, 0, values.length);
    }

    /**
     * Create a map from an array of terms.
     *
     * @param keys
     *            the array of terms to create the map from.
     * @param kstart
     *            the offset of the first key to insert.
     * @param kcount
     *            the number of keys to insert.
     * @param values
     *            the array of values to create the map from.
     * @param vstart
     *            the offset of the first value to insert.
     * @param vcount
     *            the number of values to insert.
     *
     * @exception java.lang.IllegalArgumentException
     *                if any array is empty (null) or contains null elements.
     * @exception java.lang.IllegalArgumentException
     *                if kcount and vcount differ.
     */
    public OtpErlangMap(final OtpErlangObject[] keys, final int kstart,
            final int kcount, final OtpErlangObject[] values, final int vstart,
            final int vcount) {
        if (keys == null || values == null) {
            throw new java.lang.IllegalArgumentException(
                    "Map content can't be null");
        } else if (kcount != vcount) {
            throw new java.lang.IllegalArgumentException(
                    "Map keys and values must have same arity");
        } else if (vcount < 1) {
            this.keys = NO_ELEMENTS;
            this.values = NO_ELEMENTS;
        } else {
            this.keys = new OtpErlangObject[vcount];
            for (int i = 0; i < vcount; i++) {
                if (keys[kstart + i] != null) {
                    this.keys[i] = keys[kstart + i];
                } else {
                    throw new java.lang.IllegalArgumentException(
                            "Map key cannot be null (element" + (kstart + i)
                                    + ")");
                }
            }
            this.values = new OtpErlangObject[vcount];
            for (int i = 0; i < vcount; i++) {
                if (values[vstart + i] != null) {
                    this.values[i] = values[vstart + i];
                } else {
                    throw new java.lang.IllegalArgumentException(
                            "Map value cannot be null (element" + (vstart + i)
                                    + ")");
                }
            }
        }
    }

    /**
     * Create a map from a stream containing a map encoded in Erlang external
     * format.
     *
     * @param buf
     *            the stream containing the encoded map.
     *
     * @exception OtpErlangDecodeException
     *                if the buffer does not contain a valid external
     *                representation of an Erlang map.
     */
    public OtpErlangMap(final OtpInputStream buf)
            throws OtpErlangDecodeException {
        final int arity = buf.read_map_head();

        if (arity > 0) {
            keys = new OtpErlangObject[arity];
            values = new OtpErlangObject[arity];

            for (int i = 0; i < arity; i++) {
                keys[i] = buf.read_any();
                values[i] = buf.read_any();
            }
        } else {
            keys = NO_ELEMENTS;
            values = NO_ELEMENTS;
        }
    }

    /**
     * Get the arity of the map.
     *
     * @return the number of elements contained in the map.
     */
    public int arity() {
        return keys.length;
    }

    /**
     * Get the specified value from the map.
     *
     * @param key
     *            the key of the requested value.
     *
     * @return the requested value, of null if key is not a valid key.
     */
    public OtpErlangObject get(final OtpErlangObject key) {
        if (key == null) {
            return null;
        }
        for (int i = 0; i < keys.length; i++) {
            if (key.equals(keys[i])) {
                return values[i];
            }
        }
        return null;
    }

    /**
     * Get all the keys from the map as an array.
     *
     * @return an array containing all of the map's keys.
     */
    public OtpErlangObject[] keys() {
        final OtpErlangObject[] res = new OtpErlangObject[arity()];
        System.arraycopy(keys, 0, res, 0, res.length);
        return res;
    }

    /**
     * Get all the values from the map as an array.
     *
     * @return an array containing all of the map's values.
     */
    public OtpErlangObject[] values() {
        final OtpErlangObject[] res = new OtpErlangObject[arity()];
        System.arraycopy(values, 0, res, 0, res.length);
        return res;
    }

    /**
     * Get the string representation of the map.
     *
     * @return the string representation of the map.
     */
    @Override
    public String toString() {
        int i;
        final StringBuffer s = new StringBuffer();
        final int arity = values.length;

        s.append("#{");

        for (i = 0; i < arity; i++) {
            if (i > 0) {
                s.append(",");
            }
            s.append(keys[i].toString());
            s.append(" => ");
            s.append(values[i].toString());
        }

        s.append("}");

        return s.toString();
    }

    /**
     * Convert this map to the equivalent Erlang external representation.
     *
     * @param buf
     *            an output stream to which the encoded map should be written.
     */
    @Override
    public void encode(final OtpOutputStream buf) {
        final int arity = values.length;

        buf.write_map_head(arity);

        for (int i = 0; i < arity; i++) {
            buf.write_any(keys[i]);
            buf.write_any(values[i]);
        }
    }

    /**
     * Determine if two maps are equal. Maps are equal if they have the same
     * arity and all of the elements are equal.
     *
     * @param o
     *            the map to compare to.
     *
     * @return true if the maps have the same arity and all the elements are
     *         equal.
     */
    @Override
    public boolean equals(final Object o) {
        if (!(o instanceof OtpErlangMap)) {
            return false;
        }

        final OtpErlangMap t = (OtpErlangMap) o;
        final int a = arity();

        if (a != t.arity()) {
            return false;
        }

        for (int i = 0; i < a; i++) {
            if (!keys[i].equals(t.keys[i])) {
                return false; // early exit
            }
        }
        for (int i = 0; i < a; i++) {
            if (!values[i].equals(t.values[i])) {
                return false; // early exit
            }
        }

        return true;
    }

    @Override
    protected int doHashCode() {
        final OtpErlangObject.Hash hash = new OtpErlangObject.Hash(9);
        final int a = arity();
        hash.combine(a);
        for (int i = 0; i < a; i++) {
            hash.combine(keys[i].hashCode());
        }
        for (int i = 0; i < a; i++) {
            hash.combine(values[i].hashCode());
        }
        return hash.valueOf();
    }

    @Override
    public Object clone() {
        final OtpErlangMap newMap = (OtpErlangMap) super.clone();
        newMap.values = values.clone();
        return newMap;
    }
}