/*
    * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    *
    * This code is free software; you can redistribute it and/or modify it
    * under the terms of the GNU General Public License version 2 only, as
    * published by the Free Software Foundation.  Oracle designates this
    * particular file as subject to the "Classpath" exception as provided
    * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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   */
  
  package davmail.ldap;
  
  import java.io.UnsupportedEncodingException;
  import java.nio.charset.StandardCharsets;
  
  /**
   * A BER encoder.
   *
   * @author Jagane Sundar
   * @author Scott Seligman
   * @author Vincent Ryan
   */
  public final class BerEncoder extends Ber {
  
      private int curSeqIndex;
      private int[] seqOffset;
      private static final int INITIAL_SEQUENCES = 16;
      private static final int DEFAULT_BUFSIZE = 1024;
  
      // When buf is full, expand its size by the following factor.
      private static final int BUF_GROWTH_FACTOR = 8;
  
      /**
       * Creates a BER buffer for encoding.
       */
      public BerEncoder() {
          this(DEFAULT_BUFSIZE);
      }
  
      /**
       * Creates a BER buffer of a specified size for encoding.
       * Specify the initial bufsize.  Buffer will be expanded as needed.
       * @param bufsize The number of bytes for the buffer.
       */
      public BerEncoder(int bufsize) {
          buf = new byte[bufsize];
          this.bufsize = bufsize;
          offset = 0;
  
          seqOffset = new int[INITIAL_SEQUENCES];
          curSeqIndex = 0;
      }
  
      /**
       * Resets encoder to state when newly constructed.  Zeros out
       * internal data structures.
       */
      public void reset() {
          while (offset > 0) {
              buf[--offset] = 0;
          }
          while (curSeqIndex > 0) {
              seqOffset[--curSeqIndex] = 0;
          }
      }
  
  // ------------------ Accessor methods ------------
  
      /**
       * Gets the number of encoded bytes in this BER buffer.
       */
      public int getDataLen() {
          return offset;
      }
  
      /**
       * Gets the buffer that contains the BER encoding. Throws an
       * exception if unmatched beginSeq() and endSeq() pairs were
       * encountered. Not entire buffer contains encoded bytes.
       * Use getDataLen() to determine number of encoded bytes.
       * Use getBuffer(true) to get rid of excess bytes in array.
       * @throws IllegalStateException If buffer contains unbalanced sequence.
       */
      public byte[] getBuf() {
         if (curSeqIndex != 0) {
             throw new IllegalStateException("BER encode error: Unbalanced SEQUENCEs.");
         }
         return buf;     // shared buffer, be careful to use this method.
     }
 
     /**
      * Gets the buffer that contains the BER encoding, trimming unused bytes.
      *
      * @throws IllegalStateException If buffer contains unbalanced sequence.
      */
     @SuppressWarnings("unused")
     public byte[] getTrimmedBuf() {
         int len = getDataLen();
         byte[] trimBuf = new byte[len];
 
         System.arraycopy(getBuf(), 0, trimBuf, 0, len);
         return trimBuf;
     }
 
 // -------------- encoding methods -------------
 
     /**
      * Begin encoding a sequence with a tag.
      */
     public void beginSeq(int tag) {
 
         // Double the size of the SEQUENCE array if it overflows
         if (curSeqIndex >= seqOffset.length) {
             int[] seqOffsetTmp = new int[seqOffset.length * 2];
 
             System.arraycopy(seqOffset, 0, seqOffsetTmp, 0, seqOffset.length);
             seqOffset = seqOffsetTmp;
         }
 
         encodeByte(tag);
         seqOffset[curSeqIndex] = offset;
 
         // Save space for sequence length.
         // %%% Currently we save enough space for sequences up to 64k.
         //     For larger sequences we'll need to shift the data to the right
         //     in endSeq().  If we could instead pad the length field with
         //     zeros, it would be a big win.
         ensureFreeBytes(3);
         offset += 3;
 
         curSeqIndex++;
     }
 
     /**
      * Terminate a BER sequence.
      */
     public void endSeq() throws EncodeException {
         curSeqIndex--;
         if (curSeqIndex < 0) {
             throw new IllegalStateException("BER encode error: Unbalanced SEQUENCEs.");
         }
 
         int start = seqOffset[curSeqIndex] + 3; // index beyond length field
         int len = offset - start;
 
         if (len <= 0x7f) {
             shiftSeqData(start, len, -2);
             buf[seqOffset[curSeqIndex]] = (byte) len;
         } else if (len <= 0xff) {
             shiftSeqData(start, len, -1);
             buf[seqOffset[curSeqIndex]] = (byte) 0x81;
             buf[seqOffset[curSeqIndex] + 1] = (byte) len;
         } else if (len <= 0xffff) {
             buf[seqOffset[curSeqIndex]] = (byte) 0x82;
             buf[seqOffset[curSeqIndex] + 1] = (byte) (len >> 8);
             buf[seqOffset[curSeqIndex] + 2] = (byte) len;
         } else if (len <= 0xffffff) {
             shiftSeqData(start, len, 1);
             buf[seqOffset[curSeqIndex]] = (byte) 0x83;
             buf[seqOffset[curSeqIndex] + 1] = (byte) (len >> 16);
             buf[seqOffset[curSeqIndex] + 2] = (byte) (len >> 8);
             buf[seqOffset[curSeqIndex] + 3] = (byte) len;
         } else {
             throw new EncodeException("SEQUENCE too long");
         }
     }
 
     /**
      * Shifts contents of buf in the range [start,start+len) a specified amount.
      * Positive shift value means shift to the right.
      */
     private void shiftSeqData(int start, int len, int shift) {
         if (shift > 0) {
             ensureFreeBytes(shift);
         }
         System.arraycopy(buf, start, buf, start + shift, len);
         offset += shift;
     }
 
     /**
      * Encode a single byte.
      */
     public void encodeByte(int b) {
         ensureFreeBytes(1);
         buf[offset++] = (byte) b;
     }
 
 /*
     private void deleteByte() {
         offset--;
     }
 */
 
 
     /*
      * Encodes an int.
      *<blockquote><pre>
      * BER integer ::= 0x02 berlength byte {byte}*
      *</pre></blockquote>
      */
     public void encodeInt(int i) {
         encodeInt(i, 0x02);
     }
 
     /**
      * Encodes an int and a tag.
      *<blockquote><pre>
      * BER integer w tag ::= tag berlength byte {byte}*
      *</pre></blockquote>
      */
     public void encodeInt(int i, int tag) {
         int mask = 0xff800000;
         int intsize = 4;
 
         while( (((i & mask) == 0) || ((i & mask) == mask)) && (intsize > 1) ) {
             intsize--;
             i <<= 8;
         }
 
         encodeInt(i, tag, intsize);
     }
 
     //
     // encodes an int using numbytes for the actual encoding.
     //
     private void encodeInt(int i, int tag, int intsize) {
 
         //
         // integer ::= 0x02 asnlength byte {byte}*
         //
 
         if (intsize > 4) {
             throw new IllegalArgumentException("BER encode error: INTEGER too long.");
         }
 
         ensureFreeBytes(2 + intsize);
 
         buf[offset++] = (byte) tag;
         buf[offset++] = (byte) intsize;
 
         int mask = 0xff000000;
 
         while (intsize-- > 0) {
             buf[offset++] = (byte) ((i & mask) >> 24);
             i <<= 8;
         }
     }
 
     /**
      * Encodes a boolean.
      *<blockquote><pre>
      * BER boolean ::= 0x01 0x01 {0xff|0x00}
      *</pre></blockquote>
      */
     @SuppressWarnings("unused")
     public void encodeBoolean(boolean b) {
         encodeBoolean(b, ASN_BOOLEAN);
     }
 
 
     /**
      * Encodes a boolean and a tag
      *<blockquote><pre>
      * BER boolean w TAG ::= tag 0x01 {0xff|0x00}
      *</pre></blockquote>
      */
     public void encodeBoolean(boolean b, int tag) {
         ensureFreeBytes(3);
 
         buf[offset++] = (byte) tag;
         buf[offset++] = 0x01;
         buf[offset++] = b ? (byte) 0xff : (byte) 0x00;
     }
 
     /**
      * Encodes a string.
      *<blockquote><pre>
      * BER string ::= 0x04 strlen byte1 byte2...
      *</pre></blockquote>
      * The string is converted into bytes using UTF-8 or ISO-Latin-1.
      */
     public void encodeString(String str, boolean encodeUTF8)
             throws EncodeException {
         encodeString(str, ASN_OCTET_STR, encodeUTF8);
     }
 
     /**
      * Encodes a string and a tag.
      *<blockquote><pre>
      * BER string w TAG ::= tag strlen byte1 byte2...
      *</pre></blockquote>
      */
     public void encodeString(String str, int tag, boolean encodeUTF8)
             throws EncodeException {
 
         encodeByte(tag);
 
         int i = 0;
         int count;
         byte[] bytes = null;
 
         if (str == null) {
             count = 0;
         } else if (encodeUTF8) {
             bytes = str.getBytes(StandardCharsets.UTF_8);
             count = bytes.length;
         } else {
             try {
                 bytes = str.getBytes("8859_1");
                 count = bytes.length;
             } catch (UnsupportedEncodingException e) {
                 throw new EncodeException("8859_1 not available on platform");
             }
         }
 
         encodeLength(count);
 
         ensureFreeBytes(count);
         while (i < count) {
             buf[offset++] = bytes[i++];
         }
     }
 
     /**
      * Encodes a portion of an octet string and a tag.
      */
     public void encodeOctetString(byte[] tb, int tag, int tboffset, int length)
             throws EncodeException {
 
         encodeByte(tag);
         encodeLength(length);
 
         if (length > 0) {
             ensureFreeBytes(length);
             System.arraycopy(tb, tboffset, buf, offset, length);
             offset += length;
         }
     }
 
     /**
      * Encodes an octet string and a tag.
      */
     public void encodeOctetString(byte[] tb, int tag) throws EncodeException {
         encodeOctetString(tb, tag, 0, tb.length);
     }
 
     private void encodeLength(int len) throws EncodeException {
         ensureFreeBytes(4);     // worst case
 
         if (len < 128) {
             buf[offset++] = (byte) len;
         } else if (len <= 0xff) {
             buf[offset++] = (byte) 0x81;
             buf[offset++] = (byte) len;
         } else if (len <= 0xffff) {
             buf[offset++] = (byte) 0x82;
             buf[offset++] = (byte) (len >> 8);
             buf[offset++] = (byte) (len & 0xff);
         } else if (len <= 0xffffff) {
             buf[offset++] = (byte) 0x83;
             buf[offset++] = (byte) (len >> 16);
             buf[offset++] = (byte) (len >> 8);
             buf[offset++] = (byte) (len & 0xff);
         } else {
             throw new EncodeException("string too long");
         }
     }
 
     /**
      * Encodes an array of strings.
      */
     @SuppressWarnings("unused")
     public void encodeStringArray(String[] strs, boolean encodeUTF8)
             throws EncodeException {
         if (strs == null)
             return;
         for (String str : strs) {
             encodeString(str, encodeUTF8);
         }
     }
 /*
     private void encodeNull() {
 
         //
         // NULL ::= 0x05 0x00
         //
         encodeByte(0x05);
         encodeByte(0x00);
     }
 */
 
     /**
      * Ensures that there are at least "len" unused bytes in "buf".
      * When more space is needed "buf" is expanded by a factor of
      * BUF_GROWTH_FACTOR, then "len" bytes are added if "buf" still
      * isn't large enough.
      */
     private void ensureFreeBytes(int len) {
         if (bufsize - offset < len) {
             int newsize = bufsize * BUF_GROWTH_FACTOR;
             if (newsize - offset < len) {
                 newsize += len;
             }
             byte[] newbuf = new byte[newsize];
             // Only copy bytes in the range [0, offset)
             System.arraycopy(buf, 0, newbuf, 0, offset);
 
             buf = newbuf;
             bufsize = newsize;
         }
     }
 }