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- using System;
- using ICSharpCode.SharpZipLib.Checksum;
- namespace ICSharpCode.SharpZipLib.Zip.Compression
- {
- /// <summary>
- /// Strategies for deflater
- /// </summary>
- public enum DeflateStrategy
- {
- /// <summary>
- /// The default strategy
- /// </summary>
- Default = 0,
- /// <summary>
- /// This strategy will only allow longer string repetitions. It is
- /// useful for random data with a small character set.
- /// </summary>
- Filtered = 1,
- /// <summary>
- /// This strategy will not look for string repetitions at all. It
- /// only encodes with Huffman trees (which means, that more common
- /// characters get a smaller encoding.
- /// </summary>
- HuffmanOnly = 2
- }
- // DEFLATE ALGORITHM:
- //
- // The uncompressed stream is inserted into the window array. When
- // the window array is full the first half is thrown away and the
- // second half is copied to the beginning.
- //
- // The head array is a hash table. Three characters build a hash value
- // and they the value points to the corresponding index in window of
- // the last string with this hash. The prev array implements a
- // linked list of matches with the same hash: prev[index & WMASK] points
- // to the previous index with the same hash.
- //
- /// <summary>
- /// Low level compression engine for deflate algorithm which uses a 32K sliding window
- /// with secondary compression from Huffman/Shannon-Fano codes.
- /// </summary>
- public class DeflaterEngine
- {
- #region Constants
- const int TooFar = 4096;
- #endregion
- #region Constructors
- /// <summary>
- /// Construct instance with pending buffer
- /// </summary>
- /// <param name="pending">
- /// Pending buffer to use
- /// </param>>
- public DeflaterEngine(DeflaterPending pending)
- {
- this.pending = pending;
- huffman = new DeflaterHuffman(pending);
- adler = new Adler32();
- window = new byte[2 * DeflaterConstants.WSIZE];
- head = new short[DeflaterConstants.HASH_SIZE];
- prev = new short[DeflaterConstants.WSIZE];
- // We start at index 1, to avoid an implementation deficiency, that
- // we cannot build a repeat pattern at index 0.
- blockStart = strstart = 1;
- }
- #endregion
- /// <summary>
- /// Deflate drives actual compression of data
- /// </summary>
- /// <param name="flush">True to flush input buffers</param>
- /// <param name="finish">Finish deflation with the current input.</param>
- /// <returns>Returns true if progress has been made.</returns>
- public bool Deflate(bool flush, bool finish)
- {
- bool progress;
- do {
- FillWindow();
- bool canFlush = flush && (inputOff == inputEnd);
- #if DebugDeflation
- if (DeflaterConstants.DEBUGGING) {
- Console.WriteLine("window: [" + blockStart + "," + strstart + ","
- + lookahead + "], " + compressionFunction + "," + canFlush);
- }
- #endif
- switch (compressionFunction) {
- case DeflaterConstants.DEFLATE_STORED:
- progress = DeflateStored(canFlush, finish);
- break;
- case DeflaterConstants.DEFLATE_FAST:
- progress = DeflateFast(canFlush, finish);
- break;
- case DeflaterConstants.DEFLATE_SLOW:
- progress = DeflateSlow(canFlush, finish);
- break;
- default:
- throw new InvalidOperationException("unknown compressionFunction");
- }
- } while (pending.IsFlushed && progress); // repeat while we have no pending output and progress was made
- return progress;
- }
- /// <summary>
- /// Sets input data to be deflated. Should only be called when <code>NeedsInput()</code>
- /// returns true
- /// </summary>
- /// <param name="buffer">The buffer containing input data.</param>
- /// <param name="offset">The offset of the first byte of data.</param>
- /// <param name="count">The number of bytes of data to use as input.</param>
- public void SetInput(byte[] buffer, int offset, int count)
- {
- if (buffer == null) {
- throw new ArgumentNullException("nameof(buffer)");
- }
- if (offset < 0) {
- throw new ArgumentOutOfRangeException("nameof(offset)");
- }
- if (count < 0) {
- throw new ArgumentOutOfRangeException("nameof(count)");
- }
- if (inputOff < inputEnd) {
- throw new InvalidOperationException("Old input was not completely processed");
- }
- int end = offset + count;
- /* We want to throw an ArrayIndexOutOfBoundsException early. The
- * check is very tricky: it also handles integer wrap around.
- */
- if ((offset > end) || (end > buffer.Length)) {
- throw new ArgumentOutOfRangeException("nameof(count)");
- }
- inputBuf = buffer;
- inputOff = offset;
- inputEnd = end;
- }
- /// <summary>
- /// Determines if more <see cref="SetInput">input</see> is needed.
- /// </summary>
- /// <returns>Return true if input is needed via <see cref="SetInput">SetInput</see></returns>
- public bool NeedsInput()
- {
- return (inputEnd == inputOff);
- }
- /// <summary>
- /// Set compression dictionary
- /// </summary>
- /// <param name="buffer">The buffer containing the dictionary data</param>
- /// <param name="offset">The offset in the buffer for the first byte of data</param>
- /// <param name="length">The length of the dictionary data.</param>
- public void SetDictionary(byte[] buffer, int offset, int length)
- {
- #if DebugDeflation
- if (DeflaterConstants.DEBUGGING && (strstart != 1) )
- {
- throw new InvalidOperationException("strstart not 1");
- }
- #endif
- adler.Update(buffer, offset, length);
- if (length < DeflaterConstants.MIN_MATCH) {
- return;
- }
- if (length > DeflaterConstants.MAX_DIST) {
- offset += length - DeflaterConstants.MAX_DIST;
- length = DeflaterConstants.MAX_DIST;
- }
- System.Array.Copy(buffer, offset, window, strstart, length);
- UpdateHash();
- --length;
- while (--length > 0) {
- InsertString();
- strstart++;
- }
- strstart += 2;
- blockStart = strstart;
- }
- /// <summary>
- /// Reset internal state
- /// </summary>
- public void Reset()
- {
- huffman.Reset();
- adler.Reset();
- blockStart = strstart = 1;
- lookahead = 0;
- totalIn = 0;
- prevAvailable = false;
- matchLen = DeflaterConstants.MIN_MATCH - 1;
- for (int i = 0; i < DeflaterConstants.HASH_SIZE; i++) {
- head[i] = 0;
- }
- for (int i = 0; i < DeflaterConstants.WSIZE; i++) {
- prev[i] = 0;
- }
- }
- /// <summary>
- /// Reset Adler checksum
- /// </summary>
- public void ResetAdler()
- {
- adler.Reset();
- }
- /// <summary>
- /// Get current value of Adler checksum
- /// </summary>
- public int Adler {
- get {
- return unchecked((int)adler.Value);
- }
- }
- /// <summary>
- /// Total data processed
- /// </summary>
- public long TotalIn {
- get {
- return totalIn;
- }
- }
- /// <summary>
- /// Get/set the <see cref="DeflateStrategy">deflate strategy</see>
- /// </summary>
- public DeflateStrategy Strategy {
- get {
- return strategy;
- }
- set {
- strategy = value;
- }
- }
- /// <summary>
- /// Set the deflate level (0-9)
- /// </summary>
- /// <param name="level">The value to set the level to.</param>
- public void SetLevel(int level)
- {
- if ((level < 0) || (level > 9)) {
- throw new ArgumentOutOfRangeException("nameof(level)");
- }
- goodLength = DeflaterConstants.GOOD_LENGTH[level];
- max_lazy = DeflaterConstants.MAX_LAZY[level];
- niceLength = DeflaterConstants.NICE_LENGTH[level];
- max_chain = DeflaterConstants.MAX_CHAIN[level];
- if (DeflaterConstants.COMPR_FUNC[level] != compressionFunction) {
- #if DebugDeflation
- if (DeflaterConstants.DEBUGGING) {
- Console.WriteLine("Change from " + compressionFunction + " to "
- + DeflaterConstants.COMPR_FUNC[level]);
- }
- #endif
- switch (compressionFunction) {
- case DeflaterConstants.DEFLATE_STORED:
- if (strstart > blockStart) {
- huffman.FlushStoredBlock(window, blockStart,
- strstart - blockStart, false);
- blockStart = strstart;
- }
- UpdateHash();
- break;
- case DeflaterConstants.DEFLATE_FAST:
- if (strstart > blockStart) {
- huffman.FlushBlock(window, blockStart, strstart - blockStart,
- false);
- blockStart = strstart;
- }
- break;
- case DeflaterConstants.DEFLATE_SLOW:
- if (prevAvailable) {
- huffman.TallyLit(window[strstart - 1] & 0xff);
- }
- if (strstart > blockStart) {
- huffman.FlushBlock(window, blockStart, strstart - blockStart, false);
- blockStart = strstart;
- }
- prevAvailable = false;
- matchLen = DeflaterConstants.MIN_MATCH - 1;
- break;
- }
- compressionFunction = DeflaterConstants.COMPR_FUNC[level];
- }
- }
- /// <summary>
- /// Fill the window
- /// </summary>
- public void FillWindow()
- {
- /* If the window is almost full and there is insufficient lookahead,
- * move the upper half to the lower one to make room in the upper half.
- */
- if (strstart >= DeflaterConstants.WSIZE + DeflaterConstants.MAX_DIST) {
- SlideWindow();
- }
- /* If there is not enough lookahead, but still some input left,
- * read in the input
- */
- if (lookahead < DeflaterConstants.MIN_LOOKAHEAD && inputOff < inputEnd) {
- int more = 2 * DeflaterConstants.WSIZE - lookahead - strstart;
- if (more > inputEnd - inputOff) {
- more = inputEnd - inputOff;
- }
- System.Array.Copy(inputBuf, inputOff, window, strstart + lookahead, more);
- adler.Update(inputBuf, inputOff, more);
- inputOff += more;
- totalIn += more;
- lookahead += more;
- }
- if (lookahead >= DeflaterConstants.MIN_MATCH) {
- UpdateHash();
- }
- }
- void UpdateHash()
- {
- /*
- if (DEBUGGING) {
- Console.WriteLine("updateHash: "+strstart);
- }
- */
- ins_h = (window[strstart] << DeflaterConstants.HASH_SHIFT) ^ window[strstart + 1];
- }
- /// <summary>
- /// Inserts the current string in the head hash and returns the previous
- /// value for this hash.
- /// </summary>
- /// <returns>The previous hash value</returns>
- int InsertString()
- {
- short match;
- int hash = ((ins_h << DeflaterConstants.HASH_SHIFT) ^ window[strstart + (DeflaterConstants.MIN_MATCH - 1)]) & DeflaterConstants.HASH_MASK;
- #if DebugDeflation
- if (DeflaterConstants.DEBUGGING)
- {
- if (hash != (((window[strstart] << (2*HASH_SHIFT)) ^
- (window[strstart + 1] << HASH_SHIFT) ^
- (window[strstart + 2])) & HASH_MASK)) {
- throw new SharpZipBaseException("hash inconsistent: " + hash + "/"
- +window[strstart] + ","
- +window[strstart + 1] + ","
- +window[strstart + 2] + "," + HASH_SHIFT);
- }
- }
- #endif
- prev[strstart & DeflaterConstants.WMASK] = match = head[hash];
- head[hash] = unchecked((short)strstart);
- ins_h = hash;
- return match & 0xffff;
- }
- void SlideWindow()
- {
- Array.Copy(window, DeflaterConstants.WSIZE, window, 0, DeflaterConstants.WSIZE);
- matchStart -= DeflaterConstants.WSIZE;
- strstart -= DeflaterConstants.WSIZE;
- blockStart -= DeflaterConstants.WSIZE;
- // Slide the hash table (could be avoided with 32 bit values
- // at the expense of memory usage).
- for (int i = 0; i < DeflaterConstants.HASH_SIZE; ++i) {
- int m = head[i] & 0xffff;
- head[i] = (short)(m >= DeflaterConstants.WSIZE ? (m - DeflaterConstants.WSIZE) : 0);
- }
- // Slide the prev table.
- for (int i = 0; i < DeflaterConstants.WSIZE; i++) {
- int m = prev[i] & 0xffff;
- prev[i] = (short)(m >= DeflaterConstants.WSIZE ? (m - DeflaterConstants.WSIZE) : 0);
- }
- }
- /// <summary>
- /// Find the best (longest) string in the window matching the
- /// string starting at strstart.
- ///
- /// Preconditions:
- /// <code>
- /// strstart + DeflaterConstants.MAX_MATCH <= window.length.</code>
- /// </summary>
- /// <param name="curMatch"></param>
- /// <returns>True if a match greater than the minimum length is found</returns>
- bool FindLongestMatch( int curMatch )
- {
- int match;
- int scan = strstart;
- // scanMax is the highest position that we can look at
- int scanMax = scan + Math.Min( DeflaterConstants.MAX_MATCH, lookahead ) - 1;
- int limit = Math.Max( scan - DeflaterConstants.MAX_DIST, 0 );
- byte[] window = this.window;
- short[] prev = this.prev;
- int chainLength = this.max_chain;
- int niceLength = Math.Min( this.niceLength, lookahead );
- matchLen = Math.Max( matchLen, DeflaterConstants.MIN_MATCH - 1 );
- if (scan + matchLen > scanMax) return false;
- byte scan_end1 = window[scan + matchLen - 1];
- byte scan_end = window[scan + matchLen];
- // Do not waste too much time if we already have a good match:
- if (matchLen >= this.goodLength) chainLength >>= 2;
- do
- {
- match = curMatch;
- scan = strstart;
- if (window[match + matchLen] != scan_end
- || window[match + matchLen - 1] != scan_end1
- || window[match] != window[scan]
- || window[++match] != window[++scan])
- {
- continue;
- }
- // scan is set to strstart+1 and the comparison passed, so
- // scanMax - scan is the maximum number of bytes we can compare.
- // below we compare 8 bytes at a time, so first we compare
- // (scanMax - scan) % 8 bytes, so the remainder is a multiple of 8
- switch( (scanMax - scan) % 8 )
- {
- case 1: if (window[++scan] == window[++match]) break;
- break;
- case 2: if (window[++scan] == window[++match]
- && window[++scan] == window[++match]) break;
- break;
- case 3: if (window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]) break;
- break;
- case 4: if (window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]) break;
- break;
- case 5: if (window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]) break;
- break;
- case 6: if (window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]) break;
- break;
- case 7: if (window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]) break;
- break;
- }
- if (window[scan] == window[match])
- {
- /* We check for insufficient lookahead only every 8th comparison;
- * the 256th check will be made at strstart + 258 unless lookahead is
- * exhausted first.
- */
- do
- {
- if (scan == scanMax)
- {
- ++scan; // advance to first position not matched
- ++match;
- break;
- }
- }
- while (window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]
- && window[++scan] == window[++match]);
- }
- if (scan - strstart > matchLen)
- {
- #if DebugDeflation
- if (DeflaterConstants.DEBUGGING && (ins_h == 0) )
- Console.Error.WriteLine("Found match: " + curMatch + "-" + (scan - strstart));
- #endif
- matchStart = curMatch;
- matchLen = scan - strstart;
- if (matchLen >= niceLength)
- break;
- scan_end1 = window[scan - 1];
- scan_end = window[scan];
- }
- } while ((curMatch = (prev[curMatch & DeflaterConstants.WMASK] & 0xffff)) > limit && 0 != --chainLength );
- return matchLen >= DeflaterConstants.MIN_MATCH;
- }
- bool DeflateStored(bool flush, bool finish)
- {
- if (!flush && (lookahead == 0)) {
- return false;
- }
- strstart += lookahead;
- lookahead = 0;
- int storedLength = strstart - blockStart;
- if ((storedLength >= DeflaterConstants.MAX_BLOCK_SIZE) || // Block is full
- (blockStart < DeflaterConstants.WSIZE && storedLength >= DeflaterConstants.MAX_DIST) || // Block may move out of window
- flush) {
- bool lastBlock = finish;
- if (storedLength > DeflaterConstants.MAX_BLOCK_SIZE) {
- storedLength = DeflaterConstants.MAX_BLOCK_SIZE;
- lastBlock = false;
- }
- #if DebugDeflation
- if (DeflaterConstants.DEBUGGING)
- {
- Console.WriteLine("storedBlock[" + storedLength + "," + lastBlock + "]");
- }
- #endif
- huffman.FlushStoredBlock(window, blockStart, storedLength, lastBlock);
- blockStart += storedLength;
- return !lastBlock;
- }
- return true;
- }
- bool DeflateFast(bool flush, bool finish)
- {
- if (lookahead < DeflaterConstants.MIN_LOOKAHEAD && !flush) {
- return false;
- }
- while (lookahead >= DeflaterConstants.MIN_LOOKAHEAD || flush) {
- if (lookahead == 0) {
- // We are flushing everything
- huffman.FlushBlock(window, blockStart, strstart - blockStart, finish);
- blockStart = strstart;
- return false;
- }
- if (strstart > 2 * DeflaterConstants.WSIZE - DeflaterConstants.MIN_LOOKAHEAD) {
- /* slide window, as FindLongestMatch needs this.
- * This should only happen when flushing and the window
- * is almost full.
- */
- SlideWindow();
- }
- int hashHead;
- if (lookahead >= DeflaterConstants.MIN_MATCH &&
- (hashHead = InsertString()) != 0 &&
- strategy != DeflateStrategy.HuffmanOnly &&
- strstart - hashHead <= DeflaterConstants.MAX_DIST &&
- FindLongestMatch(hashHead)) {
- // longestMatch sets matchStart and matchLen
- #if DebugDeflation
- if (DeflaterConstants.DEBUGGING)
- {
- for (int i = 0 ; i < matchLen; i++) {
- if (window[strstart + i] != window[matchStart + i]) {
- throw new SharpZipBaseException("Match failure");
- }
- }
- }
- #endif
- bool full = huffman.TallyDist(strstart - matchStart, matchLen);
- lookahead -= matchLen;
- if (matchLen <= max_lazy && lookahead >= DeflaterConstants.MIN_MATCH) {
- while (--matchLen > 0) {
- ++strstart;
- InsertString();
- }
- ++strstart;
- } else {
- strstart += matchLen;
- if (lookahead >= DeflaterConstants.MIN_MATCH - 1) {
- UpdateHash();
- }
- }
- matchLen = DeflaterConstants.MIN_MATCH - 1;
- if (!full) {
- continue;
- }
- } else {
- // No match found
- huffman.TallyLit(window[strstart] & 0xff);
- ++strstart;
- --lookahead;
- }
- if (huffman.IsFull()) {
- bool lastBlock = finish && (lookahead == 0);
- huffman.FlushBlock(window, blockStart, strstart - blockStart, lastBlock);
- blockStart = strstart;
- return !lastBlock;
- }
- }
- return true;
- }
- bool DeflateSlow(bool flush, bool finish)
- {
- if (lookahead < DeflaterConstants.MIN_LOOKAHEAD && !flush) {
- return false;
- }
- while (lookahead >= DeflaterConstants.MIN_LOOKAHEAD || flush) {
- if (lookahead == 0) {
- if (prevAvailable) {
- huffman.TallyLit(window[strstart - 1] & 0xff);
- }
- prevAvailable = false;
- // We are flushing everything
- #if DebugDeflation
- if (DeflaterConstants.DEBUGGING && !flush)
- {
- throw new SharpZipBaseException("Not flushing, but no lookahead");
- }
- #endif
- huffman.FlushBlock(window, blockStart, strstart - blockStart,
- finish);
- blockStart = strstart;
- return false;
- }
- if (strstart >= 2 * DeflaterConstants.WSIZE - DeflaterConstants.MIN_LOOKAHEAD) {
- /* slide window, as FindLongestMatch needs this.
- * This should only happen when flushing and the window
- * is almost full.
- */
- SlideWindow();
- }
- int prevMatch = matchStart;
- int prevLen = matchLen;
- if (lookahead >= DeflaterConstants.MIN_MATCH) {
- int hashHead = InsertString();
- if (strategy != DeflateStrategy.HuffmanOnly &&
- hashHead != 0 &&
- strstart - hashHead <= DeflaterConstants.MAX_DIST &&
- FindLongestMatch(hashHead)) {
- // longestMatch sets matchStart and matchLen
- // Discard match if too small and too far away
- if (matchLen <= 5 && (strategy == DeflateStrategy.Filtered || (matchLen == DeflaterConstants.MIN_MATCH && strstart - matchStart > TooFar))) {
- matchLen = DeflaterConstants.MIN_MATCH - 1;
- }
- }
- }
- // previous match was better
- if ((prevLen >= DeflaterConstants.MIN_MATCH) && (matchLen <= prevLen)) {
- #if DebugDeflation
- if (DeflaterConstants.DEBUGGING)
- {
- for (int i = 0 ; i < matchLen; i++) {
- if (window[strstart-1+i] != window[prevMatch + i])
- throw new SharpZipBaseException();
- }
- }
- #endif
- huffman.TallyDist(strstart - 1 - prevMatch, prevLen);
- prevLen -= 2;
- do {
- strstart++;
- lookahead--;
- if (lookahead >= DeflaterConstants.MIN_MATCH) {
- InsertString();
- }
- } while (--prevLen > 0);
- strstart++;
- lookahead--;
- prevAvailable = false;
- matchLen = DeflaterConstants.MIN_MATCH - 1;
- } else {
- if (prevAvailable) {
- huffman.TallyLit(window[strstart - 1] & 0xff);
- }
- prevAvailable = true;
- strstart++;
- lookahead--;
- }
- if (huffman.IsFull()) {
- int len = strstart - blockStart;
- if (prevAvailable) {
- len--;
- }
- bool lastBlock = (finish && (lookahead == 0) && !prevAvailable);
- huffman.FlushBlock(window, blockStart, len, lastBlock);
- blockStart += len;
- return !lastBlock;
- }
- }
- return true;
- }
- #region Instance Fields
- // Hash index of string to be inserted
- int ins_h;
- /// <summary>
- /// Hashtable, hashing three characters to an index for window, so
- /// that window[index]..window[index+2] have this hash code.
- /// Note that the array should really be unsigned short, so you need
- /// to and the values with 0xffff.
- /// </summary>
- short[] head;
- /// <summary>
- /// <code>prev[index & WMASK]</code> points to the previous index that has the
- /// same hash code as the string starting at index. This way
- /// entries with the same hash code are in a linked list.
- /// Note that the array should really be unsigned short, so you need
- /// to and the values with 0xffff.
- /// </summary>
- short[] prev;
- int matchStart;
- // Length of best match
- int matchLen;
- // Set if previous match exists
- bool prevAvailable;
- int blockStart;
- /// <summary>
- /// Points to the current character in the window.
- /// </summary>
- int strstart;
- /// <summary>
- /// lookahead is the number of characters starting at strstart in
- /// window that are valid.
- /// So window[strstart] until window[strstart+lookahead-1] are valid
- /// characters.
- /// </summary>
- int lookahead;
- /// <summary>
- /// This array contains the part of the uncompressed stream that
- /// is of relevance. The current character is indexed by strstart.
- /// </summary>
- byte[] window;
- DeflateStrategy strategy;
- int max_chain, max_lazy, niceLength, goodLength;
- /// <summary>
- /// The current compression function.
- /// </summary>
- int compressionFunction;
- /// <summary>
- /// The input data for compression.
- /// </summary>
- byte[] inputBuf;
- /// <summary>
- /// The total bytes of input read.
- /// </summary>
- long totalIn;
- /// <summary>
- /// The offset into inputBuf, where input data starts.
- /// </summary>
- int inputOff;
- /// <summary>
- /// The end offset of the input data.
- /// </summary>
- int inputEnd;
- DeflaterPending pending;
- DeflaterHuffman huffman;
- /// <summary>
- /// The adler checksum
- /// </summary>
- Adler32 adler;
- #endregion
- }
- }
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