///////////////////////////////////////////////////////////////////////////

//

// Copyright (c) 2002, Industrial Light & Magic, a division of Lucas

// Digital Ltd. LLC

// 

// All rights reserved.

// 

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

// *       Redistributions of source code must retain the above copyright

// notice, this list of conditions and the following disclaimer.

// *       Redistributions in binary form must reproduce the above

// copyright notice, this list of conditions and the following disclaimer

// in the documentation and/or other materials provided with the

// distribution.

// *       Neither the name of Industrial Light & Magic nor the names of

// its contributors may be used to endorse or promote products derived

// from this software without specific prior written permission. 

// 

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

//

///////////////////////////////////////////////////////////////////////////

//-----------------------------------------------------------------------------

//

//	16-bit Huffman compression and decompression.

//

//	The source code in this file is derived from the 8-bit

//	Huffman compression and decompression routines written

//	by Christian Rouet for his PIZ image file format.

//

//-----------------------------------------------------------------------------

#include <ImfHuf.h>

#include <ImfInt64.h>

#include "ImfAutoArray.h"

#include "ImfFastHuf.h"

#include "Iex.h"

#include <cstring>

#include <cassert>

#include <algorithm>

using namespace std;

using namespace IEX_NAMESPACE;

#include "ImfNamespace.h"

OPENEXR_IMF_INTERNAL_NAMESPACE_SOURCE_ENTER

namespace {

const int HUF_ENCBITS = 16;			// literal (value) bit length

const int HUF_DECBITS = 14;			// decoding bit size (>= 8)

const int HUF_ENCSIZE = (1 << HUF_ENCBITS) + 1;	// encoding table size

const int HUF_DECSIZE =  1 << HUF_DECBITS;	// decoding table size

const int HUF_DECMASK = HUF_DECSIZE - 1;

struct HufDec

{				// short code		long code

				//-------------------------------

    int		len:8;		// code length		0	 

    int		lit:24;		// lit			p size	 

    int	*	p;		// 0			lits	 

};

void

invalidNBits ()

{

    throw InputExc ("Error in header for Huffman-encoded data "

		    "(invalid number of bits).");

}

void

tooMuchData ()

{

    throw InputExc ("Error in Huffman-encoded data "

		    "(decoded data are longer than expected).");

}

void

notEnoughData ()

{

    throw InputExc ("Error in Huffman-encoded data "

		    "(decoded data are shorter than expected).");

}

void

invalidCode ()

{

    throw InputExc ("Error in Huffman-encoded data "

		    "(invalid code).");

}

void

invalidTableSize ()

{

    throw InputExc ("Error in Huffman-encoded data "

		    "(invalid code table size).");

}

void

unexpectedEndOfTable ()

{

    throw InputExc ("Error in Huffman-encoded data "

		    "(unexpected end of code table data).");

}

void

tableTooLong ()

{

    throw InputExc ("Error in Huffman-encoded data "

		    "(code table is longer than expected).");

}

void

invalidTableEntry ()

{

    throw InputExc ("Error in Huffman-encoded data "

		    "(invalid code table entry).");

}

inline Int64

hufLength (Int64 code)

{

    return code & 63;

}

inline Int64

hufCode (Int64 code)

{

    return code >> 6;

}

inline void

outputBits (int nBits, Int64 bits, Int64 &c, int &lc, char *&out)

{

    c <<= nBits;

    lc += nBits;

    c |= bits;

    while (lc >= 8)

	*out++ = (c >> (lc -= 8));

}

inline Int64

getBits (int nBits, Int64 &c, int &lc, const char *&in)

{

    while (lc < nBits)

    {

	c = (c << 8) | *(unsigned char *)(in++);

	lc += 8;

    }

    lc -= nBits;

    return (c >> lc) & ((1 << nBits) - 1);

}

//

// ENCODING TABLE BUILDING & (UN)PACKING

//

//

// Build a "canonical" Huffman code table:

//	- for each (uncompressed) symbol, hcode contains the length

//	  of the corresponding code (in the compressed data)

//	- canonical codes are computed and stored in hcode

//	- the rules for constructing canonical codes are as follows:

//	  * shorter codes (if filled with zeroes to the right)

//	    have a numerically higher value than longer codes

//	  * for codes with the same length, numerical values

//	    increase with numerical symbol values

//	- because the canonical code table can be constructed from

//	  symbol lengths alone, the code table can be transmitted

//	  without sending the actual code values

//	- see http://www.compressconsult.com/huffman/

//

void

hufCanonicalCodeTable (Int64 hcode[HUF_ENCSIZE])

{

    Int64 n[59];

    //

    // For each i from 0 through 58, count the

    // number of different codes of length i, and

    // store the count in n[i].

    //

    for (int i = 0; i <= 58; ++i)

	n[i] = 0;

    for (int i = 0; i < HUF_ENCSIZE; ++i)

	n[hcode[i]] += 1;

    //

    // For each i from 58 through 1, compute the

    // numerically lowest code with length i, and

    // store that code in n[i].

    //

    Int64 c = 0;

    for (int i = 58; i > 0; --i)

    {

	Int64 nc = ((c + n[i]) >> 1);

	n[i] = c;

	c = nc;

    }

    //

    // hcode[i] contains the length, l, of the

    // code for symbol i.  Assign the next available

    // code of length l to the symbol and store both

    // l and the code in hcode[i].

    //

    for (int i = 0; i < HUF_ENCSIZE; ++i)

    {

	int l = hcode[i];

	if (l > 0)

	    hcode[i] = l | (n[l]++ << 6);

    }

}

//

// Compute Huffman codes (based on frq input) and store them in frq:

//	- code structure is : [63:lsb - 6:msb] | [5-0: bit length];

//	- max code length is 58 bits;

//	- codes outside the range [im-iM] have a null length (unused values);

//	- original frequencies are destroyed;

//	- encoding tables are used by hufEncode() and hufBuildDecTable();

//

struct FHeapCompare

{

    bool operator () (Int64 *a, Int64 *b) {return *a > *b;}

};

void

hufBuildEncTable

    (Int64*	frq,	// io: input frequencies [HUF_ENCSIZE], output table

     int*	im,	//  o: min frq index

     int*	iM)	//  o: max frq index

{

    //

    // This function assumes that when it is called, array frq

    // indicates the frequency of all possible symbols in the data

    // that are to be Huffman-encoded.  (frq[i] contains the number

    // of occurrences of symbol i in the data.)

    //

    // The loop below does three things:

    //

    // 1) Finds the minimum and maximum indices that point

    //    to non-zero entries in frq:

    //

    //     frq[im] != 0, and frq[i] == 0 for all i < im

    //     frq[iM] != 0, and frq[i] == 0 for all i > iM

    //

    // 2) Fills array fHeap with pointers to all non-zero

    //    entries in frq.

    //

    // 3) Initializes array hlink such that hlink[i] == i

    //    for all array entries.

    //

    AutoArray <int, HUF_ENCSIZE> hlink;

    AutoArray <Int64 *, HUF_ENCSIZE> fHeap;

    *im = 0;

    while (!frq[*im])

	(*im)++;

    int nf = 0;

    for (int i = *im; i < HUF_ENCSIZE; i++)

    {

	hlink[i] = i;

	if (frq[i])

	{

	    fHeap[nf] = &frq[i];

	    nf++;

	    *iM = i;

	}

    }

    //

    // Add a pseudo-symbol, with a frequency count of 1, to frq;

    // adjust the fHeap and hlink array accordingly.  Function

    // hufEncode() uses the pseudo-symbol for run-length encoding.

    //

    (*iM)++;

    frq[*iM] = 1;

    fHeap[nf] = &frq[*iM];

    nf++;

    //

    // Build an array, scode, such that scode[i] contains the number

    // of bits assigned to symbol i.  Conceptually this is done by

    // constructing a tree whose leaves are the symbols with non-zero

    // frequency:

    //

    //     Make a heap that contains all symbols with a non-zero frequency,

    //     with the least frequent symbol on top.

    //

    //     Repeat until only one symbol is left on the heap:

    //

    //         Take the two least frequent symbols off the top of the heap.

    //         Create a new node that has first two nodes as children, and

    //         whose frequency is the sum of the frequencies of the first

    //         two nodes.  Put the new node back into the heap.

    //

    // The last node left on the heap is the root of the tree.  For each

    // leaf node, the distance between the root and the leaf is the length

    // of the code for the corresponding symbol.

    //

    // The loop below doesn't actually build the tree; instead we compute

    // the distances of the leaves from the root on the fly.  When a new

    // node is added to the heap, then that node's descendants are linked

    // into a single linear list that starts at the new node, and the code

    // lengths of the descendants (that is, their distance from the root

    // of the tree) are incremented by one.

    //

    make_heap (&fHeap[0], &fHeap[nf], FHeapCompare());

    AutoArray <Int64, HUF_ENCSIZE> scode;

    memset (scode, 0, sizeof (Int64) * HUF_ENCSIZE);

    while (nf > 1)

    {

	//

	// Find the indices, mm and m, of the two smallest non-zero frq

	// values in fHeap, add the smallest frq to the second-smallest

	// frq, and remove the smallest frq value from fHeap.

	//

	int mm = fHeap[0] - frq;

	pop_heap (&fHeap[0], &fHeap[nf], FHeapCompare());

	--nf;

	int m = fHeap[0] - frq;

	pop_heap (&fHeap[0], &fHeap[nf], FHeapCompare());

	frq[m ] += frq[mm];

	push_heap (&fHeap[0], &fHeap[nf], FHeapCompare());

	//

	// The entries in scode are linked into lists with the

	// entries in hlink serving as "next" pointers and with

	// the end of a list marked by hlink[j] == j.

	//

	// Traverse the lists that start at scode[m] and scode[mm].

	// For each element visited, increment the length of the

	// corresponding code by one bit. (If we visit scode[j]

	// during the traversal, then the code for symbol j becomes

	// one bit longer.)

	//

	// Merge the lists that start at scode[m] and scode[mm]

	// into a single list that starts at scode[m].

	//

	//

	// Add a bit to all codes in the first list.

	//

	for (int j = m; true; j = hlink[j])

	{

	    scode[j]++;

	    assert (scode[j] <= 58);

	    if (hlink[j] == j)

	    {

		//

		// Merge the two lists.

		//

		hlink[j] = mm;

		break;

	    }

	}

	//

	// Add a bit to all codes in the second list

	//

	for (int j = mm; true; j = hlink[j])

	{

	    scode[j]++;

	    assert (scode[j] <= 58);

	    if (hlink[j] == j)

		break;

	}

    }

    //

    // Build a canonical Huffman code table, replacing the code

    // lengths in scode with (code, code length) pairs.  Copy the

    // code table from scode into frq.

    //

    hufCanonicalCodeTable (scode);

    memcpy (frq, scode, sizeof (Int64) * HUF_ENCSIZE);

}

//

// Pack an encoding table:

//	- only code lengths, not actual codes, are stored

//	- runs of zeroes are compressed as follows:

//

//	  unpacked		packed

//	  --------------------------------

//	  1 zero		0	(6 bits)

//	  2 zeroes		59

//	  3 zeroes		60

//	  4 zeroes		61

//	  5 zeroes		62

//	  n zeroes (6 or more)	63 n-6	(6 + 8 bits)

//

const int SHORT_ZEROCODE_RUN = 59;

const int LONG_ZEROCODE_RUN  = 63;

const int SHORTEST_LONG_RUN  = 2 + LONG_ZEROCODE_RUN - SHORT_ZEROCODE_RUN;

const int LONGEST_LONG_RUN   = 255 + SHORTEST_LONG_RUN;

void

hufPackEncTable

    (const Int64*	hcode,		// i : encoding table [HUF_ENCSIZE]

     int		im,		// i : min hcode index

     int		iM,		// i : max hcode index

     char**		pcode)		//  o: ptr to packed table (updated)

{

    char *p = *pcode;

    Int64 c = 0;

    int lc = 0;

    for (; im <= iM; im++)

    {

	int l = hufLength (hcode[im]);

	if (l == 0)

	{

	    int zerun = 1;

	    while ((im < iM) && (zerun < LONGEST_LONG_RUN))

	    {

		if (hufLength (hcode[im+1]) > 0 )	 

		    break;

		im++;

		zerun++;

	    }

	    if (zerun >= 2)

	    {

		if (zerun >= SHORTEST_LONG_RUN)

		{

		    outputBits (6, LONG_ZEROCODE_RUN, c, lc, p);

		    outputBits (8, zerun - SHORTEST_LONG_RUN, c, lc, p);

		}

		else

		{

		    outputBits (6, SHORT_ZEROCODE_RUN + zerun - 2, c, lc, p);

		}

		continue;

	    }

	}

	outputBits (6, l, c, lc, p);

    }

    if (lc > 0)

	*p++ = (unsigned char) (c << (8 - lc));

    *pcode = p;

}

//

// Unpack an encoding table packed by hufPackEncTable():

//

void

hufUnpackEncTable

    (const char**	pcode,		// io: ptr to packed table (updated)

     int		ni,		// i : input size (in bytes)

     int		im,		// i : min hcode index

     int		iM,		// i : max hcode index

     Int64*		hcode)		//  o: encoding table [HUF_ENCSIZE]

{

    memset (hcode, 0, sizeof (Int64) * HUF_ENCSIZE);

    const char *p = *pcode;

    Int64 c = 0;

    int lc = 0;

    for (; im <= iM; im++)

    {

	if (p - *pcode > ni)

	    unexpectedEndOfTable();

	Int64 l = hcode[im] = getBits (6, c, lc, p); // code length

	if (l == (Int64) LONG_ZEROCODE_RUN)

	{

	    if (p - *pcode > ni)

		unexpectedEndOfTable();

	    int zerun = getBits (8, c, lc, p) + SHORTEST_LONG_RUN;

	    if (im + zerun > iM + 1)

		tableTooLong();

	    while (zerun--)

		hcode[im++] = 0;

	    im--;

	}

	else if (l >= (Int64) SHORT_ZEROCODE_RUN)

	{

	    int zerun = l - SHORT_ZEROCODE_RUN + 2;

	    if (im + zerun > iM + 1)

		tableTooLong();

	    while (zerun--)

		hcode[im++] = 0;

	    im--;

	}

    }

    *pcode = const_cast<char *>(p);

    hufCanonicalCodeTable (hcode);

}

//

// DECODING TABLE BUILDING

//

//

// Clear a newly allocated decoding table so that it contains only zeroes.

//

void

hufClearDecTable

    (HufDec *		hdecod)		// io: (allocated by caller)

     					//     decoding table [HUF_DECSIZE]

{

    memset (hdecod, 0, sizeof (HufDec) * HUF_DECSIZE);

}

//

// Build a decoding hash table based on the encoding table hcode:

//	- short codes (<= HUF_DECBITS) are resolved with a single table access;

//	- long code entry allocations are not optimized, because long codes are

//	  unfrequent;

//	- decoding tables are used by hufDecode();

//

void

hufBuildDecTable

    (const Int64*	hcode,		// i : encoding table

     int		im,		// i : min index in hcode

     int		iM,		// i : max index in hcode

     HufDec *		hdecod)		//  o: (allocated by caller)

     					//     decoding table [HUF_DECSIZE]

{

    //

    // Init hashtable & loop on all codes.

    // Assumes that hufClearDecTable(hdecod) has already been called.

    //

    for (; im <= iM; im++)

    {

	Int64 c = hufCode (hcode[im]);

	int l = hufLength (hcode[im]);

	if (c >> l)

	{

	    //

	    // Error: c is supposed to be an l-bit code,

	    // but c contains a value that is greater

	    // than the largest l-bit number.

	    //

	    invalidTableEntry();

	}

	if (l > HUF_DECBITS)

	{

	    //

	    // Long code: add a secondary entry

	    //

	    HufDec *pl = hdecod + (c >> (l - HUF_DECBITS));

	    if (pl->len)

	    {

		//

		// Error: a short code has already

		// been stored in table entry *pl.

		//

		invalidTableEntry();

	    }

	    pl->lit++;

	    if (pl->p)

	    {

		int *p = pl->p;

		pl->p = new int [pl->lit];

		for (int i = 0; i < pl->lit - 1; ++i)

		    pl->p[i] = p[i];

		delete [] p;

	    }

	    else

	    {

		pl->p = new int [1];

	    }

	    pl->p[pl->lit - 1]= im;

	}

	else if (l)

	{

	    //

	    // Short code: init all primary entries

	    //

	    HufDec *pl = hdecod + (c << (HUF_DECBITS - l));

	    for (Int64 i = 1 << (HUF_DECBITS - l); i > 0; i--, pl++)

	    {

		if (pl->len || pl->p)

		{

		    //

		    // Error: a short code or a long code has

		    // already been stored in table entry *pl.

		    //

		    invalidTableEntry();

		}

		pl->len = l;

		pl->lit = im;

	    }

	}

    }

}

//

// Free the long code entries of a decoding table built by hufBuildDecTable()

//

void

hufFreeDecTable (HufDec *hdecod)	// io: Decoding table

{

    for (int i = 0; i < HUF_DECSIZE; i++)

    {

	if (hdecod[i].p)

	{

	    delete [] hdecod[i].p;

	    hdecod[i].p = 0;

	}

    }

}

//

// ENCODING

//

inline void

outputCode (Int64 code, Int64 &c, int &lc, char *&out)

{

    outputBits (hufLength (code), hufCode (code), c, lc, out);

}

inline void

sendCode (Int64 sCode, int runCount, Int64 runCode,

	  Int64 &c, int &lc, char *&out)

{

    //

    // Output a run of runCount instances of the symbol sCount.

    // Output the symbols explicitly, or if that is shorter, output

    // the sCode symbol once followed by a runCode symbol and runCount

    // expressed as an 8-bit number.

    //

    if (hufLength (sCode) + hufLength (runCode) + 8 <

        hufLength (sCode) * runCount)

    {

	outputCode (sCode, c, lc, out);

	outputCode (runCode, c, lc, out);

	outputBits (8, runCount, c, lc, out);

    }

    else

    {

	while (runCount-- >= 0)

	    outputCode (sCode, c, lc, out);

    }

}

//

// Encode (compress) ni values based on the Huffman encoding table hcode:

//

int

hufEncode				// return: output size (in bits)

    (const Int64*  	    hcode,	// i : encoding table

     const unsigned short*  in,		// i : uncompressed input buffer

     const int     	    ni,		// i : input buffer size (in bytes)

     int           	    rlc,	// i : rl code

     char*         	    out)	//  o: compressed output buffer

{

    char *outStart = out;

    Int64 c = 0;	// bits not yet written to out

    int lc = 0;		// number of valid bits in c (LSB)

    int s = in[0];

    int cs = 0;

    //

    // Loop on input values

    //

    for (int i = 1; i < ni; i++)

    {

	//

	// Count same values or send code

	//

	if (s == in[i] && cs < 255)

	{

	    cs++;

	}

	else

	{

	    sendCode (hcode[s], cs, hcode[rlc], c, lc, out);

	    cs=0;

	}

	s = in[i];

    }

    //

    // Send remaining code

    //

    sendCode (hcode[s], cs, hcode[rlc], c, lc, out);

    if (lc)

	*out = (c << (8 - lc)) & 0xff;

    return (out - outStart) * 8 + lc;

}

//

// DECODING

//

//

// In order to force the compiler to inline them,

// getChar() and getCode() are implemented as macros

// instead of "inline" functions.

//

#define getChar(c, lc, in)			\

{						\

    c = (c << 8) | *(unsigned char *)(in++);	\

    lc += 8;					\

}

#define getCode(po, rlc, c, lc, in, out, oe)	\

{						\

    if (po == rlc)				\

    {						\

	if (lc < 8)				\

	    getChar(c, lc, in);			\

						\

	lc -= 8;				\

						\

	unsigned char cs = (c >> lc);		\

						\

	if (out + cs > oe)			\

	    tooMuchData();			\

						\

	unsigned short s = out[-1];		\

						\

	while (cs-- > 0)			\

	    *out++ = s;				\

    }						\

    else if (out < oe)				\

    {						\

	*out++ = po;				\

    }						\

    else					\

    {						\

	tooMuchData();				\

    }						\

}

//

// Decode (uncompress) ni bits based on encoding & decoding tables:

//

void

hufDecode

    (const Int64 * 	hcode,	// i : encoding table

     const HufDec * 	hdecod,	// i : decoding table

     const char* 	in,	// i : compressed input buffer

     int		ni,	// i : input size (in bits)

     int		rlc,	// i : run-length code

     int		no,	// i : expected output size (in bytes)

     unsigned short*	out)	//  o: uncompressed output buffer

{

    Int64 c = 0;

    int lc = 0;

    unsigned short * outb = out;

    unsigned short * oe = out + no;

    const char * ie = in + (ni + 7) / 8; // input byte size

    //

    // Loop on input bytes

    //

    while (in < ie)

    {