H. Appendix H — Compression Source Code

 /*++

 Copyright (c) 2001-2002 Intel Corporation

 Module Name:

  Compress.c

 Abstract:

  Compression routine. The compression algorithm is a mixture of LZ77
  and Huffman Coding. LZ77 transforms the source data into a sequence
  of Original Characters and Pointers to repeated strings. This sequence
  is further divided into Blocks and Huffman codings are applied to each Block.

 Revision History:
 --*/

 #include <string.h>
 #include <stdlib.h>
 #include "eficommon.h"

 //
 // Macro Definitions
 //

 typedef INT16          NODE;
 #define UINT8_MAX      0xff
 #define UINT8_BIT      8
 #define THRESHOLD      3
 #define INIT_CRC       0
 #define WNDBIT         13
 #define WNDSIZ         (1U << WNDBIT)
 #define MAXMATCH       256
 #define PERC_FLAG      0x8000U
 #define CODE_BIT       16
 #define NIL            0
 #define MAX_HASH_VAL (3 * WNDSIZ + (WNDSIZ / 512 + 1) * UINT8_MAX)
 #define HASH(p, c) ((p) + ((c) << (WNDBIT - 9)) + WNDSIZ * 2)
 #define CRCPOLY        0xA001
 #define UPDATE_CRC(c) mCrc = mCrcTable[(mCrc ^ (c)) & 0xFF] ^ (mCrc
 >> UINT8_BIT)

 //
 // C: the Char&Len Set; P: the Position Set; T: the exTra Set
 //

 #define NC       (UINT8_MAX + MAXMATCH + 2 - THRESHOLD)
 #define CBIT       9
 #define NP       (WNDBIT + 1)
 #define PBIT     4
 #define NT       (CODE_BIT + 3)
 #define TBIT     5
 #if NT > NP
    #define NPT NT
 #else
    #define NPT NP
 #endif

 //
 // Function Prototypes
 //

 STATIC
 VOID
 PutDword(
   IN UINT32 Data
   );

 STATIC
 EFI_STATUS
 AllocateMemory (
  );

 STATIC
 VOID
 FreeMemory (
  );

 STATIC
 VOID
 InitSlide (
  );

 STATIC
 NODE
 Child (
   IN NODE q,
   IN UINT8 c
   );

 STATIC
 VOID
 MakeChild (
   IN NODE q,
   IN UINT8 c,
   IN NODE r
   );

 STATIC
 VOID
 Split (
   IN NODE Old
   );

 STATIC
 VOID
 InsertNode (
   );

 STATIC
 VOID
 DeleteNode (
   );

 STATIC
 VOID
 GetNextMatch (
   );

 STATIC
 EFI_STATUS
 Encode (
   );

 STATIC
 VOID
 CountTFreq (
   );

 STATIC
 VOID
 WritePTLen (
   IN INT32 n,
   IN INT32 nbit,
   IN INT32 Special
   );

 STATIC
 VOID
 WriteCLen (
  );

 STATIC
 VOID
 EncodeC (
 IN INT32 c
   );

 STATIC
 VOID
 EncodeP (
   IN UINT32 p
   );

 STATIC
 VOID
 SendBlock (
  );

 STATIC
 VOID
 Output (
   IN UINT32 c,
   IN UINT32 p
   );

 STATIC
 VOID
 HufEncodeStart (
  );

 STATIC
 VOID
 HufEncodeEnd (
  );

 STATIC
 VOID
 MakeCrcTable (
  );

 STATIC
 VOID
 PutBits (
   IN INT32 n,
   IN UINT32 x
   );

 STATIC
 INT32
 FreadCrc (
   OUT UINT8 *p,
   IN INT32 n
   );

 STATIC
 VOID
 InitPutBits (
  );

 STATIC
 VOID
 CountLen (
   IN INT32 i
   );

 STATIC
 VOID
 MakeLen (
   IN INT32 Root
   );

 STATIC
 VOID
 DownHeap (
   IN INT32 i
   );

 STATIC
 VOID
 MakeCode (
   IN INT32 n,
   IN UINT8 Len[],
   OUT UINT16 Code[]
   );

 STATIC
 INT32
 MakeTree (
   IN INT32 NParm,
   IN UINT16 FreqParm[],
   OUT UINT8 LenParm[],
   OUT UINT16 CodeParm[]
   );

 //
 // Global Variables
 //

 STATIC UINT8 *mSrc, *mDst, *mSrcUpperLimit, *mDstUpperLimit;

 STATIC UINT8 *mLevel, *mText, *mChildCount, *mBuf, mCLen[NC], mPTLen[NPT], *mLen;
 STATIC INT16 mHeap[NC + 1];
 STATIC INT32 mRemainder, mMatchLen, mBitCount, mHeapSize, mN;
 STATIC UINT32 mBufSiz = 0, mOutputPos, mOutputMask, mSubBitBuf, mCrc;
 STATIC UINT32 mCompSize, mOrigSize;

 STATIC UINT16 *mFreq, *mSortPtr, mLenCnt[17], mLeft[2 * NC - 1], mRight[2 * NC - 1],
        mCrcTable[UINT8_MAX + 1], mCFreq[2 * NC - 1], mCTable[4096], mCCode[NC],
        mPFreq[2 * NP - 1], mPTCode[NPT], mTFreq[2 * NT - 1];

 STATIC NODE mPos, mMatchPos, mAvail, *mPosition, *mParent, *mPrev, *mNext = NULL;


 //
 // functions
 //

 EFI_STATUS
 Compress (
   IN UINT8 *SrcBuffer,
   IN UINT32 SrcSize,
   IN UINT8 *DstBuffer,
   IN OUT UINT32 *DstSize
   )

 /*++

 Routine Description:

    The main compression routine.

 Arguments:

   SrcBuffer - The buffer storing the source data
   SrcSize - The size of the source data
   DstBuffer - The buffer to store the compressed data
   DstSize - On input, the size of DstBuffer; On output,
             the size of the actual compressed data.

 Returns:

 EFI_BUFFER_TOO_SMALL - The DstBuffer is too small. In this case,
      DstSize contains the size needed.
 EFI_SUCCESS - Compression is successful.

 --*/
 {
  EFI_STATUS Status = EFI_SUCCESS;

 //
 // Initializations
 //

 mBufSiz = 0;
 mBuf = NULL;
 mText = NULL;
 mLevel = NULL;
 mChildCount = NULL;
 mPosition = NULL;
 mParent = NULL;
 mPrev = NULL;
 mNext = NULL;

 mSrc = SrcBuffer;
 mSrcUpperLimit = mSrc + SrcSize;
 mDst = DstBuffer;
 mDstUpperLimit = mDst + *DstSize;

 PutDword(0L);
 PutDword(0L);

 MakeCrcTable ();

 mOrigSize = mCompSize = 0;
 mCrc = INIT_CRC;

 //
 // Compress it
 //

 Status = Encode();
 if (EFI_ERROR (Status)) {
  return EFI_OUT_OF_RESOURCES;
 }

 //
 // Null terminate the compressed data
 //
 if (mDst < mDstUpperLimit) {
    *mDst++ = 0;
 }

 //
 // Fill in compressed size and original size
 //
 mDst = DstBuffer;
 PutDword(mCompSize+1);
 PutDword(mOrigSize);

 //
 // Return
 //

 if (mCompSize + 1 + 8 > *DstSize) {   \
  *DstSize = mCompSize + 1 + 8;
  return EFI_BUFFER_TOO_SMALL;
 } else {
  *DstSize = mCompSize + 1 + 8;
  return EFI_SUCCESS;
 }

 }

 STATIC
 VOID
 PutDword(
   IN UINT32 Data
   )
 /*++

 Routine Description:

  Put a dword to output stream

 Arguments:

  Data - the dword to put

 Returns: (VOID)

 --*/
 {
  if (mDst < mDstUpperLimit) {
    *mDst++ = (UINT8)(((UINT8)(Data )) & 0xff);
 }

 if (mDst < mDstUpperLimit) {
  *mDst++ = (UINT8)(((UINT8)(Data >> 0x08)) & 0xff);
 }

 if (mDst < mDstUpperLimit) {
  *mDst++ = (UINT8)(((UINT8)(Data >> 0x10)) & 0xff);
 }

 if (mDst < mDstUpperLimit) {
  *mDst++ = (UINT8)(((UINT8)(Data >> 0x18)) & 0xff);
  }
 }

 STATIC
 EFI_STATUS
 AllocateMemory ()
 /*++

 Routine Description:

  Allocate memory spaces for data structures used in compression process

 Arguments: (VOID)

 Returns:

   EFI_SUCCESS - Memory is allocated successfully
   EFI_OUT_OF_RESOURCES - Allocation fails

 --*/
 {
 UINT32 i;

 mText = malloc (WNDSIZ * 2 + MAXMATCH);
 for (i = 0; i < WNDSIZ * 2 + MAXMATCH; i ++) {
  mText[i] = 0;
 }
 mLevel = malloc ((WNDSIZ + UINT8_MAX + 1) * sizeof(*mLevel));
 mChildCount = malloc ((WNDSIZ + UINT8_MAX + 1) *
 sizeof(*mChildCount));
 mPosition = malloc ((WNDSIZ + UINT8_MAX + 1) * sizeof(*mPosition));
 mParent = malloc (WNDSIZ * 2 * sizeof(*mParent));
 mPrev = malloc (WNDSIZ * 2 * sizeof(*mPrev));
 mNext = malloc ((MAX_HASH_VAL + 1) * sizeof(*mNext));

 mBufSiz = 16 * 1024U;
 while ((mBuf = malloc(mBufSiz)) == NULL) {
  mBufSiz = (mBufSiz / 10U) * 9U;
  if (mBufSiz < 4 * 1024U) {
    return EFI_OUT_OF_RESOURCES;
  }
 }
 mBuf[0] = 0;
  return EFI_SUCCESS;
 }

 VOID
 FreeMemory ()
 /*++

 Routine Description:

  Called when compression is completed to free memory previously allocated.

 Arguments: (VOID)

 Returns: (VOID)

 --*/
 {
  if (mText) {
    free (mText);
  }

  if (mLevel) {
    free (mLevel);
  }

  if (mChildCount) {
    free (mChildCount);
  }

  if (mPosition) {
    free (mPosition);
  }

  if (mParent) {
    free (mParent);
  }

  if (mPrev) {
    free (mPrev);
  }

  if (mNext) {
    free (mNext);
  }

  if (mBuf) {
    free (mBuf);
  }

  return;
 }

 STATIC
 VOID

 InitSlide ()
 /*++

 Routine Description:

  Initialize String Info Log data structures

 Arguments: (VOID)

 Returns: (VOID)

 --*/
 {
  NODE i;

  for (i = WNDSIZ; i <= WNDSIZ + UINT8_MAX; i++) {
    mLevel[i] = 1;
    mPosition[i] = NIL; /* sentinel */
  }
 for (i = WNDSIZ; i < WNDSIZ * 2; i++) {
  mParent[i] = NIL;
 }
 mAvail = 1;
  for (i = 1; i < WNDSIZ - 1; i++) {
    mNext[i] = (NODE)(i + 1);
  }

 mNext[WNDSIZ - 1] = NIL;
  for (i = WNDSIZ * 2; i <= MAX_HASH_VAL; i++) {
    mNext[i] = NIL;
  }
 }

 STATIC
 NODE
 Child (
  IN NODE q,
  IN UINT8 c
  )
 /*++

 Routine Description:

  Find child node given the parent node and the edge character

Arguments:

  q - the parent node
  c - the edge character

 Returns:

  The child node (NIL if not found)

 --*/
 {
  NODE r;

   r = mNext[HASH(q, c)];
   mParent[NIL] = q; /* sentinel */
   while (mParent[r] != q) {
    r = mNext[r];
   }

  return r;
 }

 STATIC
 VOID
 MakeChild (
  IN NODE q,
  IN UINT8 c,
  IN NODE r
  )
 /*++

 Routine Description:

    Create a new child for a given parent node.

 Arguments:

  q - the parent node
  c - the edge character
  r - the child node

 Returns: (VOID)

 --*/
 {
  NODE h, t;

   h = (NODE)HASH(q, c);
   t = mNext[h];
   mNext[h] = r;
   mNext[r] = t;
   mPrev[t] = r;
   mPrev[r] = h;
   mParent[r] = q;
   mChildCount[q]++;
 }

 STATIC
 VOID
 Split (
  NODE Old
  )
 /*++

 Routine Description:

    Split a node.

 Arguments:

    Old - the node to split

 Returns: (VOID)

 --*/
 {
   NODE New, t;

   New = mAvail;
   mAvail = mNext[New];
   mChildCount[New] = 0;
   t = mPrev[Old];
   mPrev[New] = t;
   mNext[t] = New;
   t = mNext[Old];
   mNext[New] = t;
   mPrev[t] = New;
   mParent[New] = mParent[Old];
   mLevel[New] = (UINT8)mMatchLen;
   mPosition[New] = mPos;
   MakeChild(New, mText[mMatchPos + mMatchLen], Old);
   MakeChild(New, mText[mPos + mMatchLen], mPos);
 }

 STATIC
 VOID
 InsertNode ()
 /*++

 Routine Description:

  Insert string info for current position into the String Info Log

 Arguments: (VOID)

 Returns: (VOID)

 --*/
 {
   NODE q, r, j, t;
   UINT8 c, *t1, *t2;

  if (mMatchLen >= 4) {

   //
   // We have just got a long match, the target tree
   // can be located by MatchPos + 1. Traverse the tree
   // from bottom up to get to a proper starting point.
   // The usage of PERC_FLAG ensures proper node deletion
   // in DeleteNode() later.
   //

  mMatchLen--;
  r = (INT16)((mMatchPos + 1) \| WNDSIZ);
  while ((q = mParent[r]) == NIL) {
    r = mNext[r];
  }
   while (mLevel[q] >= mMatchLen) {
    r = q; q = mParent[q];
   }
   t = q;
   while (mPosition[t] < 0) {
     mPosition[t] = mPos;
     t = mParent[t];
   }
   if (t < WNDSIZ) {
    mPosition[t] = (NODE)(mPos \| PERC_FLAG);
   }
 } else {

   //
   // Locate the target tree
   //

   q = (INT16)(mText[mPos] + WNDSIZ);
   c = mText[mPos + 1];
   if ((r = Child(q, c)) == NIL) {
     MakeChild(q, c, mPos);
     mMatchLen = 1;
     return;
   }
   mMatchLen = 2;
 }

 //
 // Traverse down the tree to find a match.
 // Update Position value along the route.
 // Node split or creation is involved.
 //

 for ( ; ; ) {
  if (r >= WNDSIZ) {
     j = MAXMATCH;
     mMatchPos = r;
  } else {
  j = mLevel[r];
  mMatchPos = (NODE)(mPosition[r] & ~PERC_FLAG);
 }
 if (mMatchPos >= mPos) {
  mMatchPos -= WNDSIZ;
 }
 t1 = &mText[mPos + mMatchLen];
 t2 = &mText[mMatchPos + mMatchLen];
 while (mMatchLen < j) {
 if (*t1 != *t2) {
   Split(r);
   return;
  }
  mMatchLen++;
  t1++;
  t2++;
 }
 if (mMatchLen >= MAXMATCH) {
    break;
 }
 mPosition[r] = mPos;
 q = r;
 if ((r = Child(q, *t1)) == NIL) {
    MakeChild(q, *t1, mPos);
    return;
  }
   mMatchLen++;
  }
  t = mPrev[r];
  mPrev[mPos] = t;
  mNext[t] = mPos;
  t = mNext[r];
  mNext[mPos] = t;
  mPrev[t] = mPos;
  mParent[mPos] = q;
  mParent[r] = NIL;

  //
  // Special usage of 'next'
  //
  mNext[r] = mPos;

 }

STATIC
VOID
DeleteNode ()
/*++

Routine Description:

  Delete outdated string info. (The Usage of PERC_FLAG
  ensures a clean deletion)

Arguments: (VOID)

Returns: (VOID)

--*/
{
 NODE q, r, s, t, u;

 if (mParent[mPos] == NIL) {
  return;
}

r = mPrev[mPos];
s = mNext[mPos];
mNext[r] = s;
mPrev[s] = r;
r = mParent[mPos];
mParent[mPos] = NIL;
if (r >= WNDSIZ || --mChildCount[r] > 1) {
  return;
}
t = (NODE)(mPosition[r] & ~PERC_FLAG);
if (t >= mPos) {
  t -= WNDSIZ;
}
s = t;
q = mParent[r];
while ((u = mPosition[q]) & PERC_FLAG) {
 u &= ~PERC_FLAG;
 if (u >= mPos) {
  u -= WNDSIZ;
 }
 if (u > s) {
  s = u;
 }
 mPosition[q] = (INT16)(s \| WNDSIZ);
 q = mParent[q];
}
if (q < WNDSIZ) {
 if (u >= mPos) {
  u -= WNDSIZ;
 }
 if (u > s) {
  s = u;
  }
  mPosition[q] = (INT16)(s \| WNDSIZ \| PERC_FLAG);
 }
 s = Child(r, mText[t + mLevel[r]]);
 t = mPrev[s];
 u = mNext[s];
 mNext[t] = u;
 mPrev[u] = t;
 t = mPrev[r];
 mNext[t] = s;
 mPrev[s] = t;
 t = mNext[r];
 mPrev[t] = s;
 mNext[s] = t;
 mParent[s] = mParent[r];
 mParent[r] = NIL;
 mNext[r] = mAvail;
 mAvail = r;
}

STATIC
VOID
GetNextMatch ()
/*++

Routine Description:

  Advance the current position (read in new data if needed).
  Delete outdated string info. Find a match string for current position.

Arguments: (VOID)

Returns: (VOID)

--*/
{
  INT32 n;

  mRemainder--;
  if (++mPos == WNDSIZ * 2) {
    memmove(&mText[0], &mText[WNDSIZ], WNDSIZ + MAXMATCH);
    n = FreadCrc(&mText[WNDSIZ + MAXMATCH], WNDSIZ);
    mRemainder += n;
    mPos = WNDSIZ;
  }
  DeleteNode();
  InsertNode();
}

STATIC
EFI_STATUS
Encode ()
/*++

Routine Description:

  The main controlling routine for compression process.

Arguments: (VOID)

Returns:

  EFI_SUCCESS - The compression is successful
  EFI_OUT_0F_RESOURCES - Not enough memory for compression process

--*/
{
 EFI_STATUS Status;
 INT32 LastMatchLen;
 NODE LastMatchPos;

 Status = AllocateMemory();
 if (EFI_ERROR(Status)) {
  FreeMemory();
  return Status;
 }

InitSlide();

HufEncodeStart();

mRemainder = FreadCrc(&mText[WNDSIZ], WNDSIZ + MAXMATCH);

mMatchLen = 0;
mPos = WNDSIZ;
InsertNode();
if (mMatchLen > mRemainder) {
 mMatchLen = mRemainder;
}
while (mRemainder > 0) {
 LastMatchLen = mMatchLen;
 LastMatchPos = mMatchPos;
 GetNextMatch();
 if (mMatchLen > mRemainder) {
   mMatchLen = mRemainder;
 }

if (mMatchLen > LastMatchLen \|\| LastMatchLen < THRESHOLD) {

  //
  // Not enough benefits are gained by outputting a pointer,
  // so just output the original character
  //

  Output(mText[mPos - 1], 0);
}  else {

  //
  // Outputting a pointer is beneficial enough, do it.
  //

  Output(LastMatchLen + (UINT8_MAX + 1 - THRESHOLD),
     (mPos - LastMatchPos - 2) & (WNDSIZ - 1));
  while (--LastMatchLen > 0) {
    GetNextMatch();
  }
  if (mMatchLen > mRemainder) {
   mMatchLen = mRemainder;
  }
 }
}

 HufEncodeEnd();
 FreeMemory();
 return EFI_SUCCESS;
}

STATIC
VOID
CountTFreq ()
/*++

Routine Description:

  Count the frequencies for the Extra Set

Arguments: (VOID)

Returns: (VOID)

--*/
{
  INT32 i, k, n, Count;

  for (i = 0; i < NT; i++) {
   mTFreq[i] = 0;
  }
  n = NC;
  while (n > 0 && mCLen[n - 1] == 0) {
   n--;
  }
  i = 0;
  while (i < n) {
   k = mCLen[i++];
   if (k == 0) {
    Count = 1;
    while (i < n && mCLen[i] == 0) {
     i++;
     Count++;
    }
    if (Count <= 2) {
     mTFreq[0] = (UINT16)(mTFreq[0] + Count);
    } else if (Count <= 18) {
     mTFreq[1]++;
    } else if (Count == 19) {
     mTFreq[0]++;
     mTFreq[1]++;
    } else {
     mTFreq[2]++;
    }
   } else {
    mTFreq[k + 2]++;
   }
  }
}

STATIC
VOID
WritePTLen (
  IN INT32 n,
  IN INT32 nbit,
  IN INT32 Special
  )
/*++

Routine Description:

  Outputs the code length array for the Extra Set or the Position Set.

Arguments:

  n - the number of symbols
  nbit - the number of bits needed to represent 'n'
  Special - the special symbol that needs to be take care of

Returns: (VOID)

--*/
{
  INT32 i, k;

  while (n > 0 && mPTLen[n - 1] == 0) {
   n--;
  }
  PutBits(nbit, n);
  i = 0;
  while (i < n) {
   k = mPTLen[i++];
   if (k <= 6) {
    PutBits(3, k);
   } else {
    PutBits(k - 3, (1U << (k - 3)) - 2);
   }
   if (i == Special) {
    while (i < 6 && mPTLen[i] == 0) {
     i++;
    }
    PutBits(2, (i - 3) & 3);
   }
  }
}

STATIC
VOID
WriteCLen ()
/*++

Routine Description:

  Outputs the code length array for Char&Length Set

Arguments: (VOID)

Returns: (VOID)

--*/
{
 INT32 i, k, n, Count;

 n = NC;
 while (n > 0 && mCLen[n - 1] == 0) {
 n--;
}
PutBits(CBIT, n);
i = 0;
while (i < n) {
 k = mCLen[i++];
 if (k == 0) {
  Count = 1;
  while (i < n && mCLen[i] == 0) {
   i++;
   Count++;
  }
  if (Count <= 2) {
   for (k = 0; k < Count; k++) {
    PutBits(mPTLen[0], mPTCode[0]);
   }
  } else if (Count <= 18) {
    PutBits(mPTLen[1], mPTCode[1]);
    PutBits(4, Count - 3);
  } else if (Count == 19) {
    PutBits(mPTLen[0], mPTCode[0]);
    PutBits(mPTLen[1], mPTCode[1]);
    PutBits(4, 15);
  } else {
    PutBits(mPTLen[2], mPTCode[2]);
    PutBits(CBIT, Count - 20);
   }
  } else {
    PutBits(mPTLen[k + 2], mPTCode[k + 2]);
   }
  }
}

STATIC
VOID
EncodeC (
  IN INT32 c
  )
{
  PutBits(mCLen[c], mCCode[c]);
}

STATIC
VOID
EncodeP (
  IN UINT32 p
  )
{
  UINT32 c, q;

  c = 0;
  q = p;
  while (q) {
    q >>= 1;
    c++;
    }
    PutBits(mPTLen[c], mPTCode[c]);
    if (c > 1) {
     PutBits(c - 1, p & (0xFFFFU >> (17 - c)));
   }
}

STATIC
VOID
SendBlock ()
/*++


Routine Description:

  Huffman code the block and output it.

Argument: (VOID)

Returns: (VOID)

--*/
{
 UINT32 i, k, Flags, Root, Pos, Size;
 Flags = 0;

 Root = MakeTree(NC, mCFreq, mCLen, mCCode);
 Size = mCFreq[Root];
 PutBits(16, Size);
 if (Root >= NC) {
   CountTFreq();
   Root = MakeTree(NT, mTFreq, mPTLen, mPTCode);
   if (Root >= NT) {
    WritePTLen(NT, TBIT, 3);
   } else {
    PutBits(TBIT, 0);
    PutBits(TBIT, Root);
   }
   WriteCLen();
  } else {
   PutBits(TBIT, 0);
   PutBits(TBIT, 0);
   PutBits(CBIT, 0);
   PutBits(CBIT, Root);
  }
  Root = MakeTree(NP, mPFreq, mPTLen, mPTCode);
  if (Root >= NP) {
   WritePTLen(NP, PBIT, -1);
  } else {
    PutBits(PBIT, 0);
    PutBits(PBIT, Root);
  }
  Pos = 0;
  for (i = 0; i < Size; i++) {
   if (i % UINT8_BIT == 0) {
    Flags = mBuf[Pos++];
   } else {
    Flags <<= 1;
   }
   if (Flags & (1U << (UINT8_BIT - 1))) {
    EncodeC(mBuf[Pos++] + (1U << UINT8_BIT));
    k = mBuf[Pos++] << UINT8_BIT;
    k += mBuf[Pos++];
    EncodeP(k);
   } else {
    EncodeC(mBuf[Pos++]);
   }
  }
  for (i = 0; i < NC; i++) {
   mCFreq[i] = 0;
  }
   for (i = 0; i < NP; i++) {
    mPFreq[i] = 0;
  }
}

STATIC
VOID
Output (
  IN UINT32 c,
  IN UINT32 p
)
/*++

Routine Description:

  Outputs an Original Character or a Pointer

Arguments:

  c - The original character or the 'String Length' element of a Pointer
  p - The 'Position' field of a Pointer

Returns: (VOID)

--*/
{
  STATIC UINT32 CPos;

  if ((mOutputMask >>= 1) == 0) {
   mOutputMask = 1U << (UINT8_BIT - 1);
   if (mOutputPos >= mBufSiz - 3 * UINT8_BIT) {
    SendBlock();
    mOutputPos = 0;
   }
   CPos = mOutputPos++;
   mBuf[CPos] = 0;
  }
  mBuf[mOutputPos++] = (UINT8) c;
  mCFreq[c]++;
  if (c >= (1U << UINT8_BIT)) {
   mBuf[CPos] \|= mOutputMask;
   mBuf[mOutputPos++] = (UINT8)(p >> UINT8_BIT);
   mBuf[mOutputPos++] = (UINT8) p;
   c = 0;
   while (p) {
    p >>= 1;
    c++;
   }
  mPFreq[c]++;
 }
}

STATIC
VOID
HufEncodeStart ()
{
 INT32 i;

 for (i = 0; i < NC; i++) {
  mCFreq[i] = 0;
 }
 for (i = 0; i < NP; i++) {
  mPFreq[i] = 0;
 }
 mOutputPos = mOutputMask = 0;
 InitPutBits();
 return;
}

STATIC
VOID
HufEncodeEnd ()
{
  SendBlock();

  //
  // Flush remaining bits
  //
  PutBits(UINT8_BIT - 1, 0);

  return;
 }

STATIC
VOID
MakeCrcTable ()
{
  UINT32 i, j, r;

  for (i = 0; i <= UINT8_MAX; i++) {
   r = i;
    for (j = 0; j < UINT8_BIT; j++) {
     if (r & 1) {
     r = (r >> 1) ^ CRCPOLY;
    } else {
     r >>= 1;
    }
   }
   mCrcTable[i] = (UINT16)r;
  }
}

STATIC
VOID
PutBits (
  IN INT32 n,
  IN UINT32 x
)
/*++

Routine Description:

  Outputs rightmost n bits of x

Arguments:

  n - the rightmost n bits of the data is used
  x - the data

Returns: (VOID)

--*/
{
UINT8 Temp;

if (n < mBitCount) {
 mSubBitBuf \|= x << (mBitCount -= n);
} else {

 Temp = (UINT8)(mSubBitBuf \| (x >> (n -= mBitCount)));
 if (mDst < mDstUpperLimit) {
  *mDst++ = Temp;
 }
 mCompSize++;

 if (n < UINT8_BIT) {
  mSubBitBuf = x << (mBitCount = UINT8_BIT - n);
 } else {

   Temp = (UINT8)(x >> (n - UINT8_BIT));
   if (mDst < mDstUpperLimit) {
    *mDst++ = Temp;
   }
   mCompSize++;

   mSubBitBuf = x << (mBitCount = 2 * UINT8_BIT - n);
  }
 }
}

STATIC
INT32
FreadCrc (
 OUT UINT8 *p,
 IN INT32 n
 )
/*++

Routine Description:

  Read in source data

Arguments:

  p - the buffer to hold the data
  n - number of bytes to read

Returns:

 number of bytes actually read

--*/
{
 INT32 i;

 for (i = 0; mSrc < mSrcUpperLimit && i < n; i++) {
  *p++ = *mSrc++;
 }
 n = i;

 p -= n;
 mOrigSize += n;
 while (--i >= 0) {
  UPDATE_CRC(*p++);
 }
 return n;
}

STATIC
VOID
InitPutBits ()
{
 mBitCount = UINT8_BIT;
 mSubBitBuf = 0;
}

STATIC
VOID
CountLen (
 IN INT32 i
 )
/*++

Routine Description:

 Count the number of each code length for a Huffman tree.

Arguments:

 i - the top node

Returns: (VOID)

--*/
{
 STATIC INT32 Depth = 0;

 if (i < mN) {
  mLenCnt[(Depth < 16) ? Depth : 16]++;
 } else {
  Depth++;
  CountLen(mLeft [i]);
  CountLen(mRight[i]);
  Depth--;
 }
}

STATIC
VOID
MakeLen (
 IN INT32 Root
 )
/*++

Routine Description:

  Create code length array for a Huffman tree

Arguments:

  Root - the root of the tree

--*/
{
 INT32 i, k;
 UINT32 Cum;

 for (i = 0; i <= 16; i++) {
  mLenCnt[i] = 0;
 }
 CountLen(Root);

 //
 // Adjust the length count array so that
 // no code will be generated longer than the designated length
 //
 Cum = 0;
 for (i = 16; i > 0; i--) {
  Cum += mLenCnt[i] << (16 - i);
 }
 while (Cum != (1U << 16)) {
  mLenCnt[16]--;
  for (i = 15; i > 0; i--) {
   if (mLenCnt[i] != 0) {
    mLenCnt[i]--;
    mLenCnt[i+1] += 2;
    break;
   }
  }
  Cum--;
 }
 for (i = 16; i > 0; i--) {
  k = mLenCnt[i];
  while (--k >= 0) {
   mLen[*mSortPtr++] = (UINT8)i;
  }
 }
}

STATIC
VOID
DownHeap (
 IN INT32 i
 )
{
 INT32 j, k;

 //
 // priority queue: send i-th entry down heap
 //

 k = mHeap[i];
 while ((j = 2 * i) <= mHeapSize) {
  if (j < mHeapSize && mFreq[mHeap[j]] > mFreq[mHeap[j + 1]]) {
   j++;
  }
  if (mFreq[k] <= mFreq[mHeap[j]]) {
   break;
  }
  mHeap[i] = mHeap[j];
  i = j;
 }
 mHeap[i] = (INT16)k;
}

STATIC
VOID
MakeCode (
 IN INT32 n,
 IN UINT8 Len[],
 OUT UINT16 Code[]
 )
/*++

Routine Description:

 Assign code to each symbol based on the code length array

Arguments:

 n - number of symbols
 Len - the code length array
 Code - stores codes for each symbol

Returns: (VOID)

--*/
{
 INT32 i;
 UINT16 Start[18];

 Start[1] = 0;
 for (i = 1; i <= 16; i++) {
  Start[i + 1] = (UINT16)((Start[i] + mLenCnt[i]) << 1);
 }
 for (i = 0; i < n; i++) {
  Code[i] = Start[Len[i]]++;
 }
}

STATIC
INT32
MakeTree (
 IN INT32 NParm,
 IN UINT16 FreqParm[],
 OUT UINT8 LenParm[],
 OUT UINT16 CodeParm[]
 )
/*++

Routine Description:

 Generates Huffman codes given a frequency distribution of symbols

Arguments:

 NParm - number of symbols
 FreqParm - frequency of each symbol
 LenParm - code length for each symbol
 CodeParm - code for each symbol

Returns:

 Root of the Huffman tree.

--*/
{
 INT32 i, j, k, Avail;

 //
 // make tree, calculate len[], return root
 //

 mN = NParm;
 mFreq = FreqParm;
 mLen = LenParm;
 Avail = mN;
 mHeapSize = 0;
 mHeap[1] = 0;
 for (i = 0; i < mN; i++) {
  mLen[i] = 0;
  if (mFreq[i]) {
   mHeap[++mHeapSize] = (INT16)i;
  }
 }
 if (mHeapSize < 2) {
  CodeParm[mHeap[1]] = 0;
  return mHeap[1];
 }
 for (i = mHeapSize / 2; i >= 1; i--) {

  //
  // make priority queue
  //
  DownHeap(i);
 }
 mSortPtr = CodeParm;
 do {
  i = mHeap[1];
  if (i < mN) {
   *mSortPtr++ = (UINT16)i;
  }
 mHeap[1] = mHeap[mHeapSize--];
 DownHeap(1);
 j = mHeap[1];
 if (j < mN) {
  *mSortPtr++ = (UINT16)j;
 }
 k = Avail++;
 mFreq[k] = (UINT16)(mFreq[i] + mFreq[j]);
 mHeap[1] = (INT16)k;
 DownHeap(1);
 mLeft[k] = (UINT16)i;
 mRight[k] = (UINT16)j;
}  while (mHeapSize > 1);

mSortPtr = CodeParm;
MakeLen(k);
MakeCode(NParm, LenParm, CodeParm);

 //
 // return root
 //
 return k;
}