//------------------------------------------------------------------------------
// picojpeg.c v1.1 - Public domain, Rich Geldreich <richgel99@gmail.com>
// Nov. 27, 2010 - Initial release
// Feb. 9, 2013 - Added H1V2/H2V1 support, cleaned up macros, signed shift fixes
// Also integrated and tested changes from Chris Phoenix <cphoenix@gmail.com>.
//------------------------------------------------------------------------------
#include "picojpeg.h"
//------------------------------------------------------------------------------
// Set to 1 if right shifts on signed ints are always unsigned (logical) shifts
// When 1, arithmetic right shifts will be emulated by using a logical shift
// with special case code to ensure the sign bit is replicated.
#define PJPG_RIGHT_SHIFT_IS_ALWAYS_UNSIGNED 0

// Define PJPG_INLINE to "inline" if your C compiler supports explicit inlining
#define PJPG_INLINE
//------------------------------------------------------------------------------
typedef unsigned char uint8;
typedef unsigned short uint16;
typedef signed char int8;
typedef signed short int16;
//------------------------------------------------------------------------------
#if PJPG_RIGHT_SHIFT_IS_ALWAYS_UNSIGNED
static int16 replicateSignBit16(int8 n) {
  switch (n) {
    case 0:
      return 0x0000;
    case 1:
      return 0x8000;
    case 2:
      return 0xC000;
    case 3:
      return 0xE000;
    case 4:
      return 0xF000;
    case 5:
      return 0xF800;
    case 6:
      return 0xFC00;
    case 7:
      return 0xFE00;
    case 8:
      return 0xFF00;
    case 9:
      return 0xFF80;
    case 10:
      return 0xFFC0;
    case 11:
      return 0xFFE0;
    case 12:
      return 0xFFF0;
    case 13:
      return 0xFFF8;
    case 14:
      return 0xFFFC;
    case 15:
      return 0xFFFE;
    default:
      return 0xFFFF;
  }
}
static PJPG_INLINE int16 arithmeticRightShiftN16(int16 x, int8 n) {
  int16 r = (uint16)x >> (uint8)n;
  if (x < 0) r |= replicateSignBit16(n);
  return r;
}
static PJPG_INLINE long arithmeticRightShift8L(long x) {
  long r = (unsigned long)x >> 8U;
  if (x < 0) r |= ~(~(unsigned long)0U >> 8U);
  return r;
}
#define PJPG_ARITH_SHIFT_RIGHT_N_16(x, n) arithmeticRightShiftN16(x, n)
#define PJPG_ARITH_SHIFT_RIGHT_8_L(x) arithmeticRightShift8L(x)
#else
#define PJPG_ARITH_SHIFT_RIGHT_N_16(x, n) ((x) >> (n))
#define PJPG_ARITH_SHIFT_RIGHT_8_L(x) ((x) >> 8)
#endif
//------------------------------------------------------------------------------
// Change as needed - the PJPG_MAX_WIDTH/PJPG_MAX_HEIGHT checks are only present
// to quickly detect bogus files.
#define PJPG_MAX_WIDTH 16384
#define PJPG_MAX_HEIGHT 16384
#define PJPG_MAXCOMPSINSCAN 3
//------------------------------------------------------------------------------
typedef enum {
  M_SOF0 = 0xC0,
  M_SOF1 = 0xC1,
  M_SOF2 = 0xC2,
  M_SOF3 = 0xC3,

  M_SOF5 = 0xC5,
  M_SOF6 = 0xC6,
  M_SOF7 = 0xC7,

  M_JPG = 0xC8,
  M_SOF9 = 0xC9,
  M_SOF10 = 0xCA,
  M_SOF11 = 0xCB,

  M_SOF13 = 0xCD,
  M_SOF14 = 0xCE,
  M_SOF15 = 0xCF,

  M_DHT = 0xC4,

  M_DAC = 0xCC,

  M_RST0 = 0xD0,
  M_RST1 = 0xD1,
  M_RST2 = 0xD2,
  M_RST3 = 0xD3,
  M_RST4 = 0xD4,
  M_RST5 = 0xD5,
  M_RST6 = 0xD6,
  M_RST7 = 0xD7,

  M_SOI = 0xD8,
  M_EOI = 0xD9,
  M_SOS = 0xDA,
  M_DQT = 0xDB,
  M_DNL = 0xDC,
  M_DRI = 0xDD,
  M_DHP = 0xDE,
  M_EXP = 0xDF,

  M_APP0 = 0xE0,
  M_APP15 = 0xEF,

  M_JPG0 = 0xF0,
  M_JPG13 = 0xFD,
  M_COM = 0xFE,

  M_TEM = 0x01,

  M_ERROR = 0x100,

  RST0 = 0xD0
} JPEG_MARKER;
//------------------------------------------------------------------------------
static const int8 ZAG[] = {
    0,  1,  8,  16, 9,  2,  3,  10, 17, 24, 32, 25, 18, 11, 4,  5,  12, 19, 26, 33, 40, 48,
    41, 34, 27, 20, 13, 6,  7,  14, 21, 28, 35, 42, 49, 56, 57, 50, 43, 36, 29, 22, 15, 23,
    30, 37, 44, 51, 58, 59, 52, 45, 38, 31, 39, 46, 53, 60, 61, 54, 47, 55, 62, 63,
};
//------------------------------------------------------------------------------
// 128 bytes
static int16 gCoeffBuf[8 * 8];

// 8*8*4 bytes * 3 = 768
static uint8 gMCUBufR[256];
static uint8 gMCUBufG[256];
static uint8 gMCUBufB[256];

// 256 bytes
static int16 gQuant0[8 * 8];
static int16 gQuant1[8 * 8];

// 6 bytes
static int16 gLastDC[3];

typedef struct HuffTableT {
  uint16 mMinCode[16];
  uint16 mMaxCode[16];
  uint8 mValPtr[16];
} HuffTable;

// DC - 192
static HuffTable gHuffTab0;

static uint8 gHuffVal0[16];

static HuffTable gHuffTab1;
static uint8 gHuffVal1[16];

// AC - 672
static HuffTable gHuffTab2;
static uint8 gHuffVal2[256];

static HuffTable gHuffTab3;
static uint8 gHuffVal3[256];

static uint8 gValidHuffTables;
static uint8 gValidQuantTables;

static uint8 gTemFlag;
#define PJPG_MAX_IN_BUF_SIZE 256
static uint8 gInBuf[PJPG_MAX_IN_BUF_SIZE];
static uint8 gInBufOfs;
static uint8 gInBufLeft;

static uint16 gBitBuf;
static uint8 gBitsLeft;
//------------------------------------------------------------------------------
static uint16 gImageXSize;
static uint16 gImageYSize;
static uint8 gCompsInFrame;
static uint8 gCompIdent[3];
static uint8 gCompHSamp[3];
static uint8 gCompVSamp[3];
static uint8 gCompQuant[3];

static uint16 gRestartInterval;
static uint16 gNextRestartNum;
static uint16 gRestartsLeft;

static uint8 gCompsInScan;
static uint8 gCompList[3];
static uint8 gCompDCTab[3];  // 0,1
static uint8 gCompACTab[3];  // 0,1

static pjpeg_scan_type_t gScanType;

static uint8 gMaxBlocksPerMCU;
static uint8 gMaxMCUXSize;
static uint8 gMaxMCUYSize;
static uint16 gMaxMCUSPerRow;
static uint16 gMaxMCUSPerCol;

static uint16 gNumMCUSRemainingX, gNumMCUSRemainingY;

static uint8 gMCUOrg[6];

static pjpeg_need_bytes_callback_t g_pNeedBytesCallback;
static void* g_pCallback_data;
static uint8 gCallbackStatus;
static uint8 gReduce;
//------------------------------------------------------------------------------
static void fillInBuf(void) {
  unsigned char status;

  // Reserve a few bytes at the beginning of the buffer for putting back ("stuffing") chars.
  gInBufOfs = 4;
  gInBufLeft = 0;

  status = (*g_pNeedBytesCallback)(gInBuf + gInBufOfs, PJPG_MAX_IN_BUF_SIZE - gInBufOfs, &gInBufLeft, g_pCallback_data);
  if (status) {
    // The user provided need bytes callback has indicated an error, so record the error and continue trying to decode.
    // The highest level pjpeg entrypoints will catch the error and return the non-zero status.
    gCallbackStatus = status;
  }
}
//------------------------------------------------------------------------------
static PJPG_INLINE uint8 getChar(void) {
  if (!gInBufLeft) {
    fillInBuf();
    if (!gInBufLeft) {
      gTemFlag = ~gTemFlag;
      return gTemFlag ? 0xFF : 0xD9;
    }
  }

  gInBufLeft--;
  return gInBuf[gInBufOfs++];
}
//------------------------------------------------------------------------------
static PJPG_INLINE void stuffChar(uint8 i) {
  gInBufOfs--;
  gInBuf[gInBufOfs] = i;
  gInBufLeft++;
}
//------------------------------------------------------------------------------
static PJPG_INLINE uint8 getOctet(uint8 FFCheck) {
  uint8 c = getChar();

  if ((FFCheck) && (c == 0xFF)) {
    uint8 n = getChar();

    if (n) {
      stuffChar(n);
      stuffChar(0xFF);
    }
  }

  return c;
}
//------------------------------------------------------------------------------
static uint16 getBits(uint8 numBits, uint8 FFCheck) {
  uint8 origBits = numBits;
  uint16 ret = gBitBuf;

  if (numBits > 8) {
    numBits -= 8;

    gBitBuf <<= gBitsLeft;

    gBitBuf |= getOctet(FFCheck);

    gBitBuf <<= (8 - gBitsLeft);

    ret = (ret & 0xFF00) | (gBitBuf >> 8);
  }

  if (gBitsLeft < numBits) {
    gBitBuf <<= gBitsLeft;

    gBitBuf |= getOctet(FFCheck);

    gBitBuf <<= (numBits - gBitsLeft);

    gBitsLeft = 8 - (numBits - gBitsLeft);
  } else {
    gBitsLeft = (uint8)(gBitsLeft - numBits);
    gBitBuf <<= numBits;
  }

  return ret >> (16 - origBits);
}
//------------------------------------------------------------------------------
static PJPG_INLINE uint16 getBits1(uint8 numBits) { return getBits(numBits, 0); }
//------------------------------------------------------------------------------
static PJPG_INLINE uint16 getBits2(uint8 numBits) { return getBits(numBits, 1); }
//------------------------------------------------------------------------------
static PJPG_INLINE uint8 getBit(void) {
  uint8 ret = 0;
  if (gBitBuf & 0x8000) ret = 1;

  if (!gBitsLeft) {
    gBitBuf |= getOctet(1);

    gBitsLeft += 8;
  }

  gBitsLeft--;
  gBitBuf <<= 1;

  return ret;
}
//------------------------------------------------------------------------------
static uint16 getExtendTest(uint8 i) {
  switch (i) {
    case 0:
      return 0;
    case 1:
      return 0x0001;
    case 2:
      return 0x0002;
    case 3:
      return 0x0004;
    case 4:
      return 0x0008;
    case 5:
      return 0x0010;
    case 6:
      return 0x0020;
    case 7:
      return 0x0040;
    case 8:
      return 0x0080;
    case 9:
      return 0x0100;
    case 10:
      return 0x0200;
    case 11:
      return 0x0400;
    case 12:
      return 0x0800;
    case 13:
      return 0x1000;
    case 14:
      return 0x2000;
    case 15:
      return 0x4000;
    default:
      return 0;
  }
}
//------------------------------------------------------------------------------
static int16 getExtendOffset(uint8 i) {
  switch (i) {
    case 0:
      return 0;
    case 1:
      return ((-1) << 1) + 1;
    case 2:
      return ((-1) << 2) + 1;
    case 3:
      return ((-1) << 3) + 1;
    case 4:
      return ((-1) << 4) + 1;
    case 5:
      return ((-1) << 5) + 1;
    case 6:
      return ((-1) << 6) + 1;
    case 7:
      return ((-1) << 7) + 1;
    case 8:
      return ((-1) << 8) + 1;
    case 9:
      return ((-1) << 9) + 1;
    case 10:
      return ((-1) << 10) + 1;
    case 11:
      return ((-1) << 11) + 1;
    case 12:
      return ((-1) << 12) + 1;
    case 13:
      return ((-1) << 13) + 1;
    case 14:
      return ((-1) << 14) + 1;
    case 15:
      return ((-1) << 15) + 1;
    default:
      return 0;
  }
};
//------------------------------------------------------------------------------
static PJPG_INLINE int16 huffExtend(uint16 x, uint8 s) {
  return ((x < getExtendTest(s)) ? ((int16)x + getExtendOffset(s)) : (int16)x);
}
//------------------------------------------------------------------------------
static PJPG_INLINE uint8 huffDecode(const HuffTable* pHuffTable, const uint8* pHuffVal) {
  uint8 i = 0;
  uint8 j;
  uint16 code = getBit();

  // This func only reads a bit at a time, which on modern CPU's is not terribly efficient.
  // But on microcontrollers without strong integer shifting support this seems like a
  // more reasonable approach.
  for (;;) {
    uint16 maxCode;

    if (i == 16) return 0;

    maxCode = pHuffTable->mMaxCode[i];
    if ((code <= maxCode) && (maxCode != 0xFFFF)) break;

    i++;
    code <<= 1;
    code |= getBit();
  }

  j = pHuffTable->mValPtr[i];
  j = (uint8)(j + (code - pHuffTable->mMinCode[i]));

  return pHuffVal[j];
}
//------------------------------------------------------------------------------
static void huffCreate(const uint8* pBits, HuffTable* pHuffTable) {
  uint8 i = 0;
  uint8 j = 0;

  uint16 code = 0;

  for (;;) {
    uint8 num = pBits[i];

    if (!num) {
      pHuffTable->mMinCode[i] = 0x0000;
      pHuffTable->mMaxCode[i] = 0xFFFF;
      pHuffTable->mValPtr[i] = 0;
    } else {
      pHuffTable->mMinCode[i] = code;
      pHuffTable->mMaxCode[i] = code + num - 1;
      pHuffTable->mValPtr[i] = j;

      j = (uint8)(j + num);

      code = (uint16)(code + num);
    }

    code <<= 1;

    i++;
    if (i > 15) break;
  }
}
//------------------------------------------------------------------------------
static HuffTable* getHuffTable(uint8 index) {
  // 0-1 = DC
  // 2-3 = AC
  switch (index) {
    case 0:
      return &gHuffTab0;
    case 1:
      return &gHuffTab1;
    case 2:
      return &gHuffTab2;
    case 3:
      return &gHuffTab3;
    default:
      return 0;
  }
}
//------------------------------------------------------------------------------
static uint8* getHuffVal(uint8 index) {
  // 0-1 = DC
  // 2-3 = AC
  switch (index) {
    case 0:
      return gHuffVal0;
    case 1:
      return gHuffVal1;
    case 2:
      return gHuffVal2;
    case 3:
      return gHuffVal3;
    default:
      return 0;
  }
}
//------------------------------------------------------------------------------
static uint16 getMaxHuffCodes(uint8 index) { return (index < 2) ? 12 : 255; }
//------------------------------------------------------------------------------
static uint8 readDHTMarker(void) {
  uint8 bits[16];
  uint16 left = getBits1(16);

  if (left < 2) return PJPG_BAD_DHT_MARKER;

  left -= 2;

  while (left) {
    uint8 i, tableIndex, index;
    uint8* pHuffVal;
    HuffTable* pHuffTable;
    uint16 count, totalRead;

    index = (uint8)getBits1(8);

    if (((index & 0xF) > 1) || ((index & 0xF0) > 0x10)) return PJPG_BAD_DHT_INDEX;

    tableIndex = ((index >> 3) & 2) + (index & 1);

    pHuffTable = getHuffTable(tableIndex);
    pHuffVal = getHuffVal(tableIndex);

    gValidHuffTables |= (1 << tableIndex);

    count = 0;
    for (i = 0; i <= 15; i++) {
      uint8 n = (uint8)getBits1(8);
      bits[i] = n;
      count = (uint16)(count + n);
    }

    if (count > getMaxHuffCodes(tableIndex)) return PJPG_BAD_DHT_COUNTS;

    for (i = 0; i < count; i++) pHuffVal[i] = (uint8)getBits1(8);

    totalRead = 1 + 16 + count;

    if (left < totalRead) return PJPG_BAD_DHT_MARKER;

    left = (uint16)(left - totalRead);

    huffCreate(bits, pHuffTable);
  }

  return 0;
}
//------------------------------------------------------------------------------
static void createWinogradQuant(int16* pQuant);

static uint8 readDQTMarker(void) {
  uint16 left = getBits1(16);

  if (left < 2) return PJPG_BAD_DQT_MARKER;

  left -= 2;

  while (left) {
    uint8 i;
    uint8 n = (uint8)getBits1(8);
    uint8 prec = n >> 4;
    uint16 totalRead;

    n &= 0x0F;

    if (n > 1) return PJPG_BAD_DQT_TABLE;

    gValidQuantTables |= (n ? 2 : 1);

    // read quantization entries, in zag order
    for (i = 0; i < 64; i++) {
      uint16 temp = getBits1(8);

      if (prec) temp = (temp << 8) + getBits1(8);

      if (n)
        gQuant1[i] = (int16)temp;
      else
        gQuant0[i] = (int16)temp;
    }

    createWinogradQuant(n ? gQuant1 : gQuant0);

    totalRead = 64 + 1;

    if (prec) totalRead += 64;

    if (left < totalRead) return PJPG_BAD_DQT_LENGTH;

    left = (uint16)(left - totalRead);
  }

  return 0;
}
//------------------------------------------------------------------------------
static uint8 readSOFMarker(void) {
  uint8 i;
  uint16 left = getBits1(16);

  if (getBits1(8) != 8) return PJPG_BAD_PRECISION;

  gImageYSize = getBits1(16);

  if ((!gImageYSize) || (gImageYSize > PJPG_MAX_HEIGHT)) return PJPG_BAD_HEIGHT;

  gImageXSize = getBits1(16);

  if ((!gImageXSize) || (gImageXSize > PJPG_MAX_WIDTH)) return PJPG_BAD_WIDTH;

  gCompsInFrame = (uint8)getBits1(8);

  if (gCompsInFrame > 3) return PJPG_TOO_MANY_COMPONENTS;

  if (left != (gCompsInFrame + gCompsInFrame + gCompsInFrame + 8)) return PJPG_BAD_SOF_LENGTH;

  for (i = 0; i < gCompsInFrame; i++) {
    gCompIdent[i] = (uint8)getBits1(8);
    gCompHSamp[i] = (uint8)getBits1(4);
    gCompVSamp[i] = (uint8)getBits1(4);
    gCompQuant[i] = (uint8)getBits1(8);

    if (gCompQuant[i] > 1) return PJPG_UNSUPPORTED_QUANT_TABLE;
  }

  return 0;
}
//------------------------------------------------------------------------------
// Used to skip unrecognized markers.
static uint8 skipVariableMarker(void) {
  uint16 left = getBits1(16);

  if (left < 2) return PJPG_BAD_VARIABLE_MARKER;

  left -= 2;

  while (left) {
    getBits1(8);
    left--;
  }

  return 0;
}
//------------------------------------------------------------------------------
// Read a define restart interval (DRI) marker.
static uint8 readDRIMarker(void) {
  if (getBits1(16) != 4) return PJPG_BAD_DRI_LENGTH;

  gRestartInterval = getBits1(16);

  return 0;
}
//------------------------------------------------------------------------------
// Read a start of scan (SOS) marker.
static uint8 readSOSMarker(void) {
  uint8 i;
  uint16 left = getBits1(16);
  uint8 spectral_start, spectral_end, successive_high, successive_low;

  gCompsInScan = (uint8)getBits1(8);

  left -= 3;

  if ((left != (gCompsInScan + gCompsInScan + 3)) || (gCompsInScan < 1) || (gCompsInScan > PJPG_MAXCOMPSINSCAN))
    return PJPG_BAD_SOS_LENGTH;

  for (i = 0; i < gCompsInScan; i++) {
    uint8 cc = (uint8)getBits1(8);
    uint8 c = (uint8)getBits1(8);
    uint8 ci;

    left -= 2;

    for (ci = 0; ci < gCompsInFrame; ci++)
      if (cc == gCompIdent[ci]) break;

    if (ci >= gCompsInFrame) return PJPG_BAD_SOS_COMP_ID;

    gCompList[i] = ci;
    gCompDCTab[ci] = (c >> 4) & 15;
    gCompACTab[ci] = (c & 15);
  }

  spectral_start = (uint8)getBits1(8);
  spectral_end = (uint8)getBits1(8);
  successive_high = (uint8)getBits1(4);
  successive_low = (uint8)getBits1(4);

  left -= 3;

  while (left) {
    getBits1(8);
    left--;
  }

  return 0;
}
//------------------------------------------------------------------------------
static uint8 nextMarker(void) {
  uint8 c;
  uint8 bytes = 0;

  do {
    do {
      bytes++;

      c = (uint8)getBits1(8);

    } while (c != 0xFF);

    do {
      c = (uint8)getBits1(8);

    } while (c == 0xFF);

  } while (c == 0);

  // If bytes > 0 here, there where extra bytes before the marker (not good).

  return c;
}
//------------------------------------------------------------------------------
// Process markers. Returns when an SOFx, SOI, EOI, or SOS marker is
// encountered.
static uint8 processMarkers(uint8* pMarker) {
  for (;;) {
    uint8 c = nextMarker();

    switch (c) {
      case M_SOF0:
      case M_SOF1:
      case M_SOF2:
      case M_SOF3:
      case M_SOF5:
      case M_SOF6:
      case M_SOF7:
      //      case M_JPG:
      case M_SOF9:
      case M_SOF10:
      case M_SOF11:
      case M_SOF13:
      case M_SOF14:
      case M_SOF15:
      case M_SOI:
      case M_EOI:
      case M_SOS: {
        *pMarker = c;
        return 0;
      }
      case M_DHT: {
        readDHTMarker();
        break;
      }
      // Sorry, no arithmetic support at this time. Dumb patents!
      case M_DAC: {
        return PJPG_NO_ARITHMITIC_SUPPORT;
      }
      case M_DQT: {
        readDQTMarker();
        break;
      }
      case M_DRI: {
        readDRIMarker();
        break;
      }
        // case M_APP0:  /* no need to read the JFIF marker */

      case M_JPG:
      case M_RST0: /* no parameters */
      case M_RST1:
      case M_RST2:
      case M_RST3:
      case M_RST4:
      case M_RST5:
      case M_RST6:
      case M_RST7:
      case M_TEM: {
        return PJPG_UNEXPECTED_MARKER;
      }
      default: /* must be DNL, DHP, EXP, APPn, JPGn, COM, or RESn or APP0 */
      {
        skipVariableMarker();
        break;
      }
    }
  }
  //   return 0;
}
//------------------------------------------------------------------------------
// Finds the start of image (SOI) marker.
static uint8 locateSOIMarker(void) {
  uint16 bytesleft;

  uint8 lastchar = (uint8)getBits1(8);

  uint8 thischar = (uint8)getBits1(8);

  /* ok if it's a normal JPEG file without a special header */

  if ((lastchar == 0xFF) && (thischar == M_SOI)) return 0;

  bytesleft = 4096;  // 512;

  for (;;) {
    if (--bytesleft == 0) return PJPG_NOT_JPEG;

    lastchar = thischar;

    thischar = (uint8)getBits1(8);

    if (lastchar == 0xFF) {
      if (thischar == M_SOI)
        break;
      else if (thischar == M_EOI)  // getBits1 will keep returning M_EOI if we read past the end
        return PJPG_NOT_JPEG;
    }
  }

  /* Check the next character after marker: if it's not 0xFF, it can't
  be the start of the next marker, so the file is bad */

  thischar = (uint8)((gBitBuf >> 8) & 0xFF);

  if (thischar != 0xFF) return PJPG_NOT_JPEG;

  return 0;
}
//------------------------------------------------------------------------------
// Find a start of frame (SOF) marker.
static uint8 locateSOFMarker(void) {
  uint8 c;

  uint8 status = locateSOIMarker();
  if (status) return status;

  status = processMarkers(&c);
  if (status) return status;

  switch (c) {
    case M_SOF2: {
      // Progressive JPEG - not supported by picojpeg (would require too
      // much memory, or too many IDCT's for embedded systems).
      return PJPG_UNSUPPORTED_MODE;
    }
    case M_SOF0: /* baseline DCT */
    {
      status = readSOFMarker();
      if (status) return status;

      break;
    }
    case M_SOF9: {
      return PJPG_NO_ARITHMITIC_SUPPORT;
    }
    case M_SOF1: /* extended sequential DCT */
    default: {
      return PJPG_UNSUPPORTED_MARKER;
    }
  }

  return 0;
}
//------------------------------------------------------------------------------
// Find a start of scan (SOS) marker.
static uint8 locateSOSMarker(uint8* pFoundEOI) {
  uint8 c;
  uint8 status;

  *pFoundEOI = 0;

  status = processMarkers(&c);
  if (status) return status;

  if (c == M_EOI) {
    *pFoundEOI = 1;
    return 0;
  } else if (c != M_SOS)
    return PJPG_UNEXPECTED_MARKER;

  return readSOSMarker();
}
//------------------------------------------------------------------------------
static uint8 init(void) {
  gImageXSize = 0;
  gImageYSize = 0;
  gCompsInFrame = 0;
  gRestartInterval = 0;
  gCompsInScan = 0;
  gValidHuffTables = 0;
  gValidQuantTables = 0;
  gTemFlag = 0;
  gInBufOfs = 0;
  gInBufLeft = 0;
  gBitBuf = 0;
  gBitsLeft = 8;

  getBits1(8);
  getBits1(8);

  return 0;
}
//------------------------------------------------------------------------------
// This method throws back into the stream any bytes that where read
// into the bit buffer during initial marker scanning.
static void fixInBuffer(void) {
  /* In case any 0xFF's where pulled into the buffer during marker scanning */

  if (gBitsLeft > 0) stuffChar((uint8)gBitBuf);

  stuffChar((uint8)(gBitBuf >> 8));

  gBitsLeft = 8;
  getBits2(8);
  getBits2(8);
}
//------------------------------------------------------------------------------
// Restart interval processing.
static uint8 processRestart(void) {
  // Let's scan a little bit to find the marker, but not _too_ far.
  // 1536 is a "fudge factor" that determines how much to scan.
  uint16 i;
  uint8 c = 0;

  for (i = 1536; i > 0; i--)
    if (getChar() == 0xFF) break;

  if (i == 0) return PJPG_BAD_RESTART_MARKER;

  for (; i > 0; i--)
    if ((c = getChar()) != 0xFF) break;

  if (i == 0) return PJPG_BAD_RESTART_MARKER;

  // Is it the expected marker? If not, something bad happened.
  if (c != (gNextRestartNum + M_RST0)) return PJPG_BAD_RESTART_MARKER;

  // Reset each component's DC prediction values.
  gLastDC[0] = 0;
  gLastDC[1] = 0;
  gLastDC[2] = 0;

  gRestartsLeft = gRestartInterval;

  gNextRestartNum = (gNextRestartNum + 1) & 7;

  // Get the bit buffer going again

  gBitsLeft = 8;
  getBits2(8);
  getBits2(8);

  return 0;
}
//------------------------------------------------------------------------------
// FIXME: findEOI() is not actually called at the end of the image
// (it's optional, and probably not needed on embedded devices)
static uint8 findEOI(void) {
  uint8 c;
  uint8 status;

  // Prime the bit buffer
  gBitsLeft = 8;
  getBits1(8);
  getBits1(8);

  // The next marker _should_ be EOI
  status = processMarkers(&c);
  if (status)
    return status;
  else if (gCallbackStatus)
    return gCallbackStatus;

  // gTotalBytesRead -= in_buf_left;
  if (c != M_EOI) return PJPG_UNEXPECTED_MARKER;

  return 0;
}
//------------------------------------------------------------------------------
static uint8 checkHuffTables(void) {
  uint8 i;

  for (i = 0; i < gCompsInScan; i++) {
    uint8 compDCTab = gCompDCTab[gCompList[i]];
    uint8 compACTab = gCompACTab[gCompList[i]] + 2;

    if (((gValidHuffTables & (1 << compDCTab)) == 0) || ((gValidHuffTables & (1 << compACTab)) == 0))
      return PJPG_UNDEFINED_HUFF_TABLE;
  }

  return 0;
}
//------------------------------------------------------------------------------
static uint8 checkQuantTables(void) {
  uint8 i;

  for (i = 0; i < gCompsInScan; i++) {
    uint8 compQuantMask = gCompQuant[gCompList[i]] ? 2 : 1;

    if ((gValidQuantTables & compQuantMask) == 0) return PJPG_UNDEFINED_QUANT_TABLE;
  }

  return 0;
}
//------------------------------------------------------------------------------
static uint8 initScan(void) {
  uint8 foundEOI;
  uint8 status = locateSOSMarker(&foundEOI);
  if (status) return status;
  if (foundEOI) return PJPG_UNEXPECTED_MARKER;

  status = checkHuffTables();
  if (status) return status;

  status = checkQuantTables();
  if (status) return status;

  gLastDC[0] = 0;
  gLastDC[1] = 0;
  gLastDC[2] = 0;

  if (gRestartInterval) {
    gRestartsLeft = gRestartInterval;
    gNextRestartNum = 0;
  }

  fixInBuffer();

  return 0;
}
//------------------------------------------------------------------------------
static uint8 initFrame(void) {
  if (gCompsInFrame == 1) {
    if ((gCompHSamp[0] != 1) || (gCompVSamp[0] != 1)) return PJPG_UNSUPPORTED_SAMP_FACTORS;

    gScanType = PJPG_GRAYSCALE;

    gMaxBlocksPerMCU = 1;
    gMCUOrg[0] = 0;

    gMaxMCUXSize = 8;
    gMaxMCUYSize = 8;
  } else if (gCompsInFrame == 3) {
    if (((gCompHSamp[1] != 1) || (gCompVSamp[1] != 1)) || ((gCompHSamp[2] != 1) || (gCompVSamp[2] != 1)))
      return PJPG_UNSUPPORTED_SAMP_FACTORS;

    if ((gCompHSamp[0] == 1) && (gCompVSamp[0] == 1)) {
      gScanType = PJPG_YH1V1;

      gMaxBlocksPerMCU = 3;
      gMCUOrg[0] = 0;
      gMCUOrg[1] = 1;
      gMCUOrg[2] = 2;

      gMaxMCUXSize = 8;
      gMaxMCUYSize = 8;
    } else if ((gCompHSamp[0] == 1) && (gCompVSamp[0] == 2)) {
      gScanType = PJPG_YH1V2;

      gMaxBlocksPerMCU = 4;
      gMCUOrg[0] = 0;
      gMCUOrg[1] = 0;
      gMCUOrg[2] = 1;
      gMCUOrg[3] = 2;

      gMaxMCUXSize = 8;
      gMaxMCUYSize = 16;
    } else if ((gCompHSamp[0] == 2) && (gCompVSamp[0] == 1)) {
      gScanType = PJPG_YH2V1;

      gMaxBlocksPerMCU = 4;
      gMCUOrg[0] = 0;
      gMCUOrg[1] = 0;
      gMCUOrg[2] = 1;
      gMCUOrg[3] = 2;

      gMaxMCUXSize = 16;
      gMaxMCUYSize = 8;
    } else if ((gCompHSamp[0] == 2) && (gCompVSamp[0] == 2)) {
      gScanType = PJPG_YH2V2;

      gMaxBlocksPerMCU = 6;
      gMCUOrg[0] = 0;
      gMCUOrg[1] = 0;
      gMCUOrg[2] = 0;
      gMCUOrg[3] = 0;
      gMCUOrg[4] = 1;
      gMCUOrg[5] = 2;

      gMaxMCUXSize = 16;
      gMaxMCUYSize = 16;
    } else
      return PJPG_UNSUPPORTED_SAMP_FACTORS;
  } else
    return PJPG_UNSUPPORTED_COLORSPACE;

  gMaxMCUSPerRow = (gImageXSize + (gMaxMCUXSize - 1)) >> ((gMaxMCUXSize == 8) ? 3 : 4);
  gMaxMCUSPerCol = (gImageYSize + (gMaxMCUYSize - 1)) >> ((gMaxMCUYSize == 8) ? 3 : 4);

  // This can overflow on large JPEG's.
  // gNumMCUSRemaining = gMaxMCUSPerRow * gMaxMCUSPerCol;
  gNumMCUSRemainingX = gMaxMCUSPerRow;
  gNumMCUSRemainingY = gMaxMCUSPerCol;

  return 0;
}
//----------------------------------------------------------------------------
// Winograd IDCT: 5 multiplies per row/col, up to 80 muls for the 2D IDCT

#define PJPG_DCT_SCALE_BITS 7

#define PJPG_DCT_SCALE (1U << PJPG_DCT_SCALE_BITS)

#define PJPG_DESCALE(x) PJPG_ARITH_SHIFT_RIGHT_N_16(((x) + (1 << (PJPG_DCT_SCALE_BITS - 1))), PJPG_DCT_SCALE_BITS)

#define PJPG_WFIX(x) ((x) * PJPG_DCT_SCALE + 0.5f)

#define PJPG_WINOGRAD_QUANT_SCALE_BITS 10

const uint8 gWinogradQuant[] = {
    128, 178, 178, 167, 246, 167, 151, 232, 232, 151, 128, 209, 219, 209, 128, 101, 178, 197, 197, 178, 101, 69,
    139, 167, 177, 167, 139, 69,  35,  96,  131, 151, 151, 131, 96,  35,  49,  91,  118, 128, 118, 91,  49,  46,
    81,  101, 101, 81,  46,  42,  69,  79,  69,  42,  35,  54,  54,  35,  28,  37,  28,  19,  19,  10,
};

// Multiply quantization matrix by the Winograd IDCT scale factors
static void createWinogradQuant(int16* pQuant) {
  uint8 i;

  for (i = 0; i < 64; i++) {
    long x = pQuant[i];
    x *= gWinogradQuant[i];
    pQuant[i] = (int16)((x + (1 << (PJPG_WINOGRAD_QUANT_SCALE_BITS - PJPG_DCT_SCALE_BITS - 1))) >>
                        (PJPG_WINOGRAD_QUANT_SCALE_BITS - PJPG_DCT_SCALE_BITS));
  }
}

// These multiply helper functions are the 4 types of signed multiplies needed by the Winograd IDCT.
// A smart C compiler will optimize them to use 16x8 = 24 bit muls, if not you may need to tweak
// these functions or drop to CPU specific inline assembly.

// 1/cos(4*pi/16)
// 362, 256+106
static PJPG_INLINE int16 imul_b1_b3(int16 w) {
  long x = (w * 362L);
  x += 128L;
  return (int16)(PJPG_ARITH_SHIFT_RIGHT_8_L(x));
}

// 1/cos(6*pi/16)
// 669, 256+256+157
static PJPG_INLINE int16 imul_b2(int16 w) {
  long x = (w * 669L);
  x += 128L;
  return (int16)(PJPG_ARITH_SHIFT_RIGHT_8_L(x));
}

// 1/cos(2*pi/16)
// 277, 256+21
static PJPG_INLINE int16 imul_b4(int16 w) {
  long x = (w * 277L);
  x += 128L;
  return (int16)(PJPG_ARITH_SHIFT_RIGHT_8_L(x));
}

// 1/(cos(2*pi/16) + cos(6*pi/16))
// 196, 196
static PJPG_INLINE int16 imul_b5(int16 w) {
  long x = (w * 196L);
  x += 128L;
  return (int16)(PJPG_ARITH_SHIFT_RIGHT_8_L(x));
}

static PJPG_INLINE uint8 clamp(int16 s) {
  if ((uint16)s > 255U) {
    if (s < 0)
      return 0;
    else if (s > 255)
      return 255;
  }

  return (uint8)s;
}

static void idctRows(void) {
  uint8 i;
  int16* pSrc = gCoeffBuf;

  for (i = 0; i < 8; i++) {
    if ((pSrc[1] | pSrc[2] | pSrc[3] | pSrc[4] | pSrc[5] | pSrc[6] | pSrc[7]) == 0) {
      // Short circuit the 1D IDCT if only the DC component is non-zero
      int16 src0 = *pSrc;

      *(pSrc + 1) = src0;
      *(pSrc + 2) = src0;
      *(pSrc + 3) = src0;
      *(pSrc + 4) = src0;
      *(pSrc + 5) = src0;
      *(pSrc + 6) = src0;
      *(pSrc + 7) = src0;
    } else {
      int16 src4 = *(pSrc + 5);
      int16 src7 = *(pSrc + 3);
      int16 x4 = src4 - src7;
      int16 x7 = src4 + src7;

      int16 src5 = *(pSrc + 1);
      int16 src6 = *(pSrc + 7);
      int16 x5 = src5 + src6;
      int16 x6 = src5 - src6;

      int16 tmp1 = imul_b5(x4 - x6);
      int16 stg26 = imul_b4(x6) - tmp1;

      int16 x24 = tmp1 - imul_b2(x4);

      int16 x15 = x5 - x7;
      int16 x17 = x5 + x7;

      int16 tmp2 = stg26 - x17;
      int16 tmp3 = imul_b1_b3(x15) - tmp2;
      int16 x44 = tmp3 + x24;

      int16 src0 = *(pSrc + 0);
      int16 src1 = *(pSrc + 4);
      int16 x30 = src0 + src1;
      int16 x31 = src0 - src1;

      int16 src2 = *(pSrc + 2);
      int16 src3 = *(pSrc + 6);
      int16 x12 = src2 - src3;
      int16 x13 = src2 + src3;

      int16 x32 = imul_b1_b3(x12) - x13;

      int16 x40 = x30 + x13;
      int16 x43 = x30 - x13;
      int16 x41 = x31 + x32;
      int16 x42 = x31 - x32;

      *(pSrc + 0) = x40 + x17;
      *(pSrc + 1) = x41 + tmp2;
      *(pSrc + 2) = x42 + tmp3;
      *(pSrc + 3) = x43 - x44;
      *(pSrc + 4) = x43 + x44;
      *(pSrc + 5) = x42 - tmp3;
      *(pSrc + 6) = x41 - tmp2;
      *(pSrc + 7) = x40 - x17;
    }

    pSrc += 8;
  }
}

static void idctCols(void) {
  uint8 i;

  int16* pSrc = gCoeffBuf;

  for (i = 0; i < 8; i++) {
    if ((pSrc[1 * 8] | pSrc[2 * 8] | pSrc[3 * 8] | pSrc[4 * 8] | pSrc[5 * 8] | pSrc[6 * 8] | pSrc[7 * 8]) == 0) {
      // Short circuit the 1D IDCT if only the DC component is non-zero
      uint8 c = clamp(PJPG_DESCALE(*pSrc) + 128);
      *(pSrc + 0 * 8) = c;
      *(pSrc + 1 * 8) = c;
      *(pSrc + 2 * 8) = c;
      *(pSrc + 3 * 8) = c;
      *(pSrc + 4 * 8) = c;
      *(pSrc + 5 * 8) = c;
      *(pSrc + 6 * 8) = c;
      *(pSrc + 7 * 8) = c;
    } else {
      int16 src4 = *(pSrc + 5 * 8);
      int16 src7 = *(pSrc + 3 * 8);
      int16 x4 = src4 - src7;
      int16 x7 = src4 + src7;

      int16 src5 = *(pSrc + 1 * 8);
      int16 src6 = *(pSrc + 7 * 8);
      int16 x5 = src5 + src6;
      int16 x6 = src5 - src6;

      int16 tmp1 = imul_b5(x4 - x6);
      int16 stg26 = imul_b4(x6) - tmp1;

      int16 x24 = tmp1 - imul_b2(x4);

      int16 x15 = x5 - x7;
      int16 x17 = x5 + x7;

      int16 tmp2 = stg26 - x17;
      int16 tmp3 = imul_b1_b3(x15) - tmp2;
      int16 x44 = tmp3 + x24;

      int16 src0 = *(pSrc + 0 * 8);
      int16 src1 = *(pSrc + 4 * 8);
      int16 x30 = src0 + src1;
      int16 x31 = src0 - src1;

      int16 src2 = *(pSrc + 2 * 8);
      int16 src3 = *(pSrc + 6 * 8);
      int16 x12 = src2 - src3;
      int16 x13 = src2 + src3;

      int16 x32 = imul_b1_b3(x12) - x13;

      int16 x40 = x30 + x13;
      int16 x43 = x30 - x13;
      int16 x41 = x31 + x32;
      int16 x42 = x31 - x32;

      // descale, convert to unsigned and clamp to 8-bit
      *(pSrc + 0 * 8) = clamp(PJPG_DESCALE(x40 + x17) + 128);
      *(pSrc + 1 * 8) = clamp(PJPG_DESCALE(x41 + tmp2) + 128);
      *(pSrc + 2 * 8) = clamp(PJPG_DESCALE(x42 + tmp3) + 128);
      *(pSrc + 3 * 8) = clamp(PJPG_DESCALE(x43 - x44) + 128);
      *(pSrc + 4 * 8) = clamp(PJPG_DESCALE(x43 + x44) + 128);
      *(pSrc + 5 * 8) = clamp(PJPG_DESCALE(x42 - tmp3) + 128);
      *(pSrc + 6 * 8) = clamp(PJPG_DESCALE(x41 - tmp2) + 128);
      *(pSrc + 7 * 8) = clamp(PJPG_DESCALE(x40 - x17) + 128);
    }

    pSrc++;
  }
}

/*----------------------------------------------------------------------------*/
static PJPG_INLINE uint8 addAndClamp(uint8 a, int16 b) {
  b = a + b;

  if ((uint16)b > 255U) {
    if (b < 0)
      return 0;
    else if (b > 255)
      return 255;
  }

  return (uint8)b;
}
/*----------------------------------------------------------------------------*/
static PJPG_INLINE uint8 subAndClamp(uint8 a, int16 b) {
  b = a - b;

  if ((uint16)b > 255U) {
    if (b < 0)
      return 0;
    else if (b > 255)
      return 255;
  }

  return (uint8)b;
}
/*----------------------------------------------------------------------------*/
// 103/256
// R = Y + 1.402 (Cr-128)

// 88/256, 183/256
// G = Y - 0.34414 (Cb-128) - 0.71414 (Cr-128)

// 198/256
// B = Y + 1.772 (Cb-128)
/*----------------------------------------------------------------------------*/
// Cb upsample and accumulate, 4x4 to 8x8
static void upsampleCb(uint8 srcOfs, uint8 dstOfs) {
  // Cb - affects G and B
  uint8 x, y;
  int16* pSrc = gCoeffBuf + srcOfs;
  uint8* pDstG = gMCUBufG + dstOfs;
  uint8* pDstB = gMCUBufB + dstOfs;
  for (y = 0; y < 4; y++) {
    for (x = 0; x < 4; x++) {
      uint8 cb = (uint8)*pSrc++;
      int16 cbG, cbB;

      cbG = ((cb * 88U) >> 8U) - 44U;
      pDstG[0] = subAndClamp(pDstG[0], cbG);
      pDstG[1] = subAndClamp(pDstG[1], cbG);
      pDstG[8] = subAndClamp(pDstG[8], cbG);
      pDstG[9] = subAndClamp(pDstG[9], cbG);

      cbB = (cb + ((cb * 198U) >> 8U)) - 227U;
      pDstB[0] = addAndClamp(pDstB[0], cbB);
      pDstB[1] = addAndClamp(pDstB[1], cbB);
      pDstB[8] = addAndClamp(pDstB[8], cbB);
      pDstB[9] = addAndClamp(pDstB[9], cbB);

      pDstG += 2;
      pDstB += 2;
    }

    pSrc = pSrc - 4 + 8;
    pDstG = pDstG - 8 + 16;
    pDstB = pDstB - 8 + 16;
  }
}
/*----------------------------------------------------------------------------*/
// Cb upsample and accumulate, 4x8 to 8x8
static void upsampleCbH(uint8 srcOfs, uint8 dstOfs) {
  // Cb - affects G and B
  uint8 x, y;
  int16* pSrc = gCoeffBuf + srcOfs;
  uint8* pDstG = gMCUBufG + dstOfs;
  uint8* pDstB = gMCUBufB + dstOfs;
  for (y = 0; y < 8; y++) {
    for (x = 0; x < 4; x++) {
      uint8 cb = (uint8)*pSrc++;
      int16 cbG, cbB;

      cbG = ((cb * 88U) >> 8U) - 44U;
      pDstG[0] = subAndClamp(pDstG[0], cbG);
      pDstG[1] = subAndClamp(pDstG[1], cbG);

      cbB = (cb + ((cb * 198U) >> 8U)) - 227U;
      pDstB[0] = addAndClamp(pDstB[0], cbB);
      pDstB[1] = addAndClamp(pDstB[1], cbB);

      pDstG += 2;
      pDstB += 2;
    }

    pSrc = pSrc - 4 + 8;
  }
}
/*----------------------------------------------------------------------------*/
// Cb upsample and accumulate, 8x4 to 8x8
static void upsampleCbV(uint8 srcOfs, uint8 dstOfs) {
  // Cb - affects G and B
  uint8 x, y;
  int16* pSrc = gCoeffBuf + srcOfs;
  uint8* pDstG = gMCUBufG + dstOfs;
  uint8* pDstB = gMCUBufB + dstOfs;
  for (y = 0; y < 4; y++) {
    for (x = 0; x < 8; x++) {
      uint8 cb = (uint8)*pSrc++;
      int16 cbG, cbB;

      cbG = ((cb * 88U) >> 8U) - 44U;
      pDstG[0] = subAndClamp(pDstG[0], cbG);
      pDstG[8] = subAndClamp(pDstG[8], cbG);

      cbB = (cb + ((cb * 198U) >> 8U)) - 227U;
      pDstB[0] = addAndClamp(pDstB[0], cbB);
      pDstB[8] = addAndClamp(pDstB[8], cbB);

      ++pDstG;
      ++pDstB;
    }

    pDstG = pDstG - 8 + 16;
    pDstB = pDstB - 8 + 16;
  }
}
/*----------------------------------------------------------------------------*/
// 103/256
// R = Y + 1.402 (Cr-128)

// 88/256, 183/256
// G = Y - 0.34414 (Cb-128) - 0.71414 (Cr-128)

// 198/256
// B = Y + 1.772 (Cb-128)
/*----------------------------------------------------------------------------*/
// Cr upsample and accumulate, 4x4 to 8x8
static void upsampleCr(uint8 srcOfs, uint8 dstOfs) {
  // Cr - affects R and G
  uint8 x, y;
  int16* pSrc = gCoeffBuf + srcOfs;
  uint8* pDstR = gMCUBufR + dstOfs;
  uint8* pDstG = gMCUBufG + dstOfs;
  for (y = 0; y < 4; y++) {
    for (x = 0; x < 4; x++) {
      uint8 cr = (uint8)*pSrc++;
      int16 crR, crG;

      crR = (cr + ((cr * 103U) >> 8U)) - 179;
      pDstR[0] = addAndClamp(pDstR[0], crR);
      pDstR[1] = addAndClamp(pDstR[1], crR);
      pDstR[8] = addAndClamp(pDstR[8], crR);
      pDstR[9] = addAndClamp(pDstR[9], crR);

      crG = ((cr * 183U) >> 8U) - 91;
      pDstG[0] = subAndClamp(pDstG[0], crG);
      pDstG[1] = subAndClamp(pDstG[1], crG);
      pDstG[8] = subAndClamp(pDstG[8], crG);
      pDstG[9] = subAndClamp(pDstG[9], crG);

      pDstR += 2;
      pDstG += 2;
    }

    pSrc = pSrc - 4 + 8;
    pDstR = pDstR - 8 + 16;
    pDstG = pDstG - 8 + 16;
  }
}
/*----------------------------------------------------------------------------*/
// Cr upsample and accumulate, 4x8 to 8x8
static void upsampleCrH(uint8 srcOfs, uint8 dstOfs) {
  // Cr - affects R and G
  uint8 x, y;
  int16* pSrc = gCoeffBuf + srcOfs;
  uint8* pDstR = gMCUBufR + dstOfs;
  uint8* pDstG = gMCUBufG + dstOfs;
  for (y = 0; y < 8; y++) {
    for (x = 0; x < 4; x++) {
      uint8 cr = (uint8)*pSrc++;
      int16 crR, crG;

      crR = (cr + ((cr * 103U) >> 8U)) - 179;
      pDstR[0] = addAndClamp(pDstR[0], crR);
      pDstR[1] = addAndClamp(pDstR[1], crR);

      crG = ((cr * 183U) >> 8U) - 91;
      pDstG[0] = subAndClamp(pDstG[0], crG);
      pDstG[1] = subAndClamp(pDstG[1], crG);

      pDstR += 2;
      pDstG += 2;
    }

    pSrc = pSrc - 4 + 8;
  }
}
/*----------------------------------------------------------------------------*/
// Cr upsample and accumulate, 8x4 to 8x8
static void upsampleCrV(uint8 srcOfs, uint8 dstOfs) {
  // Cr - affects R and G
  uint8 x, y;
  int16* pSrc = gCoeffBuf + srcOfs;
  uint8* pDstR = gMCUBufR + dstOfs;
  uint8* pDstG = gMCUBufG + dstOfs;
  for (y = 0; y < 4; y++) {
    for (x = 0; x < 8; x++) {
      uint8 cr = (uint8)*pSrc++;
      int16 crR, crG;

      crR = (cr + ((cr * 103U) >> 8U)) - 179;
      pDstR[0] = addAndClamp(pDstR[0], crR);
      pDstR[8] = addAndClamp(pDstR[8], crR);

      crG = ((cr * 183U) >> 8U) - 91;
      pDstG[0] = subAndClamp(pDstG[0], crG);
      pDstG[8] = subAndClamp(pDstG[8], crG);

      ++pDstR;
      ++pDstG;
    }

    pDstR = pDstR - 8 + 16;
    pDstG = pDstG - 8 + 16;
  }
}
/*----------------------------------------------------------------------------*/
// Convert Y to RGB
static void copyY(uint8 dstOfs) {
  uint8 i;
  uint8* pRDst = gMCUBufR + dstOfs;
  uint8* pGDst = gMCUBufG + dstOfs;
  uint8* pBDst = gMCUBufB + dstOfs;
  int16* pSrc = gCoeffBuf;

  for (i = 64; i > 0; i--) {
    uint8 c = (uint8)*pSrc++;

    *pRDst++ = c;
    *pGDst++ = c;
    *pBDst++ = c;
  }
}
/*----------------------------------------------------------------------------*/
// Cb convert to RGB and accumulate
static void convertCb(uint8 dstOfs) {
  uint8 i;
  uint8* pDstG = gMCUBufG + dstOfs;
  uint8* pDstB = gMCUBufB + dstOfs;
  int16* pSrc = gCoeffBuf;

  for (i = 64; i > 0; i--) {
    uint8 cb = (uint8)*pSrc++;
    int16 cbG, cbB;

    cbG = ((cb * 88U) >> 8U) - 44U;
    *pDstG++ = subAndClamp(pDstG[0], cbG);

    cbB = (cb + ((cb * 198U) >> 8U)) - 227U;
    *pDstB++ = addAndClamp(pDstB[0], cbB);
  }
}
/*----------------------------------------------------------------------------*/
// Cr convert to RGB and accumulate
static void convertCr(uint8 dstOfs) {
  uint8 i;
  uint8* pDstR = gMCUBufR + dstOfs;
  uint8* pDstG = gMCUBufG + dstOfs;
  int16* pSrc = gCoeffBuf;

  for (i = 64; i > 0; i--) {
    uint8 cr = (uint8)*pSrc++;
    int16 crR, crG;

    crR = (cr + ((cr * 103U) >> 8U)) - 179;
    *pDstR++ = addAndClamp(pDstR[0], crR);

    crG = ((cr * 183U) >> 8U) - 91;
    *pDstG++ = subAndClamp(pDstG[0], crG);
  }
}
/*----------------------------------------------------------------------------*/
static void transformBlock(uint8 mcuBlock) {
  idctRows();
  idctCols();

  switch (gScanType) {
    case PJPG_GRAYSCALE: {
      // MCU size: 1, 1 block per MCU
      copyY(0);
      break;
    }
    case PJPG_YH1V1: {
      // MCU size: 8x8, 3 blocks per MCU
      switch (mcuBlock) {
        case 0: {
          copyY(0);
          break;
        }
        case 1: {
          convertCb(0);
          break;
        }
        case 2: {
          convertCr(0);
          break;
        }
      }

      break;
    }
    case PJPG_YH1V2: {
      // MCU size: 8x16, 4 blocks per MCU
      switch (mcuBlock) {
        case 0: {
          copyY(0);
          break;
        }
        case 1: {
          copyY(128);
          break;
        }
        case 2: {
          upsampleCbV(0, 0);
          upsampleCbV(4 * 8, 128);
          break;
        }
        case 3: {
          upsampleCrV(0, 0);
          upsampleCrV(4 * 8, 128);
          break;
        }
      }

      break;
    }
    case PJPG_YH2V1: {
      // MCU size: 16x8, 4 blocks per MCU
      switch (mcuBlock) {
        case 0: {
          copyY(0);
          break;
        }
        case 1: {
          copyY(64);
          break;
        }
        case 2: {
          upsampleCbH(0, 0);
          upsampleCbH(4, 64);
          break;
        }
        case 3: {
          upsampleCrH(0, 0);
          upsampleCrH(4, 64);
          break;
        }
      }

      break;
    }
    case PJPG_YH2V2: {
      // MCU size: 16x16, 6 blocks per MCU
      switch (mcuBlock) {
        case 0: {
          copyY(0);
          break;
        }
        case 1: {
          copyY(64);
          break;
        }
        case 2: {
          copyY(128);
          break;
        }
        case 3: {
          copyY(192);
          break;
        }
        case 4: {
          upsampleCb(0, 0);
          upsampleCb(4, 64);
          upsampleCb(4 * 8, 128);
          upsampleCb(4 + 4 * 8, 192);
          break;
        }
        case 5: {
          upsampleCr(0, 0);
          upsampleCr(4, 64);
          upsampleCr(4 * 8, 128);
          upsampleCr(4 + 4 * 8, 192);
          break;
        }
      }

      break;
    }
  }
}
//------------------------------------------------------------------------------
static void transformBlockReduce(uint8 mcuBlock) {
  uint8 c = clamp(PJPG_DESCALE(gCoeffBuf[0]) + 128);
  int16 cbG, cbB, crR, crG;

  switch (gScanType) {
    case PJPG_GRAYSCALE: {
      // MCU size: 1, 1 block per MCU
      gMCUBufR[0] = c;
      break;
    }
    case PJPG_YH1V1: {
      // MCU size: 8x8, 3 blocks per MCU
      switch (mcuBlock) {
        case 0: {
          gMCUBufR[0] = c;
          gMCUBufG[0] = c;
          gMCUBufB[0] = c;
          break;
        }
        case 1: {
          cbG = ((c * 88U) >> 8U) - 44U;
          gMCUBufG[0] = subAndClamp(gMCUBufG[0], cbG);

          cbB = (c + ((c * 198U) >> 8U)) - 227U;
          gMCUBufB[0] = addAndClamp(gMCUBufB[0], cbB);
          break;
        }
        case 2: {
          crR = (c + ((c * 103U) >> 8U)) - 179;
          gMCUBufR[0] = addAndClamp(gMCUBufR[0], crR);

          crG = ((c * 183U) >> 8U) - 91;
          gMCUBufG[0] = subAndClamp(gMCUBufG[0], crG);
          break;
        }
      }

      break;
    }
    case PJPG_YH1V2: {
      // MCU size: 8x16, 4 blocks per MCU
      switch (mcuBlock) {
        case 0: {
          gMCUBufR[0] = c;
          gMCUBufG[0] = c;
          gMCUBufB[0] = c;
          break;
        }
        case 1: {
          gMCUBufR[128] = c;
          gMCUBufG[128] = c;
          gMCUBufB[128] = c;
          break;
        }
        case 2: {
          cbG = ((c * 88U) >> 8U) - 44U;
          gMCUBufG[0] = subAndClamp(gMCUBufG[0], cbG);
          gMCUBufG[128] = subAndClamp(gMCUBufG[128], cbG);

          cbB = (c + ((c * 198U) >> 8U)) - 227U;
          gMCUBufB[0] = addAndClamp(gMCUBufB[0], cbB);
          gMCUBufB[128] = addAndClamp(gMCUBufB[128], cbB);

          break;
        }
        case 3: {
          crR = (c + ((c * 103U) >> 8U)) - 179;
          gMCUBufR[0] = addAndClamp(gMCUBufR[0], crR);
          gMCUBufR[128] = addAndClamp(gMCUBufR[128], crR);

          crG = ((c * 183U) >> 8U) - 91;
          gMCUBufG[0] = subAndClamp(gMCUBufG[0], crG);
          gMCUBufG[128] = subAndClamp(gMCUBufG[128], crG);

          break;
        }
      }
      break;
    }
    case PJPG_YH2V1: {
      // MCU size: 16x8, 4 blocks per MCU
      switch (mcuBlock) {
        case 0: {
          gMCUBufR[0] = c;
          gMCUBufG[0] = c;
          gMCUBufB[0] = c;
          break;
        }
        case 1: {
          gMCUBufR[64] = c;
          gMCUBufG[64] = c;
          gMCUBufB[64] = c;
          break;
        }
        case 2: {
          cbG = ((c * 88U) >> 8U) - 44U;
          gMCUBufG[0] = subAndClamp(gMCUBufG[0], cbG);
          gMCUBufG[64] = subAndClamp(gMCUBufG[64], cbG);

          cbB = (c + ((c * 198U) >> 8U)) - 227U;
          gMCUBufB[0] = addAndClamp(gMCUBufB[0], cbB);
          gMCUBufB[64] = addAndClamp(gMCUBufB[64], cbB);

          break;
        }
        case 3: {
          crR = (c + ((c * 103U) >> 8U)) - 179;
          gMCUBufR[0] = addAndClamp(gMCUBufR[0], crR);
          gMCUBufR[64] = addAndClamp(gMCUBufR[64], crR);

          crG = ((c * 183U) >> 8U) - 91;
          gMCUBufG[0] = subAndClamp(gMCUBufG[0], crG);
          gMCUBufG[64] = subAndClamp(gMCUBufG[64], crG);

          break;
        }
      }
      break;
    }
    case PJPG_YH2V2: {
      // MCU size: 16x16, 6 blocks per MCU
      switch (mcuBlock) {
        case 0: {
          gMCUBufR[0] = c;
          gMCUBufG[0] = c;
          gMCUBufB[0] = c;
          break;
        }
        case 1: {
          gMCUBufR[64] = c;
          gMCUBufG[64] = c;
          gMCUBufB[64] = c;
          break;
        }
        case 2: {
          gMCUBufR[128] = c;
          gMCUBufG[128] = c;
          gMCUBufB[128] = c;
          break;
        }
        case 3: {
          gMCUBufR[192] = c;
          gMCUBufG[192] = c;
          gMCUBufB[192] = c;
          break;
        }
        case 4: {
          cbG = ((c * 88U) >> 8U) - 44U;
          gMCUBufG[0] = subAndClamp(gMCUBufG[0], cbG);
          gMCUBufG[64] = subAndClamp(gMCUBufG[64], cbG);
          gMCUBufG[128] = subAndClamp(gMCUBufG[128], cbG);
          gMCUBufG[192] = subAndClamp(gMCUBufG[192], cbG);

          cbB = (c + ((c * 198U) >> 8U)) - 227U;
          gMCUBufB[0] = addAndClamp(gMCUBufB[0], cbB);
          gMCUBufB[64] = addAndClamp(gMCUBufB[64], cbB);
          gMCUBufB[128] = addAndClamp(gMCUBufB[128], cbB);
          gMCUBufB[192] = addAndClamp(gMCUBufB[192], cbB);

          break;
        }
        case 5: {
          crR = (c + ((c * 103U) >> 8U)) - 179;
          gMCUBufR[0] = addAndClamp(gMCUBufR[0], crR);
          gMCUBufR[64] = addAndClamp(gMCUBufR[64], crR);
          gMCUBufR[128] = addAndClamp(gMCUBufR[128], crR);
          gMCUBufR[192] = addAndClamp(gMCUBufR[192], crR);

          crG = ((c * 183U) >> 8U) - 91;
          gMCUBufG[0] = subAndClamp(gMCUBufG[0], crG);
          gMCUBufG[64] = subAndClamp(gMCUBufG[64], crG);
          gMCUBufG[128] = subAndClamp(gMCUBufG[128], crG);
          gMCUBufG[192] = subAndClamp(gMCUBufG[192], crG);

          break;
        }
      }
      break;
    }
  }
}
//------------------------------------------------------------------------------
static uint8 decodeNextMCU(void) {
  uint8 status;
  uint8 mcuBlock;

  if (gRestartInterval) {
    if (gRestartsLeft == 0) {
      status = processRestart();
      if (status) return status;
    }
    gRestartsLeft--;
  }

  for (mcuBlock = 0; mcuBlock < gMaxBlocksPerMCU; mcuBlock++) {
    uint8 componentID = gMCUOrg[mcuBlock];
    uint8 compQuant = gCompQuant[componentID];
    uint8 compDCTab = gCompDCTab[componentID];
    uint8 numExtraBits, compACTab, k;
    const int16* pQ = compQuant ? gQuant1 : gQuant0;
    uint16 r, dc;

    uint8 s = huffDecode(compDCTab ? &gHuffTab1 : &gHuffTab0, compDCTab ? gHuffVal1 : gHuffVal0);

    r = 0;
    numExtraBits = s & 0xF;
    if (numExtraBits) r = getBits2(numExtraBits);
    dc = huffExtend(r, s);

    dc = dc + gLastDC[componentID];
    gLastDC[componentID] = dc;

    gCoeffBuf[0] = dc * pQ[0];

    compACTab = gCompACTab[componentID];

    if (gReduce) {
      // Decode, but throw out the AC coefficients in reduce mode.
      for (k = 1; k < 64; k++) {
        s = huffDecode(compACTab ? &gHuffTab3 : &gHuffTab2, compACTab ? gHuffVal3 : gHuffVal2);

        numExtraBits = s & 0xF;
        if (numExtraBits) getBits2(numExtraBits);

        r = s >> 4;
        s &= 15;

        if (s) {
          if (r) {
            if ((k + r) > 63) return PJPG_DECODE_ERROR;

            k = (uint8)(k + r);
          }
        } else {
          if (r == 15) {
            if ((k + 16) > 64) return PJPG_DECODE_ERROR;

            k += (16 - 1);  // - 1 because the loop counter is k
          } else
            break;
        }
      }

      transformBlockReduce(mcuBlock);
    } else {
      // Decode and dequantize AC coefficients
      for (k = 1; k < 64; k++) {
        uint16 extraBits;

        s = huffDecode(compACTab ? &gHuffTab3 : &gHuffTab2, compACTab ? gHuffVal3 : gHuffVal2);

        extraBits = 0;
        numExtraBits = s & 0xF;
        if (numExtraBits) extraBits = getBits2(numExtraBits);

        r = s >> 4;
        s &= 15;

        if (s) {
          int16 ac;

          if (r) {
            if ((k + r) > 63) return PJPG_DECODE_ERROR;

            while (r) {
              gCoeffBuf[ZAG[k++]] = 0;
              r--;
            }
          }

          ac = huffExtend(extraBits, s);

          gCoeffBuf[ZAG[k]] = ac * pQ[k];
        } else {
          if (r == 15) {
            if ((k + 16) > 64) return PJPG_DECODE_ERROR;

            for (r = 16; r > 0; r--) gCoeffBuf[ZAG[k++]] = 0;

            k--;  // - 1 because the loop counter is k
          } else
            break;
        }
      }

      while (k < 64) gCoeffBuf[ZAG[k++]] = 0;

      transformBlock(mcuBlock);
    }
  }

  return 0;
}
//------------------------------------------------------------------------------
unsigned char pjpeg_decode_mcu(void) {
  uint8 status;

  if (gCallbackStatus) return gCallbackStatus;

  if ((!gNumMCUSRemainingX) && (!gNumMCUSRemainingY)) return PJPG_NO_MORE_BLOCKS;

  status = decodeNextMCU();
  if ((status) || (gCallbackStatus)) return gCallbackStatus ? gCallbackStatus : status;

  gNumMCUSRemainingX--;
  if (!gNumMCUSRemainingX) {
    gNumMCUSRemainingY--;
    if (gNumMCUSRemainingY > 0) gNumMCUSRemainingX = gMaxMCUSPerRow;
  }

  return 0;
}
//------------------------------------------------------------------------------
unsigned char pjpeg_decode_init(pjpeg_image_info_t* pInfo, pjpeg_need_bytes_callback_t pNeed_bytes_callback,
                                void* pCallback_data, unsigned char reduce) {
  uint8 status;

  pInfo->m_width = 0;
  pInfo->m_height = 0;
  pInfo->m_comps = 0;
  pInfo->m_MCUSPerRow = 0;
  pInfo->m_MCUSPerCol = 0;
  pInfo->m_scanType = PJPG_GRAYSCALE;
  pInfo->m_MCUWidth = 0;
  pInfo->m_MCUHeight = 0;
  pInfo->m_pMCUBufR = (unsigned char*)0;
  pInfo->m_pMCUBufG = (unsigned char*)0;
  pInfo->m_pMCUBufB = (unsigned char*)0;

  g_pNeedBytesCallback = pNeed_bytes_callback;
  g_pCallback_data = pCallback_data;
  gCallbackStatus = 0;
  gReduce = reduce;

  status = init();
  if ((status) || (gCallbackStatus)) return gCallbackStatus ? gCallbackStatus : status;

  status = locateSOFMarker();
  if ((status) || (gCallbackStatus)) return gCallbackStatus ? gCallbackStatus : status;

  status = initFrame();
  if ((status) || (gCallbackStatus)) return gCallbackStatus ? gCallbackStatus : status;

  status = initScan();
  if ((status) || (gCallbackStatus)) return gCallbackStatus ? gCallbackStatus : status;

  pInfo->m_width = gImageXSize;
  pInfo->m_height = gImageYSize;
  pInfo->m_comps = gCompsInFrame;
  pInfo->m_scanType = gScanType;
  pInfo->m_MCUSPerRow = gMaxMCUSPerRow;
  pInfo->m_MCUSPerCol = gMaxMCUSPerCol;
  pInfo->m_MCUWidth = gMaxMCUXSize;
  pInfo->m_MCUHeight = gMaxMCUYSize;
  pInfo->m_pMCUBufR = gMCUBufR;
  pInfo->m_pMCUBufG = gMCUBufG;
  pInfo->m_pMCUBufB = gMCUBufB;

  return 0;
}
