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picojpeg.c
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//------------------------------------------------------------------------------
// picojpeg.c v1.1 - Public domain, Rich Geldreich <[email protected]>
// 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 <[email protected]>.
//------------------------------------------------------------------------------
#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 1
// Define PJPG_INLINE to "inline" if your C compiler supports explicit inlining
#define PJPG_INLINE inline
//------------------------------------------------------------------------------
typedef unsigned char uint8;
typedef unsigned short uint16;
typedef signed char int8;
typedef signed short int16;
//------------------------------------------------------------------------------
#ifdef 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 gNumMCUSRemaining;
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;