/*----------------------------------------------------------------------------/
/ TJpgDec - Tiny JPEG Decompressor R0.03                      (C)ChaN, 2021
/-----------------------------------------------------------------------------/
/ The TJpgDec is a generic JPEG decompressor module for tiny embedded systems.
/ This is a free software that opened for education, research and commercial
/  developments under license policy of following terms.
/
/  Copyright (C) 2021, ChaN, all right reserved.
/
/ * The TJpgDec module is a free software and there is NO WARRANTY.
/ * No restriction on use. You can use, modify and redistribute it for
/   personal, non-profit or commercial products UNDER YOUR RESPONSIBILITY.
/ * Redistributions of source code must retain the above copyright notice.
/
/-----------------------------------------------------------------------------/
/ Oct 04, 2011 R0.01  First release.
/ Feb 19, 2012 R0.01a Fixed decompression fails when scan starts with an escape seq.
/ Sep 03, 2012 R0.01b Added JD_TBLCLIP option.
/ Mar 16, 2019 R0.01c Supprted stdint.h.
/ Jul 01, 2020 R0.01d Fixed wrong integer type usage.
/ May 08, 2021 R0.02  Supprted grayscale image. Separated configuration options.
/ Jun 11, 2021 R0.02a Some performance improvement.
/ Jul 01, 2021 R0.03  Added JD_FASTDECODE option.
/                     Some performance improvement.
/----------------------------------------------------------------------------*/

#include "tjpgd.h"

#if JD_FASTDECODE == 2
#define HUFF_BIT  10 /* Bit length to apply fast huffman decode */
#define HUFF_LEN  (1 << HUFF_BIT)
#define HUFF_MASK (HUFF_LEN - 1)
#endif

/*-----------------------------------------------*/
/* Zigzag-order to raster-order conversion table */
/*-----------------------------------------------*/

static uint8_t Zig[64] = { /* Zigzag-order to raster-order conversion table */
                           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
};

/*-------------------------------------------------*/
/* Input scale factor of Arai algorithm            */
/* (scaled up 16 bits for fixed point operations)  */
/*-------------------------------------------------*/

static uint16_t Ipsf[64] = { /* See also aa_idct.png */
                             (uint16_t)(1.00000 * 8192), (uint16_t)(1.38704 * 8192), (uint16_t)(1.30656 * 8192), (uint16_t)(1.17588 * 8192), (uint16_t)(1.00000 * 8192), (uint16_t)(0.78570 * 8192), (uint16_t)(0.54120 * 8192), (uint16_t)(0.27590 * 8192),
                             (uint16_t)(1.38704 * 8192), (uint16_t)(1.92388 * 8192), (uint16_t)(1.81226 * 8192), (uint16_t)(1.63099 * 8192), (uint16_t)(1.38704 * 8192), (uint16_t)(1.08979 * 8192), (uint16_t)(0.75066 * 8192), (uint16_t)(0.38268 * 8192),
                             (uint16_t)(1.30656 * 8192), (uint16_t)(1.81226 * 8192), (uint16_t)(1.70711 * 8192), (uint16_t)(1.53636 * 8192), (uint16_t)(1.30656 * 8192), (uint16_t)(1.02656 * 8192), (uint16_t)(0.70711 * 8192), (uint16_t)(0.36048 * 8192),
                             (uint16_t)(1.17588 * 8192), (uint16_t)(1.63099 * 8192), (uint16_t)(1.53636 * 8192), (uint16_t)(1.38268 * 8192), (uint16_t)(1.17588 * 8192), (uint16_t)(0.92388 * 8192), (uint16_t)(0.63638 * 8192), (uint16_t)(0.32442 * 8192),
                             (uint16_t)(1.00000 * 8192), (uint16_t)(1.38704 * 8192), (uint16_t)(1.30656 * 8192), (uint16_t)(1.17588 * 8192), (uint16_t)(1.00000 * 8192), (uint16_t)(0.78570 * 8192), (uint16_t)(0.54120 * 8192), (uint16_t)(0.27590 * 8192),
                             (uint16_t)(0.78570 * 8192), (uint16_t)(1.08979 * 8192), (uint16_t)(1.02656 * 8192), (uint16_t)(0.92388 * 8192), (uint16_t)(0.78570 * 8192), (uint16_t)(0.61732 * 8192), (uint16_t)(0.42522 * 8192), (uint16_t)(0.21677 * 8192),
                             (uint16_t)(0.54120 * 8192), (uint16_t)(0.75066 * 8192), (uint16_t)(0.70711 * 8192), (uint16_t)(0.63638 * 8192), (uint16_t)(0.54120 * 8192), (uint16_t)(0.42522 * 8192), (uint16_t)(0.29290 * 8192), (uint16_t)(0.14932 * 8192),
                             (uint16_t)(0.27590 * 8192), (uint16_t)(0.38268 * 8192), (uint16_t)(0.36048 * 8192), (uint16_t)(0.32442 * 8192), (uint16_t)(0.27590 * 8192), (uint16_t)(0.21678 * 8192), (uint16_t)(0.14932 * 8192), (uint16_t)(0.07612 * 8192)
};

/*---------------------------------------------*/
/* Conversion table for fast clipping process  */
/*---------------------------------------------*/

#if JD_TBLCLIP

#define BYTECLIP(v) Clip8[(unsigned int)(v)&0x3FF]

static uint8_t Clip8[1024] = {
    /* 0..255 */
    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
    32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
    64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95,
    96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127,
    128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159,
    160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191,
    192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223,
    224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255,
    /* 256..511 */
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    /* -512..-257 */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    /* -256..-1 */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

#else /* JD_TBLCLIP */

static uint8_t BYTECLIP(int val)
{
    if (val < 0)
        return 0;
    if (val > 255)
        return 255;
    return (uint8_t)val;
}

#endif

/*-----------------------------------------------------------------------*/
/* Allocate a memory block from memory pool                              */
/*-----------------------------------------------------------------------*/

static void *alloc_pool(             /* Pointer to allocated memory block (NULL:no memory available) */
                        JDEC *jd,    /* Pointer to the decompressor object */
                        size_t ndata /* Number of bytes to allocate */
)
{
    char *rp = 0;

    ndata = (ndata + 3) & ~3; /* Align block size to the word boundary */

    if (jd->sz_pool >= ndata) {
        jd->sz_pool -= ndata;
        rp = (char *)jd->pool;           /* Get start of available memory pool */
        jd->pool = (void *)(rp + ndata); /* Allocate requierd bytes */
    }

    return (void *)rp; /* Return allocated memory block (NULL:no memory to allocate) */
}

/*-----------------------------------------------------------------------*/
/* Create de-quantization and prescaling tables with a DQT segment       */
/*-----------------------------------------------------------------------*/

static JRESULT create_qt_tbl(                     /* 0:OK, !0:Failed */
                             JDEC *jd,            /* Pointer to the decompressor object */
                             const uint8_t *data, /* Pointer to the quantizer tables */
                             size_t ndata         /* Size of input data */
)
{
    unsigned int i, zi;
    uint8_t d;
    int32_t *pb;

    while (ndata) { /* Process all tables in the segment */
        if (ndata < 65)
            return JDR_FMT1; /* Err: table size is unaligned */
        ndata -= 65;
        d = *data++; /* Get table property */
        if (d & 0xF0)
            return JDR_FMT1;                       /* Err: not 8-bit resolution */
        i = d & 3;                                 /* Get table ID */
        pb = alloc_pool(jd, 64 * sizeof(int32_t)); /* Allocate a memory block for the table */
        if (!pb)
            return JDR_MEM1;                                  /* Err: not enough memory */
        jd->qttbl[i] = pb;                                    /* Register the table */
        for (i = 0; i < 64; i++) {                            /* Load the table */
            zi = Zig[i];                                      /* Zigzag-order to raster-order conversion */
            pb[zi] = (int32_t)((uint32_t)*data++ * Ipsf[zi]); /* Apply scale factor of Arai algorithm to the de-quantizers */
        }
    }

    return JDR_OK;
}

/*-----------------------------------------------------------------------*/
/* Create huffman code tables with a DHT segment                         */
/*-----------------------------------------------------------------------*/

static JRESULT create_huffman_tbl(                     /* 0:OK, !0:Failed */
                                  JDEC *jd,            /* Pointer to the decompressor object */
                                  const uint8_t *data, /* Pointer to the packed huffman tables */
                                  size_t ndata         /* Size of input data */
)
{
    unsigned int i, j, b, cls, num;
    size_t np;
    uint8_t d, *pb, *pd;
    uint16_t hc, *ph;

    while (ndata) { /* Process all tables in the segment */
        if (ndata < 17)
            return JDR_FMT1; /* Err: wrong data size */
        ndata -= 17;
        d = *data++; /* Get table number and class */
        if (d & 0xEE)
            return JDR_FMT1; /* Err: invalid class/number */
        cls = d >> 4;
        num = d & 0x0F;          /* class = dc(0)/ac(1), table number = 0/1 */
        pb = alloc_pool(jd, 16); /* Allocate a memory block for the bit distribution table */
        if (!pb)
            return JDR_MEM1; /* Err: not enough memory */
        jd->huffbits[num][cls] = pb;
        for (np = i = 0; i < 16; i++) { /* Load number of patterns for 1 to 16-bit code */
            np += (pb[i] = *data++);    /* Get sum of code words for each code */
        }
        ph = alloc_pool(jd, np * sizeof(uint16_t)); /* Allocate a memory block for the code word table */
        if (!ph)
            return JDR_MEM1; /* Err: not enough memory */
        jd->huffcode[num][cls] = ph;
        hc = 0;
        for (j = i = 0; i < 16; i++) { /* Re-build huffman code word table */
            b = pb[i];
            while (b--)
                ph[j++] = hc++;
            hc <<= 1;
        }

        if (ndata < np)
            return JDR_FMT1; /* Err: wrong data size */
        ndata -= np;
        pd = alloc_pool(jd, np); /* Allocate a memory block for the decoded data */
        if (!pd)
            return JDR_MEM1; /* Err: not enough memory */
        jd->huffdata[num][cls] = pd;
        for (i = 0; i < np; i++) { /* Load decoded data corresponds to each code word */
            d = *data++;
            if (!cls && d > 11)
                return JDR_FMT1;
            pd[i] = d;
        }
#if JD_FASTDECODE == 2
        { /* Create fast huffman decode table */
            unsigned int span, td, ti;
            uint16_t *tbl_ac = 0;
            uint8_t *tbl_dc = 0;

            if (cls) {
                tbl_ac = alloc_pool(jd, HUFF_LEN * sizeof(uint16_t)); /* LUT for AC elements */
                if (!tbl_ac)
                    return JDR_MEM1; /* Err: not enough memory */
                jd->hufflut_ac[num] = tbl_ac;
                memset(tbl_ac, 0xFF, HUFF_LEN * sizeof(uint16_t)); /* Default value (0xFFFF: may be long code) */
            } else {
                tbl_dc = alloc_pool(jd, HUFF_LEN * sizeof(uint8_t)); /* LUT for AC elements */
                if (!tbl_dc)
                    return JDR_MEM1; /* Err: not enough memory */
                jd->hufflut_dc[num] = tbl_dc;
                memset(tbl_dc, 0xFF, HUFF_LEN * sizeof(uint8_t)); /* Default value (0xFF: may be long code) */
            }
            for (i = b = 0; b < HUFF_BIT; b++) { /* Create LUT */
                for (j = pb[b]; j; j--) {
                    ti = ph[i] << (HUFF_BIT - 1 - b) & HUFF_MASK; /* Index of input pattern for the code */
                    if (cls) {
                        td = pd[i++] | ((b + 1) << 8); /* b15..b8: code length, b7..b0: zero run and data length */
                        for (span = 1 << (HUFF_BIT - 1 - b); span; span--, tbl_ac[ti++] = (uint16_t)td)
                            ;
                    } else {
                        td = pd[i++] | ((b + 1) << 4); /* b7..b4: code length, b3..b0: data length */
                        for (span = 1 << (HUFF_BIT - 1 - b); span; span--, tbl_dc[ti++] = (uint8_t)td)
                            ;
                    }
                }
            }
            jd->longofs[num][cls] = i; /* Code table offset for long code */
        }
#endif
    }

    return JDR_OK;
}

/*-----------------------------------------------------------------------*/
/* Extract a huffman decoded data from input stream                      */
/*-----------------------------------------------------------------------*/

static int huffext(                 /* >=0: decoded data, <0: error code */
                   JDEC *jd,        /* Pointer to the decompressor object */
                   unsigned int id, /* Table ID (0:Y, 1:C) */
                   unsigned int cls /* Table class (0:DC, 1:AC) */
)
{
    size_t dc = jd->dctr;
    uint8_t *dp = jd->dptr;
    unsigned int d, flg = 0;

#if JD_FASTDECODE == 0
    uint8_t bm, nd, bl;
    const uint8_t *hb = jd->huffbits[id][cls];  /* Bit distribution table */
    const uint16_t *hc = jd->huffcode[id][cls]; /* Code word table */
    const uint8_t *hd = jd->huffdata[id][cls];  /* Data table */

    bm = jd->dbit; /* Bit mask to extract */
    d = 0;
    bl = 16; /* Max code length */
    do {
        if (!bm) {              /* Next byte? */
            if (!dc) {          /* No input data is available, re-fill input buffer */
                dp = jd->inbuf; /* Top of input buffer */
                dc = jd->infunc(jd, dp, JD_SZBUF);
                if (!dc)
                    return 0 - (int)JDR_INP; /* Err: read error or wrong stream termination */
            } else {
                dp++; /* Next data ptr */
            }
            dc--;        /* Decrement number of available bytes */
            if (flg) {   /* In flag sequence? */
                flg = 0; /* Exit flag sequence */
                if (*dp != 0)
                    return 0 - (int)JDR_FMT1; /* Err: unexpected flag is detected (may be collapted data) */
                *dp = 0xFF;                   /* The flag is a data 0xFF */
            } else {
                if (*dp == 0xFF) { /* Is start of flag sequence? */
                    flg = 1;
                    continue; /* Enter flag sequence, get trailing byte */
                }
            }
            bm = 0x80; /* Read from MSB */
        }
        d <<= 1; /* Get a bit */
        if (*dp & bm)
            d++;
        bm >>= 1;

        for (nd = *hb++; nd; nd--) { /* Search the code word in this bit length */
            if (d == *hc++) {        /* Matched? */
                jd->dbit = bm;
                jd->dctr = dc;
                jd->dptr = dp;
                return *hd; /* Return the decoded data */
            }
            hd++;
        }
        bl--;
    } while (bl);

#else
    const uint8_t *hb, *hd;
    const uint16_t *hc;
    unsigned int nc, bl, wbit = jd->dbit % 32;
    uint32_t w = jd->wreg & ((1UL << wbit) - 1);

    while (wbit < 16) { /* Prepare 16 bits into the working register */
        if (jd->marker) {
            d = 0xFF; /* Input stream has stalled for a marker. Generate stuff bits */
        } else {
            if (!dc) {          /* Buffer empty, re-fill input buffer */
                dp = jd->inbuf; /* Top of input buffer */
                dc = jd->infunc(jd, dp, JD_SZBUF);
                if (!dc)
                    return 0 - (int)JDR_INP; /* Err: read error or wrong stream termination */
            }
            d = *dp++;
            dc--;
            if (flg) {   /* In flag sequence? */
                flg = 0; /* Exit flag sequence */
                if (d != 0)
                    jd->marker = d; /* Not an escape of 0xFF but a marker */
                d = 0xFF;
            } else {
                if (d == 0xFF) { /* Is start of flag sequence? */
                    flg = 1;
                    continue; /* Enter flag sequence, get trailing byte */
                }
            }
        }
        w = w << 8 | d; /* Shift 8 bits in the working register */
        wbit += 8;
    }
    jd->dctr = dc;
    jd->dptr = dp;
    jd->wreg = w;

#if JD_FASTDECODE == 2
    /* Table serch for the short codes */
    d = (unsigned int)(w >> (wbit - HUFF_BIT)); /* Short code as table index */
    if (cls) {                                  /* AC element */
        d = jd->hufflut_ac[id][d];              /* Table decode */
        if (d != 0xFFFF) {                      /* It is done if hit in short code */
            jd->dbit = wbit - (d >> 8);         /* Snip the code length */
            return d & 0xFF;                    /* b7..0: zero run and following data bits */
        }
    } else {                            /* DC element */
        d = jd->hufflut_dc[id][d];      /* Table decode */
        if (d != 0xFF) {                /* It is done if hit in short code */
            jd->dbit = wbit - (d >> 4); /* Snip the code length  */
            return d & 0xF;             /* b3..0: following data bits */
        }
    }

    /* Incremental serch for the codes longer than HUFF_BIT */
    hb = jd->huffbits[id][cls] + HUFF_BIT;             /* Bit distribution table */
    hc = jd->huffcode[id][cls] + jd->longofs[id][cls]; /* Code word table */
    hd = jd->huffdata[id][cls] + jd->longofs[id][cls]; /* Data table */
    bl = HUFF_BIT + 1;
#else
    /* Incremental serch for all codes */
    hb = jd->huffbits[id][cls]; /* Bit distribution table */
    hc = jd->huffcode[id][cls]; /* Code word table */
    hd = jd->huffdata[id][cls]; /* Data table */
    bl = 1;
#endif
    for (; bl <= 16; bl++) { /* Incremental search */
        nc = *hb++;
        if (nc) {
            d = w >> (wbit - bl);
            do {                          /* Search the code word in this bit length */
                if (d == *hc++) {         /* Matched? */
                    jd->dbit = wbit - bl; /* Snip the huffman code */
                    return *hd;           /* Return the decoded data */
                }
                hd++;
            } while (--nc);
        }
    }
#endif

    return 0 - (int)JDR_FMT1; /* Err: code not found (may be collapted data) */
}

/*-----------------------------------------------------------------------*/
/* Extract N bits from input stream                                      */
/*-----------------------------------------------------------------------*/

static int bitext(                  /* >=0: extracted data, <0: error code */
                  JDEC *jd,         /* Pointer to the decompressor object */
                  unsigned int nbit /* Number of bits to extract (1 to 16) */
)
{
    size_t dc = jd->dctr;
    uint8_t *dp = jd->dptr;
    unsigned int d, flg = 0;

#if JD_FASTDECODE == 0
    uint8_t mbit = jd->dbit;

    d = 0;
    do {
        if (!mbit) {            /* Next byte? */
            if (!dc) {          /* No input data is available, re-fill input buffer */
                dp = jd->inbuf; /* Top of input buffer */
                dc = jd->infunc(jd, dp, JD_SZBUF);
                if (!dc)
                    return 0 - (int)JDR_INP; /* Err: read error or wrong stream termination */
            } else {
                dp++; /* Next data ptr */
            }
            dc--;        /* Decrement number of available bytes */
            if (flg) {   /* In flag sequence? */
                flg = 0; /* Exit flag sequence */
                if (*dp != 0)
                    return 0 - (int)JDR_FMT1; /* Err: unexpected flag is detected (may be collapted data) */
                *dp = 0xFF;                   /* The flag is a data 0xFF */
            } else {
                if (*dp == 0xFF) { /* Is start of flag sequence? */
                    flg = 1;
                    continue; /* Enter flag sequence */
                }
            }
            mbit = 0x80; /* Read from MSB */
        }
        d <<= 1; /* Get a bit */
        if (*dp & mbit)
            d |= 1;
        mbit >>= 1;
        nbit--;
    } while (nbit);

    jd->dbit = mbit;
    jd->dctr = dc;
    jd->dptr = dp;
    return (int)d;

#else
    unsigned int wbit = jd->dbit % 32;
    uint32_t w = jd->wreg & ((1UL << wbit) - 1);

    while (wbit < nbit) { /* Prepare nbit bits into the working register */
        if (jd->marker) {
            d = 0xFF; /* Input stream stalled, generate stuff bits */
        } else {
            if (!dc) {          /* Buffer empty, re-fill input buffer */
                dp = jd->inbuf; /* Top of input buffer */
                dc = jd->infunc(jd, dp, JD_SZBUF);
                if (!dc)
                    return 0 - (int)JDR_INP; /* Err: read error or wrong stream termination */
            }
            d = *dp++;
            dc--;
            if (flg) {   /* In flag sequence? */
                flg = 0; /* Exit flag sequence */
                if (d != 0)
                    jd->marker = d; /* Not an escape of 0xFF but a marker */
                d = 0xFF;
            } else {
                if (d == 0xFF) { /* Is start of flag sequence? */
                    flg = 1;
                    continue; /* Enter flag sequence, get trailing byte */
                }
            }
        }
        w = w << 8 | d; /* Get 8 bits into the working register */
        wbit += 8;
    }
    jd->wreg = w;
    jd->dbit = wbit - nbit;
    jd->dctr = dc;
    jd->dptr = dp;

    return (int)(w >> ((wbit - nbit) % 32));
#endif
}

/*-----------------------------------------------------------------------*/
/* Process restart interval                                              */
/*-----------------------------------------------------------------------*/

static JRESULT restart(
    JDEC *jd,     /* Pointer to the decompressor object */
    uint16_t rstn /* Expected restert sequense number */
)
{
    unsigned int i;
    uint8_t *dp = jd->dptr;
    size_t dc = jd->dctr;

#if JD_FASTDECODE == 0
    uint16_t d = 0;

    /* Get two bytes from the input stream */
    for (i = 0; i < 2; i++) {
        if (!dc) { /* No input data is available, re-fill input buffer */
            dp = jd->inbuf;
            dc = jd->infunc(jd, dp, JD_SZBUF);
            if (!dc)
                return JDR_INP;
        } else {
            dp++;
        }
        dc--;
        d = d << 8 | *dp; /* Get a byte */
    }
    jd->dptr = dp;
    jd->dctr = dc;
    jd->dbit = 0;

    /* Check the marker */
    if ((d & 0xFFD8) != 0xFFD0 || (d & 7) != (rstn & 7)) {
        return JDR_FMT1; /* Err: expected RSTn marker is not detected (may be collapted data) */
    }

#else
    uint16_t marker;

    if (jd->marker) { /* Generate a maker if it has been detected */
        marker = 0xFF00 | jd->marker;
        jd->marker = 0;
    } else {
        marker = 0;
        for (i = 0; i < 2; i++) { /* Get a restart marker */
            if (!dc) {            /* No input data is available, re-fill input buffer */
                dp = jd->inbuf;
                dc = jd->infunc(jd, dp, JD_SZBUF);
                if (!dc)
                    return JDR_INP;
            }
            marker = (marker << 8) | *dp++; /* Get a byte */
            dc--;
        }
        jd->dptr = dp;
        jd->dctr = dc;
    }

    /* Check the marker */
    if ((marker & 0xFFD8) != 0xFFD0 || (marker & 7) != (rstn & 7)) {
        return JDR_FMT1; /* Err: expected RSTn marker was not detected (may be collapted data) */
    }

    jd->dbit = 0; /* Discard stuff bits */
#endif

    jd->dcv[2] = jd->dcv[1] = jd->dcv[0] = 0; /* Reset DC offset */
    return JDR_OK;
}

/*-----------------------------------------------------------------------*/
/* Apply Inverse-DCT in Arai Algorithm (see also aa_idct.png)            */
/*-----------------------------------------------------------------------*/

static void block_idct(
    int32_t *src, /* Input block data (de-quantized and pre-scaled for Arai Algorithm) */
    jd_yuv_t *dst /* Pointer to the destination to store the block as byte array */
)
{
    const int32_t M13 = (int32_t)(1.41421 * 4096), M2 = (int32_t)(1.08239 * 4096), M4 = (int32_t)(2.61313 * 4096), M5 = (int32_t)(1.84776 * 4096);
    int32_t v0, v1, v2, v3, v4, v5, v6, v7;
    int32_t t10, t11, t12, t13;
    int i;

    /* Process columns */
    for (i = 0; i < 8; i++) {
        v0 = src[8 * 0]; /* Get even elements */
        v1 = src[8 * 2];
        v2 = src[8 * 4];
        v3 = src[8 * 6];

        t10 = v0 + v2; /* Process the even elements */
        t12 = v0 - v2;
        t11 = (v1 - v3) * M13 >> 12;
        v3 += v1;
        t11 -= v3;
        v0 = t10 + v3;
        v3 = t10 - v3;
        v1 = t11 + t12;
        v2 = t12 - t11;

        v4 = src[8 * 7]; /* Get odd elements */
        v5 = src[8 * 1];
        v6 = src[8 * 5];
        v7 = src[8 * 3];

        t10 = v5 - v4; /* Process the odd elements */
        t11 = v5 + v4;
        t12 = v6 - v7;
        v7 += v6;
        v5 = (t11 - v7) * M13 >> 12;
        v7 += t11;
        t13 = (t10 + t12) * M5 >> 12;
        v4 = t13 - (t10 * M2 >> 12);
        v6 = t13 - (t12 * M4 >> 12) - v7;
        v5 -= v6;
        v4 -= v5;

        src[8 * 0] = v0 + v7; /* Write-back transformed values */
        src[8 * 7] = v0 - v7;
        src[8 * 1] = v1 + v6;
        src[8 * 6] = v1 - v6;
        src[8 * 2] = v2 + v5;
        src[8 * 5] = v2 - v5;
        src[8 * 3] = v3 + v4;
        src[8 * 4] = v3 - v4;

        src++; /* Next column */
    }

    /* Process rows */
    src -= 8;
    for (i = 0; i < 8; i++) {
        v0 = src[0] + (128L << 8); /* Get even elements (remove DC offset (-128) here) */
        v1 = src[2];
        v2 = src[4];
        v3 = src[6];

        t10 = v0 + v2; /* Process the even elements */
        t12 = v0 - v2;
        t11 = (v1 - v3) * M13 >> 12;
        v3 += v1;
        t11 -= v3;
        v0 = t10 + v3;
        v3 = t10 - v3;
        v1 = t11 + t12;
        v2 = t12 - t11;

        v4 = src[7]; /* Get odd elements */
        v5 = src[1];
        v6 = src[5];
        v7 = src[3];

        t10 = v5 - v4; /* Process the odd elements */
        t11 = v5 + v4;
        t12 = v6 - v7;
        v7 += v6;
        v5 = (t11 - v7) * M13 >> 12;
        v7 += t11;
        t13 = (t10 + t12) * M5 >> 12;
        v4 = t13 - (t10 * M2 >> 12);
        v6 = t13 - (t12 * M4 >> 12) - v7;
        v5 -= v6;
        v4 -= v5;

        /* Descale the transformed values 8 bits and output a row */
#if JD_FASTDECODE >= 1
        dst[0] = (int16_t)((v0 + v7) >> 8);
        dst[7] = (int16_t)((v0 - v7) >> 8);
        dst[1] = (int16_t)((v1 + v6) >> 8);
        dst[6] = (int16_t)((v1 - v6) >> 8);
        dst[2] = (int16_t)((v2 + v5) >> 8);
        dst[5] = (int16_t)((v2 - v5) >> 8);
        dst[3] = (int16_t)((v3 + v4) >> 8);
        dst[4] = (int16_t)((v3 - v4) >> 8);
#else
        dst[0] = BYTECLIP((v0 + v7) >> 8);
        dst[7] = BYTECLIP((v0 - v7) >> 8);
        dst[1] = BYTECLIP((v1 + v6) >> 8);
        dst[6] = BYTECLIP((v1 - v6) >> 8);
        dst[2] = BYTECLIP((v2 + v5) >> 8);
        dst[5] = BYTECLIP((v2 - v5) >> 8);
        dst[3] = BYTECLIP((v3 + v4) >> 8);
        dst[4] = BYTECLIP((v3 - v4) >> 8);
#endif

        dst += 8;
        src += 8; /* Next row */
    }
}

/*-----------------------------------------------------------------------*/
/* Load all blocks in an MCU into working buffer                         */
/*-----------------------------------------------------------------------*/

static JRESULT mcu_load(
    JDEC *jd /* Pointer to the decompressor object */
)
{
    int32_t *tmp = (int32_t *)jd->workbuf; /* Block working buffer for de-quantize and IDCT */
    int d, e;
    unsigned int blk, nby, i, bc, z, id, cmp;
    jd_yuv_t *bp;
    const int32_t *dqf;

    nby = jd->msx * jd->msy; /* Number of Y blocks (1, 2 or 4) */
    bp = jd->mcubuf;         /* Pointer to the first block of MCU */

    for (blk = 0; blk < nby + 2; blk++) {      /* Get nby Y blocks and two C blocks */
        cmp = (blk < nby) ? 0 : blk - nby + 1; /* Component number 0:Y, 1:Cb, 2:Cr */

        if (cmp && jd->ncomp != 3) { /* Clear C blocks if not exist (monochrome image) */
            for (i = 0; i < 64; bp[i++] = 128)
                ;

        } else {              /* Load Y/C blocks from input stream */
            id = cmp ? 1 : 0; /* Huffman table ID of this component */

            /* Extract a DC element from input stream */
            d = huffext(jd, id, 0); /* Extract a huffman coded data (bit length) */
            if (d < 0)
                return (JRESULT)(0 - d); /* Err: invalid code or input */
            bc = (unsigned int)d;
            d = jd->dcv[cmp];       /* DC value of previous block */
            if (bc) {               /* If there is any difference from previous block */
                e = bitext(jd, bc); /* Extract data bits */
                if (e < 0)
                    return (JRESULT)(0 - e); /* Err: input */
                bc = 1 << (bc - 1);          /* MSB position */
                if (!(e & bc))
                    e -= (bc << 1) - 1;    /* Restore negative value if needed */
                d += e;                    /* Get current value */
                jd->dcv[cmp] = (int16_t)d; /* Save current DC value for next block */
            }
            dqf = jd->qttbl[jd->qtid[cmp]]; /* De-quantizer table ID for this component */
            tmp[0] = d * dqf[0] >> 8;       /* De-quantize, apply scale factor of Arai algorithm and descale 8 bits */

            /* Extract following 63 AC elements from input stream */
            memset(&tmp[1], 0, 63 * sizeof(int32_t)); /* Initialize all AC elements */
            z = 1;                                    /* Top of the AC elements (in zigzag-order) */
            do {
                d = huffext(jd, id, 1); /* Extract a huffman coded value (zero runs and bit length) */
                if (d == 0)
                    break; /* EOB? */
                if (d < 0)
                    return (JRESULT)(0 - d); /* Err: invalid code or input error */
                bc = (unsigned int)d;
                z += bc >> 4; /* Skip leading zero run */
                if (z >= 64)
                    return JDR_FMT1;    /* Too long zero run */
                if (bc &= 0x0F) {       /* Bit length? */
                    d = bitext(jd, bc); /* Extract data bits */
                    if (d < 0)
                        return (JRESULT)(0 - d); /* Err: input device */
                    bc = 1 << (bc - 1);          /* MSB position */
                    if (!(d & bc))
                        d -= (bc << 1) - 1;   /* Restore negative value if needed */
                    i = Zig[z];               /* Get raster-order index */
                    tmp[i] = d * dqf[i] >> 8; /* De-quantize, apply scale factor of Arai algorithm and descale 8 bits */
                }
            } while (++z < 64); /* Next AC element */

            if (JD_FORMAT != 2 || !cmp) {                         /* C components may not be processed if in grayscale output */
                if (z == 1 || (JD_USE_SCALE && jd->scale == 3)) { /* If no AC element or scale ratio is 1/8, IDCT can be ommited and the block is filled with DC value */
                    d = (jd_yuv_t)((*tmp / 256) + 128);
                    if (JD_FASTDECODE >= 1) {
                        for (i = 0; i < 64; bp[i++] = d)
                            ;
                    } else {
                        memset(bp, d, 64);
                    }
                } else {
                    block_idct(tmp, bp); /* Apply IDCT and store the block to the MCU buffer */
                }
            }
        }

        bp += 64; /* Next block */
    }

    return JDR_OK; /* All blocks have been loaded successfully */
}

/*-----------------------------------------------------------------------*/
/* Output an MCU: Convert YCrCb to RGB and output it in RGB form         */
/*-----------------------------------------------------------------------*/

static JRESULT mcu_output(
    JDEC *jd,                                /* Pointer to the decompressor object */
    int (*outfunc)(JDEC *, void *, JRECT *), /* RGB output function */
    unsigned int x,                          /* MCU location in the image */
    unsigned int y                           /* MCU location in the image */
)
{
    const int CVACC = (sizeof(int) > 2) ? 1024 : 128; /* Adaptive accuracy for both 16-/32-bit systems */
    unsigned int ix, iy, mx, my, rx, ry;
    int yy, cb, cr;
    jd_yuv_t *py, *pc;
    uint8_t *pix;
    JRECT rect;

    mx = jd->msx * 8;
    my = jd->msy * 8;                                /* MCU size (pixel) */
    rx = (x + mx <= jd->width) ? mx : jd->width - x; /* Output rectangular size (it may be clipped at right/bottom end of image) */
    ry = (y + my <= jd->height) ? my : jd->height - y;
    if (JD_USE_SCALE) {
        rx >>= jd->scale;
        ry >>= jd->scale;
        if (!rx || !ry)
            return JDR_OK; /* Skip this MCU if all pixel is to be rounded off */
        x >>= jd->scale;
        y >>= jd->scale;
    }
    rect.left = x;
    rect.right = x + rx - 1; /* Rectangular area in the frame buffer */
    rect.top = y;
    rect.bottom = y + ry - 1;

    if (!JD_USE_SCALE || jd->scale != 3) { /* Not for 1/8 scaling */
        pix = (uint8_t *)jd->workbuf;

        if (JD_FORMAT != 2) { /* RGB output (build an RGB MCU from Y/C component) */
            for (iy = 0; iy < my; iy++) {
                pc = py = jd->mcubuf;
                if (my == 16) { /* Double block height? */
                    pc += 64 * 4 + (iy >> 1) * 8;
                    if (iy >= 8)
                        py += 64;
                } else { /* Single block height */
                    pc += mx * 8 + iy * 8;
                }
                py += iy * 8;
                for (ix = 0; ix < mx; ix++) {
                    cb = pc[0] - 128; /* Get Cb/Cr component and remove offset */
                    cr = pc[64] - 128;
                    if (mx == 16) { /* Double block width? */
                        if (ix == 8)
                            py += 64 - 8; /* Jump to next block if double block heigt */
                        pc += ix & 1;     /* Step forward chroma pointer every two pixels */
                    } else {              /* Single block width */
                        pc++;             /* Step forward chroma pointer every pixel */
                    }
                    yy = *py++; /* Get Y component */
                    *pix++ = /*R*/ BYTECLIP(yy + ((int)(1.402 * CVACC) * cr) / CVACC);
                    *pix++ = /*G*/ BYTECLIP(yy - ((int)(0.344 * CVACC) * cb + (int)(0.714 * CVACC) * cr) / CVACC);
                    *pix++ = /*B*/ BYTECLIP(yy + ((int)(1.772 * CVACC) * cb) / CVACC);
                }
            }
        } else { /* Monochrome output (build a grayscale MCU from Y comopnent) */
            for (iy = 0; iy < my; iy++) {
                py = jd->mcubuf + iy * 8;
                if (my == 16) { /* Double block height? */
                    if (iy >= 8)
                        py += 64;
                }
                for (ix = 0; ix < mx; ix++) {
                    if (mx == 16) { /* Double block width? */
                        if (ix == 8)
                            py += 64 - 8; /* Jump to next block if double block height */
                    }
                    *pix++ = (uint8_t)*py++; /* Get and store a Y value as grayscale */
                }
            }
        }

        /* Descale the MCU rectangular if needed */
        if (JD_USE_SCALE && jd->scale) {
            unsigned int x, y, r, g, b, s, w, a;
            uint8_t *op;

            /* Get averaged RGB value of each square correcponds to a pixel */
            s = jd->scale * 2;                       /* Number of shifts for averaging */
            w = 1 << jd->scale;                      /* Width of square */
            a = (mx - w) * (JD_FORMAT != 2 ? 3 : 1); /* Bytes to skip for next line in the square */
            op = (uint8_t *)jd->workbuf;
            for (iy = 0; iy < my; iy += w) {
                for (ix = 0; ix < mx; ix += w) {
                    pix = (uint8_t *)jd->workbuf + (iy * mx + ix) * (JD_FORMAT != 2 ? 3 : 1);
                    r = g = b = 0;
                    for (y = 0; y < w; y++) { /* Accumulate RGB value in the square */
                        for (x = 0; x < w; x++) {
                            r += *pix++;          /* Accumulate R or Y (monochrome output) */
                            if (JD_FORMAT != 2) { /* RGB output? */
                                g += *pix++;      /* Accumulate G */
                                b += *pix++;      /* Accumulate B */
                            }
                        }
                        pix += a;
                    }                              /* Put the averaged pixel value */
                    *op++ = (uint8_t)(r >> s);     /* Put R or Y (monochrome output) */
                    if (JD_FORMAT != 2) {          /* RGB output? */
                        *op++ = (uint8_t)(g >> s); /* Put G */
                        *op++ = (uint8_t)(b >> s); /* Put B */
                    }
                }
            }
        }

    } else { /* For only 1/8 scaling (left-top pixel in each block are the DC value of the block) */

        /* Build a 1/8 descaled RGB MCU from discrete comopnents */
        pix = (uint8_t *)jd->workbuf;
        pc = jd->mcubuf + mx * my;
        cb = pc[0] - 128; /* Get Cb/Cr component and restore right level */
        cr = pc[64] - 128;
        for (iy = 0; iy < my; iy += 8) {
            py = jd->mcubuf;
            if (iy == 8)
                py += 64 * 2;
            for (ix = 0; ix < mx; ix += 8) {
                yy = *py; /* Get Y component */
                py += 64;
                if (JD_FORMAT != 2) {
                    *pix++ = /*R*/ BYTECLIP(yy + ((int)(1.402 * CVACC) * cr / CVACC));
                    *pix++ = /*G*/ BYTECLIP(yy - ((int)(0.344 * CVACC) * cb + (int)(0.714 * CVACC) * cr) / CVACC);
                    *pix++ = /*B*/ BYTECLIP(yy + ((int)(1.772 * CVACC) * cb / CVACC));
                } else {
                    *pix++ = yy;
                }
            }
        }
    }

    /* Squeeze up pixel table if a part of MCU is to be truncated */
    mx >>= jd->scale;
    if (rx < mx) { /* Is the MCU spans rigit edge? */
        uint8_t *s, *d;
        unsigned int x, y;

        s = d = (uint8_t *)jd->workbuf;
        for (y = 0; y < ry; y++) {
            for (x = 0; x < rx; x++) { /* Copy effective pixels */
                *d++ = *s++;
                if (JD_FORMAT != 2) {
                    *d++ = *s++;
                    *d++ = *s++;
                }
            }
            s += (mx - rx) * (JD_FORMAT != 2 ? 3 : 1); /* Skip truncated pixels */
        }
    }

    /* Convert RGB888 to RGB565 if needed */
    if (JD_FORMAT == 1) {
        uint8_t *s = (uint8_t *)jd->workbuf;
        uint16_t w, *d = (uint16_t *)s;
        unsigned int n = rx * ry;

        do {
            w = (*s++ & 0xF8) << 8;  /* RRRRR----------- */
            w |= (*s++ & 0xFC) << 3; /* -----GGGGGG----- */
            w |= *s++ >> 3;          /* -----------BBBBB */
            *d++ = w;
        } while (--n);
    }

    /* Output the rectangular */
    return outfunc(jd, jd->workbuf, &rect) ? JDR_OK : JDR_INTR;
}

/*-----------------------------------------------------------------------*/
/* Analyze the JPEG image and Initialize decompressor object             */
/*-----------------------------------------------------------------------*/

#define LDB_WORD(ptr) (uint16_t)(((uint16_t) * ((uint8_t *)(ptr)) << 8) | (uint16_t) * (uint8_t *)((ptr) + 1))

JRESULT jd_prepare(
    JDEC *jd,                                    /* Blank decompressor object */
    size_t (*infunc)(JDEC *, uint8_t *, size_t), /* JPEG strem input function */
    void *pool,                                  /* Working buffer for the decompression session */
    size_t sz_pool,                              /* Size of working buffer */
    void *dev                                    /* I/O device identifier for the session */
)
{
    uint8_t *seg, b;
    uint16_t marker;
    unsigned int n, i, ofs;
    size_t len;
    JRESULT rc;

    memset(jd, 0, sizeof(JDEC)); /* Clear decompression object (this might be a problem if machine's null pointer is not all bits zero) */
    jd->pool = pool;             /* Work memroy */
    jd->sz_pool = sz_pool;       /* Size of given work memory */
    jd->infunc = infunc;         /* Stream input function */
    jd->device = dev;            /* I/O device identifier */

    jd->inbuf = seg = alloc_pool(jd, JD_SZBUF); /* Allocate stream input buffer */
    if (!seg)
        return JDR_MEM1;

    ofs = marker = 0; /* Find SOI marker */
    do {
        if (jd->infunc(jd, seg, 1) != 1)
            return JDR_INP; /* Err: SOI was not detected */
        ofs++;
        marker = marker << 8 | seg[0];
    } while (marker != 0xFFD8);

    for (;;) { /* Parse JPEG segments */
        /* Get a JPEG marker */
        if (jd->infunc(jd, seg, 4) != 4)
            return JDR_INP;
        marker = LDB_WORD(seg);  /* Marker */
        len = LDB_WORD(seg + 2); /* Length field */
        if (len <= 2 || (marker >> 8) != 0xFF)
            return JDR_FMT1;
        len -= 2;       /* Segent content size */
        ofs += 4 + len; /* Number of bytes loaded */

        switch (marker & 0xFF) {
            case 0xC0: /* SOF0 (baseline JPEG) */
                if (len > JD_SZBUF)
                    return JDR_MEM2;
                if (jd->infunc(jd, seg, len) != len)
                    return JDR_INP; /* Load segment data */

                jd->width = LDB_WORD(&seg[3]);  /* Image width in unit of pixel */
                jd->height = LDB_WORD(&seg[1]); /* Image height in unit of pixel */
                jd->ncomp = seg[5];             /* Number of color components */
                if (jd->ncomp != 3 && jd->ncomp != 1)
                    return JDR_FMT3; /* Err: Supports only Grayscale and Y/Cb/Cr */

                /* Check each image component */
                for (i = 0; i < jd->ncomp; i++) {
                    b = seg[7 + 3 * i];                            /* Get sampling factor */
                    if (i == 0) {                                  /* Y component */
                        if (b != 0x11 && b != 0x22 && b != 0x21) { /* Check sampling factor */
                            return JDR_FMT3;                       /* Err: Supports only 4:4:4, 4:2:0 or 4:2:2 */
                        }
                        jd->msx = b >> 4;
                        jd->msy = b & 15; /* Size of MCU [blocks] */
                    } else {              /* Cb/Cr component */
                        if (b != 0x11)
                            return JDR_FMT3; /* Err: Sampling factor of Cb/Cr must be 1 */
                    }
                    jd->qtid[i] = seg[8 + 3 * i]; /* Get dequantizer table ID for this component */
                    if (jd->qtid[i] > 3)
                        return JDR_FMT3; /* Err: Invalid ID */
                }
                break;

            case 0xDD: /* DRI - Define Restart Interval */
                if (len > JD_SZBUF)
                    return JDR_MEM2;
                if (jd->infunc(jd, seg, len) != len)
                    return JDR_INP; /* Load segment data */

                jd->nrst = LDB_WORD(seg); /* Get restart interval (MCUs) */
                break;

            case 0xC4: /* DHT - Define Huffman Tables */
                if (len > JD_SZBUF)
                    return JDR_MEM2;
                if (jd->infunc(jd, seg, len) != len)
                    return JDR_INP; /* Load segment data */

                rc = create_huffman_tbl(jd, seg, len); /* Create huffman tables */
                if (rc)
                    return rc;
                break;

            case 0xDB: /* DQT - Define Quaitizer Tables */
                if (len > JD_SZBUF)
                    return JDR_MEM2;
                if (jd->infunc(jd, seg, len) != len)
                    return JDR_INP; /* Load segment data */

                rc = create_qt_tbl(jd, seg, len); /* Create de-quantizer tables */
                if (rc)
                    return rc;
                break;

            case 0xDA: /* SOS - Start of Scan */
                if (len > JD_SZBUF)
                    return JDR_MEM2;
                if (jd->infunc(jd, seg, len) != len)
                    return JDR_INP; /* Load segment data */

                if (!jd->width || !jd->height)
                    return JDR_FMT1; /* Err: Invalid image size */
                if (seg[0] != jd->ncomp)
                    return JDR_FMT3; /* Err: Wrong color components */

                /* Check if all tables corresponding to each components have been loaded */
                for (i = 0; i < jd->ncomp; i++) {
                    b = seg[2 + 2 * i]; /* Get huffman table ID */
                    if (b != 0x00 && b != 0x11)
                        return JDR_FMT3;                              /* Err: Different table number for DC/AC element */
                    n = i ? 1 : 0;                                    /* Component class */
                    if (!jd->huffbits[n][0] || !jd->huffbits[n][1]) { /* Check huffman table for this component */
                        return JDR_FMT1;                              /* Err: Nnot loaded */
                    }
                    if (!jd->qttbl[jd->qtid[i]]) { /* Check dequantizer table for this component */
                        return JDR_FMT1;           /* Err: Not loaded */
                    }
                }

                /* Allocate working buffer for MCU and pixel output */
                n = jd->msy * jd->msx; /* Number of Y blocks in the MCU */
                if (!n)
                    return JDR_FMT1;   /* Err: SOF0 has not been loaded */
                len = n * 64 * 2 + 64; /* Allocate buffer for IDCT and RGB output */
                if (len < 256)
                    len = 256;                     /* but at least 256 byte is required for IDCT */
                jd->workbuf = alloc_pool(jd, len); /* and it may occupy a part of following MCU working buffer for RGB output */
                if (!jd->workbuf)
                    return JDR_MEM1;                                          /* Err: not enough memory */
                jd->mcubuf = alloc_pool(jd, (n + 2) * 64 * sizeof(jd_yuv_t)); /* Allocate MCU working buffer */
                if (!jd->mcubuf)
                    return JDR_MEM1; /* Err: not enough memory */

                /* Align stream read offset to JD_SZBUF */
                if (ofs %= JD_SZBUF) {
                    jd->dctr = jd->infunc(jd, seg + ofs, (size_t)(JD_SZBUF - ofs));
                }
                jd->dptr = seg + ofs - (JD_FASTDECODE ? 0 : 1);

                return JDR_OK; /* Initialization succeeded. Ready to decompress the JPEG image. */

            case 0xC1:           /* SOF1 */
            case 0xC2:           /* SOF2 */
            case 0xC3:           /* SOF3 */
            case 0xC5:           /* SOF5 */
            case 0xC6:           /* SOF6 */
            case 0xC7:           /* SOF7 */
            case 0xC9:           /* SOF9 */
            case 0xCA:           /* SOF10 */
            case 0xCB:           /* SOF11 */
            case 0xCD:           /* SOF13 */
            case 0xCE:           /* SOF14 */
            case 0xCF:           /* SOF15 */
            case 0xD9:           /* EOI */
                return JDR_FMT3; /* Unsuppoted JPEG standard (may be progressive JPEG) */

            default: /* Unknown segment (comment, exif or etc..) */
                /* Skip segment data (null pointer specifies to remove data from the stream) */
                if (jd->infunc(jd, 0, len) != len)
                    return JDR_INP;
        }
    }
}

/*-----------------------------------------------------------------------*/
/* Start to decompress the JPEG picture                                  */
/*-----------------------------------------------------------------------*/

JRESULT jd_decomp(
    JDEC *jd,                                /* Initialized decompression object */
    int (*outfunc)(JDEC *, void *, JRECT *), /* RGB output function */
    uint8_t scale                            /* Output de-scaling factor (0 to 3) */
)
{
    unsigned int x, y, mx, my;
    uint16_t rst, rsc;
    JRESULT rc;

    if (scale > (JD_USE_SCALE ? 3 : 0))
        return JDR_PAR;
    jd->scale = scale;

    mx = jd->msx * 8;
    my = jd->msy * 8; /* Size of the MCU (pixel) */

    jd->dcv[2] = jd->dcv[1] = jd->dcv[0] = 0; /* Initialize DC values */
    rst = rsc = 0;

    rc = JDR_OK;
    for (y = 0; y < jd->height; y += my) {       /* Vertical loop of MCUs */
        for (x = 0; x < jd->width; x += mx) {    /* Horizontal loop of MCUs */
            if (jd->nrst && rst++ == jd->nrst) { /* Process restart interval if enabled */
                rc = restart(jd, rsc++);
                if (rc != JDR_OK)
                    return rc;
                rst = 1;
            }
            rc = mcu_load(jd); /* Load an MCU (decompress huffman coded stream, dequantize and apply IDCT) */
            if (rc != JDR_OK)
                return rc;
            rc = mcu_output(jd, outfunc, x, y); /* Output the MCU (YCbCr to RGB, scaling and output) */
            if (rc != JDR_OK)
                return rc;
        }
    }

    return rc;
}
