/* Bit operations.
 *
 * Copyright (c) 2009-2012, Redis Ltd.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *   * Neither the name of Redis nor the names of its contributors may be used
 *     to endorse or promote products derived from this software without
 *     specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "server.h"
#if HAVE_X86_SIMD
/* Define __MM_MALLOC_H to prevent importing the memory aligned
 * allocation functions, which we don't use. */
#define __MM_MALLOC_H
#include <immintrin.h>
#endif
#if HAVE_ARM_NEON
#include <arm_neon.h>
#endif
/* -----------------------------------------------------------------------------
 * Helpers and low level bit functions.
 * -------------------------------------------------------------------------- */

static const unsigned char bitsinbyte[256] = {
    0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 1, 2, 2, 3, 2,
    3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3,
    3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5,
    6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4,
    3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4,
    5, 5, 6, 5, 6, 6, 7, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6,
    6, 7, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8};

#if HAVE_X86_SIMD
/* The SIMD version of popcount enhances performance through parallel lookup tables which is based on the following article:
 * https://arxiv.org/pdf/1611.07612 */
ATTRIBUTE_TARGET_AVX2
long long popcountAVX2(void *s, long count) {
    long i = 0;
    unsigned char *p = (unsigned char *)s;
    long long bits = 0;

    /* clang-format off */
    const __m256i lookup = _mm256_setr_epi8(
        /* First Lane [0:127] */
        /* 0 */ 0, /* 1 */ 1, /* 2 */ 1, /* 3 */ 2,
        /* 4 */ 1, /* 5 */ 2, /* 6 */ 2, /* 7 */ 3,
        /* 8 */ 1, /* 9 */ 2, /* a */ 2, /* b */ 3,
        /* c */ 2, /* d */ 3, /* e */ 3, /* f */ 4,

        /* Second Lane [128:255] identical to first lane due to lane isolation in _mm256_shuffle_epi8.
         * For more information, see following URL
         * https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_mm256_shuffle_epi8 */
        /* 0 */ 0, /* 1 */ 1, /* 2 */ 1, /* 3 */ 2,
        /* 4 */ 1, /* 5 */ 2, /* 6 */ 2, /* 7 */ 3,
        /* 8 */ 1, /* 9 */ 2, /* a */ 2, /* b */ 3,
        /* c */ 2, /* d */ 3, /* e */ 3, /* f */ 4);
    /* clang-format on */
    const __m256i low_mask = _mm256_set1_epi8(0x0f);
    __m256i acc = _mm256_setzero_si256();

/* Count 32 bytes per iteration. */
#define ITER_32_BYTES                                                             \
    {                                                                             \
        const __m256i vec = _mm256_loadu_si256((const __m256i *)(p + i));         \
        const __m256i lo = _mm256_and_si256(vec, low_mask);                       \
        const __m256i hi = _mm256_and_si256(_mm256_srli_epi16(vec, 4), low_mask); \
        const __m256i popcnt1 = _mm256_shuffle_epi8(lookup, lo);                  \
        const __m256i popcnt2 = _mm256_shuffle_epi8(lookup, hi);                  \
        local = _mm256_add_epi8(local, popcnt1);                                  \
        local = _mm256_add_epi8(local, popcnt2);                                  \
        i += 32;                                                                  \
    }

    /* We divide the array into the following three parts
     *        Part A         Part B       Part C
     * +-----------------+--------------+---------+
     * | 8 * 32bytes * X |  32bytes * Y | Z bytes |
     * +-----------------+--------------+---------+
     */

    /* Part A: loop unrolling, processing 8 * 32 bytes per iteration. */
    while (i + 8 * 32 <= count) {
        __m256i local = _mm256_setzero_si256();
        ITER_32_BYTES
        ITER_32_BYTES
        ITER_32_BYTES
        ITER_32_BYTES
        ITER_32_BYTES
        ITER_32_BYTES
        ITER_32_BYTES
        ITER_32_BYTES
        acc = _mm256_add_epi64(acc, _mm256_sad_epu8(local, _mm256_setzero_si256()));
    }

    /* Part B: when the remaining data length is less than 8 * 32 bytes,
     * process 32 bytes per iteration. */
    __m256i local = _mm256_setzero_si256();
    while (i + 32 <= count) {
        ITER_32_BYTES;
    }
    acc = _mm256_add_epi64(acc, _mm256_sad_epu8(local, _mm256_setzero_si256()));

#undef ITER_32_BYTES

    bits += _mm256_extract_epi64(acc, 0);
    bits += _mm256_extract_epi64(acc, 1);
    bits += _mm256_extract_epi64(acc, 2);
    bits += _mm256_extract_epi64(acc, 3);

    /* Part C: count the remaining bytes. */
    for (; i < count; i++) {
        bits += bitsinbyte[p[i]];
    }

    return bits;
}
#endif

/* The scalar version of popcount based on lookup tables. */
long long popcountScalar(void *s, long count) {
    long long bits = 0;
    unsigned char *p = s;
    uint32_t *p4;

    /* Count initial bytes not aligned to 32 bit. */
    while ((unsigned long)p & 3 && count) {
        bits += bitsinbyte[*p++];
        count--;
    }

    /* Count bits 28 bytes at a time */
    p4 = (uint32_t *)p;
    while (count >= 28) {
        uint32_t aux1, aux2, aux3, aux4, aux5, aux6, aux7;

        aux1 = *p4++;
        aux2 = *p4++;
        aux3 = *p4++;
        aux4 = *p4++;
        aux5 = *p4++;
        aux6 = *p4++;
        aux7 = *p4++;
        count -= 28;

        aux1 = aux1 - ((aux1 >> 1) & 0x55555555);
        aux1 = (aux1 & 0x33333333) + ((aux1 >> 2) & 0x33333333);
        aux2 = aux2 - ((aux2 >> 1) & 0x55555555);
        aux2 = (aux2 & 0x33333333) + ((aux2 >> 2) & 0x33333333);
        aux3 = aux3 - ((aux3 >> 1) & 0x55555555);
        aux3 = (aux3 & 0x33333333) + ((aux3 >> 2) & 0x33333333);
        aux4 = aux4 - ((aux4 >> 1) & 0x55555555);
        aux4 = (aux4 & 0x33333333) + ((aux4 >> 2) & 0x33333333);
        aux5 = aux5 - ((aux5 >> 1) & 0x55555555);
        aux5 = (aux5 & 0x33333333) + ((aux5 >> 2) & 0x33333333);
        aux6 = aux6 - ((aux6 >> 1) & 0x55555555);
        aux6 = (aux6 & 0x33333333) + ((aux6 >> 2) & 0x33333333);
        aux7 = aux7 - ((aux7 >> 1) & 0x55555555);
        aux7 = (aux7 & 0x33333333) + ((aux7 >> 2) & 0x33333333);
        bits += ((((aux1 + (aux1 >> 4)) & 0x0F0F0F0F) + ((aux2 + (aux2 >> 4)) & 0x0F0F0F0F) +
                  ((aux3 + (aux3 >> 4)) & 0x0F0F0F0F) + ((aux4 + (aux4 >> 4)) & 0x0F0F0F0F) +
                  ((aux5 + (aux5 >> 4)) & 0x0F0F0F0F) + ((aux6 + (aux6 >> 4)) & 0x0F0F0F0F) +
                  ((aux7 + (aux7 >> 4)) & 0x0F0F0F0F)) *
                 0x01010101) >>
                24;
    }
    /* Count the remaining bytes. */
    p = (unsigned char *)p4;
    while (count--) bits += bitsinbyte[*p++];
    return bits;
}

#if HAVE_ARM_NEON
#include <arm_neon.h>

/*  SIMD version of popcount for ARM NEON.
 *  Processes data in 64-byte NEON batches, falls back to scalar for tail. */
long long popcountNEON(void *s, long n) {
    long long t = 0;
    uint8_t *p = (uint8_t *)s;
    ;
    const uint8_t *e = p + n;

    /* Process 64-byte blocks using unrolled loop (4 x 16-byte vectors) */
    for (; p <= e - 64; p += 64) {
        /* Load 4 vector registers (16 bytes each) */
        uint8x16_t v0 = vld1q_u8(p);
        uint8x16_t v1 = vld1q_u8(p + 16);
        uint8x16_t v2 = vld1q_u8(p + 32);
        uint8x16_t v3 = vld1q_u8(p + 48);

        /* Count bits in each byte and sum vectors */
        uint8x16_t s1 = vaddq_u8(vcntq_u8(v0), vcntq_u8(v1));
        uint8x16_t s2 = vaddq_u8(vcntq_u8(v2), vcntq_u8(v3));
        uint8x16_t s0 = vaddq_u8(s1, s2);

        /* Sum all bytes in the final vector */
        uint16x8_t sc = vpaddlq_u8(s0); // 16x u8 -> 8x u16 (pairwise add)
        uint32_t t1 = vaddvq_u16(sc);
        t += t1;
    }

    /* Process remaining 16-byte chunks */
    for (; p + 16 <= e; p += 16) {
        t += vaddvq_u8(vcntq_u8(vld1q_u8(p)));
    }

    /* Handle remaining bytes with scalar fallback */
    if (p < e) {
        size_t r = e - p;
        t += popcountScalar((void *)p, r);
    }

    return t;
}
#endif

/* Count number of bits set in the binary array pointed by 's' and long
 * 'count' bytes. The implementation of this function is required to
 * work with an input string length up to 512 MB or more (server.proto_max_bulk_len) */
long long serverPopcount(void *s, long count) {
#if HAVE_X86_SIMD
    /* If length of s >= 256 bits and the CPU supports AVX2,
     * we prefer to use the SIMD version */
    if (count >= 32 && __builtin_cpu_supports("avx2")) {
        return popcountAVX2(s, count);
    }
#endif
#ifdef __aarch64__
    if (count >= 16) {
        return popcountNEON(s, count);
    }
#endif

    return popcountScalar(s, count);
}

/* Return the position of the first bit set to one (if 'bit' is 1) or
 * zero (if 'bit' is 0) in the bitmap starting at 's' and long 'count' bytes.
 *
 * The function is guaranteed to return a value >= 0 if 'bit' is 0 since if
 * no zero bit is found, it returns count*8 assuming the string is zero
 * padded on the right. However if 'bit' is 1 it is possible that there is
 * not a single set bit in the bitmap. In this special case -1 is returned. */
long long serverBitpos(void *s, unsigned long count, int bit) {
    unsigned long *l;
    unsigned char *c;
    unsigned long skipval, word = 0, one;
    long long pos = 0; /* Position of bit, to return to the caller. */
    unsigned long j;
    int found;

    /* Process whole words first, seeking for first word that is not
     * all ones or all zeros respectively if we are looking for zeros
     * or ones. This is much faster with large strings having contiguous
     * blocks of 1 or 0 bits compared to the vanilla bit per bit processing.
     *
     * Note that if we start from an address that is not aligned
     * to sizeof(unsigned long) we consume it byte by byte until it is
     * aligned. */

    /* Skip initial bits not aligned to sizeof(unsigned long) byte by byte. */
    skipval = bit ? 0 : UCHAR_MAX;
    c = (unsigned char *)s;
    found = 0;
    while ((unsigned long)c & (sizeof(*l) - 1) && count) {
        if (*c != skipval) {
            found = 1;
            break;
        }
        c++;
        count--;
        pos += 8;
    }

    /* Skip bits with full word step. */
    l = (unsigned long *)c;
    if (!found) {
        skipval = bit ? 0 : ULONG_MAX;
        while (count >= sizeof(*l)) {
            if (*l != skipval) break;
            l++;
            count -= sizeof(*l);
            pos += sizeof(*l) * 8;
        }
    }

    /* Load bytes into "word" considering the first byte as the most significant
     * (we basically consider it as written in big endian, since we consider the
     * string as a set of bits from left to right, with the first bit at position
     * zero.
     *
     * Note that the loading is designed to work even when the bytes left
     * (count) are less than a full word. We pad it with zero on the right. */
    c = (unsigned char *)l;
    for (j = 0; j < sizeof(*l); j++) {
        word <<= 8;
        if (count) {
            word |= *c;
            c++;
            count--;
        }
    }

    /* Special case:
     * If bits in the string are all zero and we are looking for one,
     * return -1 to signal that there is not a single "1" in the whole
     * string. This can't happen when we are looking for "0" as we assume
     * that the right of the string is zero padded. */
    if (bit == 1 && word == 0) return -1;

    /* Last word left, scan bit by bit. The first thing we need is to
     * have a single "1" set in the most significant position in an
     * unsigned long. We don't know the size of the long so we use a
     * simple trick. */
    one = ULONG_MAX; /* All bits set to 1.*/
    one >>= 1;       /* All bits set to 1 but the MSB. */
    one = ~one;      /* All bits set to 0 but the MSB. */

    while (one) {
        if (((one & word) != 0) == bit) return pos;
        pos++;
        one >>= 1;
    }

    /* If we reached this point, there is a bug in the algorithm, since
     * the case of no match is handled as a special case before. */
    serverPanic("End of serverBitpos() reached.");
    return 0; /* Just to avoid warnings. */
}

/* The following set.*Bitfield and get.*Bitfield functions implement setting
 * and getting arbitrary size (up to 64 bits) signed and unsigned integers
 * at arbitrary positions into a bitmap.
 *
 * The representation considers the bitmap as having the bit number 0 to be
 * the most significant bit of the first byte, and so forth, so for example
 * setting a 5 bits unsigned integer to value 23 at offset 7 into a bitmap
 * previously set to all zeroes, will produce the following representation:
 *
 * +--------+--------+
 * |00000001|01110000|
 * +--------+--------+
 *
 * When offsets and integer sizes are aligned to bytes boundaries, this is the
 * same as big endian, however when such alignment does not exist, its important
 * to also understand how the bits inside a byte are ordered.
 *
 * Note that this format follows the same convention as SETBIT and related
 * commands.
 */

void setUnsignedBitfield(unsigned char *p, uint64_t offset, uint64_t bits, uint64_t value) {
    uint64_t byte, bit, byteval, bitval, j;

    for (j = 0; j < bits; j++) {
        bitval = (value & ((uint64_t)1 << (bits - 1 - j))) != 0;
        byte = offset >> 3;
        bit = 7 - (offset & 0x7);
        byteval = p[byte];
        byteval &= ~(1 << bit);
        byteval |= bitval << bit;
        p[byte] = byteval & 0xff;
        offset++;
    }
}

void setSignedBitfield(unsigned char *p, uint64_t offset, uint64_t bits, int64_t value) {
    uint64_t uv = value; /* Casting will add UINT64_MAX + 1 if v is negative. */
    setUnsignedBitfield(p, offset, bits, uv);
}

uint64_t getUnsignedBitfield(unsigned char *p, uint64_t offset, uint64_t bits) {
    uint64_t byte, bit, byteval, bitval, j, value = 0;

    for (j = 0; j < bits; j++) {
        byte = offset >> 3;
        bit = 7 - (offset & 0x7);
        byteval = p[byte];
        bitval = (byteval >> bit) & 1;
        value = (value << 1) | bitval;
        offset++;
    }
    return value;
}

int64_t getSignedBitfield(unsigned char *p, uint64_t offset, uint64_t bits) {
    int64_t value;
    union {
        uint64_t u;
        int64_t i;
    } conv;

    /* Converting from unsigned to signed is undefined when the value does
     * not fit, however here we assume two's complement and the original value
     * was obtained from signed -> unsigned conversion, so we'll find the
     * most significant bit set if the original value was negative.
     *
     * Note that two's complement is mandatory for exact-width types
     * according to the C99 standard. */
    conv.u = getUnsignedBitfield(p, offset, bits);
    value = conv.i;

    /* If the top significant bit is 1, propagate it to all the
     * higher bits for two's complement representation of signed
     * integers. */
    if (bits < 64 && (value & ((uint64_t)1 << (bits - 1)))) value |= ((uint64_t)-1) << bits;
    return value;
}

/* The following two functions detect overflow of a value in the context
 * of storing it as an unsigned or signed integer with the specified
 * number of bits. The functions both take the value and a possible increment.
 * If no overflow could happen and the value+increment fit inside the limits,
 * then zero is returned, otherwise in case of overflow, 1 is returned,
 * otherwise in case of underflow, -1 is returned.
 *
 * When non-zero is returned (overflow or underflow), if not NULL, *limit is
 * set to the value the operation should result when an overflow happens,
 * depending on the specified overflow semantics:
 *
 * For BFOVERFLOW_SAT if 1 is returned, *limit it is set maximum value that
 * you can store in that integer. when -1 is returned, *limit is set to the
 * minimum value that an integer of that size can represent.
 *
 * For BFOVERFLOW_WRAP *limit is set by performing the operation in order to
 * "wrap" around towards zero for unsigned integers, or towards the most
 * negative number that is possible to represent for signed integers. */

#define BFOVERFLOW_WRAP 0
#define BFOVERFLOW_SAT 1
#define BFOVERFLOW_FAIL 2 /* Used by the BITFIELD command implementation. */

int checkUnsignedBitfieldOverflow(uint64_t value, int64_t incr, uint64_t bits, int owtype, uint64_t *limit) {
    uint64_t max = (bits == 64) ? UINT64_MAX : (((uint64_t)1 << bits) - 1);
    int64_t maxincr = max - value;
    int64_t minincr = -value;

    if (value > max || (incr > 0 && incr > maxincr)) {
        if (limit) {
            if (owtype == BFOVERFLOW_WRAP) {
                goto handle_wrap;
            } else if (owtype == BFOVERFLOW_SAT) {
                *limit = max;
            }
        }
        return 1;
    } else if (incr < 0 && incr < minincr) {
        if (limit) {
            if (owtype == BFOVERFLOW_WRAP) {
                goto handle_wrap;
            } else if (owtype == BFOVERFLOW_SAT) {
                *limit = 0;
            }
        }
        return -1;
    }
    return 0;

handle_wrap: {
    uint64_t mask = ((uint64_t)-1) << bits;
    uint64_t res = value + incr;

    res &= ~mask;
    *limit = res;
}
    return 1;
}

int checkSignedBitfieldOverflow(int64_t value, int64_t incr, uint64_t bits, int owtype, int64_t *limit) {
    int64_t max = (bits == 64) ? INT64_MAX : (((int64_t)1 << (bits - 1)) - 1);
    int64_t min = (-max) - 1;

    /* max/min and value are signed integers but to avoid undefined behavior
     * we temporarily cast them to unsigned integers before subtracting. */
    int64_t maxincr = (int64_t)((uint64_t)max - (uint64_t)value);
    int64_t minincr = (int64_t)((uint64_t)min - (uint64_t)value);

    if (value > max || (bits != 64 && incr > maxincr) || (value >= 0 && incr > 0 && incr > maxincr)) {
        if (limit) {
            if (owtype == BFOVERFLOW_WRAP) {
                goto handle_wrap;
            } else if (owtype == BFOVERFLOW_SAT) {
                *limit = max;
            }
        }
        return 1;
    } else if (value < min || (bits != 64 && incr < minincr) || (value < 0 && incr < 0 && incr < minincr)) {
        if (limit) {
            if (owtype == BFOVERFLOW_WRAP) {
                goto handle_wrap;
            } else if (owtype == BFOVERFLOW_SAT) {
                *limit = min;
            }
        }
        return -1;
    }
    return 0;

handle_wrap: {
    uint64_t msb = (uint64_t)1 << (bits - 1);
    uint64_t a = value, b = incr, c;
    c = a + b; /* Perform addition as unsigned so that's defined. */

    /* If the sign bit is set, propagate to all the higher order
     * bits, to cap the negative value. If it's clear, mask to
     * the positive integer limit. */
    if (bits < 64) {
        uint64_t mask = ((uint64_t)-1) << bits;
        if (c & msb) {
            c |= mask;
        } else {
            c &= ~mask;
        }
    }
    *limit = c;
}
    return 1;
}

/* Debugging function. Just show bits in the specified bitmap. Not used
 * but here for not having to rewrite it when debugging is needed. */
void printBits(unsigned char *p, unsigned long count) {
    unsigned long j, i, byte;

    for (j = 0; j < count; j++) {
        byte = p[j];
        for (i = 0x80; i > 0; i /= 2) printf("%c", (byte & i) ? '1' : '0');
        printf("|");
    }
    printf("\n");
}

/* -----------------------------------------------------------------------------
 * Bits related string commands: GETBIT, SETBIT, BITCOUNT, BITOP.
 * -------------------------------------------------------------------------- */

#define BITOP_AND 0
#define BITOP_OR 1
#define BITOP_XOR 2
#define BITOP_NOT 3

#define BITFIELDOP_GET 0
#define BITFIELDOP_SET 1
#define BITFIELDOP_INCRBY 2

/* This helper function used by GETBIT / SETBIT parses the bit offset argument
 * making sure an error is returned if it is negative or if it overflows
 * the server's 512 MB limit for the string value or more (server.proto_max_bulk_len).
 *
 * If the 'hash' argument is true, and 'bits is positive, then the command
 * will also parse bit offsets prefixed by "#". In such a case the offset
 * is multiplied by 'bits'. This is useful for the BITFIELD command. */
int getBitOffsetFromArgument(client *c, robj *o, uint64_t *offset, int hash, int bits) {
    long long loffset;
    char *err = "bit offset is not an integer or out of range";
    sds p = objectGetVal(o);
    size_t plen = sdslen(p);
    int usehash = 0;

    /* Handle #<offset> form. */
    if (p[0] == '#' && hash && bits > 0) usehash = 1;

    if (string2ll(p + usehash, plen - usehash, &loffset) == 0) {
        addReplyError(c, err);
        return C_ERR;
    }

    /* Adjust the offset by 'bits' for #<offset> form. */
    if (usehash) loffset *= bits;

    /* Limit offset to server.proto_max_bulk_len (512MB in bytes by default) */
    if (loffset < 0 || (!mustObeyClient(c) && (loffset >> 3) >= server.proto_max_bulk_len)) {
        addReplyError(c, err);
        return C_ERR;
    }

    *offset = loffset;
    return C_OK;
}

/* This helper function for BITFIELD parses a bitfield type in the form
 * <sign><bits> where sign is 'u' or 'i' for unsigned and signed, and
 * the bits is a value between 1 and 64. However 64 bits unsigned integers
 * are reported as an error because of current limitations of RESP
 * to return unsigned integer values greater than INT64_MAX.
 *
 * On error C_ERR is returned and an error is sent to the client. */
int getBitfieldTypeFromArgument(client *c, robj *o, int *sign, int *bits) {
    sds p = objectGetVal(o);
    size_t plen = sdslen(p);
    char *err = "Invalid bitfield type. Use something like i16 u8. Note that u64 is not supported but i64 is.";
    long long llbits;

    if (p[0] == 'i') {
        *sign = 1;
    } else if (p[0] == 'u') {
        *sign = 0;
    } else {
        addReplyError(c, err);
        return C_ERR;
    }

    if ((string2ll(p + 1, plen - 1, &llbits)) == 0 || llbits < 1 || (*sign == 1 && llbits > 64) ||
        (*sign == 0 && llbits > 63)) {
        addReplyError(c, err);
        return C_ERR;
    }
    *bits = llbits;
    return C_OK;
}

/* This is a helper function for commands implementations that need to write
 * bits to a string object. The command creates or pad with zeroes the string
 * so that the 'maxbit' bit can be addressed. The object is finally
 * returned. Otherwise if the key holds a wrong type NULL is returned and
 * an error is sent to the client. */
robj *lookupStringForBitCommand(client *c, uint64_t maxbit, int *dirty) {
    size_t byte = maxbit >> 3;
    robj *o = lookupKeyWrite(c->db, c->argv[1]);
    if (checkType(c, o, OBJ_STRING)) return NULL;
    if (dirty) *dirty = 0;

    if (o == NULL) {
        o = createObject(OBJ_STRING, sdsnewlen(NULL, byte + 1));
        dbAdd(c->db, c->argv[1], &o);
        if (dirty) *dirty = 1;
    } else {
        o = dbUnshareStringValue(c->db, c->argv[1], o);
        size_t oldlen = sdslen(objectGetVal(o));
        objectSetVal(o, sdsgrowzero(objectGetVal(o), byte + 1));
        if (dirty && oldlen != sdslen(objectGetVal(o))) *dirty = 1;
    }
    return o;
}

/* Return a pointer to the string object content, and stores its length
 * in 'len'. The user is required to pass (likely stack allocated) buffer
 * 'llbuf' of at least LONG_STR_SIZE bytes. Such a buffer is used in the case
 * the object is integer encoded in order to provide the representation
 * without using heap allocation.
 *
 * The function returns the pointer to the object array of bytes representing
 * the string it contains, that may be a pointer to 'llbuf' or to the
 * internal object representation. As a side effect 'len' is filled with
 * the length of such buffer.
 *
 * If the source object is NULL the function is guaranteed to return NULL
 * and set 'len' to 0. */
unsigned char *getObjectReadOnlyString(robj *o, long *len, char *llbuf) {
    serverAssert(!o || o->type == OBJ_STRING);
    unsigned char *p = NULL;

    /* Set the 'p' pointer to the string, that can be just a stack allocated
     * array if our string was integer encoded. */
    if (o && o->encoding == OBJ_ENCODING_INT) {
        p = (unsigned char *)llbuf;
        if (len) *len = ll2string(llbuf, LONG_STR_SIZE, (long)objectGetVal(o));
    } else if (o) {
        p = (unsigned char *)objectGetVal(o);
        if (len) *len = sdslen(objectGetVal(o));
    } else {
        if (len) *len = 0;
    }
    return p;
}

/* SETBIT key offset bitvalue */
void setbitCommand(client *c) {
    robj *o;
    char *err = "bit is not an integer or out of range";
    uint64_t bitoffset;
    ssize_t byte, bit;
    int byteval, bitval;
    long on;

    if (getBitOffsetFromArgument(c, c->argv[2], &bitoffset, 0, 0) != C_OK) return;

    if (getLongFromObjectOrReply(c, c->argv[3], &on, err) != C_OK) return;

    /* Bits can only be set or cleared... */
    if (on & ~1) {
        addReplyError(c, err);
        return;
    }

    int dirty;
    if ((o = lookupStringForBitCommand(c, bitoffset, &dirty)) == NULL) return;

    /* Get current values */
    byte = bitoffset >> 3;
    byteval = ((uint8_t *)objectGetVal(o))[byte];
    bit = 7 - (bitoffset & 0x7);
    bitval = byteval & (1 << bit);

    /* Either it is newly created, changed length, or the bit changes before and after.
     * Note that the bitval here is actually a decimal number.
     * So we need to use `!!` to convert it to 0 or 1 for comparison. */
    if (dirty || (!!bitval != on)) {
        /* Update byte with new bit value. */
        byteval &= ~(1 << bit);
        byteval |= ((on & 0x1) << bit);
        ((uint8_t *)objectGetVal(o))[byte] = byteval;
        signalModifiedKey(c, c->db, c->argv[1]);
        notifyKeyspaceEvent(NOTIFY_STRING, "setbit", c->argv[1], c->db->id);
        server.dirty++;
    }

    /* Return original value. */
    addReply(c, bitval ? shared.cone : shared.czero);
}

/* GETBIT key offset */
void getbitCommand(client *c) {
    robj *o;
    char llbuf[32];
    uint64_t bitoffset;
    size_t byte, bit;
    size_t bitval = 0;

    if (getBitOffsetFromArgument(c, c->argv[2], &bitoffset, 0, 0) != C_OK) return;

    if ((o = lookupKeyReadOrReply(c, c->argv[1], shared.czero)) == NULL || checkType(c, o, OBJ_STRING)) return;

    byte = bitoffset >> 3;
    bit = 7 - (bitoffset & 0x7);
    if (sdsEncodedObject(o)) {
        if (byte < sdslen(objectGetVal(o))) bitval = ((uint8_t *)objectGetVal(o))[byte] & (1 << bit);
    } else {
        if (byte < (size_t)ll2string(llbuf, sizeof(llbuf), (long)objectGetVal(o))) bitval = llbuf[byte] & (1 << bit);
    }

    addReply(c, bitval ? shared.cone : shared.czero);
}

/* BITOP op_name target_key src_key1 src_key2 src_key3 ... src_keyN */
VALKEY_NO_SANITIZE("alignment")
void bitopCommand(client *c) {
    char *opname = objectGetVal(c->argv[1]);
    robj *o, *targetkey = c->argv[2];
    unsigned long op, j, numkeys;
    robj **objects;                 /* Array of source objects. */
    unsigned char **src;            /* Array of source strings pointers. */
    unsigned long *len, maxlen = 0; /* Array of length of src strings,
                                       and max len. */
    unsigned long minlen = 0;       /* Min len among the input keys. */
    unsigned char *res = NULL;      /* Resulting string. */

    /* Parse the operation name. */
    if ((opname[0] == 'a' || opname[0] == 'A') && !strcasecmp(opname, "and"))
        op = BITOP_AND;
    else if ((opname[0] == 'o' || opname[0] == 'O') && !strcasecmp(opname, "or"))
        op = BITOP_OR;
    else if ((opname[0] == 'x' || opname[0] == 'X') && !strcasecmp(opname, "xor"))
        op = BITOP_XOR;
    else if ((opname[0] == 'n' || opname[0] == 'N') && !strcasecmp(opname, "not"))
        op = BITOP_NOT;
    else {
        addReplyErrorObject(c, shared.syntaxerr);
        return;
    }

    /* Sanity check: NOT accepts only a single key argument. */
    if (op == BITOP_NOT && c->argc != 4) {
        addReplyError(c, "BITOP NOT must be called with a single source key.");
        return;
    }

    /* Lookup keys, and store pointers to the string objects into an array. */
    numkeys = c->argc - 3;
    src = zmalloc(sizeof(unsigned char *) * numkeys);
    len = zmalloc(sizeof(long) * numkeys);
    objects = zmalloc(sizeof(robj *) * numkeys);
    for (j = 0; j < numkeys; j++) {
        o = lookupKeyRead(c->db, c->argv[j + 3]);
        /* Handle non-existing keys as empty strings. */
        if (o == NULL) {
            objects[j] = NULL;
            src[j] = NULL;
            len[j] = 0;
            minlen = 0;
            continue;
        }
        /* Return an error if one of the keys is not a string. */
        if (checkType(c, o, OBJ_STRING)) {
            unsigned long i;
            for (i = 0; i < j; i++) {
                if (objects[i]) decrRefCount(objects[i]);
            }
            zfree(src);
            zfree(len);
            zfree(objects);
            return;
        }
        objects[j] = getDecodedObject(o);
        src[j] = objectGetVal(objects[j]);
        len[j] = sdslen(objectGetVal(objects[j]));
        if (len[j] > maxlen) maxlen = len[j];
        if (j == 0 || len[j] < minlen) minlen = len[j];
    }

    /* Compute the bit operation, if at least one string is not empty. */
    if (maxlen) {
        res = (unsigned char *)sdsnewlen(NULL, maxlen);
        unsigned char output, byte;
        unsigned long i;

        /* Fast path: as far as we have data for all the input bitmaps we
         * can take a fast path that performs much better than the
         * vanilla algorithm. On ARM we skip the fast path since it will
         * result in GCC compiling the code using multiple-words load/store
         * operations that are not supported even in ARM >= v6. */
        j = 0;
#ifndef USE_ALIGNED_ACCESS
        if (minlen >= sizeof(unsigned long) * 4 && numkeys <= 16) {
            unsigned long *lp[16];
            unsigned long *lres = (unsigned long *)res;

            memcpy(lp, src, sizeof(unsigned long *) * numkeys);
            memcpy(res, src[0], minlen);

            /* Different branches per different operations for speed (sorry). */
            if (op == BITOP_AND) {
                while (minlen >= sizeof(unsigned long) * 4) {
                    for (i = 1; i < numkeys; i++) {
                        lres[0] &= lp[i][0];
                        lres[1] &= lp[i][1];
                        lres[2] &= lp[i][2];
                        lres[3] &= lp[i][3];
                        lp[i] += 4;
                    }
                    lres += 4;
                    j += sizeof(unsigned long) * 4;
                    minlen -= sizeof(unsigned long) * 4;
                }
            } else if (op == BITOP_OR) {
                while (minlen >= sizeof(unsigned long) * 4) {
                    for (i = 1; i < numkeys; i++) {
                        lres[0] |= lp[i][0];
                        lres[1] |= lp[i][1];
                        lres[2] |= lp[i][2];
                        lres[3] |= lp[i][3];
                        lp[i] += 4;
                    }
                    lres += 4;
                    j += sizeof(unsigned long) * 4;
                    minlen -= sizeof(unsigned long) * 4;
                }
            } else if (op == BITOP_XOR) {
                while (minlen >= sizeof(unsigned long) * 4) {
                    for (i = 1; i < numkeys; i++) {
                        lres[0] ^= lp[i][0];
                        lres[1] ^= lp[i][1];
                        lres[2] ^= lp[i][2];
                        lres[3] ^= lp[i][3];
                        lp[i] += 4;
                    }
                    lres += 4;
                    j += sizeof(unsigned long) * 4;
                    minlen -= sizeof(unsigned long) * 4;
                }
            } else if (op == BITOP_NOT) {
                while (minlen >= sizeof(unsigned long) * 4) {
                    lres[0] = ~lres[0];
                    lres[1] = ~lres[1];
                    lres[2] = ~lres[2];
                    lres[3] = ~lres[3];
                    lres += 4;
                    j += sizeof(unsigned long) * 4;
                    minlen -= sizeof(unsigned long) * 4;
                }
            }
        }
#endif

        /* j is set to the next byte to process by the previous loop. */
        for (; j < maxlen; j++) {
            output = (len[0] <= j) ? 0 : src[0][j];
            if (op == BITOP_NOT) output = ~output;
            for (i = 1; i < numkeys; i++) {
                int skip = 0;
                byte = (len[i] <= j) ? 0 : src[i][j];
                switch (op) {
                case BITOP_AND:
                    output &= byte;
                    skip = (output == 0);
                    break;
                case BITOP_OR:
                    output |= byte;
                    skip = (output == 0xff);
                    break;
                case BITOP_XOR: output ^= byte; break;
                }

                if (skip) {
                    break;
                }
            }
            res[j] = output;
        }
    }
    for (j = 0; j < numkeys; j++) {
        if (objects[j]) decrRefCount(objects[j]);
    }
    zfree(src);
    zfree(len);
    zfree(objects);

    /* Store the computed value into the target key */
    if (maxlen) {
        o = createObject(OBJ_STRING, res);
        setKey(c, c->db, targetkey, &o, 0);
        notifyKeyspaceEvent(NOTIFY_STRING, "set", targetkey, c->db->id);
        server.dirty++;
    } else if (dbDelete(c->db, targetkey)) {
        signalModifiedKey(c, c->db, targetkey);
        notifyKeyspaceEvent(NOTIFY_GENERIC, "del", targetkey, c->db->id);
        server.dirty++;
    }
    addReplyLongLong(c, maxlen); /* Return the output string length in bytes. */
}

/* BITCOUNT key [start [end [BIT|BYTE]]] */
void bitcountCommand(client *c) {
    robj *o;
    long long start, end;
    long strlen;
    unsigned char *p;
    char llbuf[LONG_STR_SIZE];
    int isbit = 0;
    unsigned char first_byte_neg_mask = 0, last_byte_neg_mask = 0;

    /* Parse start/end range if any. */
    if (c->argc == 3 || c->argc == 4 || c->argc == 5) {
        if (getLongLongFromObjectOrReply(c, c->argv[2], &start, NULL) != C_OK) return;
        if (c->argc == 5) {
            if (!strcasecmp(objectGetVal(c->argv[4]), "bit"))
                isbit = 1;
            else if (!strcasecmp(objectGetVal(c->argv[4]), "byte"))
                isbit = 0;
            else {
                addReplyErrorObject(c, shared.syntaxerr);
                return;
            }
        }
        if (c->argc >= 4) {
            if (getLongLongFromObjectOrReply(c, c->argv[3], &end, NULL) != C_OK) return;
        }

        /* Lookup, check for type. */
        o = lookupKeyRead(c->db, c->argv[1]);
        if (checkType(c, o, OBJ_STRING)) return;
        p = getObjectReadOnlyString(o, &strlen, llbuf);
        long long totlen = strlen;

        /* Make sure we will not overflow */
        serverAssert(totlen <= LLONG_MAX >> 3);

        if (c->argc < 4) end = totlen - 1;

        /* Convert negative indexes */
        if (start < 0 && end < 0 && start > end) {
            addReply(c, shared.czero);
            return;
        }
        if (isbit) totlen <<= 3;
        if (start < 0) start = totlen + start;
        if (end < 0) end = totlen + end;
        if (start < 0) start = 0;
        if (end < 0) end = 0;
        if (end >= totlen) end = totlen - 1;
        if (isbit && start <= end) {
            /* Before converting bit offset to byte offset, create negative masks
             * for the edges. */
            first_byte_neg_mask = ~((1 << (8 - (start & 7))) - 1) & 0xFF;
            last_byte_neg_mask = (1 << (7 - (end & 7))) - 1;
            start >>= 3;
            end >>= 3;
        }
    } else if (c->argc == 2) {
        /* Lookup, check for type. */
        o = lookupKeyRead(c->db, c->argv[1]);
        if (checkType(c, o, OBJ_STRING)) return;
        p = getObjectReadOnlyString(o, &strlen, llbuf);
        /* The whole string. */
        start = 0;
        end = strlen - 1;
    } else {
        /* Syntax error. */
        addReplyErrorObject(c, shared.syntaxerr);
        return;
    }

    /* Return 0 for non existing keys. */
    if (o == NULL) {
        addReply(c, shared.czero);
        return;
    }

    /* Precondition: end >= 0 && end < strlen, so the only condition where
     * zero can be returned is: start > end. */
    if (start > end) {
        addReply(c, shared.czero);
    } else {
        long bytes = (long)(end - start + 1);
        long long count = serverPopcount(p + start, bytes);
        if (first_byte_neg_mask != 0 || last_byte_neg_mask != 0) {
            unsigned char firstlast[2] = {0, 0};
            /* We may count bits of first byte and last byte which are out of
             * range. So we need to subtract them. Here we use a trick. We set
             * bits in the range to zero. So these bit will not be excluded. */
            if (first_byte_neg_mask != 0) firstlast[0] = p[start] & first_byte_neg_mask;
            if (last_byte_neg_mask != 0) firstlast[1] = p[end] & last_byte_neg_mask;
            count -= serverPopcount(firstlast, 2);
        }
        addReplyLongLong(c, count);
    }
}

/* BITPOS key bit [start [end [BIT|BYTE]]] */
void bitposCommand(client *c) {
    robj *o;
    long long start, end;
    long bit, strlen;
    unsigned char *p;
    char llbuf[LONG_STR_SIZE];
    int isbit = 0, end_given = 0;
    unsigned char first_byte_neg_mask = 0, last_byte_neg_mask = 0;

    /* Parse the bit argument to understand what we are looking for, set
     * or clear bits. */
    if (getLongFromObjectOrReply(c, c->argv[2], &bit, NULL) != C_OK) return;
    if (bit != 0 && bit != 1) {
        addReplyError(c, "The bit argument must be 1 or 0.");
        return;
    }

    /* Parse start/end range if any. */
    if (c->argc == 4 || c->argc == 5 || c->argc == 6) {
        if (getLongLongFromObjectOrReply(c, c->argv[3], &start, NULL) != C_OK) return;
        if (c->argc == 6) {
            if (!strcasecmp(objectGetVal(c->argv[5]), "bit"))
                isbit = 1;
            else if (!strcasecmp(objectGetVal(c->argv[5]), "byte"))
                isbit = 0;
            else {
                addReplyErrorObject(c, shared.syntaxerr);
                return;
            }
        }
        if (c->argc >= 5) {
            if (getLongLongFromObjectOrReply(c, c->argv[4], &end, NULL) != C_OK) return;
            end_given = 1;
        }

        /* Lookup, check for type. */
        o = lookupKeyRead(c->db, c->argv[1]);
        if (checkType(c, o, OBJ_STRING)) return;
        p = getObjectReadOnlyString(o, &strlen, llbuf);

        /* Make sure we will not overflow */
        long long totlen = strlen;
        serverAssert(totlen <= LLONG_MAX >> 3);

        if (c->argc < 5) end = totlen - 1;

        if (isbit) totlen <<= 3;
        /* Convert negative indexes */
        if (start < 0) start = totlen + start;
        if (end < 0) end = totlen + end;
        if (start < 0) start = 0;
        if (end < 0) end = 0;
        if (end >= totlen) end = totlen - 1;
        if (isbit && start <= end) {
            /* Before converting bit offset to byte offset, create negative masks
             * for the edges. */
            first_byte_neg_mask = ~((1 << (8 - (start & 7))) - 1) & 0xFF;
            last_byte_neg_mask = (1 << (7 - (end & 7))) - 1;
            start >>= 3;
            end >>= 3;
        }
    } else if (c->argc == 3) {
        /* Lookup, check for type. */
        o = lookupKeyRead(c->db, c->argv[1]);
        if (checkType(c, o, OBJ_STRING)) return;
        p = getObjectReadOnlyString(o, &strlen, llbuf);

        /* The whole string. */
        start = 0;
        end = strlen - 1;
    } else {
        /* Syntax error. */
        addReplyErrorObject(c, shared.syntaxerr);
        return;
    }

    /* If the key does not exist, from our point of view it is an infinite
     * array of 0 bits. If the user is looking for the first clear bit return 0,
     * If the user is looking for the first set bit, return -1. */
    if (o == NULL) {
        addReplyLongLong(c, bit ? -1 : 0);
        return;
    }

    /* For empty ranges (start > end) we return -1 as an empty range does
     * not contain a 0 nor a 1. */
    if (start > end) {
        addReplyLongLong(c, -1);
    } else {
        long bytes = end - start + 1;
        long long pos;
        unsigned char tmpchar;
        if (first_byte_neg_mask) {
            if (bit)
                tmpchar = p[start] & ~first_byte_neg_mask;
            else
                tmpchar = p[start] | first_byte_neg_mask;
            /* Special case, there is only one byte */
            if (last_byte_neg_mask && bytes == 1) {
                if (bit)
                    tmpchar = tmpchar & ~last_byte_neg_mask;
                else
                    tmpchar = tmpchar | last_byte_neg_mask;
            }
            pos = serverBitpos(&tmpchar, 1, bit);
            /* If there are no more bytes or we get valid pos, we can exit early */
            if (bytes == 1 || (pos != -1 && pos != 8)) goto result;
            start++;
            bytes--;
        }
        /* If the last byte has not bits in the range, we should exclude it */
        long curbytes = bytes - (last_byte_neg_mask ? 1 : 0);
        if (curbytes > 0) {
            pos = serverBitpos(p + start, curbytes, bit);
            /* If there is no more bytes or we get valid pos, we can exit early */
            if (bytes == curbytes || (pos != -1 && pos != (long long)curbytes << 3)) goto result;
            start += curbytes;
            bytes -= curbytes;
        }
        if (bit)
            tmpchar = p[end] & ~last_byte_neg_mask;
        else
            tmpchar = p[end] | last_byte_neg_mask;
        pos = serverBitpos(&tmpchar, 1, bit);

    result:
        /* If we are looking for clear bits, and the user specified an exact
         * range with start-end, we can't consider the right of the range as
         * zero padded (as we do when no explicit end is given).
         *
         * So if serverBitpos() returns the first bit outside the range,
         * we return -1 to the caller, to mean, in the specified range there
         * is not a single "0" bit. */
        if (end_given && bit == 0 && pos == (long long)bytes << 3) {
            addReplyLongLong(c, -1);
            return;
        }
        if (pos != -1) pos += (long long)start << 3; /* Adjust for the bytes we skipped. */
        addReplyLongLong(c, pos);
    }
}

/* BITFIELD key subcommand-1 arg ... subcommand-2 arg ... subcommand-N ...
 *
 * Supported subcommands:
 *
 * GET <type> <offset>
 * SET <type> <offset> <value>
 * INCRBY <type> <offset> <increment>
 * OVERFLOW [WRAP|SAT|FAIL]
 */

#define BITFIELD_FLAG_NONE 0
#define BITFIELD_FLAG_READONLY (1 << 0)

struct bitfieldOp {
    uint64_t offset; /* Bitfield offset. */
    int64_t i64;     /* Increment amount (INCRBY) or SET value */
    int opcode;      /* Operation id. */
    int owtype;      /* Overflow type to use. */
    int bits;        /* Integer bitfield bits width. */
    int sign;        /* True if signed, otherwise unsigned op. */
};

/* This implements both the BITFIELD command and the BITFIELD_RO command
 * when flags is set to BITFIELD_FLAG_READONLY: in this case only the
 * GET subcommand is allowed, other subcommands will return an error. */
void bitfieldGeneric(client *c, int flags) {
    robj *o;
    uint64_t bitoffset;
    int j, numops = 0, changes = 0, dirty = 0;
    struct bitfieldOp *ops = NULL; /* Array of ops to execute at end. */
    int owtype = BFOVERFLOW_WRAP;  /* Overflow type. */
    int readonly = 1;
    uint64_t highest_write_offset = 0;

    for (j = 2; j < c->argc; j++) {
        int remargs = c->argc - j - 1;           /* Remaining args other than current. */
        char *subcmd = objectGetVal(c->argv[j]); /* Current command name. */
        int opcode;                              /* Current operation code. */
        long long i64 = 0;                       /* Signed SET value. */
        int sign = 0;                            /* Signed or unsigned type? */
        int bits = 0;                            /* Bitfield width in bits. */

        if (!strcasecmp(subcmd, "get") && remargs >= 2)
            opcode = BITFIELDOP_GET;
        else if (!strcasecmp(subcmd, "set") && remargs >= 3)
            opcode = BITFIELDOP_SET;
        else if (!strcasecmp(subcmd, "incrby") && remargs >= 3)
            opcode = BITFIELDOP_INCRBY;
        else if (!strcasecmp(subcmd, "overflow") && remargs >= 1) {
            char *owtypename = objectGetVal(c->argv[j + 1]);
            j++;
            if (!strcasecmp(owtypename, "wrap"))
                owtype = BFOVERFLOW_WRAP;
            else if (!strcasecmp(owtypename, "sat"))
                owtype = BFOVERFLOW_SAT;
            else if (!strcasecmp(owtypename, "fail"))
                owtype = BFOVERFLOW_FAIL;
            else {
                addReplyError(c, "Invalid OVERFLOW type specified");
                zfree(ops);
                return;
            }
            continue;
        } else {
            addReplyErrorObject(c, shared.syntaxerr);
            zfree(ops);
            return;
        }

        /* Get the type and offset arguments, common to all the ops. */
        if (getBitfieldTypeFromArgument(c, c->argv[j + 1], &sign, &bits) != C_OK) {
            zfree(ops);
            return;
        }

        if (getBitOffsetFromArgument(c, c->argv[j + 2], &bitoffset, 1, bits) != C_OK) {
            zfree(ops);
            return;
        }

        if (opcode != BITFIELDOP_GET) {
            readonly = 0;
            if (highest_write_offset < bitoffset + bits - 1) highest_write_offset = bitoffset + bits - 1;
            /* INCRBY and SET require another argument. */
            if (getLongLongFromObjectOrReply(c, c->argv[j + 3], &i64, NULL) != C_OK) {
                zfree(ops);
                return;
            }
        }

        /* Populate the array of operations we'll process. */
        ops = zrealloc(ops, sizeof(*ops) * (numops + 1));
        ops[numops].offset = bitoffset;
        ops[numops].i64 = i64;
        ops[numops].opcode = opcode;
        ops[numops].owtype = owtype;
        ops[numops].bits = bits;
        ops[numops].sign = sign;
        numops++;

        j += 3 - (opcode == BITFIELDOP_GET);
    }

    if (readonly) {
        /* Lookup for read is ok if key doesn't exit, but errors
         * if it's not a string. */
        o = lookupKeyRead(c->db, c->argv[1]);
        if (o != NULL && checkType(c, o, OBJ_STRING)) {
            zfree(ops);
            return;
        }
    } else {
        if (flags & BITFIELD_FLAG_READONLY) {
            zfree(ops);
            addReplyError(c, "BITFIELD_RO only supports the GET subcommand");
            return;
        }

        /* Lookup by making room up to the farthest bit reached by
         * this operation. */
        if ((o = lookupStringForBitCommand(c, highest_write_offset, &dirty)) == NULL) {
            zfree(ops);
            return;
        }
    }

    initDeferredReplyBuffer(c);
    addReplyArrayLen(c, numops);

    /* Actually process the operations. */
    for (j = 0; j < numops; j++) {
        struct bitfieldOp *thisop = ops + j;

        /* Execute the operation. */
        if (thisop->opcode == BITFIELDOP_SET || thisop->opcode == BITFIELDOP_INCRBY) {
            /* SET and INCRBY: We handle both with the same code path
             * for simplicity. SET return value is the previous value so
             * we need fetch & store as well. */

            /* We need two different but very similar code paths for signed
             * and unsigned operations, since the set of functions to get/set
             * the integers and the used variables types are different. */
            if (thisop->sign) {
                int64_t oldval, newval, wrapped, retval;
                int overflow;

                oldval = getSignedBitfield(objectGetVal(o), thisop->offset, thisop->bits);

                if (thisop->opcode == BITFIELDOP_INCRBY) {
                    overflow = checkSignedBitfieldOverflow(oldval, thisop->i64, thisop->bits, thisop->owtype, &wrapped);
                    newval = overflow ? wrapped : oldval + thisop->i64;
                    retval = newval;
                } else {
                    newval = thisop->i64;
                    overflow = checkSignedBitfieldOverflow(newval, 0, thisop->bits, thisop->owtype, &wrapped);
                    if (overflow) newval = wrapped;
                    retval = oldval;
                }

                /* On overflow of type is "FAIL", don't write and return
                 * NULL to signal the condition. */
                if (!(overflow && thisop->owtype == BFOVERFLOW_FAIL)) {
                    addReplyLongLong(c, retval);
                    setSignedBitfield(objectGetVal(o), thisop->offset, thisop->bits, newval);

                    if (dirty || (oldval != newval)) changes++;
                } else {
                    addReplyNull(c);
                }
            } else {
                /* Initialization of 'wrapped' is required to avoid
                 * false-positive warning "-Wmaybe-uninitialized" */
                uint64_t oldval, newval, retval, wrapped = 0;
                int overflow;

                oldval = getUnsignedBitfield(objectGetVal(o), thisop->offset, thisop->bits);

                if (thisop->opcode == BITFIELDOP_INCRBY) {
                    newval = oldval + thisop->i64;
                    overflow =
                        checkUnsignedBitfieldOverflow(oldval, thisop->i64, thisop->bits, thisop->owtype, &wrapped);
                    if (overflow) newval = wrapped;
                    retval = newval;
                } else {
                    newval = thisop->i64;
                    overflow = checkUnsignedBitfieldOverflow(newval, 0, thisop->bits, thisop->owtype, &wrapped);
                    if (overflow) newval = wrapped;
                    retval = oldval;
                }
                /* On overflow of type is "FAIL", don't write and return
                 * NULL to signal the condition. */
                if (!(overflow && thisop->owtype == BFOVERFLOW_FAIL)) {
                    addReplyLongLong(c, retval);
                    setUnsignedBitfield(objectGetVal(o), thisop->offset, thisop->bits, newval);

                    if (dirty || (oldval != newval)) changes++;
                } else {
                    addReplyNull(c);
                }
            }
        } else {
            /* GET */
            unsigned char buf[9];
            long strlen = 0;
            unsigned char *src = NULL;
            char llbuf[LONG_STR_SIZE];

            if (o != NULL) src = getObjectReadOnlyString(o, &strlen, llbuf);

            /* For GET we use a trick: before executing the operation
             * copy up to 9 bytes to a local buffer, so that we can easily
             * execute up to 64 bit operations that are at actual string
             * object boundaries. */
            memset(buf, 0, 9);
            int i;
            uint64_t byte = thisop->offset >> 3;
            for (i = 0; i < 9; i++) {
                if (src == NULL || i + byte >= (uint64_t)strlen) break;
                buf[i] = src[i + byte];
            }

            /* Now operate on the copied buffer which is guaranteed
             * to be zero-padded. */
            if (thisop->sign) {
                int64_t val = getSignedBitfield(buf, thisop->offset - (byte * 8), thisop->bits);
                addReplyLongLong(c, val);
            } else {
                uint64_t val = getUnsignedBitfield(buf, thisop->offset - (byte * 8), thisop->bits);
                addReplyLongLong(c, val);
            }
        }
    }

    if (changes) {
        signalModifiedKey(c, c->db, c->argv[1]);
        notifyKeyspaceEvent(NOTIFY_STRING, "setbit", c->argv[1], c->db->id);
        server.dirty += changes;
    }
    commitDeferredReplyBuffer(c, 1);
    zfree(ops);
}

void bitfieldCommand(client *c) {
    bitfieldGeneric(c, BITFIELD_FLAG_NONE);
}

void bitfieldroCommand(client *c) {
    bitfieldGeneric(c, BITFIELD_FLAG_READONLY);
}
