futriix/src/intset.c

/*
 * Copyright (c) 2009-2012, Pieter Noordhuis <pcnoordhuis at gmail dot com>
 * 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "intset.h"
#include "zmalloc.h"
#include "endianconv.h"
#include "serverassert.h"

/* Note that these encodings are ordered, so:
 * INTSET_ENC_INT16 < INTSET_ENC_INT32 < INTSET_ENC_INT64. */
#define INTSET_ENC_INT16 (sizeof(int16_t))
#define INTSET_ENC_INT32 (sizeof(int32_t))
#define INTSET_ENC_INT64 (sizeof(int64_t))

/* Return the required encoding for the provided value. */
static uint8_t _intsetValueEncoding(int64_t v) {
    if (v < INT32_MIN || v > INT32_MAX)
        return INTSET_ENC_INT64;
    else if (v < INT16_MIN || v > INT16_MAX)
        return INTSET_ENC_INT32;
    else
        return INTSET_ENC_INT16;
}

/* Return the value at pos, given an encoding. */
static int64_t _intsetGetEncoded(intset *is, int pos, uint8_t enc) {
    int64_t v64;
    int32_t v32;
    int16_t v16;

    if (enc == INTSET_ENC_INT64) {
        memcpy(&v64, ((int64_t *)is->contents) + pos, sizeof(v64));
        memrev64ifbe(&v64);
        return v64;
    } else if (enc == INTSET_ENC_INT32) {
        memcpy(&v32, ((int32_t *)is->contents) + pos, sizeof(v32));
        memrev32ifbe(&v32);
        return v32;
    } else {
        memcpy(&v16, ((int16_t *)is->contents) + pos, sizeof(v16));
        memrev16ifbe(&v16);
        return v16;
    }
}

/* Return the value at pos, using the configured encoding. */
static int64_t _intsetGet(intset *is, int pos) {
    return _intsetGetEncoded(is, pos, intrev32ifbe(is->encoding));
}

/* Set the value at pos, using the configured encoding. */
static void _intsetSet(intset *is, int pos, int64_t value) {
    uint32_t encoding = intrev32ifbe(is->encoding);

    if (encoding == INTSET_ENC_INT64) {
        ((int64_t *)is->contents)[pos] = value;
        memrev64ifbe(((int64_t *)is->contents) + pos);
    } else if (encoding == INTSET_ENC_INT32) {
        ((int32_t *)is->contents)[pos] = value;
        memrev32ifbe(((int32_t *)is->contents) + pos);
    } else {
        ((int16_t *)is->contents)[pos] = value;
        memrev16ifbe(((int16_t *)is->contents) + pos);
    }
}

/* Create an empty intset. */
intset *intsetNew(void) {
    intset *is = zmalloc(sizeof(intset));
    is->encoding = intrev32ifbe(INTSET_ENC_INT16);
    is->length = 0;
    return is;
}

/* Resize the intset */
static intset *intsetResize(intset *is, uint32_t len) {
    uint64_t size = (uint64_t)len * intrev32ifbe(is->encoding);
    assert(size <= SIZE_MAX - sizeof(intset));
    is = zrealloc(is, sizeof(intset) + size);
    return is;
}

/* Search for the position of "value". Return 1 when the value was found and
 * sets "pos" to the position of the value within the intset. Return 0 when
 * the value is not present in the intset and sets "pos" to the position
 * where "value" can be inserted. */
static uint8_t intsetSearch(intset *is, int64_t value, uint32_t *pos) {
    int min = 0, max = intrev32ifbe(is->length) - 1, mid = -1;
    int64_t cur = -1;

    /* The value can never be found when the set is empty */
    if (intrev32ifbe(is->length) == 0) {
        if (pos) *pos = 0;
        return 0;
    } else {
        /* Check for the case where we know we cannot find the value,
         * but do know the insert position. */
        if (value > _intsetGet(is, max)) {
            if (pos) *pos = intrev32ifbe(is->length);
            return 0;
        } else if (value < _intsetGet(is, 0)) {
            if (pos) *pos = 0;
            return 0;
        }
    }

    while (max >= min) {
        mid = ((unsigned int)min + (unsigned int)max) >> 1;
        cur = _intsetGet(is, mid);
        if (value > cur) {
            min = mid + 1;
        } else if (value < cur) {
            max = mid - 1;
        } else {
            break;
        }
    }

    if (value == cur) {
        if (pos) *pos = mid;
        return 1;
    } else {
        if (pos) *pos = min;
        return 0;
    }
}

/* Upgrades the intset to a larger encoding and inserts the given integer. */
static intset *intsetUpgradeAndAdd(intset *is, int64_t value) {
    uint8_t curenc = intrev32ifbe(is->encoding);
    uint8_t newenc = _intsetValueEncoding(value);
    int length = intrev32ifbe(is->length);
    int prepend = value < 0 ? 1 : 0;

    /* First set new encoding and resize */
    is->encoding = intrev32ifbe(newenc);
    is = intsetResize(is, intrev32ifbe(is->length) + 1);

    /* Upgrade back-to-front so we don't overwrite values.
     * Note that the "prepend" variable is used to make sure we have an empty
     * space at either the beginning or the end of the intset. */
    while (length--) _intsetSet(is, length + prepend, _intsetGetEncoded(is, length, curenc));

    /* Set the value at the beginning or the end. */
    if (prepend)
        _intsetSet(is, 0, value);
    else
        _intsetSet(is, intrev32ifbe(is->length), value);
    is->length = intrev32ifbe(intrev32ifbe(is->length) + 1);
    return is;
}

static void intsetMoveTail(intset *is, uint32_t from, uint32_t to) {
    void *src, *dst;
    uint32_t bytes = intrev32ifbe(is->length) - from;
    uint32_t encoding = intrev32ifbe(is->encoding);

    if (encoding == INTSET_ENC_INT64) {
        src = (int64_t *)is->contents + from;
        dst = (int64_t *)is->contents + to;
        bytes *= sizeof(int64_t);
    } else if (encoding == INTSET_ENC_INT32) {
        src = (int32_t *)is->contents + from;
        dst = (int32_t *)is->contents + to;
        bytes *= sizeof(int32_t);
    } else {
        src = (int16_t *)is->contents + from;
        dst = (int16_t *)is->contents + to;
        bytes *= sizeof(int16_t);
    }
    memmove(dst, src, bytes);
}

/* Insert an integer in the intset */
intset *intsetAdd(intset *is, int64_t value, uint8_t *success) {
    uint8_t valenc = _intsetValueEncoding(value);
    uint32_t pos;
    if (success) *success = 1;

    /* Upgrade encoding if necessary. If we need to upgrade, we know that
     * this value should be either appended (if > 0) or prepended (if < 0),
     * because it lies outside the range of existing values. */
    if (valenc > intrev32ifbe(is->encoding)) {
        /* This always succeeds, so we don't need to curry *success. */
        return intsetUpgradeAndAdd(is, value);
    } else {
        /* Abort if the value is already present in the set.
         * This call will populate "pos" with the right position to insert
         * the value when it cannot be found. */
        if (intsetSearch(is, value, &pos)) {
            if (success) *success = 0;
            return is;
        }

        is = intsetResize(is, intrev32ifbe(is->length) + 1);
        if (pos < intrev32ifbe(is->length)) intsetMoveTail(is, pos, pos + 1);
    }

    _intsetSet(is, pos, value);
    is->length = intrev32ifbe(intrev32ifbe(is->length) + 1);
    return is;
}

/* Delete integer from intset */
intset *intsetRemove(intset *is, int64_t value, int *success) {
    uint8_t valenc = _intsetValueEncoding(value);
    uint32_t pos;
    if (success) *success = 0;

    if (valenc <= intrev32ifbe(is->encoding) && intsetSearch(is, value, &pos)) {
        uint32_t len = intrev32ifbe(is->length);

        /* We know we can delete */
        if (success) *success = 1;

        /* Overwrite value with tail and update length */
        if (pos < (len - 1)) intsetMoveTail(is, pos + 1, pos);
        is = intsetResize(is, len - 1);
        is->length = intrev32ifbe(len - 1);
    }
    return is;
}

/* Determine whether a value belongs to this set */
uint8_t intsetFind(intset *is, int64_t value) {
    uint8_t valenc = _intsetValueEncoding(value);
    return valenc <= intrev32ifbe(is->encoding) && intsetSearch(is, value, NULL);
}

/* Return random member */
int64_t intsetRandom(intset *is) {
    uint32_t len = intrev32ifbe(is->length);
    assert(len); /* avoid division by zero on corrupt intset payload. */
    return _intsetGet(is, rand() % len);
}

/* Return the largest member. */
int64_t intsetMax(intset *is) {
    uint32_t len = intrev32ifbe(is->length);
    return _intsetGet(is, len - 1);
}

/* Return the smallest member. */
int64_t intsetMin(intset *is) {
    return _intsetGet(is, 0);
}

/* Get the value at the given position. When this position is
 * out of range the function returns 0, when in range it returns 1. */
uint8_t intsetGet(intset *is, uint32_t pos, int64_t *value) {
    if (pos < intrev32ifbe(is->length)) {
        *value = _intsetGet(is, pos);
        return 1;
    }
    return 0;
}

/* Return intset length */
uint32_t intsetLen(const intset *is) {
    return intrev32ifbe(is->length);
}

/* Return intset blob size in bytes. */
size_t intsetBlobLen(intset *is) {
    return sizeof(intset) + (size_t)intrev32ifbe(is->length) * intrev32ifbe(is->encoding);
}

/* Validate the integrity of the data structure.
 * when `deep` is 0, only the integrity of the header is validated.
 * when `deep` is 1, we make sure there are no duplicate or out of order records. */
int intsetValidateIntegrity(const unsigned char *p, size_t size, int deep) {
    intset *is = (intset *)p;
    /* check that we can actually read the header. */
    if (size < sizeof(*is)) return 0;

    uint32_t encoding = intrev32ifbe(is->encoding);

    size_t record_size;
    if (encoding == INTSET_ENC_INT64) {
        record_size = INTSET_ENC_INT64;
    } else if (encoding == INTSET_ENC_INT32) {
        record_size = INTSET_ENC_INT32;
    } else if (encoding == INTSET_ENC_INT16) {
        record_size = INTSET_ENC_INT16;
    } else {
        return 0;
    }

    /* check that the size matches (all records are inside the buffer). */
    uint32_t count = intrev32ifbe(is->length);
    if (sizeof(*is) + count * record_size != size) return 0;

    /* check that the set is not empty. */
    if (count == 0) return 0;

    if (!deep) return 1;

    /* check that there are no dup or out of order records. */
    int64_t prev = _intsetGet(is, 0);
    for (uint32_t i = 1; i < count; i++) {
        int64_t cur = _intsetGet(is, i);
        if (cur <= prev) return 0;
        prev = cur;
    }

    return 1;
}