Class: BloomFilter

Inherits:
Object
  • Object
show all
Defined in:
lib/bloomfilter.rb,
ext/sbloomfilter.c

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.new(*args) ⇒ Object 



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# File 'ext/sbloomfilter.c', line 76

static VALUE bf_s_new(int argc, VALUE *argv, VALUE self) {
    struct BloomFilter *bf;
    VALUE arg1, arg2, arg3, arg4, arg5, obj;
    int m, k, s, b, r, bytes;

    obj = Data_Make_Struct(self, struct BloomFilter, NULL, bits_free, bf);

    /* default = Fugou approach :-) */
    arg1 = INT2FIX(100000000);
    arg2 = INT2FIX(4);
    arg3 = INT2FIX(0);
    arg4 = INT2FIX(1);
    arg5 = INT2FIX(0);

    switch (argc) {
        case 5:
	    if (argv[4] == Qtrue) {
		    arg5 = INT2FIX(1);
	    }
        case 4:
	    arg4 = argv[3];
        case 3:
	    arg3 = argv[2];
        case 2:
	    arg2 = argv[1];
        case 1:
	    arg1 = argv[0];
	    break;
    }

    m = FIX2INT(arg1);
    k = FIX2INT(arg2);
    s = FIX2INT(arg3);
    b = FIX2INT(arg4);
    r = FIX2INT(arg5);

    if (b < 1 || b > 8)
        rb_raise(rb_eArgError, "bucket size");
    if (m < 1)
        rb_raise(rb_eArgError, "array size");
    if (k < 1)
        rb_raise(rb_eArgError, "hash length");
    if (s < 0)
        rb_raise(rb_eArgError, "random seed");

    bf->b = b;
    bf->m = m;
    bf->k = k;
    bf->s = s;
    bf->r = r;
    bf->num_set = 0;

    bytes = ((m * b) + 15) / 8;
    bf->ptr = ALLOC_N(unsigned char, bytes);

    /* initialize the bits with zeros */
    memset(bf->ptr, 0, bytes);
    rb_iv_set(obj, "@hash_value", rb_hash_new());

    return obj;
}

Instance Method Details

#[](key) ⇒ Object 



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# File 'lib/bloomfilter.rb', line 19

def [] key
  return nil unless include?(key)
  @hash_value[key]
end

#[]=(key, value) ⇒ Object 



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# File 'lib/bloomfilter.rb', line 14

def []= key, value
  insert(key)
  @hash_value[key] = value
end

#b ⇒ Object 



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# File 'ext/sbloomfilter.c', line 150

static VALUE bf_b(VALUE self) {
    struct BloomFilter *bf;
    Data_Get_Struct(self, struct BloomFilter, bf);
    return INT2FIX(bf->b);
}

#delete(key) ⇒ Object 



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# File 'ext/sbloomfilter.c', line 199

static VALUE bf_delete(VALUE self, VALUE key) {
    int index, seed;
    int i, len, m, k, s;
    char *ckey;

    struct BloomFilter *bf;
    Data_Get_Struct(self, struct BloomFilter, bf);

    Check_Type(key, T_STRING);
    ckey = STR2CSTR(key);
    len = (int) (RSTRINGLEN(key)); /* length of the string in bytes */

    m = bf->m;
    k = bf->k;
    s = bf->s;

    for (i = 0; i <= k - 1; i++) {
        /* seeds for hash functions */
        seed = i + s;

        /* hash */
        index = (int) (crc32((unsigned int) (seed), ckey, len) % (unsigned int) (m));

        /*  set a bit at the index */
        bucket_unset(bf, index);
    }

    bf->num_set += 1;
    return Qnil;
}

#include?(key) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'ext/sbloomfilter.c', line 231

static VALUE bf_include(VALUE self, VALUE key) {
    int index, seed;
    int i, len, m, k, s;
    char *ckey;

    struct BloomFilter *bf;
    Data_Get_Struct(self, struct BloomFilter, bf);

    Check_Type(key, T_STRING);
    ckey = STR2CSTR(key);
    len = (int) (RSTRINGLEN(key)); /* length of the string in bytes */

    m = bf->m;
    k = bf->k;
    s = bf->s;

    for (i = 0; i <= k - 1; i++) {
        /* seeds for hash functions */
        seed = i + s;

        /* hash */
        index = (int) (crc32((unsigned int) (seed), ckey, len) % (unsigned int) (m));

        /* check the bit at the index */
        if (!bucket_check(bf, index))
            return Qfalse; /* i.e., it is a new entry ; escape the loop */
    }

    return Qtrue;
}

#insert(key) ⇒ Object 



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# File 'ext/sbloomfilter.c', line 168

static VALUE bf_insert(VALUE self, VALUE key) {
    int index, seed;
    int i, len, m, k, s;
    char *ckey;

    struct BloomFilter *bf;
    Data_Get_Struct(self, struct BloomFilter, bf);

    Check_Type(key, T_STRING);
    ckey = STR2CSTR(key);
    len = (int) (RSTRINGLEN(key)); /* length of the string in bytes */

    m = bf->m;
    k = bf->k;
    s = bf->s;

    for (i = 0; i <= k - 1; i++) {
        /* seeds for hash functions */
        seed = i + s;

        /* hash */
        index = (int) (crc32((unsigned int) (seed), ckey, len) % (unsigned int) (m));

        /*  set a bit at the index */
        bucket_set(bf, index);
    }

    bf->num_set += 1;
    return Qnil;
}

#k ⇒ Object 



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# File 'ext/sbloomfilter.c', line 144

static VALUE bf_k(VALUE self) {
    struct BloomFilter *bf;
    Data_Get_Struct(self, struct BloomFilter, bf);
    return INT2FIX(bf->k);
}

#key?(key) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/bloomfilter.rb', line 24

def key? key
  include?(key)
end

#keys ⇒ Object 



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# File 'lib/bloomfilter.rb', line 28

def keys
  @hash_value.keys
end

#m ⇒ Object 



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# File 'ext/sbloomfilter.c', line 138

static VALUE bf_m(VALUE self) {
    struct BloomFilter *bf;
    Data_Get_Struct(self, struct BloomFilter, bf);
    return INT2FIX(bf->m);
}

#num_set ⇒ Object 



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# File 'ext/sbloomfilter.c', line 162

static VALUE bf_num_set(VALUE self) {
    struct BloomFilter *bf;
    Data_Get_Struct(self, struct BloomFilter, bf);
    return INT2FIX(bf->num_set);
}

#r ⇒ Object 



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# File 'ext/sbloomfilter.c', line 156

static VALUE bf_r(VALUE self) {
    struct BloomFilter *bf;
    Data_Get_Struct(self, struct BloomFilter, bf);
    return bf->r == 0 ? Qfalse : Qtrue;
}

#stats ⇒ Object 



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# File 'lib/bloomfilter.rb', line 4

def stats
  fp = ((1.0 - Math.exp(-(self.k * self.num_set).to_f / self.m)) ** self.k) * 100
  printf "Number of filter buckets (m): %d\n" % self.m
  printf "Number of bits per buckets (b): %d\n" % self.b
  printf "Number of filter elements (n): %d\n" % self.num_set
  printf "Number of filter hashes (k) : %d\n" % self.k
  printf "Raise on overflow? (r) : %s\n" % self.r.to_s
  printf "Predicted false positive rate = %.2f%\n" % fp
end

#to_s ⇒ Object 



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# File 'ext/sbloomfilter.c', line 262

static VALUE bf_to_s(VALUE self) {
    struct BloomFilter *bf;
    unsigned char *ptr;
    int i;
    VALUE str;

    Data_Get_Struct(self, struct BloomFilter, bf);
    str = rb_str_new(0, bf->m);

    ptr = (unsigned char *) RSTRINGPTR(str);
    for (i = 0; i < bf->m; i++)
        *ptr++ = bucket_get(bf, i) ? '1' : '0';

    return str;
}