hashiterator.pmc

/*
Copyright (C) 2001-2011, Parrot Foundation.

=head1 NAME

src/pmc/hashiterator.pmc - Implementation of Iterator for Hashes.

=head1 DESCRIPTION

Generic iterator for traversing Hash.

=head1 SYNOPSIS

=head2 default usage

    .local pmc iterator, hash, key, entry
    iterator = iter hash
  iter_loop:
    unless iterator, iter_end  # while (more values)
    key   = shift iterator     # get the key. Some key
    entry = hash[key]
    ...
    goto iter_loop
  iter_end:

=head2 C++-style usage

    .local pmc iterator, hash, iter_key, key, entry
    iterator = iter hash
  iter_loop:
    unless iterator, iter_end  # while (more values)
    iter_key = shift iterator     # get the key
    key = iter_key.'key'()        # get an original key used to put value
    key = iter_key.'value'()      # get an entry
    ...
    goto iter_loop
  iter_end:


=head1 Methods

=over 4

=cut

*/

#include "pmc/pmc_hash.h"
#include "pmc/pmc_hashiteratorkey.h"

/* HEADERIZER HFILE: none */
/* HEADERIZER BEGIN: static */
/* Don't modify between HEADERIZER BEGIN / HEADERIZER END.  Your changes will be lost. */

static void advance_to_next(ARGMOD(PMC *self))
        __attribute__nonnull__(1)
        FUNC_MODIFIES(*self);

#define ASSERT_ARGS_advance_to_next __attribute__unused__ int _ASSERT_ARGS_CHECK = (\
       PARROT_ASSERT_ARG(self))
/* Don't modify between HEADERIZER BEGIN / HEADERIZER END.  Your changes will be lost. */
/* HEADERIZER END: static */

/*

=item C<static void advance_to_next(PMC *self)>

Advance to next position. Return found (if any) HashBucket.

=cut

*/

static void
advance_to_next(ARGMOD(PMC *self))
{
    ASSERT_ARGS(advance_to_next)
    Parrot_HashIterator_attributes * const attrs  = PARROT_HASHITERATOR(self);

    if (attrs->elements <= 0) {
        attrs->elements = -1;
        return;
    }

    if (attrs->parrot_hash->key_type == Hash_key_type_int
    ||  attrs->parrot_hash->key_type == Hash_key_type_ptr
    ||  attrs->parrot_hash->key_type == Hash_key_type_cstring) {
        /* indexed scan */
        if (attrs->bucket)
            attrs->bucket = attrs->bucket->next;
        while (!attrs->bucket) {
            /* Check pos overflow, can happen if items are deleted */
            if (attrs->pos == attrs->total_buckets) {
                attrs->elements = 0;
                break;
            }
            attrs->bucket = attrs->parrot_hash->index[attrs->pos++];
        }
    }
    else {
        /* linear scan */
        const int n_buckets = N_BUCKETS(attrs->total_buckets);

        if (!attrs->bucket)
            attrs->bucket = attrs->parrot_hash->buckets;
        while (attrs->pos < n_buckets) {
            attrs->bucket = attrs->parrot_hash->buckets + attrs->pos++;
            if (attrs->bucket->key)
                break;
        }
        /* Can happen if items are deleted */
        if (!attrs->bucket->key)
            attrs->elements = 0;
    }

    --attrs->elements;

    return;
}

pmclass HashIterator extends Iterator no_ro auto_attrs {
    ATTR PMC        *pmc_hash;      /* the Hash which this Iterator iterates */
    ATTR Hash       *parrot_hash;   /* Underlying implementation of hash */
    ATTR HashBucket *bucket;        /* Current bucket */
    ATTR INTVAL      total_buckets; /* Total buckets in index */
    ATTR INTVAL      pos;           /* Current position in index */
    ATTR INTVAL      elements;      /* How many elements left to iterate over */

/*

=item C<void init_pmc(PMC *initializer)>

Initializes the iterator with an aggregate PMC.
Defaults iteration mode to iterate from start.

=cut

*/

    VTABLE void init_pmc(PMC *hash) {
        Parrot_HashIterator_attributes * const attrs =
            (Parrot_HashIterator_attributes *) PMC_data(SELF);

        attrs->pmc_hash         = hash;
        attrs->parrot_hash      = (Hash*)VTABLE_get_pointer(INTERP, hash);
        attrs->total_buckets    = attrs->parrot_hash->mask + 1;
        attrs->elements         = attrs->parrot_hash->entries;
        attrs->bucket           = NULL;
        attrs->pos              = 0;

        PObj_custom_mark_SET(SELF);
    }

/*

=item C<void mark()>

Marks the hash as live.

=cut

*/

    VTABLE void mark() {
        PMC * const hash = PARROT_HASHITERATOR(SELF)->pmc_hash;
        Parrot_gc_mark_PMC_alive(INTERP, hash);
        /* We don't mark underlying parrot_hash. Hash PMC will mark it */
    }

/*

=item C<PMC *clone()>

=cut

*/
    VTABLE PMC* clone() {
        return PMCNULL;
    }

/*

=item C<void set_integer_native()>

=cut

*/
    VTABLE void set_integer_native(INTVAL value) {
        Parrot_HashIterator_attributes * const attrs =
                PARROT_HASHITERATOR(SELF);

        if (value == ITERATE_FROM_START) {
            /* Restart iterator */
            attrs->elements         = attrs->parrot_hash->entries;
            attrs->bucket           = NULL;
            attrs->pos              = 0;
            return;
        }

        Parrot_ex_throw_from_c_args(INTERP, NULL, EXCEPTION_INVALID_OPERATION,
                "HashIterator: unknown iterator type");
    };

/*

=item C<PMC *get_pmc()>

Returns this Iterator's Hash.

=cut

*/
    VTABLE PMC* get_pmc() {
        return PARROT_HASHITERATOR(SELF)->pmc_hash;
    }

/*

=item C<INTVAL get_bool()>

Returns true if there is more elements to iterate over.

=cut

*/

    VTABLE INTVAL get_bool() {
        return PARROT_HASHITERATOR(SELF)->elements != 0;

    }

/*

=item C<INTVAL elements()>

Returns the number of remaining elements in the Hash.

=cut

*/

    VTABLE INTVAL elements() {
        return PARROT_HASHITERATOR(SELF)->elements;
    }

    VTABLE INTVAL get_integer() {
        return PARROT_HASHITERATOR(SELF)->elements;
    }

/*

=item C<PMC *shift_pmc()>

Returns the HashIteratorKey for the current position and advance
the next one.

=cut

*/

    VTABLE PMC *shift_pmc() {
        Parrot_HashIterator_attributes * const attrs =
                PARROT_HASHITERATOR(SELF);

        PMC        *ret;

        /* Move to next bucket */
        advance_to_next(SELF);

        if (attrs->elements < 0)
            Parrot_ex_throw_from_c_args(INTERP, NULL, EXCEPTION_OUT_OF_BOUNDS,
                "StopIteration");

        ret = Parrot_pmc_new(INTERP, enum_class_HashIteratorKey);
        VTABLE_set_pointer_keyed_int(INTERP, ret, 0, attrs->parrot_hash);
        VTABLE_set_pointer_keyed_int(INTERP, ret, 1, attrs->bucket);

        return ret;
    }

/*

*/

    VTABLE STRING* shift_string() {
        Parrot_HashIterator_attributes * const attrs = PARROT_HASHITERATOR(SELF);

        /* Move to next bucket */
        advance_to_next(SELF);

        if (attrs->elements < 0)
            return CONST_STRING(INTERP, "");

        return Parrot_hash_key_to_string(INTERP, attrs->parrot_hash, attrs->bucket->key);
    }

}

/*

=back

=cut

*/

/*
 * Local variables:
 *   c-file-style: "parrot"
 * End:
 * vim: expandtab shiftwidth=4 cinoptions='\:2=2' :
 */