phpman > man > Tie::SubstrHash(3pm)

NAME
    Tie::SubstrHash - Fixed-table-size, fixed-key-length hashing

SYNOPSIS
        require Tie::SubstrHash;

        tie %myhash, 'Tie::SubstrHash', $key_len, $value_len, $table_size;

DESCRIPTION
    The Tie::SubstrHash package provides a hash-table-like interface to an array of determinate
    size, with constant key size and record size.

    Upon tying a new hash to this package, the developer must specify the size of the keys that will
    be used, the size of the value fields that the keys will index, and the size of the overall
    table (in terms of key-value pairs, not size in hard memory). *These values will not change for
    the duration of the tied hash*. The newly-allocated hash table may now have data stored and
    retrieved. Efforts to store more than $table_size elements will result in a fatal error, as will
    efforts to store a value not exactly $value_len characters in length, or reference through a key
    not exactly $key_len characters in length. While these constraints may seem excessive, the
    result is a hash table using much less internal memory than an equivalent freely-allocated hash
    table.

CAVEATS
    Because the current implementation uses the table and key sizes for the hashing algorithm, there
    is no means by which to dynamically change the value of any of the initialization parameters.

    The hash does not support exists().