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Overview
Variable Length Fields
FlexFile is a very focused dual purpose tool kit for Clipper
programmers. Its first and main purpose is to provide a
complete replacement for Clipper's memo-fields with a more
powerful and more efficient Variable Length Field engine. We
are certain that it will relieve you of the confinement
imposed by Clipper's memo-fields, but also, we believe it may
change the way you think about your data base structures in
general.
FlexFile was designed to be immediately familiar to the
Clipper programmer. To accomplish this goal, many of the
function names can only be distinguished from their Clipper
counterpart by a V_ prefix. For example, V_USE() opens a DBV
file in the currently V_SELECT()ed work area.
The similarities extend into the structural use of FlexFile's
Variable Length Fields (VLF) as well. FlexFile's version of a
memo-field (which we will refer to as a pointer-field) is a
six byte character type field in a DBF file. FlexFile uses
this pointer-field to store a pointer to variable length data
in a .DBV file (FlexFile's version of a .DBT file). These
similarities allow any Clipper REPLACE syntax which works on
memo-fields to remain almost unchanged when used with
FlexFile. This claim carries in network environments as well.
The benefits and use of FlexFile's Variable Length Fields are
discussed in detail in the Reference "Variable Length Fields".
Pay special attention to the section on FlexFile's extended
features.
Arrays
FlexFile's strongly typed arrays provide a utility which defy
the products name. Instead of being flexible, these arrays
are purposefully rigid. The utility of these arrays is
twofold. First and foremost, they use far less space than
their Clipper counterpart. For example, any Clipper array of
1,000 elements would require a minimum of 14,000 bytes from
Clipper's free pool of memory. A FlexFile array of 1,000
integers, on the other hand, would require only 2,000 bytes
from Clipper's free pool of memory.
Typically, large strongly typed arrays are used for scientific
or statistical matrixes. For this reason, FlexFile provides a
host of functions which globally manipulate or query these
large arrays.
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