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<refentry id="tableimix">
<indexterm id="IndexTableimix"><primary>tableimix</primary></indexterm>
<refentryinfo><title>Table Control:Read/Write Opreations</title></refentryinfo>
<refmeta>
<refentrytitle>tableimix</refentrytitle>
</refmeta>
<refnamediv>
<refname>tableimix</refname>
<refpurpose>
Mixes two tables.
</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<para>
Mixes two tables.
</para>
</refsect1>
<refsect1>
<title>Syntax</title>
<synopsis><command>tableimix</command> idft, idoff, ilen, is1ft, is1off, is1g, is2ft, is2off, is2g</synopsis>
</refsect1>
<refsect1>
<title>Initialization</title>
<para>
<emphasis>idft</emphasis> -- Destination function table.
</para>
<para>
<emphasis>idoff</emphasis> -- Offset to start writing from. Can be negative.
</para>
<para>
<emphasis>ilen</emphasis> -- Number of write operations to perform. Negative means work backwards.
</para>
<para>
<emphasis>is1ft</emphasis>, <emphasis>is2ft</emphasis> -- Source function tables. These can be the same as the destination table, if care is exercised about direction of copying data.
</para>
<para>
<emphasis>is1off</emphasis>, <emphasis>is2off</emphasis> -- Offsets to start reading from in source tables.
</para>
<para>
<emphasis>is1g</emphasis>, <emphasis>is2g</emphasis> -- Gains to apply when reading from the source tables. The results are added and the sum is written to the destination table.
</para>
</refsect1>
<refsect1>
<title>Performance</title>
<para>
<emphasis>tableimix</emphasis> -- This opcode mixes from two tables, with separate gains into the destination table. Writing is done for <emphasis>ilen</emphasis> locations, usually stepping forward through the table - if <emphasis>ilen</emphasis> is positive. If it is negative, then the writing and reading order is backwards - towards lower indexes in the tables. This bi-directional option makes it easy to shift the contents of a table sideways by reading from it and writing back to it with a different offset.
</para>
<para>
If <emphasis>ilen</emphasis> is 0, no writing occurs. Note that the internal integer value of <emphasis>ilen</emphasis> is derived from the ANSI C floor() function - which returns the next most negative integer. Hence a fractional negative <emphasis>ilen</emphasis> value of -2.3 would create an internal length of 3, and cause the copying to start from the offset locations and proceed for two locations to the left.
</para>
<para>
The total index for table reading and writing is calculated from the starting offset for each table, plus the index value, which starts at 0 and then increments (or decrements) by 1 as mixing proceeds.
</para>
<para>
These total indexes can potentially be very large, since there is no restriction on the offset or the <emphasis>ilen</emphasis>. However each total index for each table is ANDed with a length mask (such as 0000 0111 for a table of length 8) to form a final index which is actually used for reading or writing. So no reading or writing can occur outside the tables. This is the same as <quote>wrap</quote> mode in table read and write. These opcodes do not read or write the guardpoint. If a table has been rewritten with one of these, then if it has a guardpoint which is supposed to contain the same value as the location 0, then call <link linkend="tableigpw"><citetitle>tableigpw</citetitle></link> afterwards.
</para>
<para>
The indexes and offsets are all in table steps - they are not normalized to 0 - 1. So for a table of length 256, <emphasis>ilen</emphasis> should be set to 256 if all the table was to be read or written.
</para>
<para>
The tables do not need to be the same length - wrapping occurs individually for each table.
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<link linkend="tablecopy"><citetitle>tablecopy</citetitle></link>,
<link linkend="tablegpw"><citetitle>tablegpw</citetitle></link>,
<link linkend="tablemix"><citetitle>tablemix</citetitle></link>,
<link linkend="tableicopy"><citetitle>tableicopy</citetitle></link>,
<link linkend="tableigpw"><citetitle>tableigpw</citetitle></link>
</para>
</refsect1>
<refsect1>
<title>Credits</title>
<para>
<simplelist>
<member>Author: Robin Whittle</member>
<member>Australia</member>
<member>May 1997</member>
</simplelist>
</para>
<para>New in version 3.47</para>
</refsect1>
</refentry>
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