103 lines
6.6 KiB
HTML
103 lines
6.6 KiB
HTML
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<meta name="DC.Title" content="%OFFSET built-in function" />
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<meta name="abstract" content="The offset built-in function (%OFFSET or %OFS) can be used to store or change the offset portion of a CL pointer variable and can only be used within a CL procedure." />
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<meta name="description" content="The offset built-in function (%OFFSET or %OFS) can be used to store or change the offset portion of a CL pointer variable and can only be used within a CL procedure." />
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<title>%OFFSET built-in function</title>
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</head>
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<body id="rbam6offset"><a name="rbam6offset"><!-- --></a>
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<img src="./delta.gif" alt="Start of change" /><!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">%OFFSET built-in function</h1>
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<div><p>The offset built-in function (%OFFSET or %OFS) can be used to store
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or change the offset portion of a CL pointer variable and can only be used
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within a CL procedure.</p>
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<div class="section"><div class="p">In a CHGVAR command, the %OFFSET function can be used two different
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ways: <ul><li>You can specify the %OFFSET function for the variable (VAR
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parameter) to set the offset portion of a pointer variable.</li>
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<li>You can specify the %OFFSET function for the value (VALUE parameter) to
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which the variable is to be changed.</li>
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</ul>
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In an IF command, the %OFFSET function can be specified in the expression
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(COND parameter) and is treated like a four-byte unsigned integer value.</div>
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<div class="p">The
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format of the offset built-in function is:<pre>%OFFSET(variable name)</pre>
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or<pre>%OFS(variable name)</pre>
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</div>
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<p>In
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the following example, pointer variable &P1 has no initial value specified
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and therefore is initialized to null. The first CHGVAR will store the offset
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from the null pointer value in integer variable &I1; the command will
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run without an error, and the value of &I1 will probably be zero, though
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the offset for a null pointer is not defined. The second CHGVAR command
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sets &P1 to the address of local character variable &C1; pointer &P1
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now points to byte 1 of variable &C1. The third CHGVAR command will store
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the offset portion of &P1 into the integer variable &I2. Note that
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the offset is from the start of the storage for all automatic variables for
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the current thread and not from the start of automatic storage for the current
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program or from the start of variable &C1. The fourth CHGVAR command
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takes the integer value stored in &I2, adds one hundred, and stores the
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resulting number into the integer variable &I3. The fifth CHGVAR command
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changes the offset portion of pointer &P1 using integer variable &I3;
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pointer &P1 now points to byte 101 of variable &C1. The sixth CHGVAR
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command will calculate the integer expression for the VALUE parameter by storing
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the offset portion of pointer &P1 into a temporary integer variable and
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subtracting 20, and use this calculated value to reset the offset portion
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of pointer &P1; pointer &P1 now points to byte 81 of variable &C1.</p>
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<pre>PGM
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DCL &C1 *CHAR 30000
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DCL &P1 *PTR
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DCL &P2 *PTR
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DCL &I1 *UINT 4
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DCL &I2 *UINT 4
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DCL &I3 *UINT 4
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CHGVAR &I1 %OFFSET(&P1) /* 1 */
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CHGVAR &P1 %ADDRESS(&C1) /* 2 */
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CHGVAR &I2 %OFFSET(&P1) /* 3 */
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CHGVAR &I3 (%I2+100) /* 4 */
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CHGVAR %OFFSET(&P1) &I3 /* 5 */
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CHGVAR %OFFSET(&P1) (%OFFSET(&P1)-20) /* 6 */
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ENDPGM</pre>
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The %OFFSET built-in function cannot be used with a pointer variable
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that addresses teraspace storage.</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="contp.htm" title="You can use commands to change the flow of logic within your CL procedure.">Control processing within a CL procedure</a></div>
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</div>
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<div class="reltasks"><strong>Related tasks</strong><br />
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<div><a href="valuv.htm" title="You can change the value of a CL variable using the Change Variable (CHGVAR) command.">Change the value of a variable</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="rbam6builtinfunc.htm" title="CL provides several built-in functions.">Built-in functions for CL</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="../clfinder/finder.htm">CL command finder</a></div>
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<div><a href="../cl/chgvar.htm">Change Variable (CHGVAR) command</a></div>
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</div>
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</div>
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<img src="./deltaend.gif" alt="End of change" /></body>
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</html>
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