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110 lines
2.5 KiB
C
110 lines
2.5 KiB
C
/*
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* Minimalistic GEOSLib overlay demo program
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*
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* 2012-01-01, Oliver Schmidt (ol.sc@web.de)
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*
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*/
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#include <stdio.h>
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#include <geos.h>
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#include "overlay-demores.h"
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/* Functions resident in an overlay can call back functions resident in the
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* main program at any time without any precautions. The function show() is
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* an example for such a function resident in the main program.
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*/
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void show(char *name)
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{
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char line1[40];
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sprintf(line1, CBOLDON "Overlay Demo - Overlay %s" CPLAINTEXT, name);
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DlgBoxOk(line1,
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"Click OK to return to Main.");
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}
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/* In a real-world overlay program one would probably not use a #pragma but
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* rather place the all the code of certain souce files into the overlay by
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* compiling them with --code-name OVERLAY1.
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*/
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#pragma code-name(push, "OVERLAY1");
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void foo(void)
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{
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/* Functions resident in an overlay can access all program variables and
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* constants at any time without any precautions because those are never
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* placed in overlays. The string constant "One" is an example for such
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* a constant resident in the main program.
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*/
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show("One");
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}
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#pragma code-name(pop);
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#pragma code-name(push, "OVERLAY2");
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void bar(void)
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{
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show("Two");
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}
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#pragma code-name(pop);
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#pragma code-name(push, "OVERLAY3");
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void foobar (void)
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{
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show("Three");
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}
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#pragma code-name(pop);
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void main(int /*argc*/, char *argv[])
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{
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OpenRecordFile(argv[0]);
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DlgBoxOk(CBOLDON "Overlay Demo - Main" CPLAINTEXT,
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"Click OK to call Overlay One.");
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PointRecord(1);
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/* The macro definitions OVERLAY_ADDR and OVERLAY_SIZE were generated in
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* overlay-demores.h by grc65. They contain the overlay area address and
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* size specific to a certain program.
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*/
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ReadRecord(OVERLAY_ADDR, OVERLAY_SIZE);
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/* The linker makes sure that the call to foo() ends up at the right mem
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* addr. However it's up to user to make sure that the - right - overlay
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* is actually loaded before making the the call.
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*/
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foo();
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DlgBoxOk(CBOLDON "Overlay Demo - Main" CPLAINTEXT,
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"Click OK to call Overlay Two.");
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PointRecord(2);
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/* Replacing one overlay with another one can only happen from the main
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* program. This implies that an overlay can never load another overlay.
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*/
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ReadRecord(OVERLAY_ADDR, OVERLAY_SIZE);
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bar();
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DlgBoxOk(CBOLDON "Overlay Demo - Main" CPLAINTEXT,
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"Click OK to call Overlay Three.");
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PointRecord(3);
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ReadRecord(OVERLAY_ADDR, OVERLAY_SIZE);
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foobar();
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CloseRecordFile();
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}
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