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Internal/screen character mapping: Supressed warnings for re-map and added documentation.

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This commit is contained in:
IrgendwerA8 2016-08-27 22:02:08 +02:00
parent 024f66a84f
commit d65f587f69
2 changed files with 59 additions and 1 deletions
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52
doc/atari.sgml
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@ -318,6 +318,58 @@ chip registers.
</descrip><p>
<sect1>Character mapping<p>
The Atari has two representations for characters:
<enum>
<item> ATASCII is character mapping which is similar to ASCII and used
by the CIO system of the OS. This is the default mapping of cc65 when
producing code for the atari target.
<item> The internal/screen mapping represents the real value of the
screen ram when showing a character.
</enum>
For direct memory access (simplicity and speed) enabling the internal
mapping can be useful. This can be achieved by including the
"<tt/atari_screen_charmap.h/" header.
A word of caution: Since the <tt/0x00/ character has to be mapped in an
incompatible way to the C-standard, the usage of string functions in
conjunction with internal character mapped strings delivers unexpected
results regarding the string length. The end of strings are detected where
you may not expect them (to early or (much) to late). Internal mapped
strings typically support the "<tt/mem...()/" functions.
<em>For assembler sources the macro "<tt/scrcode/" from the "<tt/atari.mac/"
package delivers the same feature.</em>
You can switch back to the ATASCII mapping by including
"<tt/atari_atascii_charmap.h/".
A final note: Since cc65 has currently some difficulties with string merging
under different mappings, defining remapped strings works only flawlessly
with static array initialization:
<verb>
#include &lt;atari\_screen\_charmap.h&gt;
char pcScreenMappingString[] = "Hello Atari!";
#include &lt;atari_atascii_charmap.h&gt;
char pcAtasciiMappingString[] = "Hello Atari!";
</verb>
delivers correct results, while
<verb>
#include &lt;atari_screen_charmap.h&gt;
char* pcScreenMappingString = "Hello Atari!";
#include &lt;atari_atascii_charmap.h&gt;
char* pcAtasciiMappingString = "Hello Atari!";
</verb>
does not.
<sect>Loadable drivers<p>

6
include/atari_screen_charmap.h
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@ -30,7 +30,10 @@
/* No include guard here! Multiple use in one file may be intentional. */
#pragma warn (remap-zero, push, off)
#pragma charmap (0x00, 0x40)
#pragma warn (remap-zero, pop)
#pragma charmap (0x01, 0x41)
#pragma charmap (0x02, 0x42)
#pragma charmap (0x03, 0x43)
@ -64,7 +67,10 @@
#pragma charmap (0x1E, 0x5E)
#pragma charmap (0x1F, 0x5F)
#pragma warn (remap-zero, push, off)
#pragma charmap (0x20, 0x00)
#pragma warn (remap-zero, pop)
#pragma charmap (0x21, 0x01)
#pragma charmap (0x22, 0x02)
#pragma charmap (0x23, 0x03)