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Correct get_floating_value to be consistent in out-of-bounds behaviour.

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Thomas Harte 2021-04-15 21:13:36 -04:00
parent 349b9ce502
commit fa18b06dbf
1 changed files with 9 additions and 5 deletions
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14
Machines/Sinclair/ZXSpectrum/Video.hpp
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@ -401,20 +401,24 @@ template <VideoTiming timing> class Video {
*/ */
uint8_t get_floating_value() const { uint8_t get_floating_value() const {
constexpr auto timings = get_timings(); constexpr auto timings = get_timings();
const uint8_t out_of_bounds = (timing == VideoTiming::Plus3) ? last_contended_access_ : 0xff;
const int line = time_into_frame_ / timings.cycles_per_line; const int line = time_into_frame_ / timings.cycles_per_line;
if(line >= 192) return 0xff; if(line >= 192) {
return out_of_bounds;
}
const int time_into_line = time_into_frame_ % timings.cycles_per_line; const int time_into_line = time_into_frame_ % timings.cycles_per_line;
if(time_into_line >= 256 || (time_into_line&8)) { if(time_into_line >= 256 || (time_into_line&8)) {
return last_contended_access_; return out_of_bounds;
} }
// The +2a and +3 always return the low bit as set. // The +2a and +3 always return the low bit as set.
const uint8_t value = last_fetches_[(time_into_line >> 1) & 3];
if constexpr (timing == VideoTiming::Plus3) { if constexpr (timing == VideoTiming::Plus3) {
return last_fetches_[(time_into_line >> 1) & 3] | 1; return value | 1;
} }
return value;
return last_fetches_[(time_into_line >> 1) & 3];
} }
/*! /*!