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Moved to the maximum possibly required queue length of 4. Though the emulated 2600 should never need more than 2 slots as per the current calling pattern, it's not a contractual guarantee.

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This commit is contained in:
Thomas Harte 2017-02-25 17:25:10 -05:00
parent c898c8a99e
commit e61e355251
1 changed files with 24 additions and 10 deletions
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34
Machines/Atari2600/TIA.hpp
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@ -150,7 +150,7 @@ class TIA {
// player state // player state
struct Player: public Object<Player> { struct Player: public Object<Player> {
Player() : copy_flags(0), graphic{0, 0}, reverse_mask(false), pixel_position(32), graphic_index(0), adder(4) {} Player() : copy_flags(0), graphic{0, 0}, reverse_mask(false), pixel_position(32), graphic_index(0), adder(4), queue_read_pointer_(0), queue_write_pointer_(0) {}
int adder; int adder;
int copy_flags; // a bit field, corresponding to the first few values of NUSIZ int copy_flags; // a bit field, corresponding to the first few values of NUSIZ
@ -179,20 +179,33 @@ class TIA {
void dequeue_pixels(uint8_t *const target, const uint8_t collision_identity, const int time_now) void dequeue_pixels(uint8_t *const target, const uint8_t collision_identity, const int time_now)
{ {
if(queue_.start != queue_.end) while(queue_read_pointer_ != queue_write_pointer_)
{ {
output_pixels(&target[queue_.start], queue_.end - queue_.start, collision_identity, queue_.pixel_position, queue_.adder, queue_.reverse_mask); uint8_t *const start_ptr = &target[queue_[queue_read_pointer_].start];
queue_.start = queue_.end; if(queue_[queue_read_pointer_].end > time_now)
{
const int length = time_now - queue_[queue_read_pointer_].start;
output_pixels(start_ptr, length, collision_identity, queue_[queue_read_pointer_].pixel_position, queue_[queue_read_pointer_].adder, queue_[queue_read_pointer_].reverse_mask);
queue_[queue_read_pointer_].pixel_position += length * queue_[queue_read_pointer_].adder;
queue_[queue_read_pointer_].start = time_now;
return;
}
else
{
output_pixels(start_ptr, queue_[queue_read_pointer_].end - queue_[queue_read_pointer_].start, collision_identity, queue_[queue_read_pointer_].pixel_position, queue_[queue_read_pointer_].adder, queue_[queue_read_pointer_].reverse_mask);
}
queue_read_pointer_ = (queue_read_pointer_ + 1)&3;
} }
} }
void enqueue_pixels(const int start, const int end) void enqueue_pixels(const int start, const int end)
{ {
queue_.start = start; queue_[queue_write_pointer_].start = start;
queue_.end = end; queue_[queue_write_pointer_].end = end;
queue_.pixel_position = pixel_position; queue_[queue_write_pointer_].pixel_position = pixel_position;
queue_.adder = adder; queue_[queue_write_pointer_].adder = adder;
queue_.reverse_mask = reverse_mask; queue_[queue_write_pointer_].reverse_mask = reverse_mask;
queue_write_pointer_ = (queue_write_pointer_ + 1)&3;
skip_pixels(end - start); skip_pixels(end - start);
} }
@ -203,7 +216,8 @@ class TIA {
int pixel_position; int pixel_position;
int adder; int adder;
int reverse_mask; int reverse_mask;
} queue_; } queue_[4];
int queue_read_pointer_, queue_write_pointer_;
inline void output_pixels(uint8_t *const target, const int count, const uint8_t collision_identity, int pixel_position, int adder, int reverse_mask) inline void output_pixels(uint8_t *const target, const int count, const uint8_t collision_identity, int pixel_position, int adder, int reverse_mask)
{ {