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Give clearer names to the two pointers.

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This commit is contained in:
Thomas Harte 2023-01-20 20:29:15 -05:00
parent 392b0acb58
commit 9b7a925816
4 changed files with 77 additions and 77 deletions
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98
Components/9918/Implementation/9918.cpp
View File

@ -39,10 +39,10 @@ Base<personality>::Base() :
// Establish that output is delayed after reading by `output_lag` cycles; start
// at a random position.
read_pointer_.row = rand() % 262;
read_pointer_.column = rand() % (Timing<personality>::CyclesPerLine - output_lag);
write_pointer_.row = read_pointer_.row;
write_pointer_.column = read_pointer_.column + output_lag;
fetch_pointer_.row = rand() % 262;
fetch_pointer_.column = rand() % (Timing<personality>::CyclesPerLine - output_lag);
output_pointer_.row = output_pointer_.row;
output_pointer_.column = output_pointer_.column + output_lag;
}
template <Personality personality>
@ -155,20 +155,20 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
while(write_cycles_pool || read_cycles_pool) {
#ifndef NDEBUG
LineBufferPointer backup = this->read_pointer_;
LineBufferPointer backup = this->output_pointer_;
#endif
if(write_cycles_pool) {
// Determine how much writing to do.
const int write_cycles = std::min(
Timing<personality>::CyclesPerLine - this->write_pointer_.column,
Timing<personality>::CyclesPerLine - this->fetch_pointer_.column,
write_cycles_pool
);
const int end_column = this->write_pointer_.column + write_cycles;
LineBuffer &line_buffer = this->line_buffers_[this->write_pointer_.row];
const int end_column = this->fetch_pointer_.column + write_cycles;
LineBuffer &line_buffer = this->line_buffers_[this->fetch_pointer_.row];
// Determine what this does to any enqueued VRAM access.
this->minimum_access_column_ = this->write_pointer_.column + this->cycles_until_access_;
this->minimum_access_column_ = this->fetch_pointer_.column + this->cycles_until_access_;
this->cycles_until_access_ -= write_cycles;
@ -176,8 +176,8 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
// Latch scrolling position, if necessary.
// ---------------------------------------
if constexpr (is_sega_vdp(personality)) {
if(this->write_pointer_.column < 61 && end_column >= 61) {
if(!this->write_pointer_.row) {
if(this->fetch_pointer_.column < 61 && end_column >= 61) {
if(!this->fetch_pointer_.row) {
Storage<personality>::latched_vertical_scroll_ = Storage<personality>::vertical_scroll_;
if(Storage<personality>::mode4_enable_) {
@ -201,7 +201,7 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
// Perform memory accesses.
// ------------------------
#define fetch(function, clock) \
const int first_window = from_internal<personality, clock>(this->write_pointer_.column);\
const int first_window = from_internal<personality, clock>(this->fetch_pointer_.column);\
const int final_window = from_internal<personality, clock>(end_column); \
if(first_window == final_window) break; \
if(final_window != clock_rate<personality, clock>()) { \
@ -224,12 +224,12 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
// -------------------------------
// Check for interrupt conditions.
// -------------------------------
if(this->write_pointer_.column < this->mode_timing_.line_interrupt_position && end_column >= this->mode_timing_.line_interrupt_position) {
if(this->fetch_pointer_.column < this->mode_timing_.line_interrupt_position && end_column >= this->mode_timing_.line_interrupt_position) {
// The Sega VDP offers a decrementing counter for triggering line interrupts;
// it is reloaded either when it overflows or upon every non-pixel line after the first.
// It is otherwise decremented.
if constexpr (is_sega_vdp(personality)) {
if(this->write_pointer_.row >= 0 && this->write_pointer_.row <= this->mode_timing_.pixel_lines) {
if(this->fetch_pointer_.row >= 0 && this->fetch_pointer_.row <= this->mode_timing_.pixel_lines) {
--this->line_interrupt_counter_;
if(this->line_interrupt_counter_ == 0xff) {
this->line_interrupt_pending_ = true;
@ -245,8 +245,8 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
}
if(
this->write_pointer_.row == this->mode_timing_.end_of_frame_interrupt_position.row &&
this->write_pointer_.column < this->mode_timing_.end_of_frame_interrupt_position.column &&
this->fetch_pointer_.row == this->mode_timing_.end_of_frame_interrupt_position.row &&
this->fetch_pointer_.column < this->mode_timing_.end_of_frame_interrupt_position.column &&
end_column >= this->mode_timing_.end_of_frame_interrupt_position.column
) {
this->status_ |= StatusInterrupt;
@ -257,13 +257,13 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
// -------------
// Advance time.
// -------------
this->write_pointer_.column = end_column;
this->fetch_pointer_.column = end_column;
write_cycles_pool -= write_cycles;
if(this->write_pointer_.column == Timing<personality>::CyclesPerLine) {
this->write_pointer_.column = 0;
this->write_pointer_.row = (this->write_pointer_.row + 1) % this->mode_timing_.total_lines;
LineBuffer &next_line_buffer = this->line_buffers_[this->write_pointer_.row];
if(this->fetch_pointer_.column == Timing<personality>::CyclesPerLine) {
this->fetch_pointer_.column = 0;
this->fetch_pointer_.row = (this->fetch_pointer_.row + 1) % this->mode_timing_.total_lines;
LineBuffer &next_line_buffer = this->line_buffers_[this->fetch_pointer_.row];
// Establish the current screen output mode, which will be captured as a
// line mode momentarily.
@ -292,22 +292,22 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
if(
(this->screen_mode_ == ScreenMode::Blank) ||
(this->write_pointer_.row >= this->mode_timing_.pixel_lines && this->write_pointer_.row != this->mode_timing_.total_lines-1))
(this->fetch_pointer_.row >= this->mode_timing_.pixel_lines && this->fetch_pointer_.row != this->mode_timing_.total_lines-1))
next_line_buffer.line_mode = LineMode::Refresh;
}
}
#ifndef NDEBUG
assert(backup.row == this->read_pointer_.row && backup.column == this->read_pointer_.column);
backup = this->write_pointer_;
assert(backup.row == this->output_pointer_.row && backup.column == this->output_pointer_.column);
backup = this->fetch_pointer_;
#endif
if(read_cycles_pool) {
// Determine how much time has passed in the remainder of this line, and proceed.
const int target_read_cycles = std::min(
Timing<personality>::CyclesPerLine - this->read_pointer_.column,
Timing<personality>::CyclesPerLine - this->output_pointer_.column,
read_cycles_pool
);
int read_cycles_performed = 0;
@ -322,8 +322,8 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
if constexpr (is_sega_vdp(personality)) {
next_cram_value = 0;
if(!this->upcoming_cram_dots_.empty() && this->upcoming_cram_dots_.front().location.row == this->read_pointer_.row) {
int time_until_dot = this->upcoming_cram_dots_.front().location.column - this->read_pointer_.column;
if(!this->upcoming_cram_dots_.empty() && this->upcoming_cram_dots_.front().location.row == this->output_pointer_.row) {
int time_until_dot = this->upcoming_cram_dots_.front().location.column - this->output_pointer_.column;
if(time_until_dot < read_cycles) {
read_cycles = time_until_dot;
@ -335,8 +335,8 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
read_cycles_performed += read_cycles;
const int end_column = this->read_pointer_.column + read_cycles;
LineBuffer &line_buffer = this->line_buffers_[this->read_pointer_.row];
const int end_column = this->output_pointer_.column + read_cycles;
LineBuffer &line_buffer = this->line_buffers_[this->output_pointer_.row];
// --------------------
@ -349,7 +349,7 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
#define output_default_colour_burst(x) crt_convert(output_default_colour_burst, x)
#define intersect(left, right, code) { \
const int start = std::max(this->read_pointer_.column, left); \
const int start = std::max(this->output_pointer_.column, left); \
const int end = std::min(end_column, right); \
if(end > start) {\
code;\
@ -358,10 +358,10 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
#define border(left, right) intersect(left, right, this->output_border(end - start, cram_value))
if(line_buffer.line_mode == LineMode::Refresh || this->read_pointer_.row > this->mode_timing_.pixel_lines) {
if(line_buffer.line_mode == LineMode::Refresh || this->output_pointer_.row > this->mode_timing_.pixel_lines) {
if(
this->read_pointer_.row >= this->mode_timing_.first_vsync_line &&
this->read_pointer_.row < this->mode_timing_.first_vsync_line + 4
this->output_pointer_.row >= this->mode_timing_.first_vsync_line &&
this->output_pointer_.row < this->mode_timing_.first_vsync_line + 4
) {
// Vertical sync.
// TODO: the Mega Drive supports interlaced video, I think?
@ -375,7 +375,7 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
// Blanking region: output the entire sequence when the cursor
// crosses the start-of-border point.
if(
this->read_pointer_.column < Timing<personality>::StartOfLeftBorder &&
this->output_pointer_.column < Timing<personality>::StartOfLeftBorder &&
end_column >= Timing<personality>::StartOfLeftBorder
) {
output_blank(Timing<personality>::StartOfSync - Timing<personality>::EndOfRightBorder);
@ -394,7 +394,7 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
// Blanking region.
if(
this->read_pointer_.column < Timing<personality>::StartOfLeftBorder &&
this->output_pointer_.column < Timing<personality>::StartOfLeftBorder &&
end_column >= Timing<personality>::StartOfLeftBorder
) {
output_blank(Timing<personality>::StartOfSync - Timing<personality>::EndOfRightBorder);
@ -464,17 +464,17 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
// -------------
// Advance time.
// -------------
this->read_pointer_.column = end_column;
this->output_pointer_.column = end_column;
}
read_cycles_pool -= target_read_cycles;
if(this->read_pointer_.column == Timing<personality>::CyclesPerLine) {
this->read_pointer_.column = 0;
this->read_pointer_.row = (this->read_pointer_.row + 1) % this->mode_timing_.total_lines;
if(this->output_pointer_.column == Timing<personality>::CyclesPerLine) {
this->output_pointer_.column = 0;
this->output_pointer_.row = (this->output_pointer_.row + 1) % this->mode_timing_.total_lines;
}
}
assert(backup.row == this->write_pointer_.row && backup.column == this->write_pointer_.column);
assert(backup.row == this->fetch_pointer_.row && backup.column == this->fetch_pointer_.column);
}
}
@ -776,9 +776,9 @@ uint8_t TMS9918<personality>::get_current_line() const {
// Determine the row to return.
constexpr int row_change_position = 63; // This is the proper Master System value; substitute if any other VDPs turn out to have this functionality.
int source_row =
(this->write_pointer_.column < row_change_position)
? (this->write_pointer_.row + this->mode_timing_.total_lines - 1) % this->mode_timing_.total_lines
: this->write_pointer_.row;
(this->fetch_pointer_.column < row_change_position)
? (this->fetch_pointer_.row + this->mode_timing_.total_lines - 1) % this->mode_timing_.total_lines
: this->fetch_pointer_.row;
if(this->tv_standard_ == TVStandard::NTSC) {
if(this->mode_timing_.pixel_lines == 240) {
@ -815,7 +815,7 @@ HalfCycles TMS9918<personality>::get_next_sequence_point() const {
int time_until_frame_interrupt =
(
((this->mode_timing_.end_of_frame_interrupt_position.row * Timing<personality>::CyclesPerLine) + this->mode_timing_.end_of_frame_interrupt_position.column + frame_length) -
((this->write_pointer_.row * Timing<personality>::CyclesPerLine) + this->write_pointer_.column)
((this->fetch_pointer_.row * Timing<personality>::CyclesPerLine) + this->fetch_pointer_.column)
) % frame_length;
if(!time_until_frame_interrupt) time_until_frame_interrupt = frame_length;
@ -826,8 +826,8 @@ HalfCycles TMS9918<personality>::get_next_sequence_point() const {
// Calculate when the next line interrupt will occur.
int next_line_interrupt_row = -1;
int cycles_to_next_interrupt_threshold = this->mode_timing_.line_interrupt_position - this->write_pointer_.column;
int line_of_next_interrupt_threshold = this->write_pointer_.row;
int cycles_to_next_interrupt_threshold = this->mode_timing_.line_interrupt_position - this->fetch_pointer_.column;
int line_of_next_interrupt_threshold = this->fetch_pointer_.row;
if(cycles_to_next_interrupt_threshold <= 0) {
cycles_to_next_interrupt_threshold += Timing<personality>::CyclesPerLine;
++line_of_next_interrupt_threshold;
@ -866,8 +866,8 @@ template <Personality personality>
HalfCycles TMS9918<personality>::get_time_until_line(int line) {
if(line < 0) line += this->mode_timing_.total_lines;
int cycles_to_next_interrupt_threshold = this->mode_timing_.line_interrupt_position - this->write_pointer_.column;
int line_of_next_interrupt_threshold = this->write_pointer_.row;
int cycles_to_next_interrupt_threshold = this->mode_timing_.line_interrupt_position - this->fetch_pointer_.column;
int line_of_next_interrupt_threshold = this->fetch_pointer_.row;
if(cycles_to_next_interrupt_threshold <= 0) {
cycles_to_next_interrupt_threshold += Timing<personality>::CyclesPerLine;
++line_of_next_interrupt_threshold;
@ -900,7 +900,7 @@ template <Personality personality>uint8_t TMS9918<personality>::get_latched_hori
template <Personality personality>
void TMS9918<personality>::latch_horizontal_counter() {
this->latched_column_ = this->write_pointer_.column;
this->latched_column_ = this->fetch_pointer_.column;
}
template class TI::TMS::TMS9918<Personality::TMS9918A>;

6
Components/9918/Implementation/9918Base.hpp
View File

@ -300,7 +300,7 @@ template <Personality personality> struct Base: public Storage<personality> {
// to update sprites and tiles, but writing time affects when the palette is used and when the collision flag
// may end up being set. So the two processes are slightly decoupled. The end of reading one line may overlap
// with the beginning of writing the next, hence the two separate line buffers.
LineBufferPointer read_pointer_, write_pointer_;
LineBufferPointer output_pointer_, fetch_pointer_;
int masked_address(int address);
void write_vram(uint8_t);
@ -370,8 +370,8 @@ template <Personality personality> struct Base: public Storage<personality> {
// on screen. So it's wherever the output stream would be now. Which
// is output_lag cycles ago from the point of view of the input stream.
auto &dot = Storage<personality>::upcoming_cram_dots_.emplace_back();
dot.location.column = write_pointer_.column - output_lag;
dot.location.row = write_pointer_.row;
dot.location.column = fetch_pointer_.column - output_lag;
dot.location.row = fetch_pointer_.row;
// Handle before this row conditionally; then handle after (or, more realistically,
// exactly at the end of) naturally.

8
Components/9918/Implementation/Draw.hpp
View File

@ -13,7 +13,7 @@
template <Personality personality>
void Base<personality>::draw_tms_character(int start, int end) {
LineBuffer &line_buffer = line_buffers_[read_pointer_.row];
LineBuffer &line_buffer = line_buffers_[output_pointer_.row];
// Paint the background tiles.
const int pixels_left = end - start;
@ -106,7 +106,7 @@ void Base<personality>::draw_tms_character(int start, int end) {
template <Personality personality>
void Base<personality>::draw_tms_text(int start, int end) {
LineBuffer &line_buffer = line_buffers_[read_pointer_.row];
LineBuffer &line_buffer = line_buffers_[output_pointer_.row];
const uint32_t colours[2] = { palette[background_colour_], palette[text_colour_] };
const int shift = start % 6;
@ -135,7 +135,7 @@ template <Personality personality>
void Base<personality>::draw_sms(int start, int end, uint32_t cram_dot) {
if constexpr (is_sega_vdp(personality)) {
LineBuffer &line_buffer = line_buffers_[read_pointer_.row];
LineBuffer &line_buffer = line_buffers_[output_pointer_.row];
int colour_buffer[256];
/*
@ -143,7 +143,7 @@ void Base<personality>::draw_sms(int start, int end, uint32_t cram_dot) {
*/
int tile_start = start, tile_end = end;
int tile_offset = start;
if(read_pointer_.row >= 16 || !Storage<personality>::horizontal_scroll_lock_) {
if(output_pointer_.row >= 16 || !Storage<personality>::horizontal_scroll_lock_) {
for(int c = start; c < (line_buffer.latched_horizontal_scroll & 7); ++c) {
colour_buffer[c] = 16 + background_colour_;
++tile_offset;

42
Components/9918/Implementation/Fetch.hpp
View File

@ -139,9 +139,9 @@ template<bool use_end> void Base<personality>::fetch_tms_text(int start, int end
fetch_columns_4(location, column); \
fetch_columns_4(location+12, column+4);
LineBuffer &line_buffer = line_buffers_[write_pointer_.row];
const size_t row_base = pattern_name_address_ & (0x3c00 | size_t(write_pointer_.row >> 3) * 40);
const size_t row_offset = pattern_generator_table_address_ & (0x3800 | (write_pointer_.row & 7));
LineBuffer &line_buffer = line_buffers_[fetch_pointer_.row];
const size_t row_base = pattern_name_address_ & (0x3c00 | size_t(fetch_pointer_.row >> 3) * 40);
const size_t row_offset = pattern_generator_table_address_ & (0x3800 | (fetch_pointer_.row & 7));
switch(start) {
default: assert(false);
@ -210,7 +210,7 @@ template<bool use_end> void Base<personality>::fetch_tms_character(int start, in
sprite_fetch_graphics(location+2, sprite)
#define sprite_y_read(location, sprite) \
slot(location): posit_sprite(sprite_selection_buffer, sprite, ram_[sprite_attribute_table_address_ & (((sprite) << 2) | 0x3f80)], write_pointer_.row);
slot(location): posit_sprite(sprite_selection_buffer, sprite, ram_[sprite_attribute_table_address_ & (((sprite) << 2) | 0x3f80)], fetch_pointer_.row);
#define fetch_tile_name(column) line_buffer.names[column].offset = ram_[(row_base + column) & 0x3fff];
@ -237,9 +237,9 @@ template<bool use_end> void Base<personality>::fetch_tms_character(int start, in
slot(location+14): \
slot(location+15): fetch_tile(column+3)
LineBuffer &line_buffer = line_buffers_[write_pointer_.row];
LineBuffer &sprite_selection_buffer = line_buffers_[(write_pointer_.row + 1) % mode_timing_.total_lines];
const size_t row_base = pattern_name_address_ & (size_t((write_pointer_.row << 2)&~31) | 0x3c00);
LineBuffer &line_buffer = line_buffers_[fetch_pointer_.row];
LineBuffer &sprite_selection_buffer = line_buffers_[(fetch_pointer_.row + 1) % mode_timing_.total_lines];
const size_t row_base = pattern_name_address_ & (size_t((fetch_pointer_.row << 2)&~31) | 0x3c00);
size_t pattern_base = pattern_generator_table_address_;
size_t colour_base = colour_table_address_;
@ -247,10 +247,10 @@ template<bool use_end> void Base<personality>::fetch_tms_character(int start, in
if(screen_mode_ == ScreenMode::Graphics) {
// If this is high resolution mode, allow the row number to affect the pattern and colour addresses.
pattern_base &= size_t(0x2000 | ((write_pointer_.row & 0xc0) << 5));
colour_base &= size_t(0x2000 | ((write_pointer_.row & 0xc0) << 5));
pattern_base &= size_t(0x2000 | ((fetch_pointer_.row & 0xc0) << 5));
colour_base &= size_t(0x2000 | ((fetch_pointer_.row & 0xc0) << 5));
colour_base += size_t(write_pointer_.row & 7);
colour_base += size_t(fetch_pointer_.row & 7);
colour_name_shift = 0;
} else {
colour_base &= size_t(0xffc0);
@ -258,9 +258,9 @@ template<bool use_end> void Base<personality>::fetch_tms_character(int start, in
}
if(screen_mode_ == ScreenMode::MultiColour) {
pattern_base += size_t((write_pointer_.row >> 2) & 7);
pattern_base += size_t((fetch_pointer_.row >> 2) & 7);
} else {
pattern_base += size_t(write_pointer_.row & 7);
pattern_base += size_t(fetch_pointer_.row & 7);
}
switch(start) {
@ -348,8 +348,8 @@ template<bool use_end> void Base<personality>::fetch_sms(int start, int end) {
#define sprite_y_read(location, sprite) \
slot(location): \
posit_sprite(sprite_selection_buffer, sprite, ram_[Storage<personality>::sprite_attribute_table_address_ & ((sprite) | 0x3f00)], write_pointer_.row); \
posit_sprite(sprite_selection_buffer, sprite+1, ram_[Storage<personality>::sprite_attribute_table_address_ & ((sprite + 1) | 0x3f00)], write_pointer_.row); \
posit_sprite(sprite_selection_buffer, sprite, ram_[Storage<personality>::sprite_attribute_table_address_ & ((sprite) | 0x3f00)], fetch_pointer_.row); \
posit_sprite(sprite_selection_buffer, sprite+1, ram_[Storage<personality>::sprite_attribute_table_address_ & ((sprite + 1) | 0x3f00)], fetch_pointer_.row); \
#define fetch_tile_name(column, row_info) {\
const size_t scrolled_column = (column - horizontal_offset) & 0x1f;\
@ -391,9 +391,9 @@ template<bool use_end> void Base<personality>::fetch_sms(int start, int end) {
slot(location+15): fetch_tile(column+3)
// Determine the coarse horizontal scrolling offset; this isn't applied on the first two lines if the programmer has requested it.
LineBuffer &line_buffer = line_buffers_[write_pointer_.row];
LineBuffer &sprite_selection_buffer = line_buffers_[(write_pointer_.row + 1) % mode_timing_.total_lines];
const int horizontal_offset = (write_pointer_.row >= 16 || !Storage<personality>::horizontal_scroll_lock_) ? (line_buffer.latched_horizontal_scroll >> 3) : 0;
LineBuffer &line_buffer = line_buffers_[fetch_pointer_.row];
LineBuffer &sprite_selection_buffer = line_buffers_[(fetch_pointer_.row + 1) % mode_timing_.total_lines];
const int horizontal_offset = (fetch_pointer_.row >= 16 || !Storage<personality>::horizontal_scroll_lock_) ? (line_buffer.latched_horizontal_scroll >> 3) : 0;
// Limit address bits in use if this is a SMS2 mode.
const bool is_tall_mode = mode_timing_.pixel_lines != 192;
@ -402,7 +402,7 @@ template<bool use_end> void Base<personality>::fetch_sms(int start, int end) {
// Determine row info for the screen both (i) if vertical scrolling is applied; and (ii) if it isn't.
// The programmer can opt out of applying vertical scrolling to the right-hand portion of the display.
const int scrolled_row = (write_pointer_.row + Storage<personality>::latched_vertical_scroll_) % (is_tall_mode ? 256 : 224);
const int scrolled_row = (fetch_pointer_.row + Storage<personality>::latched_vertical_scroll_) % (is_tall_mode ? 256 : 224);
struct RowInfo {
size_t pattern_address_base;
size_t sub_row[2];
@ -413,9 +413,9 @@ template<bool use_end> void Base<personality>::fetch_sms(int start, int end) {
};
RowInfo row_info;
if(Storage<personality>::vertical_scroll_lock_) {
row_info.pattern_address_base = (pattern_name_address & size_t(((write_pointer_.row & ~7) << 3) | 0x3800)) - pattern_name_offset;
row_info.sub_row[0] = size_t((write_pointer_.row & 7) << 2);
row_info.sub_row[1] = 28 ^ size_t((write_pointer_.row & 7) << 2);
row_info.pattern_address_base = (pattern_name_address & size_t(((fetch_pointer_.row & ~7) << 3) | 0x3800)) - pattern_name_offset;
row_info.sub_row[0] = size_t((fetch_pointer_.row & 7) << 2);
row_info.sub_row[1] = 28 ^ size_t((fetch_pointer_.row & 7) << 2);
} else row_info = scrolled_row_info;
// ... and do the actual fetching, which follows this routine: