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190 lines
6.4 KiB
C++
190 lines
6.4 KiB
C++
//
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// ScanTarget.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 05/11/2018.
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// Copyright © 2018 Thomas Harte. All rights reserved.
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//
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#include "ScanTarget.hpp"
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#include "Primitives/Rectangle.hpp"
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using namespace Outputs::Display::OpenGL;
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namespace {
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constexpr int WriteAreaWidth = 2048;
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constexpr int WriteAreaHeight = 2048;
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#define TextureAddress(x, y) (((x) << 11) | (y))
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#define TextureAddressGetX(v) ((v) >> 11)
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#define TextureAddressGetY(v) ((v) & 0x7ff)
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#define TextureSub(x, y) (((x) - (y)) & 0x7ff)
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}
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ScanTarget::ScanTarget() {
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// Allocate space for the scans.
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glGenBuffers(1, &scan_buffer_name_);
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glBindBuffer(GL_ARRAY_BUFFER, scan_buffer_name_);
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const auto buffer_size = scan_buffer_.size() * sizeof(Scan);
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glBufferData(GL_ARRAY_BUFFER, GLsizeiptr(buffer_size), NULL, GL_STREAM_DRAW);
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// TODO: if this is OpenGL 4.4 or newer, use glBufferStorage rather than glBufferData
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// and specify GL_MAP_PERSISTENT_BIT. Then map the buffer now, and let the client
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// write straight into it.
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}
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ScanTarget::~ScanTarget() {
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// Release scan space.
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glDeleteBuffers(1, &scan_buffer_name_);
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}
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void ScanTarget::set_modals(Modals modals) {
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// TODO: consider resizing the write_area_texture_, and setting
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// write_area_texture_line_length_ appropriately.
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modals_ = modals;
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const auto data_type_size = Outputs::Display::size_for_data_type(modals.input_data_type);
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if(data_type_size != data_type_size_) {
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// TODO: flush output.
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data_type_size_ = data_type_size;
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write_area_texture_.resize(2048*2048*data_type_size_);
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write_pointers_.scan_buffer = 0;
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write_pointers_.write_area = 0;
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}
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}
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Outputs::Display::ScanTarget::Scan *ScanTarget::get_scan() {
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if(allocation_has_failed_) return nullptr;
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const auto result = &scan_buffer_[write_pointers_.scan_buffer];
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const auto read_pointers = read_pointers_.load();
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// Advance the pointer.
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const auto next_write_pointer = decltype(write_pointers_.scan_buffer)((write_pointers_.scan_buffer + 1) % scan_buffer_.size());
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// Check whether that's too many.
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if(next_write_pointer == read_pointers.scan_buffer) {
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allocation_has_failed_ = true;
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return nullptr;
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}
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write_pointers_.scan_buffer = next_write_pointer;
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// Fill in extra OpenGL-specific details.
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// result->data_y = write_pointers_.write_area;
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result->composite_y = 0;
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return static_cast<Outputs::Display::ScanTarget::Scan *>(result);
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}
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uint8_t *ScanTarget::allocate_write_area(size_t required_length, size_t required_alignment) {
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if(allocation_has_failed_) return nullptr;
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// Determine where the proposed write area would start and end.
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uint16_t output_y = TextureAddressGetY(write_pointers_.write_area);
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uint16_t aligned_start_x = TextureAddressGetX(write_pointers_.write_area & 0xffff) + 1;
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aligned_start_x += uint16_t((required_alignment - aligned_start_x%required_alignment)%required_alignment);
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uint16_t end_x = aligned_start_x + uint16_t(1 + required_length);
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if(end_x > WriteAreaWidth) {
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output_y = (output_y + 1) % WriteAreaHeight;
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aligned_start_x = uint16_t(required_alignment);
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end_x = aligned_start_x + uint16_t(1 + required_length);
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}
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// Check whether that steps over the read pointer.
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const auto new_address = TextureAddress(end_x, output_y);
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const auto read_pointers = read_pointers_.load();
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const auto new_distance = TextureSub(read_pointers.write_area, new_address);
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const auto previous_distance = TextureSub(read_pointers.write_area, write_pointers_.write_area);
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// If allocating this would somehow make the write pointer further away from the read pointer,
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// there must not be enough space left.
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if(new_distance > previous_distance) {
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allocation_has_failed_ = true;
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return nullptr;
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}
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// Everything checks out, return the pointer.
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last_supplied_x_ = aligned_start_x;
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return &write_area_texture_[size_t(new_address) * data_type_size_];
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}
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void ScanTarget::reduce_previous_allocation_to(size_t actual_length) {
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if(allocation_has_failed_) return;
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// The write area was allocated in the knowledge that there's sufficient
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// distance left on the current line, so there's no need to worry about carry.
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write_pointers_.write_area += actual_length + 1;
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}
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void ScanTarget::submit() {
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if(allocation_has_failed_) {
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// Reset all pointers to where they were.
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write_pointers_ = submit_pointers_.load();
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} else {
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// Advance submit pointer.
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submit_pointers_.store(write_pointers_);
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}
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allocation_has_failed_ = false;
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}
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void ScanTarget::draw() {
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// Grab the current read and submit pointers.
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const auto submit_pointers = submit_pointers_.load();
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const auto read_pointers = read_pointers_.load();
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// Submit scans.
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if(submit_pointers.scan_buffer != read_pointers.scan_buffer) {
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const auto buffer_size = scan_buffer_.size() * sizeof(Scan);
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uint8_t *destination = static_cast<uint8_t *>(
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glMapBufferRange(GL_ARRAY_BUFFER, 0, GLsizeiptr(buffer_size), GL_MAP_WRITE_BIT | GL_MAP_FLUSH_EXPLICIT_BIT)
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);
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if(submit_pointers.scan_buffer > read_pointers.scan_buffer) {
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// Submit the direct region from the submit pointer to the read pointer.
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const size_t offset = read_pointers.scan_buffer * sizeof(Scan);
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const size_t length = (submit_pointers.scan_buffer - read_pointers.scan_buffer) * sizeof(Scan);
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memcpy(&destination[offset], &scan_buffer_[read_pointers.scan_buffer], length);
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glFlushMappedBufferRange(GL_ARRAY_BUFFER, GLintptr(offset), GLsizeiptr(length));
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} else {
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// The circular buffer wrapped around; submit the data from the read pointer to the end of
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// the buffer and from the start of the buffer to the submit pointer.
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const size_t offset = read_pointers.scan_buffer * sizeof(Scan);
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const size_t end_length = (scan_buffer_.size() - read_pointers.scan_buffer) * sizeof(Scan);
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const size_t start_length = submit_pointers.scan_buffer * sizeof(Scan);
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memcpy(&destination[offset], &scan_buffer_[read_pointers.scan_buffer], end_length);
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memcpy(&destination[0], &scan_buffer_[0], start_length);
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glFlushMappedBufferRange(GL_ARRAY_BUFFER, GLintptr(offset), GLsizeiptr(end_length));
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glFlushMappedBufferRange(GL_ARRAY_BUFFER, 0, GLsizeiptr(start_length));
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}
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glUnmapBuffer(GL_ARRAY_BUFFER);
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}
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// TODO: submit texture.
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// TODO: clear composite buffer (if needed).
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// TODO: drawing (!)
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// All data now having been spooled to the GPU, update the read pointers to
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// the submit pointer location.
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read_pointers_.store(submit_pointers);
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glClear(GL_COLOR_BUFFER_BIT);
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// ::OpenGL::Rectangle rect(-0.8f, -0.8f, 1.6f, 1.6f);
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// rect.draw(1, 1, 0);
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}
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