vertex-buffer.cpp

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/*
 * Copyright (C) 2023  Christopher J. Howard
 *
 * This file is part of Antkeeper source code.
 *
 * Antkeeper source code is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Antkeeper source code is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#include <engine/gl/vertex-buffer.hpp>
#include <stdexcept>
#include <glad/gl.h>
#include <utility>
 
namespace gl {
 
namespace
{
    static constexpr GLenum buffer_usage_lut[] =
    {
        GL_STREAM_DRAW,
        GL_STREAM_READ,
        GL_STREAM_COPY,
        GL_STATIC_DRAW,
        GL_STATIC_READ,
        GL_STATIC_COPY,
        GL_DYNAMIC_DRAW,
        GL_DYNAMIC_READ,
        GL_DYNAMIC_COPY
    };
}
 
vertex_buffer::vertex_buffer(buffer_usage usage, std::size_t size, std::span<const std::byte> data):
    m_usage{usage},
    m_size{size}
{
    if (!data.empty())
    {
        // Bounds check
        if (data.size() < size)
        {
            throw std::out_of_range("Vertex buffer construct operation exceeded data bounds.");
        }
    }
    
    const GLenum gl_usage = buffer_usage_lut[std::to_underlying(m_usage)];
    glCreateBuffers(1, &m_gl_named_buffer);
    glNamedBufferData(m_gl_named_buffer, static_cast<GLsizeiptr>(m_size), data.empty() ? nullptr : data.data(), gl_usage);
}
 
vertex_buffer::vertex_buffer(const vertex_buffer& buffer):
    vertex_buffer(buffer.m_usage, buffer.m_size)
{
    copy(buffer, m_size);
}
 
vertex_buffer::vertex_buffer(vertex_buffer&& buffer):
    m_gl_named_buffer{std::exchange(buffer.m_gl_named_buffer, 0)},
    m_usage{std::move(buffer.m_usage)},
    m_size{std::exchange(buffer.m_size, 0)}
{}
 
vertex_buffer::~vertex_buffer()
{
    if (m_gl_named_buffer)
    {
        glDeleteBuffers(1, &m_gl_named_buffer);
    }
}
 
vertex_buffer& vertex_buffer::operator=(const vertex_buffer& buffer)
{
    repurpose(buffer.m_usage, buffer.m_size);
    copy(buffer, m_size);
    
    return *this;
}
 
vertex_buffer& vertex_buffer::operator=(vertex_buffer&& buffer)
{
    if (m_gl_named_buffer)
    {
        glDeleteBuffers(1, &m_gl_named_buffer);
    }
    
    m_gl_named_buffer = std::exchange(buffer.m_gl_named_buffer, 0);
    m_usage = std::move(buffer.m_usage);
    m_size = std::exchange(buffer.m_size, 0);
    
    return *this;
}
 
void vertex_buffer::repurpose(buffer_usage usage, std::size_t size, std::span<const std::byte> data)
{
    if (!data.empty())
    {
        // Bounds check
        if (data.size() < size)
        {
            throw std::out_of_range("Vertex buffer resize operation exceeded data bounds.");
        }
    }
    
    m_usage = usage;
    m_size = size;
    
    const auto gl_usage = buffer_usage_lut[std::to_underlying(m_usage)];
    glNamedBufferData(m_gl_named_buffer, static_cast<GLsizeiptr>(m_size), data.empty() ? nullptr : data.data(), gl_usage);
}
 
void vertex_buffer::write(std::size_t offset, std::span<const std::byte> data)
{
    // Ignore empty write operations
    if (data.empty())
    {
        return;
    }
    
    // Bounds check
    if (offset + data.size() > m_size)
    {
        throw std::out_of_range("Vertex buffer write operation exceeded buffer bounds.");
    }
    
    glNamedBufferSubData(m_gl_named_buffer, static_cast<GLintptr>(offset), static_cast<GLsizeiptr>(data.size()), data.data());
}
 
void vertex_buffer::read(std::size_t offset, std::span<std::byte> data) const
{
    // Ignore empty read operations
    if (data.empty())
    {
        return;
    }
    
    // Bounds check
    if (offset + data.size() > m_size)
    {
        throw std::out_of_range("Vertex buffer read operation exceeded buffer bounds.");
    }
    
    glGetNamedBufferSubData(m_gl_named_buffer, static_cast<GLintptr>(offset), static_cast<GLsizeiptr>(data.size()), data.data());
}
 
void vertex_buffer::copy(const vertex_buffer& read_buffer, std::size_t copy_size, std::size_t read_offset, std::size_t write_offset)
{
    // Bounds check
    if (read_offset + copy_size > read_buffer.m_size)
    {
        throw std::out_of_range("Vertex buffer copy operation exceeded read buffer bounds.");
    }
    if (write_offset + copy_size > m_size)
    {
        throw std::out_of_range("Vertex buffer copy operation exceeded write buffer bounds.");
    }
    
    glCopyNamedBufferSubData(read_buffer.m_gl_named_buffer, m_gl_named_buffer, static_cast<GLintptr>(read_offset), static_cast<GLintptr>(write_offset), static_cast<GLsizeiptr>(copy_size));
}
 
} // namespace gl