Save texture to TGA using mmap

Removes the need to allocate a large temporary buffer, instead just memmaps a file big enough and has
OpenGL write the texture data directly to it.

1 files changed, 16 insertions, 9 deletions

diff --git a/gfx/models/texture.cpp b/gfx/models/texture.cpp
index 645920f..5b8d376 100644
--- a/gfx/models/texture.cpp
+++ b/gfx/models/texture.cpp
@@ -7,6 +7,7 @@
 #include <glm/geometric.hpp>

 #include <resource.h>

 #include <stb/stb_image.h>

+#include <sys/mman.h>

 

 Cache<Texture, std::filesystem::path> Texture::cachedTexture;

 

@@ -44,17 +45,23 @@ void
 Texture::save(const glTexture & texture, GLenum format, const glm::ivec2 & size, unsigned short channels,

 		const char * path, short tgaFormat)

 {

-	using PixelData = std::vector<unsigned char>;

-	PixelData buffer(static_cast<size_t>(size.x * size.y * channels));

-	glGetTextureImage(texture, 0, format, GL_UNSIGNED_BYTE, static_cast<GLsizei>(buffer.size()), buffer.data());

+	using TGAHead = std::array<short, 9>;

 

-	auto out = open(path, O_WRONLY | O_CREAT, 0660);

-	const short TGAhead[] = {0, tgaFormat, 0, 0, 0, 0, static_cast<short>(size.x), static_cast<short>(size.y),

-			static_cast<short>(8 * channels)};

-	std::ignore = write(out, &TGAhead, sizeof(TGAhead));

-	std::ignore = write(out, buffer.data(), buffer.size());

-	std::ignore = ftruncate(out, static_cast<off_t>(buffer.size() + sizeof(TGAhead)));

+	size_t dataSize = (static_cast<size_t>(size.x * size.y * channels));

+	size_t fileSize = dataSize + sizeof(TGAHead);

+

+	auto out = open(path, O_RDWR | O_CREAT, 0660);

+	std::ignore = ftruncate(out, static_cast<off_t>(fileSize));

+	TGAHead * tga = static_cast<TGAHead *>(mmap(nullptr, fileSize, PROT_WRITE, MAP_SHARED, out, 0));

 	close(out);

+	if (tga == MAP_FAILED) {

+		return;

+	}

+	*tga = {0, tgaFormat, 0, 0, 0, 0, static_cast<short>(size.x), static_cast<short>(size.y),

+			static_cast<short>(8 * channels)};

+	glGetTextureImage(texture, 0, format, GL_UNSIGNED_BYTE, static_cast<GLsizei>(dataSize), tga + 1);

+	msync(tga, fileSize, MS_ASYNC);

+	munmap(tga, fileSize);

 }

 

 void