blender-archive/intern/gawain/src/gwn_shader_interface.c

// Gawain shader interface (C --> GLSL)
//
// This code is part of the Gawain library, with modifications
// specific to integration with Blender.
//
// Copyright 2017 Mike Erwin
//
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of
// the MPL was not distributed with this file, You can obtain one at https://mozilla.org/MPL/2.0/.

#include "gwn_shader_interface.h"
#include <stdlib.h>
#include <stddef.h>
#include <string.h>

#define DEBUG_SHADER_INTERFACE 0

#if DEBUG_SHADER_INTERFACE
 #include <stdio.h>
#endif

static const char* BuiltinUniform_name(Gwn_UniformBuiltin u)
	{
	static const char* names[] =
		{
		[GWN_UNIFORM_NONE] = NULL,

		[GWN_UNIFORM_MODELVIEW] = "ModelViewMatrix",
		[GWN_UNIFORM_PROJECTION] = "ProjectionMatrix",
		[GWN_UNIFORM_MVP] = "ModelViewProjectionMatrix",

		[GWN_UNIFORM_MODELVIEW_INV] = "ModelViewInverseMatrix",
		[GWN_UNIFORM_PROJECTION_INV] = "ProjectionInverseMatrix",

		[GWN_UNIFORM_NORMAL] = "NormalMatrix",

		[GWN_UNIFORM_COLOR] = "color",

		[GWN_UNIFORM_CUSTOM] = NULL,
		[GWN_NUM_UNIFORMS] = NULL,
		};

	return names[u];
	}

GWN_INLINE bool match(const char* a, const char* b)
	{
	return strcmp(a, b) == 0;
	}

GWN_INLINE unsigned hash_string(const char *str)
	{
	unsigned i = 0, c;

	while ((c = *str++))
		{
		i = i * 37 + c;
		}

	return i;
	}

GWN_INLINE void set_input_name(Gwn_ShaderInterface* shaderface, Gwn_ShaderInput* input,
                               const char* name, uint32_t name_len)
	{
	input->name_offset = shaderface->name_buffer_offset;
	input->name_hash = hash_string(name);
	shaderface->name_buffer_offset += name_len + 1; // include NULL terminator
	}

GWN_INLINE void shader_input_to_bucket(Gwn_ShaderInput* input,
                                       Gwn_ShaderInput* buckets[GWN_NUM_SHADERINTERFACE_BUCKETS])
	{
	const unsigned bucket_index = input->name_hash % GWN_NUM_SHADERINTERFACE_BUCKETS;
	input->next = buckets[bucket_index];
	buckets[bucket_index] = input;
	}

GWN_INLINE const Gwn_ShaderInput* buckets_lookup(Gwn_ShaderInput* const buckets[GWN_NUM_SHADERINTERFACE_BUCKETS],
                                           const char *name_buffer, const char *name)
	{
	const unsigned name_hash = hash_string(name);
	const unsigned bucket_index = name_hash % GWN_NUM_SHADERINTERFACE_BUCKETS;
	const Gwn_ShaderInput* input = buckets[bucket_index];
	if (input == NULL)
		{
			// Requested uniform is not found at all.
			return NULL;
		}
	// Optimization bit: if there is no hash collision detected when constructing shader interface
	// it means we can only request the single possible uniform. Surely, it's possible we request
	// uniform which causes hash collision, but that will be detected in debug builds.
	if (input->next == NULL)
		{
			if (name_hash == input->name_hash)
				{
#if TRUST_NO_ONE
				assert(match(name_buffer + input->name_offset, name));
#endif
				return input;
				}
			return NULL;
		}
	// Work through possible collisions.
	const Gwn_ShaderInput* next = input;
	while (next != NULL)
		{
		input = next;
		next = input->next;

		if (input->name_hash != name_hash)
			{
			continue;
			}
		if (match(name_buffer + input->name_offset, name))
			{
			return input;
			}
		}
	return NULL; // not found
	}

GWN_INLINE void buckets_free(Gwn_ShaderInput* buckets[GWN_NUM_SHADERINTERFACE_BUCKETS])
	{
	for (unsigned bucket_index = 0; bucket_index < GWN_NUM_SHADERINTERFACE_BUCKETS; ++bucket_index)
		{
		Gwn_ShaderInput *input = buckets[bucket_index];
		while (input != NULL)
			{
			Gwn_ShaderInput *input_next = input->next;
			free(input);
			input = input_next;
			}
		}
	}

// keep these in sync with Gwn_UniformBuiltin order
#define FIRST_UNIFORM GWN_UNIFORM_MODELVIEW
#define LAST_UNIFORM GWN_UNIFORM_COLOR

static bool setup_builtin_uniform(Gwn_ShaderInput* input, const char* name)
	{
	// TODO: reject DOUBLE, IMAGE, ATOMIC_COUNTER gl_types

	// detect built-in uniforms (name must match)
	for (Gwn_UniformBuiltin u = FIRST_UNIFORM; u <= LAST_UNIFORM; ++u)
		{
		const char* builtin_name = BuiltinUniform_name(u);
		if (match(name, builtin_name))
			{
			input->builtin_type = u;
			return true;
			}
		}

	input->builtin_type = GWN_UNIFORM_CUSTOM;
	return false;
	}

static const Gwn_ShaderInput* add_uniform(Gwn_ShaderInterface* shaderface, const char* name)
	{
		Gwn_ShaderInput* input = malloc(sizeof(Gwn_ShaderInput));

		input->location = glGetUniformLocation(shaderface->program, name);

		unsigned name_len = strlen(name);
		shaderface->name_buffer = realloc(shaderface->name_buffer, shaderface->name_buffer_offset + name_len + 1); // include NULL terminator
		char* name_buffer = shaderface->name_buffer + shaderface->name_buffer_offset;
		strcpy(name_buffer, name);

		set_input_name(shaderface, input, name, name_len);
		setup_builtin_uniform(input, name);

		shader_input_to_bucket(input, shaderface->uniform_buckets);
		if (input->builtin_type != GWN_UNIFORM_NONE &&
		    input->builtin_type != GWN_UNIFORM_CUSTOM)
			{
			shaderface->builtin_uniforms[input->builtin_type] = input;
			}
#if DEBUG_SHADER_INTERFACE
		printf("Gwn_ShaderInterface %p, program %d, uniform[] '%s' at location %d\n", shaderface, shaderface->program, name, input->location);
#endif
		return input;
	}

Gwn_ShaderInterface* GWN_shaderinterface_create(GLint program)
	{
	Gwn_ShaderInterface* shaderface = calloc(1, sizeof(Gwn_ShaderInterface));
	shaderface->program = program;

#if DEBUG_SHADER_INTERFACE
	printf("%s {\n", __func__); // enter function
	printf("Gwn_ShaderInterface %p, program %d\n", shaderface, program);
#endif

	GLint max_attrib_name_len, attrib_ct;
	glGetProgramiv(program, GL_ACTIVE_ATTRIBUTE_MAX_LENGTH, &max_attrib_name_len);
	glGetProgramiv(program, GL_ACTIVE_ATTRIBUTES, &attrib_ct);

	GLint max_ubo_name_len, ubo_ct;
	glGetProgramiv(program, GL_ACTIVE_UNIFORM_BLOCK_MAX_NAME_LENGTH, &max_ubo_name_len);
	glGetProgramiv(program, GL_ACTIVE_UNIFORM_BLOCKS, &ubo_ct);

	const uint32_t name_buffer_len = attrib_ct * max_attrib_name_len + ubo_ct * max_ubo_name_len;
	shaderface->name_buffer = malloc(name_buffer_len);

	// Attributes
	for (uint32_t i = 0; i < attrib_ct; ++i)
		{
		Gwn_ShaderInput* input = malloc(sizeof(Gwn_ShaderInput));
		GLsizei remaining_buffer = name_buffer_len - shaderface->name_buffer_offset;
		char* name = shaderface->name_buffer + shaderface->name_buffer_offset;
		GLsizei name_len = 0;

		glGetActiveAttrib(program, i, remaining_buffer, &name_len, &input->size, &input->gl_type, name);

		// TODO: reject DOUBLE gl_types

		input->location = glGetAttribLocation(program, name);

		set_input_name(shaderface, input, name, name_len);

		shader_input_to_bucket(input, shaderface->attrib_buckets);

#if DEBUG_SHADER_INTERFACE
		printf("attrib[%u] '%s' at location %d\n", i, name, input->location);
#endif
		}

	// Uniform Blocks
	for (uint32_t i = 0; i < ubo_ct; ++i)
		{
		Gwn_ShaderInput* input = malloc(sizeof(Gwn_ShaderInput));
		GLsizei remaining_buffer = name_buffer_len - shaderface->name_buffer_offset;
		char* name = shaderface->name_buffer + shaderface->name_buffer_offset;
		GLsizei name_len = 0;

		glGetActiveUniformBlockName(program, i, remaining_buffer, &name_len, name);

		input->location = i;

		set_input_name(shaderface, input, name, name_len);

		shader_input_to_bucket(input, shaderface->ubo_buckets);

#if DEBUG_SHADER_INTERFACE
		printf("attrib[%u] '%s' at location %d\n", i, name, input->location);
#endif
		}

	return shaderface;
	}

void GWN_shaderinterface_discard(Gwn_ShaderInterface* shaderface)
	{
	// Free memory used by buckets and has entries.
	buckets_free(shaderface->uniform_buckets);
	buckets_free(shaderface->attrib_buckets);
	buckets_free(shaderface->ubo_buckets);
	// Free memory used by name_buffer.
	free(shaderface->name_buffer);
	// Free memory used by shader interface by its self.
	free(shaderface);
	}

const Gwn_ShaderInput* GWN_shaderinterface_uniform(const Gwn_ShaderInterface* shaderface, const char* name)
	{
	// TODO: Warn if we find a matching builtin, since these can be looked up much quicker.
	const Gwn_ShaderInput* input = buckets_lookup(shaderface->uniform_buckets, shaderface->name_buffer, name);

	// If input is not found add it so it's found next time.
	if (input == NULL)
		input = add_uniform((Gwn_ShaderInterface*)shaderface, name);

	return (input->location != -1) ? input : NULL;
	}

const Gwn_ShaderInput* GWN_shaderinterface_uniform_builtin(const Gwn_ShaderInterface* shaderface, Gwn_UniformBuiltin builtin)
	{
#if TRUST_NO_ONE
	assert(builtin != GWN_UNIFORM_NONE);
	assert(builtin != GWN_UNIFORM_CUSTOM);
	assert(builtin != GWN_NUM_UNIFORMS);
#endif

	const Gwn_ShaderInput* input = shaderface->builtin_uniforms[builtin];

	// If input is not found add it so it's found next time.
	if (input == NULL)
		input = add_uniform((Gwn_ShaderInterface*)shaderface, BuiltinUniform_name(builtin));

	return (input->location != -1) ? input : NULL;
	}

const Gwn_ShaderInput* GWN_shaderinterface_ubo(const Gwn_ShaderInterface* shaderface, const char* name)
	{
	return buckets_lookup(shaderface->ubo_buckets, shaderface->name_buffer, name);
	}

const Gwn_ShaderInput* GWN_shaderinterface_attr(const Gwn_ShaderInterface* shaderface, const char* name)
	{
	return buckets_lookup(shaderface->attrib_buckets, shaderface->name_buffer, name);
	}