shader_testing/src/util.h

#ifndef UTIL_H
#define UTIL_H

#include <cassert>
#include <cstring>

#include "types.h"


//-----------------
// Hashing

// NOTE: FNV1a hashing algorithm http://www.isthe.com/chongo/tech/comp/fnv/
#define FNV1_64_INIT ((u64) 0xcbf29ce484222325ULL)
#define FNV_64_PRIME ((u64) 0x100000001b3ULL)
u64
utilFNV64a_str(const char *str, u64 hval = FNV1_64_INIT);

//-----------------
// Memory allocation

struct memory_arena
{
	size_t max_size;
	void* head;
	void* next_free;
};

#define DEFAULT_ARENA_SIZE 10 * 1024 * 1024 // 10MB
memory_arena* arenaInit(size_t initial_size = DEFAULT_ARENA_SIZE);

void arenaFree(memory_arena*& arena);
uint arenaGetFreeSize(memory_arena* arena);

#define ARENA_ALLOC(arena, type, count) \
	(type*) arenaAllocateBlock(arena, sizeof(type) * count)
void* arenaAllocateBlock(memory_arena* arena, size_t block_size);

#define MAX_NAME_LENGTH 256
char* arenaCopyCStr(memory_arena* arena,
	const char* input,
	u32 max_len = MAX_NAME_LENGTH);

char* utilAllocateCStr(const char* str, u32 max_len = 256);
void utilSafeFree(void* p);

#endif // UTIL_H


#ifdef UTIL_IMPLEMENTATION

//-----------------
// Hashing

uint64_t
utilFNV64a_str(const char* str, uint64_t hval)
{
	unsigned char* s = (unsigned char *)str; // unsigned string

	// FNV-1a hash each octet of the string
	while (*s) {
		// xor the bottom with the current octet
		hval ^= (uint64_t)*s++;
		// multiply by the 64 bit FNV magic prime mod 2^64
		hval *= FNV_64_PRIME;
	}

	return hval;
}

//-----------------
// Memory allocation

memory_arena*
arenaInit(size_t initial_size)
{
	uint sz = sizeof(memory_arena);
	memory_arena* arena =
		(memory_arena*) std::calloc(initial_size + sz, sizeof(u8));
	arena->head = arena->next_free = (uint8_t*) arena + sz;
	arena->max_size = initial_size;
	return arena;
}

void
arenaFree(memory_arena*& arena)
{
	if (arena != nullptr) {
		std::free(arena);
		arena = nullptr;
	}
}

uint
arenaGetFreeSize(memory_arena* arena)
{
	return (uint8_t*) arena->head
		+ arena->max_size
		- (uint8_t*) arena->next_free;
}

void*
arenaAllocateBlock(memory_arena* arena, size_t block_size)
{
	// TODO: resizable memory arena
	assert(arenaGetFreeSize(arena) >= block_size);
	assert(block_size > 0);
	void* ret = arena->next_free;
	arena->next_free = (uint8_t*) arena->next_free + block_size;
	return ret;
}

char*
arenaCopyCStr(memory_arena* arena, const char* input, u32 max_len)
{
	u32 name_len = std::strlen(input) + 1;
	assert(name_len < max_len);
	char* out = ARENA_ALLOC(arena, char, name_len);
	std::strncpy(out, input, name_len);
	return out;
}

char*
utilAllocateCStr(const char* str, u32 max_len)
{
	u32 len = strlen(str) + 1;

	if (len > max_len) {
		printf("%s(), %s , longer than %i\n", __FUNCTION__, str, max_len);
		return nullptr;
	}

	char* out = (char*) std::calloc(len, sizeof(u8));
	strncpy(out, str, len - 1);
	return out;
}

void
utilSafeFree(void* p)
{
	assert(p != nullptr);
	free(p);
}

#endif