gvox-sys 1.3.0

Voxel file format parser
Documentation 
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#pragma once

#include "math_helpers.hpp"

static constexpr auto REGION_SIZE = size_t{8};

static constexpr auto get_mask(uint32_t bits_per_variant) -> uint32_t {
    return (~0u) >> (32 - bits_per_variant);
}

static constexpr auto calc_palette_region_size(size_t bits_per_variant) -> size_t {
    auto palette_region_size = (bits_per_variant * REGION_SIZE * REGION_SIZE * REGION_SIZE + 7) / 8;
    palette_region_size = (palette_region_size + 3) / 4;
    auto size = palette_region_size + 1;
    return size * 4;
}

static constexpr auto calc_block_size(size_t variant_n) -> size_t {
    return calc_palette_region_size(ceil_log2(static_cast<uint32_t>(variant_n))) + sizeof(uint32_t) * variant_n;
}

static constexpr auto MAX_REGION_ALLOCATION_SIZE = REGION_SIZE * REGION_SIZE * REGION_SIZE * sizeof(uint32_t);
static constexpr auto MAX_REGION_COMPRESSED_VARIANT_N =
    REGION_SIZE == 8 ? 367 : (REGION_SIZE == 16 ? 2559 : 0);

static_assert(calc_block_size(MAX_REGION_COMPRESSED_VARIANT_N) <= MAX_REGION_ALLOCATION_SIZE);
static_assert(calc_block_size(MAX_REGION_COMPRESSED_VARIANT_N + 1) > MAX_REGION_ALLOCATION_SIZE);

struct ChannelHeader {
    uint32_t variant_n;
    uint32_t blob_offset; // if variant_n == 1, this is just the data
};