253 lines
8.1 KiB
C++
253 lines
8.1 KiB
C++
#include <cstdint>
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#include <tuple>
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namespace twiddle {
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/*
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This reproduces the twiddle index table shown in
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"3.6.2.1 Twiddled Format".
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x →
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000 001 010 011
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--------------------------------
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| xyxyxy xyxyxy xyxyxy xyxyxy
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|===============================
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y 000 | 000000 000010 001000 001010
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↓ 001 | 000001 000011 001001 001011
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010 | 000100 000110 001100 001110
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011 | 000101 000111 001101 001111
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alternately, in verilog syntax:
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input [2:0] x; // x coordinate
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input [2:0] y; // y coordinate
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output [5:0] t; // twiddled index
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assign t = {x[2], y[2], x[1], y[1], x[0], y[0]};
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*/
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constexpr inline int log2(uint32_t n)
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{
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switch (n) {
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default:
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case 8: return 3;
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case 16: return 4;
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case 32: return 5;
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case 64: return 6;
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case 128: return 7;
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case 256: return 8;
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case 512: return 9;
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case 1024: return 10;
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}
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}
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constexpr inline uint32_t from_xy(uint32_t x, uint32_t y, uint32_t width, uint32_t height)
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{
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// maximum texture size : 1024x1024
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// maximum 1-dimensional index: 0xfffff
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// bits : 19-0
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// y bits: 0, 2, 4, 6, 8, 10, 12, 14, 16, 18
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// x bits: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19
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int width_max = log2(width);
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int height_max = log2(height);
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uint32_t twiddle_ix = 0;
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for (int i = 0; i < (20 / 2); i++) {
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if (i < width_max && i < height_max) {
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twiddle_ix |= ((y >> i) & 1) << (i * 2 + 0);
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twiddle_ix |= ((x >> i) & 1) << (i * 2 + 1);
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} else if (i < width_max) {
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twiddle_ix |= ((x >> i) & 1) << (i + height_max);
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} else if (i < height_max) {
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twiddle_ix |= ((y >> i) & 1) << (i + width_max);
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} else {
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break;
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}
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}
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return twiddle_ix;
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}
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static_assert(from_xy(0b000, 0b000, 8, 8) == 0);
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static_assert(from_xy(0b001, 0b000, 8, 8) == 2);
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static_assert(from_xy(0b010, 0b000, 8, 8) == 8);
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static_assert(from_xy(0b011, 0b000, 8, 8) == 10);
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static_assert(from_xy(0b100, 0b000, 8, 8) == 32);
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static_assert(from_xy(0b101, 0b000, 8, 8) == 34);
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static_assert(from_xy(0b110, 0b000, 8, 8) == 40);
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static_assert(from_xy(0b111, 0b000, 8, 8) == 42);
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static_assert(from_xy(0b000, 0b001, 8, 8) == 1);
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static_assert(from_xy(0b000, 0b010, 8, 8) == 4);
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static_assert(from_xy(0b000, 0b011, 8, 8) == 5);
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static_assert(from_xy(0b000, 0b100, 8, 8) == 16);
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static_assert(from_xy(0b000, 0b101, 8, 8) == 17);
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static_assert(from_xy(0b000, 0b110, 8, 8) == 20);
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static_assert(from_xy(0b000, 0b111, 8, 8) == 21);
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// 1 0 0 0
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// x bits: 19, 17, 15, 13, 11, 9, 7, 5, 3, 1
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// y bits: 18, 16, 14, 12, 10, 8, 6, 4, 2, 0
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static_assert(from_xy(0b1000, 0b001, 16, 8) == 65);
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static_assert(from_xy(0b1010, 0b001, 16, 8) == 73);
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static_assert(from_xy(0b000, 0b1001, 8, 16) == 65);
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static_assert(from_xy(0b010, 0b1001, 8, 16) == 73);
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/*
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constexpr inline std::array<uint32_t, 2>
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from_ix(uint32_t curve_ix)
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{
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std::array<uint32_t, 2> x_y = {0, 0};
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uint32_t curve_bit = 0;
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while (curve_ix != 0) {
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x_y[(curve_bit + 1) % 2] |= (curve_ix & 1) << (curve_bit / 2);
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curve_ix >>= 1;
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curve_bit += 1;
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}
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return x_y;
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}
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constexpr inline std::tuple<uint32_t, uint32_t>
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from_ix(uint32_t curve_ix)
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{
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uint32_t y = (curve_ix >> 0) & 0x55555555;
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y = (y | (y >> 1)) & 0x33333333;
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y = (y | (y >> 2)) & 0x0f0f0f0f;
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y = (y | (y >> 4)) & 0x00ff00ff;
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y = (y | (y >> 8)) & 0x0000ffff;
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uint32_t x = (curve_ix >> 1) & 0x55555555;
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x = (x | (x >> 1)) & 0x33333333;
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x = (x | (x >> 2)) & 0x0f0f0f0f;
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x = (x | (x >> 4)) & 0x00ff00ff;
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x = (x | (x >> 8)) & 0x0000ffff;
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return {x, y};
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}
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using xy_type = std::tuple<uint32_t, uint32_t>;
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static_assert(from_ix(0) == xy_type{0b000, 0b000});
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static_assert(from_ix(2) == xy_type{0b001, 0b000});
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static_assert(from_ix(8) == xy_type{0b010, 0b000});
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static_assert(from_ix(10) == xy_type{0b011, 0b000});
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static_assert(from_ix(32) == xy_type{0b100, 0b000});
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static_assert(from_ix(34) == xy_type{0b101, 0b000});
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static_assert(from_ix(40) == xy_type{0b110, 0b000});
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static_assert(from_ix(42) == xy_type{0b111, 0b000});
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static_assert(from_ix(1) == xy_type{0b000, 0b001});
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static_assert(from_ix(4) == xy_type{0b000, 0b010});
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static_assert(from_ix(5) == xy_type{0b000, 0b011});
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static_assert(from_ix(16) == xy_type{0b000, 0b100});
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static_assert(from_ix(17) == xy_type{0b000, 0b101});
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static_assert(from_ix(20) == xy_type{0b000, 0b110});
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static_assert(from_ix(21) == xy_type{0b000, 0b111});
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*/
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template <typename T>
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void texture(volatile T * dst, const T * src, const uint32_t width, const uint32_t height)
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{
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for (uint32_t y = 0; y < height; y++) {
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for (uint32_t x = 0; x < width; x++) {
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uint32_t twiddle_ix = from_xy(x, y, width, height);
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T value = src[y * width + x];
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dst[twiddle_ix] = value;
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}
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}
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}
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template <typename T>
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void texture_4bpp(volatile T * dst, const T * src, const uint32_t width, const uint32_t height)
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{
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for (uint32_t y = 0; y < height; y++) {
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for (uint32_t x = 0; x < width; x++) {
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uint32_t twiddle_ix = from_xy(x, y, width, height);
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T value = src[y * width + x];
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uint32_t shift = (4 * (twiddle_ix & 1));
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dst[twiddle_ix / 2] &= ~(0b1111 << shift);
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dst[twiddle_ix / 2] |= value << shift;
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}
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}
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}
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/*
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the following code is not correct
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template <uint32_t dst_bits_per_pixel, typename T, typename U>
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void texture2(volatile T * dst, const U * src,
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const uint32_t src_stride,
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const uint32_t curve_end_ix)
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{
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constexpr uint32_t t_bits = (sizeof (T)) * 8;
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static_assert(t_bits >= dst_bits_per_pixel);
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static_assert((t_bits / dst_bits_per_pixel) * dst_bits_per_pixel == t_bits);
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constexpr uint32_t pixels_per_t = t_bits / dst_bits_per_pixel;
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static_assert(pixels_per_t == 1 || pixels_per_t == 2 || pixels_per_t == 4 || pixels_per_t == 8 || pixels_per_t == 16 || pixels_per_t == 32);
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T dst_val = 0;
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for (uint32_t curve_ix = 0; curve_ix <= curve_end_ix; curve_ix++) {
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auto [x, y] = from_ix(curve_ix);
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const U src_val = src[y * src_stride + x];
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if constexpr (pixels_per_t == 1) {
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dst[curve_ix] = src_val;
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} else {
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const uint32_t curve_ix_mod = curve_ix & (pixels_per_t - 1);
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dst_val |= src_val << (dst_bits_per_pixel * curve_ix_mod);
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if (curve_ix_mod == (pixels_per_t - 1)) {
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dst[curve_ix / pixels_per_t] = dst_val;
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dst_val = 0;
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}
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}
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}
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}
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template <uint32_t dst_bits_per_pixel, uint32_t src_bits_per_pixel, typename T, typename U>
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void texture3(volatile T * dst, const U * src,
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const uint32_t src_stride,
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const uint32_t curve_end_ix)
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{
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constexpr uint32_t t_bits = (sizeof (T)) * 8;
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static_assert(t_bits >= dst_bits_per_pixel);
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static_assert((t_bits / dst_bits_per_pixel) * dst_bits_per_pixel == t_bits);
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constexpr uint32_t pixels_per_t = t_bits / dst_bits_per_pixel;
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static_assert(pixels_per_t == 1 || pixels_per_t == 2 || pixels_per_t == 4 || pixels_per_t == 8 || pixels_per_t == 16 || pixels_per_t == 32);
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constexpr uint32_t u_bits = (sizeof (U)) * 8;
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static_assert(u_bits >= src_bits_per_pixel);
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static_assert((u_bits / src_bits_per_pixel) * src_bits_per_pixel == u_bits);
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constexpr uint32_t pixels_per_u = u_bits / src_bits_per_pixel;
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static_assert(pixels_per_u == 1 || pixels_per_u == 2 || pixels_per_u == 4 || pixels_per_u == 8 || pixels_per_u == 16 || pixels_per_u == 32);
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constexpr uint32_t src_val_mask = ((1 << src_bits_per_pixel) - 1);
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constexpr uint32_t dst_val_mask = ((1 << dst_bits_per_pixel) - 1);
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constexpr uint32_t dst_src_shift = (dst_bits_per_pixel < src_bits_per_pixel) ? (src_bits_per_pixel - dst_bits_per_pixel) : 0;
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T dst_val = 0;
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for (uint32_t curve_ix = 0; curve_ix <= curve_end_ix; curve_ix++) {
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auto [x, y] = from_ix(curve_ix);
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const uint32_t src_ix = y * src_stride + (x / pixels_per_u);
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const uint32_t src_ix_mod = x & (pixels_per_u - 1);
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const U src_val = (src[src_ix] >> (src_bits_per_pixel * src_ix_mod)) & src_val_mask;
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if constexpr (pixels_per_t == 1) {
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dst[curve_ix] = src_val;
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} else {
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const uint32_t curve_ix_mod = curve_ix & (pixels_per_t - 1);
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dst_val |= ((src_val >> dst_src_shift) & dst_val_mask) << (dst_bits_per_pixel * curve_ix_mod);
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if (curve_ix_mod == (pixels_per_t - 1)) {
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dst[curve_ix / pixels_per_t] = dst_val;
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dst_val = 0;
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}
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}
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}
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}
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*/
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}
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