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// This file is part of the 64k demo project.
// Tests for the ANS (rANS) entropy coder in util/ans.h.
// Encoder is enabled in tests via ANS_ENABLE_ENCODER.
#include "util/ans.h"
#include <cassert>
#include <cstdint>
#include <cstdio>
#include <cstring>
#include <random>
#include <string>
#include <vector>
namespace {
bool RoundtripCheck(const std::vector<uint8_t>& input,
const uint32_t* initial_counts, const char* label) {
std::vector<uint8_t> compressed;
if (!ans::Encode(input.data(), input.size(), &compressed, initial_counts)) {
fprintf(stderr, "[%s] Encode failed\n", label);
return false;
}
std::vector<uint8_t> decoded(input.size());
size_t decoded_size = 0;
if (!ans::Decode(compressed.data(), compressed.size(), decoded.data(),
decoded.size(), &decoded_size, initial_counts)) {
fprintf(stderr, "[%s] Decode failed\n", label);
return false;
}
if (decoded_size != input.size() ||
std::memcmp(decoded.data(), input.data(), input.size()) != 0) {
fprintf(stderr, "[%s] payload mismatch\n", label);
return false;
}
const double ratio =
input.empty() ? 0.0 : (double)compressed.size() / (double)input.size();
fprintf(stderr, "[%s] OK: %zu -> %zu bytes (%.3f x)\n", label, input.size(),
compressed.size(), ratio);
return true;
}
// Covers: empty / single byte / single-symbol run / all-zeros / random uniform
// / random skewed / repeated ASCII. Each is a roundtrip with default (uniform)
// initial counts.
void TestRoundtripVariants() {
std::mt19937 rng_uniform(12345);
std::vector<uint8_t> random_uniform(64 * 1024);
for (auto& b : random_uniform)
b = (uint8_t)(rng_uniform() & 0xff);
std::mt19937 rng_skewed(67890);
std::vector<uint8_t> random_skewed(32 * 1024);
for (auto& b : random_skewed) {
// 90% byte 'A', 10% other ASCII letters.
const uint32_t r = rng_skewed();
b = (r % 10 == 0) ? (uint8_t)('B' + (r >> 8) % 25) : (uint8_t)'A';
}
const char* ascii =
"@group(0) @binding(0) var smplr: sampler;\n"
"@group(0) @binding(1) var tex: texture_2d<f32>;\n"
"@fragment fn fs_main(@builtin(position) p: vec4f) -> @location(0) "
"vec4f {\n"
" let uv = p.xy / vec2f(1280.0, 720.0);\n"
" return textureSample(tex, smplr, uv);\n"
"}\n";
std::vector<uint8_t> ascii_block;
for (int i = 0; i < 50; ++i) { // cross chunk boundary
ascii_block.insert(ascii_block.end(), ascii, ascii + std::strlen(ascii));
}
struct Case {
const char* label;
std::vector<uint8_t> data;
};
const Case cases[] = {
{"empty", {}},
{"single-byte", {0x42}},
{"single-symbol-run", std::vector<uint8_t>(4096, 'A')},
{"all-zeros", std::vector<uint8_t>(8192, 0)},
{"random-uniform", random_uniform},
{"random-skewed", random_skewed},
{"ascii-shader-text", ascii_block},
};
for (const Case& c : cases) {
assert(RoundtripCheck(c.data, nullptr, c.label));
}
}
// Seeded initial counts should compress a matching corpus at least as well
// as uniform init, and roundtrip identically.
void TestSeededInitialCounts() {
std::vector<uint8_t> corpus;
const char* sample = "fn main() { let x = vec3f(1.0, 2.0, 3.0); }\n";
for (int i = 0; i < 200; ++i) {
corpus.insert(corpus.end(), sample, sample + std::strlen(sample));
}
uint32_t hist[256] = {};
ans::Histogram(corpus.data(), corpus.size(), hist);
std::vector<uint8_t> seeded_out, uniform_out;
assert(ans::Encode(corpus.data(), corpus.size(), &seeded_out, hist));
assert(ans::Encode(corpus.data(), corpus.size(), &uniform_out, nullptr));
std::vector<uint8_t> decoded(corpus.size());
size_t decoded_size = 0;
assert(ans::Decode(seeded_out.data(), seeded_out.size(), decoded.data(),
decoded.size(), &decoded_size, hist));
assert(decoded_size == corpus.size());
assert(std::memcmp(decoded.data(), corpus.data(), corpus.size()) == 0);
fprintf(stderr, "[seeded-vs-uniform] seeded=%zu uniform=%zu raw=%zu\n",
seeded_out.size(), uniform_out.size(), corpus.size());
assert(seeded_out.size() <= uniform_out.size());
}
// The chunk-end state check must reject: a mismatched model (decoder uses a
// different initial distribution), a single bit-flip in the payload, and a
// truncated stream.
void TestRejection() {
std::mt19937 rng(1);
// 1) Mismatched models.
{
std::vector<uint8_t> v(4096);
for (auto& b : v)
b = (uint8_t)('a' + (rng() % 26));
uint32_t hist[256] = {};
ans::Histogram(v.data(), v.size(), hist);
std::vector<uint8_t> encoded;
assert(ans::Encode(v.data(), v.size(), &encoded, hist));
std::vector<uint8_t> decoded(v.size());
size_t decoded_size = 0;
assert(!ans::Decode(encoded.data(), encoded.size(), decoded.data(),
decoded.size(), &decoded_size, nullptr));
fprintf(stderr, "[rejection] mismatched-counts OK\n");
}
// 2) Corruption.
{
std::vector<uint8_t> v(2048);
for (auto& b : v)
b = (uint8_t)(rng() & 0xff);
std::vector<uint8_t> encoded;
assert(ans::Encode(v.data(), v.size(), &encoded, nullptr));
encoded[encoded.size() / 2] ^= 0x55; // flip a payload byte
std::vector<uint8_t> decoded(v.size());
size_t decoded_size = 0;
assert(!ans::Decode(encoded.data(), encoded.size(), decoded.data(),
decoded.size(), &decoded_size, nullptr));
fprintf(stderr, "[rejection] corruption OK\n");
}
// 3) Truncation.
{
std::vector<uint8_t> v(4096);
for (size_t i = 0; i < v.size(); ++i)
v[i] = (uint8_t)i;
std::vector<uint8_t> encoded;
assert(ans::Encode(v.data(), v.size(), &encoded, nullptr));
encoded.resize(encoded.size() - 8);
std::vector<uint8_t> decoded(v.size());
size_t decoded_size = 0;
assert(!ans::Decode(encoded.data(), encoded.size(), decoded.data(),
decoded.size(), &decoded_size, nullptr));
fprintf(stderr, "[rejection] truncation OK\n");
}
}
void TestPeekSize() {
std::vector<uint8_t> v(1234, 'Q');
std::vector<uint8_t> encoded;
assert(ans::Encode(v.data(), v.size(), &encoded, nullptr));
assert(ans::PeekUncompressedSize(encoded.data(), encoded.size()) == v.size());
}
} // namespace
int main() {
TestRoundtripVariants();
TestSeededInitialCounts();
TestRejection();
TestPeekSize();
fprintf(stderr, "All ANS tests passed.\n");
return 0;
}
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