[RELEASE] u22-v03

This version is submitted to U22 breau.

util/chaos/CMakeLists.txt

@@ -0,0 +1,7 @@
+add_library(chaos
+  abchash.c
+  xorshift.c
+)
+target_link_libraries(chaos
+  math
+)

util/chaos/abchash.c

@@ -0,0 +1,32 @@
+#include "./abchash.h"
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#define CHAOS_ABCHASH_GET_CODE(c) (  \
+      ('0' <= c && c <= '9')? c-'0':      \
+      ('a' <= c && c <= 'z')? c-'a'+10:   \
+      (c == '_')       ? 36: UINT8_MAX)
+
+#define CHAOS_ABCHASH_MAX_CODE 36
+
+uint64_t chaos_abchash(const char* str, size_t len) {
+  assert(chaos_abchash_validate(str, len));
+
+  uint64_t ans = 0;
+  for (size_t i = 0; i < len; ++i) {
+    ans = ans*(CHAOS_ABCHASH_MAX_CODE+1) + CHAOS_ABCHASH_GET_CODE(str[i]);
+  }
+  return ans;
+}
+
+bool chaos_abchash_validate(const char* str, size_t len) {
+  for (size_t i = 0; i < len; ++i) {
+    if (CHAOS_ABCHASH_GET_CODE(str[i]) > CHAOS_ABCHASH_MAX_CODE) {
+      return false;
+    }
+  }
+  return len > 0;
+}

util/chaos/abchash.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+/* DON'T EXPECT THIS ALGORITHM TO BE ONE-WAY */
+
+uint64_t
+chaos_abchash(
+    const char* str,
+    size_t      len
+);
+
+bool
+chaos_abchash_validate(
+    const char* str,
+    size_t      len
+);

util/chaos/xorshift.c

@@ -0,0 +1,19 @@
+#include "./xorshift.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+uint64_t chaos_xorshift(uint64_t seed) {
+  seed = seed ^ (seed << 13);
+  seed = seed ^ (seed >>  7);
+  return seed ^ (seed << 17);
+}
+
+float chaos_xorshift_fract(uint64_t seed, uint64_t* next_seed) {
+  static const uint64_t period = 10000;
+
+  seed = chaos_xorshift(seed);
+  if (next_seed != NULL) *next_seed = seed;
+
+  return seed%period*1.f/period;
+}

util/chaos/xorshift.h

@@ -0,0 +1,14 @@
+#pragma once
+
+#include <stdint.h>
+
+uint64_t
+chaos_xorshift(
+    uint64_t seed
+);
+
+float
+chaos_xorshift_fract(
+    uint64_t  seed,
+    uint64_t* next_seed  /* NULLABLE */
+);