From 636dfc412f33b05ecfdc375a146cf9cd773b38f2 Mon Sep 17 00:00:00 2001
From: cfif <cham-zod@mail.ru>
Date: Fri, 24 Jan 2025 13:22:33 +0300
Subject: [PATCH] =?UTF-8?q?=D0=9F=D0=B5=D1=80=D0=B5=D0=BD=D0=BE=D1=81=20?=
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---
 Galois256.c  | 128 +++++++++++++++++++++++++++++++++++++++++++++++++++
 Galois256.h  |  35 ++++++++++++++
 modular.json |  10 ++++
 3 files changed, 173 insertions(+)
 create mode 100644 Galois256.c
 create mode 100644 Galois256.h
 create mode 100644 modular.json

diff --git a/Galois256.c b/Galois256.c
new file mode 100644
index 0000000..bf3a268
--- /dev/null
+++ b/Galois256.c
@@ -0,0 +1,128 @@
+//
+// Created by zemon on 22.07.2022.
+//
+#include "Galois256.h"
+#include <memory.h>
+#include "stdint.h"
+
+
+int32_t inline iGalois256Add(tGalois256 *env, int one, int two) {
+    return one ^ two;
+}
+
+int32_t inline iGalois256Sub(tGalois256 *env, int one, int two) {
+    return one ^ two;
+}
+
+
+int32_t iGalois256PowValue(tGalois256 *env, int degree) {
+    int deg_in_bounds;
+
+    if (degree < 0) {
+        deg_in_bounds = env->field_elements_limit - ((degree * -1) % env->field_elements_limit);
+    } else {
+        deg_in_bounds = degree % env->field_elements_limit;
+    }
+
+
+    return env->pow_table[deg_in_bounds];
+}
+
+
+int32_t iGalois256LogValue(tGalois256 *env, int degree) {
+
+    if ((degree <= 0) || (degree > env->field_elements_limit)) {
+//        printf("ERROR! Log out of bounds deg:%i in field len %i", degree, env->field_elements_limit);
+        return -1;
+    }
+
+    return env->log_table[degree];
+}
+
+
+int32_t iGalois256Mul(tGalois256 *env, int one, int two) {
+    if (0 == one || 0 == two) {
+        return 0;
+    }
+    return iGalois256PowValue(env, iGalois256LogValue(env, one) + iGalois256LogValue(env, two));
+}
+
+
+int32_t iGalois256Div(tGalois256 *env, int dividable, int divider) {
+
+    if (divider == 0) {
+//        printf("Division by zero %i/%i", dividable, divider);
+        return -1;
+    }
+
+    if (dividable == 0) {
+        return 0;
+    }
+    return iGalois256PowValue(
+            env,
+            iGalois256LogValue(env, dividable) - iGalois256LogValue(env, divider)
+    );
+}
+
+
+int32_t iGalois256Pow(tGalois256 *env, int base, int degree) {
+
+    if (degree == 0) {
+        return 1;
+    }
+
+    if (base == 0) {
+        return 0;
+    }
+
+    int base_log = iGalois256LogValue(env, base);
+
+    return iGalois256PowValue(env, degree * base_log);
+}
+
+
+void iGalois256GenTables(tGalois256 *env) {
+
+    memset(env->log_table, 0, (env->field_elements_limit + 1) * sizeof(int32_t));
+    memset(env->pow_table, 0, (env->field_elements_limit + 1) * sizeof(int32_t));
+
+    int mask = 1;
+    env->pow_table[env->base_degree] = 0;
+
+    for (int i = 0; i < env->base_degree; i++) {
+        env->pow_table[i] = mask;
+        env->log_table[env->pow_table[i]] = i;
+
+        if (env->irreducible_polynomial[i] != 0) {
+            env->pow_table[env->base_degree] ^= mask;
+        }
+
+        mask <<= 1;
+    }
+
+
+    env->log_table[env->pow_table[env->base_degree]] = env->base_degree;
+    mask >>= 1;
+
+    for (int i = env->base_degree + 1; i < env->field_elements_limit; i++) {
+        if (env->pow_table[i - 1] >= mask) {
+            env->pow_table[i] = env->pow_table[env->base_degree] ^ ((env->pow_table[i - 1] ^ mask) << 1);
+        } else {
+            env->pow_table[i] = env->pow_table[i - 1] << 1;
+        }
+        env->log_table[env->pow_table[i]] = i;
+    }
+
+    env->log_table[0] = -1;
+}
+
+static const uint8_t iGalois256BaseDegree = 8;
+static const uint8_t iGalois256IrreduciblePolynomial[] = {1, 0, 1, 1, 1, 0, 0, 0, 1};
+
+void iGalois256Init(tGalois256 *env) {
+    env->base_degree = iGalois256BaseDegree;
+    env->irreducible_polynomial = (uint8_t *) iGalois256IrreduciblePolynomial;
+    env->field_elements_limit = (0x01 << (uint16_t) iGalois256BaseDegree) - 1;
+
+    iGalois256GenTables(env);
+}
\ No newline at end of file
diff --git a/Galois256.h b/Galois256.h
new file mode 100644
index 0000000..4b16e9e
--- /dev/null
+++ b/Galois256.h
@@ -0,0 +1,35 @@
+//
+// Created by zemon on 24.07.2022.
+//
+
+#ifndef PDM_FIR_TEST_GALOIS256_H
+#define PDM_FIR_TEST_GALOIS256_H
+
+#include "stdint.h"
+
+typedef struct {
+    uint8_t base_degree;
+    uint8_t *irreducible_polynomial;
+    int32_t field_elements_limit;
+    int32_t pow_table[256];
+    int32_t log_table[256];
+
+} tGalois256;
+
+void iGalois256Init(tGalois256 *env);
+
+int32_t iGalois256Add(tGalois256 *env, int one, int two);
+
+int32_t iGalois256Sub(tGalois256 *env, int one, int two);
+
+int32_t iGalois256Mul(tGalois256 *env, int one, int two);
+
+int32_t iGalois256Div(tGalois256 *env, int dividable, int divider);
+
+int32_t iGalois256Pow(tGalois256 *env, int base, int degree);
+
+int32_t iGalois256LogValue(tGalois256 *env, int degree);
+
+int32_t iGalois256PowValue(tGalois256 *env, int degree);
+
+#endif //PDM_FIR_TEST_GALOIS256_H
diff --git a/modular.json b/modular.json
new file mode 100644
index 0000000..0dd1901
--- /dev/null
+++ b/modular.json
@@ -0,0 +1,10 @@
+{
+  "cmake": {
+    "inc_dirs": [
+      "./"
+    ],
+    "srcs": [
+      "./**.c"
+    ]
+  }
+}
\ No newline at end of file