LibCrypto: Simplify and move CRC32 table to cpp file

CRC32 table is generated at compile-time and put into a static
variable in the header file. This can be moved to be a function
instead of a class, be moved to the `.cpp` file` and generated as an
array instead of a class which only implements `operator[]`.

2 files changed, 24 insertions, 31 deletions

diff --git a/Userland/Libraries/LibCrypto/Checksum/CRC32.cpp b/Userland/Libraries/LibCrypto/Checksum/CRC32.cpp
index 84201aa724..0a0ed2e861 100644
--- a/Userland/Libraries/LibCrypto/Checksum/CRC32.cpp
+++ b/Userland/Libraries/LibCrypto/Checksum/CRC32.cpp
@@ -1,15 +1,37 @@
 /*
- * Copyright (c) 2020, the SerenityOS developers.
+ * Copyright (c) 2020-2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/Array.h>
 #include <AK/Span.h>
 #include <AK/Types.h>
 #include <LibCrypto/Checksum/CRC32.h>
 
 namespace Crypto::Checksum {
 
+static constexpr auto generate_table()
+{
+    Array<u32, 256> data {};
+    for (auto i = 0u; i < data.size(); i++) {
+        u32 value = i;
+
+        for (auto j = 0; j < 8; j++) {
+            if (value & 1) {
+                value = 0xEDB88320 ^ (value >> 1);
+            } else {
+                value = value >> 1;
+            }
+        }
+
+        data[i] = value;
+    }
+    return data;
+}
+
+static constexpr auto table = generate_table();
+
 void CRC32::update(ReadonlyBytes data)
 {
     for (size_t i = 0; i < data.size(); i++) {
diff --git a/Userland/Libraries/LibCrypto/Checksum/CRC32.h b/Userland/Libraries/LibCrypto/Checksum/CRC32.h
index e2913527fd..8853c38a52 100644
--- a/Userland/Libraries/LibCrypto/Checksum/CRC32.h
+++ b/Userland/Libraries/LibCrypto/Checksum/CRC32.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, the SerenityOS developers.
+ * Copyright (c) 2020-2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -12,35 +12,6 @@
 
 namespace Crypto::Checksum {
 
-struct Table {
-    u32 data[256];
-
-    constexpr Table()
-        : data()
-    {
-        for (auto i = 0; i < 256; i++) {
-            u32 value = i;
-
-            for (auto j = 0; j < 8; j++) {
-                if (value & 1) {
-                    value = 0xEDB88320 ^ (value >> 1);
-                } else {
-                    value = value >> 1;
-                }
-            }
-
-            data[i] = value;
-        }
-    }
-
-    constexpr u32 operator[](int index) const
-    {
-        return data[index];
-    }
-};
-
-constexpr static auto table = Table();
-
 class CRC32 : public ChecksumFunction<u32> {
 public:
     CRC32() { }