feat(crypto): ✨ add SodiumString

Runtime/Algorand.Unity.Crypto/SodiumString.cs

@@ -0,0 +1,71 @@
+using System;
+using System.Diagnostics;
+using Unity.Collections;
+using Unity.Jobs;
+
+namespace Algorand.Unity.Crypto
+{
+    public struct SodiumString : INativeDisposable
+    {
+        private readonly SecureMemoryHandle handle;
+
+        private readonly int totalCapacity;
+
+        private int length;
+
+        public bool IsCreated => handle.IsCreated;
+
+        public int Length => length;
+
+        public int Capacity => totalCapacity - 1;
+
+        public unsafe byte* GetUnsafePtr()
+        {
+            return (byte*)handle.GetUnsafePtr();
+        }
+
+        public SodiumString(ReadOnlySpan<char> source)
+        {
+            totalCapacity = source.Length * sizeof(char);
+            var totalCapacityNUint = (UIntPtr)totalCapacity;
+            handle = SecureMemoryHandle.Create(totalCapacityNUint);
+            unsafe
+            {
+                fixed (char* sourceptr = source)
+                {
+                    sodium.sodium_mlock((IntPtr)sourceptr, totalCapacityNUint);
+                    var error = UTF8ArrayUnsafeUtility.Copy(
+                        handle.GetUnsafePtr(),
+                        out length,
+                        totalCapacity - 1,
+                        sourceptr,
+                        source.Length
+                    );
+                    sodium.sodium_munlock((IntPtr)sourceptr, totalCapacityNUint);
+                    if (error != CopyError.None)
+                    {
+                        if (handle.IsCreated) handle.Dispose();
+                        length = 0;
+                        ThrowCopyError(error, source);
+                    }
+                }
+            }
+        }
+
+        public JobHandle Dispose(JobHandle inputDeps)
+        {
+            return handle.Dispose(inputDeps);
+        }
+
+        public void Dispose()
+        {
+            handle.Dispose();
+        }
+
+        [Conditional("ENABLE_UNITY_COLLECTIONS_CHECKS")]
+        void ThrowCopyError(CopyError error, ReadOnlySpan<char> source)
+        {
+            throw new ArgumentException($"NativeText: {error} while copying \"{source.ToString()}\"");
+        }
+    }
+}