From f444a999ba669b086dacde440368227a624f8d23 Mon Sep 17 00:00:00 2001
From: Alex Barney <thealexbarney@gmail.com>
Date: Sun, 11 Jul 2021 22:37:44 -0700
Subject: [PATCH] Add misc helper functions and fix null assertion text

---
 src/LibHac/Common/SpanHelpers.cs   | 27 ++++++++++++++++++++++++
 src/LibHac/Diag/Impl/AssertImpl.cs |  8 ++++----
 src/LibHac/Util/StringUtils.cs     | 33 ++++++++++++++++++++++++++++++
 3 files changed, 64 insertions(+), 4 deletions(-)

diff --git a/src/LibHac/Common/SpanHelpers.cs b/src/LibHac/Common/SpanHelpers.cs
index 700ab9bd..fd0543ad 100644
--- a/src/LibHac/Common/SpanHelpers.cs
+++ b/src/LibHac/Common/SpanHelpers.cs
@@ -4,6 +4,33 @@ using System.Runtime.InteropServices;
 
 namespace LibHac.Common
 {
+    public static class SpanExtensions
+    {
+        /// <summary>
+        /// Gets the element at the specified zero-based index or gets 0 if the index is out-of-bounds.
+        /// </summary>
+        /// <param name="span">The <see cref="ReadOnlySpan{T}"/> containing the element to get.</param>
+        /// <param name="i">The zero-based index of the element.</param>
+        /// <returns>The element at the specified index or 0 if out-of-bounds.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static byte At(in this ReadOnlySpan<byte> span, int i)
+        {
+            return (uint)i >= (uint)span.Length ? (byte)0 : span[i];
+        }
+
+        /// <summary>
+        /// Gets the element at the specified zero-based index or gets 0 if the index is out-of-bounds.
+        /// </summary>
+        /// <param name="span">The <see cref="Span{T}"/> containing the element to get.</param>
+        /// <param name="i">The zero-based index of the element.</param>
+        /// <returns>The element at the specified index or 0 if out-of-bounds.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static byte At(in this Span<byte> span, int i)
+        {
+            return (uint)i >= (uint)span.Length ? (byte)0 : span[i];
+        }
+    }
+
     public static class SpanHelpers
     {
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
diff --git a/src/LibHac/Diag/Impl/AssertImpl.cs b/src/LibHac/Diag/Impl/AssertImpl.cs
index 351d2e9a..69c06d37 100644
--- a/src/LibHac/Diag/Impl/AssertImpl.cs
+++ b/src/LibHac/Diag/Impl/AssertImpl.cs
@@ -10,14 +10,14 @@ namespace LibHac.Diag.Impl
         internal static void InvokeAssertionNotNull(AssertionType assertionType, string valueText, string functionName,
             string fileName, int lineNumber)
         {
-            Assert.OnAssertionFailure(assertionType, valueText, functionName, fileName, lineNumber,
+            Assert.OnAssertionFailure(assertionType, "NotNull", functionName, fileName, lineNumber,
                 $"{valueText} must not be nullptr.");
         }
 
         internal static void InvokeAssertionNull(AssertionType assertionType, string valueText, string functionName,
             string fileName, int lineNumber)
         {
-            Assert.OnAssertionFailure(assertionType, valueText, functionName, fileName, lineNumber,
+            Assert.OnAssertionFailure(assertionType, "Null", functionName, fileName, lineNumber,
                 $"{valueText} must be nullptr.");
         }
 
@@ -137,12 +137,12 @@ namespace LibHac.Diag.Impl
 
         public static bool NotNull<T>(Span<T> span)
         {
-            return !Unsafe.IsNullRef(ref MemoryMarshal.GetReference(span));
+            return !Unsafe.IsNullRef(ref MemoryMarshal.GetReference(span)) || span.Length == 0;
         }
 
         public static bool NotNull<T>(ReadOnlySpan<T> span)
         {
-            return !Unsafe.IsNullRef(ref MemoryMarshal.GetReference(span));
+            return !Unsafe.IsNullRef(ref MemoryMarshal.GetReference(span)) || span.Length == 0;
         }
 
         public static bool WithinRange(int value, int lowerInclusive, int upperExclusive)
diff --git a/src/LibHac/Util/StringUtils.cs b/src/LibHac/Util/StringUtils.cs
index 52d0154b..145d3497 100644
--- a/src/LibHac/Util/StringUtils.cs
+++ b/src/LibHac/Util/StringUtils.cs
@@ -22,6 +22,22 @@ namespace LibHac.Util
             return i;
         }
 
+        public static int Copy(Span<byte> dest, ReadOnlySpan<byte> source, int maxLen)
+        {
+            int maxLenLocal = Math.Min(Math.Min(dest.Length, source.Length), maxLen);
+
+            int i;
+            for (i = 0; i < maxLenLocal && source[i] != 0; i++)
+                dest[i] = source[i];
+
+            if (i < dest.Length)
+            {
+                dest[i] = 0;
+            }
+
+            return i;
+        }
+
         public static int GetLength(ReadOnlySpan<byte> s)
         {
             int i = 0;
@@ -160,6 +176,23 @@ namespace LibHac.Util
             return iDest;
         }
 
+        public static int Find(ReadOnlySpan<byte> haystack, ReadOnlySpan<byte> needle)
+        {
+            if (needle.Length == 0)
+                return 0;
+
+            for (int i = 0; i <= haystack.Length - needle.Length; i++)
+            {
+                int j;
+                for (j = 0; j < needle.Length && haystack[i + j] == needle[j]; j++) { }
+
+                if (j == needle.Length)
+                    return i;
+            }
+
+            return -1;
+        }
+
         public static ReadOnlySpan<byte> StringToUtf8(string value)
         {
             return Encoding.UTF8.GetBytes(value).AsSpan();