From 0baa90d641ff8763e8258e73da44421b53567bce Mon Sep 17 00:00:00 2001
From: PixelyIon <pixelyion@protonmail.com>
Date: Fri, 15 Apr 2022 20:37:01 +0530
Subject: [PATCH] Implement `SpanEqual` and `SpanHash`

We desire the ability to hash and check equality of data across spans to use associative containers such as `std::unordered_map` with spans. The implemented functions provide an easy way to do that.
---
 app/src/main/cpp/skyline/common/span.h | 28 +++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/app/src/main/cpp/skyline/common/span.h b/app/src/main/cpp/skyline/common/span.h
index 2904adf7..131a1a37 100644
--- a/app/src/main/cpp/skyline/common/span.h
+++ b/app/src/main/cpp/skyline/common/span.h
@@ -82,7 +82,7 @@ namespace skyline {
         /**
          * @return If a supplied span is located entirely inside this span and is effectively a subspan
          */
-        constexpr bool contains(const span<T, Extent>& other) const {
+        constexpr bool contains(const span<T, Extent> &other) const {
             return this->begin() <= other.begin() && this->end() >= other.end();
         }
 
@@ -95,7 +95,7 @@ namespace skyline {
 
         /** Comparision operators for equality and binary searches **/
 
-        constexpr bool operator==(const span<T, Extent>& other) const {
+        constexpr bool operator==(const span<T, Extent> &other) const {
             return this->data() == other.data() && this->size() == other.size();
         }
 
@@ -103,7 +103,7 @@ namespace skyline {
             return this->data() < other.data();
         }
 
-        constexpr bool operator<(T* pointer) const {
+        constexpr bool operator<(T *pointer) const {
             return this->data() < pointer;
         }
 
@@ -155,4 +155,26 @@ namespace skyline {
     span(Container &) -> span<typename Container::value_type>;
     template<typename Container>
     span(const Container &) -> span<const typename Container::value_type>;
+
+    /**
+     * @return If the contents of the two spans are byte-for-byte equal
+     */
+    template<typename T, size_t Extent = std::dynamic_extent>
+    struct SpanEqual {
+        constexpr bool operator()(const span<T, Extent> &lhs, const span<T, Extent> &rhs) const {
+            if (lhs.size_bytes() != rhs.size_bytes())
+                return false;
+            return std::equal(lhs.begin(), lhs.end(), rhs.begin());
+        }
+    };
+
+    /**
+     * @return A hash of the contents of the span
+     */
+    template<typename T, size_t Extent = std::dynamic_extent>
+    struct SpanHash {
+        constexpr size_t operator()(const skyline::span<T, Extent> &x) const {
+            return XXH64(x.data(), x.size_bytes(), 0);
+        }
+    };
 }