From a86b6690f072742367ade5ad5c55f80b28c95bdf Mon Sep 17 00:00:00 2001
From: Eugen Wissner <belka@caraus.de>
Date: Tue, 12 Jun 2018 20:19:06 +0200
Subject: [PATCH] Implement auto-decoding free equal comparison

Fix #39.
---
 arch/x64/linux/memory/cmp.S         |  1 +
 source/tanya/algorithm/comparison.d | 61 +++++++++++++++++++++++++++++
 source/tanya/container/array.d      |  1 -
 source/tanya/container/list.d       |  3 +-
 source/tanya/container/string.d     |  2 +-
 source/tanya/math/mp.d              |  2 +-
 source/tanya/memory/op.d            |  5 +++
 7 files changed, 70 insertions(+), 5 deletions(-)

diff --git a/arch/x64/linux/memory/cmp.S b/arch/x64/linux/memory/cmp.S
index 169e2eb..64d3ca6 100644
--- a/arch/x64/linux/memory/cmp.S
+++ b/arch/x64/linux/memory/cmp.S
@@ -47,6 +47,7 @@ _D5tanya6memory2op9cmpMemoryFNaNbNixAvxAvZi:
 
 	aligned_1: // Compare the remaining bytes
 		mov %rdx, %rcx
+		cmp $0x0, %rcx
 
 		repe cmpsb
 		jl less
diff --git a/source/tanya/algorithm/comparison.d b/source/tanya/algorithm/comparison.d
index f8e1c60..61dbcf6 100644
--- a/source/tanya/algorithm/comparison.d
+++ b/source/tanya/algorithm/comparison.d
@@ -16,6 +16,7 @@ module tanya.algorithm.comparison;
 
 import tanya.algorithm.mutation;
 import tanya.math : isNaN;
+import tanya.memory.op;
 import tanya.meta.metafunction;
 import tanya.meta.trait;
 import tanya.meta.transform;
@@ -270,3 +271,63 @@ if (isForwardRange!Range && isOrderingComparable!(ElementType!Range))
         assert(max(s2, s3).s == 3);
     }
 }
+
+/**
+ * Compares element-wise two ranges for equality.
+ *
+ * If the ranges have different lengths, they aren't equal.
+ *
+ * Params:
+ *  R1     = First range type.
+ *  R2     = Second range type.
+ *  range1 = First range.
+ *  range2 = Second range.
+ *
+ * Returns: $(D_KEYWORD true) if both ranges are equal, $(D_KEYWORD false)
+ *          otherwise.
+ */
+bool equal(R1, R2)(R1 r1, R2 r2)
+if (allSatisfy!(isInputRange, R1, R2) && is(typeof(r1.front == r2.front)))
+{
+    static if (isDynamicArray!R1
+            && is(R1 == R2)
+            && __traits(isPOD, ElementType!R1))
+    {
+        return cmp(r1, r2) == 0;
+    }
+    else
+    {
+        static if (hasLength!R1 && hasLength!R2)
+        {
+            if (r1.length != r2.length)
+            {
+                return false;
+            }
+        }
+        for (; !r1.empty && !r2.empty; r1.popFront(), r2.popFront())
+        {
+            if (r1.front != r2.front)
+            {
+                return false;
+            }
+        }
+        static if (hasLength!R1 && hasLength!R2)
+        {
+            return true;
+        }
+        else
+        {
+            return r1.empty && r2.empty;
+        }
+    }
+}
+
+///
+@nogc nothrow pure @safe unittest
+{
+    int[2] range1 = [1, 2];
+    assert(equal(range1[], range1[]));
+
+    int[3] range2 = [1, 2, 3];
+    assert(!equal(range1[], range2[]));
+}
diff --git a/source/tanya/container/array.d b/source/tanya/container/array.d
index 8f34847..59cc3fb 100644
--- a/source/tanya/container/array.d
+++ b/source/tanya/container/array.d
@@ -15,7 +15,6 @@
 module tanya.container.array;
 
 import core.checkedint;
-import std.algorithm.comparison : equal;
 import std.algorithm.mutation : bringToFront,
                                 copy,
                                 fill,
diff --git a/source/tanya/container/list.d b/source/tanya/container/list.d
index 23467e5..64ea740 100644
--- a/source/tanya/container/list.d
+++ b/source/tanya/container/list.d
@@ -15,7 +15,6 @@
  */
 module tanya.container.list;
 
-import std.algorithm.comparison : equal;
 import std.algorithm.searching;
 import tanya.algorithm.comparison;
 import tanya.algorithm.mutation;
@@ -574,7 +573,7 @@ struct SList(T)
      */
     bool opEquals()(auto ref typeof(this) that) inout
     {
-        return equal(this[], that[]);
+        return equal(opIndex(), that[]);
     }
 
     ///
diff --git a/source/tanya/container/string.d b/source/tanya/container/string.d
index 54c0200..ad8fa82 100644
--- a/source/tanya/container/string.d
+++ b/source/tanya/container/string.d
@@ -26,7 +26,7 @@
  */
 module tanya.container.string;
 
-import std.algorithm.comparison : cmp, equal;
+import std.algorithm.comparison : cmp;
 import std.algorithm.mutation : bringToFront, copy;
 import std.algorithm.searching;
 import tanya.algorithm.comparison;
diff --git a/source/tanya/math/mp.d b/source/tanya/math/mp.d
index b98fbd7..ae365de 100644
--- a/source/tanya/math/mp.d
+++ b/source/tanya/math/mp.d
@@ -14,7 +14,7 @@
  */
 module tanya.math.mp;
 
-import std.algorithm.comparison : cmp, equal;
+import std.algorithm.comparison : cmp;
 import std.algorithm.mutation : copy, fill, reverse;
 import std.range;
 import tanya.algorithm.comparison;
diff --git a/source/tanya/memory/op.d b/source/tanya/memory/op.d
index 0a73020..ec9bc2e 100644
--- a/source/tanya/memory/op.d
+++ b/source/tanya/memory/op.d
@@ -40,6 +40,11 @@ version (TanyaNative)
         fillMemory(buffer[1 .. $], 0);
         assert(buffer[0] == 1 && buffer[1] == 0);
     }
+
+    @nogc nothrow pure @safe unittest
+    {
+        assert(cmp(null, null) == 0);
+    }
 }
 
 private enum alignMask = size_t.sizeof - 1;