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CHANGELOG.md

@@ -1033,6 +1033,7 @@ This release closes the following issue:
 
 ##### Features
 
+-   [`8248b4a`](https://github.com/stdlib-js/stdlib/commit/8248b4a4c72d7a981a72075583561b98646c8068) - add macro to convert a stride to an index offset
 -   [`123f7f9`](https://github.com/stdlib-js/stdlib/commit/123f7f945a9154c7518c6c0837110e0712811b5f) - add `blas/base/diagonal-types`
 -   [`9174c02`](https://github.com/stdlib-js/stdlib/commit/9174c02e42ca651f8959fff0626ae8147a75ee09) - add `blas/base/shared`
 
@@ -2143,6 +2144,8 @@ A total of 35 people contributed to this release. Thank you to the following con
 
 <details>
 
+-   [`5418177`](https://github.com/stdlib-js/stdlib/commit/5418177d92f26a6d99bd53d19713f2fa0d536b27) - **refactor:** use macro to convert stride to offset _(by Athan Reines)_
+-   [`8248b4a`](https://github.com/stdlib-js/stdlib/commit/8248b4a4c72d7a981a72075583561b98646c8068) - **feat:** add macro to convert a stride to an index offset _(by Athan Reines)_
 -   [`c3895df`](https://github.com/stdlib-js/stdlib/commit/c3895df672126473f5803e93b529bcdd0775c75a) - **refactor:** use utility to resolve an index offset _(by Athan Reines)_
 -   [`1654659`](https://github.com/stdlib-js/stdlib/commit/1654659445a6dee281706379770c9cb0498c36c7) - **refactor:** update implementation to reduce code duplication [(#2480)](https://github.com/stdlib-js/stdlib/pull/2480) _(by Aman Bhansali, Athan Reines)_
 -   [`4d08374`](https://github.com/stdlib-js/stdlib/commit/4d0837401b68ebd4e5b8c38e0214158dbe410a07) - **refactor:** reduce code duplication [(#2479)](https://github.com/stdlib-js/stdlib/pull/2479) _(by Aman Bhansali, Athan Reines)_

base/dcopy/src/dcopy.c

@@ -61,16 +61,8 @@ void API_SUFFIX(c_dcopy)( const CBLAS_INT N, const double *X, const CBLAS_INT st
 		}
 		return;
 	}
-	if ( strideX < 0 ) {
-		ix = (1-N) * strideX;
-	} else {
-		ix = 0;
-	}
-	if ( strideY < 0 ) {
-		iy = (1-N) * strideY;
-	} else {
-		iy = 0;
-	}
+	ix = STDLIB_BLAS_BASE_STRIDE2OFFSET( N, strideX );
+	iy = STDLIB_BLAS_BASE_STRIDE2OFFSET( N, strideY );
 	for ( i = 0; i < N; i++ ) {
 		Y[ iy ] = X[ ix ];
 		ix += strideX;

base/shared/include/stdlib/blas/base/shared.h

@@ -20,5 +20,6 @@
 #define STDLIB_BLAS_BASE_SHARED_H
 
 #include "shared/cblas.h"
+#include "shared/macros.h"
 
 #endif // !STDLIB_BLAS_BASE_SHARED_H

base/shared/include/stdlib/blas/base/shared/macros.h

@@ -0,0 +1,47 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2023 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+#ifndef STDLIB_BLAS_BASE_SHARED_MACROS_H
+#define STDLIB_BLAS_BASE_SHARED_MACROS_H
+
+/*
+* If C++, prevent name mangling so that the compiler emits a binary file having undecorated names, thus mirroring the behavior of a C compiler.
+*/
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+* Macro for converting a stride to an index offset.
+*
+* @param N         number of indexed elements
+* @param stride    index increment
+*
+* @example
+* #include <stdint.h>
+*
+* int64_t offset = STDLIB_BLAS_BASE_STRIDE2OFFSET( 10, -10 );
+* // returns 90
+*/
+#define STDLIB_BLAS_BASE_STRIDE2OFFSET( N, stride ) ( ( (stride) > 0 ) ? 0 : ( 1-(N) ) * (stride) )
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // !STDLIB_BLAS_BASE_SHARED_MACROS_H