1 files changed, 52 insertions, 0 deletions
diff --git a/library/psa_crypto_core_common.h b/library/psa_crypto_core_common.h
new file mode 100644
index 00000000000..98fce2cca4e
--- /dev/null
+++ b/library/psa_crypto_core_common.h
@@ -0,0 +1,52 @@
+/**
+ * \file psa_crypto_core_common.h
+ *
+ * \brief Utility macros for internal use in the PSA cryptography core.
+ */
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+ */
+
+#ifndef PSA_CRYPTO_CORE_COMMON_H
+#define PSA_CRYPTO_CORE_COMMON_H
+
+/** Return an offset into a buffer.
+ *
+ * This is just the addition of an offset to a pointer, except that this
+ * function also accepts an offset of 0 into a buffer whose pointer is null.
+ * (`p + n` has undefined behavior when `p` is null, even when `n == 0`.
+ * A null pointer is a valid buffer pointer when the size is 0, for example
+ * as the result of `malloc(0)` on some platforms.)
+ *
+ * \param p     Pointer to a buffer of at least n bytes.
+ *              This may be \p NULL if \p n is zero.
+ * \param n     An offset in bytes.
+ * \return      Pointer to offset \p n in the buffer \p p.
+ *              Note that this is only a valid pointer if the size of the
+ *              buffer is at least \p n + 1.
+ */
+static inline unsigned char *psa_crypto_buffer_offset(
+    unsigned char *p, size_t n)
+{
+    return p == NULL ? NULL : p + n;
+}
+
+/** Return an offset into a read-only buffer.
+ *
+ * Similar to mbedtls_buffer_offset(), but for const pointers.
+ *
+ * \param p     Pointer to a buffer of at least n bytes.
+ *              This may be \p NULL if \p n is zero.
+ * \param n     An offset in bytes.
+ * \return      Pointer to offset \p n in the buffer \p p.
+ *              Note that this is only a valid pointer if the size of the
+ *              buffer is at least \p n + 1.
+ */
+static inline const unsigned char *psa_crypto_buffer_offset_const(
+    const unsigned char *p, size_t n)
+{
+    return p == NULL ? NULL : p + n;
+}
+
+#endif /* PSA_CRYPTO_CORE_COMMON_H */