Improve docs for mbedtls_ct_memcmp
Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/include/mbedtls/constant_time.h b/include/mbedtls/constant_time.h
index 01d5d9d..49bb375 100644
--- a/include/mbedtls/constant_time.h
+++ b/include/mbedtls/constant_time.h
@@ -26,16 +26,19 @@
/** Constant-time buffer comparison without branches.
*
* This is equivalent to the standard memcmp function, but is likely to be
- * compiled to code using bitwise operation rather than a branch.
+ * compiled to code using bitwise operation rather than a branch, such that
+ * the time taken is constant w.r.t. the data pointed to by \p a and \p b,
+ * and w.r.t. whether \p a and \p b are equal or not. It is not constant-time
+ * w.r.t. \p n .
*
* This function can be used to write constant-time code by replacing branches
* with bit operations using masks.
*
- * \param a Pointer to the first buffer.
- * \param b Pointer to the second buffer.
- * \param n The number of bytes to compare in the buffer.
+ * \param a Pointer to the first buffer, containing at least \p n bytes. May not be NULL.
+ * \param b Pointer to the second buffer, containing at least \p n bytes. May not be NULL.
+ * \param n The number of bytes to compare.
*
- * \return Zero if the content of the two buffer is the same,
+ * \return Zero if the contents of the two buffers are the same,
* otherwise non-zero.
*/
int mbedtls_ct_memcmp(const void *a,