Improve Bignum documentation
Signed-off-by: Janos Follath <janos.follath@arm.com>
diff --git a/library/bignum_mod_raw.h b/library/bignum_mod_raw.h
index 8f0f0f2..85ca533 100644
--- a/library/bignum_mod_raw.h
+++ b/library/bignum_mod_raw.h
@@ -28,11 +28,13 @@
/** Import X from unsigned binary data.
*
- * This function is guaranteed to return an MPI with exactly the necessary
- * number of limbs (in particular, it does not skip 0s in the input).
+ * The MPI needs to have enough limbs to store the full value (in particular,
+ * this function does not skip 0s in the input).
*
- * \param X The address of the MPI. The size is determined by \p m.
- * \param m The address of a modulus related to \p X.
+ * \param X The address of the MPI. The size is determined by \p m. (In
+ * particular, it must have at least as many limbs as the modulus
+ * \p m.)
+ * \param m The address of the modulus related to \p X.
* \param buf The input buffer to import from.
* \param buflen The length in bytes of \p buf.
*
@@ -40,7 +42,7 @@
* \return #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p X isn't
* large enough to hold the value in \p buf.
* \return #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if the external representation
- * of \p m is invalid or \p X is less then \p m.
+ * of \p m is invalid or \p X is not less than \p m.
*/
int mbedtls_mpi_mod_raw_read( mbedtls_mpi_uint *X,
mbedtls_mpi_mod_modulus *m,
@@ -49,9 +51,11 @@
/** Export X into unsigned binary data.
*
- * \param X The address of the MPI. The size is determined by \p m.
- * \param m The address of a modulus related to \p X.
- * \param buf The output buffer to import.
+ * \param X The address of the MPI. The size is determined by \p m. (In
+ * particular, it must have at least as many limbs as the modulus
+ * \p m.)
+ * \param m The address of the modulus related to \p X.
+ * \param buf The output buffer to export to.
* \param buflen The length in bytes of \p buf.
*
* \return \c 0 if successful.