Improve Bignum documentation
Signed-off-by: Janos Follath <janos.follath@arm.com>
diff --git a/library/bignum_core.h b/library/bignum_core.h
index 622f018..2141640 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -54,8 +54,8 @@
/** Import X from unsigned binary data, little endian.
*
- * This function is guaranteed to return an MPI with at least 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.
* \param nx The number of limbs of \p X.
@@ -73,8 +73,8 @@
/** Import X from unsigned binary data, big endian.
*
- * 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.
* \param nx The number of limbs of \p X.
@@ -94,7 +94,7 @@
*
* \param X The address of the MPI.
* \param nx The number of limbs of \p X.
- * \param buf The output buffer to import.
+ * \param buf The output buffer to export to.
* \param buflen The length in bytes of \p buf.
*
* \return \c 0 if successful.
@@ -110,7 +110,7 @@
*
* \param X The address of the MPI.
* \param nx The number of limbs of \p X.
- * \param buf The output buffer to import.
+ * \param buf The output buffer to export to.
* \param buflen The length in bytes of \p buf.
*
* \return \c 0 if successful.
diff --git a/library/bignum_mod.h b/library/bignum_mod.h
index a4f0248..254a744 100644
--- a/library/bignum_mod.h
+++ b/library/bignum_mod.h
@@ -67,13 +67,19 @@
/** Setup a residue structure.
*
* \param r The address of residue to setup. The size is determined by \p m.
- * \param m The address of a modulus related to \p r.
- * \param p The address of the MPI used for \p r.
+ * (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 r.
+ * \param p The address of the limb array storing the value of \p r. The
+ * memory pointed by \p p will be used by \p r and must not be
+ * freed or written until after mbedtls_mpi_mod_residue_release()
+ * is called.
* \param pn The number of limbs of \p p.
*
* \return \c 0 if successful.
- * \return #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if \p r, \p m or \p p is
- * #NULL pointer or if \p p is less then \p m.
+ * \return #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if \p r, \p m or \p p is #NULL
+ * pointer, \p pn is less than the limbs in \p m or if \p p is not
+ * less than \p m.
*/
int mbedtls_mpi_mod_residue_setup( mbedtls_mpi_mod_residue *r,
mbedtls_mpi_mod_modulus *m,
@@ -82,6 +88,12 @@
/** Unbind elements of a residue structure.
*
+ * This function removes the reference to the limb array that was passed to
+ * mbedtls_mpi_mod_residue_setup() to make it safe to free or use again.
+ *
+ * This function invalidates \p r and it must not be used until after
+ * mbedtls_mpi_mod_residue_setup() is called on it again.
+ *
* \param r The address of residue to release.
*/
void mbedtls_mpi_mod_residue_release( mbedtls_mpi_mod_residue *r );
@@ -95,10 +107,15 @@
/** Setup a residue structure.
*
* \param m The address of a modulus.
- * \param p The address of the MPI used for \p m.
+ * \param p The address of the limb array storing the value of \p m. The
+ * memory pointed by \p p will be used by \p r and must not be
+ * freed or written until after
+ * mbedtls_mpi_mod_modulus_free() is called.
* \param pn The number of limbs of \p p.
- * \param ext_rep The external representation of \p m (eg. byte order).
- * \param int_rep The selector which representation is used.
+ * \param ext_rep The external representation to be used for residues
+ * associated with \p m (see #mbedtls_mpi_mod_ext_rep).
+ * \param int_rep The internal representation to be used for residues
+ * associated with \p m (see #mbedtls_mpi_mod_rep_selector).
*
* \return \c 0 if successful.
* \return #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if \p m or \p p is
@@ -110,7 +127,13 @@
int ext_rep,
int int_rep );
-/** Unbind elements of a modulus structure.
+/** Free elements of a modulus structure.
+ *
+ * This function frees any memory allocated by mbedtls_mpi_mod_modulus_setup().
+ *
+ * \warning This function does not free the limb array passed to
+ * mbedtls_mpi_mod_modulus_setup() only removes the reference to it,
+ * making it safe to free or to use it again.
*
* \param m The address of a modulus.
*/
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.
diff --git a/library/bignum_new.c b/library/bignum_new.c
index d1253f8..2613941 100644
--- a/library/bignum_new.c
+++ b/library/bignum_new.c
@@ -313,8 +313,8 @@
/*
* Import X from unsigned binary data, little endian
*
- * This function is guaranteed to return an MPI with at least 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).
*/
int mbedtls_mpi_core_read_le( mbedtls_mpi_uint *X,
size_t nx,
@@ -338,8 +338,8 @@
/*
* Import X from unsigned binary data, big endian
*
- * 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).
*/
int mbedtls_mpi_core_read_be( mbedtls_mpi_uint *X,
size_t nx,