psa_internal_export_key function for common code.

create psa_internal_export_key function for common code in psa_export_key and psa_export_public_key.
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 0fa4000..7f18bd4 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -457,23 +457,28 @@
     return( PSA_SUCCESS );
 }
 
-psa_status_t psa_export_key(psa_key_slot_t key,
-                            uint8_t *data,
-                            size_t data_size,
-                            size_t *data_length)
+
+static  psa_status_t psa_internal_export_key(psa_key_slot_t key,
+                                             uint8_t *data,
+                                             size_t data_size,
+                                             size_t *data_length,
+                                             int export_public_key)
 {
     key_slot_t *slot;
 
     if( key == 0 || key > MBEDTLS_PSA_KEY_SLOT_COUNT )
         return( PSA_ERROR_EMPTY_SLOT );
-    slot = &global_data.key_slots[key];
+    slot = &global_data.key_slots[ key ];
     if( slot->type == PSA_KEY_TYPE_NONE )
         return( PSA_ERROR_EMPTY_SLOT );
-
+		
     if( !( slot->policy.usage & PSA_KEY_USAGE_EXPORT ) )
         return( PSA_ERROR_NOT_PERMITTED );
+		
+    if( ( export_public_key ) && ( !( PSA_KEY_TYPE_IS_PUBLIC_KEY( slot->type ) || PSA_KEY_TYPE_IS_KEYPAIR( slot->type ) ) ) )
+        return( PSA_ERROR_INVALID_ARGUMENT );
 
-    if( PSA_KEY_TYPE_IS_RAW_BYTES( slot->type ) )
+    if( ( !export_public_key) && PSA_KEY_TYPE_IS_RAW_BYTES( slot->type ) )
     {
         if( slot->data.raw.bytes > data_size )
             return( PSA_ERROR_BUFFER_TOO_SMALL );
@@ -483,41 +488,51 @@
     }
     else
 #if defined(MBEDTLS_PK_WRITE_C)
-    if( slot->type == PSA_KEY_TYPE_RSA_PUBLIC_KEY ||
-        slot->type == PSA_KEY_TYPE_RSA_KEYPAIR ||
-        PSA_KEY_TYPE_IS_ECC( slot->type ) )
-    {
-        mbedtls_pk_context pk;
-        int ret;
-        mbedtls_pk_init( &pk );
         if( slot->type == PSA_KEY_TYPE_RSA_PUBLIC_KEY ||
-            slot->type == PSA_KEY_TYPE_RSA_KEYPAIR )
+            slot->type == PSA_KEY_TYPE_RSA_KEYPAIR ||
+            PSA_KEY_TYPE_IS_ECC( slot->type ) )
         {
-            pk.pk_info = &mbedtls_rsa_info;
-            pk.pk_ctx = slot->data.rsa;
+            mbedtls_pk_context pk;
+            int ret;
+            mbedtls_pk_init( &pk );
+            if( slot->type == PSA_KEY_TYPE_RSA_PUBLIC_KEY ||
+                slot->type == PSA_KEY_TYPE_RSA_KEYPAIR )
+            {
+                pk.pk_info = &mbedtls_rsa_info;
+                pk.pk_ctx = slot->data.rsa;
+            }
+            else
+            {
+                pk.pk_info = &mbedtls_eckey_info;
+                pk.pk_ctx = slot->data.ecp;
+            }
+
+            if( ( ! export_public_key ) && PSA_KEY_TYPE_IS_KEYPAIR( slot->type ) )
+                ret = mbedtls_pk_write_key_der( &pk, data, data_size );
+            else
+                ret = mbedtls_pk_write_pubkey_der( &pk, data, data_size );
+            if ( ret < 0 )
+                return( mbedtls_to_psa_error( ret ) );
+            *data_length = ret;
+            return( PSA_SUCCESS );
         }
         else
-        {
-            pk.pk_info = &mbedtls_eckey_info;
-            pk.pk_ctx = slot->data.ecp;
-        }
-        if( PSA_KEY_TYPE_IS_KEYPAIR( slot->type ) )
-            ret = mbedtls_pk_write_key_der( &pk, data, data_size );
-        else
-            ret = mbedtls_pk_write_pubkey_der( &pk, data, data_size );
-        if( ret < 0 )
-            return( mbedtls_to_psa_error( ret ) );
-        *data_length = ret;
-        return( PSA_SUCCESS );
-    }
-    else
 #endif /* defined(MBEDTLS_PK_WRITE_C) */
-    {
-        /* This shouldn't happen in the reference implementation, but
-           it is valid for a special-purpose implementation to omit
-           support for exporting certain key types. */
-        return( PSA_ERROR_NOT_SUPPORTED );
-    }
+        {
+            /* This shouldn't happen in the reference implementation, but
+            it is valid for a special-purpose implementation to omit
+            support for exporting certain key types. */
+            return( PSA_ERROR_NOT_SUPPORTED );
+        }
+}
+
+psa_status_t psa_export_key(psa_key_slot_t key,
+                            uint8_t *data,
+                            size_t data_size,
+                            size_t *data_length)
+{
+    return psa_internal_export_key( key, data, data_size,
+                                  data_length, 0 );
 }
 
 
@@ -526,50 +541,10 @@
                                    size_t data_size,
                                    size_t *data_length)
 {
-    key_slot_t *slot;
-
-    if( key == 0 || key > MBEDTLS_PSA_KEY_SLOT_COUNT )
-        return( PSA_ERROR_EMPTY_SLOT );
-    slot = &global_data.key_slots[key];        
-    if( slot->type == PSA_KEY_TYPE_NONE )
-        return( PSA_ERROR_EMPTY_SLOT );   
-
-    if( !( PSA_KEY_TYPE_IS_PUBLIC_KEY( slot->type ) || PSA_KEY_TYPE_IS_KEYPAIR(slot->type) )  )
-        return( PSA_ERROR_INVALID_ARGUMENT );   
-    
-#if defined(MBEDTLS_PK_WRITE_C)
-    if( slot->type == PSA_KEY_TYPE_RSA_PUBLIC_KEY ||
-        slot->type == PSA_KEY_TYPE_RSA_KEYPAIR ||
-        PSA_KEY_TYPE_IS_ECC( slot->type ) )
-    {
-        mbedtls_pk_context pk;
-        int ret;
-        mbedtls_pk_init( &pk );
-        if( slot->type == PSA_KEY_TYPE_RSA_PUBLIC_KEY ||
-            slot->type == PSA_KEY_TYPE_RSA_KEYPAIR )
-        {
-            pk.pk_info = &mbedtls_rsa_info;
-            pk.pk_ctx = slot->data.rsa;
-        }
-        else
-        {
-            pk.pk_info = &mbedtls_eckey_info;
-            pk.pk_ctx = slot->data.ecp;
-        }
-        ret = mbedtls_pk_write_pubkey_der( &pk, data, data_size );
-        if( ret < 0 )
-            return( mbedtls_to_psa_error( ret ) );
-        *data_length = ret;
-        return( PSA_SUCCESS );
-    }
-#endif /* defined(MBEDTLS_PK_WRITE_C) */
-    /* This shouldn't happen in the reference implementation, but
-        it is valid for a special-purpose implementation to omit
-        support for exporting certain key types. */
-    return( PSA_ERROR_NOT_SUPPORTED );
+    return psa_internal_export_key( key, data, data_size,
+                                   data_length, 1 );
 }
 
-
 /****************************************************************/
 /* Message digests */
 /****************************************************************/