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/* Copyright 2016 OpenMarket Ltd
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* functions for encoding and decoding messages in the Olm protocol.
*
* Some of these functions have only C++ bindings, and are declared in
* message.hh; in time, they should probably be converted to plain C and
* declared here.
*/
#ifndef OLM_MESSAGE_H_
#define OLM_MESSAGE_H_
#include <stdint.h>
#include <stddef.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* The length of the buffer needed to hold a group message.
*/
size_t _olm_encode_group_message_length(
size_t group_session_id_length,
uint32_t chain_index,
size_t ciphertext_length,
size_t mac_length
);
/**
* Writes the message headers into the output buffer.
*
* version: version number of the olm protocol
* session_id: group session identifier
* session_id_length: length of session_id
* message_index: message index
* ciphertext_length: length of the ciphertext
* output: where to write the output. Should be at least
* olm_encode_group_message_length() bytes long.
* ciphertext_ptr: returns the address that the ciphertext
* should be written to, followed by the MAC.
*
* Returns the size of the message, up to the MAC.
*/
size_t _olm_encode_group_message(
uint8_t version,
const uint8_t *session_id,
size_t session_id_length,
uint32_t message_index,
size_t ciphertext_length,
uint8_t *output,
uint8_t **ciphertext_ptr
);
struct _OlmDecodeGroupMessageResults {
uint8_t version;
const uint8_t *session_id;
size_t session_id_length;
uint32_t message_index;
int has_message_index;
const uint8_t *ciphertext;
size_t ciphertext_length;
};
/**
* Reads the message headers from the input buffer.
*/
void _olm_decode_group_message(
const uint8_t *input, size_t input_length,
size_t mac_length,
/* output structure: updated with results */
struct _OlmDecodeGroupMessageResults *results
);
#ifdef __cplusplus
} // extern "C"
#endif
#endif /* OLM_MESSAGE_H_ */
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