add documentation for SAS functions

include/olm/sas.h

@@ -25,51 +25,112 @@ extern "C" {
 
 typedef struct OlmSAS OlmSAS;
 
+/** A null terminated string describing the most recent error to happen to an
+ * SAS object. */
 const char * olm_sas_last_error(
     OlmSAS * sas
 );
 
+/** The size of an SAS object in bytes. */
 size_t olm_sas_size(void);
 
+/** Initialize an SAS object using the supplied memory.
+ * The supplied memory must be at least `olm_sas_size()` bytes. */
 OlmSAS * olm_sas(
     void * memory
 );
 
+/** Clears the memory used to back an SAS object. */
 size_t olm_clear_sas(
     OlmSAS * sas
 );
 
+/** The number of random bytes needed to create an SAS object. */
 size_t olm_create_sas_random_length(
     OlmSAS * sas
 );
 
+/** Creates a new SAS object.
+ *
+ * @param[in] sas the SAS object to create, initialized by `olm_sas()`.
+ * @param[in] random array of random bytes.
+ * @param[in] random_length the number of random bytes provided.  Must be at
+ *    least `olm_create_sas_random_length()`.
+ *
+ * @return `olm_error()` on failure.  If there weren't enough random bytes then
+ * `olm_sas_last_error()` will be `NOT_ENOUGH_RANDOM`.
+ */
 size_t olm_create_sas(
     OlmSAS * sas,
     void * random, size_t random_length
 );
 
+/** The size of a public key in bytes. */
 size_t olm_sas_pubkey_length(OlmSAS * sas);
 
+/** Get the public key for the SAS object.
+ *
+ * @param[in] sas the SAS object.
+ * @param[out] pubkey buffer to store the public key.
+ * @param[in] pubkey_length the size of the `pubkey` buffer.  Must be at least
+ *   `olm_sas_pubkey_length()`.
+ *
+ * @return `olm_error()` on failure.  If the `pubkey` buffer is too small, then
+ * `olm_sas_last_error()` will be `OUTPUT_BUFFER_TOO_SMALL`.
+ */
 size_t olm_sas_get_pubkey(
     OlmSAS * sas,
     void * pubkey, size_t pubkey_length
 );
 
+/** Sets the public key of other user.
+ *
+ * @param[in] sas the SAS object.
+ * @param[in] their_key the other user's public key.
+ * @param[in] their_key_size the size of the `their_key` buffer.
+ *
+ * @return `olm_error()` on failure.  If the `their_key` buffer is too small,
+ * then `olm_sas_last_error()` will be `INPUT_BUFFER_TOO_SMALL`.
+ */
 size_t olm_sas_set_their_key(
     OlmSAS *sas,
     void * their_key, size_t their_key_length
 );
 
+/** Generate bytes to use for the short authentication string.
+ *
+ * @param[in] sas the SAS object.
+ * @param[in] info extra information to mix in when generating the bytes.
+ * @param[in] info_length the length of the `info` parameter.
+ * @param[out] output the output buffer.
+ * @param[in] output_length the size of the output buffer.
+ */
 size_t olm_sas_generate_bytes(
     OlmSAS * sas,
     const void * info, size_t info_length,
     void * output, size_t output_length
 );
 
+/** The size of the message authentication code generated by
+ * olm_sas_calculate_mac()`. */
 size_t olm_sas_mac_length(
     OlmSAS *sas
 );
 
+/** Generate a message authentication code (MAC) based on the shared secret.
+ *
+ * @param[in] sas the SAS object.
+ * @param[in] input the message to produce the authentication code for.
+ * @param[in] input_length the length of the message.
+ * @param[in] info extra information to mix in when generating the MAC.
+ * @param[in] info_length the length of the `info` parameter.
+ * @param[out] mac the buffer in which to store the MAC.
+ * @param[in] mac_length the size of the `mac` buffer.  Must be at least
+ * `olm_sas_mac_length()`
+ *
+ * @return `olm_error()` on failure.  If the `mac` buffer is too small, then
+ * `olm_sas_last_error()` will be `OUTPUT_BUFFER_TOO_SMALL`.
+ */
 size_t olm_sas_calculate_mac(
     OlmSAS * sas,
     void * input, size_t input_length,