Call History Plugin
Introduction: Callhistory is a plugin loaded by ofono for persisting voice call history information in a disk file. Plugin exports dbus methods and signals as org.ofono.callhistory interface. Whenever there is a voice call in the system, ofono calls the plugin with the infomation (lineid,calltype,start time, end time) , plugin writes the information into the file , increments the 'unread' field in the header and sends out dbus signal with the number of unread records. Client (dialer) requests history records by calling method "GetVoiceHistory" exposed on the callhistory interface. After receiving information client calls the "SetVoiceHistoryRead" as an acknowledgement to indicate end of transaction. The pointers in the header are adjusted appropriately (explained clearly below). Design : Plugin uses memory mapped file for high performance input/output operations. File is used as cyclic queue for storing or reading records, it store s 50 records of 78bytes,hence fixed size file of 3916 bytes is used. File's first 16 bytes were used for storing header, and next 3900 bytes for data. Header structure has head pointer, tail pointer,unread and lastid. Head pointer points to next slot for writing record into,tail for reading record, unread for number of history records unread by client, lastid for id of the last record that is written. Below is the file structure: (3916 bytes) |Header|Data| 0 16 Header Structure: (16 bytes) |head|tail|unread|lastid| 0 4 8 12 16 head : Points to next slot for writing tail : Points to next record to be read unread : Number of Unread records so far lastid : Number of the record that is last written Below is the structure of the history record: History Record:(78 bytes) |id|lineid|calltype|start time|end time| id : Record id lineid : phone Number calltype : Outgoing/Incoming/Missed start time: start time in UTC end time: end time in UTC When the plugin is loaded by the ofono, it opens or creates a disk file of 3916 bytes size and maps it into fixed size memory space. Plugin reads the header of the file , if the 'unread' records is > 0 , a signal is sent out on the dbus with the information of number of unread records. Requesting data by client: When the client calls "GetVoiceHistory" method,plugin uses temp_tail and temp_unread variables to accomplish sending data to client. It copies tail pointer stored in the header into temporary tail pointer ,starts to read history records one at a time from the location pointed by the temp tail pointer , copies the into dbus structure, increments the temp tail pointer by size of the history record (78 bytes) and reads data from the next record location , this is repeated until it reaches head pointer. when all the unread records are read then the dbus structure is sent to the client. Once the data received, client needs to "SetVoiceHistoryRead" method to indicate that it received the data. Plugin will update the tail pointer with the temp tail pointer and unread records number is decremented by temp_unread. Using temp_tail and temp_unread variables protect from modifying the header if there is any loss in data delivery. If client doesnt call 'SetVoiceHistoryRead' then the actua l header pointers wont be updated in the file. Writing record into the file: When Ofono calls the plugin with call information (phone number, call type, call start time , call end time), plugin increaments the lastid to create record id for this record ,writes the record in the location pointed by head, and the head pointer is incremented by size of record (78 bytes), "unread" variable is incremented by 1. If the head reaches end of file (3916) then it is reset it back to begining of the data portion of the file (16 bytes). A dbus signal is sent out with number of current unread records. Plugin keeps writing the records in circular queue. Locking: Accessing Memory mapped file pointer , all header fields (head,tail,unread,lastid), temp_unread,temp_tail are synchronized by a mutex. writing into memory file and reading from memory file happen asynchronously, so mutex is used to protect the memory mapped file pointer , header, temp_unread, temp_tail. Limitations: History is limited to storing 50 records. The above design assumes that there is only one client (either dialer or a history daemon) that reads data and sends acknowledgemnts. _______________________________________________ ofono mailing list [email protected] http://lists.ofono.org/listinfo/ofono
