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What are plugins?

Creating plugins

I have created a library of useful functions for writing J-Pilot conduits.  The code is inside j-pilot and the header file is libplugin.h.  The naming convention is that all of these functions start with "jp_".  There are some I threw in there and didn't add a jp_ prefix because I would have had to change too much existing code. 

If you do create a plugin I would appreciate it if you would give me a link to the site so that I can put it on my website.  This will encourage more people to use J-Pilot and your plugin.  Even if you are working on a plugin you can let me know and I will put it down as in progress so that someone doesn't duplicate your effort.  Its GNU licensed code so you are free to do not tell me of course, as long as you follow the GNU license. My email is Judd Montgomery <judd@engineer.com>.  The official J-Pilot website is at http://jpilot.org.

Example Plugins

Plugin call back functions

int plugin_search(char *search_string, int case_sense, struct search_result **sr);

struct search_result
{
   char *line;
   unsigned int unique_id;
   struct search_result *next;
};

char *search_string - input parameter, a string that the user is searching on.
int case_sense - input parameter, will be TRUE if a case sensitive match is required.
struct search_result **sr - output parameter, a null terminated linked list of search matches to be returned to jpilot.

struct search_result
{
char *line - This is the search result text as you want it to appear in the search result window.
unsigned int unique_id - This is the unique_id of the record that the search match appeared in.  This number will be passed back to plugin_gui if the record is selected in the search window.
struct search_result *next - A pointer to the next node in the linked list.
};

This function will be called from the search window of the main program.  The output parameter search_result will be displayed in the search window.

int plugin_get_name(char *name, int len);

char *name - output parameter, a pointer to a pre-allocated buffer in j-pilots address space.  The plugin should copy its name into this string.
int len - input parameter, the length of this buffer.  Don't overwrite this buffer.  Its currently 50 characters.

This function is used to get the name of the plugin, e.g. "Expense 1.0".  This function must be implemented or the plugin won't be loaded..

int plugin_get_menu_name(char *name, int len);

char *name - output parameter, a pointer to a pre-allocated buffer in j-pilots address space.  The plugin should copy its name into this string.
int len - input parameter, the length of this buffer.  Don't overwrite this buffer.  Its currently 50 characters.

This function is used to get the name of the plugin, e.g. "Expense".  This is the name that will appear in the j-pilot menu under plugins.  It is possible to have a plugin that isn't accessible under the menu, in that case this function should not be implemented.

int plugin_get_help_name(char *name, int len);

char *name - output parameter, a pointer to a pre-allocated buffer in j-pilots address space.  The plugin should copy its name into this string.
int len - input parameter, the length of this buffer.  Don't overwrite this buffer.  Its currently 50 characters.

This function is used to get the name of the plugin as it wishes to appear in the help menu pulldown, e.g. "About Expense".  This function is not mandatory.

int plugin_help(char **text, int *width, int *height);

char **text - output parameter, the plugin should point this string pointer to a string to be displayed in the help box. 
int *width - output parameter, the width of the help window.
int *height - output parameter, the height of the help window.

int plugin_get_db_name(char *name, int len);

char *name - output parameter, a pointer to a pre-allocated buffer in j-pilots address space.
int len - input parameter, the length of this buffer.  Please don't overwrite this buffer.  Its currently 50 characters.

This function is used to get the name of the palm database (pdb file) that is to be synced.  This DB will be automatically synced when j-pilot performs a sync.

For example the expense plugin uses the DB file "ExpenseDB.pdb", it would copy "ExpenseDB" to name, leaving off the extension.  A normal plugin that just adds, deletes, and changes DB records using the plugin API will not have to do any special work during a sync process, it will be automatic.

int plugin_startup(jp_startup_info *info);

typedef struct
{
   char *base_dir;
} jp_startup_info;

This plugin function is called when j-pilot starts up.  Any initialization needed should be done here.
The base_dir is the directory where j-pilot was compiled to be installed (default is "/usr/local").  More fields may be added to this structure later as needed without changing the API.

int plugin_gui(GtkWidget *vbox, GtkWidget *hbox, unsigned int unique_id);

GtkWidget *vbox - input parameter, the box underneath the sync and quit buttons.  This is where the main applications put the delete button.
GtkWidget *hbox - input parameter, the box that makes up the main part of the screen.
unsigned int unique_id - input parameter, a record id that the application should go to.  It is used by the search window.  This will be a non-null when this function is called from the search screen, null otherwise.

This plugin function is called when the plugin is selected from the j-pilot menu, or from the search window.  This is where the plugin can draw on the screen and provide the GUI interface, etc.  If unique_id is non-null then the application should go directly to that record.  This is how the search window forces the applications to go to the search result records.

char **text - output parameter, the text to be displayed on the about dialog window.
int *width - output parameter, the width of the dialog window.
int *height - output parameter, the height of the dialog window.

This plugin function is called when the plugin is selected from the j-pilot help menu pulldown.  2 things can be done here.
1. allocate memory for a text string to pass back to jpilot and it will be displayed in a dialog window with width and height as the width and height of the window.
2.  set *text=NULL to prevent jpilot from putting up a dialog window and then implement the help portion yourself.
3.  I guess you could do both 1 and 2.

This plugin function is called when another application has been called and the boxes for the plugin GUI screen are about to be destroyed.  Most widgets will be destroyed when their parents are destroyed, so this function normally is not needed.

int plugin_pre_sync(void);

This function is called after the j-pilot sync button is pressed and before the sync with the pilot is started.

int plugin_sync(int sd);
int sd - input parameter, the handle to the pilot sync connection.

This function is called after the sync button is pressed and during the sync process.
Unless something special is needed to be done with the sync handle this function does not need to be used.
The sync process in j-pilot is a forked process, and this function will be called from the forked process.  Therefore the previous state of global data in the plugin will not be available when this function is called.
The order of operations during a sync is as follows:
1. The 4 main applications are synced.
2. Plugins are synced according to the DB name passed back from plugin_get_db_name().
3. This function is called.
4. Modified pdb files are pulled back from the pilot to the desktop if a backup operation is being performed. 

int plugin_post_sync(void);

This function is called after the sync process is completed.  Screen redraws may be a good thing to do here, as categories and records may have changed during the sync.

int plugin_exit_cleanup(void);

This function is called when j-pilot is shutting down.

int plugin_print(?,?);

There will be a print API here, but printing has not been implemented yet.

Plugin API functions

int jp_init(void);

int jp_logf(int level, char *format, ...);

example:
plugin_logf(LOG_WARN, "error number %d: %s\n", n, err);

There are 3 places for logging output to go to.  Standard output (stdout, usually the terminal window), the log file in ~/.jpilot/, and the ouput window (the one that pops up while you are syncing).

Logging levels are bitmasks, so they may be combined with a logical OR.

You can run J-Pilot in debug mode by executing "jpilot -d" to force debug output.
 

Logging Levels

level	stdout	log file	GUI	Intended use
LOG_DEBUG	Debug only	Debug only		Goes to stdout These messages will not normally show up unless jpilot is in debug mode.  These message should be things like "x=%d", or "inside while loop", etc.
LOG_INFO	X	X	X	Informational messages that aren't serious.  e.g. "Put the palm in the cradle now", "Syncing xxx plugin", etc.
LOG_WARN	X	X	X	Warning messages, that are not fatal, but may affect execution.  e.g. "Out of Memory", "Could not open file".
LOG_FATAL	X	X	X	Fatal messages in which execution can not continue.  e.g. "could not open display".  "Out of Memory" may also belong here.
				*I didn't intend for the following levels to be used unless they are needed.  They provide more precise control over the logging output, but also override any future configurability.
LOG_STDOUT	X			Using this will force a message to be displayed on stdout.*
LOG_FILE		X		Using this will force a message to be written to the log file.*
LOG_GUI			X	Using this will force a message to be displayed in the output window.*

int jp_install_append_line(char *line);

char *line - input parameter, this is just a line to write to the install file.

The install file is a file that is read line by line during the sync process.  Each line is the full path to a file name to be installed.  Once the file is installed on the pilot successfully then that line is removed from the file.
example: "/home/base/AddressDB.pdb" will install this AddressDB to the pilot.

int jp_install_remove_line(int deleted_line);

int deleted_line - input parameter, This is the line number to be deleted from the install file.  The first line is line zero.

const char *jp_strstr(const char *haystack, const char *needle, int case_sense);

This function is analogous to the C function strstr except that it has a case sensitive parameter.

int jp_get_app_info(char *DB_name, void **buf, int buf_size);

char *DB_name - input parameter, the name of the DB file to be read.  For example to read the Expense data you would pass "ExpenseDB", leaving off the .pdb extension.
void **buf - output parameter, a pointer to a pointer to a memory area to be allocated for the application info to be copied into.  Memory is allocated and must be freed by the calling function.
int buf_size - output parameter, the size of the memory block that is allocated during this call.

This function retrieves the application info from a PDB file.  It is packed and must be unpacked into a format that is specific to each palm application.

int jp_open_home_file(char *filename, char *mode);

char *filename - input parameter, the name of the file to be opened. 

char *mode - input parameter, mode to open file in. See man page for fopen. 

This function opens a file in $JPILOT_HOME/.jpilot/ Its analogous to fopen except that it looks in the jpilot directory for the file.

Using J-Pilot database files

Records are just chunks of data.  They must be packed and unpacked into some meaningful form by the desktop application.  To do this it is neccessary to know the record format of the palm application.  The palm processor is Motorola 68000 based and the palm stores integers native to its own processor, so some translations need to be made on integer data.  There are examples of this in the pilot-link library code.

To modify a record you must write the new record to the pc file and then delete the original record.  Actually if its a record in the pdb file it won't actually get deleted.  A "deleted record" with the same unique_id will have to be written to the pc file.  You don't really have to worry about the details of doing this since there is a library to do it for you.

So, when you read a database using the libplugin calls you will get records back with different record types depending on where they came from and what they are scheduled to do at sync time.

This is a short explanation of each record type:

PALM_REC:  This record was read from the palm pdb file.  It is unchanged by j-pilot.

MODIFIED_PALM_REC:  This record has been modified by j-pilot.  What this means is that this record has been deleted and a new record has been created to reflect the changes.  This is the original record that still exists in the pdb file and it will be deleted at sync time.  This record is kept so that at sync time it can be compared with the palm pilots record to see if it was modified on the pilot and in j-pilot.  This record shouldn't be shown to the user.

DELETED_PALM_REC:  This record has been scheduled to be deleted from the pdb file at sync time.  This is the record retrieved from the pdb file and there is another record in the pc file with a matching unique_id to mark this record as deleted.  This record should not be shown to the user.

NEW_PC_REC:  This is a new record that has been added by j-pilot.  It is in the pc file and will be written to the palm during the next sync and then retrieved back from the palm into the pdb file.

DELETED_PC_REC:  This record was created in the pc file and then later deleted.  It shouldn't be shown to the user.

DELETED_DELETED_PALM_REC:  This record should only exist during a sync process.  During the sync when a DELETED_PALM_REC gets deleted from the pilot it will be marked with this record type and then as soon as the sync is finished the pc file will get cleaned up and it should be removed.  If a crash occurs it could be possible for this record to be in the pc file.

The SPENT_PC_RECORD_BIT means that this record will be removed during the next pc file cleanup.  If this bit is set then the record can be totally ignored.
 

typedef enum {
   PALM_REC = 100L,
   MODIFIED_PALM_REC = 101L,
   DELETED_PALM_REC = 102L,
   NEW_PC_REC = 103L,
   DELETED_PC_REC =  SPENT_PC_RECORD_BIT + 104L,
   DELETED_DELETED_PALM_REC =  SPENT_PC_RECORD_BIT + 105L
} PCRecType;

int jp_read_DB_files(char *DB_name, GList **records);

char *DB_name is a pointer to the name of the DB file to be read.  For example to read the Expense data you would pass "ExpenseDB", leaving off the .pdb extension.    Both the pdb and the pc files are read.
GList **records is a pointer to a pointer to a list of records to be read from the database files.  Memory is allocated and should be freed by calling jp_free_DB_records().

This function will read the pdb file and the pc file out of the $(HOME)/.jpilot/ directory and put all the records into a list.  The list contains structures of the following:

typedef struct
{
   PCRecType rt;
   unsigned int unique_id;
   unsigned char attrib;
   void *buf;
   int size;
} jp_buf_rec;

PCRecType rt - This has been explained in the previous paragraph.
unsigned int unique_id - This is the unique_id of a record.  The palm assigns these when they are created.  The PC records will have their own set of unique ids.
unsigned char attrib - This is the attributes of the record.  Look at the pilot-link code to understand these.
void *buf - This is the raw record as read from the DB.
int size - This is the size of the raw record.

int jp_free_DB_records(GList **records);

GList **records is a pointer to pointer to a list of records to be freed.
This function will free the records list and set the pointer to NULL on completion.

This call should be used to free the record list allocated by jp_read_DB_files().

int jp_delete_record(char *DB_name, buf_rec *br, int flag);

char *DB_name is the DB name to be witten to.  For example to write to the Expense application database you would pass "ExpenseDB".  Do not pass the file extension (".pdb").
buf_rec *br is a pointer to a record to be deleted.
int flag can be either DELETE_FLAG or MODIFY_FLAG.  DELETE_FLAG should be used if the record is being deleted.  MODIFY_FLAG should be used if the record is being modified.

char *DB_name is the DB name to be witten to.  For example to write to the Expense application database you would pass "ExpenseDB".  Do not pass the file extension (".pdb").
buf_rec *br is a pointer to a record to be written to the DB file.

typedef struct
{
   PCRecType rt;
   unsigned int unique_id;
   unsigned char attrib;
   void *buf;
   int size;
} jp_buf_rec;

This function is used for writing a record to the pc database file.  The record type should almost always be NEW_PC_REC.  Unique_id can be left blank since it is an outgoing parameter.  A new unique id will be assigned and placed in the structure.  Attrib is the record attributes, buf is a raw database record, and size is the size of the record.
 

Other Miscellaneous API Functions

int unlink_file(char *filename);

char *filename is the filename to remove. 

This function is like unlink except that it looks for the file in the jpilot directory. 

int rename_file(char *old_filename, char *new_filename);

char *old_filename is the filename to rename. 

char *new_filename is the filename to rename to. 

This function is like rename except that it looks for the files in the jpilot directory. 

int get_app_info_size(FILE *in, int *size);

FILE *in input parameter, an open file pointer to a palm pdb file. 

int *size output parameter, is the size of the application info block. 

int read_header(FILE *pc_in, PC3RecordHeader *header);

FILE *pc_in input parameter, an open file pointer to a J-Pilot pc3 file pdb file. 

PC3RecordHeader *header output parameter, the header from the file read in. 

int write_header(FILE *pc_out, PC3RecordHeader *header);

FILE *pc_out input parameter, an open file pointer to a J-Pilot pc3 file pdb file. 

PC3RecordHeader *header input parameter, the header to be written to the file.