SYNOPSIS

#include "bss.h"
typedef int (*RTBHandler)(time_t time, unsigned long count, char *buffer, int bufLength);
[see description for available functions]

DESCRIPTION

The BSS library supports the streaming of data over delay-tolerant networking (DTN) bundles. The intent of the library is to enable applications that pass streaming data received in transmission time order (i.e., without time regressions) to an application-specific ``display'' function --- notionally for immediate real-time display --- but to store all received data (including out-of-order data) in a private database for playback under user control. The reception and real-time display of in-order data is performed by a background thread, leaving the application's main (foreground) thread free to respond to user commands controlling playback or other application-specific functions.

The application-specific ``display'' function invoked by the background thread must conform to the RTBHandler type definition. It must return 0 on success, -1 on any error that should terminate the background thread. Only on return from this function will the background thread proceed to acquire the next BSS payload.

All data acquired by the BSS background thread is written to a BSS database comprising three files: table, list, and data. The name of the database is the root name that is common to the three files, e.g., db3.tbl, db3.lst, db3.dat would be the three files making up the db3 BSS database. All three files of the selected BSS database must reside in the same directory of the file system.

Several replay navigation functions in the BSS library require that the application provide a navigation state structure of type bssNav as defined in the bss.h header file. The application is not reponsible for populating this structure; it's strictly for the private use of the BSS library.

int bssOpen(char *bssName, char *path, char *eid)

Opens access to a BSS database, to enable data playback. bssName identifies the specific BSS database that is to be opened. path identifies the directory in which the database resides. eid is ignored. On any failure, returns -1. On success, returns zero.

int bssStart(char *bssName, char *path, char *eid, char *buffer, int bufLen, RTBHandler handler)

Starts a BSS data acquisition background thread. bssName identifies the BSS database into which data will be acquired. path identifies the directory in which that database resides. eid is used to open the BP endpoint at which the delivered BSS bundle payload contents will be acquired. buffer identifies a data acquisition buffer, which must be provided by the application, and bufLen indicates the length of that buffer; received bundle payloads in excess of this length will be discarded.

handler identifies the display function to which each in-order bundle payload will be passed. The time and count parameters passed to this function identify the received bundle, indicating the bundle's creation timestamp time (in seconds) and counter value. The buffer and bufLength parameters indicate the location into which the bundle's payload was acquired and the length of the acquired payload. handler must return -1 on any unrecoverable system error, 0 otherwise. A return value of -1 from handler will terminate the BSS data acquisition background thread.

On any failure, returns -1. On success, returns zero.

int bssRun(char *bssName, char *path, char *eid, char *buffer, int bufLen, RTBHandler handler)

A convenience function that performs both bssOpen() and bssStart(). On any failure, returns -1. On success, returns zero.

void bssClose()

Terminates data playback access to the most recently opened BSS database.

void bssStop()

Terminates the most recently initiated BSS data acquisition background thread.

void bssExit()

A convenience function that performs both bssClose() and bssStop().

long bssRead(bssNav nav, char *data, int dataLen)

Copies the data at the current playback position in the database, as indicated by nav, into data; if the length of the data is in excess of dataLen then an error condition is asserted (i.e., -1 is returned). Note that bssRead() cannot be successfully called until nav has been populated, nominally by a preceding call to bssSeek(), bssNext(), or bssPrev(). Returns the length of data read, or -1 on any error.

long bssSeek(bssNav *nav, time_t time, time_t *curTime, unsigned long *count)

Sets the current playback position in the database, in nav, to the data received in the bundle with the earliest creation time that was greater than or equal to time. Populates nav and also returns the creation time and bundle ID count of that bundle in curTime and count. Returns the length of data at this location, or -1 on any error.

long bssSeek_read(bssNav *nav, time_t time, time_t *curTime, unsigned long *count, char *data, int dataLen)

A convenience function that performs bssSeek() followed by an immediate bssRead() to return the data at the new playback position. Returns the length of data read, or -1 on any error.

long bssNext(bssNav *nav, time_t *curTime, unsigned long *count)

Sets the playback position in the database, in nav, to the data received in the bundle with the earliest creation time and ID count greater than that of the bundle at the current playback position. Populates nav and also returns the creation time and bundle ID count of that bundle in curTime and count. Returns the length of data at this location (if any), -2 on reaching end of list, or -1 on any error.

long bssNext_read(bssNav *nav, time_t *curTime, unsigned long *count, char *data, int dataLen)

A convenience function that performs bssNext() followed by an immediate bssRead() to return the data at the new playback position. Returns the length of data read, -2 on reaching end of list, or -1 on any error.

long bssPrev(bssNav *nav, time_t *curTime, unsigned long *count)

Sets the playback position in the database, in nav, to the data received in the bundle with the latest creation time and ID count earlier than that of the bundle at the current playback position. Populates nav and also returns the creation time and bundle ID count of that bundle in curTime and count. Returns the length of data at this location (if any), -2 on reaching end of list, or -1 on any error.

long bssPrev_read(bssNav *nav, time_t *curTime, unsigned long *count, char *data, int dataLen)

A convenience function that performs bssPrev() followed by an immediate bssRead() to return the data at the new playback position. Returns the length of data read, -2 on reaching end of list, or -1 on any error.