# kbuffer_timestamp

## NAME



           kbuffer_timestamp, kbuffer_subbuf_timestamp - Functions that read
           various data of a kbuffer descriptor
    


## SYNOPSIS



           **#include <kbuffer.h>**
    
           unsigned long long **kbuffer_timestamp**(struct kbuffer *_kbuf_);
           unsigned long long **kbuffer_subbuf_timestamp**(struct kbuffer *_kbuf_ , void *_subbuf_);
    


## DESCRIPTION



           The function **kbuffer_timestamp()** returns the timestamp of the
           current event of _kbuf_.
    
           The function **kbuffer_subbuf_timestamp()** returns the timestamp for
           the sub-buffer that was loaded in _kbuf_. This usually is (but not
           guaranteed to be) the timestamp of the first event on the
           sub-buffer.
    
           The function **kbuffer_start_of_data()** returns the offset of where
           the delta
    


## RETURN VALUE



           **kbuffer_read_event()** returns the event that the _kbuf_ descriptor is
           currently at, or NULL if the last event was passed (by
           **kbuffer_next_event()**).
    
           **kbuffer_next_event()** returns the next event after the current
           event or NULL if there are no more events.
    
           **kbuffer_read_at_offset()** returns the event at a given _offset_ from
           the start of the sub-buffer stored in _kbuf_ , or NULL if there
           exists no event. Note, _offset_ only needs to be an offset that
           lands on the record, or is at the start of it. It does not need to
           be exactly at the beginning of the record.
    
           **kbuffer_missed_events()** returns 0 if there were no missed events
           before loaded sub-buffer. Returns -1 if there were an unknown
           number of missed events, or if the number of missed events is
           known, that number will be returned.
    
           **kbuffer_event_size()** returns the size of the data payload of the
           current event of _kbuf_.
    
           **kbuffer_curr_size()** returns the size of the entire record of the
           current event of _kbuf_. This includes the size of the meta data for
           that record.
    
           **kbuf_curr_offset()** returns the offset of the current record from
           the beginning of the _kbuf_ sub-buffer.
    
           **kbuf_curr_index()** returns the index of the current record from the
           beginning of the _kbuf_ data section.
    


## EXAMPLE



               #include <stdio.h>
               #include <stdlib.h>
               #include <fcntl.h>
               #include <unistd.h>
               #include <sys/stat.h>
    
               #include <kbuffer.h>
    
               int main (int argc, char **argv)
               {
                       unsigned long long ts;
                       struct kbuffer *kbuf;
                       struct stat st;
                       char *buf;
                       void *event;
                       int save_offset = -1;
                       int record_size;
                       int offset;
                       int index;
                       int size;
                       int ret;
                       int fd;
                       int i = 0;
    
                       if (argc < 2) {
                               printf("usage: %s raw-subbuffer-page\n", argv[0]);
                               printf(" Try: dd count=1 bs=4096 if=/sys/kernel/tracing/per_cpu/cpu0/trace_pipe_raw of=/tmp/file\n");
                               exit(0);
                       }
    
                       if (stat(argv[1], &st) < 0) {
                               perror("stat");
                               exit(-1);
                       }
    
                       buf = malloc(st.st_size);
                       if (!buf) {
                               perror("Allocating buffer");
                               exit(-1);
                       }
    
                       fd = open(argv[1], O_RDONLY);
                       if (fd < 0) {
                               perror(argv[1]);
                               exit(-1);
                       }
    
                       ret = read(fd, buf, st.st_size);
                       if (ret < 0) {
                               perror("Reading buffer");
                               exit(-1);
                       }
                       close(fd);
    
                       kbuf = kbuffer_alloc(KBUFFER_ENDIAN_SAME_AS_HOST,
                                            KBUFFER_LSIZE_SAME_AS_HOST);
                       if (!kbuf) {
                               perror("Creating kbuffer");
                               exit(-1);
                       }
                       ret = kbuffer_load_subbuffer(kbuf, buf);
                       if (ret < 0) {
                               perror("Loading sub bufer");
                               exit(-1);
                       }
    
                       if (kbuffer_subbuffer_size(kbuf) > st.st_size) {
                               fprintf(stderr, "kbuffer is bigger than raw size %d > %ld\n",
                                       kbuffer_subbuffer_size(kbuf), st.st_size);
                               exit(-1);
                       }
    
                       ret = kbuffer_missed_events(kbuf);
                       if (ret) {
                               if (ret > 0)
                                       printf("Missed %d events before this buffer\n", ret);
                               else
                                       printf("Missed unknown number of events before this buffer\n");
                       }
                       do {
                               event = kbuffer_read_event(kbuf, &ts);
                               if (event) {
                                       record_size = kbuffer_curr_size(kbuf);
                                       offset = kbuffer_curr_offset(kbuf);
                                       index = kbuffer_curr_index(kbuf);
                                       size = kbuffer_event_size(kbuf);
    
                                       if (i == 20)
                                               save_offset = offset;
                                       printf(" event %3d ts:%lld\trecord_size:%d size:%d\tindex:%d offset:%d\n",
                                              i++, ts, record_size, size, index, offset);
                                       event = kbuffer_next_event(kbuf, NULL);
                               }
                       } while (event);
    
                       if (!event)
                               printf("Finished sub buffer\n");
    
                       if (save_offset > 0) {
                               event = kbuffer_read_at_offset(kbuf, save_offset, &ts);
                               if (!event) {
                                       fprintf(stderr, "Funny, can't find event 20 at offset %d\n", save_offset);
                                       exit(-1);
                               }
                               record_size = kbuffer_curr_size(kbuf);
                               offset = kbuffer_curr_offset(kbuf);
                               index = kbuffer_curr_index(kbuf);
                               size = kbuffer_event_size(kbuf);
    
                               printf("\n saved event 20 ts:%lld\trecord_size:%d size:%d\tindex:%d offset:%d\n\n",
                                      ts, record_size, size, index, offset);
                       }
                       kbuffer_free(kbuf);
    
                       return 0;
               }
    


## FILES



               **event-parse.h**
                       Header file to include in order to have access to the library APIs.
               **-ltraceevent**
                       Linker switch to add when building a program that uses the library.
    


## LICENSE



           libtraceevent is Free Software licensed under the GNU LGPL 2.1
    


## RESOURCES



           **https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/ **
    


## NOTES



            1. rostedt@goodmis.org
               mailto:rostedt@goodmis.org
    
            2. linux-trace-devel@vger.kernel.org
               mailto:linux-trace-devel@vger.kernel.org
    


* * *