stasis-aries-wal/src/stasis/logger/logHandle.c

/*---
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FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
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POSSIBILITY OF SUCH DAMAGE.

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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND
NON-INFRINGEMENT. THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, AND
THE AUTHORS AND DISTRIBUTORS HAVE NO OBLIGATION TO PROVIDE
MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

GOVERNMENT USE: If you are acquiring this software on behalf of the
U.S. government, the Government shall have only "Restricted Rights" in
the software and related documentation as defined in the Federal
Acquisition Regulations (FARs) in Clause 52.227.19 (c) (2). If you are
acquiring the software on behalf of the Department of Defense, the
software shall be classified as "Commercial Computer Software" and the
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---*/

#include <config.h> 

#include <stdlib.h>

#include "logHandle.h"

/**
   Sets the next and prev field of h, but does not set h.file_offset.
   That should probably be set before calling this function.
*/

static void set_offsets(LogHandle * h, const LogEntry * e);

/*-------------------------------------------------------*/

LogHandle getLogHandle() {

  lsn_t lsn = LogTruncationPoint();

  return getGuardedHandle(lsn, NULL, NULL);
}

LogHandle getLSNHandle(lsn_t lsn) {
  return getGuardedHandle(lsn, NULL, NULL);
}

LogHandle getGuardedHandle(lsn_t lsn, guard_fcn_t * guard, void * guard_state) {
  LogHandle ret;
  ret.next_offset = lsn;
  ret.prev_offset = lsn;
  ret.guard = guard;
  ret.guard_state = guard_state;
  return ret;
}

const LogEntry * nextInLog(LogHandle * h) {
  const LogEntry * ret = LogReadLSN(h->next_offset);
  if(ret != NULL) {
    set_offsets(h, ret);
  }

  if(h->guard) {
    if(!(h->guard(ret, h->guard_state))) {
      FreeLogEntry(ret);
      ret = NULL;
    }
  }


  return ret;
}

const LogEntry * previousInTransaction(LogHandle * h) {
  const LogEntry * ret = NULL;
  if(h->prev_offset > 0) {
    ret = LogReadLSN(h->prev_offset);
    set_offsets(h, ret);

    if(h->guard) {
      if(!h->guard(ret, h->guard_state)) {
	FreeLogEntry(ret);
	ret = NULL;
      }
    }
  }

  return ret;

}

static void set_offsets(LogHandle * h, const LogEntry * e) {
  h->next_offset = LogNextEntry(e);
  h->prev_offset = e->prevLSN;
}