.\" Automatically generated by Pandoc 2.9.2.1
.\"
.TH "" "" "2023-05-31" "PMDK - " "PMDK Programmer's Manual"
.hy
.\" SPDX-License-Identifier: BSD-3-Clause
.\" Copyright 2017-2023, Intel Corporation
.SH NAME
.PP
\f[B]pmemlog_tell\f[R]()(DEPRECATED),
\f[B]pmemlog_rewind\f[R]()(DEPRECATED),
\f[B]pmemlog_walk\f[R]()(DEPRECATED) - checks current write point for
the log or walks through the log
.SH SYNOPSIS
.IP
.nf
\f[C]
#include <libpmemlog.h>

long long pmemlog_tell(PMEMlogpool *plp);
void pmemlog_rewind(PMEMlogpool *plp);
void pmemlog_walk(PMEMlogpool *plp, size_t chunksize,
    int (*process_chunk)(const void *buf, size_t len, void *arg),
    void *arg);
\f[R]
.fi
.SH DESCRIPTION
.PP
The \f[B]pmemlog_tell\f[R]() function returns the current write point
for the log, expressed as a byte offset into the usable log space in the
memory pool.
This offset starts off as zero on a newly-created log, and is
incremented by each successful append operation.
This function can be used to determine how much data is currently in the
log.
.PP
The \f[B]pmemlog_rewind\f[R]() function resets the current write point
for the log to zero.
After this call, the next append adds to the beginning of the log.
.PP
The \f[B]pmemlog_walk\f[R]() function walks through the log
\f[I]plp\f[R], from beginning to end, calling the callback function
\f[I]process_chunk\f[R] for each \f[I]chunksize\f[R] block of data
found.
The argument \f[I]arg\f[R] is also passed to the callback to help avoid
the need for global state.
The \f[I]chunksize\f[R] argument is useful for logs with fixed-length
records and may be specified as 0 to cause a single call to the callback
with the entire log contents passed as the \f[I]buf\f[R] argument.
The \f[I]len\f[R] argument tells the \f[I]process_chunk\f[R] function
how much data \f[I]buf\f[R] is holding.
The callback function should return 1 if \f[B]pmemlog_walk\f[R]() should
continue walking through the log, or 0 to terminate the walk.
The callback function is called while holding \f[B]libpmemlog\f[R](7)
internal locks that make calls atomic, so the callback function must not
try to append to the log itself or deadlock will occur.
.SH RETURN VALUE
.PP
On success, \f[B]pmemlog_tell\f[R]() returns the current write point for
the log.
On error, it returns -1 and sets \f[I]errno\f[R] appropriately.
.PP
The \f[B]pmemlog_rewind\f[R]() and \f[B]pmemlog_walk\f[R]() functions
return no value.
.SH SEE ALSO
.PP
\f[B]libpmemlog\f[R](7) and \f[B]<https://pmem.io>\f[R]