.\" Automatically generated by Pandoc 2.10.1
.\"
.TH "PMEMBLK_READ" "3" "2020-10-28" "PMDK - pmemblk API version 1.1" "PMDK Programmer's Manual"
.hy
.\" SPDX-License-Identifier: BSD-3-Clause
.\" Copyright 2017-2018, Intel Corporation
.SH NAME
.PP
\f[B]pmemblk_read\f[R](), \f[B]pmemblk_write\f[R]() - read or write a
block from a block memory pool
.SH SYNOPSIS
.IP
.nf
\f[C]
#include <libpmemblk.h>

int pmemblk_read(PMEMblkpool *pbp, void *buf, long long blockno);
int pmemblk_write(PMEMblkpool *pbp, const void *buf, long long blockno);
\f[R]
.fi
.SH DESCRIPTION
.PP
The \f[B]pmemblk_read\f[R]() function reads the block with block number
\f[I]blockno\f[R] from memory pool \f[I]pbp\f[R] into the buffer
\f[I]buf\f[R].
Reading a block that has never been written by \f[B]pmemblk_write\f[R]()
will return a block of zeroes.
.PP
The \f[B]pmemblk_write\f[R]() function writes a block from \f[I]buf\f[R]
to block number \f[I]blockno\f[R] in the memory pool \f[I]pbp\f[R].
The write is atomic with respect to other reads and writes.
In addition, the write cannot be torn by program failure or system
crash; on recovery the block is guaranteed to contain either the old
data or the new data, never a mixture of both.
.SH RETURN VALUE
.PP
On success, the \f[B]pmemblk_read\f[R]() and \f[B]pmemblk_write\f[R]()
functions return 0.
On error, they return -1 and set \f[I]errno\f[R] appropriately.
.SH SEE ALSO
.PP
\f[B]libpmemblk\f[R](7) and \f[B]<https://pmem.io>\f[R]