.\" Automatically generated by Pandoc 2.2.1
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.TH "PMEMBLK_READ" "3" "2019-02-19" "PMDK - pmemblk API version 1.1" "PMDK Programmer's Manual"
.hy
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.SH NAME
.PP
\f[B]pmemblk_read\f[](), \f[B]pmemblk_write\f[]() \- 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[]
.fi
.SH DESCRIPTION
.PP
The \f[B]pmemblk_read\f[]() function reads the block with block number
\f[I]blockno\f[] from memory pool \f[I]pbp\f[] into the buffer
\f[I]buf\f[].
Reading a block that has never been written by \f[B]pmemblk_write\f[]()
will return a block of zeroes.
.PP
The \f[B]pmemblk_write\f[]() function writes a block from \f[I]buf\f[]
to block number \f[I]blockno\f[] in the memory pool \f[I]pbp\f[].
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[]() and \f[B]pmemblk_write\f[]()
functions return 0.
On error, they return \-1 and set \f[I]errno\f[] appropriately.
.SH SEE ALSO
.PP
\f[B]libpmemblk\f[](7) and \f[B]<http://pmem.io>\f[]