minix/lib/libc/cdb/cdbw.3

.\"	$NetBSD: cdbw.3,v 1.6 2013/07/20 21:39:56 wiz Exp $
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.\" Copyright (c) 2010 The NetBSD Foundation, Inc.
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Joerg Sonnenberger.
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.Dd June 3, 2012
.Dt CDBW 3
.Os
.Sh NAME
.Nm cdbw_open ,
.Nm cdbw_put ,
.Nm cdbw_put_data ,
.Nm cdbw_put_key ,
.Nm cdbw_stable_seeder ,
.Nm cdbw_output ,
.Nm cdbw_close
.Nd create constant databases
.Sh SYNOPSIS
.In archive_entry.h
.Ft "struct cdbw *"
.Fn cdbw_open "void"
.Ft int
.Fo cdbw_put
.Fa "struct cdbw *cdbw"
.Fa "const void *key"
.Fa "size_t keylen"
.Fa "const void *data"
.Fa "size_t datalen"
.Fc
.Ft int
.Fo cdbw_put_data
.Fa "struct cdbw *cdbw"
.Fa "const void *data"
.Fa "size_t datalen"
.Fa "uint32_t *index"
.Fc
.Ft int
.Fo cdbw_put_key
.Fa "struct cdbw *cdbw"
.Fa "const void *key"
.Fa "size_t keylen"
.Fa "uint32_t index"
.Fc
.Ft uint32_t
.Fo cdbw_stable_seeder
.Fa "void"
.Fc
.Ft int
.Fo cdbw_output
.Fa "struct cdbw *cdbw"
.Fa "int output"
.Fa "const char descr[16]"
.Fa "uint32_t (*seedgen)(void)"
.Fc
.Ft void
.Fn cdbw_close "struct cdbw *cdbw"
.Sh DESCRIPTION
The
.Nm cdbw
functions are used to create a constant databases for use with
.Xr cdbr 3 .
Details about the file format, including overhead and limitations,
can be found in
.Xr cdb 5 .
.Pp
.Fn cdbw_open
prepares a new
.Nm cdb
writer.
The function returns a handle to pass to the other functions.
.Pp
.Fn cdbw_close
frees all resources associated with the handle.
.Pp
.Fn cdbw_put
adds the given (key,value) pair after checking for a duplicate key.
.Fn cdbw_put_data
adds the given value to the writer without adding a key reference.
The returned index can be used in subsequent calls to
.Fn cdbw_put_key
to add one or more keys pointing to this value.
.Fn cdbw_put_key
checks for duplicate keys and valid index arguments.
On success it adds the given key.
.Pp
.Fn cdbw_output
computes the database file and writes it to the given descriptor.
The function returns an error if the file cannot be written correctly.
The
.Fn descr
parameter provides a human readable description of the database content.
The
.Fn seedgen
parameter can be used to override the default PRNG.
The bitwise layout of the output depends on the chosen seed.
The function should return a different value for each invocation.
The
.Fn cdbw_stable_seeder
can be used to create reproducible output.
It may be slower than the default.
.Sh SEE ALSO
.Xr cdbr 3 ,
.Xr cdb 5
.Sh HISTORY
Support for the
.Nm cdb
format first appeared in
.Nx 6.0 .
.Sh AUTHORS
The
.Nm cdbr
and
.Nm cdbw
functions have been written by
.An Joerg Sonnenberger Aq Mt joerg@NetBSD.org .