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.TH qlibs:cdbread 3
.SH NAME
cdbread \- fetch information from a constant database
.SH SYNTAX
.B #include \(dqcdbread.h\(dq
void \fBcdb_init\fP(struct cdb *\fIc\fR,int \fIfd\fR);
.br
int \fBcdb_read\fP(struct cdb *\fIc\fR,char *\fIdata\fR,unsigned int \fIdlen\fR,uint32 \fIpos\fR);
.br
int \fBcdb_findstart\fP(int \fIfd\fR,char *\fIkey\fR,unsigned int \fIlen\fR);
.br
int \fBcdb_findnext\fP(int \fIfd\fR,char *\fIkey\fR,unsigned int \fIlen\fR);
.br
int \fBcdb_find\fP(int \fIfd\fR,char *\fIney\fR,unsigned int \fIlen\fR);
.br
int \fBcdb_findnext\fP(int \fIfd\fR,char *\fIkey\fR,unsigned int \fIlen\fR);
.br
void \fBcdb_free\fP(struct cdb *\fIc\fR):
.SH DESCRIPTION
.B cdb_free
unallocates
.I c
if
.I c
is allocated.
Otherwise it leaves
.I c
alone.
.B cdb_free
does not close
.IR fd .
.B cdb_init
allocates
.B c
to hold information about a constant database read by descriptor
.IR fd .
You may call
.B cdb_init
repeatedly; if
.I c
is already allocated,
.B cdb_init
unallocates it first.
.B cdb_read
reads
.I dlen
bytes into
.I d
from byte position
.I dpos
in the database. You must allocate
.I c
before calling
.BR cdb_read .
Normally
.B cdb_read
returns
.IR 0 .
If the database file is shorter than
.I dpos+dlen
bytes, or if there is a disk read error,
.B cdb_read
returns
.IR -1 ,
setting
.I errno
appropriately.
.B cdb_findstart
prepares
.I c
to search for the first record under a new
.IR key .
You must allocate
.I c
before calling
.BR cdb_findstart ,
and you must call
.B cdb_findstart
before calling
.BR cdb_findnext .
.B cdb_findnext
looks for the nth record under
.I key
in the database, where
.I n
is the number of calls to
.B cdb_findnext
after the most recent call to
.BR cdb_findstart .
If it finds the record,
.B cdb_findnext
returns
.IR 1 ;
if there are exactly n-1 such records,
.B cdb_findnext
returns
.IR 0 ;
if there are fewer than n-1 such records, the behavior of
.B cdb_findnext
is undefined; if there is a database format error or disk error,
.B cdb_findnext
returns
.IR -1 , setting
.I errno
appropriately. Each call to
.B cdb_findnext
(before another call to
.BR cdb_findstart )
must use the same
.I k
and
.IR klen .
If
.B cdb_findnext
returns
.IR 1 ,
it arranges for
.B cdb_datapos
to return the starting byte position of the data in the record, and for
.B cdb_datalen
to return the number of bytes of data in the record.
Otherwise the results of
.B cdb_datapos
and
.B cdb_datalen
are undefined.
.B cdb_find
is the same as
.B cdb_findstart
followed by
.BR cdb_findnext :
it finds the first record under
.IR key.
.B cdb_datapos
and
.B cdb_datalen
are macros pointing to the found information following
.I key
in the cdb and returning their length.
.SH EXAMPLE
#include <cdbread.h>
int fd;
char *data;
unsigned int len;
stralloc key = {0};
static struct cdb c;
cdb_init(&c,fd);
switch (cdb_find(&c,key.s,key.len)) {
case -1: return -1;
case 0: return 0;
}
len = cdb_datalen(&c);
data = alloc(len);
if (!data) return -1;
if (cdb_read(&c,data,datalen,cdb_datapos(&c)) == -1) {
alloc_free(data);
return -1;
}
cdb_free(&c);
.SH "SEE ALSO"
cdbmake(3)
|
