VILLA(3) Quick Database Manager VILLA(3)NAME
Villa - the advanced API of QDBM
SYNOPSIS
#include <depot.h>
#include <cabin.h>
#include <villa.h>
#include <stdlib.h>
typedef int(*VLCFUNC)(const char *aptr, int asiz, const char *bptr, int
bsiz);
VILLA *vlopen(const char *name, int omode, VLCFUNC cmp);
int vlclose(VILLA *villa);
int vlput(VILLA *villa, const char *kbuf, int ksiz, const char *vbuf,
int vsiz, int dmode);
int vlout(VILLA *villa, const char *kbuf, int ksiz);
char *vlget(VILLA *villa, const char *kbuf, int ksiz, int *sp);
int vlvsiz(VILLA *villa, const char *kbuf, int ksiz);
int vlvnum(VILLA *villa, const char *kbuf, int ksiz);
int vlputlist(VILLA *villa, const char *kbuf, int ksiz, const CBLIST
*vals);
int vloutlist(VILLA *villa, const char *kbuf, int ksiz);
CBLIST *vlgetlist(VILLA *villa, const char *kbuf, int ksiz);
char *vlgetcat(VILLA *villa, const char *kbuf, int ksiz, int *sp);
int vlcurfirst(VILLA *villa);
int vlcurlast(VILLA *villa);
int vlcurprev(VILLA *villa);
int vlcurnext(VILLA *villa);
int vlcurjump(VILLA *villa, const char *kbuf, int ksiz, int jmode);
char *vlcurkey(VILLA *villa, int *sp);
char *vlcurval(VILLA *villa, int *sp);
int vlcurput(VILLA *villa, const char *vbuf, int vsiz, int cpmode);
int vlcurout(VILLA *villa);
void vlsettuning(VILLA *villa, int lrecmax, int nidxmax, int lcnum, int
ncnum);
int vlsetfbpsiz(VILLA *villa, int size);
int vlsync(VILLA *villa);
int vloptimize(VILLA *villa);
char *vlname(VILLA *villa);
int vlfsiz(VILLA *villa);
int vllnum(VILLA *villa);
int vlnnum(VILLA *villa);
int vlrnum(VILLA *villa);
int vlwritable(VILLA *villa);
int vlfatalerror(VILLA *villa);
int vlinode(VILLA *villa);
time_t vlmtime(VILLA *villa);
int vltranbegin(VILLA *villa);
int vltrancommit(VILLA *villa);
int vltranabort(VILLA *villa);
int vlremove(const char *name);
int vlrepair(const char *name, VLCFUNC cmp);
int vlexportdb(VILLA *villa, const char *name);
int vlimportdb(VILLA *villa, const char *name);
DESCRIPTION
Villa is the advanced API of QDBM. It provides routines for managing a
database file of B+ tree. Each record is stored being sorted in order
defined by a user. As for hash databases, retrieving method is pro‐
vided only as complete accord. However, with Villa, it is possible to
retrieve records specified by range. Cursor is used in order to access
each record in order. It is possible to store records duplicating keys
in a database. Moreover, according to the transaction mechanism, you
can commit or abort operations of a database in a lump.
Villa is implemented, based on Depot and Cabin. A database file of
Villa is actual one of Depot. Although processing speed of retrieving
and storing is slower than Depot, the size of a database is smaller.
In order to use Villa, you should include `depot.h', `cabin.h',
`villa.h' and `stdlib.h' in the source files. Usually, the following
description will be near the beginning of a source file.
#include <depot.h>
#include <cabin.h>
#include <villa.h>
#include <stdlib.h>
A pointer to `VILLA' is used as a database handle. It is like that some
file I/O routines of `stdio.h' use a pointer to `FILE'. A database
handle is opened with the function `vlopen' and closed with `vlclose'.
You should not refer directly to any member of the handle. If a fatal
error occurs in a database, any access method via the handle except
`vlclose' will not work and return error status. Although a process is
allowed to use multiple database handles at the same time, handles of
the same database file should not be used. Before the cursor is used,
it should be initialized by one of `vlcurfirst', `vlcurlast' or `vlcur‐
jump'. Also after storing or deleting a record with functions except
for `vlcurput' and `vlcurout', the cursor should be initialized.
Villa also assign the external variable `dpecode' with the error code.
The function `dperrmsg' is used in order to get the message of the
error code.
You can define a comparing function to specify the order of records.
The function should be the following type.
typedef int(*VLCFUNC)(const char *aptr, int asiz, const char *bptr, int
bsiz);
`aptr' specifies the pointer to the region of one key. `asiz'
specifies the size of the region of one key. `bptr' specifies
the pointer to the region of the other key. `bsiz' specifies
the size of the region of the other key. The return value is
positive if the former is big, negative if the latter is big, 0
if both are equivalent.
The function `vlopen' is used in order to get a database handle.
VILLA *vlopen(const char *name, int omode, VLCFUNC cmp);
`name' specifies the name of a database file. `omode' specifies
the connection mode: `VL_OWRITER' as a writer, `VL_OREADER' as a
reader. If the mode is `VL_OWRITER', the following may be added
by bitwise or: `VL_OCREAT', which means it creates a new data‐
base if not exist, `VL_OTRUNC', which means it creates a new
database regardless if one exists, `VL_OZCOMP', which means
leaves in the database are compressed, `VL_OYCOMP', which means
leaves in the database are compressed with LZO, `VL_OXCOMP',
which means leaves in the database are compressed with BZIP2.
Both of `VL_OREADER' and `VL_OWRITER' can be added to by bitwise
or: `VL_ONOLCK', which means it opens a database file without
file locking, or `VL_OLCKNB', which means locking is performed
without blocking. `cmp' specifies the comparing function:
`VL_CMPLEX' comparing keys in lexical order, `VL_CMPINT' compar‐
ing keys as objects of `int' in native byte order, `VL_CMPNUM'
comparing keys as numbers of big endian, `VL_CMPDEC' comparing
keys as decimal strings. Any function based on the declaration
of the type `VLCFUNC' can be assigned to the comparing function.
The comparing function should be kept same in the life of a
database. The return value is the database handle or `NULL' if
it is not successful. While connecting as a writer, an exclu‐
sive lock is invoked to the database file. While connecting as
a reader, a shared lock is invoked to the database file. The
thread blocks until the lock is achieved. `VL_OZCOMP',
`VL_OYCOMP', and `VL_OXCOMP' are available only if QDBM was
built each with ZLIB, LZO, and BZIP2 enabled. If `VL_ONOLCK' is
used, the application is responsible for exclusion control.
The function `vlclose' is used in order to close a database handle.
int vlclose(VILLA *villa);
`villa' specifies a database handle. If successful, the return
value is true, else, it is false. Because the region of a
closed handle is released, it becomes impossible to use the han‐
dle. Updating a database is assured to be written when the han‐
dle is closed. If a writer opens a database but does not close
it appropriately, the database will be broken. If the transac‐
tion is activated and not committed, it is aborted.
The function `vlput' is used in order to store a record.
int vlput(VILLA *villa, const char *kbuf, int ksiz, const char *vbuf,
int vsiz, int dmode);
`villa' specifies a database handle connected as a writer.
`kbuf' specifies the pointer to the region of a key. `ksiz'
specifies the size of the region of the key. If it is negative,
the size is assigned with `strlen(kbuf)'. `vbuf' specifies the
pointer to the region of a value. `vsiz' specifies the size of
the region of the value. If it is negative, the size is
assigned with `strlen(vbuf)'. `dmode' specifies behavior when
the key overlaps, by the following values: `VL_DOVER', which
means the specified value overwrites the existing one,
`VL_DKEEP', which means the existing value is kept, `VL_DCAT',
which means the specified value is concatenated at the end of
the existing value, `VL_DDUP', which means duplication of keys
is allowed and the specified value is added as the last one,
`VL_DDUPR', which means duplication of keys is allowed and the
specified value is added as the first one. If successful, the
return value is true, else, it is false. The cursor becomes
unavailable due to updating database.
The function `vlout' is used in order to delete a record.
int vlout(VILLA *villa, const char *kbuf, int ksiz);
`villa' specifies a database handle connected as a writer.
`kbuf' specifies the pointer to the region of a key. `ksiz'
specifies the size of the region of the key. If it is negative,
the size is assigned with `strlen(kbuf)'. If successful, the
return value is true, else, it is false. False is returned when
no record corresponds to the specified key. When the key of
duplicated records is specified, the first record of the same
key is deleted. The cursor becomes unavailable due to updating
database.
The function `vlget' is used in order to retrieve a record.
char *vlget(VILLA *villa, const char *kbuf, int ksiz, int *sp);
`villa' specifies a database handle. `kbuf' specifies the
pointer to the region of a key. `ksiz' specifies the size of
the region of the key. If it is negative, the size is assigned
with `strlen(kbuf)'. `sp' specifies the pointer to a variable
to which the size of the region of the return value is assigned.
If it is `NULL', it is not used. If successful, the return
value is the pointer to the region of the value of the corre‐
sponding record, else, it is `NULL'. `NULL' is returned when no
record corresponds to the specified key. When the key of dupli‐
cated records is specified, the value of the first record of the
same key is selected. Because an additional zero code is
appended at the end of the region of the return value, the
return value can be treated as a character string. Because the
region of the return value is allocated with the `malloc' call,
it should be released with the `free' call if it is no longer in
use.
The function `vlvsiz' is used in order to get the size of the value of
a record.
int vlvsiz(VILLA *villa, const char *kbuf, int ksiz);
`villa' specifies a database handle. `kbuf' specifies the
pointer to the region of a key. `ksiz' specifies the size of
the region of the key. If it is negative, the size is assigned
with `strlen(kbuf)'. If successful, the return value is the
size of the value of the corresponding record, else, it is -1.
If multiple records correspond, the size of the first is
returned.
The function `vlvnum' is used in order to get the number of records
corresponding a key.
int vlvnum(VILLA *villa, const char *kbuf, int ksiz);
`villa' specifies a database handle. `kbuf' specifies the
pointer to the region of a key. `ksiz' specifies the size of
the region of the key. If it is negative, the size is assigned
with `strlen(kbuf)'. The return value is the number of corre‐
sponding records. If no record corresponds, 0 is returned.
The function `vlputlist' is used in order to store plural records cor‐
responding a key.
int vlputlist(VILLA *villa, const char *kbuf, int ksiz, const CBLIST
*vals);
`villa' specifies a database handle connected as a writer.
`kbuf' specifies the pointer to the region of a key. `ksiz'
specifies the size of the region of the key. If it is negative,
the size is assigned with `strlen(kbuf)'. `vals' specifies a
list handle of values. The list should not be empty. If suc‐
cessful, the return value is true, else, it is false. The cur‐
sor becomes unavailable due to updating database.
The function `vloutlist' is used in order to delete all records corre‐
sponding a key.
int vloutlist(VILLA *villa, const char *kbuf, int ksiz);
`villa' specifies a database handle connected as a writer.
`kbuf' specifies the pointer to the region of a key. `ksiz'
specifies the size of the region of the key. If it is negative,
the size is assigned with `strlen(kbuf)'. If successful, the
return value is true, else, it is false. False is returned when
no record corresponds to the specified key. The cursor becomes
unavailable due to updating database.
The function `vlgetlist' is used in order to retrieve values of all
records corresponding a key.
CBLIST *vlgetlist(VILLA *villa, const char *kbuf, int ksiz);
`villa' specifies a database handle. `kbuf' specifies the
pointer to the region of a key. `ksiz' specifies the size of
the region of the key. If it is negative, the size is assigned
with `strlen(kbuf)'. If successful, the return value is a list
handle of the values of the corresponding records, else, it is
`NULL'. `NULL' is returned when no record corresponds to the
specified key. Because the handle of the return value is opened
with the function `cblistopen', it should be closed with the
function `cblistclose' if it is no longer in use.
The function `vlgetcat' is used in order to retrieve concatenated val‐
ues of all records corresponding a key.
char *vlgetcat(VILLA *villa, const char *kbuf, int ksiz, int *sp);
`villa' specifies a database handle. `kbuf' specifies the
pointer to the region of a key. `ksiz' specifies the size of
the region of the key. If it is negative, the size is assigned
with `strlen(kbuf)'. `sp' specifies the pointer to a variable
to which the size of the region of the return value is assigned.
If it is `NULL', it is not used. If successful, the return
value is the pointer to the region of the concatenated values of
the corresponding record, else, it is `NULL'. `NULL' is
returned when no record corresponds to the specified key.
Because an additional zero code is appended at the end of the
region of the return value, the return value can be treated as a
character string. Because the region of the return value is
allocated with the `malloc' call, it should be released with the
`free' call if it is no longer in use.
The function `vlcurfirst' is used in order to move the cursor to the
first record.
int vlcurfirst(VILLA *villa);
`villa' specifies a database handle. If successful, the return
value is true, else, it is false. False is returned if there is
no record in the database.
The function `vlcurlast' is used in order to move the cursor to the
last record.
int vlcurlast(VILLA *villa);
`villa' specifies a database handle. If successful, the return
value is true, else, it is false. False is returned if there is
no record in the database.
The function `vlcurprev' is used in order to move the cursor to the
previous record.
int vlcurprev(VILLA *villa);
`villa' specifies a database handle. If successful, the return
value is true, else, it is false. False is returned if there is
no previous record.
The function `vlcurnext' is used in order to move the cursor to the
next record.
int vlcurnext(VILLA *villa);
`villa' specifies a database handle. If successful, the return
value is true, else, it is false. False is returned if there is
no next record.
The function `vlcurjump' is used in order to move the cursor to a posi‐
tion around a record.
int vlcurjump(VILLA *villa, const char *kbuf, int ksiz, int jmode);
`villa' specifies a database handle. `kbuf' specifies the
pointer to the region of a key. `ksiz' specifies the size of
the region of the key. If it is negative, the size is assigned
with `strlen(kbuf)'. `jmode' specifies detail adjustment:
`VL_JFORWARD', which means that the cursor is set to the first
record of the same key and that the cursor is set to the next
substitute if completely matching record does not exist,
`VL_JBACKWARD', which means that the cursor is set to the last
record of the same key and that the cursor is set to the previ‐
ous substitute if completely matching record does not exist. If
successful, the return value is true, else, it is false. False
is returned if there is no record corresponding the condition.
The function `vlcurkey' is used in order to get the key of the record
where the cursor is.
char *vlcurkey(VILLA *villa, int *sp);
`villa' specifies a database handle. `sp' specifies the pointer
to a variable to which the size of the region of the return
value is assigned. If it is `NULL', it is not used. If suc‐
cessful, the return value is the pointer to the region of the
key of the corresponding record, else, it is `NULL'. `NULL' is
returned when no record corresponds to the cursor. Because an
additional zero code is appended at the end of the region of the
return value, the return value can be treated as a character
string. Because the region of the return value is allocated
with the `malloc' call, it should be released with the `free'
call if it is no longer in use.
The function `vlcurval' is used in order to get the value of the record
where the cursor is.
char *vlcurval(VILLA *villa, int *sp);
`villa' specifies a database handle. `sp' specifies the pointer
to a variable to which the size of the region of the return
value assigned. If it is `NULL', it is not used. If success‐
ful, the return value is the pointer to the region of the value
of the corresponding record, else, it is `NULL'. `NULL' is
returned when no record corresponds to the cursor. Because an
additional zero code is appended at the end of the region of the
return value, the return value can be treated as a character
string. Because the region of the return value is allocated
with the `malloc' call, it should be released with the `free'
call if it is no longer in use.
The function `vlcurput' is used in order to insert a record around the
cursor.
int vlcurput(VILLA *villa, const char *vbuf, int vsiz, int cpmode);
`villa' specifies a database handle connected as a writer.
`vbuf' specifies the pointer to the region of a value. `vsiz'
specifies the size of the region of the value. If it is nega‐
tive, the size is assigned with `strlen(vbuf)'. `cpmode' speci‐
fies detail adjustment: `VL_CPCURRENT', which means that the
value of the current record is overwritten, `VL_CPBEFORE', which
means that a new record is inserted before the current record,
`VL_CPAFTER', which means that a new record is inserted after
the current record. If successful, the return value is true,
else, it is false. False is returned when no record corresponds
to the cursor. After insertion, the cursor is moved to the
inserted record.
The function `vlcurout' is used in order to delete the record where the
cursor is.
int vlcurout(VILLA *villa);
`villa' specifies a database handle connected as a writer. If
successful, the return value is true, else, it is false. False
is returned when no record corresponds to the cursor. After
deletion, the cursor is moved to the next record if possible.
The function `vlsettuning' is used in order to set the tuning parame‐
ters for performance.
void vlsettuning(VILLA *villa, int lrecmax, int nidxmax, int lcnum, int
ncnum);
`villa' specifies a database handle. `lrecmax' specifies the
max number of records in a leaf node of B+ tree. If it is not
more than 0, the default value is specified. `nidxmax' speci‐
fies the max number of indexes in a non-leaf node of B+ tree.
If it is not more than 0, the default value is specified.
`lcnum' specifies the max number of caching leaf nodes. If it
is not more than 0, the default value is specified. `ncnum'
specifies the max number of caching non-leaf nodes. If it is
not more than 0, the default value is specified. The default
setting is equivalent to `vlsettuning(49, 192, 1024, 512)'.
Because tuning parameters are not saved in a database, you
should specify them every opening a database.
The function `vlsetfbpsiz' is used in order to set the size of the free
block pool of a database handle.
int vlsetfbpsiz(VILLA *villa, int size);
`villa' specifies a database handle connected as a writer.
`size' specifies the size of the free block pool of a database.
If successful, the return value is true, else, it is false. The
default size of the free block pool is 256. If the size is
greater, the space efficiency of overwriting values is improved
with the time efficiency sacrificed.
The function `vlsync' is used in order to synchronize updating contents
with the file and the device.
int vlsync(VILLA *villa);
`villa' specifies a database handle connected as a writer. If
successful, the return value is true, else, it is false. This
function is useful when another process uses the connected data‐
base file. This function should not be used while the transac‐
tion is activated.
The function `vloptimize' is used in order to optimize a database.
int vloptimize(VILLA *villa);
`villa' specifies a database handle connected as a writer. If
successful, the return value is true, else, it is false. In an
alternating succession of deleting and storing with overwrite or
concatenate, dispensable regions accumulate. This function is
useful to do away with them. This function should not be used
while the transaction is activated.
The function `vlname' is used in order to get the name of a database.
char *vlname(VILLA *villa);
`villa' specifies a database handle. If successful, the return
value is the pointer to the region of the name of the database,
else, it is `NULL'. Because the region of the return value is
allocated with the `malloc' call, it should be released with the
`free' call if it is no longer in use.
The function `vlfsiz' is used in order to get the size of a database
file.
int vlfsiz(VILLA *villa);
`villa' specifies a database handle. If successful, the return
value is the size of the database file, else, it is -1. Because
of the I/O buffer, the return value may be less than the hard
size.
The function `vllnum' is used in order to get the number of the leaf
nodes of B+ tree.
int vllnum(VILLA *villa);
`villa' specifies a database handle. If successful, the return
value is the number of the leaf nodes, else, it is -1.
The function `vlnnum' is used in order to get the number of the
non-leaf nodes of B+ tree.
int vlnnum(VILLA *villa);
`villa' specifies a database handle. If successful, the return
value is the number of the non-leaf nodes, else, it is -1.
The function `vlrnum' is used in order to get the number of the records
stored in a database.
int vlrnum(VILLA *villa);
`villa' specifies a database handle. If successful, the return
value is the number of the records stored in the database, else,
it is -1.
The function `vlwritable' is used in order to check whether a database
handle is a writer or not.
int vlwritable(VILLA *villa);
`villa' specifies a database handle. The return value is true
if the handle is a writer, false if not.
The function `vlfatalerror' is used in order to check whether a data‐
base has a fatal error or not.
int vlfatalerror(VILLA *villa);
`villa' specifies a database handle. The return value is true
if the database has a fatal error, false if not.
The function `vlinode' is used in order to get the inode number of a
database file.
int vlinode(VILLA *villa);
`villa' specifies a database handle. The return value is the
inode number of the database file.
The function `vlmtime' is used in order to get the last modified time
of a database.
time_t vlmtime(VILLA *villa);
`villa' specifies a database handle. The return value is the
last modified time of the database.
The function `vltranbegin' is used in order to begin the transaction.
int vltranbegin(VILLA *villa);
`villa' specifies a database handle connected as a writer. If
successful, the return value is true, else, it is false.
Because this function does not perform mutual exclusion control
in multi-thread, the application is responsible for it. Only
one transaction can be activated with a database handle at the
same time.
The function `vltrancommit' is used in order to commit the transaction.
int vltrancommit(VILLA *villa);
`villa' specifies a database handle connected as a writer. If
successful, the return value is true, else, it is false. Updat‐
ing a database in the transaction is fixed when it is committed
successfully.
The function `vltranabort' is used in order to abort the transaction.
int vltranabort(VILLA *villa);
`villa' specifies a database handle connected as a writer. If
successful, the return value is true, else, it is false. Updat‐
ing a database in the transaction is discarded when it is
aborted. The state of the database is rollbacked to before
transaction.
The function `vlremove' is used in order to remove a database file.
int vlremove(const char *name);
`name' specifies the name of a database file. If successful,
the return value is true, else, it is false.
The function `vlrepair' is used in order to repair a broken database
file.
int vlrepair(const char *name, VLCFUNC cmp);
`name' specifies the name of a database file. `cmp' specifies
the comparing function of the database file. If successful, the
return value is true, else, it is false. There is no guarantee
that all records in a repaired database file correspond to the
original or expected state.
The function `vlexportdb' is used in order to dump all records as
endian independent data.
int vlexportdb(VILLA *villa, const char *name);
`villa' specifies a database handle. `name' specifies the name
of an output file. If successful, the return value is true,
else, it is false.
The function `vlimportdb' is used in order to load all records from
endian independent data.
int vlimportdb(VILLA *villa, const char *name);
`villa' specifies a database handle connected as a writer. The
database of the handle must be empty. `name' specifies the name
of an input file. If successful, the return value is true,
else, it is false.
If QDBM was built with POSIX thread enabled, the global variable
`dpecode' is treated as thread specific data, and functions of Villa
are reentrant. In that case, they are thread-safe as long as a handle
is not accessed by threads at the same time, on the assumption that
`errno', `malloc', and so on are thread-safe.
Vista is the extended API of Villa. To compensate for the defect that
Villa can not handle a file whose size is more than 2GB, Vista does not
use Depot but Curia for handling its internal database. While Vista
provides data structure and operations of B+ tree as with Villa, its
database is realized as a directory.
In order to use Vista, you should include `vista.h' instead of
`villa.h'. Because Vista is implemented by overriding symbols of
Villa, it can be used as with Villa. That is, Signatures of Villa and
Vista is all the same. However, as its adverse effect, modules using
Vista can not use Depot nor Villa.
SEE ALSOqdbm(3), depot(3), curia(3), relic(3), hovel(3), cabin(3), odeum(3),
ndbm(3), gdbm(3)Man Page 2004-04-22 VILLA(3)
