Provided by: libqdbm-dev_1.8.78-11build3_amd64 
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 provided 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 `vlcurjump'. 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 database 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' comparing 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 exclusive 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 handle. Updating a database is assured to be written when
the handle is closed. If a writer opens a database but does not close it
appropriately, the database will be broken. If the transaction 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 corresponding record, else, it is `NULL'. `NULL' is returned when no
record corresponds to the specified key. When the key of duplicated 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
corresponding records. If no record corresponds, 0 is returned.
The function `vlputlist' is used in order to store plural records corresponding 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 successful,
the return value is true, else, it is false. The cursor becomes unavailable due to
updating database.
The function `vloutlist' is used in order to delete all records corresponding 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 values 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 position 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 previous 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 successful, 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 successful, 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 negative, the size is assigned with `strlen(vbuf)'. `cpmode'
specifies 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 parameters 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' specifies 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 database file. This function should not be used while
the transaction 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 database 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. Updating 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. Updating 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 ALSO
qdbm(3), depot(3), curia(3), relic(3), hovel(3), cabin(3), odeum(3), ndbm(3), gdbm(3)