DEPOT(3)                    Quick Database Manager                    DEPOT(3)



NAME
       Depot - the basic API of QDBM


SYNOPSIS
       #include <depot.h>
       #include <stdlib.h>

       extern const char *dpversion;

       extern int dpecode;

       const char *dperrmsg(int ecode);

       DEPOT *dpopen(const char *name, int omode, int bnum);

       int dpclose(DEPOT *depot);

       int dpput(DEPOT *depot, const char *kbuf, int ksiz, const char *vbuf,
       int vsiz, int dmode);

       int dpout(DEPOT *depot, const char *kbuf, int ksiz);

       char *dpget(DEPOT *depot, const char *kbuf, int ksiz, int start, int
       max, int *sp);

       int dpgetwb(DEPOT *depot, const char *kbuf, int ksiz, int start, int
       max, char *vbuf);

       int dpvsiz(DEPOT *depot, const char *kbuf, int ksiz);

       int dpiterinit(DEPOT *depot);

       char *dpiternext(DEPOT *depot, int *sp);

       int dpsetalign(DEPOT *depot, int align);

       int dpsetfbpsiz(DEPOT *depot, int size);

       int dpsync(DEPOT *depot);

       int dpoptimize(DEPOT *depot, int bnum);

       char *dpname(DEPOT *depot);

       int dpfsiz(DEPOT *depot);

       int dpbnum(DEPOT *depot);

       int dpbusenum(DEPOT *depot);

       int dprnum(DEPOT *depot);

       int dpwritable(DEPOT *depot);

       int dpfatalerror(DEPOT *depot);

       int dpinode(DEPOT *depot);

       time_t dpmtime(DEPOT *depot);

       int dpfdesc(DEPOT *depot);

       int dpremove(const char *name);

       int dprepair(const char *name);

       int dpexportdb(DEPOT *depot, const char *name);

       int dpimportdb(DEPOT *depot, const char *name);

       char *dpsnaffle(const char *name, const char *kbuf, int ksiz, int *sp);

       int dpinnerhash(const char *kbuf, int ksiz);

       int dpouterhash(const char *kbuf, int ksiz);

       int dpprimenum(int num);


DESCRIPTION
       Depot is the basic API of QDBM.  Almost all features for managing a
       database provided by QDBM are implemented by Depot.  Other APIs are no
       more than wrappers of Depot.  Depot is the fastest in all APIs of QDBM.

       In order to use Depot, you should include `depot.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 <stdlib.h>

       A pointer to `DEPOT' 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 `dpopen' and closed with
       `dpclose'.  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 `dpclose' 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.

       The external variable `dpversion' is the string containing the version
       information.

       extern const char *dpversion;

       The external variable `dpecode' is assigned with the last happened
       error code.  Refer to `depot.h' for details of the error codes.

       extern int dpecode;
              The initial value of this variable is `DP_NOERR'.  The other
              values are `DP_EFATAL', `DP_EMODE', `DP_EBROKEN', `DP_EKEEP',
              `DP_ENOITEM', `DP_EALLOC', `DP_EMAP', `DP_EOPEN', `DP_ECLOSE',
              `DP_ETRUNC', `DP_ESYNC', `DP_ESTAT', `DP_ESEEK', `DP_EREAD',
              `DP_EWRITE', `DP_ELOCK', `DP_EUNLINK', `DP_EMKDIR', `DP_ERMDIR',
              and `DP_EMISC'.

       The function `dperrmsg' is used in order to get a message string
       corresponding to an error code.

       const char *dperrmsg(int ecode);
              `ecode' specifies an error code.  The return value is the
              message string of the error code.  The region of the return
              value is not writable.

       The function `dpopen' is used in order to get a database handle.

       DEPOT *dpopen(const char *name, int omode, int bnum);
              `name' specifies the name of a database file.  `omode' specifies
              the connection mode: `DP_OWRITER' as a writer, `DP_OREADER' as a
              reader.  If the mode is `DP_OWRITER', the following may be added
              by bitwise or: `DP_OCREAT', which means it creates a new
              database if not exist, `DP_OTRUNC', which means it creates a new
              database regardless if one exists.  Both of `DP_OREADER' and
              `DP_OWRITER' can be added to by bitwise or: `DP_ONOLCK', which
              means it opens a database file without file locking, or
              `DP_OLCKNB', which means locking is performed without blocking.
              `DP_OCREAT' can be added to by bitwise or: `DP_OSPARSE', which
              means it creates a database file as a sparse file.  `bnum'
              specifies the number of elements of the bucket array.  If it is
              not more than 0, the default value is specified.  The size of a
              bucket array is determined on creating, and can not be changed
              except for by optimization of the database.  Suggested size of a
              bucket array is about from 0.5 to 4 times of the number of all
              records to store.  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.  If
              `DP_ONOLCK' is used, the application is responsible for
              exclusion control.

       The function `dpclose' is used in order to close a database handle.

       int dpclose(DEPOT *depot);
              `depot' 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.

       The function `dpput' is used in order to store a record.

       int dpput(DEPOT *depot, const char *kbuf, int ksiz, const char *vbuf,
       int vsiz, int dmode);
              `depot' 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: `DP_DOVER', which
              means the specified value overwrites the existing one,
              `DP_DKEEP', which means the existing value is kept, `DP_DCAT',
              which means the specified value is concatenated at the end of
              the existing value.  If successful, the return value is true,
              else, it is false.

       The function `dpout' is used in order to delete a record.

       int dpout(DEPOT *depot, const char *kbuf, int ksiz);
              `depot' 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 function `dpget' is used in order to retrieve a record.

       char *dpget(DEPOT *depot, const char *kbuf, int ksiz, int start, int
       max, int *sp);
              `depot' 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)'.  `start' specifies the offset address of
              the beginning of the region of the value to be read.  `max'
              specifies the max size to be read.  If it is negative, the size
              to read is unlimited.  `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 or the size of
              the value of the corresponding record is less than `start'.
              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 `dpgetwb' is used in order to retrieve a record and write
       the value into a buffer.

       int dpgetwb(DEPOT *depot, const char *kbuf, int ksiz, int start, int
       max, char *vbuf);
              `depot' 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)'.  `start' specifies the offset address of
              the beginning of the region of the value to be read.  `max'
              specifies the max size to be read.  It shuld be equal to or less
              than the size of the writing buffer.  `vbuf' specifies the
              pointer to a buffer into which the value of the corresponding
              record is written.  If successful, the return value is the size
              of the written data, else, it is -1.  -1 is returned when no
              record corresponds to the specified key or the size of the value
              of the corresponding record is less than `start'.  Note that no
              additional zero code is appended at the end of the region of the
              writing buffer.

       The function `dpvsiz' is used in order to get the size of the value of
       a record.

       int dpvsiz(DEPOT *depot, const char *kbuf, int ksiz);
              `depot' 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.
              Because this function does not read the entity of a record, it
              is faster than `dpget'.

       The function `dpiterinit' is used in order to initialize the iterator
       of a database handle.

       int dpiterinit(DEPOT *depot);
              `depot' specifies a database handle.  If successful, the return
              value is true, else, it is false.  The iterator is used in order
              to access the key of every record stored in a database.

       The function `dpiternext' is used in order to get the next key of the
       iterator.

       char *dpiternext(DEPOT *depot, int *sp);
              `depot' 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
              next key, else, it is `NULL'.  `NULL' is returned when no record
              is to be get out of the iterator.  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.  It is possible to access every record by
              iteration of calling this function.  However, it is not assured
              if updating the database is occurred while the iteration.
              Besides, the order of this traversal access method is arbitrary,
              so it is not assured that the order of storing matches the one
              of the traversal access.

       The function `dpsetalign' is used in order to set alignment of a
       database handle.

       int dpsetalign(DEPOT *depot, int align);
              `depot' specifies a database handle connected as a writer.
              `align' specifies the size of alignment.  If successful, the
              return value is true, else, it is false.  If alignment is set to
              a database, the efficiency of overwriting values is improved.
              The size of alignment is suggested to be average size of the
              values of the records to be stored.  If alignment is positive,
              padding whose size is multiple number of the alignment is
              placed.  If alignment is negative, as `vsiz' is the size of a
              value, the size of padding is calculated with `(vsiz / pow(2,
              abs(align) - 1))'.  Because alignment setting is not saved in a
              database, you should specify alignment every opening a database.

       The function `dpsetfbpsiz' is used in order to set the size of the free
       block pool of a database handle.

       int dpsetfbpsiz(DEPOT *depot, int size);
              `depot' 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 16.  If the size is
              greater, the space efficiency of overwriting values is improved
              with the time efficiency sacrificed.

       The function `dpsync' is used in order to synchronize updating contents
       with the file and the device.

       int dpsync(DEPOT *depot);
              `depot' 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.

       The function `dpoptimize' is used in order to optimize a database.

       int dpoptimize(DEPOT *depot, int bnum);
              `depot' specifies a database handle connected as a writer.
              `bnum' specifies the number of the elements of the bucket array.
              If it is not more than 0, the default value is specified.  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.

       The function `dpname' is used in order to get the name of a database.

       char *dpname(DEPOT *depot);
              `depot' 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 `dpfsiz' is used in order to get the size of a database
       file.

       int dpfsiz(DEPOT *depot);
              `depot' specifies a database handle.  If successful, the return
              value is the size of the database file, else, it is -1.

       The function `dpbnum' is used in order to get the number of the
       elements of the bucket array.

       int dpbnum(DEPOT *depot);
              `depot' specifies a database handle.  If successful, the return
              value is the number of the elements of the bucket array, else,
              it is -1.

       The function `dpbusenum' is used in order to get the number of the used
       elements of the bucket array.

       int dpbusenum(DEPOT *depot);
              `depot' specifies a database handle.  If successful, the return
              value is the number of the used elements of the bucket array,
              else, it is -1.  This function is inefficient because it
              accesses all elements of the bucket array.

       The function `dprnum' is used in order to get the number of the records
       stored in a database.

       int dprnum(DEPOT *depot);
              `depot' 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 `dpwritable' is used in order to check whether a database
       handle is a writer or not.

       int dpwritable(DEPOT *depot);
              `depot' specifies a database handle.  The return value is true
              if the handle is a writer, false if not.

       The function `dpfatalerror' is used in order to check whether a
       database has a fatal error or not.

       int dpfatalerror(DEPOT *depot);
              `depot' specifies a database handle.  The return value is true
              if the database has a fatal error, false if not.

       The function `dpinode' is used in order to get the inode number of a
       database file.

       int dpinode(DEPOT *depot);
              `depot' specifies a database handle.  The return value is the
              inode number of the database file.

       The function `dpmtime' is used in order to get the last modified time
       of a database.

       time_t dpmtime(DEPOT *depot);
              `depot' specifies a database handle.  The return value is the
              last modified time of the database.

       The function `dpfdesc' is used in order to get the file descriptor of a
       database file.

       int dpfdesc(DEPOT *depot);
              `depot' specifies a database handle.  The return value is the
              file descriptor of the database file.  Handling the file
              descriptor of a database file directly is not suggested.

       The function `dpremove' is used in order to remove a database file.

       int dpremove(const char *name);
              `name' specifies the name of a database file.  If successful,
              the return value is true, else, it is false.

       The function `dprepair' is used in order to repair a broken database
       file.

       int dprepair(const char *name);
              `name' specifies the name of a 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 `dpexportdb' is used in order to dump all records as
       endian independent data.

       int dpexportdb(DEPOT *depot, const char *name);
              `depot' 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 `dpimportdb' is used in order to load all records from
       endian independent data.

       int dpimportdb(DEPOT *depot, const char *name);
              `depot' 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.

       The function `dpsnaffle' is used in order to retrieve a record directly
       from a database file.

       char *dpsnaffle(const char *name, const char *kbuf, int ksiz, int *sp);
              `name' specifies the name of a database file.  `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.  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.  Although this function can be
              used even while the database file is locked by another process,
              it is not assured that recent updated is reflected.

       The function `dpinnerhash' is a hash function used inside Depot.

       int dpinnerhash(const char *kbuf, int ksiz);
              `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 hash value of 31 bits length computed from the key.  This
              function is useful when an application calculates the state of
              the inside bucket array.

       The function `dpouterhash' is a hash function which is independent from
       the hash functions used inside Depot.

       int dpouterhash(const char *kbuf, int ksiz);
              `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 hash value of 31 bits length computed from the key.  This
              function is useful when an application uses its own hash
              algorithm outside Depot.

       The function `dpprimenum' is used in order to get a natural prime
       number not less than a number.

       int dpprimenum(int num);
              `num' specified a natural number.  The return value is a natural
              prime number not less than the specified number.  This function
              is useful when an application determines the size of a bucket
              array of its own hash algorithm.

       If QDBM was built with POSIX thread enabled, the global variable
       `dpecode' is treated as thread specific data, and functions of Depot
       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.


SEE ALSO
       qdbm(3), curia(3), relic(3), hovel(3), cabin(3), villa(3), odeum(3),
       ndbm(3), gdbm(3)



Man Page                          2004-04-22                          DEPOT(3)
