Provided by: libqdbm-dev_1.8.78-6build3_amd64 bug

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)