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authorSergey Poznyakoff <gray@gnu.org>2021-03-21 13:34:16 +0200
committerSergey Poznyakoff <gray@gnu.org>2021-03-21 13:52:49 +0200
commitd3e279579685be6732b3f7980f0b6a66f7e2d394 (patch)
tree41bc61c15b5b70c6cdda1467ab9a66fe0b8e4d8d /doc
parent35d78dd3c6f96904175a8d152828e4616e7fe6c7 (diff)
downloadgdbm-newcache.tar.gz
gdbm-newcache.tar.bz2
Enable automatic cache size by default.newcache
This provides for the optimal performance. Additional GDBM_XVERIFY flag can be used when opening the database to request extended database verification (entire avail stack will be checked). * src/bucket.c (cache_lookup): Handle cache_size == GDBM_CACHE_AUTO. (_gdbm_cache_init): Likewise. * src/gdbm.h.in (GDBM_XVERIFY): New flag to gdbm_open. (GDBM_CACHE_AUTO): New constant. Define error constants within enum. Fix definition of GDBM_BAD_HASH_ENTRY. * src/gdbmclose.c: Fix misleading comment. * src/gdbmconst.h: Define DEFAULT_CACHESIZE to be GDBM_CACHE_AUTO. * src/gdbmopen.c (gdbm_fd_open): Call gdbm_avail_verify if the GDBM_XVERIFY flag is set. * doc/gdbm.texi: Update. * doc/gdbm.3: Update.
Diffstat (limited to 'doc')
-rw-r--r--doc/gdbm.340
-rw-r--r--doc/gdbm.texi462
2 files changed, 323 insertions, 179 deletions
diff --git a/doc/gdbm.3 b/doc/gdbm.3
index 6525112..cfef634 100644
--- a/doc/gdbm.3
+++ b/doc/gdbm.3
@@ -13,7 +13,7 @@
.\"
.\" You should have received a copy of the GNU General Public License
.\" along with GDBM. If not, see <http://www.gnu.org/licenses/>. */
-.TH GDBM 3 "January 27, 2020" "GDBM" "GDBM User Reference"
+.TH GDBM 3 "March 21, 2021" "GDBM" "GDBM User Reference"
.SH NAME
GDBM \- The GNU database manager. Includes \fBdbm\fR and \fBndbm\fR
compatibility.
@@ -33,28 +33,35 @@ compatibility.
.br
.BI "int gdbm_close (GDBM_FILE " dbf ");"
.br
-.BI "int gdbm_store (GDBM_FILE " dbf ", datum " key ", datum " content ", int " flag );
+.BI "int gdbm_store (GDBM_FILE " dbf ", datum " key ", datum " content ", int " flag ");"
.br
-.BI "datum gdbm_fetch (GDBM_FILE " dbf ", datum " key );
+.BI "datum gdbm_fetch (GDBM_FILE " dbf ", datum " key ");"
.br
-.BI "int gdbm_delete (GDBM_FILE " dbf ", datum " key );
+.BI "int gdbm_delete (GDBM_FILE " dbf ", datum " key ");"
.br
.BI "datum gdbm_firstkey (GDBM_FILE " dbf ");"
.br
-.BI "datum gdbm_nextkey (GDBM_FILE " dbf ", datum " key );
+.BI "datum gdbm_nextkey (GDBM_FILE " dbf ", datum " key ");"
+.br
+.BI "int gdbm_recover (GDBM_FILE " dbf ", gdbm_recovery *" rcvr ", int" flags ");"
.br
.BI "int gdbm_reorganize (GDBM_FILE " dbf ");"
.br
.BI "int gdbm_sync (GDBM_FILE " dbf ");"
.br
-.BI "int gdbm_exists (GDBM_FILE " dbf ", datum " key );
+.BI "int gdbm_exists (GDBM_FILE " dbf ", datum " key ");"
.br
-.BI "const char *gdbm_strerror (gdbm_error " errno );
+.BI "const char *gdbm_strerror (gdbm_error " errno ");"
.br
.BI "int gdbm_setopt (GDBM_FILE " dbf ", int " option ", int " value ", int " size );
.br
.BI "int gdbm_fdesc (GDBM_FILE " dbf );
.br
+.BI "int gdbm_count (GDBM_FILE " dbf ", gdbm_count_t *" pcount ");"
+.br
+.BI "int gdbm_bucket_count (GDBM_FILE " dbf ", size_t *" pcount ");"
+.br
+.BI "int gdbm_avail_verify (GDBM_FILE " dbf ");"
.PP
.SS DBM Compatibility routines:
.PP
@@ -161,6 +168,15 @@ Causes all database operations to be synchronized to the disk,
.TP
.B GDBM_NOLOCK
Prevents the library from performing any locking on the database file.
+.TP
+.B GDBM_CLOEXEC
+Set the close-on-exec flag on the database file descriptor.
+.TP
+.B GDBM_XVERIFY
+Enable additional consistency checks. With this flag, eventual
+corruptions of the database are discovered when opening it, instead of
+when a corrupted structure is read during normal operation. However,
+on large databases, it can slow down the opening process.
.PP
The option
.B GDBM_FAST
@@ -327,9 +343,13 @@ and \fIoption\fR specifies which option to set. The valid options are
currently:
.TP
.B GDBM_CACHESIZE
-Set the size of the internal bucket cache. This option may only be set once
-on each \fIGDBM_FILE\fR descriptor, and is set automatically to 100 upon the
-first access to the database.
+Set the size of the internal bucket cache. By default, the cache size
+is selected to provide for the optimal performance. Use this option,
+if you wish to limit the memory usage at the expense of performance.
+.sp
+Use the
+.B GDBM_CACHE_AUTO
+constant to return to the default.
.TP
.B GDBM_FASTMODE
Set \fBfast mode\fR to either on or off. This allows \fBfast mode\fR to
diff --git a/doc/gdbm.texi b/doc/gdbm.texi
index 9c679ca..5f42ced 100644
--- a/doc/gdbm.texi
+++ b/doc/gdbm.texi
@@ -68,7 +68,7 @@ Documentation License.''
@sp 1
@center Edition @value{EDITION}
@sp 1
-@center for GNU @code{dbm}, Version @value{VERSION}
+@center for GNU @command{dbm}, Version @value{VERSION}
@page
@vskip 0pt plus 1filll
@insertcopying
@@ -85,8 +85,8 @@ Documentation License.''
@node Top
@top The GNU database manager.
-GNU @code{dbm} is a library of functions implementing a hashed database
-on a disk file. This manual documents GNU @code{dbm} Version @value{VERSION}
+GNU @command{dbm} is a library of functions implementing a hashed database
+on a disk file. This manual documents GNU @command{dbm} Version @value{VERSION}
(@code{gdbm}). The software was originally written by Philip A.@:
Nelson. This document was originally written by Pierre Gaumond from
texts written by Phil.
@@ -115,7 +115,7 @@ Functions:
* Options:: Setting internal options.
* Locking:: File locking.
* Variables:: Useful global variables.
-
+* Additional functions::
* Error codes:: Error codes returned by @code{gdbm} calls.
* Compatibility:: Compatibility with UNIX dbm and ndbm.
@@ -143,8 +143,8 @@ Other topics:
@node Copying
@chapter Copying Conditions.
This library is @dfn{free}; this means that everyone is free to use
-it and free to redistribute it on a free basis. GNU @code{dbm} (@code{gdbm})
-is not in the public domain; it is copyrighted and there
+it and free to redistribute it on a free basis. GNU @command{dbm}
+(@code{gdbm}) is not in the public domain; it is copyrighted and there
are restrictions on its distribution, but these restrictions are
designed to permit everything that a good cooperating citizen would want
to do. What is not allowed is to try to prevent others from further
@@ -176,10 +176,10 @@ Public License.) A copy the GNU General Public License is included with
the distribution of @code{gdbm}.
@node Intro
-@chapter Introduction to GNU @code{dbm}.
+@chapter Introduction to GNU @command{dbm}.
-GNU @code{dbm} (@code{gdbm}) is a library of database functions that use
-extensible hashing and works similar to the standard UNIX @code{dbm}
+GNU @command{dbm} (@code{gdbm}) is a library of database functions that use
+extensible hashing and works similar to the standard UNIX @command{dbm}
functions. These routines are provided to a programmer needing to
create and manipulate a hashed database. (@code{gdbm} is @emph{NOT} a
complete database package for an end user.)
@@ -344,7 +344,7 @@ no such key
@cindex opening the database
@cindex database, opening or creating
@deftypefn {gdbm interface} GDBM_FILE gdbm_open (const char *@var{name}, int @var{block_size}, @
- int @var{flags}, int @var{mode}, void (*fatal_func)(const char *))
+ int @var{flags}, int @var{mode}, void (*@var{fatal_func})(const char *))
Initializes @code{gdbm} system. If the file has a size of zero bytes, a file
initialization procedure is performed, setting up the initial structure in the
file.
@@ -363,61 +363,91 @@ initialized. If the value is less than 512, the file system block
size is used instead. The size is adjusted so that the block can hold
exact number of directory entries, so that the effective block size
can be slightly greater than requested. However, if the
-@samp{GDBM_BSEXACT} flag is set and the size needs to be adjusted, the
-function will return with error status, setting the @samp{gdbm_errno}
-variable to @samp{GDBM_BLOCK_SIZE_ERROR}.
+@code{GDBM_BSEXACT} flag is set and the size needs to be adjusted, the
+function will return with error status, setting the @code{gdbm_errno}
+variable to @code{GDBM_BLOCK_SIZE_ERROR}.
@item flags
@kwindex GDBM_READER
@kwindex GDBM_WRITER
@kwindex GDBM_WRCREAT
@kwindex GDBM_NEWDB
-If @code{flags} is set to @samp{GDBM_READER}, the user wants to just read the
+If @code{flags} is set to @code{GDBM_READER}, the user wants to just read the
database and any call to @code{gdbm_store} or @code{gdbm_delete} will fail.
Many readers can access the database at the same time. If @code{flags} is
-set to @samp{GDBM_WRITER}, the user wants both read and write access
+set to @code{GDBM_WRITER}, the user wants both read and write access
to the database and requires exclusive access. If @code{flags} is set
-to @samp{GDBM_WRCREAT}, the user wants both read and write access to
+to @code{GDBM_WRCREAT}, the user wants both read and write access to
the database and wants it created if it does not already exist. If
-@code{flags} is set to @samp{GDBM_NEWDB}, the user want a new database
+@code{flags} is set to @code{GDBM_NEWDB}, the user want a new database
created, regardless of whether one existed, and wants read and write
access to the new database.
@kwindex GDBM_SYNC
@kwindex GDBM_NOLOCK
@kwindex GDBM_NOMMAP
-The following may also be logically or'd into the database flags:
-@samp{GDBM_SYNC}, which causes all database operations to be
-synchronized to the disk, @samp{GDBM_NOLOCK}, which prevents the library
-from performing any locking on the database file, and @samp{GDBM_NOMMAP},
-which disables the memory mapping mechanism. The option @samp{GDBM_FAST} is
-now obsolete, since @code{gdbm} defaults to no-sync mode.
+The following constants may also be logically or'd into the database
+flags:
+
+@table @code
+@kwindex GDBM_SYNC
+@item GDBM_SYNC
+Synchronize all database operations to disk immediately. This
+provides for the best database consistency at the expense of severe
+performance degradation.
+
+@kwindex GDBM_FAST
+@item GDBM_FAST
+A reverse of @code{GDBM_SYNC}. Synchronize writes only when needed.
+This is the default. The flag is provided for compatibility with
+previous versions of @command{GDBM}.
+
+@kwindex GDBM_NOLOCK
+@item GDBM_NOLOCK
+Don't lock the database file. Use this flag if you intend to do
+locking separately.
+
+@kwindex GDBM_NOMMAP
+@item GDBM_NOMMAP
+Disable memory mapping mechanism. This degrades performance.
@kwindex GDBM_BSEXACT
+@item GDBM_BSEXACT
If this flag is set and the requested @var{block_size} cannot be used
without adjustment, @code{gdbm_open} will refuse to create the
-databases. In this case it will set the @samp{gdbm_errno}
-variable to @samp{GDBM_BLOCK_SIZE_ERROR} and return @samp{NULL}.
+databases. In this case it will set the @code{gdbm_errno}
+variable to @code{GDBM_BLOCK_SIZE_ERROR} and return @code{NULL}.
@kwindex GDBM_CLOEXEC
@cindex close-on-exec
-If the host @samp{open} call
+@item GDBM_CLOEXEC
+Set the close-on-exec flag on the database file descriptor. The
+@code{libc} must support the @code{O_CLOEXEC} flag@footnote{
@ifhtml
(@uref{http://www.manpagez.com/man/2/open, open(2)})
@end ifhtml
@ifnothtml
-(@pxref{open,,,open(2),open(2) man page})
+@xref{open,,,open(2),open(2) man page}
@end ifnothtml
-supports the @samp{O_CLOEXEC} flag, the @samp{GDBM_CLOEXEC} can be
-or'd into the flags, to enable the close-on-exec flag for the
-database file descriptor.
+}
+
+@kwindex GDBM_XVERIFY
+@item GDBM_XVERIFY
+Enable additional consistency checks. With this flag, eventual
+corruptions of the database are discovered when opening it, instead of
+when a corrupted structure is read during normal operation. However,
+on large databases, it can slow down the opening process.
+
+@xref{Additional functions}.
+@end table
+
@item mode
-File mode (see
+File mode@footnote{See
@ifhtml
@uref{http://www.manpagez.com/man/2/chmod, chmod(2)},
@end ifhtml
@ifnothtml
-@ref{chmod,,change permissions of a file,chmod(2),
+@xref{chmod,,change permissions of a file,chmod(2),
chmod(2) man page},
@end ifnothtml
and
@@ -425,17 +455,17 @@ and
@uref{http://www.manpagez.com/man/2/open, open(2)}),
@end ifhtml
@ifnothtml
-@pxref{open,,open a file,open(2), open(2) man page}),
+@ref{open,,open a file,open(2), open(2) man page}.},
@end ifnothtml
-which is used if the file is created).
+which is used if the file is created.
@item fatal_func
A function for @code{gdbm} to call if it detects a fatal error. The only
-parameter of this function is a string. If the value of @samp{NULL} is
+parameter of this function is a string. If the value of @code{NULL} is
provided, @code{gdbm} will use a default function.
@end table
The return value, is the pointer needed by all other functions to
-access that @code{gdbm} file. If the return is the @samp{NULL} pointer,
+access that @code{gdbm} file. If the return is the @code{NULL} pointer,
@code{gdbm_open} was not successful. The errors can be found in
@code{gdbm_errno} variable (@pxref{Variables, gdbm_errno}). Available
error codes are discussed in @ref{Error codes}.
@@ -446,7 +476,7 @@ returned from @code{gdbm_open}.
@deftypefn {gdbm interface} GDBM_FILE gdbm_fd_open (int @var{fd},@
const char *@var{name}, int @var{block_size}, @
- int @var{flags}, int @var{mode}, void (*fatal_func)(const char *))
+ int @var{flags}, int @var{mode}, void (*@var{fatal_func})(const char *))
Alternative function for opening a GDBM database. The @var{fd}
argument is the file descriptor of the database file obtained by a
@@ -523,8 +553,8 @@ The data to be associated with the key.
@kwindex GDBM_REPLACE
@kwindex GDBM_INSERT
Defines the action to take when the key is already in the database. The value
-@samp{GDBM_REPLACE} (defined in @file{gdbm.h}) asks that the old data
-be replaced by the new @var{content}. The value @samp{GDBM_INSERT}
+@code{GDBM_REPLACE} (defined in @file{gdbm.h}) asks that the old data
+be replaced by the new @var{content}. The value @code{GDBM_INSERT}
asks that an error be returned and no action taken if the @var{key}
already exists.
@end table
@@ -538,20 +568,20 @@ database.
@item -1
The item was not stored in the database because the caller was not an
official writer or either @var{key} or @var{content} have a
-@samp{NULL} @samp{dptr} field.
+@code{NULL} @code{dptr} field.
-Both @var{key} and @var{content} must have the @samp{dptr} field be a
-non-@samp{NULL} value. Since a @samp{NULL} @samp{dptr} field is used by
+Both @var{key} and @var{content} must have the @code{dptr} field be a
+non-@code{NULL} value. Since a @code{NULL} @code{dptr} field is used by
other functions to indicate an error, it cannot be valid data.
@item +1
The item was not stored because the argument @var{flag} was
-@samp{GDBM_INSERT} and the @var{key} was already in the database.
+@code{GDBM_INSERT} and the @var{key} was already in the database.
@end table
@end deftypefn
If you store data for a @var{key} that is already in the data base,
@code{gdbm} replaces the old data with the new data if called with
-@samp{GDBM_REPLACE}. You do not get two data items for the same
+@code{GDBM_REPLACE}. You do not get two data items for the same
@code{key} and you do not get an error from @code{gdbm_store}.
The size of datum in @code{gdbm} is restricted only by the maximum
@@ -566,13 +596,13 @@ value for an object of type @code{int} (type of the @code{dsize} member of
@deftypefn {gdbm interface} datum gdbm_fetch (GDBM_FILE @var{dbf}, datum @var{key})
Looks up a given @var{key} and returns the information associated with it.
-The @samp{dptr} field in the structure that is returned points to a
+The @code{dptr} field in the structure that is returned points to a
memory block allocated by @code{malloc}. It is the caller's
responsibility to free it when no longer needed.
-If the @samp{dptr} is @samp{NULL}, inspect the value of the
+If the @code{dptr} is @code{NULL}, inspect the value of the
@code{gdbm_errno} variable (@pxref{Variables,gdbm_errno}). If it is
-@samp{GDBM_ITEM_NOT_FOUND}, no data was found. Any other value means an
+@code{GDBM_ITEM_NOT_FOUND}, no data was found. Any other value means an
error occurred. Use @code{gdbm_strerror} function to convert
@code{gdbm_errno} to a human-readable string.
@@ -606,12 +636,12 @@ You may also search for a particular key without retrieving it:
@deftypefn {gdbm interface} int gdbm_exists (GDBM_FILE @var{dbf}, datum @var{key})
Checks whether the @var{key} exists in the database @var{dbf}.
-If @var{key} is found, returns @samp{true} (@samp{1}). If it is not
-found, returns @samp{false} (@samp{0}) and sets @code{gdbm_errno} to
-@samp{GDBM_NO_ERROR} (@samp{0}).
+If @var{key} is found, returns @code{true} (@code{1}). If it is not
+found, returns @code{false} (@code{0}) and sets @code{gdbm_errno} to
+@code{GDBM_NO_ERROR} (@code{0}).
-On error, returns @samp{0} and sets @code{gdbm_errno} to a
-non-@samp{0} error code.
+On error, returns @code{0} and sets @code{gdbm_errno} to a
+non-@code{0} error code.
The parameters are:
@@ -644,8 +674,8 @@ The pointer returned by @code{gdbm_open}.
The search key.
@end table
-The function returns @samp{-1} if the item is not present or the
-requester is a reader. The return of @samp{0} marks a successful delete.
+The function returns @code{-1} if the item is not present or the
+requester is a reader. The return of @code{0} marks a successful delete.
@end deftypefn
@node Sequential
@@ -663,13 +693,13 @@ access is not @code{key} sequential, but it is guaranteed to visit every
@deftypefn {gdbm interface} datum gdbm_firstkey (GDBM_FILE @var{dbf})
Initiate sequential access to the database @var{dbf}. The returned
-value is the first key accessed in the database. If the @samp{dptr}
-field in the returned datum is @samp{NULL}, inspect the
+value is the first key accessed in the database. If the @code{dptr}
+field in the returned datum is @code{NULL}, inspect the
@code{gdbm_errno} variable (@pxref{Variables, gdbm_errno}). The value
of @code{GDBM_ITEM_NOT_FOUND} means that the database contains no
data. Other value means an error occurred.
-On success, @samp{dptr} points to a memory block obtained from
+On success, @code{dptr} points to a memory block obtained from
@code{malloc}, which holds the key value. The caller is responsible
for freeing this memory block when no longer needed.
@end deftypefn
@@ -680,13 +710,13 @@ initiated by @code{gdbm_firstkey}. The parameter @var{prev} holds the
value returned from a previous call to @code{gdbm_nextkey} or
@code{gdbm_firstkey}.
-The function returns next key from the database. If the @samp{dptr}
-field in the returned datum is @samp{NULL} inspect the
+The function returns next key from the database. If the @code{dptr}
+field in the returned datum is @code{NULL} inspect the
@code{gdbm_errno} variable (@pxref{Variables, gdbm_errno}). The value
of @code{GDBM_ITEM_NOT_FOUND} means that all keys in the database
has been visited. Any other value means an error occurred.
-Otherwise, @samp{dptr} points to a memory block obtained from
+Otherwise, @code{dptr} points to a memory block obtained from
@code{malloc}, which holds the key value. The caller is responsible
for freeing this memory block when no longer needed.
@end deftypefn
@@ -780,7 +810,7 @@ reorganization.
@cindex synchronization, database
@kwindex GDBM_SYNC
-Unless your database was opened with the @samp{GDBM_SYNC} flag,
+Unless your database was opened with the @code{GDBM_SYNC} flag,
@code{gdbm} does not wait for writes to be flushed to the disk before
continuing. This allows for faster writing of databases at the risk
of having a corrupted database if the application terminates in an
@@ -865,16 +895,16 @@ A pointer to the source database, returned by a prior call to
Name of the dump file.
@item format
-Output file format. Allowed values are: @samp{GDBM_DUMP_FMT_BINARY} to
-create a binary dump and @samp{GDBM_DUMP_FMT_ASCII} to create an ASCII
+Output file format. Allowed values are: @code{GDBM_DUMP_FMT_BINARY} to
+create a binary dump and @code{GDBM_DUMP_FMT_ASCII} to create an ASCII
dump file.
@item open_flags
-How to create the output file. If @var{flag} is @samp{GDBM_WRCREAT}
+How to create the output file. If @var{flag} is @code{GDBM_WRCREAT}
the file will be created if it does not exist. If it does exist,
the @code{gdbm_dump} will fail.
-If @var{flag} is @samp{GDBM_NEWDB}, the function will create a new
+If @var{flag} is @code{GDBM_NEWDB}, the function will create a new
output file, replacing it if it already exists.
@item mode
@@ -895,13 +925,13 @@ for a detailed discussion.
int @var{meta_mask}, @
unsigned long *@var{errline})
Loads data from the dump file @var{filename} into the database pointed
-to by @var{pdbf}. The latter can point to @samp{NULL}, in which case
+to by @var{pdbf}. The latter can point to @code{NULL}, in which case
the function will try to create a new database. If it succeeds, the
function will return, in the memory location pointed to by @var{pdbf},
a pointer to the newly created database. If the dump file carries no
information about the original database file name, the function will
-set @code{gdbm_errno} to @samp{GDBM_NO_DBNAME} and return
-@samp{-1}, indicating failure.
+set @code{gdbm_errno} to @code{GDBM_NO_DBNAME} and return
+@code{-1}, indicating failure.
The @var{flag} has the same meaning as the @var{flag} argument
to the @code{gdbm_store} function (@pxref{Store}).
@@ -943,7 +973,7 @@ Input contained some illegal data.
This error can occur only when the input file is in ASCII format. It
indicates that the data part of the record about to be read lacked
length specification. Application developers are advised to treat
-this error equally as @samp{GDBM_ILLEGAL_DATA}.
+this error equally as @code{GDBM_ILLEGAL_DATA}.
@end table
Mild errors mean that the function was able to successfully load and
@@ -964,10 +994,10 @@ The function was unable to restore database file mode (permission bits).
If an error occurs while loading data from an input file in ASCII
format, the number of line in which the error occurred will be stored
in the location pointed to by the @var{errline} parameter, unless it
-is @samp{NULL}.
+is @code{NULL}.
If the line information is not available or applicable, @var{errline}
-will be set to @samp{0}.
+will be set to @code{0}.
@end deftypefn
@deftypefn {gdbm interface} int gdbm_dump_to_file (GDBM_FILE @var{dbf}, @
@@ -1090,6 +1120,10 @@ code. The following are the ones that have:
@item GDBM_FILE_READ_ERROR
@item GDBM_FILE_STAT_ERROR
@item GDBM_BACKUP_FAILED
+@item GDBM_BACKUP_FAILED
+@item GDBM_FILE_CLOSE_ERROR
+@item GDBM_FILE_SYNC_ERROR
+@item GDBM_FILE_TRUNCATE_ERROR
@end itemize
For other errors, @code{gdbm_last_syserr} will return 0.
@@ -1097,7 +1131,7 @@ For other errors, @code{gdbm_last_syserr} will return 0.
@anchor{gdbm_check_syserr}
@deftypefn {gdbm interface} {int} gdbm_check_syserr (gdbm_errno @var{err})
-Returns @code{1}, if system errno value should be checked to get more
+Returns @code{1}, if system @code{errno} value should be checked to get more
info on the error described by GDBM code @var{err}.
@end deftypefn
@@ -1108,7 +1142,7 @@ particular database file, use the @code{gdbm_db_strerror} function:
Returns textual description of the most recent error encountered when
operating on the database @var{dbf}. The resulting string is often
more informative than what would be returned by
-@samp{gdbm_strerror(gdbm_last_errno(@var{dbf}))}. In particular, if
+@code{gdbm_strerror(gdbm_last_errno(@var{dbf}))}. In particular, if
there is a system error associated with the recent failure, it will be
described as well.
@end deftypefn
@@ -1291,7 +1325,7 @@ place the option value (depending on the option).
The length of the data pointed to by @var{value}.
@end table
-The return value will be @samp{-1} upon failure, or @samp{0} upon
+The return value will be @code{-1} upon failure, or @code{0} upon
success. The global variable @code{gdbm_errno} will be set upon failure.
@end deftypefn
@@ -1302,23 +1336,33 @@ The valid options are:
@kwindex GDBM_SETCACHESIZE
@item GDBM_SETCACHESIZE
@itemx GDBM_CACHESIZE
-Set the size of the internal bucket cache. This option may only be
-set once on each GDBM_FILE descriptor, and is set automatically to 100
-upon the first access to the database. The @var{value} should point
-to a @code{size_t} holding the desired cache size.
+@kwindex GDBM_CACHE_AUTO
+Set the size of the internal bucket cache. The @var{value} should
+point to a @code{size_t} holding the desired cache size, or the
+constant @code{GDBM_CACHE_AUTO}, to set the best cache size
+automatically.
+
+By default, a newly open database is configured to adapt the cache
+size to the number of index buckets in the database file. This
+provides for the best performance.
+
+Use this option if you wish to limit the memory usage at the expense
+of performance. If you chose to do so, please bear in mind that cache
+becomes effective when its size is greater then 2/3 of the number of
+index bucket counts in the database. The best performance results are
+achieved when cache size equals the number of buckets. For example:
-The @samp{GDBM_CACHESIZE} option is provided for compatibility with
-earlier versions.
+@example
+size_t bn;
+gdbm_bucket_count (dbf, &bn);
+ret = gdbm_setopt (dbf, GDBM_SETCACHESIZE, &bn, sizeof (bn));
+@end example
-For instance, to set a database to use a cache of 10, after opening it
-with @code{gdbm_open}, but prior to accessing it in any way, the following
-code could be used:
+To set the best cache size, use the constant @code{GDBM_CACHE_AUTO}:
@example
-@group
-int value = 10;
-ret = gdbm_setopt (dbf, GDBM_SETCACHESIZE, &value, sizeof (int));
-@end group
+size_t bn = GDBM_CACHE_AUTO;
+ret = gdbm_setopt (dbf, GDBM_SETCACHESIZE, &bn, sizeof (bn));
@end example
@kwindex GDBM_GETCACHESIZE
@@ -1338,7 +1382,7 @@ its value will be similar to the flags used when opening the database
@item GDBM_FASTMODE
Enable or disable the @dfn{fast writes mode}, i.e.@: writes without
subsequent synchronization. The @var{value} should point
-to an integer: @samp{TRUE} to enable fast mode, and @samp{FALSE} to
+to an integer: @code{TRUE} to enable fast mode, and @code{FALSE} to
disable it.
This option is retained for compatibility with previous versions of
@@ -1351,14 +1395,14 @@ This option is retained for compatibility with previous versions of
@itemx GDBM_SYNCMODE
Turn on or off file system synchronization operations. This
setting defaults to off. The @var{value} should point
-to an integer: @samp{TRUE} to turn synchronization on, and @samp{FALSE} to
+to an integer: @code{TRUE} to turn synchronization on, and @code{FALSE} to
turn it off.
Note, that this option is a reverse of @code{GDBM_FASTMODE},
-i.e.@: calling @code{GDBM_SETSYNCMODE} with @samp{TRUE} has the same effect
-as calling @code{GDBM_FASTMODE} with @samp{FALSE}.
+i.e.@: calling @code{GDBM_SETSYNCMODE} with @code{TRUE} has the same effect
+as calling @code{GDBM_FASTMODE} with @code{FALSE}.
-The @samp{GDBM_SYNCMODE} option is provided for compatibility with
+The @code{GDBM_SYNCMODE} option is provided for compatibility with
earlier versions.
@kwindex GDBM_GETSYNCMODE
@@ -1376,10 +1420,10 @@ Set central free block pool to either on or off. The default is off,
which is how previous versions of @code{gdbm} handled free blocks. If
set, this option causes all subsequent free blocks to be placed in the
@emph{global} pool, allowing (in theory) more file space to be reused
-more quickly. The @var{value} should point to an integer: @samp{TRUE} to
-turn central block pool on, and @samp{FALSE} to turn it off.
+more quickly. The @var{value} should point to an integer: @code{TRUE} to
+turn central block pool on, and @code{FALSE} to turn it off.
-The @samp{GDBM_CENTFREE} option is provided for compatibility with
+The @code{GDBM_CENTFREE} option is provided for compatibility with
earlier versions.
@kwindex GDBM_SETCOALESCEBLKS
@@ -1393,7 +1437,7 @@ is how previous versions of @code{gdbm} handled free blocks. If set,
this option causes adjacent free blocks to be merged. This can become
a @acronym{CPU} expensive process with time, though, especially if
used in conjunction with GDBM_CENTFREE. The @var{value} should point
-to an integer: @samp{TRUE} to turn free block merging on, and @samp{FALSE} to
+to an integer: @code{TRUE} to turn free block merging on, and @code{FALSE} to
turn it off.
@kwindex GDBM_GETCOALESCEBLKS
@@ -1417,7 +1461,7 @@ point to a value of type @code{size_t} where to return the data.
@kwindex GDBM_SETMMAP
@item GDBM_SETMMAP
Enable or disable memory mapping mode. The @var{value} should point
-to an integer: @samp{TRUE} to enable memory mapping or @samp{FALSE} to
+to an integer: @code{TRUE} to enable memory mapping or @code{FALSE} to
disable it.
@kwindex GDBM_GETMMAP
@@ -1459,7 +1503,7 @@ Return the block size in bytes. The @var{value} should point to @code{int}.
@cindex locking
@kwindex GDBM_NOLOCK
-With locking disabled (if @code{gdbm_open} was called with @samp{GDBM_NOLOCK}),
+With locking disabled (if @code{gdbm_open} was called with @code{GDBM_NOLOCK}),
the user may want to perform their own file locking on the database file
in order to prevent multiple writers operating on the same file
simultaneously.
@@ -1548,8 +1592,8 @@ To compare two split-out version numbers, use the following function:
@deftypefn {gdbm interface} int gdbm_version_cmp (int const @var{a}[3], @
int const @var{b}[3])
-Compare two version numbers. Return @samp{-1} if @var{a} is less than
-@var{b}, @samp{1} if @var{a} is greater than @var{b} and @samp{0} if
+Compare two version numbers. Return @code{-1} if @var{a} is less than
+@var{b}, @code{1} if @var{a} is greater than @var{b} and @code{0} if
they are equal.
Comparison is done from left to right, so that:
@@ -1569,6 +1613,16 @@ gdbm_version_cmp (a, b) @result{} -1
@end example
@end deftypefn
+@node Additional functions
+@chapter Additional functions
+
+@deftypefn {gdbm interface} int gdbm_avail_verify (GDBM_FILE @var{dbf})
+Verify if the available block stack is in consistent state. On
+success, returns 0. If any errors are encountered, sets the
+@code{gdbm_errno} to @code{GDBM_BAD_AVAIL}, marks the database as
+needing recovery (@pxref{Recovery}) and return -1.
+@end deftypefn
+
@node Error codes
@chapter Error codes
@cindex error codes
@@ -1590,7 +1644,7 @@ Memory allocation failed. Not enough memory.
@item GDBM_BLOCK_SIZE_ERROR
This error is set by the @code{gdbm_open} function (@pxref{Open}), if
the value of its @var{block_size} argument is incorrect and the
-@samp{GDBM_BSEXACT} flag is set.
+@code{GDBM_BSEXACT} flag is set.
@kwindex GDBM_FILE_OPEN_ERROR
@item GDBM_FILE_OPEN_ERROR
@@ -1640,7 +1694,7 @@ The file given as argument to @code{gdbm_open} function is not a valid
@kwindex GDBM_CANT_BE_READER
@item GDBM_CANT_BE_READER
This error code is set by the @code{gdbm_open} function if it is not
-able to lock file when called in @samp{GDBM_READER} mode (@pxref{Open,
+able to lock file when called in @code{GDBM_READER} mode (@pxref{Open,
GDBM_READER}).
@kwindex GDBM_CANT_BE_WRITER
@@ -1681,7 +1735,7 @@ able to create a temporary database. @xref{Reorganization}.
@item GDBM_CANNOT_REPLACE
Cannot replace existing item. This error is set by the
@code{gdbm_store} if the requested @var{key} value is found in the
-database and the @var{flag} parameter is not @samp{GDBM_REPLACE}.
+database and the @var{flag} parameter is not @code{GDBM_REPLACE}.
@xref{Store}, for a detailed discussion.
@kwindex GDBM_ILLEGAL_DATA
@@ -1691,9 +1745,10 @@ to @code{gdbm_store} (@pxref{Store}).
@kwindex GDBM_OPT_ALREADY_SET
@item GDBM_OPT_ALREADY_SET
-Requested option can be set only once and was already set. This error
-is returned by the @code{gdbm_setopt} function. @xref{Options,
-GDBM_CACHESIZE}.
+Requested option can be set only once and was already set. As of
+version @value{VERSION}, this error code is no longer used. In prior
+versions it could have been returned by the @code{gdbm_setopt}
+function when setting the @code{GDBM_CACHESIZE} value.
@kwindex GDBM_OPT_ILLEGAL
@item GDBM_OPT_ILLEGAL
@@ -1740,7 +1795,7 @@ these functions are: @code{gdbm_delete}, @code{gdbm_exists},
@item GDBM_NO_DBNAME
Output database name is not specified. This error code is set by
@code{gdbm_load} (@pxref{gdbm_load function,,gdbm_load}) if the first
-argument points to @samp{NULL} and the input file does not specify the
+argument points to @code{NULL} and the input file does not specify the
database name.
@kwindex GDBM_ERR_FILE_OWNER
@@ -1773,14 +1828,83 @@ The GDBM engine is unable to create backup copy of the file.
@item GDBM_DIR_OVERFLOW
Bucket directory would overflow the size limit during an attempt to split
hash bucket. This error can occur while storing a new key.
+
+@kwindex GDBM_BAD_BUCKET
+@item GDBM_BAD_BUCKET
+Invalid index bucket is encountered in the database. Database
+recovery is needed (@pxref{Recovery}).
+
+@kwindex GDBM_BAD_HEADER
+@item GDBM_BAD_HEADER
+This error is set by @code{gdbm_open} and @code{gdbm_fd_open}, if the
+first block read from the database file does not contain a valid GDBM
+header.
+
+@kwindex GDBM_BAD_AVAIL
+@item GDBM_BAD_AVAIL
+The available space stack is invalid. This error can be set by
+@code{gdbm_open} and @code{gdbm_fd_open}, if the extended database
+verification was requested (@code{GDBM_XVERIFY}). It is also set
+by the @code{gdbm_avail_verify} function (@pxref{Additional
+functions}).
+
+Database recovery is needed (@pxref{Recovery}).
+
+@kwindex GDBM_BAD_HASH_TABLE
+@item GDBM_BAD_HASH_TABLE
+Hash table in a bucket is invalid. This error can be set by the
+following functions: @code{gdbm_delete}, @code{gdbm_exists},
+@code{gdbm_fetch}, @code{gdbm_firstkey}, @code{gdbm_nextkey}, and
+@code{gdbm_store}.
+
+Database recovery is needed (@pxref{Recovery}).
+
+@kwindex GDBM_BAD_DIR_ENTRY
+@item GDBM_BAD_DIR_ENTRY
+Bad directory entry found in the bucket. The database recovery is
+needed (@pxref{Recovery}).
+
+@kwindex GDBM_FILE_CLOSE_ERROR
+@item GDBM_FILE_CLOSE_ERROR
+The @code{gdbm_close} function was unable to close the database file
+descriptor. The system @code{errno} variable contains the
+corresponding error code.
+
+@kwindex GDBM_FILE_SYNC_ERROR
+@item GDBM_FILE_SYNC_ERROR
+Cached content couldn't be synchronized to disk. Examine the
+@code{errno} variable to get more info,
+
+Database recovery is needed (@pxref{Recovery}).
+
+@kwindex GDBM_FILE_TRUNCATE_ERROR
+@item GDBM_FILE_TRUNCATE_ERROR
+File cannot be truncated. Examine the @code{errno} variable to get
+more info,
+
+This error is set by @code{gdbm_open} and @code{gdbm_fd_open} when
+called with the @code{GDBM_NEWDB} flag.
+
+@kwindex GDBM_BUCKET_CACHE_CORRUPTED
+@item GDBM_BUCKET_CACHE_CORRUPTED
+The bucket cache structure is corrupted. Database recovery is needed
+(@pxref{Recovery}).
+
+@kwindex GDBM_BAD_HASH_ENTRY
+@kwindex GDBM_BAD_HASH_ENTRY
+This error is set during sequential access (@pxref{Sequential}), if
+the next hash table entry does not contain the expected key. This
+means that the bucket is malformed or corrupted and the database needs
+recovery (@pxref{Recovery}).
+
@end table
@node Compatibility
-@chapter Compatibility with standard @code{dbm} and @code{ndbm}.
+@chapter Compatibility with standard @command{dbm} and @command{ndbm}.
@cindex compatibility layer
-@code{Gdbm} includes a compatibility layer, which provides traditional
-@samp{ndbm} and older @samp{dbm} functions. The layer is compiled and
+@command{Gdbm} includes a compatibility layer, which provides traditional
+@command{ndbm} and older @command{dbm} functions. The layer is compiled and
installed if the @option{--enable-libgdbm-compat} option is used when
configuring the package.
@@ -1790,7 +1914,7 @@ configuring the package.
The compatibility layer consists of two header files: @file{ndbm.h}
and @file{dbm.h} and the @file{libgdbm_compat} library.
-Older programs using @code{ndbm} or @code{dbm} interfaces can
+Older programs using @command{ndbm} or @command{dbm} interfaces can
use @file{libgdbm_compat} without any changes. To link a program with
the compatibility library, add the following two options to the
@command{cc} invocation: @option{-lgdbm -lgdbm_compat}. The @option{-L}
@@ -1809,11 +1933,11 @@ consist of two different files: @file{@var{file}.dir} and
specification and corresponds to the traditional usage. Note,
however, that despite the similarity of the naming convention,
actual data stored in these files has not the same format as
-in the databases created by other @code{dbm} or @code{ndbm}
+in the databases created by other @command{dbm} or @command{ndbm}
libraries. In other words, you cannot access a standard UNIX
-@code{dbm} file with GNU @code{dbm}!
+@command{dbm} file with GNU @command{dbm}!
-GNU @code{dbm} files are not @code{sparse}. You can copy them with
+GNU @command{dbm} files are not @code{sparse}. You can copy them with
the usual @code{cp} command and they will not expand in the copying
process.
@@ -1826,7 +1950,7 @@ process.
@section NDBM interface functions.
@cindex NDBM functions
-The functions below implement the @acronym{POSIX} @samp{ndbm} interface:
+The functions below implement the @acronym{POSIX} @command{ndbm} interface:
@deftypefn {ndbm} {DBM *} dbm_open (char *@var{file}, int @var{flags}, int @var{mode})
Opens a database. The @var{file} argument is the full name of the
@@ -1848,7 +1972,7 @@ The function returns a pointer to the @code{DBM} structure describing
the database. This pointer is used to refer to this database in all
operations described below.
-Any error detected will cause a return value of @samp{NULL} and an
+Any error detected will cause a return value of @code{NULL} and an
appropriate value will be stored in @code{gdbm_errno}
(@pxref{Variables}).
@end deftypefn
@@ -1863,7 +1987,7 @@ Reads a record from the database with the matching key. The @var{key}
argument supplies the key that is being looked for.
If no matching record is found, the @code{dptr} member of the returned
-datum is @samp{NULL}. Otherwise, the @code{dptr} member of the
+datum is @code{NULL}. Otherwise, the @code{dptr} member of the
returned datum points to the memory managed by the compatibility
library. The application should never free it.
@end deftypefn
@@ -1885,7 +2009,7 @@ Replace existing record with the new one.
@kwindex DBM_INSERT
@item DBM_INSERT
The existing record is left unchanged, and the function returns
-@samp{1}.
+@code{1}.
@end table
If no matching record exists in the database, new record will be
@@ -1894,8 +2018,8 @@ inserted no matter what the value of the @var{mode} is.
@deftypefn {ndbm} int dbm_delete (DBM *@var{dbf}, datum @var{key})
Deletes the record with the matching key from the database. If the
-function succeeds, @samp{0} is returned. Otherwise, if no matching
-record is found or if an error occurs, @samp{-1} is returned.
+function succeeds, @code{0} is returned. Otherwise, if no matching
+record is found or if an error occurs, @code{-1} is returned.
@end deftypefn
@deftypefn {ndbm} datum dbm_firstkey (DBM *@var{dbf})
@@ -1904,7 +2028,7 @@ the first key. Note, that the word @samp{first} does not imply any
specific ordering of the keys.