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-rw-r--r--doc/gperf.texi813
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diff --git a/doc/gperf.texi b/doc/gperf.texi
index e510ac97021f..e23f7b5329c0 100644
--- a/doc/gperf.texi
+++ b/doc/gperf.texi
@@ -7,9 +7,9 @@
@c some day we should @include version.texi instead of defining
@c these values at hand.
-@set UPDATED 26 September 2000
-@set EDITION 2.7.2
-@set VERSION 2.7.2
+@set UPDATED 31 March 2007
+@set EDITION 3.0.3
+@set VERSION 3.0.3
@c ---------------------
@c remove the black boxes generated in the GPL appendix.
@@ -28,7 +28,7 @@
This file documents the features of the GNU Perfect Hash Function
Generator @value{VERSION}.
-Copyright @copyright{} 1989-2000 Free Software Foundation, Inc.
+Copyright @copyright{} 1989-2006 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
@@ -62,10 +62,11 @@ Software Foundation instead of in the original English.
@subtitle The GNU Perfect Hash Function Generator
@subtitle Edition @value{EDITION}, @value{UPDATED}
@author Douglas C. Schmidt
+@author Bruno Haible
@page
@vskip 0pt plus 1filll
-Copyright @copyright{} 1989-2000 Free Software Foundation, Inc.
+Copyright @copyright{} 1989-2007 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of
@@ -98,13 +99,12 @@ bugs.
* Copying:: GNU @code{gperf} General Public License says
how you can copy and share @code{gperf}.
* Contributors:: People who have contributed to @code{gperf}.
-* Motivation:: Static search structures and GNU GPERF.
+* Motivation:: The purpose of @code{gperf}.
* Search Structures:: Static search structures and GNU @code{gperf}
* Description:: High-level discussion of how GPERF functions.
* Options:: A description of options to the program.
* Bugs:: Known bugs and limitations with GPERF.
* Projects:: Things still left to do.
-* Implementation:: Implementation Details for GNU GPERF.
* Bibliography:: Material Referenced in this Report.
* Concept Index::
@@ -115,13 +115,20 @@ High-Level Description of GNU @code{gperf}
* Input Format:: Input Format to @code{gperf}
* Output Format:: Output Format for Generated C Code with @code{gperf}
-* Binary Strings:: Use of NUL characters
+* Binary Strings:: Use of NUL bytes
Input Format to @code{gperf}
-* Declarations:: @code{struct} Declarations and C Code Inclusion.
+* Declarations:: Declarations.
* Keywords:: Format for Keyword Entries.
* Functions:: Including Additional C Functions.
+* Controls for GNU indent:: Where to place directives for GNU @code{indent}.
+
+Declarations
+
+* User-supplied Struct:: Specifying keywords with attributes.
+* Gperf Declarations:: Embedding command line options in the input.
+* C Code Inclusion:: Including C declarations and definitions.
Invoking @code{gperf}
@@ -147,15 +154,13 @@ Invoking @code{gperf}
@item
@cindex Bugs
The GNU @code{gperf} perfect hash function generator utility was
-originally written in GNU C++ by Douglas C. Schmidt. It is now also
-available in a highly-portable ``old-style'' C version. The general
+written in GNU C++ by Douglas C. Schmidt. The general
idea for the perfect hash function generator was inspired by Keith
Bostic's algorithm written in C, and distributed to net.sources around
1984. The current program is a heavily modified, enhanced, and extended
implementation of Keith's basic idea, created at the University of
California, Irvine. Bugs, patches, and suggestions should be reported
-to both @code{<bug-gnu-utils@@gnu.org>} and
-@code{<gperf-bugs@@lists.sourceforge.net>}.
+to @code{<bug-gnu-gperf@@gnu.org>}.
@item
Special thanks is extended to Michael Tiemann and Doug Lea, for
@@ -166,8 +171,9 @@ In addition, Adam de Boor and Nels Olson provided many tips and insights
that greatly helped improve the quality and functionality of @code{gperf}.
@item
-A testsuite was added by Bruno Haible. He also rewrote the output
-routines for better reliability.
+Bruno Haible enhanced and optimized the search algorithm. He also rewrote
+the input routines and the output routines for better reliability, and
+added a testsuite.
@end itemize
@node Motivation, Search Structures, Contributors, Top
@@ -176,8 +182,8 @@ routines for better reliability.
@code{gperf} is a perfect hash function generator written in C++. It
transforms an @var{n} element user-specified keyword set @var{W} into a
perfect hash function @var{F}. @var{F} uniquely maps keywords in
-@var{W} onto the range 0..@var{k}, where @var{k} >= @var{n}. If @var{k}
-= @var{n} then @var{F} is a @emph{minimal} perfect hash function.
+@var{W} onto the range 0..@var{k}, where @var{k} >= @var{n-1}. If @var{k}
+= @var{n-1} then @var{F} is a @emph{minimal} perfect hash function.
@code{gperf} generates a 0..@var{k} element static lookup table and a
pair of C functions. These functions determine whether a given
character string @var{s} occurs in @var{W}, using at most one probe into
@@ -185,11 +191,12 @@ the lookup table.
@code{gperf} currently generates the reserved keyword recognizer for
lexical analyzers in several production and research compilers and
-language processing tools, including GNU C, GNU C++, GNU Pascal, GNU
-Modula 3, and GNU indent. Complete C++ source code for @code{gperf} is
-available via anonymous ftp from @code{ftp://ftp.gnu.org/pub/gnu/gperf/}.
+language processing tools, including GNU C, GNU C++, GNU Java, GNU Pascal,
+GNU Modula 3, and GNU indent. Complete C++ source code for @code{gperf} is
+available from @code{http://ftp.gnu.org/pub/gnu/gperf/}.
A paper describing @code{gperf}'s design and implementation in greater
-detail is available in the Second USENIX C++ Conference proceedings.
+detail is available in the Second USENIX C++ Conference proceedings
+or from @code{http://www.cs.wustl.edu/~schmidt/resume.html}.
@node Search Structures, Description, Motivation, Top
@chapter Static search structures and GNU @code{gperf}
@@ -198,7 +205,7 @@ detail is available in the Second USENIX C++ Conference proceedings.
A @dfn{static search structure} is an Abstract Data Type with certain
fundamental operations, e.g., @emph{initialize}, @emph{insert},
and @emph{retrieve}. Conceptually, all insertions occur before any
-retrievals. In practice, @code{gperf} generates a @code{static} array
+retrievals. In practice, @code{gperf} generates a @emph{static} array
containing search set keywords and any associated attributes specified
by the user. Thus, there is essentially no execution-time cost for the
insertions. It is a useful data structure for representing @emph{static
@@ -254,8 +261,8 @@ the drudgery associated with constructing time- and space-efficient
search structures by hand. It has proven a useful and practical tool
for serious programming projects. Output from @code{gperf} is currently
used in several production and research compilers, including GNU C, GNU
-C++, GNU Pascal, and GNU Modula 3. The latter two compilers are not yet
-part of the official GNU distribution. Each compiler utilizes
+C++, GNU Java, GNU Pascal, and GNU Modula 3. The latter two compilers are
+not yet part of the official GNU distribution. Each compiler utilizes
@code{gperf} to automatically generate static search structures that
efficiently identify their respective reserved keywords.
@@ -265,11 +272,11 @@ efficiently identify their respective reserved keywords.
@menu
* Input Format:: Input Format to @code{gperf}
* Output Format:: Output Format for Generated C Code with @code{gperf}
-* Binary Strings:: Use of NUL characters
+* Binary Strings:: Use of NUL bytes
@end menu
The perfect hash function generator @code{gperf} reads a set of
-``keywords'' from a @dfn{keyfile} (or from the standard input by
+``keywords'' from an input file (or from the standard input by
default). It attempts to derive a perfect hashing function that
recognizes a member of the @dfn{static keyword set} with at most a
single probe into the lookup table. If @code{gperf} succeeds in
@@ -288,7 +295,7 @@ statement scheme that minimizes data space storage size. Furthermore,
using a C @code{switch} may actually speed up the keyword retrieval time
somewhat. Actual results depend on your C compiler, of course.
-In general, @code{gperf} assigns values to the characters it is using
+In general, @code{gperf} assigns values to the bytes it is using
for hashing until some set of values gives each keyword a unique value.
A helpful heuristic is that the larger the hash value range, the easier
it is for @code{gperf} to find and generate a perfect hash function.
@@ -300,7 +307,7 @@ Experimentation is the key to getting the most from @code{gperf}.
@cindex Declaration section
@cindex Keywords section
@cindex Functions section
-You can control the input keyfile format by varying certain command-line
+You can control the input file format by varying certain command-line
arguments, in particular the @samp{-t} option. The input's appearance
is similar to GNU utilities @code{flex} and @code{bison} (or UNIX
utilities @code{lex} and @code{yacc}). Here's an outline of the general
@@ -316,34 +323,64 @@ functions
@end group
@end example
-@emph{Unlike} @code{flex} or @code{bison}, all sections of
-@code{gperf}'s input are optional. The following sections describe the
+@emph{Unlike} @code{flex} or @code{bison}, the declarations section and
+the functions section are optional. The following sections describe the
input format for each section.
@menu
-* Declarations:: @code{struct} Declarations and C Code Inclusion.
+* Declarations:: Declarations.
* Keywords:: Format for Keyword Entries.
* Functions:: Including Additional C Functions.
+* Controls for GNU indent:: Where to place directives for GNU @code{indent}.
@end menu
+It is possible to omit the declaration section entirely, if the @samp{-t}
+option is not given. In this case the input file begins directly with the
+first keyword line, e.g.:
+
+@example
+@group
+january
+february
+march
+april
+...
+@end group
+@end example
+
@node Declarations, Keywords, Input Format, Input Format
-@subsection @code{struct} Declarations and C Code Inclusion
+@subsection Declarations
The keyword input file optionally contains a section for including
-arbitrary C declarations and definitions, as well as provisions for
-providing a user-supplied @code{struct}. If the @samp{-t} option
+arbitrary C declarations and definitions, @code{gperf} declarations that
+act like command-line options, as well as for providing a user-supplied
+@code{struct}.
+
+@menu
+* User-supplied Struct:: Specifying keywords with attributes.
+* Gperf Declarations:: Embedding command line options in the input.
+* C Code Inclusion:: Including C declarations and definitions.
+@end menu
+
+@node User-supplied Struct, Gperf Declarations, Declarations, Declarations
+@subsubsection User-supplied @code{struct}
+
+If the @samp{-t} option (or, equivalently, the @samp{%struct-type} declaration)
@emph{is} enabled, you @emph{must} provide a C @code{struct} as the last
-component in the declaration section from the keyfile file. The first
-field in this struct must be a @code{char *} or @code{const char *}
-identifier called @samp{name}, although it is possible to modify this
-field's name with the @samp{-K} option described below.
+component in the declaration section from the input file. The first
+field in this struct must be of type @code{char *} or @code{const char *}
+if the @samp{-P} option is not given, or of type @code{int} if the option
+@samp{-P} (or, equivalently, the @samp{%pic} declaration) is enabled.
+This first field must be called @samp{name}, although it is possible to modify
+its name with the @samp{-K} option (or, equivalently, the
+@samp{%define slot-name} declaration) described below.
Here is a simple example, using months of the year and their attributes as
input:
@example
@group
-struct months @{ char *name; int number; int days; int leap_days; @};
+struct month @{ char *name; int number; int days; int leap_days; @};
%%
january, 1, 31, 31
february, 2, 28, 29
@@ -366,6 +403,236 @@ other fields are a pair of consecutive percent signs, @samp{%%},
appearing left justified in the first column, as in the UNIX utility
@code{lex}.
+If the @code{struct} has already been declared in an include file, it can
+be mentioned in an abbreviated form, like this:
+
+@example
+@group
+struct month;
+%%
+january, 1, 31, 31
+...
+@end group
+@end example
+
+@node Gperf Declarations, C Code Inclusion, User-supplied Struct, Declarations
+@subsubsection Gperf Declarations
+
+The declaration section can contain @code{gperf} declarations. They
+influence the way @code{gperf} works, like command line options do.
+In fact, every such declaration is equivalent to a command line option.
+There are three forms of declarations:
+
+@enumerate
+@item
+Declarations without argument, like @samp{%compare-lengths}.
+
+@item
+Declarations with an argument, like @samp{%switch=@var{count}}.
+
+@item
+Declarations of names of entities in the output file, like
+@samp{%define lookup-function-name @var{name}}.
+@end enumerate
+
+When a declaration is given both in the input file and as a command line
+option, the command-line option's value prevails.
+
+The following @code{gperf} declarations are available.
+
+@table @samp
+@item %delimiters=@var{delimiter-list}
+@cindex @samp{%delimiters}
+Allows you to provide a string containing delimiters used to
+separate keywords from their attributes. The default is ",". This
+option is essential if you want to use keywords that have embedded
+commas or newlines.
+
+@item %struct-type
+@cindex @samp{%struct-type}
+Allows you to include a @code{struct} type declaration for generated
+code; see above for an example.
+
+@item %ignore-case
+@cindex @samp{%ignore-case}
+Consider upper and lower case ASCII characters as equivalent. The string
+comparison will use a case insignificant character comparison. Note that
+locale dependent case mappings are ignored.
+
+@item %language=@var{language-name}
+@cindex @samp{%language}
+Instructs @code{gperf} to generate code in the language specified by the
+option's argument. Languages handled are currently:
+
+@table @samp
+@item KR-C
+Old-style K&R C. This language is understood by old-style C compilers and
+ANSI C compilers, but ANSI C compilers may flag warnings (or even errors)
+because of lacking @samp{const}.
+
+@item C
+Common C. This language is understood by ANSI C compilers, and also by
+old-style C compilers, provided that you @code{#define const} to empty
+for compilers which don't know about this keyword.
+
+@item ANSI-C
+ANSI C. This language is understood by ANSI C compilers and C++ compilers.
+
+@item C++
+C++. This language is understood by C++ compilers.
+@end table
+
+The default is C.
+
+@item %define slot-name @var{name}
+@cindex @samp{%define slot-name}
+This declaration is only useful when option @samp{-t} (or, equivalently, the
+@samp{%struct-type} declaration) has been given.
+By default, the program assumes the structure component identifier for
+the keyword is @samp{name}. This option allows an arbitrary choice of
+identifier for this component, although it still must occur as the first
+field in your supplied @code{struct}.
+
+@item %define initializer-suffix @var{initializers}
+@cindex @samp{%define initializer-suffix}
+This declaration is only useful when option @samp{-t} (or, equivalently, the
+@samp{%struct-type} declaration) has been given.
+It permits to specify initializers for the structure members following
+@var{slot-name} in empty hash table entries. The list of initializers
+should start with a comma. By default, the emitted code will
+zero-initialize structure members following @var{slot-name}.
+
+@item %define hash-function-name @var{name}
+@cindex @samp{%define hash-function-name}
+Allows you to specify the name for the generated hash function. Default
+name is @samp{hash}. This option permits the use of two hash tables in
+the same file.
+
+@item %define lookup-function-name @var{name}
+@cindex @samp{%define lookup-function-name}
+Allows you to specify the name for the generated lookup function.
+Default name is @samp{in_word_set}. This option permits multiple
+generated hash functions to be used in the same application.
+
+@item %define class-name @var{name}
+@cindex @samp{%define class-name}
+This option is only useful when option @samp{-L C++} (or, equivalently,
+the @samp{%language=C++} declaration) has been given. It
+allows you to specify the name of generated C++ class. Default name is
+@code{Perfect_Hash}.
+
+@item %7bit
+@cindex @samp{%7bit}
+This option specifies that all strings that will be passed as arguments
+to the generated hash function and the generated lookup function will
+solely consist of 7-bit ASCII characters (bytes in the range 0..127).
+(Note that the ANSI C functions @code{isalnum} and @code{isgraph} do
+@emph{not} guarantee that a byte is in this range. Only an explicit
+test like @samp{c >= 'A' && c <= 'Z'} guarantees this.)
+
+@item %compare-lengths
+@cindex @samp{%compare-lengths}
+Compare keyword lengths before trying a string comparison. This option
+is mandatory for binary comparisons (@pxref{Binary Strings}). It also might
+cut down on the number of string comparisons made during the lookup, since
+keywords with different lengths are never compared via @code{strcmp}.
+However, using @samp{%compare-lengths} might greatly increase the size of the
+generated C code if the lookup table range is large (which implies that
+the switch option @samp{-S} or @samp{%switch} is not enabled), since the length
+table contains as many elements as there are entries in the lookup table.
+
+@item %compare-strncmp
+@cindex @samp{%compare-strncmp}
+Generates C code that uses the @code{strncmp} function to perform
+string comparisons. The default action is to use @code{strcmp}.
+
+@item %readonly-tables
+@cindex @samp{%readonly-tables}
+Makes the contents of all generated lookup tables constant, i.e.,
+``readonly''. Many compilers can generate more efficient code for this
+by putting the tables in readonly memory.
+
+@item %enum
+@cindex @samp{%enum}
+Define constant values using an enum local to the lookup function rather
+than with #defines. This also means that different lookup functions can
+reside in the same file. Thanks to James Clark @code{<jjc@@ai.mit.edu>}.
+
+@item %includes
+@cindex @samp{%includes}
+Include the necessary system include file, @code{<string.h>}, at the
+beginning of the code. By default, this is not done; the user must
+include this header file himself to allow compilation of the code.
+
+@item %global-table
+@cindex @samp{%global-table}
+Generate the static table of keywords as a static global variable,
+rather than hiding it inside of the lookup function (which is the
+default behavior).
+
+@item %pic
+@cindex @samp{%pic}
+Optimize the generated table for inclusion in shared libraries. This
+reduces the startup time of programs using a shared library containing
+the generated code. If the @samp{%struct-type} declaration (or,
+equivalently, the option @samp{-t}) is also given, the first field of the
+user-defined struct must be of type @samp{int}, not @samp{char *}, because
+it will contain offsets into the string pool instead of actual strings.
+To convert such an offset to a string, you can use the expression
+@samp{stringpool + @var{o}}, where @var{o} is the offset. The string pool
+name can be changed through the @samp{%define string-pool-name} declaration.
+
+@item %define string-pool-name @var{name}
+@cindex @samp{%define string-pool-name}
+Allows you to specify the name of the generated string pool created by
+the declaration @samp{%pic} (or, equivalently, the option @samp{-P}).
+The default name is @samp{stringpool}. This declaration permits the use of
+two hash tables in the same file, with @samp{%pic} and even when the
+@samp{%global-table} declaration (or, equivalently, the option @samp{-G})
+is given.
+
+@item %null-strings
+@cindex @samp{%null-strings}
+Use NULL strings instead of empty strings for empty keyword table entries.
+This reduces the startup time of programs using a shared library containing
+the generated code (but not as much as the declaration @samp{%pic}), at the
+expense of one more test-and-branch instruction at run time.
+
+@item %define word-array-name @var{name}
+@cindex @samp{%define word-array-name}
+Allows you to specify the name for the generated array containing the
+hash table. Default name is @samp{wordlist}. This option permits the
+use of two hash tables in the same file, even when the option @samp{-G}
+(or, equivalently, the @samp{%global-table} declaration) is given.
+
+@item %define length-table-name @var{name}
+@cindex @samp{%define length-table-name}
+Allows you to specify the name for the generated array containing the
+length table. Default name is @samp{lengthtable}. This option permits the
+use of two length tables in the same file, even when the option @samp{-G}
+(or, equivalently, the @samp{%global-table} declaration) is given.
+
+@item %switch=@var{count}
+@cindex @samp{%switch}
+Causes the generated C code to use a @code{switch} statement scheme,
+rather than an array lookup table. This can lead to a reduction in both
+time and space requirements for some input files. The argument to this
+option determines how many @code{switch} statements are generated. A
+value of 1 generates 1 @code{switch} containing all the elements, a
+value of 2 generates 2 tables with 1/2 the elements in each
+@code{switch}, etc. This is useful since many C compilers cannot
+correctly generate code for large @code{switch} statements. This option
+was inspired in part by Keith Bostic's original C program.
+
+@item %omit-struct-type
+@cindex @samp{%omit-struct-type}
+Prevents the transfer of the type declaration to the output file. Use
+this option if the type is already defined elsewhere.
+@end table
+
+@node C Code Inclusion, , Gperf Declarations, Declarations
+@subsubsection C Code Inclusion
+
@cindex @samp{%@{}
@cindex @samp{%@}}
Using a syntax similar to GNU utilities @code{flex} and @code{bison}, it
@@ -380,9 +647,9 @@ feature:
%@{
#include <assert.h>
/* This section of code is inserted directly into the output. */
-int return_month_days (struct months *months, int is_leap_year);
+int return_month_days (struct month *months, int is_leap_year);
%@}
-struct months @{ char *name; int number; int days; int leap_days; @};
+struct month @{ char *name; int number; int days; int leap_days; @};
%%
january, 1, 31, 31
february, 2, 28, 29
@@ -391,32 +658,21 @@ march, 3, 31, 31
@end group
@end example
-It is possible to omit the declaration section entirely. In this case
-the keyfile begins directly with the first keyword line, e.g.:
-
-@example
-@group
-january, 1, 31, 31
-february, 2, 28, 29
-march, 3, 31, 31
-april, 4, 30, 30
-...
-@end group
-@end example
-
@node Keywords, Functions, Declarations, Input Format
@subsection Format for Keyword Entries
-The second keyfile format section contains lines of keywords and any
+The second input file format section contains lines of keywords and any
associated attributes you might supply. A line beginning with @samp{#}
in the first column is considered a comment. Everything following the
-@samp{#} is ignored, up to and including the following newline.
+@samp{#} is ignored, up to and including the following newline. A line
+beginning with @samp{%} in the first column is an option declaration and
+must not occur within the keywords section.
-The first field of each non-comment line is always the key itself. It
+The first field of each non-comment line is always the keyword itself. It
can be given in two ways: as a simple name, i.e., without surrounding
string quotation marks, or as a string enclosed in double-quotes, in
C syntax, possibly with backslash escapes like @code{\"} or @code{\234}
-or @code{\xa8}. In either case, it must start right at the beginning
+or @code{\xa8}. In either case, it must start right at the beginning
of the line, without leading whitespace.
In this context, a ``field'' is considered to extend up to, but
not include, the first blank, comma, or newline. Here is a simple
@@ -445,11 +701,12 @@ Additional fields may optionally follow the leading keyword. Fields
should be separated by commas, and terminate at the end of line. What
these fields mean is entirely up to you; they are used to initialize the
elements of the user-defined @code{struct} provided by you in the
-declaration section. If the @samp{-t} option is @emph{not} enabled
+declaration section. If the @samp{-t} option (or, equivalently, the
+@samp{%struct-type} declaration) is @emph{not} enabled
these fields are simply ignored. All previous examples except the last
one contain keyword attributes.
-@node Functions, , Keywords, Input Format
+@node Functions, Controls for GNU indent, Keywords, Input Format
@subsection Including Additional C Functions
The optional third section also corresponds closely with conventions
@@ -459,12 +716,58 @@ file, is included verbatim into the generated output file. Naturally,
it is your responsibility to ensure that the code contained in this
section is valid C.
+@node Controls for GNU indent, , Functions, Input Format
+@subsection Where to place directives for GNU @code{indent}.
+
+If you want to invoke GNU @code{indent} on a @code{gperf} input file,
+you will see that GNU @code{indent} doesn't understand the @samp{%%},
+@samp{%@{} and @samp{%@}} directives that control @code{gperf}'s
+interpretation of the input file. Therefore you have to insert some
+directives for GNU @code{indent}. More precisely, assuming the most
+general input file structure
+
+@example
+@group
+declarations part 1
+%@{
+verbatim code
+%@}
+declarations part 2
+%%
+keywords
+%%
+functions
+@end group
+@end example
+
+@noindent
+you would insert @samp{*INDENT-OFF*} and @samp{*INDENT-ON*} comments
+as follows:
+
+@example
+@group
+/* *INDENT-OFF* */
+declarations part 1
+%@{
+/* *INDENT-ON* */
+verbatim code
+/* *INDENT-OFF* */
+%@}
+declarations part 2
+%%
+keywords
+%%
+/* *INDENT-ON* */
+functions
+@end group
+@end example
+
@node Output Format, Binary Strings, Input Format, Description
@section Output Format for Generated C Code with @code{gperf}
@cindex hash table
Several options control how the generated C code appears on the standard
-output. Two C function are generated. They are called @code{hash} and
+output. Two C functions are generated. They are called @code{hash} and
@code{in_word_set}, although you may modify their names with a command-line
option. Both functions require two arguments, a string, @code{char *}
@var{str}, and a length parameter, @code{int} @var{len}. Their default
@@ -472,26 +775,28 @@ function prototypes are as follows:
@deftypefun {unsigned int} hash (const char * @var{str}, unsigned int @var{len})
By default, the generated @code{hash} function returns an integer value
-created by adding @var{len} to several user-specified @var{str} key
+created by adding @var{len} to several user-specified @var{str} byte
positions indexed into an @dfn{associated values} table stored in a
local static array. The associated values table is constructed
internally by @code{gperf} and later output as a static local C array
-called @samp{hash_table}; its meaning and properties are described below
-(@pxref{Implementation}). The relevant key positions are specified via
-the @samp{-k} option when running @code{gperf}, as detailed in the
-@emph{Options} section below(@pxref{Options}).
+called @samp{hash_table}. The relevant selected positions (i.e. indices
+into @var{str}) are specified via the @samp{-k} option when running
+@code{gperf}, as detailed in the @emph{Options} section below (@pxref{Options}).
@end deftypefun
@deftypefun {} in_word_set (const char * @var{str}, unsigned int @var{len})
If @var{str} is in the keyword set, returns a pointer to that
-keyword. More exactly, if the option @samp{-t} was given, it returns
-a pointer to the matching keyword's structure. Otherwise it returns
+keyword. More exactly, if the option @samp{-t} (or, equivalently, the
+@samp{%struct-type} declaration) was given, it returns
+a pointer to the matching keyword's structure. Otherwise it returns
@code{NULL}.
@end deftypefun
-If the option @samp{-c} is not used, @var{str} must be a NUL terminated
-string of exactly length @var{len}. If @samp{-c} is used, @var{str} must
-simply be an array of @var{len} characters and does not need to be NUL
+If the option @samp{-c} (or, equivalently, the @samp{%compare-strncmp}
+declaration) is not used, @var{str} must be a NUL terminated
+string of exactly length @var{len}. If @samp{-c} (or, equivalently, the
+@samp{%compare-strncmp} declaration) is used, @var{str} must
+simply be an array of @var{len} bytes and does not need to be NUL
terminated.
The code generated for these two functions is affected by the following
@@ -512,44 +817,50 @@ degree of optimization, this method often results in smaller and faster
code.
@end table
-If the @samp{-t} and @samp{-S} options are omitted, the default action
-is to generate a @code{char *} array containing the keys, together with
-additional null strings used for padding the array. By experimenting
+If the @samp{-t} and @samp{-S} options (or, equivalently, the
+@samp{%struct-type} and @samp{%switch} declarations) are omitted, the default
+action
+is to generate a @code{char *} array containing the keywords, together with
+additional empty strings used for padding the array. By experimenting
with the various input and output options, and timing the resulting C
code, you can determine the best option choices for different keyword
set characteristics.
@node Binary Strings, , Output Format, Description
-@section Use of NUL characters
+@section Use of NUL bytes
@cindex NUL
By default, the code generated by @code{gperf} operates on zero
-terminated strings, the usual representation of strings in C. This means
-that the keywords in the input file must not contain NUL characters,
+terminated strings, the usual representation of strings in C. This means
+that the keywords in the input file must not contain NUL bytes,
and the @var{str} argument passed to @code{hash} or @code{in_word_set}
must be NUL terminated and have exactly length @var{len}.
-If option @samp{-c} is used, then the @var{str} argument does not need
-to be NUL terminated. The code generated by @code{gperf} will only
+If option @samp{-c} (or, equivalently, the @samp{%compare-strncmp}
+declaration) is used, then the @var{str} argument does not need
+to be NUL terminated. The code generated by @code{gperf} will only
access the first @var{len}, not @var{len+1}, bytes starting at @var{str}.
However, the keywords in the input file still must not contain NUL
-characters.
+bytes.
-If option @samp{-l} is used, then the hash table performs binary
-comparison. The keywords in the input file may contain NUL characters,
+If option @samp{-l} (or, equivalently, the @samp{%compare-lengths}
+declaration) is used, then the hash table performs binary
+comparison. The keywords in the input file may contain NUL bytes,
written in string syntax as @code{\000} or @code{\x00}, and the code
-generated by @code{gperf} will treat NUL like any other character.
-Also, in this case the @samp{-c} option is ignored.
+generated by @code{gperf} will treat NUL like any other byte.
+Also, in this case the @samp{-c} option (or, equivalently, the
+@samp{%compare-strncmp} declaration) is ignored.
@node Options, Bugs, Description, Top
@chapter Invoking @code{gperf}
There are @emph{many} options to @code{gperf}. They were added to make
the program more convenient for use with real applications. ``On-line''
-help is readily available via the @samp{-h} option. Here is the
+help is readily available via the @samp{--help} option. Here is the
complete list of options.
@menu
+* Output File:: Specifying the Location of the Output File
* Input Details:: Options that affect Interpretation of the Input File
* Output Language:: Specifying the Language for the Output Code
* Output Details:: Fine tuning Details in the Output Code
@@ -557,15 +868,29 @@ complete list of options.
* Verbosity:: Informative Output
@end menu
-@node Input Details, Output Language, Options, Options
+@node Output File, Input Details, Options, Options
+@section Specifying the Location of the Output File
+
+@table @samp
+@item --output-file=@var{file}
+Allows you to specify the name of the file to which the output is written to.
+@end table
+
+The results are written to standard output if no output file is specified
+or if it is @samp{-}.
+
+@node Input Details, Output Language, Output File, Options
@section Options that affect Interpretation of the Input File
+These options are also available as declarations in the input file
+(@pxref{Gperf Declarations}).
+
@table @samp
@item -e @var{keyword-delimiter-list}
@itemx --delimiters=@var{keyword-delimiter-list}
@cindex Delimiters
-Allows the user to provide a string containing delimiters used to
-separate keywords from their attributes. The default is ",\n". This
+Allows you to provide a string containing delimiters used to
+separate keywords from their attributes. The default is ",". This
option is essential if you want to use keywords that have embedded
commas or newlines. One useful trick is to use -e'TAB', where TAB is
the literal tab character.
@@ -578,11 +903,25 @@ part of the type declaration. Keywords and additional fields may follow
this, one group of fields per line. A set of examples for generating
perfect hash tables and functions for Ada, C, C++, Pascal, Modula 2,
Modula 3 and JavaScript reserved words are distributed with this release.
+
+@item --ignore-case
+Consider upper and lower case ASCII characters as equivalent. The string
+comparison will use a case insignificant character comparison. Note that
+locale dependent case mappings are ignored. This option is therefore not
+suitable if a properly internationalized or locale aware case mapping
+should be used. (For example, in a Turkish locale, the upper case equivalent
+of the lowercase ASCII letter @samp{i} is the non-ASCII character
+@samp{capital i with dot above}.) For this case, it is better to apply
+an uppercase or lowercase conversion on the string before passing it to
+the @code{gperf} generated function.
@end table
@node Output Language, Output Details, Input Details, Options
@section Options to specify the Language for the Output Code
+These options are also available as declarations in the input file
+(@pxref{Gperf Declarations}).
+
@table @samp
@item -L @var{generated-language-name}
@itemx --language=@var{generated-language-name}
@@ -591,41 +930,45 @@ option's argument. Languages handled are currently:
@table @samp
@item KR-C
-Old-style K&R C. This language is understood by old-style C compilers and
+Old-style K&R C. This language is understood by old-style C compilers and
ANSI C compilers, but ANSI C compilers may flag warnings (or even errors)
because of lacking @samp{const}.
@item C
-Common C. This language is understood by ANSI C compilers, and also by
+Common C. This language is understood by ANSI C compilers, and also by
old-style C compilers, provided that you @code{#define const} to empty
for compilers which don't know about this keyword.
@item ANSI-C
-ANSI C. This language is understood by ANSI C compilers and C++ compilers.
+ANSI C. This language is understood by ANSI C compilers and C++ compilers.
@item C++
-C++. This language is understood by C++ compilers.
+C++. This language is understood by C++ compilers.
@end table
The default is C.
@item -a
This option is supported for compatibility with previous releases of
-@code{gperf}. It does not do anything.
+@code{gperf}. It does not do anything.
@item -g
This option is supported for compatibility with previous releases of
-@code{gperf}. It does not do anything.
+@code{gperf}. It does not do anything.
@end table
@node Output Details, Algorithmic Details, Output Language, Options
@section Options for fine tuning Details in the Output Code
+Most of these options are also available as declarations in the input file
+(@pxref{Gperf Declarations}).
+
@table @samp
-@item -K @var{key-name}
-@itemx --slot-name=@var{key-name}
+@item -K @var{slot-name}
+@itemx --slot-name=@var{slot-name}
@cindex Slot name
-This option is only useful when option @samp{-t} has been given.
+This option is only useful when option @samp{-t} (or, equivalently, the
+@samp{%struct-type} declaration) has been given.
By default, the program assumes the structure component identifier for
the keyword is @samp{name}. This option allows an arbitrary choice of
identifier for this component, although it still must occur as the first
@@ -634,29 +977,30 @@ field in your supplied @code{struct}.
@item -F @var{initializers}
@itemx --initializer-suffix=@var{initializers}
@cindex Initializers
-This option is only useful when option @samp{-t} has been given.
+This option is only useful when option @samp{-t} (or, equivalently, the
+@samp{%struct-type} declaration) has been given.
It permits to specify initializers for the structure members following
-@var{key name} in empty hash table entries. The list of initializers
+@var{slot-name} in empty hash table entries. The list of initializers
should start with a comma. By default, the emitted code will
-zero-initialize structure members following @var{key name}.
+zero-initialize structure members following @var{slot-name}.
@item -H @var{hash-function-name}
-@itemx --hash-fn-name=@var{hash-function-name}
+@itemx --hash-function-name=@var{hash-function-name}
Allows you to specify the name for the generated hash function. Default
name is @samp{hash}. This option permits the use of two hash tables in
the same file.
@item -N @var{lookup-function-name}
-@itemx --lookup-fn-name=@var{lookup-function-name}
+@itemx --lookup-function-name=@var{lookup-function-name}
Allows you to specify the name for the generated lookup function.
-Default name is @samp{in_word_set}. This option permits completely
-automatic generation of perfect hash functions, especially when multiple
-generated hash functions are used in the same application.
+Default name is @samp{in_word_set}. This option permits multiple
+generated hash functions to be used in the same application.
@item -Z @var{class-name}
@itemx --class-name=@var{class-name}
@cindex Class name
-This option is only useful when option @samp{-L C++} has been given. It
+This option is only useful when option @samp{-L C++} (or, equivalently,
+the @samp{%language=C++} declaration) has been given. It
allows you to specify the name of generated C++ class. Default name is
@code{Perfect_Hash}.
@@ -664,12 +1008,23 @@ allows you to specify the name of generated C++ class. Default name is
@itemx --seven-bit
This option specifies that all strings that will be passed as arguments
to the generated hash function and the generated lookup function will
-solely consist of 7-bit ASCII characters (characters in the range 0..127).
+solely consist of 7-bit ASCII characters (bytes in the range 0..127).
(Note that the ANSI C functions @code{isalnum} and @code{isgraph} do
-@emph{not} guarantee that a character is in this range. Only an explicit
+@emph{not} guarantee that a byte is in this range. Only an explicit
test like @samp{c >= 'A' && c <= 'Z'} guarantees this.) This was the
default in versions of @code{gperf} earlier than 2.7; now the default is
-to assume 8-bit characters.
+to support 8-bit and multibyte characters.
+
+@item -l
+@itemx --compare-lengths
+Compare keyword lengths before trying a string comparison. This option
+is mandatory for binary comparisons (@pxref{Binary Strings}). It also might
+cut down on the number of string comparisons made during the lookup, since
+keywords with different lengths are never compared via @code{strcmp}.
+However, using @samp{-l} might greatly increase the size of the
+generated C code if the lookup table range is large (which implies that
+the switch option @samp{-S} or @samp{%switch} is not enabled), since the length
+table contains as many elements as there are entries in the lookup table.
@item -c
@itemx --compare-strncmp
@@ -695,30 +1050,63 @@ beginning of the code. By default, this is not done; the user must
include this header file himself to allow compilation of the code.
@item -G
-@itemx --global
+@itemx --global-table
Generate the static table of keywords as a static global variable,
rather than hiding it inside of the lookup function (which is the
default behavior).
+@item -P
+@itemx --pic
+Optimize the generated table for inclusion in shared libraries. This
+reduces the startup time of programs using a shared library containing
+the generated code. If the option @samp{-t} (or, equivalently, the
+@samp{%struct-type} declaration) is also given, the first field of the
+user-defined struct must be of type @samp{int}, not @samp{char *}, because
+it will contain offsets into the string pool instead of actual strings.
+To convert such an offset to a string, you can use the expression
+@samp{stringpool + @var{o}}, where @var{o} is the offset. The string pool
+name can be changed through the option @samp{--string-pool-name}.
+
+@item -Q @var{string-pool-name}
+@itemx --string-pool-name=@var{string-pool-name}
+Allows you to specify the name of the generated string pool created by
+option @samp{-P}. The default name is @samp{stringpool}. This option
+permits the use of two hash tables in the same file, with @samp{-P} and
+even when the option @samp{-G} (or, equivalently, the @samp{%global-table}
+declaration) is given.
+
+@item --null-strings
+Use NULL strings instead of empty strings for empty keyword table entries.
+This reduces the startup time of programs using a shared library containing
+the generated code (but not as much as option @samp{-P}), at the expense
+of one more test-and-branch instruction at run time.
+
@item -W @var{hash-table-array-name}
@itemx --word-array-name=@var{hash-table-array-name}
@cindex Array name
Allows you to specify the name for the generated array containing the
hash table. Default name is @samp{wordlist}. This option permits the
use of two hash tables in the same file, even when the option @samp{-G}
-is given.
+(or, equivalently, the @samp{%global-table} declaration) is given.
+
+@itemx --length-table-name=@var{length-table-array-name}
+@cindex Array name
+Allows you to specify the name for the generated array containing the
+length table. Default name is @samp{lengthtable}. This option permits the
+use of two length tables in the same file, even when the option @samp{-G}
+(or, equivalently, the @samp{%global-table} declaration) is given.
@item -S @var{total-switch-statements}
@itemx --switch=@var{total-switch-statements}
@cindex @code{switch}
Causes the generated C code to use a @code{switch} statement scheme,
rather than an array lookup table. This can lead to a reduction in both
-time and space requirements for some keyfiles. The argument to this
-option determines how many @code{switch} statements are generated. A
+time and space requirements for some input files. The argument to this
+option determines how many @code{switch} statements are generated. A
value of 1 generates 1 @code{switch} containing all the elements, a
value of 2 generates 2 tables with 1/2 the elements in each
@code{switch}, etc. This is useful since many C compilers cannot
-correctly generate code for large @code{switch} statements. This option
+correctly generate code for large @code{switch} statements. This option
was inspired in part by Keith Bostic's original C program.
@item -T
@@ -728,93 +1116,73 @@ this option if the type is already defined elsewhere.
@item -p
This option is supported for compatibility with previous releases of
-@code{gperf}. It does not do anything.
+@code{gperf}. It does not do anything.
@end table
@node Algorithmic Details, Verbosity, Output Details, Options
@section Options for changing the Algorithms employed by @code{gperf}
@table @samp
-@item -k @var{keys}
-@itemx --key-positions=@var{keys}
-Allows selection of the character key positions used in the keywords'
-hash function. The allowable choices range between 1-126, inclusive.
+@item -k @var{selected-byte-positions}
+@itemx --key-positions=@var{selected-byte-positions}
+Allows selection of the byte positions used in the keywords'
+hash function. The allowable choices range between 1-255, inclusive.
The positions are separated by commas, e.g., @samp{-k 9,4,13,14};
ranges may be used, e.g., @samp{-k 2-7}; and positions may occur
-in any order. Furthermore, the meta-character '*' causes the generated
-hash function to consider @strong{all} character positions in each key,
-whereas '$' instructs the hash function to use the ``final character''
-of a key (this is the only way to use a character position greater than
-126, incidentally).
+in any order. Furthermore, the wildcard '*' causes the generated
+hash function to consider @strong{all} byte positions in each keyword,
+whereas '$' instructs the hash function to use the ``final byte''
+of a keyword (this is the only way to use a byte position greater than
+255, incidentally).
For instance, the option @samp{-k 1,2,4,6-10,'$'} generates a hash
function that considers positions 1,2,4,6,7,8,9,10, plus the last
-character in each key (which may differ for each key, obviously). Keys
-with length less than the indicated key positions work properly, since
-selected key positions exceeding the key length are simply not
+byte in each keyword (which may be at a different position for each
+keyword, obviously). Keywords
+with length less than the indicated byte positions work properly, since
+selected byte positions exceeding the keyword length are simply not
referenced in the hash function.
-@item -l
-@itemx --compare-strlen
-Compare key lengths before trying a string comparison. This might cut
-down on the number of string comparisons made during the lookup, since
-keys with different lengths are never compared via @code{strcmp}.
-However, using @samp{-l} might greatly increase the size of the
-generated C code if the lookup table range is large (which implies that
-the switch option @samp{-S} is not enabled), since the length table
-contains as many elements as there are entries in the lookup table.
-This option is mandatory for binary comparisons (@pxref{Binary Strings}).
+This option is not normally needed since version 2.8 of @code{gperf};
+the default byte positions are computed depending on the keyword set,
+through a search that minimizes the number of byte positions.
@item -D
@itemx --duplicates
@cindex Duplicates
-Handle keywords whose key position sets hash to duplicate values.
-Duplicate hash values occur for two reasons:
-
-@itemize @bullet
-@item
-Since @code{gperf} does not backtrack it is possible for it to process
-all your input keywords without finding a unique mapping for each word.
-However, frequently only a very small number of duplicates occur, and
-the majority of keys still require one probe into the table.
-
-@item
-Sometimes a set of keys may have the same names, but possess different
-attributes. With the -D option @code{gperf} treats all these keys as
+Handle keywords whose selected byte sets hash to duplicate values.
+Duplicate hash values can occur if a set of keywords has the same names, but
+possesses different attributes, or if the selected byte positions are not well
+chosen. With the -D option @code{gperf} treats all these keywords as
part of an equivalence class and generates a perfect hash function with
-multiple comparisons for duplicate keys. It is up to you to completely
+multiple comparisons for duplicate keywords. It is up to you to completely
disambiguate the keywords by modifying the generated C code. However,
@code{gperf} helps you out by organizing the output.
-@end itemize
-Option @samp{-D} is extremely useful for certain large or highly
-redundant keyword sets, e.g., assembler instruction opcodes.
Using this option usually means that the generated hash function is no
longer perfect. On the other hand, it permits @code{gperf} to work on
keyword sets that it otherwise could not handle.
-@item -f @var{iteration-amount}
-@itemx --fast=@var{iteration-amount}
-Generate the perfect hash function ``fast''. This decreases
-@code{gperf}'s running time at the cost of minimizing generated
-table-size. The iteration amount represents the number of times to
-iterate when resolving a collision. `0' means iterate by the number of
-keywords. This option is probably most useful when used in conjunction
-with options @samp{-D} and/or @samp{-S} for @emph{large} keyword sets.
+@item -m @var{iterations}
+@itemx --multiple-iterations=@var{iterations}
+Perform multiple choices of the @samp{-i} and @samp{-j} values, and
+choose the best results. This increases the running time by a factor of
+@var{iterations} but does a good job minimizing the generated table size.
@item -i @var{initial-value}
@itemx --initial-asso=@var{initial-value}
Provides an initial @var{value} for the associate values array. Default
is 0. Increasing the initial value helps inflate the final table size,
possibly leading to more time efficient keyword lookups. Note that this
-option is not particularly useful when @samp{-S} is used. Also,
+option is not particularly useful when @samp{-S} (or, equivalently,
+@samp{%switch}) is used. Also,
@samp{-i} is overridden when the @samp{-r} option is used.
@item -j @var{jump-value}
@itemx --jump=@var{jump-value}
@cindex Jump value
Affects the ``jump value'', i.e., how far to advance the associated
-character value upon collisions. @var{Jump-value} is rounded up to an
+byte value upon collisions. @var{Jump-value} is rounded up to an
odd number, the default is 5. If the @var{jump-value} is 0 @code{gperf}
jumps by random amounts.
@@ -824,60 +1192,38 @@ Instructs the generator not to include the length of a keyword when
computing its hash value. This may save a few assembly instructions in
the generated lookup table.
-@item -o
-@itemx --occurrence-sort
-Reorders the keywords by sorting the keywords so that frequently
-occuring key position set components appear first. A second reordering
-pass follows so that keys with ``already determined values'' are placed
-towards the front of the keylist. This may decrease the time required
-to generate a perfect hash function for many keyword sets, and also
-produce more minimal perfect hash functions. The reason for this is
-that the reordering helps prune the search time by handling inevitable
-collisions early in the search process. On the other hand, if the
-number of keywords is @emph{very} large using @samp{-o} may
-@emph{increase} @code{gperf}'s execution time, since collisions will
-begin earlier and continue throughout the remainder of keyword
-processing. See Cichelli's paper from the January 1980 Communications
-of the ACM for details.
-
@item -r
@itemx --random
Utilizes randomness to initialize the associated values table. This
frequently generates solutions faster than using deterministic
initialization (which starts all associated values at 0). Furthermore,
using the randomization option generally increases the size of the
-table. If @code{gperf} has difficultly with a certain keyword set try using
-@samp{-r} or @samp{-D}.
+table.
@item -s @var{size-multiple}
@itemx --size-multiple=@var{size-multiple}
Affects the size of the generated hash table. The numeric argument for
this option indicates ``how many times larger or smaller'' the maximum
-associated value range should be, in relationship to the number of keys.
-If the @var{size-multiple} is negative the maximum associated value is
-calculated by @emph{dividing} it into the total number of keys. For
-example, a value of 3 means ``allow the maximum associated value to be
-about 3 times larger than the number of input keys''.
-
-Conversely, a value of -3 means ``allow the maximum associated value to
-be about 3 times smaller than the number of input keys''. Negative
-values are useful for limiting the overall size of the generated hash
-table, though this usually increases the number of duplicate hash
-values.
-
-If `generate switch' option @samp{-S} is @emph{not} enabled, the maximum
+associated value range should be, in relationship to the number of keywords.
+It can be written as an integer, a floating-point number or a fraction.
+For example, a value of 3 means ``allow the maximum associated value to be
+about 3 times larger than the number of input keywords''.
+Conversely, a value of 1/3 means ``allow the maximum associated value to
+be about 3 times smaller than the number of input keywords''. Values
+smaller than 1 are useful for limiting the overall size of the generated hash
+table, though the option @samp{-m} is better at this purpose.
+
+If `generate switch' option @samp{-S} (or, equivalently, @samp{%switch}) is
+@emph{not} enabled, the maximum
associated value influences the static array table size, and a larger
table should decrease the time required for an unsuccessful search, at
the expense of extra table space.
The default value is 1, thus the default maximum associated value about
-the same size as the number of keys (for efficiency, the maximum
+the same size as the number of keywords (for efficiency, the maximum
associated value is always rounded up to a power of 2). The actual
table size may vary somewhat, since this technique is essentially a
-heuristic. In particular, setting this value too high slows down
-@code{gperf}'s runtime, since it must search through a much larger range
-of values. Judicious use of the @samp{-f} option helps alleviate this
-overhead, however.
+heuristic.
@end table
@node Verbosity, , Algorithmic Details, Options
@@ -919,16 +1265,6 @@ work efficiently on much larger keyword sets (over 15,000 keywords).
When processing large keyword sets it helps greatly to have over 8 megs
of RAM.
-However, since @code{gperf} does not backtrack no guaranteed solution
-occurs on every run. On the other hand, it is usually easy to obtain a
-solution by varying the option parameters. In particular, try the
-@samp{-r} option, and also try changing the default arguments to the
-@samp{-s} and @samp{-j} options. To @emph{guarantee} a solution, use
-the @samp{-D} and @samp{-S} options, although the final results are not
-likely to be a @emph{perfect} hash function anymore! Finally, use the
-@samp{-f} option if you want @code{gperf} to generate the perfect hash
-function @emph{fast}, with less emphasis on making it minimal.
-
@item
The size of the generate static keyword array can get @emph{extremely}
large if the input keyword file is large or if the keywords are quite
@@ -936,19 +1272,19 @@ similar. This tends to slow down the compilation of the generated C
code, and @emph{greatly} inflates the object code size. If this
situation occurs, consider using the @samp{-S} option to reduce data
size, potentially increasing keyword recognition time a negligible
-amount. Since many C compilers cannot correctly generated code for
+amount. Since many C compilers cannot correctly generate code for
large switch statements it is important to qualify the @var{-S} option
with an appropriate numerical argument that controls the number of
switch statements generated.
@item
-The maximum number of key positions selected for a given key has an
-arbitrary limit of 126. This restriction should be removed, and if
+The maximum number of selected byte positions has an
+arbitrary limit of 255. This restriction should be removed, and if
anyone considers this a problem write me and let me know so I can remove
the constraint.
@end itemize
-@node Projects, Implementation, Bugs, Top
+@node Projects, Bibliography, Bugs, Top
@chapter Things Still Left to Do
It should be ``relatively'' easy to replace the current perfect hash
@@ -958,18 +1294,10 @@ worthwhile improvements include:
@itemize @bullet
@item
-Make the algorithm more robust. At present, the program halts with an
-error diagnostic if it can't find a direct solution and the @samp{-D}
-option is not enabled. A more comprehensive, albeit computationally
-expensive, approach would employ backtracking or enable alternative
-options and retry. It's not clear how helpful this would be, in
-general, since most search sets are rather small in practice.
-
-@item
Another useful extension involves modifying the program to generate
``minimal'' perfect hash functions (under certain circumstances, the
current version can be rather extravagant in the generated table size).
-Again, this is mostly of theoretical interest, since a sparse table
+This is mostly of theoretical interest, since a sparse table
often produces faster lookups, and use of the @samp{-S} @code{switch}
option can minimize the data size, at the expense of slightly longer
lookups (note that the gcc compiler generally produces good code for
@@ -977,42 +1305,30 @@ lookups (note that the gcc compiler generally produces good code for
@item
In addition to improving the algorithm, it would also be useful to
-generate a C++ class or Ada package as the code output, in addition to
-the current C routines.
+generate an Ada package as the code output, in addition to the current
+C and C++ routines.
@end itemize
-@node Implementation, Bibliography, Projects, Top
-@chapter Implementation Details of GNU @code{gperf}
-
-A paper describing the high-level description of the data structures and
-algorithms used to implement @code{gperf} will soon be available. This
-paper is useful not only from a maintenance and enhancement perspective,
-but also because they demonstrate several clever and useful programming
-techniques, e.g., `Iteration Number' boolean arrays, double
-hashing, a ``safe'' and efficient method for reading arbitrarily long
-input from a file, and a provably optimal algorithm for simultaneously
-determining both the minimum and maximum elements in a list.
-
@page
-@node Bibliography, Concept Index, Implementation, Top
+@node Bibliography, Concept Index, Projects, Top
@chapter Bibliography
[1] Chang, C.C.: @i{A Scheme for Constructing Ordered Minimal Perfect
Hashing Functions} Information Sciences 39(1986), 187-195.
-
+
[2] Cichelli, Richard J. @i{Author's Response to ``On Cichelli's Minimal Perfect Hash
Functions Method''} Communications of the ACM, 23, 12(December 1980), 729.
-
+
[3] Cichelli, Richard J. @i{Minimal Perfect Hash Functions Made Simple}
Communications of the ACM, 23, 1(January 1980), 17-19.
-
+
[4] Cook, C. R. and Oldehoeft, R.R. @i{A Letter Oriented Minimal
Perfect Hashing Function} SIGPLAN Notices, 17, 9(September 1982), 18-27.
[5] Cormack, G. V. and Horspool, R. N. S. and Kaiserwerth, M.
@i{Practical Perfect Hashing} Computer Journal, 28, 1(January 1985), 54-58.
-
+
[6] Jaeschke, G. @i{Reciprocal Hashing: A Method for Generating Minimal
Perfect Hashing Functions} Communications of the ACM, 24, 12(December
1981), 829-833.
@@ -1027,19 +1343,22 @@ Hash Functions} Communications of the ACM, 28, 5(December 1985), 523-532
[9] Schmidt, Douglas C. @i{GPERF: A Perfect Hash Function Generator}
Second USENIX C++ Conference Proceedings, April 1990.
-[10] Sebesta, R.W. and Taylor, M.A. @i{Minimal Perfect Hash Functions
+[10] Schmidt, Douglas C. @i{GPERF: A Perfect Hash Function Generator}
+C++ Report, SIGS 10 10 (November/December 1998).
+
+[11] Sebesta, R.W. and Taylor, M.A. @i{Minimal Perfect Hash Functions
for Reserved Word Lists} SIGPLAN Notices, 20, 12(September 1985), 47-53.
-[11] Sprugnoli, R. @i{Perfect Hashing Functions: A Single Probe
+[12] Sprugnoli, R. @i{Perfect Hashing Functions: A Single Probe
Retrieving Method for Static Sets} Communications of the ACM, 20
11(November 1977), 841-850.
-[12] Stallman, Richard M. @i{Using and Porting GNU CC} Free Software Foundation,
+[13] Stallman, Richard M. @i{Using and Porting GNU CC} Free Software Foundation,
1988.
-[13] Stroustrup, Bjarne @i{The C++ Programming Language.} Addison-Wesley, 1986.
+[14] Stroustrup, Bjarne @i{The C++ Programming Language.} Addison-Wesley, 1986.
-[14] Tiemann, Michael D. @i{User's Guide to GNU C++} Free Software
+[15] Tiemann, Michael D. @i{User's Guide to GNU C++} Free Software
Foundation, 1989.
@node Concept Index, , Bibliography, Top