mirror of
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Update.
2000-04-25 Jes Sorensen <Jes.Sorensen@cern.ch>
* shlib-versions: Rename ia64 dynamic linker to ld-linux-ia64.so.1
to avoid name clashes with the ia32 linker.
2000-04-25 Jakub Jelinek <jakub@redhat.com>
* sysdeps/alpha/dl-machine.h (_dl_start_user): Fix the _dl_skip_args
handling.
* manual/string.texi: Document strcasestr, strchrnul, strtoimax,
strtoumax, strfry, and memfrob.
* manual/arith.texi: Document {,u}int*_t types, and strto{i,u}max.
Patch by Bryan Henderson <bryanh@giraffe-data.com>.
This commit is contained in:
Ulrich Drepper
parent
3300816c38
commit
0e4ee106c2
15
ChangeLog
15
ChangeLog
@ -1,5 +1,20 @@
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2000-04-25 Jes Sorensen <Jes.Sorensen@cern.ch>
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* shlib-versions: Rename ia64 dynamic linker to ld-linux-ia64.so.1
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to avoid name clashes with the ia32 linker.
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2000-04-25 Jakub Jelinek <jakub@redhat.com>
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* sysdeps/alpha/dl-machine.h (_dl_start_user): Fix the _dl_skip_args
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handling.
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2000-04-27 Ulrich Drepper <drepper@redhat.com>
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* manual/string.texi: Document strcasestr, strchrnul, strtoimax,
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strtoumax, strfry, and memfrob.
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* manual/arith.texi: Document {,u}int*_t types, and strto{i,u}max.
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Patch by Bryan Henderson <bryanh@giraffe-data.com>.
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* elf/soinit.c (__libc_global_ctors): Call __pthread_initialize_minimal
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if this function is available.
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@ -9,6 +9,8 @@ These functions are declared in the header files @file{math.h} and
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@file{complex.h}.
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@menu
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* Integers:: Basic integer types and concepts
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* Integer Division:: Integer division with guaranteed rounding.
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* Floating Point Numbers:: Basic concepts. IEEE 754.
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* Floating Point Classes:: The five kinds of floating-point number.
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* Floating Point Errors:: When something goes wrong in a calculation.
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@ -17,11 +19,253 @@ These functions are declared in the header files @file{math.h} and
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* Arithmetic Functions:: Fundamental operations provided by the library.
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* Complex Numbers:: The types. Writing complex constants.
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* Operations on Complex:: Projection, conjugation, decomposition.
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* Integer Division:: Integer division with guaranteed rounding.
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* Parsing of Numbers:: Converting strings to numbers.
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* System V Number Conversion:: An archaic way to convert numbers to strings.
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@end menu
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@node Integers
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@section Integers
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@cindex integer
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The C language defines several integer data types: integer, short integer,
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long integer, and character, all in both signed and unsigned varieties.
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The GNU C compiler extends the language to contain long long integers
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as well.
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@cindex signedness
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The C integer types were intended to allow code to be portable among
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machines with different inherent data sizes (word sizes), so each type
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may have different ranges on different machines. The problem with
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this is that a program often needs to be written for a particular range
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of integers, and sometimes must be written for a particular size of
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storage, regardless of what machine the program runs on.
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To address this problem, the GNU C library contains C type definitions
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you can use to declare integers that meet your exact needs. Because the
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GNU C library header files are customized to a specific machine, your
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program source code doesn't have to be.
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These @code{typedef}s are in @file{stdint.h}.
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@pindex stdint.h
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If you require that an integer be represented in exactly N bits, use one
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of the following types, with the obvious mapping to bit size and signedness:
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@itemize @w
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@item int8_t
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@item int16_t
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@item int32_t
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@item int64_t
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@item uint8_t
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@item uint16_t
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@item uint32_t
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@item uint64_t
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@end itemize
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If your C compiler and target machine do not allow integers of a certain
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size, the corresponding above type does not exist.
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If you don't need a specific storage size, but want the smallest data
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structure with @emph{at least} N bits, use one of these:
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@itemize @w
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@item int8_least_t
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@item int16_least_t
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@item int32_least_t
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@item int64_least_t
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@item uint8_least_t
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@item uint16_least_t
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@item uint32_least_t
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@item uint64_least_t
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@end itemize
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If you don't need a specific storage size, but want the data structure
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that allows the fastest access while having at least N bits (and
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among data structures with the same access speed, the smallest one), use
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one of these:
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@itemize @w
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@item int8_fast_t
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@item int16_fast_t
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@item int32_fast_t
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@item int64_fast_t
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@item uint8_fast_t
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@item uint16_fast_t
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@item uint32_fast_t
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@item uint64_fast_t
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@end itemize
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If you want an integer with the widest range possible on the platform on
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which it is being used, use one of the following. If you use these,
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you should write code that takes into account the variable size and range
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of the integer.
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@itemize @w
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@item intmax_t
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@item uintmax_t
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@end itemize
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The GNU C library also provides macros that tell you the maximum and
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minimum possible values for each integer data type. The macro names
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follow these examples: @code{INT32_MAX}, @code{UINT8_MAX},
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@code{INT_FAST32_MIN}, @code{INT_LEAST64_MIN}, @code{UINTMAX_MAX},
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@code{INTMAX_MAX}, @code{INTMAX_MIN}. Note that there are no macros for
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unsigned integer minima. These are always zero.
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@cindex maximum possible integer
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@cindex mininum possible integer
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There are similar macros for use with C's built in integer types which
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should come with your C compiler. These are described in @ref{Data Type
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Measurements}.
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Don't forget you can use the C @code{sizeof} function with any of these
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data types to get the number of bytes of storage each uses.
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@node Integer Division
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@section Integer Division
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@cindex integer division functions
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This section describes functions for performing integer division. These
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functions are redundant when GNU CC is used, because in GNU C the
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@samp{/} operator always rounds towards zero. But in other C
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implementations, @samp{/} may round differently with negative arguments.
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@code{div} and @code{ldiv} are useful because they specify how to round
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the quotient: towards zero. The remainder has the same sign as the
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numerator.
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These functions are specified to return a result @var{r} such that the value
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@code{@var{r}.quot*@var{denominator} + @var{r}.rem} equals
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@var{numerator}.
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@pindex stdlib.h
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To use these facilities, you should include the header file
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@file{stdlib.h} in your program.
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@comment stdlib.h
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@comment ISO
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@deftp {Data Type} div_t
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This is a structure type used to hold the result returned by the @code{div}
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function. It has the following members:
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@table @code
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@item int quot
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The quotient from the division.
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@item int rem
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The remainder from the division.
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@end table
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@end deftp
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@comment stdlib.h
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@comment ISO
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@deftypefun div_t div (int @var{numerator}, int @var{denominator})
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This function @code{div} computes the quotient and remainder from
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the division of @var{numerator} by @var{denominator}, returning the
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result in a structure of type @code{div_t}.
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If the result cannot be represented (as in a division by zero), the
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behavior is undefined.
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Here is an example, albeit not a very useful one.
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@smallexample
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div_t result;
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result = div (20, -6);
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@end smallexample
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@noindent
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Now @code{result.quot} is @code{-3} and @code{result.rem} is @code{2}.
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@end deftypefun
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@comment stdlib.h
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@comment ISO
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@deftp {Data Type} ldiv_t
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This is a structure type used to hold the result returned by the @code{ldiv}
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function. It has the following members:
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@table @code
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@item long int quot
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The quotient from the division.
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@item long int rem
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The remainder from the division.
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@end table
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(This is identical to @code{div_t} except that the components are of
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type @code{long int} rather than @code{int}.)
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@end deftp
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@comment stdlib.h
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@comment ISO
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@deftypefun ldiv_t ldiv (long int @var{numerator}, long int @var{denominator})
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The @code{ldiv} function is similar to @code{div}, except that the
|
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arguments are of type @code{long int} and the result is returned as a
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structure of type @code{ldiv_t}.
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@end deftypefun
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@comment stdlib.h
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@comment ISO
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@deftp {Data Type} lldiv_t
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This is a structure type used to hold the result returned by the @code{lldiv}
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function. It has the following members:
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@table @code
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@item long long int quot
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The quotient from the division.
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@item long long int rem
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The remainder from the division.
|
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@end table
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(This is identical to @code{div_t} except that the components are of
|
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type @code{long long int} rather than @code{int}.)
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@end deftp
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@comment stdlib.h
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@comment ISO
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@deftypefun lldiv_t lldiv (long long int @var{numerator}, long long int @var{denominator})
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The @code{lldiv} function is like the @code{div} function, but the
|
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arguments are of type @code{long long int} and the result is returned as
|
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a structure of type @code{lldiv_t}.
|
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|
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The @code{lldiv} function was added in @w{ISO C99}.
|
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@end deftypefun
|
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|
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@comment inttypes.h
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@comment ISO
|
||||
@deftp {Data Type} imaxdiv_t
|
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This is a structure type used to hold the result returned by the @code{imaxdiv}
|
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function. It has the following members:
|
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|
||||
@table @code
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||||
@item intmax_t quot
|
||||
The quotient from the division.
|
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|
||||
@item intmax_t rem
|
||||
The remainder from the division.
|
||||
@end table
|
||||
|
||||
(This is identical to @code{div_t} except that the components are of
|
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type @code{intmax_t} rather than @code{int}.)
|
||||
|
||||
See @ref{Integers} for a description of the @code{intmax_t} type.
|
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|
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@end deftp
|
||||
|
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@comment inttypes.h
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@comment ISO
|
||||
@deftypefun imaxdiv_t imaxdiv (intmax_t @var{numerator}, intmax_t @var{denominator})
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The @code{imaxdiv} function is like the @code{div} function, but the
|
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arguments are of type @code{intmax_t} and the result is returned as
|
||||
a structure of type @code{imaxdiv_t}.
|
||||
|
||||
See @ref{Integers} for a description of the @code{intmax_t} type.
|
||||
|
||||
The @code{imaxdiv} function was added in @w{ISO C99}.
|
||||
@end deftypefun
|
||||
|
||||
|
||||
@node Floating Point Numbers
|
||||
@section Floating Point Numbers
|
||||
@cindex floating point
|
||||
@ -919,6 +1163,9 @@ the absolute value of @code{INT_MIN} (the smallest possible @code{int})
|
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cannot be represented; thus, @w{@code{abs (INT_MIN)}} is not defined.
|
||||
|
||||
@code{llabs} and @code{imaxdiv} are new to @w{ISO C99}.
|
||||
|
||||
See @ref{Integers} for a description of the @code{intmax_t} type.
|
||||
|
||||
@end deftypefun
|
||||
|
||||
@comment math.h
|
||||
@ -1784,145 +2031,6 @@ INFINITY + I * copysign (0.0, cimag (z))
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@end smallexample
|
||||
@end deftypefun
|
||||
|
||||
@node Integer Division
|
||||
@section Integer Division
|
||||
@cindex integer division functions
|
||||
|
||||
This section describes functions for performing integer division. These
|
||||
functions are redundant when GNU CC is used, because in GNU C the
|
||||
@samp{/} operator always rounds towards zero. But in other C
|
||||
implementations, @samp{/} may round differently with negative arguments.
|
||||
@code{div} and @code{ldiv} are useful because they specify how to round
|
||||
the quotient: towards zero. The remainder has the same sign as the
|
||||
numerator.
|
||||
|
||||
These functions are specified to return a result @var{r} such that the value
|
||||
@code{@var{r}.quot*@var{denominator} + @var{r}.rem} equals
|
||||
@var{numerator}.
|
||||
|
||||
@pindex stdlib.h
|
||||
To use these facilities, you should include the header file
|
||||
@file{stdlib.h} in your program.
|
||||
|
||||
@comment stdlib.h
|
||||
@comment ISO
|
||||
@deftp {Data Type} div_t
|
||||
This is a structure type used to hold the result returned by the @code{div}
|
||||
function. It has the following members:
|
||||
|
||||
@table @code
|
||||
@item int quot
|
||||
The quotient from the division.
|
||||
|
||||
@item int rem
|
||||
The remainder from the division.
|
||||
@end table
|
||||
@end deftp
|
||||
|
||||
@comment stdlib.h
|
||||
@comment ISO
|
||||
@deftypefun div_t div (int @var{numerator}, int @var{denominator})
|
||||
This function @code{div} computes the quotient and remainder from
|
||||
the division of @var{numerator} by @var{denominator}, returning the
|
||||
result in a structure of type @code{div_t}.
|
||||
|
||||
If the result cannot be represented (as in a division by zero), the
|
||||
behavior is undefined.
|
||||
|
||||
Here is an example, albeit not a very useful one.
|
||||
|
||||
@smallexample
|
||||
div_t result;
|
||||
result = div (20, -6);
|
||||
@end smallexample
|
||||
|
||||
@noindent
|
||||
Now @code{result.quot} is @code{-3} and @code{result.rem} is @code{2}.
|
||||
@end deftypefun
|
||||
|
||||
@comment stdlib.h
|
||||
@comment ISO
|
||||
@deftp {Data Type} ldiv_t
|
||||
This is a structure type used to hold the result returned by the @code{ldiv}
|
||||
function. It has the following members:
|
||||
|
||||
@table @code
|
||||
@item long int quot
|
||||
The quotient from the division.
|
||||
|
||||
@item long int rem
|
||||
The remainder from the division.
|
||||
@end table
|
||||
|
||||
(This is identical to @code{div_t} except that the components are of
|
||||
type @code{long int} rather than @code{int}.)
|
||||
@end deftp
|
||||
|
||||
@comment stdlib.h
|
||||
@comment ISO
|
||||
@deftypefun ldiv_t ldiv (long int @var{numerator}, long int @var{denominator})
|
||||
The @code{ldiv} function is similar to @code{div}, except that the
|
||||
arguments are of type @code{long int} and the result is returned as a
|
||||
structure of type @code{ldiv_t}.
|
||||
@end deftypefun
|
||||
|
||||
@comment stdlib.h
|
||||
@comment ISO
|
||||
@deftp {Data Type} lldiv_t
|
||||
This is a structure type used to hold the result returned by the @code{lldiv}
|
||||
function. It has the following members:
|
||||
|
||||
@table @code
|
||||
@item long long int quot
|
||||
The quotient from the division.
|
||||
|
||||
@item long long int rem
|
||||
The remainder from the division.
|
||||
@end table
|
||||
|
||||
(This is identical to @code{div_t} except that the components are of
|
||||
type @code{long long int} rather than @code{int}.)
|
||||
@end deftp
|
||||
|
||||
@comment stdlib.h
|
||||
@comment ISO
|
||||
@deftypefun lldiv_t lldiv (long long int @var{numerator}, long long int @var{denominator})
|
||||
The @code{lldiv} function is like the @code{div} function, but the
|
||||
arguments are of type @code{long long int} and the result is returned as
|
||||
a structure of type @code{lldiv_t}.
|
||||
|
||||
The @code{lldiv} function was added in @w{ISO C99}.
|
||||
@end deftypefun
|
||||
|
||||
@comment inttypes.h
|
||||
@comment ISO
|
||||
@deftp {Data Type} imaxdiv_t
|
||||
This is a structure type used to hold the result returned by the @code{imaxdiv}
|
||||
function. It has the following members:
|
||||
|
||||
@table @code
|
||||
@item intmax_t quot
|
||||
The quotient from the division.
|
||||
|
||||
@item intmax_t rem
|
||||
The remainder from the division.
|
||||
@end table
|
||||
|
||||
(This is identical to @code{div_t} except that the components are of
|
||||
type @code{intmax_t} rather than @code{int}.)
|
||||
@end deftp
|
||||
|
||||
@comment inttypes.h
|
||||
@comment ISO
|
||||
@deftypefun imaxdiv_t imaxdiv (intmax_t @var{numerator}, intmax_t @var{denominator})
|
||||
The @code{imaxdiv} function is like the @code{div} function, but the
|
||||
arguments are of type @code{intmax_t} and the result is returned as
|
||||
a structure of type @code{imaxdiv_t}.
|
||||
|
||||
The @code{imaxdiv} function was added in @w{ISO C99}.
|
||||
@end deftypefun
|
||||
|
||||
|
||||
@node Parsing of Numbers
|
||||
@section Parsing of Numbers
|
||||
@cindex parsing numbers (in formatted input)
|
||||
@ -2016,11 +2124,15 @@ There is an example at the end of this section.
|
||||
@comment ISO
|
||||
@deftypefun {unsigned long int} strtoul (const char *@var{string}, char **@var{tailptr}, int @var{base})
|
||||
The @code{strtoul} (``string-to-unsigned-long'') function is like
|
||||
@code{strtol} except it returns an @code{unsigned long int} value. If
|
||||
the number has a leading @samp{-} sign, the return value is negated.
|
||||
@code{strtol} except it converts to an @code{unsigned long int} value.
|
||||
The syntax is the same as described above for @code{strtol}. The value
|
||||
returned on overflow is @code{ULONG_MAX} (@pxref{Range of
|
||||
Type}).
|
||||
returned on overflow is @code{ULONG_MAX} (@pxref{Range of Type}).
|
||||
|
||||
If @var{string} depicts a negative number, @code{strtoul} acts the same
|
||||
as @var{strtol} but casts the result to an unsigned integer. That means
|
||||
for example that @code{strtoul} on @code{"-1"} returns @code{ULONG_MAX}
|
||||
and an input more negative than @code{LONG_MIN} returns
|
||||
(@code{ULONG_MAX} + 1) / 2.
|
||||
|
||||
@code{strtoul} sets @var{errno} to @code{EINVAL} if @var{base} is out of
|
||||
range, or @code{ERANGE} on overflow.
|
||||
@ -2051,9 +2163,8 @@ The @code{strtoll} function was introduced in @w{ISO C99}.
|
||||
@comment stdlib.h
|
||||
@comment ISO
|
||||
@deftypefun {unsigned long long int} strtoull (const char *@var{string}, char **@var{tailptr}, int @var{base})
|
||||
The @code{strtoull} function is like @code{strtoul} except that it
|
||||
returns an @code{unsigned long long int}. The value returned on overflow
|
||||
is @code{ULONG_LONG_MAX} (@pxref{Range of Type}).
|
||||
The @code{strtoull} function is related to @code{strtoll} the same way
|
||||
@code{strtoul} is related to @code{strtol}.
|
||||
|
||||
The @code{strtoull} function was introduced in @w{ISO C99}.
|
||||
@end deftypefun
|
||||
@ -2064,6 +2175,35 @@ The @code{strtoull} function was introduced in @w{ISO C99}.
|
||||
@code{strtouq} is the BSD name for @code{strtoull}.
|
||||
@end deftypefun
|
||||
|
||||
@comment inttypes.h
|
||||
@comment ???
|
||||
@deftypefun {long long int} strtoimax (const char *@var{string}, char **@var{tailptr}, int @var{base})
|
||||
The @code{strtoimax} function is like @code{strtol} except that it returns
|
||||
a @code{intmax_t} value, and accepts numbers of a corresponding range.
|
||||
|
||||
If the string has valid syntax for an integer but the value is not
|
||||
representable because of overflow, @code{strtoimax} returns either
|
||||
@code{INTMAX_MAX} or @code{INTMAX_MIN} (@pxref{Integers}), as
|
||||
appropriate for the sign of the value. It also sets @code{errno} to
|
||||
@code{ERANGE} to indicate there was overflow.
|
||||
|
||||
The symbols for @code{strtoimax} are declared in @file{inttypes.h}.
|
||||
|
||||
See @ref{Integers} for a description of the @code{intmax_t} type.
|
||||
|
||||
@end deftypefun
|
||||
|
||||
@comment inttypes.h
|
||||
@comment ???
|
||||
@deftypefun uintmax_t strtoumax (const char *@var{string}, char **@var{tailptr}, int @var{base})
|
||||
The @code{strtoumax} function is related to @code{strtoimax}
|
||||
the same way that @code{strtoul} is related to @code{strtol}.
|
||||
|
||||
The symbols for @code{strtoimax} are declared in @file{inttypes.h}.
|
||||
|
||||
See @ref{Integers} for a description of the @code{intmax_t} type.
|
||||
@end deftypefun
|
||||
|
||||
@comment stdlib.h
|
||||
@comment ISO
|
||||
@deftypefun {long int} atol (const char *@var{string})
|
||||
|
||||
@ -33,6 +33,8 @@ too.
|
||||
* Search Functions:: Searching for a specific element or substring.
|
||||
* Finding Tokens in a String:: Splitting a string into tokens by looking
|
||||
for delimiters.
|
||||
* strfry:: Function for flash-cooking a string.
|
||||
* Trivial Encryption:: Obscuring data.
|
||||
* Encode Binary Data:: Encoding and Decoding of Binary Data.
|
||||
* Argz and Envz Vectors:: Null-separated string vectors.
|
||||
@end menu
|
||||
@ -1092,15 +1094,14 @@ specifying a null character as the value of the @var{c} argument.
|
||||
@end deftypefun
|
||||
|
||||
@comment string.h
|
||||
@comment BSD
|
||||
@deftypefun {char *} index (const char *@var{string}, int @var{c})
|
||||
@code{index} is another name for @code{strchr}; they are exactly the same.
|
||||
New code should always use @code{strchr} since this name is defined in
|
||||
@w{ISO C} while @code{index} is a BSD invention which never was available
|
||||
on @w{System V} derived systems.
|
||||
@comment ???
|
||||
@deftypefun {char *} strchrnul (const char *@var{string}, int @var{c})
|
||||
@code{strchrnul} is the same as @code{strchr} except that if it does
|
||||
not find the character, it returns a pointer to string's terminating
|
||||
null character rather than a null pointer.
|
||||
@end deftypefun
|
||||
|
||||
One useful, but unusual, use of the @code{strchr} or @code{index}
|
||||
One useful, but unusual, use of the @code{strchr}
|
||||
function is when one wants to have a pointer pointing to the NUL byte
|
||||
terminating a string. This is often written in this way:
|
||||
|
||||
@ -1121,8 +1122,8 @@ There is no restriction on the second parameter of @code{strchr} so it
|
||||
could very well also be the NUL character. Those readers thinking very
|
||||
hard about this might now point out that the @code{strchr} function is
|
||||
more expensive than the @code{strlen} function since we have two abort
|
||||
criteria. This is right. But when using the GNU C library is used this
|
||||
@code{strchr} call gets optimized in a special way so that this version
|
||||
criteria. This is right. But in the GNU C library the implementation of
|
||||
@code{strchr} is optimized in a special way so that @code{strchr}
|
||||
actually is faster.
|
||||
|
||||
@comment string.h
|
||||
@ -1139,15 +1140,6 @@ strrchr ("hello, world", 'l')
|
||||
@end smallexample
|
||||
@end deftypefun
|
||||
|
||||
@comment string.h
|
||||
@comment BSD
|
||||
@deftypefun {char *} rindex (const char *@var{string}, int @var{c})
|
||||
@code{rindex} is another name for @code{strrchr}; they are exactly the same.
|
||||
New code should always use @code{strrchr} since this name is defined in
|
||||
@w{ISO C} while @code{rindex} is a BSD invention which never was available
|
||||
on @w{System V} derived systems.
|
||||
@end deftypefun
|
||||
|
||||
@comment string.h
|
||||
@comment ISO
|
||||
@deftypefun {char *} strstr (const char *@var{haystack}, const char *@var{needle})
|
||||
@ -1167,6 +1159,24 @@ strstr ("hello, world", "wo")
|
||||
@end deftypefun
|
||||
|
||||
|
||||
@comment string.h
|
||||
@comment ???
|
||||
@deftypefun {char *} strcasestr (const char *@var{haystack}, const char *@var{needle})
|
||||
This is like @code{strstr}, except that it ignores case in searching for
|
||||
the substring. Like @code{strcasecmp}, it is locale dependent how
|
||||
uppercase and lowercase characters are related.
|
||||
|
||||
|
||||
For example,
|
||||
@smallexample
|
||||
strstr ("hello, world", "L")
|
||||
@result{} "llo, world"
|
||||
strstr ("hello, World", "wo")
|
||||
@result{} "World"
|
||||
@end smallexample
|
||||
@end deftypefun
|
||||
|
||||
|
||||
@comment string.h
|
||||
@comment GNU
|
||||
@deftypefun {void *} memmem (const void *@var{haystack}, size_t @var{haystack-len},@*const void *@var{needle}, size_t @var{needle-len})
|
||||
@ -1228,6 +1238,27 @@ strpbrk ("hello, world", " \t\n,.;!?")
|
||||
@c @end group
|
||||
@end deftypefun
|
||||
|
||||
|
||||
@subsection Compatibility String Search Functions
|
||||
|
||||
@comment string.h
|
||||
@comment BSD
|
||||
@deftypefun {char *} index (const char *@var{string}, int @var{c})
|
||||
@code{index} is another name for @code{strchr}; they are exactly the same.
|
||||
New code should always use @code{strchr} since this name is defined in
|
||||
@w{ISO C} while @code{index} is a BSD invention which never was available
|
||||
on @w{System V} derived systems.
|
||||
@end deftypefun
|
||||
|
||||
@comment string.h
|
||||
@comment BSD
|
||||
@deftypefun {char *} rindex (const char *@var{string}, int @var{c})
|
||||
@code{rindex} is another name for @code{strrchr}; they are exactly the same.
|
||||
New code should always use @code{strrchr} since this name is defined in
|
||||
@w{ISO C} while @code{rindex} is a BSD invention which never was available
|
||||
on @w{System V} derived systems.
|
||||
@end deftypefun
|
||||
|
||||
@node Finding Tokens in a String
|
||||
@section Finding Tokens in a String
|
||||
|
||||
@ -1390,6 +1421,75 @@ token = strsep (&running, delimiters); /* token => "" */
|
||||
token = strsep (&running, delimiters); /* token => NULL */
|
||||
@end smallexample
|
||||
|
||||
|
||||
@node strfry
|
||||
@section strfry
|
||||
|
||||
The function below addresses the perennial programming quandary: ``How do
|
||||
I take good data in string form and painlessly turn it into garbage?''
|
||||
This is actually a fairly simple task for C programmers who do not use
|
||||
the GNU C library string functions, but for programs based on the GNU C
|
||||
library, the @code{strfry} function is the preferred method for
|
||||
destroying string data.
|
||||
|
||||
The prototype for this function is in @file{string.h}.
|
||||
|
||||
@comment string.h
|
||||
@comment GNU
|
||||
@deftypefun char *strfry(char *@var{string})
|
||||
|
||||
@code{strfry} creates a pseudorandom anagram of a string, replacing the
|
||||
input with the anagram in place. For each position in the string,
|
||||
@code{strfry} swaps it with a position in the string selected at random
|
||||
(from a uniform distribution). The two positions may be the same.
|
||||
|
||||
The return value of @code{strfry} is always @var{string}.
|
||||
|
||||
@strong{Portability Note:} This function is unique to the GNU C library.
|
||||
|
||||
@end deftypefun
|
||||
|
||||
|
||||
@node Trivial Encryption
|
||||
@section Trivial Encryption
|
||||
@cindex encryption
|
||||
|
||||
|
||||
The @code{memfrob} function converts an array of data to something
|
||||
unrecognizable and back again. It is not encryption in its usual sense
|
||||
since it is easy for someone to convert the encrypted data back to clear
|
||||
text. The transformation is analogous to Usenet's ``Rot13'' encryption
|
||||
method for obscuring offensive jokes from sensitive eyes and such.
|
||||
Unlike Rot13, @code{memfrob} works on arbitrary binary data, not just
|
||||
text.
|
||||
@cindex Rot13
|
||||
|
||||
For true encryption, @xref{Cryptographic Functions}.
|
||||
|
||||
This function is declared in @file{string.h}.
|
||||
@pindex string.h
|
||||
|
||||
@comment string.h
|
||||
@comment GNU
|
||||
@deftypefun {void *} memfrob (void *@var{mem}, size_t @var{length})
|
||||
|
||||
@code{memfrob} transforms (frobnicates) each byte of the data structure
|
||||
at @var{mem}, which is @var{length} bytes long, by bitwise exclusive
|
||||
oring it with binary 00101010. It does the transformation in place and
|
||||
its return value is always @var{mem}.
|
||||
|
||||
Note that @code{memfrob} a second time on the same data structure
|
||||
returns it to its original state.
|
||||
|
||||
This is a good function for hiding information from someone who doesn't
|
||||
want to see it or doesn't want to see it very much. To really prevent
|
||||
people from retrieving the information, use stronger encryption such as
|
||||
that described in @xref{Cryptographic Functions}.
|
||||
|
||||
@strong{Portability Note:} This function is unique to the GNU C library.
|
||||
|
||||
@end deftypefun
|
||||
|
||||
@node Encode Binary Data
|
||||
@section Encode Binary Data
|
||||
|
||||
|
||||
@ -54,7 +54,7 @@ sparc64-.*-linux.* ld=ld-linux.so.2
|
||||
sparc.*-.*-linux.* ld=ld-linux.so.2
|
||||
alpha.*-.*-linux.* ld=ld-linux.so.2
|
||||
arm.*-.*-linux.* ld=ld-linux.so.2
|
||||
ia64-.*-linux.* ld=ld-linux.so.2 GLIBC_2.2
|
||||
ia64-.*-linux.* ld=ld-linux-ia64.so.1 GLIBC_2.2
|
||||
mips.*-.*-linux.* ld=ld.so.1 GLIBC_2.0 GLIBC_2.2
|
||||
# We use the ELF ABI standard name for the default.
|
||||
.*-.*-.* ld=ld.so.1
|
||||
|
||||
@ -291,7 +291,7 @@ _dl_start_user:
|
||||
/* See if we were run as a command with the executable file
|
||||
name as an extra leading argument. */
|
||||
ldl $1, _dl_skip_args
|
||||
beq $1, $fixup_stack
|
||||
bne $1, $fixup_stack
|
||||
$fixup_stack_ret:
|
||||
/* The special initializer gets called with the stack just
|
||||
as the application's entry point will see it; it can
|
||||
@ -316,7 +316,7 @@ $fixup_stack:
|
||||
ldq $2, 0($sp)
|
||||
subq $2, $1, $2
|
||||
mov $sp, $4
|
||||
s8addq $2, $sp, $3
|
||||
s8addq $1, $sp, $3
|
||||
stq $2, 0($sp)
|
||||
/* Copy down argv. */
|
||||
0: ldq $5, 8($3)
|
||||
|
||||
Loading…
Reference in New Issue
Block a user