From 0e4ee106c2a3cae0c6986bc54d18ffffd7c6d7e5 Mon Sep 17 00:00:00 2001 From: Ulrich Drepper Date: Fri, 28 Apr 2000 03:27:50 +0000 Subject: Update. 2000-04-25 Jes Sorensen * 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 * 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 . --- manual/string.texi | 136 ++++++++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 118 insertions(+), 18 deletions(-) (limited to 'manual/string.texi') diff --git a/manual/string.texi b/manual/string.texi index 4657ed4da1..ebf3713378 100644 --- a/manual/string.texi +++ b/manual/string.texi @@ -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 -- cgit 1.4.1