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authorUlrich Drepper <drepper@redhat.com>2000-04-28 03:27:50 +0000
committerUlrich Drepper <drepper@redhat.com>2000-04-28 03:27:50 +0000
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tree25c2315cfbbb2a85fd4d95a2cde5c9229a2bd402 /manual/string.texi
parent3300816c38721bcddbbeb92de7fe44b90454bce6 (diff)
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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>.
Diffstat (limited to 'manual/string.texi')
-rw-r--r--manual/string.texi136
1 files changed, 118 insertions, 18 deletions
diff --git a/manual/string.texi b/manual/string.texi
index 4657ed4..ebf3713 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
@@ -1140,15 +1141,6 @@ strrchr ("hello, world", 'l')
@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})
This is like @code{strchr}, except that it searches @var{haystack} for a
@@ -1168,6 +1160,24 @@ strstr ("hello, world", "wo")
@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})
This is like @code{strstr}, but @var{needle} and @var{haystack} are byte
@@ -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