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       ggstrlcpy, ggstrlcat - size-bounded string copying and concatenation


       #include <ggi/gg.h>

       size_t ggstrlcpy(char *dst, const char *src, size_t siz);

       size_t ggstrlcat(char *dst, const char *src, size_t siz);


       The  ggstrlcpy  and  ggstrlcat  functions  copy and concatenate strings
       respectively.  They are designed to be safer, more consistent, and less
       error  prone  replacements for strncpy(3) and strncat(3).  Unlike those
       functions, ggstrlcpy and ggstrlcat take the full  size  of  the  buffer
       (not  just  the  length)  and guarantee to NUL-terminate the result (as
       long as size is larger than 0 or, in the case of ggstrlcat, as long  as
       there  is at least one byte free in dst).  Note that you should include
       a byte for the NUL in size.  Also note  that  ggstrlcpy  and  ggstrlcat
       only operate on true C strings.  This means that for ggstrlcpy src must
       be NUL-terminated and for ggstrlcat both  src  and  dst  must  be  NUL-

       The  ggstrlcpy  function  copies up to siz - 1 characters from the NUL-
       terminated string src to dst, NUL-terminating the result.

       The ggstrlcat function appends the NUL-terminated string src to the end
       of  dst.   It  will  append  at  most siz - strlen(dst) - 1 bytes, NUL-
       terminating the result.


       The ggstrlcpy and ggstrlcat functions return the total  length  of  the
       string  they  tried  to create.  For ggstrlcpy that means the length of
       src.  For ggstrlcat that means the  initial  length  of  dst  plus  the
       length  of  src.  While this may seem somewhat confusing it was done to
       make truncation detection simple.

       Note however, that  if  ggstrlcat  traverses  size  characters  without
       finding  a  NUL,  the length of the string is considered to be size and
       the destination string will not be NUL-terminated (since there  was  no
       space for the NUL).  This keeps ggstrlcat from running off the end of a
       string.  In practice this should not happen (as it  means  that  either
       size  is  incorrect  or  that dst is not a proper C string).  The check
       exists to prevent potential security problems in incorrect code.


       The following code fragment illustrates the simple case:

       char *s, *p, buf[BUFSIZ];


       (void)ggstrlcpy(buf, s, sizeof(buf));
       (void)ggstrlcat(buf, p, sizeof(buf));

       To detect truncation, perhaps while building a pathname, something like
       the following might be used:

       char *dir, *file, pname[MAXPATHLEN];


       if (ggstrlcpy(pname, dir, sizeof(pname)) >= sizeof(pname))
               goto toolong;
       if (ggstrlcat(pname, file, sizeof(pname)) >= sizeof(pname))
               goto toolong;

       Since  we  know  how  many  characters we copied the first time, we can
       speed things up a bit by using a copy instead of an append:

       char *dir, *file, pname[MAXPATHLEN];
       size_t n;


       n = ggstrlcpy(pname, dir, sizeof(pname));
       if (n >= sizeof(pname))
               goto toolong;
       if (ggstrlcpy(pname + n, file, sizeof(pname) - n) >= sizeof(pname) - n)
               goto toolong;

       However, one may question the validity of such optimizations,  as  they
       defeat the whole purpose of ggstrlcpy and ggstrlcat.


       snprintf(3) strncat(3) strncpy(3)


       strlcpy and strlcat first appeared in OpenBSD 2.4, then in NetBSD 1.4.3
       and FreeBSD 3.3.0.  ggstrlcpy and ggstrlcat has been added to libgg for