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Diffstat (limited to 'manual/socket.texi')
| -rw-r--r-- | manual/socket.texi | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/manual/socket.texi b/manual/socket.texi index f8564ab..b9102c6 100644 --- a/manual/socket.texi +++ b/manual/socket.texi @@ -1268,6 +1268,57 @@ The host database contains an entry for the name, but it doesn't have an associated Internet address. @end table +The lookup functions above all have one in common: they are not +reentrant and therefore unusable in multi-threaded applications. +Therefore provides the GNU C library a new set of functions which can be +used in this context. + +@comment netdb.h +@comment GNU +@deftypefun int gethostbyname_r (const char *restrict @var{name}, struct hostent *restrict @var{result_buf}, char *restrict @var{buf}, size_t @var{buflen}, struct hostent **restrict @var{result}, int *restrict @var{h_errnop}) +The @code{gethostbyname_r} function returns information about the host +named @var{name}. The caller must pass a pointer to an object of type +@code{struct hostent} in the @var{result_buf} parameter. In addition +the function may need extra buffer space and the caller must pass an +pointer and the size of the buffer in the @var{buf} and @var{buflen} +parameters. + +A pointer to the buffer, in which the result is stored, is available in +@code{*@var{result}} after the function call successfully returned. +Success is signalled by a zero return value. If the function failed the +return value is an error number. In addition to the errors defined for +@code{gethostbyname} it can also be @code{ERANGE}. In this case the +call should be repeated with a larger buffer. Additional error +information is not stored in the global variable @code{h_errno} but +instead in the object pointed to by @var{h_errnop}. +@end deftypefun + +@comment netdb.h +@comment GNU +@deftypefun int gethostbyname2_r (const char *@var{name}, int @var{af}, struct hostent *restrict @var{result_buf}, char *restrict @var{buf}, size_t @var{buflen}, struct hostent **restrict @var{result}, int *restrict @var{h_errnop}) +The @code{gethostbyname2_r} function is like @code{gethostbyname_r}, but +allows the caller to specify the desired address family (e.g.@: +@code{AF_INET} or @code{AF_INET6}) for the result. +@end deftypefun + +@comment netdb.h +@comment GNU +@deftypefun int gethostbyaddr_r (const char *@var{addr}, int @var{length}, int @var{format}, struct hostent *restrict @var{result_buf}, char *restrict @var{buf}, size_t @var{buflen}, struct hostent **restrict @var{result}, int *restrict @var{h_errnop}) +The @code{gethostbyaddr_r} function returns information about the host +with Internet address @var{addr}. The parameter @var{addr} is not +really a pointer to char - it can be a pointer to an IPv4 or an IPv6 +address. The @var{length} argument is the size (in bytes) of the address +at @var{addr}. @var{format} specifies the address format; for an IPv4 +Internet address, specify a value of @code{AF_INET}; for an IPv6 +Internet address, use @code{AF_INET6}. + +Similar to the @code{gethostbyname_r} function, the caller must provide +buffers for the result and memory used internally. In case of success +the funciton returns zero. Otherwise the value is an error number where +@code{ERANGE} has the special meaning that the caller-provided buffer is +too small. +@end deftypefun + You can also scan the entire hosts database one entry at a time using @code{sethostent}, @code{gethostent}, and @code{endhostent}. Be careful in using these functions, because they are not reentrant. |