NAME¶
OSSP sa - Socket Abstraction
VERSION¶
OSSP sa 1.2.5 (02-Oct-2005)
SYNOPSIS¶
- Abstract Data Types:
- sa_rc_t, sa_addr_t, sa_t.
- Address Object Operations:
- sa_addr_create, sa_addr_destroy.
- Address Operations:
- sa_addr_u2a, sa_addr_s2a, sa_addr_a2u, sa_addr_a2s,
sa_addr_match.
- Socket Object Operations:
- sa_create, sa_destroy.
- Socket Parameter Operations:
- sa_type, sa_timeout, sa_buffer, sa_option, sa_syscall.
- Socket Connection Operations:
- sa_bind, sa_connect, sa_listen, sa_accept, sa_getremote,
sa_getlocal, sa_shutdown.
- Socket Input/Output Operations (Stream
Communication):
- sa_getfd, sa_read, sa_readln, sa_write, sa_writef,
sa_flush.
- Socket Input/Output Operations (Datagram
Communication):
- sa_recv, sa_send, sa_sendf.
- Socket Error Handling:
- sa_error.
DESCRIPTION¶
OSSP sa is an abstraction library for the Unix
Socket networking
application programming interface (API), featuring stream and datagram
oriented communication over
Unix Domain and
Internet Domain (TCP
and UDP) sockets.
It provides the following key features:
- Stand-Alone, Self-Contained, Embeddable
- Although there are various Open Source libraries available
which provide a similar abstraction approach, they all either lack
important features or unfortunately depend on other companion libraries.
OSSP sa fills this gap by providing all important features (see
following points) as a stand-alone and fully self-contained library. This
way OSSP sa can be trivially embedded as a sub-library into other
libraries. It especially provides additional support for namespace-safe
embedding of its API in order to avoid symbol conflicts (see SA_PREFIX in
sa.h).
- Address Abstraction
- Most of the ugliness in the Unix Socket API is the
necessity to have to deal with the various address structures (struct
sockaddr_xx) which exist because of both the different communication types
and addressing schemes. OSSP sa fully hides this by providing an
abstract and opaque address type (sa_addr_t) together with utility
functions which allow one to convert from the traditional struct sockaddr
or URI specification to the sa_addr_t and vice versa without having to
deal with special cases related to the underlying particular struct
sockaddr_xx. OSSP sa support Unix Domain and both IPv4 and
IPv6 Internet Domain addressing.
- Type Abstraction
- Some other subtle details in the Unix Socket API
make the life hard in practice: socklen_t and ssize_t. These two types
originally were (and on some platforms still are) plain integers or
unsigned integers while POSIX later introduced own types for them (and
even revised these types after some time again). This is nasty, because
for 100% type-correct API usage (especially important on 64-bit machines
where pointers to different integer types make trouble), every application
has to check whether the newer types exists, and if not provide own
definitions which map to the still actually used integer type on the
underlying platform. OSSP sa hides most of this in its API and for
socklen_t provides a backward-compatibility definition. Instead of ssize_t
it can use size_t because OSSP sa does not use traditional Unix
return code semantics.
- I/O Timeouts
- Each I/O function in OSSP sa is aware of timeouts
(set by sa_timeout(3)), i.e., all I/O operations return SA_ERR_TMT
if the timeout expired before the I/O operation was able to succeed. This
allows one to easily program less-blocking network services. OSSP
sa internally implements these timeouts either through the
SO_{SND,RCV}TIMEO feature on more modern Socket implementations or
through traditional select(2). This way high performance is
achieved on modern platforms while the full functionality still is
available on older platforms.
- I/O Stream Buffering
- If OSSP sa is used for stream communication,
internally all I/O operations can be performed through input and/or output
buffers (set by sa_buffer(3)) for achieving higher I/O performance
by doing I/O operations on larger aggregated messages and with less
required system calls. Additionally if OSSP sa is used for stream
communication, for convenience reasons line-oriented reading (
sa_readln(3)) and formatted writing (see sa_writef(3)) is
provided, modelled after STDIO's fgets(3) and fprintf(3).
Both features fully leverage from the I/O buffering.
DATA TYPES¶
OSSP sa uses three data types in its API:
- sa_rc_t (Return Code Type)
- This is an exported enumerated integer type with the
following possible values:
SA_OK Everything Ok
SA_ERR_ARG Invalid Argument
SA_ERR_USE Invalid Use Or Context
SA_ERR_MEM Not Enough Memory
SA_ERR_MTC Matching Failed
SA_ERR_EOF End Of Communication
SA_ERR_TMT Communication Timeout
SA_ERR_SYS Operating System Error (see errno)
SA_ERR_IMP Implementation Not Available
SA_ERR_INT Internal Error
- sa_addr_t (Socket Address Abstraction Type)
- This is an opaque data type representing a socket address.
Only pointers to this abstract data type are used in the API.
- sa_t (Socket Abstraction Type)
- This is an opaque data type representing a socket. Only
pointers to this abstract data type are used in the API.
FUNCTIONS¶
OSSP sa provides a bunch of API functions, all modelled after the same
prototype:
sa_rc_t
sa_name(sa_[addr_]_t *, ...)
This means, every function returns sa_rc_t to indicate its success (SA_OK) or
failure (SA_ERR_
XXX) by returning a return code (the corresponding
describing text can be determined by passing this return code to
sa_error(3)). Each function name starts with the common prefix sa_ and
receives a sa_t (or sa_addr_t) object handle on which it operates as its first
argument.
Address Object Operations
This API part provides operations for the creation and destruction of address
abstraction sa_addr_t.
- sa_rc_t sa_addr_create(sa_addr_t **saa);
- Create a socket address abstraction object. The object is
stored in saa on success.
Example: sa_addr_t *saa; sa_addr_create(&saa);
- sa_rc_t sa_addr_destroy(sa_addr_t *saa);
- Destroy a socket address abstraction object. The object
saa is invalid after this call succeeded.
Example: sa_addr_destroy(saa);
Address Operations
This API part provides operations for working with the address abstraction
sa_addr_t.
- sa_rc_t sa_addr_u2a(sa_addr_t *saa, const
char * uri, ...);
- Import an address into by converting from an URI
specification to the corresponding address abstraction.
The supported syntax for uri is: "unix:path" for
Unix Domain addresses and "inet://
addr:port[#protocol]" for Internet Domain
addresses.
In the URI, path can be an absolute or relative filesystem path to an
existing or not-existing file. addr can be an IPv4 address in
dotted decimal notation ("127.0.0.1"), an IPv6 address in
colon-separated (optionally abbreviated) hexadecimal notation
("::1") or a to-be-resolved hostname
("localhost.example.com"). port has to be either a
decimal port in the range 1...65535 or a port name ("smtp"). If
port is specified as a name, it is resolved as a TCP port by
default. To force resolving a port name via a particular protocol,
protocol can be specified as either "tcp" or
"udp".
The result is stored in saa on success.
Example: sa_addr_u2a(saa, "inet://192.168.0.1:smtp");
- sa_rc_t sa_addr_s2a(sa_addr_t *saa, const
struct sockaddr * sabuf, socklen_t salen);
- Import an address by converting from a traditional struct
sockaddr object to the corresponding address abstraction.
The accepted addresses for sabuf are: struct sockaddr_un (AF_LOCAL),
struct sockaddr_in (AF_INET) and struct sockaddr_in6 (AF_INET6). The
salen is the corresponding sizeof(...) of the particular underyling
structure.
The result is stored in saa on success.
Example: sockaddr_in in; sa_addr_s2a(saa, (struct sockaddr *)&in,
(socklen_t)sizeof(in));
- sa_rc_t sa_addr_a2u(sa_addr_t *saa, char
**uri);
- Export an address by converting from the address
abstraction to the corresponding URI specification.
The result is a string of the form "unix: path" for
Unix Domain addresses and
"inet://addr:port" for Internet
Domain addresses. Notice that addr and port are
returned in numerical (unresolved) way. Additionally, because usually one
cannot map bidirectionally between TCP or UDP port names and the numerical
value, there is no distinction between TCP and UDP here.
The result is stored in uri on success. The caller has to
free(3) the uri buffer later.
Example: char *uri; sa_addr_a2u(saa, &uri);
- sa_rc_t sa_addr_a2s(sa_addr_t *saa, struct
sockaddr ** sabuf, socklen_t *salen);
- Export an address by converting from the address
abstraction to the corresponding traditional struct sockaddr object.
The result is one of the following particular underlying address structures:
struct sockaddr_un (AF_LOCAL), struct sockaddr_in (AF_INET) and struct
sockaddr_in6 (AF_INET6).
The result is stored in sabuf and salen on success. The caller
has to free(3) the sabuf buffer later.
Example: struct sockaddr sabuf, socklen_t salen; sa_addr_a2s(saa, &sa,
&salen);
- sa_rc_t sa_addr_match(sa_addr_t *saa1,
sa_addr_t * saa2, size_t prefixlen);
- Match two address abstractions up to a specified prefix.
This compares the addresses saa1 and saa2 by only taking the
prefix part of length prefixlen into account. prefixlen is
number of filesystem path characters for Unix Domain addresses and
number of bits for Internet Domain addresses. In case of
Internet Domain addresses, the addresses are matched in network
byte order and the port (counting as an additional bit/item of length 1)
is virtually appended to the address for matching. Specifying
prefixlen as -1 means matching the whole address (but without the
virtually appended port) without having to know how long the underlying
address representation (length of path for Unix Domain addresses, 32+1
[IPv4] or 128+1 [IPv6] for Internet Domain addresses) is. Specifying
prefixlen as -2 is equal to -1 but additionally the port is
matched, too.
This especially can be used to implement Access Control Lists (ACL) without
having to fiddle around with the underlying representation. For this, make
saa1 the to be checked address and saa2 plus
prefixlen the ACL pattern as shown in the following example.
Example:
sa_addr_t *srv_sa;
sa_addr_t *clt_saa;
sa_t *clt_sa;
sa_addr_t *acl_saa;
char *acl_addr = "192.168.0.0";
int acl_len = 24;
...
sa_addr_u2a(&acl_saa, "inet://%s:0", acl_addr);
...
while (sa_accept(srv_sa, &clt_saa, &clt_sa) == SA_OK) {
if (sa_addr_match(clt_saa, acl_saa, acl_len) != SA_OK) {
/* connection refused */
...
sa_addr_destroy(clt_saa);
sa_destroy(clt_sa);
continue;
}
...
}
...
Socket Object Operations
This API part provides operations for the creation and destruction of socket
abstraction sa_t.
- sa_rc_t sa_create(sa_t **sa);
- Create a socket abstraction object. The object is stored in
sa on success.
Example: sa_t *sa; sa_create(&sa);
- sa_rc_t sa_destroy(sa_t *sa);
- Destroy a socket abstraction object. The object sa
is invalid after this call succeeded.
Example: sa_destroy(sa);
Socket Parameter Operations
This API part provides operations for parameterizing the socket abstraction
sa_t.
- sa_rc_t sa_type(sa_t *sa, sa_type_t
type);
- Assign a particular communication protocol type to the
socket abstraction object.
A socket can only be assigned a single protocol type at any time.
Nevertheless one can switch the type of a socket abstraction object at any
time in order to reuse it for a different communication. Just keep in mind
that switching the type will stop a still ongoing communication by closing
the underlying socket.
Possible values for type are SA_TYPE_STREAM (stream communication)
and SA_TYPE_DATAGRAM (datagram communication). The default communication
protocol type is SA_TYPE_STREAM.
Example: sa_type(sa, SA_TYPE_STREAM);
- sa_rc_t sa_timeout(sa_t *sa, sa_timeout_t
id, long sec, long usec);
- Assign one or more communication timeouts to the socket
abstraction object.
Possible values for id are: SA_TIMEOUT_ACCEPT (affecting
sa_accept(3)), SA_TIMEOUT_CONNECT (affecting sa_connect(3)),
SA_TIMEOUT_READ (affecting sa_read(3), sa_readln(3) and
sa_recv(3)) and SA_TIMEOUT_WRITE (affecting sa_write(3),
sa_writef(3), sa_send(3), and sa_sendf(3)).
Additionally you can set all four timeouts at once by using
SA_TIMEOUT_ALL. The default is that no communication timeouts are used
which is equal to sec=0/usec=0.
Example: sa_timeout(sa, SA_TIMEOUT_ALL, 30, 0);
- sa_rc_t sa_buffer(sa_t *sa, sa_buffer_t
id, size_t size);
- Assign I/O communication buffers to the socket abstraction
object.
Possible values for id are: SA_BUFFER_READ (affecting
sa_read(3) and sa_readln(3)) and SA_BUFFER_WRITE (affecting
sa_write(3) and sa_writef(3)). The default is that no
communication buffers are used which is equal to size=0.
Example: sa_buffer(sa, SA_BUFFER_READ, 16384);
- sa_rc_t sa_option(sa_t *sa, sa_option_t
id, ...);
- Adjust various options of the socket abstraction object.
The adjusted option is controlled by id. The number and type of the
expected following argument(s) are dependent on the particular option.
Currently the following options are implemented (option arguments in
parenthesis):
SA_OPTION_NAGLE (int yesno) for enabling (yesno=1) or
disabling ( yesno == 0) Nagle's Algorithm (see RFC898 and
TCP_NODELAY of setsockopt(2)).
SA_OPTION_LINGER (int amount) for enabling (amount ==
seconds != 0) or disabling ( amount == 0) lingering on close
(see SO_LINGER of setsockopt(2)). Notice: using seconds >
0 results in a regular (maximum of seconds lasting) lingering on
close while using seconds < 0 results in the special case of a
TCP RST based connection termination on close.
SA_OPTION_REUSEADDR (int yesno) for enabling (yesno == 1) or
disabling ( yesno == 0) the reusability of the address on binding
via sa_bind(3) (see SO_REUSEADDR of setsockopt(2)).
SA_OPTION_REUSEPORT (int yesno) for enabling (yesno == 1) or
disabling ( yesno == 0) the reusability of the port on binding via
sa_bind(3) (see SO_REUSEPORT of setsockopt(2)).
SA_OPTION_NONBLOCK (int yesno) for enabling (yesno == 1) or
disabling ( yesno == 0) non-blocking I/O mode (see O_NONBLOCK of
fcntl(2)).
Example: sa_option(sa, SA_OPTION_NONBLOCK, 1);
- sa_rc_t sa_syscall(sa_t *sa, sa_syscall_t
id, void (* fptr)(), void *fctx);
- Divert I/O communication related system calls to user
supplied callback functions.
This allows you to override mostly all I/O related system calls OSSP
sa internally performs while communicating. This can be used to
adapt OSSP sa to different run-time environments and requirements
without having to change the source code. Usually this is used to divert
the system calls to the variants of a user-land multithreading facility
like GNU Pth.
The function supplied as fptr is required to fulfill the API of the
replaced system call, i.e., it has to have the same prototype (if
fctx is NULL). If fctx is not NULL, this prototype has to be
extended to accept an additional first argument of type void * which
receives the value of fctx. It is up to the callback function
whether to pass the call through to the replaced actual system call or
not.
Possible values for id are (expected prototypes behind fptr
are given in parenthesis):
SA_SYSCALL_CONNECT: "int (*)([void *,] int, const struct
sockaddr *, socklen_t)", see connect(2).
SA_SYSCALL_ACCEPT: "int (*)([void *,] int, struct sockaddr *,
socklen_t *)", see accept(2).
SA_SYSCALL_SELECT: "int (*)([void *,] int, fd_set *, fd_set *,
fd_set *, struct timeval *)", see select(2).
SA_SYSCALL_READ: "ssize_t (*)([void *,] int, void *,
size_t)", see read(2).
SA_SYSCALL_WRITE: "ssize_t (*)([void *,] int, const void *,
size_t)", see write(2).
SA_SYSCALL_RECVFROM: "ssize_t (*)([void *,] int, void *,
size_t, int, struct sockaddr *, socklen_t *)", see
recvfrom(2).
SA_SYSCALL_SENDTO: "ssize_t (*)([void *,] int, const void *,
size_t, int, const struct sockaddr *, socklen_t)", see
sendto(2).
Example:
ssize_t
trace_read(void *ctx, int fd, void *buf, size_t len)
{
FILE *fp = (FILE *)ctx;
ssize_t rv;
int errno_saved;
rv = read(fd, buf, len);
errno_saved = errno;
fprintf(fp, "read(%d, %lx, %d) = %d\n",
fd, (long)buf, len, rv);
errno = errno_saved;
return rv;
}
...
FILE *trace_fp = ...;
sa_syscall(sa, SA_SC_READ, trace_read, trace_fp);
...
Socket Connection Operations
This API part provides connection operations for stream-oriented data
communication through the socket abstraction sa_t.
- sa_rc_t sa_bind(sa_t *sa, sa_addr_t
*laddr);
- Bind socket abstraction object to a local protocol address.
This assigns the local protocol address laddr. When a socket is
created, it exists in an address family space but has no protocol address
assigned. This call requests that laddr be used as the local
address. For servers this is the address they later listen on (see
sa_listen(3)) for incoming connections, for clients this is the
address used for outgoing connections (see sa_connect(3)).
Internally this directly maps to bind(2).
Example: sa_bind(sa, laddr);
- sa_rc_t sa_connect(sa_t *sa, sa_addr_t
*raddr);
- Initiate an outgoing connection on a socket abstraction
object.
This performs a connect to the remote address raddr. If the socket is
of type SA_TYPE_DATAGRAM, this call specifies the peer with which the
socket is to be associated; this address is that to which datagrams are to
be sent, and the only address from which datagrams are to be received. If
the socket is of type SA_TYPE_STREAM, this call attempts to make a
connection to the remote socket. Internally this directly maps to
connect(2).
Example: sa_connect(sa, raddr);
- sa_rc_t sa_listen(sa_t *sa, int
backlog);
- Listen for incoming connections on a socket abstraction
object.
A willingness to accept incoming connections and a queue limit for incoming
connections are specified by this call. The backlog argument
defines the maximum length the queue of pending connections may grow to.
Internally this directly maps to listen(2).
Example: sa_listen(sa, 128);
- sa_rc_t sa_accept(sa_t *sa, sa_addr_t
**caddr, sa_t ** csa);
- Accept incoming connection on a socket abstraction object.
This accepts an incoming connection by extracting the first connection
request on the queue of pending connections. It creates a new socket
abstraction object (returned in csa) and a new socket address
abstraction object (returned in caddr) describing the connection.
The caller has to destroy these objects later. If no pending connections
are present on the queue, it blocks the caller until a connection is
present.
Example:
sa_addr_t *clt_saa;
sa_t *clt_sa;
...
while (sa_accept(srv_sa, &clt_saa, &clt_sa) == SA_OK) {
...
}
- sa_rc_t sa_getremote(sa_t *sa, sa_addr_t
**raddr);
- Get address abstraction of remote side of communication.
This determines the address of the communication peer and creates a new
socket address abstraction object (returned in raddr) describing
the peer address. The application has to destroy raddr later with
sa_addr_destroy(3). Internally this maps to getpeername(2).
Example: sa_addr_t *raddr; sa_getremote(sa, &raddr);
- sa_rc_t sa_getlocal(sa_t *sa, sa_addr_t
**laddr);
- Get address abstraction of local side of communication.
This determines the address of the local communication side and creates a
new socket address abstraction object (returned in laddr)
describing the local address. The application has to destroy laddr
later with sa_addr_destroy(3). Internally this maps to
getsockname(2).
Example: sa_addr_t *laddr; sa_getlocal(sa, &laddr);
- sa_rc_t sa_shutdown(sa_t *sa, char
*flags);
- Shut down part of the full-duplex connection.
This performs a shut down of the connection described in sa. The
flags string can be either "r" (indicating the read channel of
the communication is shut down only), "w" (indicating the write
channel of the communication is shut down only), or "rw"
(indicating both the read and write channels of the communication are shut
down). Internally this directly maps to shutdown(2).
Example: sa_shutdown(sa, "w");
Socket Input/Output Operations (Stream Communication)
This API part provides I/O operations for stream-oriented data communication
through the socket abstraction sa_t.
- sa_rc_t sa_getfd(sa_t *sa, int
*fd);
- Get underlying socket filedescriptor.
This peeks into the underlying socket filedescriptor OSSP sa
allocated internally for the communication. This can be used for adjusting
the socket communication (via fcntl(2), setsockopt(2), etc)
directly.
Think twice before using this, then think once more. After all that, think
again. With enough thought, the need for directly manipulating the
underlying socket can often be eliminated. At least remember that all your
direct socket operations fully by-pass OSSP sa and this way can
leads to nasty side-effects.
Example: int fd; sa_getfd(sa, &fd);
- sa_rc_t sa_read(sa_t *sa, char *buf,
size_t buflen, size_t *bufdone);
- Read a chunk of data from socket into own buffer.
This reads from the socket (optionally through the internal read buffer) up
to a maximum of buflen bytes into buffer buf. The actual
number of read bytes is stored in bufdone. This internally maps to
read(2).
Example: char buf[1024]; size_t n; sa_read(sa, buf, sizeof(buf),
&n);
- sa_rc_t sa_readln(sa_t *sa, char *buf,
size_t buflen, size_t *bufdone);
- Read a line of data from socket into own buffer.
This reads from the socket (optionally through the internal read buffer) up
to a maximum of buflen bytes into buffer buf, but only as
long as no line terminating newline character (0x0a) was found. The line
terminating newline character is stored in the buffer plus a (not counted)
terminating NUL character ('\0'), too. The actual number of read bytes is
stored in bufdone. This internally maps to sa_read(3).
Keep in mind that for efficiency reasons, line-oriented I/O usually always
should be performed with read buffer (see sa_option(3) and
SA_BUFFER_READ). Without such a read buffer, the performance is cruel,
because single character read(2) operations would be performed on
the underlying socket.
Example: char buf[1024]; size_t n; sa_readln(sa, buf, sizeof(buf),
&n);
- sa_rc_t sa_write(sa_t *sa, const char
*buf, size_t buflen, size_t *bufdone);
- Write a chunk of data to socket from own buffer.
This writes to the socket (optionally through the internal write buffer)
buflen bytes from buffer buf. In case of a partial write,
the actual number of written bytes is stored in bufdone. This
internally maps to write(2).
Example: sa_write(sa, cp, strlen(cp), NULL);
- sa_rc_t sa_writef(sa_t *sa, const char
*fmt, ...);
- Write formatted data data to socket.
This formats a string according to the printf(3)-style format
specification fmt and sends the result to the socket (optionally
through the internal write buffer). In case of a partial socket write, the
not written data of the formatted string is internally discarded. Hence
using a write buffer is strongly recommended here (see sa_option(3)
and SA_BUFFER_WRITE). This internally maps to sa_write(3).
The underlying string formatting engine is just a minimal one and for
security and independence reasons intentionally not directly based on s[n]
printf(3). It understands only the following format specifications:
"%%", "%c" (char), "%s" (char *) and
"%d" (int) without any precision and padding possibilities. It
is intended for minimal formatting only. If you need more sophisticated
formatting, you have to format first into an own buffer via s[n]
printf(3) and then write this to the socket via sa_write(3)
instead.
Example: sa_writef(sa, "%s=%d\n", cp, i);
- sa_rc_t sa_flush(sa_t *sa);
- Flush still pending outgoing data to socket.
This writes all still pending outgoing data for the internal write buffer
(see sa_option(3) and SA_BUFFER_WRITE) to the socket. This
internally maps to write(2).
Example: sa_flush(sa);
Socket Input/Output Operations (Datagram Communication)
This API part provides I/O operations for datagram-oriented data communication
through the socket abstraction sa_t.
- sa_rc_t sa_recv(sa_t *sa, sa_addr_t
**raddr, char * buf, size_t buflen, size_t
*bufdone);
- Receive a chunk of data from remote address via socket into
own buffer.
This receives from the remote address specified in raddr via the
socket up to a maximum of buflen bytes into buffer buf. The
actual number of received bytes is stored in bufdone. This
internally maps to recvfrom(2).
Example: char buf[1024]; size_t n; sa_recv(sa, buf, sizeof(buf), &n,
saa);
- sa_rc_t sa_send(sa_t *sa, sa_addr_t
*raddr, const char * buf, size_t buflen, size_t
*bufdone);
- Send a chunk of data to remote address via socket from own
buffer.
This sends to the remote address specified in raddr via the socket
buflen bytes from buffer buf. The actual number of sent
bytes is stored in bufdone. This internally maps to
sendto(2).
Example: sa_send(sa, buf, strlen(buf), NULL, saa);
- sa_rc_t sa_sendf(sa_t *sa, sa_addr_t
*raddr, const char * fmt, ...);
- Send formatted data data to remote address via socket.
This formats a string according to the printf(3)-style format
specification fmt and sends the result to the socket as a single
piece of data chunk. In case of a partial socket write, the not written
data of the formatted string is internally discarded.
The underlying string formatting engine is just a minimal one and for
security and independence reasons intentionally not directly based on s[n]
printf(3). It understands only the following format specifications:
"%%", "%c" (char), "%s" (char *) and
"%d" (int) without any precision and padding possibilities. It
is intended for minimal formatting only. If you need more sophisticated
formatting, you have to format first into an own buffer via s[n]
printf(3) and then send this to the remote address via
sa_send(3) instead.
Example: sa_sendf(sa, saa, "%s=%d\n", cp, i);
Socket Error Handling
This API part provides error handling operations only.
- char *sa_error(sa_rc_t rv);
- Return the string representation corresponding to the
return code value rv. The returned string has to be treated
read-only by the application and is not required to be deallocated.
SEE ALSO¶
Standards
R. Gilligan, S. Thomson, J. Bound, W. Stevens:
"Basic Socket Interface
Extensions for IPv6",
RFC 2553, March 1999.
W. Stevens:
"Advanced Sockets API for IPv6",
RFC 2292,
February 1998.
R. Fielding, L. Masinter, T. Berners-Lee:
"Uniform Resource Identifiers:
Generic Syntax",
RFC 2396, August 1998.
R. Hinden, S. Deering:
"IP Version 6 Addressing Architecture",
RFC 2373, July 1998.
R. Hinden, B. Carpenter, L. Masinter:
"Format for Literal IPv6 Addresses
in URL's",
RFC 2732, December 1999.
Papers
Stuart Sechrest:
"An Introductory 4.4BSD Interprocess Communication
Tutorial", FreeBSD 4.4 (/usr/share/doc/psd/20.ipctut/).
Samuel J. Leffler, Robert S. Fabry, William N. Joy, Phil Lapsley:
"An
Advanced 4.4BSD Interprocess Communication Tutorial", FreeBSD 4.4
(/usr/share/doc/psd/21.ipc/).
Craig Metz:
"Protocol Independence Using the Sockets API",
http://www.usenix.org/publications/library/proceedings/usenix2000/freenix/metzprotocol.html,
USENIX Annual Technical Conference, June 2000.
Manual Pages
socket(2),
accept(2),
bind(2),
connect(2),
getpeername(2),
getsockname(2),
getsockopt(2),
ioctl(2),
listen(2),
read(2),
recv(2),
select(2),
send(2),
shutdown(2),
socketpair(2),
write(2),
getprotoent(3),
protocols(4).
HISTORY¶
OSSP sa was invented in August 2001 by Ralf S. Engelschall
<rse@engelschall.com> under contract with Cable & Wireless
<
http://www.cw.com/> for use inside the OSSP project. Its creation was
prompted by the requirement to implement an SMTP logging channel for the
OSSP l2 library. Its initial code was derived from a predecessor
sub-library originally written for socket address abstraction inside the
OSSP lmtp2nntp tool.
AUTHOR¶
Ralf S. Engelschall
rse@engelschall.com
www.engelschall.com