sa(3) Socket Abstraction sa(3)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_getlo‐
cal, 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 appli‐
cation programming interface (API), featuring stream and datagram ori‐
ented 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 impor‐
tant 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 sock‐
addr_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 util‐
ity 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 inte‐
gers 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 def‐
inition. 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_time‐
out(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 communica‐
tion, 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 pos‐
sible 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 corre‐
sponding 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 abstrac‐
tion 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 par‐
ticular 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 pre‐
fixlen);
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 pre‐
fixlen 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 communi‐
cation 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 set‐
sockopt(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 ter‐
mination on close.
SA_OPTION_REUSEADDR (int yesno) for enabling (yesno == 1) or dis‐
abling (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 dis‐
abling (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 dis‐
abling (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 require‐
ments without having to change the source code. Usually this is
used to divert the system calls to the variants of a user-land mul‐
tithreading 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 argu‐
ment 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 connec‐
tion 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 con‐
nection. The caller has to destroy these objects later. If no pend‐
ing 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) describ‐
ing 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 getsock‐
name(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 communi‐
cation 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 allo‐
cated 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 per‐
formed 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 *buf‐
done);
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 spec‐
ification 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 commu‐
nication 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 spec‐
ification 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 Identi‐
fiers: 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/proceed‐
ings/usenix2000/freenix/metzprotocol.html, USENIX Annual Technical Con‐
ference, June 2000.
Manual Pages
socket(2), accept(2), bind(2), connect(2), getpeername(2), getsock‐
name(2), getsockopt(2), ioctl(2), listen(2), read(2), recv(2),
select(2), send(2), shutdown(2), socketpair(2), write(2), getpro‐
toent(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
02-Oct-2005 OSSP sa 1.2.5 sa(3)
