STYX(10.2) STYX(10.2)
NAME
Fcall, convS2M, convD2M, convM2S, convM2D, fcallconv,
dirconv - C interface to Inferno File protocol
SYNOPSIS
#include <styx.h>
int convS2M(Fcall *f, char *ap)
int convD2M(Dir *d, char *ap)
int convM2S(char *ap, Fcall *f, int n)
int convM2D(char *ap, Dir *d)
int dirconv(Fmt*)
int fcallconv(Fmt*)
DESCRIPTION
These routines convert messages in the machine-independent
format of the Inferno file protocol, Styx (see section 5 of
this manual) to and from a more convenient form, an Fcall
structure:
typedef
struct Fcall
{
char type;
short fid;
ushort tag;
ushort oldtag; /* T-Flush */
Qid qid; /* R-Attach, R-Walk, R-Open, R-Create */
char uname[NAMELEN]; /* T-Attach */
char aname[NAMELEN]; /* T-Attach */
char ename[ERRLEN]; /* R-Error */
long perm; /* T-Create */
short newfid; /* T-Clone */
char name[NAMELEN]; /* T-Walk, T-Create */
char mode; /* T-Create, T-Open */
long offset; /* T-Read, T-Write */
long count; /* T-Read, T-Write, R-Read */
char *data; /* T-Write, R-Read */
char stat[DIRLEN]; /* T-Wstat, R-Stat */
} Fcall;
This structure is defined in <styx.h>. See the other pages
in this section of the manual for a full description of Styx
messages and their encoding. For all message types, the
type field of an Fcall holds one of Tnop, Rnop, Tattach,
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STYX(10.2) STYX(10.2)
Rattach, etc. (defined in an enumerated type in <styx.h>).
Fid is used by most messages, and tag is used by all mes-
sages. The other fields are used selectively by the message
types given in comments.
ConvM2S takes a buffer ap of length n, and attempts to
unpack a complete Styx message to fill in Fcall structure f.
To help a caller that is reading and processing Styx mes-
sages from an input stream that does not preserve message
boundaries, the return value distinguishes three cases:
- If the passed message, including any data for Twrite
and Rread messages, forms a complete, properly format-
ted Styx message, the return value is the number of
bytes consumed. It can be less than n when further
messages or partial messages remain in ap. For Twrite
and Tread messages, f->data is set to a pointer into
the argument message, not a copy.
- If the message in ap is incomplete but valid thus far,
the return value is 0; more bytes must be read and
added to the buffer to complete the message.
- If the message is invalid, the return value is -1.
ConvS2M does the reverse conversion, turning f into a mes-
sage starting at ap. The length of the resulting message is
returned; it returns -1 if the message type is invalid. For
Twrite and Rread messages, f->count bytes starting at
f->data are copied into the message.
The constant MAXMSG is the length of the longest message,
excluding data; MAXFDATA (8192) is the maximum count in a
read or write message. Thus messages are guaranteed to be
shorter than MAXMSG+MAXFDATA bytes long.
Another structure is Dir, used by the routines described in
sys-stat(2). ConvM2D converts the machine-independent form
starting at ap into d and returns the length of the encod-
ing. ConvD2M does the reverse translation, also returning
the length of the encoding.
Dirconv and fcallconv are print(10.2) formatting routines.
They convert Dir* and Fcall* values into string representa-
tions of the directory buffer or Fcall buffer. Fcallconv is
installed under format F in the Inferno emulator and kernel.
SOURCE
/include/styx.h
SEE ALSO
intro(2), styxlib(2), sys-stat(2), intro(5), intro(10),
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STYX(10.2) STYX(10.2)
print(10.2)
BUGS
The offset and directory length fields have 8 bytes in the
protocol, but these routines assume they fit into a long.
ConvS2M should check for counts exceeding MAXFMSG.
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