357 lines
6.9 KiB
Text
357 lines
6.9 KiB
Text
.TH FCALL 2
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.SH NAME
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Fcall, convS2M, convD2M, convM2S, convM2D, fcallfmt, dirfmt, dirmodefmt, read9pmsg, statcheck, sizeS2M, sizeD2M \- interface to Plan 9 File protocol
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.SH SYNOPSIS
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.B #include <u.h>
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.br
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.B #include <libc.h>
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.br
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.br
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.B #include <fcall.h>
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.PP
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.B
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uint convS2M(Fcall *f, uchar *ap, uint nap)
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.PP
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.B
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uint convD2M(Dir *d, uchar *ap, uint nap)
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.PP
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.B
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uint convM2S(uchar *ap, uint nap, Fcall *f)
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.PP
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.B
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uint convM2D(uchar *ap, uint nap, Dir *d, char *strs)
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.PP
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.B
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int dirfmt(Fmt*)
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.PP
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.B
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int fcallfmt(Fmt*)
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.PP
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.B
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int dirmodefmt(Fmt*)
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.PP
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.B
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int read9pmsg(int fd, uchar *buf, uint nbuf)
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.PP
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.B
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int statcheck(uchar *buf, uint nbuf)
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.PP
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.B
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uint sizeS2M(Fcall *f)
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.PP
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.B
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uint sizeD2M(Dir *d)
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.SH DESCRIPTION
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These
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routines convert messages in the machine-independent format of
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the Plan 9 file protocol,
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9P, to and from a more convenient form,
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an
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.B Fcall
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structure:
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.PP
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.EX
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.if n .ta 4n +6n +5n +6n +18n +4n
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.if t .ta \w'xxxx'u +\w'short 'u +\w'xxxx'u +\w'ushort 'u +\w'ticket[TICKETLEN]; 'u +\w'/* 'u
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#define MAXWELEM 16
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typedef
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struct Fcall
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{
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uchar type;
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u32int fid;
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ushort tag;
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union {
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struct {
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u32int msize; /* Tversion, Rversion */
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char *version; /* Tversion, Rversion */
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};
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struct {
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ushort oldtag; /* Tflush */
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};
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struct {
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char *ename; /* Rerror */
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};
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struct {
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Qid qid; /* Rattach, Ropen, Rcreate */
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u32int iounit; /* Ropen, Rcreate */
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};
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struct {
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Qid aqid; /* Rauth */
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};
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struct {
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u32int afid; /* Tauth, Tattach */
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char *uname; /* Tauth, Tattach */
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char *aname; /* Tauth, Tattach */
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};
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struct {
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u32int perm; /* Tcreate */
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char *name; /* Tcreate */
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uchar mode; /* Tcreate, Topen */
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};
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struct {
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u32int newfid; /* Twalk */
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ushort nwname; /* Twalk */
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char *wname[MAXWELEM]; /* Twalk */
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};
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struct {
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ushort nwqid; /* Rwalk */
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Qid wqid[MAXWELEM]; /* Rwalk */
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};
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struct {
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vlong offset; /* Tread, Twrite */
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u32int count; /* Tread, Twrite, Rread */
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char *data; /* Twrite, Rread */
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};
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struct {
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ushort nstat; /* Twstat, Rstat */
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uchar *stat; /* Twstat, Rstat */
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};
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};
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} Fcall;
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.EE
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.EX
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/* these are implemented as macros */
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uchar GBIT8(uchar*)
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ushort GBIT16(uchar*)
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ulong GBIT32(uchar*)
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vlong GBIT64(uchar*)
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void PBIT8(uchar*, uchar)
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void PBIT16(uchar*, ushort)
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void PBIT32(uchar*, ulong)
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void PBIT64(uchar*, vlong)
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#define BIT8SZ 1
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#define BIT16SZ 2
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#define BIT32SZ 4
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#define BIT64SZ 8
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.EE
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.PP
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This structure is defined in
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.BR <fcall.h> .
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See section 5
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for a full description of 9P messages and their encoding.
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For all message types, the
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.B type
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field of an
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.B Fcall
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holds one of
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.BR Tversion ,
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.BR Rversion ,
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.BR Tattach ,
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.BR Rattach ,
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etc. (defined in an enumerated type in
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.BR <fcall.h> ).
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.B Fid
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is used by most messages, and
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.B tag
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is used by all messages.
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The other fields are used selectively by the message types
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given in comments.
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.PP
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.I ConvM2S
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takes a 9P message at
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.I ap
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of length
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.IR nap ,
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and uses it to fill in
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.B Fcall
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structure
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.IR f .
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If the passed message
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including any data for
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.B Twrite
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and
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.B Rread
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messages
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is formatted properly,
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the return value is the number of bytes the message occupied in the buffer
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.IR ap ,
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which will always be less than or equal to
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.IR nap ;
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otherwise it is 0.
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For
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.B Twrite
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and
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.B Tread
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messages,
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.B data
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is set to a pointer into the argument message,
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not a copy.
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.PP
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.I ConvS2M
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does the reverse conversion, turning
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.I f
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into a message starting at
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.IR ap .
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The length of the resulting message is returned.
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For
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.B Twrite
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and
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.B Rread
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messages,
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.B count
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bytes starting at
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.B data
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are copied into the message.
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.PP
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The constant
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.B IOHDRSZ
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is a suitable amount of buffer to reserve for storing
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the 9P header;
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the data portion of a
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.B Twrite
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or
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.B Rread
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will be no more than the buffer size negotiated in the
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.BR Tversion/Rversion
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exchange, minus
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.BR IOHDRSZ .
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.PP
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The routine
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.I sizeS2M
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returns the number of bytes required to store the machine-independent representation of the
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.B Fcall
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structure
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.IR f ,
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including its initial 32-bit size field.
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In other words, it reports the number of bytes produced
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by a successful call to
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.IR convS2M .
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.PP
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Another structure is
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.BR Dir ,
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used by the routines described in
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.IR stat (2).
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.I ConvM2D
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converts the machine-independent form starting at
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.I ap
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into
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.IR d
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and returns the length of the machine-independent encoding.
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The strings in the returned
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.B Dir
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structure are stored at successive locations starting at
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.BR strs .
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Usually
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.B strs
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will point to storage immediately after the
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.B Dir
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itself.
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It can also be a
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.B nil
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pointer, in which case the string pointers in the returned
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.B Dir
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are all
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.BR nil ;
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however, the return value still includes their length.
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.PP
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.I ConvD2M
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does the reverse translation,
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also returning the length of the encoding.
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If the buffer is too short, the return value will be
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.B BIT16SZ
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and the correct size will be returned in the first
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.B BIT16SZ
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bytes.
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(If the buffer is less that
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.BR BIT16SZ ,
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the return value is zero; therefore a correct test for
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complete packing of the message is that the return value is
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greater than
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.BR BIT16SZ ).
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The macro
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.B GBIT16
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can be used to extract the correct value.
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The related macros with different sizes retrieve the corresponding-sized quantities.
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.B PBIT16
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and its brethren place values in messages.
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With the exception of handling short buffers in
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.IR convD2M ,
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these macros are not usually needed except by internal routines.
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.PP
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Analogous to
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.IR sizeS2M ,
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.I sizeD2M
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returns the number of bytes required to store the machine-independent representation of the
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.B Dir
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structure
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.IR d ,
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including its initial 16-bit size field.
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.PP
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The routine
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.B statcheck
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checks whether the
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.I nbuf
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bytes of
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.I buf
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contain a validly formatted machine-independent
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.B Dir
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entry suitable as an argument, for example, for the
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.B wstat
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(see
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.IR stat (2))
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system call.
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It checks that the sizes of all the elements of the entry sum to exactly
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.IR nbuf ,
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which is a simple but effective test of validity.
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.I Nbuf
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and
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.I buf
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should include the second two-byte (16-bit) length field that precedes the entry when
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formatted in a 9P message (see
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.IR stat (5));
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in other words,
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.I nbuf
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is 2 plus the sum of the sizes of the entry itself.
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.I Statcheck
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also verifies that the length field has the correct value (that is,
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.IB nbuf -2\f1).
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It returns
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.B 0
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for a valid entry and
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.B -1
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for an incorrectly formatted entry.
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.PP
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.IR Dirfmt ,
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.IR fcallfmt ,
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and
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.I dirmodefmt
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are formatting routines, suitable for
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.IR fmtinstall (2).
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They convert
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.BR Dir* ,
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.BR Fcall* ,
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and
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.BR long
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values into string representations of the directory buffer,
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.B Fcall
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buffer,
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or file mode value.
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.I Fcallfmt
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assumes that
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.I dirfmt
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has been installed with format letter
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.L D
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and
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.I dirmodefmt
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with format letter
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.LR M .
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.PP
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.I Read9pmsg
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calls
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.IR read (2)
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multiple times, if necessary, to read an entire 9P message into
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.BR buf .
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The return value is 0 for end of file, or -1 for error; it does not return
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partial messages.
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.SH SOURCE
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.B /sys/src/libc/9sys
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.SH SEE ALSO
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.IR intro (2),
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.IR 9p (2),
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.IR stat (2),
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.IR intro (5)
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