121 lines
2.1 KiB
Text
121 lines
2.1 KiB
Text
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.TH 9PCMDBUF 2
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.SH NAME
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Cmdbuf, parsecmd, respondcmderror, lookupcmd \- control message parsing
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.SH SYNOPSIS
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.ft L
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.nf
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#include <u.h>
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#include <libc.h>
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#include <fcall.h>
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#include <thread.h>
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#include <9p.h>
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.fi
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.PP
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.ft L
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.nf
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.ta \w'\fL1234'u +\w'\fL12345678'u
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typedef struct Cmdbuf
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{
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char *buf;
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char **f;
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int nf;
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} Cmdbuf;
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typedef struct Cmdtab
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{
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int index;
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char *cmd;
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int narg;
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};
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Cmdbuf *parsecmd(char *p, int n)
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Cmdtab *lookupcmd(Cmdbuf *cb, Cmdtab *tab, int ntab)
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void respondcmderror(Req *r, Cmdbuf *cb, char *fmt, ...)
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.fi
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.SH DESCRIPTION
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These data structures and functions provide parsing of textual control messages.
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.PP
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.I Parsecmd
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treats the
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.I n
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bytes at
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.I p
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(which need not be NUL-terminated) as a UTF string and splits it
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using
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.I tokenize
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(see
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.IR getfields (2)).
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It returns a
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.B Cmdbuf
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structure holding pointers to each field in the message.
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It is the caller's responsibility to
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free this structure when it is no longer needed.
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.PP
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.I Lookupcmd
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walks through the array
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.IR ctab ,
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which has
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.I ntab
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entries,
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looking for the first
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.B Cmdtab
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that matches the parsed command.
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(If the parsed command is empty,
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.I lookupcmd
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returns nil immediately.)
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A
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.B Cmdtab
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matches the command if
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.I cmd
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is equal to
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.IB cb -> f [0]
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or if
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.I cmd
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is
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.LR * .
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Once a matching
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.B Cmdtab
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has been found, if
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.I narg
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is not zero, then the parsed command
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must have exactly
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.I narg
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fields (including the command string itself).
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If the command has the wrong number of arguments,
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.I lookupcmd
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returns nil.
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Otherwise, it returns a pointer to the
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.B Cmdtab
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entry.
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If
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.I lookupcmd
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does not find a matching command at all,
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it returns nil.
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Whenever
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.I lookupcmd
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returns nil, it sets the system error string.
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.PP
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.I Respondcmderror
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resoponds to request
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.I r
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with an error of the form
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`\fIfmt\fB:\fI cmd\fR,'
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where
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.I fmt
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is the formatted string and
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.I cmd
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is a reconstruction of the parsed command.
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Fmt
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is often simply
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.B "%r" .
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.SH EXAMPLES
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This interface is not used in any distributed 9P servers.
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It was lifted from the Plan 9 kernel.
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Almost any kernel driver
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.RB ( /sys/src/9/*/dev*.c )
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is a good example.
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.SH SOURCE
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.B /sys/src/lib9p/parse.c
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.SH SEE ALSO
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.IR 9p (2)
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