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Diffstat (limited to 'man/10/newchan')
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diff --git a/man/10/newchan b/man/10/newchan new file mode 100644 index 00000000..69346d46 --- /dev/null +++ b/man/10/newchan @@ -0,0 +1,227 @@ +.TH NEWCHAN 10.2 +.SH NAME +newchan, chanfree, cclose, eqqid, eqchan, isdir, fdtochan, namec \- channel operations +.SH SYNOPSIS +.ta \w'\fLChan* 'u +.B +Chan* newchan(void) +.PP +.B +void chanfree(Chan *c) +.PP +.B +int eqqid(Qid a, Qid b) +.PP +.B +int eqchan(Chan *a, Chan *b, int pathonly) +.PP +.B +void isdir(Chan *c) +.PP +.B +Chan* fdtochan(Fgrp *f, int fd, int mode, int chkmnt, int iref) +.PP +.B +Chan* namec(char *pathname, int amode, int omode, ulong perm) +.PP +.B +void cclose(Chan *c) +.SH DESCRIPTION +A value of type +.B Chan +represents a kernel channel for I/O and name space operations. +It has the following public structure: +.IP +.EX +typedef struct Chan{ + ushort type; /* driver name */ + ulong dev; /* instance number */ + ushort mode; /* open mode */ + ushort flag; /* COPEN set once opened */ + ulong offset; /* current file offset */ + Qid qid; /* unique id (path, vers) */ + Cname* name; /* name by which it was accessed */ +.EE +.PP +.I Newchan +returns a pointer to a newly allocated channel (sleeping if necessary until memory is available). +Device drivers do not normally call +.IR newchan +directly, but instead allocate channels using either +.IR devattach , +when a process attaches to the device's root, +or +.IR devclone , +when an existing channel is cloned; +see +.IR devattach (10.2). +.PP +.I Chanfree +frees the channel structure +.I c +for reuse. +.PP +.I Eqqid +returns 1 if +.B Qid +values +.I a +and +.I b +are equal +(ie, +both their +.B path +and +.B vers +members are equal); +it returns 0 otherwise. +.PP +.I Eqchan +returns 1 if +.I a +and +.I b +have the same +.BR qid , +.BR type +and +.BR dev +members +(ie, they represent the same file); +it returns 0 otherwise. +If +.I pathonly +is non-zero, the comparison of the two +.B qid +members compares only their +.B path +values, +ignoring the version field +.BR vers . +.PP +.I Isdir +checks that a given channel +.I c +is a directory. +If so, it returns; +otherwise, it generates an +.IR error (10.2), +.BR Enotdir . +.PP +The +.B Fgrp +structure represents an array of open files, each +represented by a +.BR Chan , +indexed by integer file descriptors. +A given +.B Fgrp +can be shared between processes. +.PP +.I Fdtochan +returns a pointer to the +.B Chan +corresponding to file descriptor +.I fd +in file descriptor group +.I f +(almost invariably +.BR up->env->fgrp , +the file descriptor group for the current process). +If +.I mode +is a valid mode for +.IR sys-open (2), +typically +.BR OREAD , +.B OWRITE +or +.BR ORDWR , +it must correspond to the mode with which +.I fd +was originally opened; if +.I mode +is +.BR -1 , +no check is made. +If +.I chkmnt +is non-zero, +.I c +must not be a channel in use by the mount driver +.IR mnt (3). +On successful return, if +.I iref +is non-zero, the channel's reference count has been incremented. +.I Fdtochan +calls +.IR error (10.2) +if it detects invalid uses, in particular an invalid file descriptor +.IR fd . +.PP +.I Namec +looks up a +.I pathname +in the current name space and returns a channel. +.I Amode +determines the mode of look up, and must be one of the constants below: +.TF Aaccess +.PD +.TP +.B Aaccess +Access file for information, as in the stat command or call. +.TP +.B Atodir +Access file as directory (the +.B CHDIR +bit of its +.B qid.path +must be set). +.TP +.B Aopen +Access for I/O. +.TP +.B Amount +Access directory to be mounted upon. +.TP +.B Acreate +File is to be created. +.PP +If +.I amode +is +.B Aopen +or +.BR Acreate , +.I omode +should be a mode suitable for +.IR sys-open (2); +if +.BR Acreate , +.I perm +should be valid file permissions. +In all other cases, +.I omode +and +.I perm +can be zero. +.PP +.I Cclose +decrements the reference count on +.IR c ; +if no further references remain, it +calls the corresponding device's +.B Dev.close +to close the channel, and frees +.IR c . +.SH DIAGNOSTICS +Most functions call +.IR error (10.2) +on any sort of error. +.SH SOURCE +.B /os/port/chan.c +.br +.B /emu/port/chan.c +.SH SEE ALSO +.IR ref (10.2) |