lflseek.c File Reference

#include <xinu.h>

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Functions
devcall	lflseek (struct dentry *devptr, uint32 offset)

Function Documentation

lflseek()

devcall lflseek	(	struct dentry *	devptr,
		uint32	offset
	)

Definition at line 9 of file lflseek.c.

References dentry::dvminor, ldentry::ld_size, LF_BLKSIZ, LF_USED, lflcblk::lfbyte, lflcblk::lfdblock, lflcblk::lfdirptr, lfltab, lflcblk::lfmutex, lflcblk::lfpos, lflcblk::lfstate, OK, signal(), SYSERR, and wait().

{
    struct  lflcblk *lfptr;     /* Ptr to open file table entry */

    /* If file is not open, return an error */

    lfptr = &lfltab[devptr->dvminor];
    wait(lfptr->lfmutex);
    if (lfptr->lfstate != LF_USED) {
        signal(lfptr->lfmutex);
        return SYSERR;
    }

    /* Verify offset is within current file size */

    if (offset > lfptr->lfdirptr->ld_size) {
        signal(lfptr->lfmutex);
        return SYSERR;
    }

    /* Record new offset and invalidate byte pointer (i.e., force   */
    /*   the index and data blocks to be replaced if a successive   */
    /*   call is made to read or write)             */

    lfptr->lfpos = offset;
    lfptr->lfbyte = &lfptr->lfdblock[LF_BLKSIZ];

    signal(lfptr->lfmutex);
    return OK;
}

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