lflgetc.c File Reference

#include <xinu.h>

Include dependency graph for lflgetc.c:

Go to the source code of this file.

Functions
devcall	lflgetc (struct dentry *devptr)

Function Documentation

lflgetc()

devcall lflgetc

(

struct dentry *

devptr

)

Definition at line 9 of file lflgetc.c.

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

Referenced by lflread().

{
    struct  lflcblk *lfptr;     /* Ptr to open file table entry */
    struct  ldentry *ldptr;     /* Ptr to file's entry in the   */
                    /*   in-memory directory    */
    int32   onebyte;        /* Next data byte in the file   */

    /* Obtain exclusive use of the file */

    lfptr = &lfltab[devptr->dvminor];
    wait(lfptr->lfmutex);

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

    if (lfptr->lfstate != LF_USED) {
        signal(lfptr->lfmutex);
        return SYSERR;
    }

    /* Return EOF for any attempt to read beyond the end-of-file */

    ldptr = lfptr->lfdirptr;
    if (lfptr->lfpos >= ldptr->ld_size) {
        signal(lfptr->lfmutex);
        return EOF;
    }

    /* If byte pointer is beyond the current data block, set up */
    /*  a new data block                    */

    if (lfptr->lfbyte >= &lfptr->lfdblock[LF_BLKSIZ]) {
        lfsetup(lfptr);
    }

    /* Extract the next byte from block, update file position, and  */
    /*  return the byte to the caller               */

    onebyte = 0xff & *lfptr->lfbyte++;
    lfptr->lfpos++;
    signal(lfptr->lfmutex);
    return onebyte;
}

Here is the call graph for this function:

Here is the caller graph for this function: