source: buchla-68k/libcio/read.c@ c59409e

/*
   =============================================================================
        read.c -- file read functions for the C I/O Library
        Version 9 -- 1987-10-28 -- D.N. Lynx Crowe

        int
        read(fd, buff, len)
        char *buff;

                Reads 'len' bytes from file 'fd' into 'buff'.
                Returns FAILURE (-1) for errors, number of bytes read
                if successful.

        int
        _getsec(fp, buf, len)
        register struct fcb *fp;
        char *buf;
        unsigned len;

                Gets 'len' bytes into 'buf' from file 'fp'.
                Returns FAILURE (-1) for errors, SUCCESS (0) if successful.

        int
        _filerd(fp, buffer, len)
        register struct fcb *fp;
        char *buffer;
        unsigned len;

                Reads 'len' bytes into 'buffer' from 'fp'.
                Returns FAILURE (-1) for errors, number of bytes read
                if successful.

   =============================================================================
*/

#define DEBUGIT         0

#include "ram.h"

static int16_t (*t_read[])(io_arg arg, void *buff, int16_t len) = {

        _badfio,        /* 0 - invalid type */
        _filerd,        /* 1 - disk file read */
        _conin          /* 2 - console read */
};

/*
   =============================================================================
        read(fd, buff, len) -- Reads 'len' bytes from file 'fd' into 'buff'.
        Returns FAILURE (-1) for errors, number of bytes read if successful.
   =============================================================================
*/

int16_t read(int16_t fd, void *buff, int16_t len)
{
        register struct channel *chp;

        if (fd < 0 OR fd > MAXCHAN) {   /* check fd range */

                errno = EBADF;  /* bad fd */
                return(FAILURE);
        }

        chp = &chantab[fd];     /* point at the channel table */
        return((*t_read[chp->c_read])(chp->c_arg, buff, len));  /* do the read */
}

/*
   =============================================================================
        _getsec(fp, buf, len) -- Gets 'len' bytes into 'buf' from file 'fp'.
        Returns FAILURE (-1) for errors, SUCCESS (0) if successful.
   =============================================================================
*/

int16_t _getsec(struct fcb *fp, void *buf, int16_t len)
{
        if ((errno = ReadRN(fp, Wrkbuf)) NE 0)  /* get current sector */
                return(FAILURE);

        memcpy(buf, Wrkbuf + fp->offset, len);  /* move what we need */

        if ((fp->offset = (fp->offset + len) & (BPSEC - 1)) EQ 0) {

                ++fp->curlsn;                   /* advance the sector number */

                if (_seek(fp) < 0)              /* seek to the next sector */
                        return(FAILURE);
        }

        return(SUCCESS);                        /* return:  all bytes read */
}

/*
   =============================================================================
        _filerd(fp, buffer, len) -- Reads 'len' bytes into 'buffer' from 'fp'.
        Returns FAILURE (-1) for errors, number of bytes read if successful.
   =============================================================================
*/

int16_t _filerd(io_arg arg, void *buffer, int16_t len)
{
        struct fcb *fp;
        int8_t *buffer8;
        register int16_t l;
        register int16_t j, k;
        register int32_t cpos, npos;

        fp = (struct fcb *)arg;
        buffer8 = buffer;

        l = 0;
        cpos = fp->offset + ((int32_t)fp->curlsn << FILESHFT);
        npos = cpos + len;

#if     DEBUGIT
        if (fsdebug)
                printf("_filerd():  len=%u, curpos=%ld, newpos=%ld, curlen=%ld\n",
                        len, cpos, npos, fp->curlen);
#endif

        if (npos GT fp->curlen) {

                len = (int16_t)(fp->curlen - cpos);

#if     DEBUGIT
        if (fsdebug)
                printf("_filerd():  len adjusted to %u\n", len);
#endif
        }

        if (fp->offset) {       /* see if we start in the middle of a sector */

                if ((l = BPSEC - fp->offset) > len)     /* see what we need */
                        l = len;

                if (_getsec(fp, buffer8, l))    /* read what we can */
                        return(len);    /* return if ERROR */
        }

        if ((k = (len - l) / BPSEC)) {          /* see what we still need */
                if ((j = blkrd(fp, buffer8 + l, k)) NE 0)
                        return((k - j) * BPSEC + l);    /* return bytes read */
        }

        l += k * BPSEC;                 /* adjust l by what we just read */

        if (l < len)    /* see if we still need a partial sector */
                if (_getsec(fp, buffer8 + l, len - l))  /* read partial sector */
                        return(l);              /* return if ERROR or EOF */

        return(len);                            /* return - got the whole thing */
}