Desktop/xinu_mips-1.0.2.tar/xinu_mips-1.0.2/tty/ttyRead.c

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/* Embedded XINU, Copyright (C) 2007.  All rights reserved. */

#include <kernel.h>
#include <device.h>
#include <tty.h>

devcall ttyRead(device *pdev, char *buf, ushort len)
{
        struct tty *ptty;
        device     *phw;
        long       c = 0;
        ushort     count = 0;

        /* Setup and error check pointers to structures */
        ptty = (struct tty *)pdev->controlblk;
        ASSERT((NULL != ptty) && (TTY_STATE_ALLOC == ptty->state));

        phw = ptty->tty_phw;
        ASSERT(NULL != phw);

        /* Check for EOF */
        if (ptty->iflags & TTY_IFLAG_EOF)
        {
                return EOF;
        }

        /* If the tty's input buffer is empty, read the next line   */ 
    /*   from the underlying device into the tty's input buffer */
        if (ptty->icount == 0)
    {
                /* Read characters from the underlying device while there */
                /*   is space in the tty's input buffer and a CR, LF, or  */
        /*   EOT (Ctrl+D) character  has not been encountered     */
                while (ptty->icount < TTY_IBLEN)
                {
                        /* Read character from underlying device */
                        if (SYSERR == (c = (*phw->getc)(phw))) { break; }

                        /* If not in RAW mode, then 'cook' special characters */
                        if (!(ptty->iflags & TTY_IFLAG_RAW))
                        {
                                /* Cook backspace and delete */
                                if (('\b' == c)
                                        || (0x7F == c))
                                {
                                        if (ptty->icount > 0)
                                        { 
                                                ptty->icount--;
                                                if (ptty->iflags & TTY_IFLAG_ECHO)
                                                { ttyPutChar(ptty->tty_dev, c); }
                                        }
                                        continue;
                                }

                                /* Drop escape sequences */
                                if (0x1B == c)
                                {
                                        if (SYSERR == (c = (*phw->getc)(phw))) { break; }
                                        if (SYSERR == (c = (*phw->getc)(phw))) { break; }
                                        continue;
                                }

                                /* Drop null characters */
                                if ('\0' == c)
                                { continue; }
                        }

                        /* Add character to input buffer */
                        ptty->inbuf[(ptty->istart + ptty->icount) % TTY_IBLEN] = c;
                        ptty->icount++;

                        /* If echo is enabled, echo the character */
                        if (ptty->iflags & TTY_IFLAG_ECHO)
                        { ttyPutChar(ptty->tty_dev, c); }

                        /* Stop reading into input buffer if CR, LF, or end of file */
                        if (('\r' == c) 
                                || ('\n' == c)
                                || (0x04 == c))
                    { break; }
                }
        }

        ptty->iflags &= ~TTY_IFLAG_CBREAK; /* Clear break (Control-C) flag */
        ptty->iflags &= ~TTY_IFLAG_EOF;    /* Clear EOF  (Control-D) flag  */

  /* Satisfy read request from input buffer */
  while ((count < len)  && (ptty->icount > 0))
  {
      /* Check for Break character (Control-C) and set flag */
      if (0x03 == c)
          { ptty->iflags |= TTY_IFLAG_CBREAK; }

      /* Check for EOF character (Control-D) and set flag */
      if (0x04 == c)
          {
                  ptty->iflags |= TTY_IFLAG_EOF;
                  len = count;
          }
      
      /* Read from input buffer into user buffer; Preserve circular buffer */
      *buf++ = ptty->inbuf[ptty->istart];
      ptty->icount--;
      ptty->istart = (ptty->istart + 1) % TTY_IBLEN;
      count++;
  }

  return count;
}

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