getchar.c

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/*                      - GETCHAR.C -

  The ANSI "getchar" function delivered here is supposed to be tailored
  for the actual target hardware.  This version of getchar contains a simple
  line-editor that can back-space and delete  (In_DELETE), skip line and
  start over again (In_SKIP), as well as recognize end of file (In_EOF).

  $Revision: 1.3 $

   Copyright 1986 - 1999 IAR Systems. All rights reserved.
*/

#include "stdio.h"

extern char _low_level_get(void);       /* Read one char from I/O */
                                        /* Should be supplied by user */

static void put_message(char *s)
{
  while (*s)
    putchar(*s++);
}


#define LINE_LENGTH 80          /* Change if you need */

#define In_DELETE 0x7F          /* ASCII <DEL> */
#define In_EOL '\r'             /* ASCII <CR> */
#define In_SKIP '\3'            /* ASCII control-C */
#define In_EOF '\x1A'           /* ASCII control-Z */

#define Out_DELETE "\x8 \x8"    /* VT100 backspace and clear */
#define Out_SKIP "^C\n"         /* ^C and new line */
#define Out_EOF "^Z"            /* ^Z and return EOF */

int getchar(void)
{
  static char io_buffer[LINE_LENGTH + 2];     /* Where to put chars */
  static int ptr;                             /* Pointer in buffer */
  char c;

  for (;;)
  {
    if (io_buffer[ptr])
      return (io_buffer[ptr++]);
    ptr = 0;
    for (;;)
    {
      if ((c = _low_level_get()) == In_EOF && !ptr)
      {
        put_message(Out_EOF);
        return EOF;
      }
      if (c == In_DELETE)
      {
        if (ptr)
        {
          ptr--;
          put_message(Out_DELETE);
        }
      }
      else if (c == In_SKIP)
      {
        put_message(Out_SKIP);
        ptr = LINE_LENGTH + 1;  /* Where there always is a zero... */
        break;
      }
      else if (c == In_EOL)
      {
        putchar(io_buffer[ptr++] = '\n');
        io_buffer[ptr] = 0;
        ptr = 0;
        break;
      }
      else if (ptr < LINE_LENGTH)
      {
        if (c >= ' ')
        {
          putchar(io_buffer[ptr++] = c);
        }
      }
      else
      {
        putchar('\7');
      }
    }
  }
}