a_localio.c

在freescale 的ne64上开发的源代码

#include "snmptype.h"
#include "a_localio.h"
/****************************************************************************
Lcl_Open -- Open a buffer for use as a local I/O stream
Parameters: LCL_FILE *lfile
            _UINT8  *buffer
            _UINT16 nbytes
Returns: (LCL_FILE *) if sucessful, (LCL_FILE *)0 if unsucessful.
****************************************************************************/
LCL_FILE *Lcl_Open(LCL_FILE * lfile, _UINT8 * buff, _UINT16 nbytes)
{
	if(lfile == 0)
		return 0;
	lfile->lcl_flags = 0;
	lfile->lbuf_start = buff;
	lfile->lbuf_next = buff;
	lfile->lbuf_end = (_UINT8 *) (buff + nbytes);
	return (lfile);
}

/****************************************************************************
Lcl_Peekc -- Peek at a character from a local I/O stream, the seek poINT32er is not advanced.
Parameters: LCL_FILE *      lfile
Returns: If sucessful: the character read, but in INT32eger format
	If unsucessful: -1
****************************************************************************/
_INT16 Lcl_Peekc(LCL_FILE * lfile)
{
	if(lfile->lcl_flags & LCL_EOF)
		return -1;
	if(lfile->lbuf_next < lfile->lbuf_end)
		return (*(lfile->lbuf_next));
	else
	{
		lfile->lcl_flags |= LCL_EOF;
		return -1;
	}
}
/****************************************************************************
Lcl_Read -- Read a set of characters from a local I/O stream.
Parameters:
  LCL_FILE *      lfile
  _UINT8  *      ubuf
  _UINT16       nbytes
Returns: The number of bytes actually read.
****************************************************************************/
_UINT16 Lcl_Read(LCL_FILE * lfile, _UINT8 * ubuf, _UINT16 nbytes)
{
	/* This is a quick implementation, to be replaced later */
	_UINT16 orig_nbytes = nbytes;
	_UINT8 c;

	while(nbytes > 0)
	{
		c = (_UINT8) Lcl_Getc(lfile);
		if(Lcl_Eof(lfile))
			break;
		*ubuf++ = c;
		--nbytes;
	}
	return (orig_nbytes - nbytes);
}

/****************************************************************************
Lcl_Seek -- Move the seek poINT32er to a give position in the local I/O buffer.
Parameters:
  LCL_FILE *      lfile
  _UINT16       offset
  _INT32             whence:
  0 to set poINT32er to offset bytes from the start
  1 to move poINT32er by offset bytes
  2 to set poINT32er to offset bytes from the end
Returns: 0 if sucessful, -1 if not.
Note: The "end" position is the byte AFTER the last one in the buffer
	  containing data.  Thus, a Lcl_Seek(.., 0, 2) will leave the caller at
	  the end-of-file.  The last byte is reached by Lcl_Seek(.., 1, 2).
****************************************************************************/
_INT16 Lcl_Seek(LCL_FILE * lfile, _UINT16 offset, _INT16 whence)
{
	_UINT8 *next;

	switch (whence)
	{
	case 0:
		next = (_UINT8 *) (lfile->lbuf_start + offset);
		break;
	case 1:
		next = (_UINT8 *) (lfile->lbuf_next + offset);
		break;
	case 2:
		next = (_UINT8 *) (lfile->lbuf_end - offset);
		break;
	default:
		return -1;
	}

	if((next < lfile->lbuf_start) || (next > lfile->lbuf_end))
		return -1;

	if(next < lfile->lbuf_end)
		lfile->lcl_flags &= ~LCL_EOF;
	lfile->lbuf_next = next;
	return 0;
}