/*
 * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/**
 * @file
 *
 * Line buffering
 *
 */

#include <stdint.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <gpxe/linebuf.h>

/**
 * Retrieve buffered-up line
 *
 * @v linebuf		Line buffer
 * @ret line		Buffered line, or NULL if no line ready to read
 */
char * buffered_line ( struct line_buffer *linebuf ) {
	return ( linebuf->ready ? linebuf->data : NULL );
}

/**
 * Discard line buffer contents
 *
 * @v linebuf		Line buffer
 */
void empty_line_buffer ( struct line_buffer *linebuf ) {
	free ( linebuf->data );
	linebuf->data = NULL;
	linebuf->len = 0;
	linebuf->ready = 0;
}

/**
 * Buffer up received data by lines
 *
 * @v linebuf			Line buffer
 * @v data			New data to add
 * @v len			Length of new data to add
 * @ret rc			Return status code
 * 
 * If line_buffer() returns >0, then an end of line has been reached
 * and the buffered-up line can be obtained from buffered_line().
 * Carriage returns and newlines will have been stripped, and the line
 * will be NUL-terminated.  This buffered line is valid only until the
 * next call to line_buffer() (or to empty_line_buffer()).
 *
 * @c data and @c len will be updated to reflect the data consumed by
 * line_buffer().
 *
 * Note that line buffers use dynamically allocated storage; you
 * should call empty_line_buffer() before freeing a @c struct @c
 * line_buffer.
 */
int line_buffer ( struct line_buffer *linebuf,
		  const char **data, size_t *len ) {
	const char *eol;
	size_t consume;
	size_t new_len;
	char *new_data;

	/* Free any completed line from previous iteration */
	if ( linebuf->ready )
		empty_line_buffer ( linebuf );

	/* Search for line terminator */
	if ( ( eol = memchr ( *data, '\n', *len ) ) ) {
		consume = ( eol - *data + 1 );
	} else {
		consume = *len;
	}

	/* Reallocate data buffer and copy in new data */
	new_len = ( linebuf->len + consume );
	new_data = realloc ( linebuf->data, ( new_len + 1 ) );
	if ( ! new_data )
		return -ENOMEM;
	memcpy ( ( new_data + linebuf->len ), *data, consume );
	new_data[new_len] = '\0';
	linebuf->data = new_data;
	linebuf->len = new_len;

	/* Update data and len */
	*data += consume;
	*len -= consume;

	/* If we have reached end of line, trim the line and mark as ready */
	if ( eol ) {
		linebuf->data[--linebuf->len] = '\0'; /* trim NL */
		if ( linebuf->data[linebuf->len - 1] == '\r' )
			linebuf->data[--linebuf->len] = '\0'; /* trim CR */
		linebuf->ready = 1;
	}

	return 0;
}