source: bootcd/isolinux/syslinux-6.03/gpxe/src/core/linebuf.c

/*
 * 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_LICENCE ( GPL2_OR_LATER );

/**
 * @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 len                     Consumed length, or negative error number
 *
 * After calling line_buffer(), use buffered_line() to determine
 * whether or not a complete line is available.  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()).
 *
 * Note that line buffers use dynamically allocated storage; you
 * should call empty_line_buffer() before freeing a @c struct @c
 * line_buffer.
 */
ssize_t 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;

        /* 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 consume;
}