Added generic line-buffering code (a la stdio)

src/core/linebuf.c

@@ -0,0 +1,136 @@
+/*
+ * 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>
+
+/**
+ * Line terminators
+ *
+ * These values are used in the @c skip_terminators bitmask.
+ */
+enum line_terminators {
+	TERM_CR = 1,
+	TERM_NL = 2,
+	TERM_NUL = 4,
+};
+
+/**
+ * Get terminator ID corresponding to character
+ *
+ * @v character		Character
+ * @ret terminator_id	Terminator ID, or -1
+ */
+static int terminator_id ( unsigned int character ) {
+	switch ( character ) {
+	case '\r':
+		return TERM_CR;
+	case '\n':
+		return TERM_NL;
+	case '\0':
+		return TERM_NUL;
+	default:
+		return -1;
+	}
+}
+
+/**
+ * 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;
+}
+
+/**
+ * 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 buffered		Amount of data consumed and added to the buffer
+ * @ret <0			Out of memory
+ * 
+ * If line_buffer() does not consume the entirety of the new data
+ * (i.e. if @c buffered is not equal to @c len), 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()).
+ *
+ * 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 ) {
+	size_t consume = 0;
+	size_t copy = 0;
+	size_t new_len;
+	char *new_data;
+	int terminator;
+
+	/* First, handle the termination of the previous line */
+	if ( linebuf->skip_terminators ) {
+		/* Free buffered string */
+		empty_line_buffer ( linebuf );
+		/* Skip over any terminators from the end of a previous line */
+		for ( ; consume < len ; consume++ ) {
+			terminator = terminator_id ( data[consume] );
+			if ( ( terminator < 0 ) ||
+			     ! ( linebuf->skip_terminators & terminator ) ) {
+				linebuf->skip_terminators = 0;
+				break;
+			}
+			linebuf->skip_terminators &= ~terminator;
+		}
+	}
+
+	/* Scan up to the next terminator, if any */
+	for ( ; consume < len ; consume++, copy++ ) {
+		if ( terminator_id ( data[consume] ) >= 0 ) {
+			linebuf->skip_terminators = -1U;
+			break;
+		}
+	}
+
+	/* Reallocate data buffer and copy in new data */
+	new_len = ( linebuf->len + copy );
+	new_data = realloc ( linebuf->data, ( new_len + 1 ) );
+	if ( ! new_data )
+		return -ENOMEM;
+	memcpy ( ( new_data + linebuf->len ), ( data + consume - copy ),
+		 copy );
+	new_data[new_len] = '\0';
+	linebuf->data = new_data;
+	linebuf->len = new_len;
+	return consume;
+}

src/include/gpxe/linebuf.h

@@ -0,0 +1,37 @@
+#ifndef _GPXE_LINEBUF_H
+#define _GPXE_LINEBUF_H
+
+/** @file
+ *
+ * Line buffering
+ *
+ */
+
+#include <stdint.h>
+#include <stddef.h>
+
+/** A line buffer */
+struct line_buffer {
+	/** Current data in the buffer */
+	char *data;
+	/** Length of current data */
+	size_t len;
+	/** Bitmask of terminating characters to skip over */
+	unsigned int skip_terminators;
+};
+
+/**
+ * Retrieve buffered-up line
+ *
+ * @v linebuf		Line buffer
+ * @ret line		Buffered line, or NULL if no line present
+ */
+static inline char * buffered_line ( struct line_buffer *linebuf ) {
+	return linebuf->data;
+}
+
+extern int line_buffer ( struct line_buffer *linebuf, const char *data,
+			 size_t len );
+extern void empty_line_buffer ( struct line_buffer *linebuf );
+
+#endif /* _GPXE_LINEBUF_H */

src/tests/linebuf_test.c

@@ -0,0 +1,27 @@
+#include <stdint.h>
+#include <string.h>
+#include <vsprintf.h>
+#include <gpxe/linebuf.h>
+
+static const char data1[] = 
+"Hello world\r\n"
+"This is a particularly mean set of lines\n"
+"with a mixture of terminators\r\r\n"
+"There should be exactly one blank line above\n"
+"and this line should never appear at all since it has no terminator";
+
+void linebuf_test ( void ) {
+	struct line_buffer linebuf;
+	const char *data = data1;
+	size_t len = ( sizeof ( data1 ) - 1 /* be mean; strip the NUL */ );
+	size_t buffered;
+
+	memset ( &linebuf, 0, sizeof ( linebuf ) );
+	while ( ( buffered = line_buffer ( &linebuf, data, len ) ) != len ) {
+		printf ( "\"%s\"\n", buffered_line ( &linebuf ) );
+		data += buffered;
+		len -= buffered;
+	}
+
+	empty_line_buffer ( &linebuf );
+}