lib/mbsedit: add simple buffer editor

Signed-off-by: Karel Zak <kzak@redhat.com>

include/mbsedit.h

@@ -0,0 +1,32 @@
+#ifndef UTIL_LINUX_MBSEDIT_H
+# define UTIL_LINUX_MBSEDIT_H
+
+#include "mbsalign.h"
+#include "widechar.h"
+
+struct mbs_editor {
+	char	*buf;		/* buffer */
+	size_t	max_bytes;	/* size of the buffer */
+	size_t	max_cells;	/* maximal allowed number of cells */
+	size_t	cur_cells;	/* number of cells to print the buffer */
+	size_t  cur_bytes;	/* number of chars in bytes */
+	size_t  cursor;		/* cursor position in bytes */
+	size_t  cursor_cells;	/* cursor position in cells */
+};
+
+enum {
+	MBS_EDIT_LEFT,
+	MBS_EDIT_RIGHT,
+	MBS_EDIT_END,
+	MBS_EDIT_HOME
+};
+
+struct mbs_editor *mbs_new_edit(char *buf, size_t bufsz, size_t ncells);
+char *mbs_free_edit(struct mbs_editor *edit);
+
+int mbs_edit_goto(struct mbs_editor *edit, int where);
+int mbs_edit_delete(struct mbs_editor *edit);
+int mbs_edit_backspace(struct mbs_editor *edit);
+int mbs_edit_insert(struct mbs_editor *edit, wint_t c);
+
+#endif /* UTIL_LINUX_MBSEDIT_H */

lib/Makemodule.am

@@ -13,6 +13,7 @@ libcommon_la_SOURCES = \
 	lib/mangle.c \
 	lib/match.c \
 	lib/mbsalign.c \
+	lib/mbsedit.c\
 	lib/md5.c \
 	lib/pager.c \
 	lib/path.c \

lib/mbsedit.c

@@ -0,0 +1,222 @@
+/*
+ * Very simple multibyte buffer editor. Allows to maintaine the current
+ * possition in the string, add and remove chars on the current possition.
+ *
+ * This file may be distributed under the terms of the
+ * GNU Lesser General Public License.
+ *
+ * Copyright (C) 2017 Karel Zak <kzak@redhat.com>
+ */
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <stdio.h>
+
+#include "mbsalign.h"
+#include "mbsedit.h"
+
+struct mbs_editor *mbs_new_edit(char *buf, size_t bufsz, size_t ncells)
+{
+	struct mbs_editor *edit = calloc(1, sizeof(*edit));
+
+	if (edit) {
+		edit->buf = buf;
+		edit->max_bytes = bufsz;
+		edit->max_cells = ncells;
+		edit->cur_cells = mbs_safe_width(buf);
+		edit->cur_bytes = strlen(buf);
+	}
+	return edit;
+}
+
+char *mbs_free_edit(struct mbs_editor *edit)
+{
+	char *ret = edit ? edit->buf : NULL;
+
+	free(edit);
+	return ret;
+}
+
+static size_t mbs_next(const char *str, size_t *ncells)
+{
+#ifdef HAVE_WIDECHAR
+	wchar_t wc;
+	size_t n = 0;
+
+	if (!str || !*str)
+		return 0;
+
+	n = mbrtowc(&wc, str, MB_CUR_MAX, NULL);
+	*ncells = wcwidth(wc);
+	return n;
+#else
+	if (!str || !*str)
+		return 0;
+	*ncells = 1;
+	return 1;
+#endif
+}
+
+static size_t mbs_prev(const char *start, const char *end, size_t *ncells)
+{
+#ifdef HAVE_WIDECHAR
+	wchar_t wc = 0;
+	const char *p, *prev;
+	size_t n = 0;
+
+	if (!start || !end || start == end || !*start)
+		return 0;
+
+	prev = p = start;
+	while (p < end) {
+		n = mbrtowc(&wc, p, MB_CUR_MAX, NULL);
+		prev = p;
+
+		if (n == (size_t) -1 || n == (size_t) -2)
+			p++;
+		else
+			p += n;
+	}
+
+	if (prev == end)
+		return 0;
+	*ncells = wcwidth(wc);
+	return n;
+#else
+	if (!start || !end || start == end || !*start)
+		return 0;
+	*ncells = 1;
+	return 1;
+#endif
+}
+
+int mbs_edit_goto(struct mbs_editor *edit, int where)
+{
+	switch (where) {
+	case MBS_EDIT_LEFT:
+		if (edit->cursor == 0)
+			return 1;
+		else {
+			size_t n, cells;
+			n = mbs_prev(edit->buf, edit->buf + edit->cursor, &cells);
+			if (n) {
+				edit->cursor -= n;
+				edit->cursor_cells -= cells;
+			}
+		}
+		break;
+	case MBS_EDIT_RIGHT:
+		if (edit->cursor_cells >= edit->cur_cells)
+			return 1;
+		else {
+			size_t n, cells;
+			n = mbs_next(edit->buf + edit->cursor, &cells);
+			if (n) {
+				edit->cursor += n;
+				edit->cursor_cells += cells;
+			}
+		}
+		break;
+	case MBS_EDIT_HOME:
+		edit->cursor = 0;
+		edit->cursor_cells = 0;
+		break;
+	case MBS_EDIT_END:
+		edit->cursor = edit->cur_bytes;
+		edit->cursor_cells = edit->cur_cells;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/* Remove next MB from @str, returns number of removed bytes */
+static size_t remove_next(char *str, size_t *ncells)
+{
+	/* all in bytes! */
+	size_t bytes, move_bytes, n;
+
+	n          = mbs_next(str, ncells);
+	bytes      = strlen(str);
+	move_bytes = bytes - n;
+
+	memmove(str, str + n, move_bytes);
+	str[bytes - n] = '\0';
+	return n;
+}
+
+static size_t mbs_insert(char *str, wint_t c, size_t *ncells)
+{
+	/* all in bytes! */
+	size_t n = 1, bytes;
+	char *in = (char *) &c;
+
+#ifdef HAVE_WIDECHAR
+	wchar_t wc = (wchar_t) c;
+	char in_buf[MB_CUR_MAX];
+
+	n = wctomb(in_buf, wc);
+	*ncells = wcwidth(wc);
+	in = in_buf;
+#else
+	*ncells = 1;
+#endif
+	bytes       = strlen(str);
+
+	memmove(str + n, str, bytes);
+	memcpy(str, in, n);
+	str[bytes + n] = '\0';
+	return n;
+}
+
+static int mbs_edit_remove(struct mbs_editor *edit)
+{
+	size_t n, ncells;
+
+	if (edit->cur_cells == 0 || edit->cursor >= edit->cur_bytes)
+		return 1;
+
+	n = remove_next(edit->buf + edit->cursor, &ncells);
+	if (n == (size_t)-1)
+		return 1;
+
+	edit->cur_bytes -= n;
+	edit->cur_cells = mbs_safe_width(edit->buf);
+	return 0;
+}
+
+int mbs_edit_delete(struct mbs_editor *edit)
+{
+	if (edit->cursor >= edit->cur_bytes
+	    && mbs_edit_goto(edit, MBS_EDIT_LEFT) == 1)
+		return 1;
+
+	return mbs_edit_remove(edit);
+}
+
+int mbs_edit_backspace(struct mbs_editor *edit)
+{
+	if (mbs_edit_goto(edit, MBS_EDIT_LEFT) == 0)
+		return mbs_edit_remove(edit);
+	return 1;
+}
+
+int mbs_edit_insert(struct mbs_editor *edit, wint_t c)
+{
+	size_t n, ncells;
+
+	if (edit->cur_bytes + MB_CUR_MAX > edit->max_bytes)
+		return 1;
+
+	n = mbs_insert(edit->buf + edit->cursor, c, &ncells);
+	if (n == (size_t)-1)
+		return 1;
+
+	edit->cursor += n;
+	edit->cursor_cells += ncells;
+	edit->cur_bytes += n;
+	edit->cur_cells = mbs_safe_width(edit->buf);
+	return 0;
+}