Add kmscon_char type

Every cell of the console contains one single printable character. We want to be
Unicode compatible so we must support combined characters. Hence, each cell
consists of a UTF-8 string that can be drawn by pango as a single glyph.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>

src/console.h

@@ -14,10 +14,22 @@
  * of it.
  */
 
+#include <inttypes.h>
 #include <stdlib.h>
 
+struct kmscon_char;
 struct kmscon_console;
 
+/* single printable characters */
+
+int kmscon_char_new(struct kmscon_char **out);
+void kmscon_char_free(struct kmscon_char *ch);
+
+int kmscon_char_set_u8(struct kmscon_char *ch, const char *str, size_t len);
+const char *kmscon_char_get_u8(const struct kmscon_char *ch);
+size_t kmscon_char_get_len(const struct kmscon_char *ch);
+int kmscon_char_append_u8(struct kmscon_char *ch, const char *str, size_t len);
+
 /* console objects */
 
 int kmscon_console_new(struct kmscon_console **out);

src/console_char.c

@@ -0,0 +1,132 @@
+/*
+ * kmscon - Console Characters
+ * Written 2011 by David Herrmann <dh.herrmann@googlemail.com>
+ */
+
+/*
+ * Console Characters
+ * A console always has a fixed width and height measured in number of
+ * characters. This interfaces describes a single character.
+ *
+ * To be Unicode compatible, the most straightforward way would be using a UCS
+ * number for each character and printing them. However, Unicode allows
+ * combining marks, that is, a single printable character is constructed of
+ * multiple characters. We support this by allowing to append characters to an
+ * existing character. This should only be used with combining chars, though.
+ * Otherwise you end up with multiple printable characters in a cell and the
+ * output may get corrupted.
+ *
+ * We store each character (sequence) as UTF8 string because the pango library
+ * accepts only UTF8. Hence, we avoid conversion to UCS or wide-characters.
+ */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "console.h"
+
+/* maximum size of a single character */
+#define KMSCON_CHAR_SIZE 6
+
+struct kmscon_char {
+	char *buf;
+	size_t size;
+	size_t len;
+};
+
+int kmscon_char_new(struct kmscon_char **out)
+{
+	struct kmscon_char *ch;
+
+	if (!out)
+		return -EINVAL;
+
+	ch = malloc(sizeof(*ch));
+	if (!ch)
+		return -ENOMEM;
+
+	memset(ch, 0, sizeof(*ch));
+
+	ch->size = KMSCON_CHAR_SIZE;
+	ch->buf = malloc(ch->size);
+	if (!ch->buf) {
+		free(ch);
+		return -ENOMEM;
+	}
+
+	memset(ch->buf, 0, ch->size);
+
+	*out = ch;
+	return 0;
+}
+
+void kmscon_char_free(struct kmscon_char *ch)
+{
+	if (!ch)
+		return;
+
+	free(ch->buf);
+	free(ch);
+}
+
+int kmscon_char_set_u8(struct kmscon_char *ch, const char *str, size_t len)
+{
+	char *buf;
+
+	if (!ch)
+		return -EINVAL;
+
+	if (ch->size < len) {
+		buf = realloc(ch->buf, len);
+		if (!buf)
+			return -ENOMEM;
+		ch->buf = buf;
+		ch->size = len;
+	}
+
+	memcpy(ch->buf, str, len);
+	ch->len = len;
+
+	return 0;
+}
+
+const char *kmscon_char_get_u8(const struct kmscon_char *ch)
+{
+	if (!ch || !ch->len)
+		return NULL;
+
+	return ch->buf;
+}
+
+size_t kmscon_char_get_len(const struct kmscon_char *ch)
+{
+	if (!ch)
+		return 0;
+
+	return ch->len;
+}
+
+int kmscon_char_append_u8(struct kmscon_char *ch, const char *str, size_t len)
+{
+	char *buf;
+	size_t nlen;
+
+	if (!ch)
+		return -EINVAL;
+
+	nlen = ch->len + len;
+
+	if (ch->size < nlen) {
+		buf = realloc(ch->buf, nlen);
+		if (!buf)
+			return -EINVAL;
+		ch->buf = buf;
+		ch->size = nlen;
+	}
+
+	memcpy(&ch->buf[ch->len], str, len);
+	ch->len += len;
+
+	return 0;
+}