lib/printbuf: prt_str_indented()

This adds a new helper, prt_str_indented(), which handles embedded
control characters by calling prt_newline(), prt_tab(), and
prt_tab_rjust() as needed.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

2 files changed, 88 insertions, 17 deletions

diff --git a/include/linux/printbuf.h b/include/linux/printbuf.h
index 861c5d75f852..eb2edb86b22c 100644
--- a/include/linux/printbuf.h
+++ b/include/linux/printbuf.h
@@ -99,6 +99,7 @@ void printbuf_indent_add(struct printbuf *, unsigned);
 void printbuf_indent_sub(struct printbuf *, unsigned);
 void prt_tab(struct printbuf *);
 void prt_tab_rjust(struct printbuf *);
+void prt_bytes_indented(struct printbuf *, const char *, unsigned);
 void prt_human_readable_u64(struct printbuf *, u64);
 void prt_human_readable_s64(struct printbuf *, s64);
 void prt_units_u64(struct printbuf *, u64);
@@ -211,6 +212,11 @@ static inline void prt_str(struct printbuf *out, const char *str)
 	prt_bytes(out, str, strlen(str));
 }
 
+static inline void prt_str_indented(struct printbuf *out, const char *str)
+{
+	prt_bytes_indented(out, str, strlen(str));
+}
+
 static inline void prt_hex_byte(struct printbuf *out, u8 byte)
 {
 	printbuf_make_room(out, 2);
diff --git a/lib/printbuf.c b/lib/printbuf.c
index 047470025748..3fbb74754b48 100644
--- a/lib/printbuf.c
+++ b/lib/printbuf.c
@@ -143,39 +143,40 @@ void printbuf_indent_sub(struct printbuf *buf, unsigned spaces)
 }
 EXPORT_SYMBOL(printbuf_indent_sub);
 
-/**
- * prt_tab - Advance printbuf to the next tabstop
- *
- * @buf: printbuf to control
- *
- * Advance output to the next tabstop by printing spaces.
- */
-void prt_tab(struct printbuf *out)
+static inline bool tabstop_is_set(struct printbuf *buf)
 {
-	int spaces = max_t(int, 0, out->tabstops[out->tabstop] - printbuf_linelen(out));
+	return buf->tabstop < ARRAY_SIZE(buf->tabstops) &&
+		buf->tabstops[buf->tabstop];
+}
 
-	BUG_ON(out->tabstop > ARRAY_SIZE(out->tabstops));
+static void __prt_tab(struct printbuf *out)
+{
+	int spaces = max_t(int, 0, out->tabstops[out->tabstop] - printbuf_linelen(out));
 
 	prt_chars(out, ' ', spaces);
 
 	out->last_field = out->pos;
 	out->tabstop++;
 }
-EXPORT_SYMBOL(prt_tab);
 
 /**
- * prt_tab_rjust - Advance printbuf to the next tabstop, right justifying
- * previous output
+ * prt_tab - Advance printbuf to the next tabstop
  *
  * @buf: printbuf to control
  *
- * Advance output to the next tabstop by inserting spaces immediately after the
- * previous tabstop, right justifying previously outputted text.
+ * Advance output to the next tabstop by printing spaces.
  */
-void prt_tab_rjust(struct printbuf *buf)
+void prt_tab(struct printbuf *out)
 {
-	BUG_ON(buf->tabstop > ARRAY_SIZE(buf->tabstops));
+	if (WARN_ON(!tabstop_is_set(out)))
+		return;
+
+	__prt_tab(out);
+}
+EXPORT_SYMBOL(prt_tab);
 
+static void __prt_tab_rjust(struct printbuf *buf)
+{
 	if (printbuf_linelen(buf) < buf->tabstops[buf->tabstop]) {
 		unsigned move = buf->pos - buf->last_field;
 		unsigned shift = buf->tabstops[buf->tabstop] -
@@ -199,9 +200,73 @@ void prt_tab_rjust(struct printbuf *buf)
 	buf->last_field = buf->pos;
 	buf->tabstop++;
 }
+
+/**
+ * prt_tab_rjust - Advance printbuf to the next tabstop, right justifying
+ * previous output
+ *
+ * @buf: printbuf to control
+ *
+ * Advance output to the next tabstop by inserting spaces immediately after the
+ * previous tabstop, right justifying previously outputted text.
+ */
+void prt_tab_rjust(struct printbuf *buf)
+{
+	if (WARN_ON(!tabstop_is_set(buf)))
+		return;
+
+	__prt_tab_rjust(buf);
+}
 EXPORT_SYMBOL(prt_tab_rjust);
 
 /**
+ * prt_bytes_indented - Print an array of chars, handling embedded control characters
+ *
+ * @out: printbuf to output to
+ * @str: string to print
+ * @count: number of bytes to print
+ *
+ * The following contol characters are handled as so:
+ *   \n: prt_newline	newline that obeys current indent level
+ *   \t: prt_tab	advance to next tabstop
+ *   \r: prt_tab_rjust	advance to next tabstop, with right justification
+ */
+void prt_bytes_indented(struct printbuf *out, const char *str, unsigned count)
+{
+	const char *unprinted_start = str;
+	const char *end = str + count;
+
+	while (str != end) {
+		switch (*str) {
+		case '\n':
+			prt_bytes(out, unprinted_start, str - unprinted_start);
+			unprinted_start = str + 1;
+			prt_newline(out);
+			break;
+		case '\t':
+			if (likely(tabstop_is_set(out))) {
+				prt_bytes(out, unprinted_start, str - unprinted_start);
+				unprinted_start = str + 1;
+				__prt_tab(out);
+			}
+			break;
+		case '\r':
+			if (likely(tabstop_is_set(out))) {
+				prt_bytes(out, unprinted_start, str - unprinted_start);
+				unprinted_start = str + 1;
+				__prt_tab_rjust(out);
+			}
+			break;
+		}
+
+		str++;
+	}
+
+	prt_bytes(out, unprinted_start, str - unprinted_start);
+}
+EXPORT_SYMBOL(prt_bytes_indented);
+
+/**
  * prt_human_readable_u64 - Print out a u64 in human readable units
  *
  * Units of 2^10 (default) or 10^3 are controlled via @buf->si_units