1 file changed, 79 insertions, 0 deletions
diff --git a/source/html.c b/source/html.c
index d1e28f8..d13ac5b 100644
--- a/source/html.c
+++ b/source/html.c
@@ -258,6 +258,85 @@ ssize_t html_ntxt(const char *txt, size_t len)
 	return left;
 }
 
+/*
+ * git ends a line only at a line feed. A browser also starts one at a carriage
+ * return with no line feed after it, since the HTML parser turns that into a
+ * line feed, and may at the other characters Unicode makes mandatory breaks.
+ * Escaping those keeps one line on the page for every line git counts, so the
+ * numbers beside the text stay in step with it.
+ */
+const char *html_line_break_escape(const char *p, const char *end, size_t *width)
+{
+	const char *esc;
+
+	switch ((unsigned char)*p) {
+	case '\r':
+		// The parser reads CR LF as the single line feed git ends the
+		// line with.
+		if (p + 1 < end && p[1] == '\n')
+			return NULL;
+		*width = 1;
+		return "\\r";
+	case '\v':
+		*width = 1;
+		return "\\v";
+	case '\f':
+		*width = 1;
+		return "\\f";
+	case 0xc2:
+		if (end - p < 2 || memcmp(p, "\xc2\x85", 2))
+			return NULL;
+		*width = 2;
+		return "\\u0085";
+	case 0xe2:
+		if (end - p >= 3 && !memcmp(p, "\xe2\x80\xa8", 3))
+			esc = "\\u2028";
+		else if (end - p >= 3 && !memcmp(p, "\xe2\x80\xa9", 3))
+			esc = "\\u2029";
+		else
+			return NULL;
+		*width = 3;
+		return esc;
+	default:
+		return NULL;
+	}
+}
+
+void html_blob_txt(const char *txt, size_t len)
+{
+	const char *end = txt + len;
+	const char *p;
+
+	for (p = txt; p < end; p++) {
+		const char *entity = NULL, *esc = NULL;
+		size_t width = 1;
+
+		if (*p == '<')
+			entity = "&lt;";
+		else if (*p == '>')
+			entity = "&gt;";
+		else if (*p == '&')
+			entity = "&amp;";
+		else
+			esc = html_line_break_escape(p, end, &width);
+		if (!entity && !esc)
+			continue;
+		html_raw(txt, p - txt);
+		if (entity) {
+			html(entity);
+		} else {
+			// The span lets a stylesheet tell the escape from the
+			// same characters typed into the file.
+			html("<span class='escape'>");
+			html(esc);
+			html("</span>");
+		}
+		p += width - 1;
+		txt = p + 1;
+	}
+	html_raw(txt, end - txt);
+}
+
 void html_attrf(const char *format, ...)
 {
 	va_list args;