spanstream: implement xsgetn

ligfx · ligfx · commit e5c0340c6e6b · 2020-04-29T15:31:31.000-07:00
It's much faster!
diff --git a/src/spanstream.h b/src/spanstream.h
@@ -44,6 +44,15 @@ class spanstream : public std::istream
 			}
 		}
 
+		std::streamsize xsgetn(char *s, std::streamsize n) override {
+			if (position + n <= buffer_size) {
+				std::copy(buffer + position, buffer + position + n, s);
+				position += n;
+				return n;
+			}
+			return 0;
+		}
+
 		int_type underflow() override {
 			return (position < buffer_size) ? buffer[position] : traits_type::eof();
 		}

Original file line number	Diff line number	Diff line change
`@@ -44,6 +44,15 @@ class spanstream : public std::istream`
`44`	`44`	`}`
`45`	`45`	`}`
`46`	`46`
	`47`	`+ std::streamsize xsgetn(char *s, std::streamsize n) override {`
	`48`	`+ if (position + n <= buffer_size) {`
	`49`	`+ std::copy(buffer + position, buffer + position + n, s);`
	`50`	`+ position += n;`
	`51`	`+ return n;`
	`52`	`+ }`
	`53`	`+ return 0;`
	`54`	`+ }`
	`55`	`+`
`47`	`56`	`int_type underflow() override {`
`48`	`57`	`return (position < buffer_size) ? buffer[position] : traits_type::eof();`
`49`	`58`	`}`