1 files changed, 46 insertions, 0 deletions
diff --git a/third_party/rust/serde/src/de/utf8.rs b/third_party/rust/serde/src/de/utf8.rs
new file mode 100644
index 0000000000..576fd03cfa
--- /dev/null
+++ b/third_party/rust/serde/src/de/utf8.rs
@@ -0,0 +1,46 @@
+use lib::*;
+
+const TAG_CONT: u8 = 0b1000_0000;
+const TAG_TWO_B: u8 = 0b1100_0000;
+const TAG_THREE_B: u8 = 0b1110_0000;
+const TAG_FOUR_B: u8 = 0b1111_0000;
+const MAX_ONE_B: u32 = 0x80;
+const MAX_TWO_B: u32 = 0x800;
+const MAX_THREE_B: u32 = 0x10000;
+
+#[inline]
+pub fn encode(c: char) -> Encode {
+    let code = c as u32;
+    let mut buf = [0; 4];
+    let pos = if code < MAX_ONE_B {
+        buf[3] = code as u8;
+        3
+    } else if code < MAX_TWO_B {
+        buf[2] = (code >> 6 & 0x1F) as u8 | TAG_TWO_B;
+        buf[3] = (code & 0x3F) as u8 | TAG_CONT;
+        2
+    } else if code < MAX_THREE_B {
+        buf[1] = (code >> 12 & 0x0F) as u8 | TAG_THREE_B;
+        buf[2] = (code >> 6 & 0x3F) as u8 | TAG_CONT;
+        buf[3] = (code & 0x3F) as u8 | TAG_CONT;
+        1
+    } else {
+        buf[0] = (code >> 18 & 0x07) as u8 | TAG_FOUR_B;
+        buf[1] = (code >> 12 & 0x3F) as u8 | TAG_CONT;
+        buf[2] = (code >> 6 & 0x3F) as u8 | TAG_CONT;
+        buf[3] = (code & 0x3F) as u8 | TAG_CONT;
+        0
+    };
+    Encode { buf: buf, pos: pos }
+}
+
+pub struct Encode {
+    buf: [u8; 4],
+    pos: usize,
+}
+
+impl Encode {
+    pub fn as_str(&self) -> &str {
+        str::from_utf8(&self.buf[self.pos..]).unwrap()
+    }
+}