| //! Types supporting the UTF-8 parser |
| #![allow(non_camel_case_types)] |
| use core::mem; |
| |
| /// States the parser can be in. |
| /// |
| /// There is a state for each initial input of the 3 and 4 byte sequences since |
| /// the following bytes are subject to different conditions than a tail byte. |
| #[allow(dead_code)] |
| #[derive(Debug, Copy, Clone)] |
| pub enum State { |
| /// Ground state; expect anything |
| Ground = 0, |
| /// 3 tail bytes |
| Tail3 = 1, |
| /// 2 tail bytes |
| Tail2 = 2, |
| /// 1 tail byte |
| Tail1 = 3, |
| /// UTF8-3 starting with E0 |
| U3_2_e0 = 4, |
| /// UTF8-3 starting with ED |
| U3_2_ed = 5, |
| /// UTF8-4 starting with F0 |
| Utf8_4_3_f0 = 6, |
| /// UTF8-4 starting with F4 |
| Utf8_4_3_f4 = 7, |
| } |
| |
| /// Action to take when receiving a byte |
| #[allow(dead_code)] |
| #[derive(Debug, Copy, Clone)] |
| pub enum Action { |
| /// Unexpected byte; sequence is invalid |
| InvalidSequence = 0, |
| /// Received valid 7-bit ASCII byte which can be directly emitted. |
| EmitByte = 1, |
| /// Set the bottom continuation byte |
| SetByte1 = 2, |
| /// Set the 2nd-from-last continuation byte |
| SetByte2 = 3, |
| /// Set the 2nd-from-last byte which is part of a two byte sequence |
| SetByte2Top = 4, |
| /// Set the 3rd-from-last continuation byte |
| SetByte3 = 5, |
| /// Set the 3rd-from-last byte which is part of a three byte sequence |
| SetByte3Top = 6, |
| /// Set the top byte of a four byte sequence. |
| SetByte4 = 7, |
| } |
| |
| /// Convert a state and action to a u8 |
| /// |
| /// State will be the bottom 4 bits and action the top 4 |
| #[inline] |
| #[allow(dead_code)] |
| pub fn pack(state: State, action: Action) -> u8 { |
| ((action as u8) << 4) | (state as u8) |
| } |
| |
| /// Convert a u8 to a state and action |
| /// |
| /// # Unsafety |
| /// |
| /// If this function is called with a byte that wasn't encoded with the `pack` |
| /// function in this module, there is no guarantee that a valid state and action |
| /// can be produced. |
| #[inline] |
| pub unsafe fn unpack(val: u8) -> (State, Action) { |
| ( |
| // State is stored in bottom 4 bits |
| mem::transmute(val & 0x0f), |
| |
| // Action is stored in top 4 bits |
| mem::transmute(val >> 4), |
| ) |
| } |