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Diffstat (limited to 'vendor/serde_json/src/read.rs')
| -rw-r--r-- | vendor/serde_json/src/read.rs | 1004 |
1 files changed, 1004 insertions, 0 deletions
diff --git a/vendor/serde_json/src/read.rs b/vendor/serde_json/src/read.rs new file mode 100644 index 0000000..7446f28 --- /dev/null +++ b/vendor/serde_json/src/read.rs @@ -0,0 +1,1004 @@ +use crate::error::{Error, ErrorCode, Result}; +use alloc::vec::Vec; +use core::char; +use core::cmp; +use core::ops::Deref; +use core::str; + +#[cfg(feature = "std")] +use crate::io; +#[cfg(feature = "std")] +use crate::iter::LineColIterator; + +#[cfg(feature = "raw_value")] +use crate::raw::BorrowedRawDeserializer; +#[cfg(all(feature = "raw_value", feature = "std"))] +use crate::raw::OwnedRawDeserializer; +#[cfg(feature = "raw_value")] +use serde::de::Visitor; + +/// Trait used by the deserializer for iterating over input. This is manually +/// "specialized" for iterating over &[u8]. Once feature(specialization) is +/// stable we can use actual specialization. +/// +/// This trait is sealed and cannot be implemented for types outside of +/// `serde_json`. +pub trait Read<'de>: private::Sealed { + #[doc(hidden)] + fn next(&mut self) -> Result<Option<u8>>; + #[doc(hidden)] + fn peek(&mut self) -> Result<Option<u8>>; + + /// Only valid after a call to peek(). Discards the peeked byte. + #[doc(hidden)] + fn discard(&mut self); + + /// Position of the most recent call to next(). + /// + /// The most recent call was probably next() and not peek(), but this method + /// should try to return a sensible result if the most recent call was + /// actually peek() because we don't always know. + /// + /// Only called in case of an error, so performance is not important. + #[doc(hidden)] + fn position(&self) -> Position; + + /// Position of the most recent call to peek(). + /// + /// The most recent call was probably peek() and not next(), but this method + /// should try to return a sensible result if the most recent call was + /// actually next() because we don't always know. + /// + /// Only called in case of an error, so performance is not important. + #[doc(hidden)] + fn peek_position(&self) -> Position; + + /// Offset from the beginning of the input to the next byte that would be + /// returned by next() or peek(). + #[doc(hidden)] + fn byte_offset(&self) -> usize; + + /// Assumes the previous byte was a quotation mark. Parses a JSON-escaped + /// string until the next quotation mark using the given scratch space if + /// necessary. The scratch space is initially empty. + #[doc(hidden)] + fn parse_str<'s>(&'s mut self, scratch: &'s mut Vec<u8>) -> Result<Reference<'de, 's, str>>; + + /// Assumes the previous byte was a quotation mark. Parses a JSON-escaped + /// string until the next quotation mark using the given scratch space if + /// necessary. The scratch space is initially empty. + /// + /// This function returns the raw bytes in the string with escape sequences + /// expanded but without performing unicode validation. + #[doc(hidden)] + fn parse_str_raw<'s>( + &'s mut self, + scratch: &'s mut Vec<u8>, + ) -> Result<Reference<'de, 's, [u8]>>; + + /// Assumes the previous byte was a quotation mark. Parses a JSON-escaped + /// string until the next quotation mark but discards the data. + #[doc(hidden)] + fn ignore_str(&mut self) -> Result<()>; + + /// Assumes the previous byte was a hex escape sequence ('\u') in a string. + /// Parses next hexadecimal sequence. + #[doc(hidden)] + fn decode_hex_escape(&mut self) -> Result<u16>; + + /// Switch raw buffering mode on. + /// + /// This is used when deserializing `RawValue`. + #[cfg(feature = "raw_value")] + #[doc(hidden)] + fn begin_raw_buffering(&mut self); + + /// Switch raw buffering mode off and provides the raw buffered data to the + /// given visitor. + #[cfg(feature = "raw_value")] + #[doc(hidden)] + fn end_raw_buffering<V>(&mut self, visitor: V) -> Result<V::Value> + where + V: Visitor<'de>; + + /// Whether StreamDeserializer::next needs to check the failed flag. True + /// for IoRead, false for StrRead and SliceRead which can track failure by + /// truncating their input slice to avoid the extra check on every next + /// call. + #[doc(hidden)] + const should_early_return_if_failed: bool; + + /// Mark a persistent failure of StreamDeserializer, either by setting the + /// flag or by truncating the input data. + #[doc(hidden)] + fn set_failed(&mut self, failed: &mut bool); +} + +pub struct Position { + pub line: usize, + pub column: usize, +} + +pub enum Reference<'b, 'c, T> +where + T: ?Sized + 'static, +{ + Borrowed(&'b T), + Copied(&'c T), +} + +impl<'b, 'c, T> Deref for Reference<'b, 'c, T> +where + T: ?Sized + 'static, +{ + type Target = T; + + fn deref(&self) -> &Self::Target { + match *self { + Reference::Borrowed(b) => b, + Reference::Copied(c) => c, + } + } +} + +/// JSON input source that reads from a std::io input stream. +#[cfg(feature = "std")] +#[cfg_attr(docsrs, doc(cfg(feature = "std")))] +pub struct IoRead<R> +where + R: io::Read, +{ + iter: LineColIterator<io::Bytes<R>>, + /// Temporary storage of peeked byte. + ch: Option<u8>, + #[cfg(feature = "raw_value")] + raw_buffer: Option<Vec<u8>>, +} + +/// JSON input source that reads from a slice of bytes. +// +// This is more efficient than other iterators because peek() can be read-only +// and we can compute line/col position only if an error happens. +pub struct SliceRead<'a> { + slice: &'a [u8], + /// Index of the *next* byte that will be returned by next() or peek(). + index: usize, + #[cfg(feature = "raw_value")] + raw_buffering_start_index: usize, +} + +/// JSON input source that reads from a UTF-8 string. +// +// Able to elide UTF-8 checks by assuming that the input is valid UTF-8. +pub struct StrRead<'a> { + delegate: SliceRead<'a>, + #[cfg(feature = "raw_value")] + data: &'a str, +} + +// Prevent users from implementing the Read trait. +mod private { + pub trait Sealed {} +} + +////////////////////////////////////////////////////////////////////////////// + +#[cfg(feature = "std")] +impl<R> IoRead<R> +where + R: io::Read, +{ + /// Create a JSON input source to read from a std::io input stream. + pub fn new(reader: R) -> Self { + IoRead { + iter: LineColIterator::new(reader.bytes()), + ch: None, + #[cfg(feature = "raw_value")] + raw_buffer: None, + } + } +} + +#[cfg(feature = "std")] +impl<R> private::Sealed for IoRead<R> where R: io::Read {} + +#[cfg(feature = "std")] +impl<R> IoRead<R> +where + R: io::Read, +{ + fn parse_str_bytes<'s, T, F>( + &'s mut self, + scratch: &'s mut Vec<u8>, + validate: bool, + result: F, + ) -> Result<T> + where + T: 's, + F: FnOnce(&'s Self, &'s [u8]) -> Result<T>, + { + loop { + let ch = tri!(next_or_eof(self)); + if !ESCAPE[ch as usize] { + scratch.push(ch); + continue; + } + match ch { + b'"' => { + return result(self, scratch); + } + b'\\' => { + tri!(parse_escape(self, validate, scratch)); + } + _ => { + if validate { + return error(self, ErrorCode::ControlCharacterWhileParsingString); + } + scratch.push(ch); + } + } + } + } +} + +#[cfg(feature = "std")] +impl<'de, R> Read<'de> for IoRead<R> +where + R: io::Read, +{ + #[inline] + fn next(&mut self) -> Result<Option<u8>> { + match self.ch.take() { + Some(ch) => { + #[cfg(feature = "raw_value")] + { + if let Some(buf) = &mut self.raw_buffer { + buf.push(ch); + } + } + Ok(Some(ch)) + } + None => match self.iter.next() { + Some(Err(err)) => Err(Error::io(err)), + Some(Ok(ch)) => { + #[cfg(feature = "raw_value")] + { + if let Some(buf) = &mut self.raw_buffer { + buf.push(ch); + } + } + Ok(Some(ch)) + } + None => Ok(None), + }, + } + } + + #[inline] + fn peek(&mut self) -> Result<Option<u8>> { + match self.ch { + Some(ch) => Ok(Some(ch)), + None => match self.iter.next() { + Some(Err(err)) => Err(Error::io(err)), + Some(Ok(ch)) => { + self.ch = Some(ch); + Ok(self.ch) + } + None => Ok(None), + }, + } + } + + #[cfg(not(feature = "raw_value"))] + #[inline] + fn discard(&mut self) { + self.ch = None; + } + + #[cfg(feature = "raw_value")] + fn discard(&mut self) { + if let Some(ch) = self.ch.take() { + if let Some(buf) = &mut self.raw_buffer { + buf.push(ch); + } + } + } + + fn position(&self) -> Position { + Position { + line: self.iter.line(), + column: self.iter.col(), + } + } + + fn peek_position(&self) -> Position { + // The LineColIterator updates its position during peek() so it has the + // right one here. + self.position() + } + + fn byte_offset(&self) -> usize { + match self.ch { + Some(_) => self.iter.byte_offset() - 1, + None => self.iter.byte_offset(), + } + } + + fn parse_str<'s>(&'s mut self, scratch: &'s mut Vec<u8>) -> Result<Reference<'de, 's, str>> { + self.parse_str_bytes(scratch, true, as_str) + .map(Reference::Copied) + } + + fn parse_str_raw<'s>( + &'s mut self, + scratch: &'s mut Vec<u8>, + ) -> Result<Reference<'de, 's, [u8]>> { + self.parse_str_bytes(scratch, false, |_, bytes| Ok(bytes)) + .map(Reference::Copied) + } + + fn ignore_str(&mut self) -> Result<()> { + loop { + let ch = tri!(next_or_eof(self)); + if !ESCAPE[ch as usize] { + continue; + } + match ch { + b'"' => { + return Ok(()); + } + b'\\' => { + tri!(ignore_escape(self)); + } + _ => { + return error(self, ErrorCode::ControlCharacterWhileParsingString); + } + } + } + } + + fn decode_hex_escape(&mut self) -> Result<u16> { + let mut n = 0; + for _ in 0..4 { + match decode_hex_val(tri!(next_or_eof(self))) { + None => return error(self, ErrorCode::InvalidEscape), + Some(val) => { + n = (n << 4) + val; + } + } + } + Ok(n) + } + + #[cfg(feature = "raw_value")] + fn begin_raw_buffering(&mut self) { + self.raw_buffer = Some(Vec::new()); + } + + #[cfg(feature = "raw_value")] + fn end_raw_buffering<V>(&mut self, visitor: V) -> Result<V::Value> + where + V: Visitor<'de>, + { + let raw = self.raw_buffer.take().unwrap(); + let raw = match String::from_utf8(raw) { + Ok(raw) => raw, + Err(_) => return error(self, ErrorCode::InvalidUnicodeCodePoint), + }; + visitor.visit_map(OwnedRawDeserializer { + raw_value: Some(raw), + }) + } + + const should_early_return_if_failed: bool = true; + + #[inline] + #[cold] + fn set_failed(&mut self, failed: &mut bool) { + *failed = true; + } +} + +////////////////////////////////////////////////////////////////////////////// + +impl<'a> SliceRead<'a> { + /// Create a JSON input source to read from a slice of bytes. + pub fn new(slice: &'a [u8]) -> Self { + SliceRead { + slice, + index: 0, + #[cfg(feature = "raw_value")] + raw_buffering_start_index: 0, + } + } + + fn position_of_index(&self, i: usize) -> Position { + let mut position = Position { line: 1, column: 0 }; + for ch in &self.slice[..i] { + match *ch { + b'\n' => { + position.line += 1; + position.column = 0; + } + _ => { + position.column += 1; + } + } + } + position + } + + /// The big optimization here over IoRead is that if the string contains no + /// backslash escape sequences, the returned &str is a slice of the raw JSON + /// data so we avoid copying into the scratch space. + fn parse_str_bytes<'s, T, F>( + &'s mut self, + scratch: &'s mut Vec<u8>, + validate: bool, + result: F, + ) -> Result<Reference<'a, 's, T>> + where + T: ?Sized + 's, + F: for<'f> FnOnce(&'s Self, &'f [u8]) -> Result<&'f T>, + { + // Index of the first byte not yet copied into the scratch space. + let mut start = self.index; + + loop { + while self.index < self.slice.len() && !ESCAPE[self.slice[self.index] as usize] { + self.index += 1; + } + if self.index == self.slice.len() { + return error(self, ErrorCode::EofWhileParsingString); + } + match self.slice[self.index] { + b'"' => { + if scratch.is_empty() { + // Fast path: return a slice of the raw JSON without any + // copying. + let borrowed = &self.slice[start..self.index]; + self.index += 1; + return result(self, borrowed).map(Reference::Borrowed); + } else { + scratch.extend_from_slice(&self.slice[start..self.index]); + self.index += 1; + return result(self, scratch).map(Reference::Copied); + } + } + b'\\' => { + scratch.extend_from_slice(&self.slice[start..self.index]); + self.index += 1; + tri!(parse_escape(self, validate, scratch)); + start = self.index; + } + _ => { + self.index += 1; + if validate { + return error(self, ErrorCode::ControlCharacterWhileParsingString); + } + } + } + } + } +} + +impl<'a> private::Sealed for SliceRead<'a> {} + +impl<'a> Read<'a> for SliceRead<'a> { + #[inline] + fn next(&mut self) -> Result<Option<u8>> { + // `Ok(self.slice.get(self.index).map(|ch| { self.index += 1; *ch }))` + // is about 10% slower. + Ok(if self.index < self.slice.len() { + let ch = self.slice[self.index]; + self.index += 1; + Some(ch) + } else { + None + }) + } + + #[inline] + fn peek(&mut self) -> Result<Option<u8>> { + // `Ok(self.slice.get(self.index).map(|ch| *ch))` is about 10% slower + // for some reason. + Ok(if self.index < self.slice.len() { + Some(self.slice[self.index]) + } else { + None + }) + } + + #[inline] + fn discard(&mut self) { + self.index += 1; + } + + fn position(&self) -> Position { + self.position_of_index(self.index) + } + + fn peek_position(&self) -> Position { + // Cap it at slice.len() just in case the most recent call was next() + // and it returned the last byte. + self.position_of_index(cmp::min(self.slice.len(), self.index + 1)) + } + + fn byte_offset(&self) -> usize { + self.index + } + + fn parse_str<'s>(&'s mut self, scratch: &'s mut Vec<u8>) -> Result<Reference<'a, 's, str>> { + self.parse_str_bytes(scratch, true, as_str) + } + + fn parse_str_raw<'s>( + &'s mut self, + scratch: &'s mut Vec<u8>, + ) -> Result<Reference<'a, 's, [u8]>> { + self.parse_str_bytes(scratch, false, |_, bytes| Ok(bytes)) + } + + fn ignore_str(&mut self) -> Result<()> { + loop { + while self.index < self.slice.len() && !ESCAPE[self.slice[self.index] as usize] { + self.index += 1; + } + if self.index == self.slice.len() { + return error(self, ErrorCode::EofWhileParsingString); + } + match self.slice[self.index] { + b'"' => { + self.index += 1; + return Ok(()); + } + b'\\' => { + self.index += 1; + tri!(ignore_escape(self)); + } + _ => { + return error(self, ErrorCode::ControlCharacterWhileParsingString); + } + } + } + } + + fn decode_hex_escape(&mut self) -> Result<u16> { + if self.index + 4 > self.slice.len() { + self.index = self.slice.len(); + return error(self, ErrorCode::EofWhileParsingString); + } + + let mut n = 0; + for _ in 0..4 { + let ch = decode_hex_val(self.slice[self.index]); + self.index += 1; + match ch { + None => return error(self, ErrorCode::InvalidEscape), + Some(val) => { + n = (n << 4) + val; + } + } + } + Ok(n) + } + + #[cfg(feature = "raw_value")] + fn begin_raw_buffering(&mut self) { + self.raw_buffering_start_index = self.index; + } + + #[cfg(feature = "raw_value")] + fn end_raw_buffering<V>(&mut self, visitor: V) -> Result<V::Value> + where + V: Visitor<'a>, + { + let raw = &self.slice[self.raw_buffering_start_index..self.index]; + let raw = match str::from_utf8(raw) { + Ok(raw) => raw, + Err(_) => return error(self, ErrorCode::InvalidUnicodeCodePoint), + }; + visitor.visit_map(BorrowedRawDeserializer { + raw_value: Some(raw), + }) + } + + const should_early_return_if_failed: bool = false; + + #[inline] + #[cold] + fn set_failed(&mut self, _failed: &mut bool) { + self.slice = &self.slice[..self.index]; + } +} + +////////////////////////////////////////////////////////////////////////////// + +impl<'a> StrRead<'a> { + /// Create a JSON input source to read from a UTF-8 string. + pub fn new(s: &'a str) -> Self { + StrRead { + delegate: SliceRead::new(s.as_bytes()), + #[cfg(feature = "raw_value")] + data: s, + } + } +} + +impl<'a> private::Sealed for StrRead<'a> {} + +impl<'a> Read<'a> for StrRead<'a> { + #[inline] + fn next(&mut self) -> Result<Option<u8>> { + self.delegate.next() + } + + #[inline] + fn peek(&mut self) -> Result<Option<u8>> { + self.delegate.peek() + } + + #[inline] + fn discard(&mut self) { + self.delegate.discard(); + } + + fn position(&self) -> Position { + self.delegate.position() + } + + fn peek_position(&self) -> Position { + self.delegate.peek_position() + } + + fn byte_offset(&self) -> usize { + self.delegate.byte_offset() + } + + fn parse_str<'s>(&'s mut self, scratch: &'s mut Vec<u8>) -> Result<Reference<'a, 's, str>> { + self.delegate.parse_str_bytes(scratch, true, |_, bytes| { + // The deserialization input came in as &str with a UTF-8 guarantee, + // and the \u-escapes are checked along the way, so don't need to + // check here. + Ok(unsafe { str::from_utf8_unchecked(bytes) }) + }) + } + + fn parse_str_raw<'s>( + &'s mut self, + scratch: &'s mut Vec<u8>, + ) -> Result<Reference<'a, 's, [u8]>> { + self.delegate.parse_str_raw(scratch) + } + + fn ignore_str(&mut self) -> Result<()> { + self.delegate.ignore_str() + } + + fn decode_hex_escape(&mut self) -> Result<u16> { + self.delegate.decode_hex_escape() + } + + #[cfg(feature = "raw_value")] + fn begin_raw_buffering(&mut self) { + self.delegate.begin_raw_buffering(); + } + + #[cfg(feature = "raw_value")] + fn end_raw_buffering<V>(&mut self, visitor: V) -> Result<V::Value> + where + V: Visitor<'a>, + { + let raw = &self.data[self.delegate.raw_buffering_start_index..self.delegate.index]; + visitor.visit_map(BorrowedRawDeserializer { + raw_value: Some(raw), + }) + } + + const should_early_return_if_failed: bool = false; + + #[inline] + #[cold] + fn set_failed(&mut self, failed: &mut bool) { + self.delegate.set_failed(failed); + } +} + +////////////////////////////////////////////////////////////////////////////// + +impl<'a, 'de, R> private::Sealed for &'a mut R where R: Read<'de> {} + +impl<'a, 'de, R> Read<'de> for &'a mut R +where + R: Read<'de>, +{ + fn next(&mut self) -> Result<Option<u8>> { + R::next(self) + } + + fn peek(&mut self) -> Result<Option<u8>> { + R::peek(self) + } + + fn discard(&mut self) { + R::discard(self); + } + + fn position(&self) -> Position { + R::position(self) + } + + fn peek_position(&self) -> Position { + R::peek_position(self) + } + + fn byte_offset(&self) -> usize { + R::byte_offset(self) + } + + fn parse_str<'s>(&'s mut self, scratch: &'s mut Vec<u8>) -> Result<Reference<'de, 's, str>> { + R::parse_str(self, scratch) + } + + fn parse_str_raw<'s>( + &'s mut self, + scratch: &'s mut Vec<u8>, + ) -> Result<Reference<'de, 's, [u8]>> { + R::parse_str_raw(self, scratch) + } + + fn ignore_str(&mut self) -> Result<()> { + R::ignore_str(self) + } + + fn decode_hex_escape(&mut self) -> Result<u16> { + R::decode_hex_escape(self) + } + + #[cfg(feature = "raw_value")] + fn begin_raw_buffering(&mut self) { + R::begin_raw_buffering(self); + } + + #[cfg(feature = "raw_value")] + fn end_raw_buffering<V>(&mut self, visitor: V) -> Result<V::Value> + where + V: Visitor<'de>, + { + R::end_raw_buffering(self, visitor) + } + + const should_early_return_if_failed: bool = R::should_early_return_if_failed; + + fn set_failed(&mut self, failed: &mut bool) { + R::set_failed(self, failed); + } +} + +////////////////////////////////////////////////////////////////////////////// + +/// Marker for whether StreamDeserializer can implement FusedIterator. +pub trait Fused: private::Sealed {} +impl<'a> Fused for SliceRead<'a> {} +impl<'a> Fused for StrRead<'a> {} + +// Lookup table of bytes that must be escaped. A value of true at index i means +// that byte i requires an escape sequence in the input. +static ESCAPE: [bool; 256] = { + const CT: bool = true; // control character \x00..=\x1F + const QU: bool = true; // quote \x22 + const BS: bool = true; // backslash \x5C + const __: bool = false; // allow unescaped + [ + // 1 2 3 4 5 6 7 8 9 A B C D E F + CT, CT, CT, CT, CT, CT, CT, CT, CT, CT, CT, CT, CT, CT, CT, CT, // 0 + CT, CT, CT, CT, CT, CT, CT, CT, CT, CT, CT, CT, CT, CT, CT, CT, // 1 + __, __, QU, __, __, __, __, __, __, __, __, __, __, __, __, __, // 2 + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 3 + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 4 + __, __, __, __, __, __, __, __, __, __, __, __, BS, __, __, __, // 5 + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 6 + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 7 + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 8 + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 9 + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // A + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // B + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // C + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // D + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // E + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // F + ] +}; + +fn next_or_eof<'de, R>(read: &mut R) -> Result<u8> +where + R: ?Sized + Read<'de>, +{ + match tri!(read.next()) { + Some(b) => Ok(b), + None => error(read, ErrorCode::EofWhileParsingString), + } +} + +fn peek_or_eof<'de, R>(read: &mut R) -> Result<u8> +where + R: ?Sized + Read<'de>, +{ + match tri!(read.peek()) { + Some(b) => Ok(b), + None => error(read, ErrorCode::EofWhileParsingString), + } +} + +fn error<'de, R, T>(read: &R, reason: ErrorCode) -> Result<T> +where + R: ?Sized + Read<'de>, +{ + let position = read.position(); + Err(Error::syntax(reason, position.line, position.column)) +} + +fn as_str<'de, 's, R: Read<'de>>(read: &R, slice: &'s [u8]) -> Result<&'s str> { + str::from_utf8(slice).or_else(|_| error(read, ErrorCode::InvalidUnicodeCodePoint)) +} + +/// Parses a JSON escape sequence and appends it into the scratch space. Assumes +/// the previous byte read was a backslash. +fn parse_escape<'de, R: Read<'de>>( + read: &mut R, + validate: bool, + scratch: &mut Vec<u8>, +) -> Result<()> { + let ch = tri!(next_or_eof(read)); + + match ch { + b'"' => scratch.push(b'"'), + b'\\' => scratch.push(b'\\'), + b'/' => scratch.push(b'/'), + b'b' => scratch.push(b'\x08'), + b'f' => scratch.push(b'\x0c'), + b'n' => scratch.push(b'\n'), + b'r' => scratch.push(b'\r'), + b't' => scratch.push(b'\t'), + b'u' => { + fn encode_surrogate(scratch: &mut Vec<u8>, n: u16) { + scratch.extend_from_slice(&[ + (n >> 12 & 0b0000_1111) as u8 | 0b1110_0000, + (n >> 6 & 0b0011_1111) as u8 | 0b1000_0000, + (n & 0b0011_1111) as u8 | 0b1000_0000, + ]); + } + + let c = match tri!(read.decode_hex_escape()) { + n @ 0xDC00..=0xDFFF => { + return if validate { + error(read, ErrorCode::LoneLeadingSurrogateInHexEscape) + } else { + encode_surrogate(scratch, n); + Ok(()) + }; + } + + // Non-BMP characters are encoded as a sequence of two hex + // escapes, representing UTF-16 surrogates. If deserializing a + // utf-8 string the surrogates are required to be paired, + // whereas deserializing a byte string accepts lone surrogates. + n1 @ 0xD800..=0xDBFF => { + if tri!(peek_or_eof(read)) == b'\\' { + read.discard(); + } else { + return if validate { + read.discard(); + error(read, ErrorCode::UnexpectedEndOfHexEscape) + } else { + encode_surrogate(scratch, n1); + Ok(()) + }; + } + + if tri!(peek_or_eof(read)) == b'u' { + read.discard(); + } else { + return if validate { + read.discard(); + error(read, ErrorCode::UnexpectedEndOfHexEscape) + } else { + encode_surrogate(scratch, n1); + // The \ prior to this byte started an escape sequence, + // so we need to parse that now. This recursive call + // does not blow the stack on malicious input because + // the escape is not \u, so it will be handled by one + // of the easy nonrecursive cases. + parse_escape(read, validate, scratch) + }; + } + + let n2 = tri!(read.decode_hex_escape()); + + if n2 < 0xDC00 || n2 > 0xDFFF { + return error(read, ErrorCode::LoneLeadingSurrogateInHexEscape); + } + + let n = (((n1 - 0xD800) as u32) << 10 | (n2 - 0xDC00) as u32) + 0x1_0000; + + match char::from_u32(n) { + Some(c) => c, + None => { + return error(read, ErrorCode::InvalidUnicodeCodePoint); + } + } + } + + // Every u16 outside of the surrogate ranges above is guaranteed + // to be a legal char. + n => char::from_u32(n as u32).unwrap(), + }; + + scratch.extend_from_slice(c.encode_utf8(&mut [0_u8; 4]).as_bytes()); + } + _ => { + return error(read, ErrorCode::InvalidEscape); + } + } + + Ok(()) +} + +/// Parses a JSON escape sequence and discards the value. Assumes the previous +/// byte read was a backslash. +fn ignore_escape<'de, R>(read: &mut R) -> Result<()> +where + R: ?Sized + Read<'de>, +{ + let ch = tri!(next_or_eof(read)); + + match ch { + b'"' | b'\\' | b'/' | b'b' | b'f' | b'n' | b'r' | b't' => {} + b'u' => { + // At this point we don't care if the codepoint is valid. We just + // want to consume it. We don't actually know what is valid or not + // at this point, because that depends on if this string will + // ultimately be parsed into a string or a byte buffer in the "real" + // parse. + + tri!(read.decode_hex_escape()); + } + _ => { + return error(read, ErrorCode::InvalidEscape); + } + } + + Ok(()) +} + +static HEX: [u8; 256] = { + const __: u8 = 255; // not a hex digit + [ + // 1 2 3 4 5 6 7 8 9 A B C D E F + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 0 + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 1 + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 2 + 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, __, __, __, __, __, __, // 3 + __, 10, 11, 12, 13, 14, 15, __, __, __, __, __, __, __, __, __, // 4 + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 5 + __, 10, 11, 12, 13, 14, 15, __, __, __, __, __, __, __, __, __, // 6 + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 7 + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 8 + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 9 + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // A + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // B + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // C + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // D + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // E + __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // F + ] +}; + +fn decode_hex_val(val: u8) -> Option<u16> { + let n = HEX[val as usize] as u16; + if n == 255 { + None + } else { + Some(n) + } +} |