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Merged
merged 2 commits into from
Jul 5, 2025
Merged

Constify character handling too #34

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4fa118d
Constify character handling too
kaidokert Jul 5, 2025
fe6ba02
Address feedback
kaidokert Jul 5, 2025
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132 changes: 84 additions & 48 deletions picojson/src/ujson/tokenizer/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -282,6 +282,60 @@ const fn process_token_char(
}
}
impl<T: BitBucket, D: DepthCounter> Tokenizer<T, D> {
// Const lookup table for escape sequences - replaces runtime match
const ESCAPE_TOKENS: [Option<EventToken>; 256] = {
let mut table = [None; 256];
table[b'"' as usize] = Some(EventToken::EscapeQuote);
table[b'\\' as usize] = Some(EventToken::EscapeBackslash);
table[b'/' as usize] = Some(EventToken::EscapeSlash);
table[b'b' as usize] = Some(EventToken::EscapeBackspace);
table[b'f' as usize] = Some(EventToken::EscapeFormFeed);
table[b'n' as usize] = Some(EventToken::EscapeNewline);
table[b'r' as usize] = Some(EventToken::EscapeCarriageReturn);
table[b't' as usize] = Some(EventToken::EscapeTab);
table
};

// Character classification tables for faster parsing
const IS_NON_ZERO_DIGIT: [bool; 256] = {
let mut table = [false; 256];
let mut i = b'1';
while i <= b'9' {
table[i as usize] = true;
i += 1;
}
table
};

const IS_WHITESPACE: [bool; 256] = {
let mut table = [false; 256];
table[b' ' as usize] = true;
table[b'\t' as usize] = true;
table[b'\n' as usize] = true;
table[b'\r' as usize] = true;
table
};

const IS_HEX_DIGIT: [bool; 256] = {
let mut table = [false; 256];
let mut i = b'0';
while i <= b'9' {
table[i as usize] = true;
i += 1;
}
let mut i = b'a';
while i <= b'f' {
table[i as usize] = true;
i += 1;
}
let mut i = b'A';
while i <= b'F' {
table[i as usize] = true;
i += 1;
}
table
};

// Number state transition table: [current_state][character] -> next_state
const NUM_TRANSITIONS: [[Option<Num>; 256]; 8] = {
let mut table = [[None; 256]; 8];
Expand Down Expand Up @@ -565,7 +619,7 @@ impl<T: BitBucket, D: DepthCounter> Tokenizer<T, D> {
callback(Event::End(EventToken::Number), pos);
self.context.after_comma = Some((ch, pos));
self.saw_a_comma_now_what()
} else if matches!(ch, b' ' | b'\t' | b'\n' | b'\r') {
} else if Self::IS_WHITESPACE[ch as usize] {
callback(Event::End(EventToken::Number), pos);
self.maybe_exit_level()
} else if ch == b']' {
Expand Down Expand Up @@ -638,44 +692,32 @@ impl<T: BitBucket, D: DepthCounter> Tokenizer<T, D> {
state: String::Escaping,
key,
},
escape_char @ (b'"' | b'\\' | b'/' | b'b' | b'f' | b'n' | b'r' | b't'),
escape_char,
) => {
let escape_token = match escape_char {
b'"' => EventToken::EscapeQuote,
b'\\' => EventToken::EscapeBackslash,
b'/' => EventToken::EscapeSlash,
b'b' => EventToken::EscapeBackspace,
b'f' => EventToken::EscapeFormFeed,
b'n' => EventToken::EscapeNewline,
b'r' => EventToken::EscapeCarriageReturn,
b't' => EventToken::EscapeTab,
// This branch should never be reached due to the pattern guard above
_ => return Error::new(ErrKind::InvalidStringEscape, current_byte, pos),
};
callback(Event::Begin(escape_token.clone()), pos);
callback(Event::End(escape_token), pos);
State::String {
state: String::Normal,
key: *key,
if let Some(escape_token) = Self::ESCAPE_TOKENS[escape_char as usize] {
callback(Event::Begin(escape_token), pos);
callback(Event::End(escape_token), pos);
State::String {
state: String::Normal,
key: *key,
}
} else if escape_char == b'u' {
// Handle unicode escape sequence
State::String {
state: String::Unicode0,
key: *key,
}
} else {
return Error::new(ErrKind::InvalidStringEscape, escape_char, pos);
}
}
(
State::String {
state: String::Escaping,
key,
},
b'u',
) => State::String {
state: String::Unicode0,
key: *key,
},
(
State::String {
state: String::Unicode0,
key,
},
b'0'..=b'9' | b'a'..=b'f' | b'A'..=b'F',
) => {
ch,
) if Self::IS_HEX_DIGIT[ch as usize] => {
callback(Event::Begin(EventToken::UnicodeEscape), pos);
State::String {
state: String::Unicode1,
Expand All @@ -687,8 +729,8 @@ impl<T: BitBucket, D: DepthCounter> Tokenizer<T, D> {
state: String::Unicode1,
key,
},
b'0'..=b'9' | b'a'..=b'f' | b'A'..=b'F',
) => State::String {
ch,
) if Self::IS_HEX_DIGIT[ch as usize] => State::String {
state: String::Unicode2,
key: *key,
},
Expand All @@ -697,8 +739,8 @@ impl<T: BitBucket, D: DepthCounter> Tokenizer<T, D> {
state: String::Unicode2,
key,
},
b'0'..=b'9' | b'a'..=b'f' | b'A'..=b'F',
) => State::String {
ch,
) if Self::IS_HEX_DIGIT[ch as usize] => State::String {
state: String::Unicode3,
key: *key,
},
Expand All @@ -707,8 +749,8 @@ impl<T: BitBucket, D: DepthCounter> Tokenizer<T, D> {
state: String::Unicode3,
key,
},
b'0'..=b'9' | b'a'..=b'f' | b'A'..=b'F',
) => {
ch,
) if Self::IS_HEX_DIGIT[ch as usize] => {
callback(Event::End(EventToken::UnicodeEscape), pos);
State::String {
state: String::Normal,
Expand Down Expand Up @@ -741,8 +783,8 @@ impl<T: BitBucket, D: DepthCounter> Tokenizer<T, D> {
| State::Object { expect: _ }
| State::Array { expect: _ }
| State::Finished,
b' ' | b'\t' | b'\n' | b'\r',
) => self.state.clone(),
ch,
) if Self::IS_WHITESPACE[ch as usize] => self.state.clone(),
(
State::Idle
| State::Object {
Expand Down Expand Up @@ -837,8 +879,8 @@ impl<T: BitBucket, D: DepthCounter> Tokenizer<T, D> {
| State::Array {
expect: Array::ItemOrEnd,
},
b'1'..=b'9',
) => {
ch,
) if Self::IS_NON_ZERO_DIGIT[ch as usize] => {
callback(Event::Begin(EventToken::Number), pos);
State::Number {
state: Num::BeforeDecimalPoint,
Expand Down Expand Up @@ -965,13 +1007,7 @@ impl<T: BitBucket, D: DepthCounter> Tokenizer<T, D> {
(State::Idle, _) => {
return Error::new(ErrKind::InvalidRoot, current_byte, pos);
}
(
State::String {
state: String::Escaping,
key: _,
},
_,
) => return Error::new(ErrKind::InvalidStringEscape, current_byte, pos),

(
State::Object {
expect: Object::Key,
Expand Down