feat(pipeline): PLC/SPS control-logic security scanner (IEC 61131-3) (#162)

compliance-agent/src/pipeline/plc/lexer.rs

@@ -0,0 +1,372 @@
+//! Lexer for IEC 61131-3 Structured Text.
+//!
+//! Tokenizes ST source into a flat token stream with 1-based line numbers.
+//! Keywords are case-insensitive. Handles `(* *)` and `//` comments, `'..'` and
+//! `".."` strings (with `''`/`""` escapes), based integers (`16#FF`, `2#1010`),
+//! and duration/date literals (`T#5s`, `DT#...`) kept as raw text.
+
+/// A lexed token with its source line.
+#[derive(Debug, Clone)]
+pub struct Token {
+    pub kind: Tok,
+    pub line: u32,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum Tok {
+    Int(i64),
+    Real(f64),
+    Str(String),
+    Time(String),
+    Bool(bool),
+    Ident(String),
+    Kw(Keyword),
+    Assign, // :=
+    Plus,   // +
+    Minus,  // -
+    Star,   // *
+    Slash,  // /
+    Power,  // **
+    LParen, // (
+    RParen, // )
+    LBrack, // [
+    RBrack, // ]
+    Dot,    // .
+    DotDot, // ..
+    Comma,  // ,
+    Semi,   // ;
+    Colon,  // :
+    Lt,     // <
+    Le,     // <=
+    Gt,     // >
+    Ge,     // >=
+    Eq,     // =
+    Ne,     // <>
+    Amp,    // &
+    Eof,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Keyword {
+    Program,
+    EndProgram,
+    Function,
+    EndFunction,
+    FunctionBlock,
+    EndFunctionBlock,
+    Var,
+    VarInput,
+    VarOutput,
+    VarInOut,
+    VarGlobal,
+    VarTemp,
+    VarExternal,
+    Constant,
+    EndVar,
+    Array,
+    Of,
+    If,
+    Then,
+    Elsif,
+    Else,
+    EndIf,
+    Case,
+    EndCase,
+    For,
+    To,
+    By,
+    Do,
+    EndFor,
+    While,
+    EndWhile,
+    Repeat,
+    Until,
+    EndRepeat,
+    Return,
+    Exit,
+    Jmp,
+    Not,
+    And,
+    Or,
+    Xor,
+    Mod,
+    Type,
+    EndType,
+    Struct,
+    EndStruct,
+}
+
+fn keyword_from(word: &str) -> Option<Keyword> {
+    use Keyword::*;
+    Some(match word.to_ascii_uppercase().as_str() {
+        "PROGRAM" => Program,
+        "END_PROGRAM" => EndProgram,
+        "FUNCTION" => Function,
+        "END_FUNCTION" => EndFunction,
+        "FUNCTION_BLOCK" => FunctionBlock,
+        "END_FUNCTION_BLOCK" => EndFunctionBlock,
+        "VAR" => Var,
+        "VAR_INPUT" => VarInput,
+        "VAR_OUTPUT" => VarOutput,
+        "VAR_IN_OUT" => VarInOut,
+        "VAR_GLOBAL" => VarGlobal,
+        "VAR_TEMP" => VarTemp,
+        "VAR_EXTERNAL" => VarExternal,
+        "CONSTANT" => Constant,
+        "END_VAR" => EndVar,
+        "ARRAY" => Array,
+        "OF" => Of,
+        "IF" => If,
+        "THEN" => Then,
+        "ELSIF" => Elsif,
+        "ELSE" => Else,
+        "END_IF" => EndIf,
+        "CASE" => Case,
+        "END_CASE" => EndCase,
+        "FOR" => For,
+        "TO" => To,
+        "BY" => By,
+        "DO" => Do,
+        "END_FOR" => EndFor,
+        "WHILE" => While,
+        "END_WHILE" => EndWhile,
+        "REPEAT" => Repeat,
+        "UNTIL" => Until,
+        "END_REPEAT" => EndRepeat,
+        "RETURN" => Return,
+        "EXIT" => Exit,
+        "JMP" => Jmp,
+        "NOT" => Not,
+        "AND" => And,
+        "OR" => Or,
+        "XOR" => Xor,
+        "MOD" => Mod,
+        "TYPE" => Type,
+        "END_TYPE" => EndType,
+        "STRUCT" => Struct,
+        "END_STRUCT" => EndStruct,
+        _ => return None,
+    })
+}
+
+/// Tokenize `src`. Unknown characters are skipped (best-effort — a scanner must
+/// not die on odd input).
+pub fn lex(src: &str) -> Vec<Token> {
+    let chars: Vec<char> = src.chars().collect();
+    let mut i = 0usize;
+    let mut line = 1u32;
+    let mut out = Vec::new();
+
+    let bump_line = |c: char, line: &mut u32| {
+        if c == '\n' {
+            *line += 1;
+        }
+    };
+
+    while i < chars.len() {
+        let c = chars[i];
+
+        // Whitespace.
+        if c.is_whitespace() {
+            bump_line(c, &mut line);
+            i += 1;
+            continue;
+        }
+
+        // Line comment: //
+        if c == '/' && i + 1 < chars.len() && chars[i + 1] == '/' {
+            while i < chars.len() && chars[i] != '\n' {
+                i += 1;
+            }
+            continue;
+        }
+
+        // Block comment: (* ... *)
+        if c == '(' && i + 1 < chars.len() && chars[i + 1] == '*' {
+            i += 2;
+            while i + 1 < chars.len() && !(chars[i] == '*' && chars[i + 1] == ')') {
+                bump_line(chars[i], &mut line);
+                i += 1;
+            }
+            i = (i + 2).min(chars.len());
+            continue;
+        }
+
+        let tok_line = line;
+
+        // String literal: '...' or "..."
+        if c == '\'' || c == '"' {
+            let quote = c;
+            i += 1;
+            let mut s = String::new();
+            while i < chars.len() {
+                let ch = chars[i];
+                if ch == quote {
+                    // Doubled quote is an escaped quote.
+                    if i + 1 < chars.len() && chars[i + 1] == quote {
+                        s.push(quote);
+                        i += 2;
+                        continue;
+                    }
+                    i += 1;
+                    break;
+                }
+                bump_line(ch, &mut line);
+                s.push(ch);
+                i += 1;
+            }
+            out.push(Token {
+                kind: Tok::Str(s),
+                line: tok_line,
+            });
+            continue;
+        }
+
+        // Identifier / keyword / time literal / boolean.
+        if c.is_ascii_alphabetic() || c == '_' {
+            let start = i;
+            while i < chars.len() && (chars[i].is_ascii_alphanumeric() || chars[i] == '_') {
+                i += 1;
+            }
+            let word: String = chars[start..i].iter().collect();
+
+            // Duration/date/time literal prefix: T#, TIME#, DT#, D#, TOD#, LT# ...
+            if i < chars.len() && chars[i] == '#' {
+                let up = word.to_ascii_uppercase();
+                if matches!(
+                    up.as_str(),
+                    "T" | "TIME" | "DT" | "D" | "TOD" | "LT" | "DATE"
+                ) {
+                    let lit_start = start;
+                    i += 1; // consume '#'
+                    while i < chars.len()
+                        && (chars[i].is_ascii_alphanumeric()
+                            || chars[i] == '.'
+                            || chars[i] == '_'
+                            || chars[i] == ':')
+                    {
+                        i += 1;
+                    }
+                    let lit: String = chars[lit_start..i].iter().collect();
+                    out.push(Token {
+                        kind: Tok::Time(lit),
+                        line: tok_line,
+                    });
+                    continue;
+                }
+            }
+
+            let kind = match word.to_ascii_uppercase().as_str() {
+                "TRUE" => Tok::Bool(true),
+                "FALSE" => Tok::Bool(false),
+                _ => match keyword_from(&word) {
+                    Some(kw) => Tok::Kw(kw),
+                    None => Tok::Ident(word),
+                },
+            };
+            out.push(Token {
+                kind,
+                line: tok_line,
+            });
+            continue;
+        }
+
+        // Number: decimal, real, or based (16#..., 2#...).
+        if c.is_ascii_digit() {
+            let start = i;
+            while i < chars.len() && (chars[i].is_ascii_digit() || chars[i] == '_') {
+                i += 1;
+            }
+            // Based literal: <base>#<digits>
+            if i < chars.len() && chars[i] == '#' {
+                let base_str: String = chars[start..i].iter().filter(|c| **c != '_').collect();
+                i += 1;
+                let dstart = i;
+                while i < chars.len() && (chars[i].is_ascii_alphanumeric() || chars[i] == '_') {
+                    i += 1;
+                }
+                let digits: String = chars[dstart..i].iter().filter(|c| **c != '_').collect();
+                let radix = base_str.parse::<u32>().unwrap_or(10);
+                let val = i64::from_str_radix(&digits, radix.clamp(2, 36)).unwrap_or(0);
+                out.push(Token {
+                    kind: Tok::Int(val),
+                    line: tok_line,
+                });
+                continue;
+            }
+            // Real: has a '.' (not '..') or exponent.
+            let is_real =
+                i < chars.len() && chars[i] == '.' && !(i + 1 < chars.len() && chars[i + 1] == '.');
+            if is_real {
+                i += 1;
+                while i < chars.len() && (chars[i].is_ascii_digit() || chars[i] == '_') {
+                    i += 1;
+                }
+                let raw: String = chars[start..i].iter().filter(|c| **c != '_').collect();
+                out.push(Token {
+                    kind: Tok::Real(raw.parse().unwrap_or(0.0)),
+                    line: tok_line,
+                });
+                continue;
+            }
+            let raw: String = chars[start..i].iter().filter(|c| **c != '_').collect();
+            out.push(Token {
+                kind: Tok::Int(raw.parse().unwrap_or(0)),
+                line: tok_line,
+            });
+            continue;
+        }
+
+        // Operators / punctuation (longest match first).
+        let two: String = chars[i..(i + 2).min(chars.len())].iter().collect();
+        let kind = match two.as_str() {
+            ":=" => Some(Tok::Assign),
+            "<=" => Some(Tok::Le),
+            ">=" => Some(Tok::Ge),
+            "<>" => Some(Tok::Ne),
+            ".." => Some(Tok::DotDot),
+            "**" => Some(Tok::Power),
+            _ => None,
+        };
+        if let Some(k) = kind {
+            out.push(Token {
+                kind: k,
+                line: tok_line,
+            });
+            i += 2;
+            continue;
+        }
+        let one = match c {
+            '+' => Some(Tok::Plus),
+            '-' => Some(Tok::Minus),
+            '*' => Some(Tok::Star),
+            '/' => Some(Tok::Slash),
+            '(' => Some(Tok::LParen),
+            ')' => Some(Tok::RParen),
+            '[' => Some(Tok::LBrack),
+            ']' => Some(Tok::RBrack),
+            '.' => Some(Tok::Dot),
+            ',' => Some(Tok::Comma),
+            ';' => Some(Tok::Semi),
+            ':' => Some(Tok::Colon),
+            '<' => Some(Tok::Lt),
+            '>' => Some(Tok::Gt),
+            '=' => Some(Tok::Eq),
+            '&' => Some(Tok::Amp),
+            _ => None,
+        };
+        if let Some(k) = one {
+            out.push(Token {
+                kind: k,
+                line: tok_line,
+            });
+        }
+        i += 1;
+    }
+
+    out.push(Token {
+        kind: Tok::Eof,
+        line,
+    });
+    out
+}