1 files changed, 52 insertions, 0 deletions
diff --git a/src/parsers/constant_expression.rs b/src/parsers/constant_expression.rs
new file mode 100644
index 0000000..78dc697
--- /dev/null
+++ b/src/parsers/constant_expression.rs
@@ -0,0 +1,52 @@
+use crate::*;
+
+
+pub fn parse_constant_expression(string: &str, parent: &Tokeniser) -> ConstantExpression {
+    use ConstantExpressionTokenVariant as TokenVar;
+    use ConstantExpressionParseError as ParseError;
+
+    let mut tokens = Vec::new();
+    let mut t = Tokeniser::new_child(string, parent);
+    t.position.to_next_char();  // skip opening delimiter
+
+    loop {
+        t.drop_whitespace();
+        t.mark_start_position();
+        let token = t.eat_token();
+        if token.is_empty() {
+            break;
+        }
+
+        let variant = match token.as_str() {
+            "=" => TokenVar::Operator(Operator::Equal),
+            "!" => TokenVar::Operator(Operator::NotEqual),
+            "<" => TokenVar::Operator(Operator::LessThan),
+            ">" => TokenVar::Operator(Operator::GreaterThan),
+            "+" => TokenVar::Operator(Operator::Add),
+            "-" => TokenVar::Operator(Operator::Subtract),
+            "<<" => TokenVar::Operator(Operator::LeftShift),
+            ">>" => TokenVar::Operator(Operator::RightShift),
+            "&" => TokenVar::Operator(Operator::And),
+            "|" => TokenVar::Operator(Operator::Or),
+            "^" => TokenVar::Operator(Operator::Xor),
+            "~" => TokenVar::Operator(Operator::Not),
+            _ => if let Some(stripped) = token.strip_prefix("0x") {
+                match usize::from_str_radix(stripped, 16) {
+                    Ok(value) => TokenVar::IntegerLiteral(value),
+                    Err(_) => TokenVar::Error(
+                        ParseError::InvalidHexadecimalLiteral(stripped.to_string())),
+                }
+            } else {
+                match usize::from_str_radix(&token, 10) {
+                    Ok(value) => TokenVar::IntegerLiteral(value),
+                    Err(_) => TokenVar::SymbolReference(token.to_string()),
+                }
+            }
+        };
+
+        let source = t.mark_end_position();
+        tokens.push(ConstantExpressionToken { source, variant });
+    }
+
+    return ConstantExpression { tokens };
+}