avm2: Re-use code in coerce_to_number

Use `string_to_f64` and `string_to_int`, as [`MathUtils::convertStringToNumber`](https://github.com/adobe/avmplus/blob/858d034a3bd3a54d9b70909386435cf4aec81d21/core/MathUtils.cpp#L453-L466)
in avmplus does.

Author: relrelb

core/src/avm2/globals/toplevel.rs

@@ -54,82 +54,6 @@ pub fn is_nan<'gc>(
     }
 }
 
-/// Converts a `WStr` to an integer (as an `f64`).
-///
-/// This function might fail for some invalid inputs, by returning `f64::NAN`.
-///
-/// `radix` is only valid in the range `2..=36`, plus the special `0` value, which means the
-/// radix is inferred from the string; hexadecimal if it starts with a `0x` prefix (case
-/// insensitive), or decimal otherwise.
-/// `strict` tells whether to fail on trailing garbage, or ignore it.
-fn string_to_int(mut s: &WStr, mut radix: i32, strict: bool) -> f64 {
-    // Allow leading whitespace.
-    skip_spaces(&mut s);
-
-    let is_negative = parse_sign(&mut s);
-
-    if radix == 16 || radix == 0 {
-        if let Some(after_0x) = s
-            .strip_prefix(WStr::from_units(b"0x"))
-            .or_else(|| s.strip_prefix(WStr::from_units(b"0X")))
-        {
-            // Consume hexadecimal prefix.
-            s = after_0x;
-
-            // Explicit hexadecimal.
-            radix = 16;
-        } else if radix == 0 {
-            // Default to decimal.
-            radix = 10;
-        }
-    }
-
-    // Fail on invalid radix or blank string.
-    if !(2..=36).contains(&radix) || s.is_empty() {
-        return f64::NAN;
-    }
-
-    // Actual number parsing.
-    let mut result = 0.0;
-    let start = s;
-    s = s.trim_start_matches(|c| {
-        match u8::try_from(c)
-            .ok()
-            .and_then(|c| char::from(c).to_digit(radix as u32))
-        {
-            Some(digit) => {
-                result *= f64::from(radix);
-                result += f64::from(digit);
-                true
-            }
-            None => false,
-        }
-    });
-
-    // Fail if we got no digits.
-    // TODO: Compare by reference instead?
-    if s.len() == start.len() {
-        return f64::NAN;
-    }
-
-    if strict {
-        // Allow trailing whitespace.
-        skip_spaces(&mut s);
-
-        // Fail if we got digits, but we're in strict mode and not at end of string.
-        if !s.is_empty() {
-            return f64::NAN;
-        }
-    }
-
-    // Apply sign.
-    if is_negative {
-        result = -result;
-    }
-
-    result
-}
-
 pub fn parse_int<'gc>(
     activation: &mut Activation<'_, 'gc, '_>,
     _this: Option<Object<'gc>>,
@@ -145,224 +69,10 @@ pub fn parse_int<'gc>(
         None => 0,
     };
 
-    let result = string_to_int(&string, radix, false);
+    let result = crate::avm2::value::string_to_int(&string, radix, false);
     Ok(result.into())
 }
 
-/// Strips leading whitespace.
-fn skip_spaces(s: &mut &WStr) {
-    *s = s.trim_start_matches(|c| {
-        matches!(
-            c,
-            0x20 | 0x09 | 0x0d | 0x0a | 0x0c | 0x0b | 0x2000
-                ..=0x200b | 0x2028 | 0x2029 | 0x205f | 0x3000
-        )
-    });
-}
-
-/// Consumes an optional sign character.
-/// Returns whether a minus sign was consumed.
-fn parse_sign(s: &mut &WStr) -> bool {
-    if let Some(after_sign) = s.strip_prefix(b'-') {
-        *s = after_sign;
-        true
-    } else if let Some(after_sign) = s.strip_prefix(b'+') {
-        *s = after_sign;
-        false
-    } else {
-        false
-    }
-}
-
-/// Converts a `WStr` to an `f64`.
-///
-/// This function might fail for some invalid inputs, by returning `None`.
-///
-/// `strict` typically tells whether to behave like `Number()` or `parseFloat()`:
-/// * `strict == true` fails on trailing garbage, but interprets blank strings (which are empty or consist only of whitespace) as zero.
-/// * `strict == false` ignores trailing garbage, but fails on blank strings.
-fn string_to_f64(mut s: &WStr, swf_version: u8, strict: bool) -> Option<f64> {
-    fn is_ascii_digit(c: u16) -> bool {
-        u8::try_from(c).map_or(false, |c| c.is_ascii_digit())
-    }
-
-    // Allow leading whitespace.
-    skip_spaces(&mut s);
-
-    // Handle blank strings as described above.
-    if s.is_empty() {
-        return if strict { Some(0.0) } else { None };
-    }
-
-    // Parse sign.
-    let is_negative = parse_sign(&mut s);
-    let after_sign = s;
-
-    // Count digits before decimal point.
-    s = s.trim_start_matches(is_ascii_digit);
-    let mut total_digits = after_sign.len() - s.len();
-
-    // Count digits after decimal point.
-    if let Some(after_dot) = s.strip_prefix(b'.') {
-        s = after_dot;
-        s = s.trim_start_matches(is_ascii_digit);
-        total_digits += after_dot.len() - s.len();
-    }
-
-    // Handle exponent.
-    let mut exponent: i32 = 0;
-    if let Some(after_e) = s.strip_prefix(b"eE".as_ref()) {
-        s = after_e;
-
-        // Parse exponent sign.
-        let exponent_is_negative = parse_sign(&mut s);
-
-        // Fail if string ends with "e-" with no exponent value specified.
-        if exponent_is_negative && s.is_empty() {
-            return None;
-        }
-
-        // Parse exponent itself.
-        s = s.trim_start_matches(|c| {
-            match u8::try_from(c)
-                .ok()
-                .and_then(|c| char::from(c).to_digit(10))
-            {
-                Some(digit) => {
-                    exponent = exponent.wrapping_mul(10);
-                    exponent = exponent.wrapping_add(digit as i32);
-                    true
-                }
-                None => false,
-            }
-        });
-
-        // Apply exponent sign.
-        if exponent_is_negative {
-            exponent = exponent.wrapping_neg();
-        }
-    }
-
-    // Allow trailing whitespace.
-    skip_spaces(&mut s);
-
-    // If we got no digits, check for Infinity/-Infinity. Otherwise fail.
-    if total_digits == 0 {
-        if let Some(after_infinity) = s.strip_prefix(WStr::from_units(b"Infinity")) {
-            s = after_infinity;
-
-            // Allow end of string or a whitespace. Otherwise fail.
-            if !s.is_empty() {
-                skip_spaces(&mut s);
-                // TODO: Compare by reference instead?
-                if s.len() == after_infinity.len() {
-                    return None;
-                }
-            }
-
-            let result = if is_negative {
-                f64::NEG_INFINITY
-            } else {
-                f64::INFINITY
-            };
-            return Some(result);
-        }
-        return None;
-    }
-
-    // Fail if we got digits, but we're in strict mode and not at end of string or at a null character.
-    if strict && !s.is_empty() && !s.starts_with(b'\0') {
-        return None;
-    }
-
-    // Bug compatibility: https://bugzilla.mozilla.org/show_bug.cgi?id=513018
-    let s = if swf_version >= 11 {
-        &after_sign[..after_sign.len() - s.len()]
-    } else {
-        after_sign
-    };
-
-    // Finally, calculate the result.
-    let mut result = if total_digits > 15 {
-        // With more than 15 digits, avmplus uses integer arithmetic to avoid rounding errors.
-        let mut result: i64 = 0;
-        let mut decimal_digits = -1;
-        for c in s {
-            if let Some(digit) = u8::try_from(c)
-                .ok()
-                .and_then(|c| char::from(c).to_digit(10))
-            {
-                if decimal_digits != -1 {
-                    decimal_digits += 1;
-                }
-
-                result *= 10;
-                result += i64::from(digit);
-            } else if c == b'.' as u16 {
-                decimal_digits = 0;
-            } else {
-                break;
-            }
-        }
-
-        if decimal_digits > 0 {
-            exponent -= decimal_digits;
-        }
-
-        if exponent > 0 {
-            result *= i64::pow(10, exponent as u32);
-        }
-
-        result as f64
-    } else {
-        let mut result = 0.0;
-        let mut decimal_digits = -1;
-        for c in s {
-            if let Some(digit) = u8::try_from(c)
-                .ok()
-                .and_then(|c| char::from(c).to_digit(10))
-            {
-                if decimal_digits != -1 {
-                    decimal_digits += 1;
-                }
-
-                result *= 10.0;
-                result += digit as f64;
-            } else if c == b'.' as u16 {
-                decimal_digits = 0;
-            } else {
-                break;
-            }
-        }
-
-        if decimal_digits > 0 {
-            exponent -= decimal_digits;
-        }
-
-        if exponent > 0 {
-            result *= f64::powi(10.0, exponent);
-        }
-
-        result
-    };
-
-    if exponent < 0 {
-        if exponent < -307 {
-            let diff = exponent + 307;
-            result /= f64::powi(10.0, -diff);
-            exponent = -307;
-        }
-        result /= f64::powi(10.0, -exponent);
-    }
-
-    // Apply sign.
-    if is_negative {
-        result = -result;
-    }
-
-    Some(result)
-}
-
 pub fn parse_float<'gc>(
     activation: &mut Activation<'_, 'gc, '_>,
     _this: Option<Object<'gc>>,
@@ -371,7 +81,7 @@ pub fn parse_float<'gc>(
     if let Some(value) = args.get(0) {
         let string = value.coerce_to_string(activation)?;
         let swf_version = activation.context.swf.version();
-        if let Some(result) = string_to_f64(&string, swf_version, false) {
+        if let Some(result) = crate::avm2::value::string_to_f64(&string, swf_version, false) {
             return Ok(result.into());
         }
     }