parthchandra commented on code in PR #307:
URL: https://github.com/apache/datafusion-comet/pull/307#discussion_r1586606093
##########
core/src/execution/datafusion/expressions/cast.rs:
##########
@@ -142,6 +233,202 @@ impl Cast {
}
}
+/// Equivalent to org.apache.spark.unsafe.types.UTF8String.toByte
+fn cast_string_to_i8(str: &str, eval_mode: EvalMode) ->
CometResult<Option<i8>> {
+ Ok(cast_string_to_int_with_range_check(
+ str,
+ eval_mode,
+ "TINYINT",
+ i8::MIN as i32,
+ i8::MAX as i32,
+ )?
+ .map(|v| v as i8))
+}
+
+/// Equivalent to org.apache.spark.unsafe.types.UTF8String.toShort
+fn cast_string_to_i16(str: &str, eval_mode: EvalMode) ->
CometResult<Option<i16>> {
+ Ok(cast_string_to_int_with_range_check(
+ str,
+ eval_mode,
+ "SMALLINT",
+ i16::MIN as i32,
+ i16::MAX as i32,
+ )?
+ .map(|v| v as i16))
+}
+
+/// Equivalent to org.apache.spark.unsafe.types.UTF8String.toInt(IntWrapper
intWrapper)
+fn cast_string_to_i32(str: &str, eval_mode: EvalMode) ->
CometResult<Option<i32>> {
+ do_cast_string_to_int::<i32>(str, eval_mode, "INT", i32::MIN)
+}
+
+/// Equivalent to org.apache.spark.unsafe.types.UTF8String.toLong(LongWrapper
intWrapper)
+fn cast_string_to_i64(str: &str, eval_mode: EvalMode) ->
CometResult<Option<i64>> {
+ do_cast_string_to_int::<i64>(str, eval_mode, "BIGINT", i64::MIN)
+}
+
+fn cast_string_to_int_with_range_check(
+ str: &str,
+ eval_mode: EvalMode,
+ type_name: &str,
+ min: i32,
+ max: i32,
+) -> CometResult<Option<i32>> {
+ match do_cast_string_to_int(str, eval_mode, type_name, i32::MIN)? {
+ None => Ok(None),
+ Some(v) if v >= min && v <= max => Ok(Some(v)),
+ _ if eval_mode == EvalMode::Ansi => Err(invalid_value(str, "STRING",
type_name)),
+ _ => Ok(None),
+ }
+}
+
+#[derive(PartialEq)]
+enum State {
+ SkipLeadingWhiteSpace,
+ SkipTrailingWhiteSpace,
+ ParseSignAndDigits,
+ ParseFractionalDigits,
+}
+
+/// Equivalent to
+/// - org.apache.spark.unsafe.types.UTF8String.toInt(IntWrapper intWrapper,
boolean allowDecimal)
+/// - org.apache.spark.unsafe.types.UTF8String.toLong(LongWrapper longWrapper,
boolean allowDecimal)
+fn do_cast_string_to_int<
+ T: Num + PartialOrd + Integer + CheckedSub + CheckedNeg + From<i32> + Copy,
+>(
+ str: &str,
+ eval_mode: EvalMode,
+ type_name: &str,
+ min_value: T,
+) -> CometResult<Option<T>> {
+ let len = str.len();
+ if str.is_empty() {
+ return none_or_err(eval_mode, type_name, str);
+ }
+
+ let mut result: T = T::zero();
+ let mut negative = false;
+ let radix = T::from(10);
+ let stop_value = min_value / radix;
+ let mut state = State::SkipLeadingWhiteSpace;
+ let mut parsed_sign = false;
+
+ for (i, ch) in str.char_indices() {
+ // skip leading whitespace
+ if state == State::SkipLeadingWhiteSpace {
+ if ch.is_whitespace() {
+ // consume this char
+ continue;
+ }
+ // change state and fall through to next section
+ state = State::ParseSignAndDigits;
+ }
+
+ if state == State::ParseSignAndDigits {
+ if !parsed_sign {
+ negative = ch == '-';
+ let positive = ch == '+';
+ parsed_sign = true;
+ if negative || positive {
+ if i + 1 == len {
+ // input string is just "+" or "-"
+ return none_or_err(eval_mode, type_name, str);
+ }
+ // consume this char
+ continue;
+ }
+ }
+
+ if ch == '.' {
+ if eval_mode == EvalMode::Legacy {
+ // truncate decimal in legacy mode
+ state = State::ParseFractionalDigits;
+ continue;
+ } else {
+ return none_or_err(eval_mode, type_name, str);
+ }
+ }
+
+ let digit = if ch.is_ascii_digit() {
+ (ch as u32) - ('0' as u32)
+ } else {
+ return none_or_err(eval_mode, type_name, str);
+ };
+
+ // We are going to process the new digit and accumulate the
result. However, before
Review Comment:
A comment to explain why we're using subtraction instead of addition would
make it easier to understand this part of the code.
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