[GitHub] [arrow-rs] tustvold commented on a diff in pull request #3043: Move reader_parser to arrow-cast (#3022)

[GitBox <gi...@apache.org>]

tustvold commented on code in PR #3043:
URL: https://github.com/apache/arrow-rs/pull/3043#discussion_r1015882812


##########
arrow-cast/src/parse.rs:
##########
@@ -130,6 +132,126 @@ pub fn string_to_timestamp_nanos(s: &str) -> Result<i64, ArrowError> {
     )))
 }
 
+/// Specialized parsing implementations
+/// used by csv and json reader
+pub trait Parser: ArrowPrimitiveType {
+    fn parse(string: &str) -> Option<Self::Native>;
+
+    fn parse_formatted(string: &str, _format: &str) -> Option<Self::Native> {
+        Self::parse(string)
+    }
+}
+
+impl Parser for Float32Type {
+    fn parse(string: &str) -> Option<f32> {
+        lexical_core::parse(string.as_bytes()).ok()
+    }
+}
+
+impl Parser for Float64Type {
+    fn parse(string: &str) -> Option<f64> {
+        lexical_core::parse(string.as_bytes()).ok()
+    }
+}
+
+macro_rules! parser_primitive {
+    ($t:ty) => {
+        impl Parser for $t {
+            fn parse(string: &str) -> Option<Self::Native> {
+                string.parse::<Self::Native>().ok()
+            }
+        }
+    };
+}
+parser_primitive!(UInt64Type);
+parser_primitive!(UInt32Type);
+parser_primitive!(UInt16Type);
+parser_primitive!(UInt8Type);
+parser_primitive!(Int64Type);
+parser_primitive!(Int32Type);
+parser_primitive!(Int16Type);
+parser_primitive!(Int8Type);
+
+impl Parser for TimestampNanosecondType {
+    fn parse(string: &str) -> Option<i64> {
+        string_to_timestamp_nanos(string).ok()
+    }
+}
+
+impl Parser for TimestampMicrosecondType {
+    fn parse(string: &str) -> Option<i64> {
+        let nanos = string_to_timestamp_nanos(string).ok();
+        nanos.map(|x| x / 1000)
+    }
+}
+
+impl Parser for TimestampMillisecondType {
+    fn parse(string: &str) -> Option<i64> {
+        let nanos = string_to_timestamp_nanos(string).ok();
+        nanos.map(|x| x / 1_000_000)
+    }
+}
+
+impl Parser for TimestampSecondType {
+    fn parse(string: &str) -> Option<i64> {
+        let nanos = string_to_timestamp_nanos(string).ok();
+        nanos.map(|x| x / 1_000_000_000)
+    }
+}
+
+parser_primitive!(Time64NanosecondType);
+parser_primitive!(Time64MicrosecondType);
+parser_primitive!(Time32MillisecondType);
+parser_primitive!(Time32SecondType);
+
+/// Number of days between 0001-01-01 and 1970-01-01
+const EPOCH_DAYS_FROM_CE: i32 = 719_163;

Review Comment:
   I think arrow_array::temporal_conversions has most of them now. In general I hope we can avoid an arrow-common, util libraries have a tendency to become generic dumping grounds without clear focus :sweat_smile: 



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