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// Copyright Amazon.com, Inc. or its affiliates.
use std::io::Write;
use std::ops::Neg;
use arrayvec::ArrayVec;
use chrono::{Datelike, Timelike};
use crate::binary::decimal::DecimalBinaryEncoder;
use crate::binary::var_int::VarInt;
use crate::binary::var_uint::VarUInt;
use crate::result::IonResult;
use crate::types::{Mantissa, TimestampPrecision};
use crate::{Decimal, Timestamp};
const MAX_INLINE_LENGTH: usize = 13;
const MAX_TIMESTAMP_LENGTH: usize = 32;
/// Provides support to write [`Timestamp`] into [Ion binary].
///
/// [Ion binary]: https://amazon-ion.github.io/ion-docs/docs/binary.html#6-timestamp
pub trait TimestampBinaryEncoder {
/// Encodes the content of a [`Timestamp`] as per the Ion binary encoding.
/// Returns the length of the encoded bytes.
///
/// This does not encode the type descriptor nor the associated length.
/// Prefer [`TimestampBinaryEncoder::encode_timestamp_value`] for that.
fn encode_timestamp(&mut self, timestamp: &Timestamp) -> IonResult<usize>;
/// Encodes a [`Timestamp`] as an Ion value with the type descriptor and length.
/// Returns the length of the encoded bytes.
fn encode_timestamp_value(&mut self, timestamp: &Timestamp) -> IonResult<usize>;
}
impl<W> TimestampBinaryEncoder for W
where
W: Write,
{
fn encode_timestamp(&mut self, timestamp: &Timestamp) -> IonResult<usize> {
const SECONDS_PER_MINUTE: f32 = 60f32;
let mut bytes_written: usize = 0;
// Each unit of the binary-encoded timestamp (hour, minute, etc) is written in UTC.
// The reader is expected to apply the encoded offset (in minutes) to derive the local time.
// [Timestamp]s are modeled as a UTC NaiveDateTime and an optional FixedOffset.
// We can use the UTC NaiveDateTime to query for the individual time fields (year, month,
// etc) that we need to write out.
let utc = timestamp.date_time;
// Write out the offset (minutes difference from UTC). If the offset is
// unknown, negative zero is used.
if let Some(offset) = timestamp.offset {
// Ion encodes offsets in minutes while chrono's DateTime stores it in seconds.
let offset_seconds = offset.local_minus_utc();
let offset_minutes = (offset_seconds as f32 / SECONDS_PER_MINUTE).round() as i64;
bytes_written += VarInt::write_i64(self, offset_minutes)?;
} else {
// The offset is unknown. Write negative zero.
bytes_written += VarInt::write_negative_zero(self)?;
}
bytes_written += VarUInt::write_u64(self, utc.year() as u64)?;
// So far, we've written required fields. The rest are optional!
if timestamp.precision > TimestampPrecision::Year {
bytes_written += VarUInt::write_u64(self, utc.month() as u64)?;
if timestamp.precision > TimestampPrecision::Month {
bytes_written += VarUInt::write_u64(self, utc.day() as u64)?;
if timestamp.precision > TimestampPrecision::Day {
bytes_written += VarUInt::write_u64(self, utc.hour() as u64)?;
bytes_written += VarUInt::write_u64(self, utc.minute() as u64)?;
if timestamp.precision > TimestampPrecision::HourAndMinute {
bytes_written += VarUInt::write_u64(self, utc.second() as u64)?;
if let Some(ref mantissa) = timestamp.fractional_seconds {
// TODO: Both branches encode directly due to one
// branch owning vs borrowing the decimal
// representation. #286 should provide a fix.
match mantissa {
Mantissa::Digits(precision) => {
// Consider the following case: `2000-01-01T00:00:00.123Z`.
// That's 123 millis, or 123,000,000 nanos.
// Our mantissa is 0.123, or 123d-3.
let scaled = utc.nanosecond() / 10u32.pow(9 - *precision); // 123,000,000 -> 123
let exponent = (*precision as i64).neg(); // -3
let fractional = Decimal::new(scaled, exponent); // 123d-3
bytes_written += self.encode_decimal(&fractional)?;
}
Mantissa::Arbitrary(decimal) => {
bytes_written += self.encode_decimal(decimal)?;
}
};
}
}
}
}
}
Ok(bytes_written)
}
fn encode_timestamp_value(&mut self, timestamp: &Timestamp) -> IonResult<usize> {
let mut bytes_written: usize = 0;
// First encode the timestamp. We need to know the encoded length before
// we can compute and write out the type descriptor.
let mut encoded: ArrayVec<u8, MAX_TIMESTAMP_LENGTH> = ArrayVec::new();
encoded.encode_timestamp(timestamp)?;
// Write the type descriptor and length.
let type_descriptor: u8;
if encoded.len() <= MAX_INLINE_LENGTH {
type_descriptor = 0x60 | encoded.len() as u8;
self.write_all(&[type_descriptor])?;
bytes_written += 1;
} else {
type_descriptor = 0x6E;
self.write_all(&[type_descriptor])?;
bytes_written += 1;
bytes_written += VarUInt::write_u64(self, encoded.len() as u64)?;
}
// Now we can write out the encoded timestamp!
self.write_all(&encoded[..])?;
bytes_written += &encoded[..].len();
Ok(bytes_written)
}
}
#[cfg(test)]
mod binary_timestamp_tests {
use super::*;
use crate::lazy::any_encoding::AnyEncoding;
use crate::lazy::reader::Reader;
use rstest::*;
// These tests show how varying levels of precision affects number of bytes
// written (for binary encoding of timestamps).
#[rstest]
#[case::y2k_utc("2000-01-01T00:00:00+00:00", 9)]
#[case::seconds_utc("2021-01-08T14:12:36+00:00", 9)]
#[case::seconds_tz("2021-01-08T14:12:36-05:00", 10)]
#[case::millis_tz("2021-01-08T14:12:36.888-05:00", 13)]
#[case::micros_tz("2021-01-08T14:12:36.888888-05:00", 14)]
#[case::nanos_tz("2021-01-08T14:12:36.888888888-05:00", 16)]
fn timestamp_encoding_bytes_written(
#[case] input: &str,
#[case] expected: usize,
) -> IonResult<()> {
let mut reader = Reader::new(AnyEncoding, input)?;
let timestamp = reader.expect_next()?.read()?.expect_timestamp()?;
let mut buf = vec![];
let written = buf.encode_timestamp_value(×tamp)?;
assert_eq!(buf.len(), expected);
assert_eq!(written, expected);
Ok(())
}
}