fory-core 1.0.0

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

use crate::buffer::{Reader, Writer};
use crate::context::{ReadContext, WriteContext};
use crate::error::Error;
use crate::resolver::TypeResolver;
use crate::serializer::util::read_basic_type_info;
use crate::serializer::{ForyDefault, Serializer};
use crate::type_id::TypeId;
use crate::types::Decimal;
use num_bigint::{BigInt, Sign};
use std::convert::TryFrom;

impl Serializer for Decimal {
    #[inline(always)]
    fn fory_write_data(&self, context: &mut WriteContext) -> Result<(), Error> {
        context.writer.write_var_i32(self.scale);
        write_decimal_unscaled(&self.unscaled, &mut context.writer)
    }

    #[inline(always)]
    fn fory_read_data(context: &mut ReadContext) -> Result<Self, Error> {
        let scale = context.reader.read_var_i32()?;
        let unscaled = read_decimal_unscaled(&mut context.reader)?;
        Ok(Self { unscaled, scale })
    }

    #[inline(always)]
    fn fory_get_type_id(_: &TypeResolver) -> Result<TypeId, Error> {
        Ok(TypeId::DECIMAL)
    }

    #[inline(always)]
    fn fory_type_id_dyn(&self, _: &TypeResolver) -> Result<TypeId, Error> {
        Ok(TypeId::DECIMAL)
    }

    #[inline(always)]
    fn fory_static_type_id() -> TypeId {
        TypeId::DECIMAL
    }

    #[inline(always)]
    fn as_any(&self) -> &dyn std::any::Any {
        self
    }

    #[inline(always)]
    fn fory_write_type_info(context: &mut WriteContext) -> Result<(), Error> {
        context.writer.write_var_u32(TypeId::DECIMAL as u32);
        Ok(())
    }

    #[inline(always)]
    fn fory_read_type_info(context: &mut ReadContext) -> Result<(), Error> {
        read_basic_type_info::<Self>(context)
    }
}

impl ForyDefault for Decimal {
    #[inline(always)]
    fn fory_default() -> Self {
        Self {
            unscaled: BigInt::from(0),
            scale: 0,
        }
    }
}

fn write_decimal_unscaled(value: &BigInt, writer: &mut Writer) -> Result<(), Error> {
    if let Some(small_value) = can_use_small_encoding(value) {
        writer.write_var_u64(encode_zigzag64(small_value) << 1);
        return Ok(());
    }

    let (sign, payload) = value.to_bytes_le();
    if payload.is_empty() {
        return Err(Error::invalid_data(
            "zero must use the small decimal encoding".to_string(),
        ));
    }
    let meta = ((payload.len() as u64) << 1) | u64::from(matches!(sign, Sign::Minus));
    writer.write_var_u64((meta << 1) | 1);
    writer.write_bytes(&payload);
    Ok(())
}

fn read_decimal_unscaled(reader: &mut Reader) -> Result<BigInt, Error> {
    let header = reader.read_var_u64()?;
    if (header & 1) == 0 {
        return Ok(BigInt::from(decode_zigzag64(header >> 1)));
    }

    let meta = header >> 1;
    let sign = (meta & 1) != 0;
    let len = (meta >> 1) as usize;
    if len == 0 {
        return Err(Error::invalid_data(
            "invalid decimal magnitude length 0".to_string(),
        ));
    }
    let payload = reader.read_bytes(len)?;
    if payload[len - 1] == 0 {
        return Err(Error::invalid_data(
            "non-canonical decimal payload: trailing zero byte".to_string(),
        ));
    }
    let magnitude = BigInt::from_bytes_le(Sign::Plus, payload);
    if magnitude == BigInt::from(0) {
        return Err(Error::invalid_data(
            "big decimal encoding must not represent zero".to_string(),
        ));
    }
    Ok(if sign { -magnitude } else { magnitude })
}

fn can_use_small_encoding(value: &BigInt) -> Option<i64> {
    let small_value = i64::try_from(value).ok()?;
    if (encode_zigzag64(small_value) & (1u64 << 63)) == 0 {
        Some(small_value)
    } else {
        None
    }
}

#[inline(always)]
fn encode_zigzag64(value: i64) -> u64 {
    ((value << 1) ^ (value >> 63)) as u64
}

#[inline(always)]
fn decode_zigzag64(value: u64) -> i64 {
    ((value >> 1) as i64) ^ -((value & 1) as i64)
}