array_string.rs

// 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 std::convert::From;
use std::fmt;
use std::{any::Any, iter::FromIterator};

use super::{
    array::print_long_array, raw_pointer::RawPtrBox, Array, ArrayData, GenericListArray,
    GenericStringIter, OffsetSizeTrait,
};
use crate::buffer::Buffer;
use crate::util::bit_util;
use crate::{buffer::MutableBuffer, datatypes::DataType};

/// Like OffsetSizeTrait, but specialized for Strings
// This allow us to expose a constant datatype for the GenericStringArray
pub trait StringOffsetSizeTrait: OffsetSizeTrait {
    const DATA_TYPE: DataType;
}

impl StringOffsetSizeTrait for i32 {
    const DATA_TYPE: DataType = DataType::Utf8;
}

impl StringOffsetSizeTrait for i64 {
    const DATA_TYPE: DataType = DataType::LargeUtf8;
}

/// Generic struct for \[Large\]StringArray
///
/// See [`StringArray`] and [`LargeStringArray`] for storing
/// specific string data.
pub struct GenericStringArray<OffsetSize: StringOffsetSizeTrait> {
    data: ArrayData,
    value_offsets: RawPtrBox<OffsetSize>,
    value_data: RawPtrBox<u8>,
}

impl<OffsetSize: StringOffsetSizeTrait> GenericStringArray<OffsetSize> {
    /// Returns the length for the element at index `i`.
    #[inline]
    pub fn value_length(&self, i: usize) -> OffsetSize {
        let offsets = self.value_offsets();
        offsets[i + 1] - offsets[i]
    }

    /// Returns the offset values in the offsets buffer
    #[inline]
    pub fn value_offsets(&self) -> &[OffsetSize] {
        // Soundness
        //     pointer alignment & location is ensured by RawPtrBox
        //     buffer bounds/offset is ensured by the ArrayData instance.
        unsafe {
            std::slice::from_raw_parts(
                self.value_offsets.as_ptr().add(self.data.offset()),
                self.len() + 1,
            )
        }
    }

    /// Returns a clone of the value data buffer
    pub fn value_data(&self) -> Buffer {
        self.data.buffers()[1].clone()
    }

    /// Returns the element at index
    /// # Safety
    /// caller is responsible for ensuring that index is within the array bounds
    #[inline]
    pub unsafe fn value_unchecked(&self, i: usize) -> &str {
        let end = self.value_offsets().get_unchecked(i + 1);
        let start = self.value_offsets().get_unchecked(i);

        // Soundness
        // pointer alignment & location is ensured by RawPtrBox
        // buffer bounds/offset is ensured by the value_offset invariants
        // ISSUE: utf-8 well formedness is not checked

        // Safety of `to_isize().unwrap()`
        // `start` and `end` are &OffsetSize, which is a generic type that implements the
        // OffsetSizeTrait. Currently, only i32 and i64 implement OffsetSizeTrait,
        // both of which should cleanly cast to isize on an architecture that supports
        // 32/64-bit offsets
        let slice = std::slice::from_raw_parts(
            self.value_data.as_ptr().offset(start.to_isize().unwrap()),
            (*end - *start).to_usize().unwrap(),
        );
        std::str::from_utf8_unchecked(slice)
    }

    /// Returns the element at index `i` as &str
    #[inline]
    pub fn value(&self, i: usize) -> &str {
        assert!(i < self.data.len(), "StringArray out of bounds access");
        // Safety:
        // `i < self.data.len()
        unsafe { self.value_unchecked(i) }
    }

    fn from_list(v: GenericListArray<OffsetSize>) -> Self {
        assert_eq!(
            v.data().child_data()[0].child_data().len(),
            0,
            "StringArray can only be created from list array of u8 values \
             (i.e. List<PrimitiveArray<u8>>)."
        );
        assert_eq!(
            v.data().child_data()[0].data_type(),
            &DataType::UInt8,
            "StringArray can only be created from List<u8> arrays, mismatched data types."
        );

        let mut builder = ArrayData::builder(OffsetSize::DATA_TYPE)
            .len(v.len())
            .add_buffer(v.data().buffers()[0].clone())
            .add_buffer(v.data().child_data()[0].buffers()[0].clone());
        if let Some(bitmap) = v.data().null_bitmap() {
            builder = builder.null_bit_buffer(bitmap.bits.clone())
        }

        let array_data = unsafe { builder.build_unchecked() };
        Self::from(array_data)
    }

    pub(crate) fn from_vec<Ptr>(v: Vec<Ptr>) -> Self
    where
        Ptr: AsRef<str>,
    {
        let mut offsets =
            MutableBuffer::new((v.len() + 1) * std::mem::size_of::<OffsetSize>());
        let mut values = MutableBuffer::new(0);

        let mut length_so_far = OffsetSize::zero();
        offsets.push(length_so_far);

        for s in &v {
            length_so_far += OffsetSize::from_usize(s.as_ref().len()).unwrap();
            offsets.push(length_so_far);
            values.extend_from_slice(s.as_ref().as_bytes());
        }
        let array_data = ArrayData::builder(OffsetSize::DATA_TYPE)
            .len(v.len())
            .add_buffer(offsets.into())
            .add_buffer(values.into());
        let array_data = unsafe { array_data.build_unchecked() };
        Self::from(array_data)
    }

    pub(crate) fn from_opt_vec(v: Vec<Option<&str>>) -> Self {
        v.into_iter().collect()
    }

    /// Creates a `GenericStringArray` based on an iterator of values without nulls
    pub fn from_iter_values<Ptr, I: IntoIterator<Item = Ptr>>(iter: I) -> Self
    where
        Ptr: AsRef<str>,
    {
        let iter = iter.into_iter();
        let (_, data_len) = iter.size_hint();
        let data_len = data_len.expect("Iterator must be sized"); // panic if no upper bound.

        let mut offsets =
            MutableBuffer::new((data_len + 1) * std::mem::size_of::<OffsetSize>());
        let mut values = MutableBuffer::new(0);

        let mut length_so_far = OffsetSize::zero();
        offsets.push(length_so_far);

        for i in iter {
            let s = i.as_ref();
            length_so_far += OffsetSize::from_usize(s.len()).unwrap();
            offsets.push(length_so_far);
            values.extend_from_slice(s.as_bytes());
        }
        let array_data = ArrayData::builder(OffsetSize::DATA_TYPE)
            .len(data_len)
            .add_buffer(offsets.into())
            .add_buffer(values.into());
        let array_data = unsafe { array_data.build_unchecked() };
        Self::from(array_data)
    }
}

impl<'a, Ptr, OffsetSize: StringOffsetSizeTrait> FromIterator<&'a Option<Ptr>>
    for GenericStringArray<OffsetSize>
where
    Ptr: AsRef<str> + 'a,
{
    /// Creates a [`GenericStringArray`] based on an iterator of `Option` references.
    fn from_iter<I: IntoIterator<Item = &'a Option<Ptr>>>(iter: I) -> Self {
        // Convert each owned Ptr into &str and wrap in an owned `Option`
        let iter = iter.into_iter().map(|o| o.as_ref().map(|p| p.as_ref()));
        // Build a `GenericStringArray` with the resulting iterator
        iter.collect::<GenericStringArray<OffsetSize>>()
    }
}

impl<'a, Ptr, OffsetSize: StringOffsetSizeTrait> FromIterator<Option<Ptr>>
    for GenericStringArray<OffsetSize>
where
    Ptr: AsRef<str>,
{
    /// Creates a [`GenericStringArray`] based on an iterator of `Option`s
    fn from_iter<I: IntoIterator<Item = Option<Ptr>>>(iter: I) -> Self {
        let iter = iter.into_iter();
        let (_, data_len) = iter.size_hint();
        let data_len = data_len.expect("Iterator must be sized"); // panic if no upper bound.

        let offset_size = std::mem::size_of::<OffsetSize>();
        let mut offsets = MutableBuffer::new((data_len + 1) * offset_size);
        let mut values = MutableBuffer::new(0);
        let mut null_buf = MutableBuffer::new_null(data_len);
        let null_slice = null_buf.as_slice_mut();
        let mut length_so_far = OffsetSize::zero();
        offsets.push(length_so_far);

        for (i, s) in iter.enumerate() {
            let value_bytes = if let Some(ref s) = s {
                // set null bit
                bit_util::set_bit(null_slice, i);
                let s_bytes = s.as_ref().as_bytes();
                length_so_far += OffsetSize::from_usize(s_bytes.len()).unwrap();
                s_bytes
            } else {
                b""
            };
            values.extend_from_slice(value_bytes);
            offsets.push(length_so_far);
        }

        // calculate actual data_len, which may be different from the iterator's upper bound
        let data_len = (offsets.len() / offset_size) - 1;
        let array_data = ArrayData::builder(OffsetSize::DATA_TYPE)
            .len(data_len)
            .add_buffer(offsets.into())
            .add_buffer(values.into())
            .null_bit_buffer(null_buf.into());
        let array_data = unsafe { array_data.build_unchecked() };
        Self::from(array_data)
    }
}

impl<'a, T: StringOffsetSizeTrait> IntoIterator for &'a GenericStringArray<T> {
    type Item = Option<&'a str>;
    type IntoIter = GenericStringIter<'a, T>;

    fn into_iter(self) -> Self::IntoIter {
        GenericStringIter::<'a, T>::new(self)
    }
}

impl<'a, T: StringOffsetSizeTrait> GenericStringArray<T> {
    /// constructs a new iterator
    pub fn iter(&'a self) -> GenericStringIter<'a, T> {
        GenericStringIter::<'a, T>::new(self)
    }
}

impl<OffsetSize: StringOffsetSizeTrait> fmt::Debug for GenericStringArray<OffsetSize> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let prefix = if OffsetSize::is_large() { "Large" } else { "" };

        write!(f, "{}StringArray\n[\n", prefix)?;
        print_long_array(self, f, |array, index, f| {
            fmt::Debug::fmt(&array.value(index), f)
        })?;
        write!(f, "]")
    }
}

impl<OffsetSize: StringOffsetSizeTrait> Array for GenericStringArray<OffsetSize> {
    fn as_any(&self) -> &dyn Any {
        self
    }

    fn data(&self) -> &ArrayData {
        &self.data
    }
}

impl<OffsetSize: StringOffsetSizeTrait> From<ArrayData>
    for GenericStringArray<OffsetSize>
{
    fn from(data: ArrayData) -> Self {
        assert_eq!(
            data.data_type(),
            &<OffsetSize as StringOffsetSizeTrait>::DATA_TYPE,
            "[Large]StringArray expects Datatype::[Large]Utf8"
        );
        assert_eq!(
            data.buffers().len(),
            2,
            "StringArray data should contain 2 buffers only (offsets and values)"
        );
        let offsets = data.buffers()[0].as_ptr();
        let values = data.buffers()[1].as_ptr();
        Self {
            data,
            value_offsets: unsafe { RawPtrBox::new(offsets) },
            value_data: unsafe { RawPtrBox::new(values) },
        }
    }
}

impl<OffsetSize: StringOffsetSizeTrait> From<Vec<Option<&str>>>
    for GenericStringArray<OffsetSize>
{
    fn from(v: Vec<Option<&str>>) -> Self {
        GenericStringArray::<OffsetSize>::from_opt_vec(v)
    }
}

impl<OffsetSize: StringOffsetSizeTrait> From<Vec<&str>>
    for GenericStringArray<OffsetSize>
{
    fn from(v: Vec<&str>) -> Self {
        GenericStringArray::<OffsetSize>::from_vec(v)
    }
}

impl<OffsetSize: StringOffsetSizeTrait> From<Vec<String>>
    for GenericStringArray<OffsetSize>
{
    fn from(v: Vec<String>) -> Self {
        GenericStringArray::<OffsetSize>::from_vec(v)
    }
}

/// An array where each element is a variable-sized sequence of bytes representing a string
/// whose maximum length (in bytes) is represented by a i32.
///
/// Example
///
/// ```
/// use arrow::array::StringArray;
/// let array = StringArray::from(vec![Some("foo"), None, Some("bar")]);
/// assert_eq!(array.value(0), "foo");
/// ```
pub type StringArray = GenericStringArray<i32>;

/// An array where each element is a variable-sized sequence of bytes representing a string
/// whose maximum length (in bytes) is represented by a i64.
///
/// Example
///
/// ```
/// use arrow::array::LargeStringArray;
/// let array = LargeStringArray::from(vec![Some("foo"), None, Some("bar")]);
/// assert_eq!(array.value(2), "bar");
/// ```
pub type LargeStringArray = GenericStringArray<i64>;

impl<T: StringOffsetSizeTrait> From<GenericListArray<T>> for GenericStringArray<T> {
    fn from(v: GenericListArray<T>) -> Self {
        GenericStringArray::<T>::from_list(v)
    }
}

#[cfg(test)]
mod tests {

    use crate::array::{ListBuilder, StringBuilder};

    use super::*;

    #[test]
    fn test_string_array_from_u8_slice() {
        let values: Vec<&str> = vec!["hello", "", "parquet"];

        // Array data: ["hello", "", "parquet"]
        let string_array = StringArray::from(values);

        assert_eq!(3, string_array.len());
        assert_eq!(0, string_array.null_count());
        assert_eq!("hello", string_array.value(0));
        assert_eq!("hello", unsafe { string_array.value_unchecked(0) });
        assert_eq!("", string_array.value(1));
        assert_eq!("", unsafe { string_array.value_unchecked(1) });
        assert_eq!("parquet", string_array.value(2));
        assert_eq!("parquet", unsafe { string_array.value_unchecked(2) });
        assert_eq!(5, string_array.value_offsets()[2]);
        assert_eq!(7, string_array.value_length(2));
        for i in 0..3 {
            assert!(string_array.is_valid(i));
            assert!(!string_array.is_null(i));
        }
    }

    #[test]
    #[should_panic(expected = "[Large]StringArray expects Datatype::[Large]Utf8")]
    fn test_string_array_from_int() {
        let array = LargeStringArray::from(vec!["a", "b"]);
        drop(StringArray::from(array.data().clone()));
    }

    #[test]
    fn test_large_string_array_from_u8_slice() {
        let values: Vec<&str> = vec!["hello", "", "parquet"];

        // Array data: ["hello", "", "parquet"]
        let string_array = LargeStringArray::from(values);

        assert_eq!(3, string_array.len());
        assert_eq!(0, string_array.null_count());
        assert_eq!("hello", string_array.value(0));
        assert_eq!("hello", unsafe { string_array.value_unchecked(0) });
        assert_eq!("", string_array.value(1));
        assert_eq!("", unsafe { string_array.value_unchecked(1) });
        assert_eq!("parquet", string_array.value(2));
        assert_eq!("parquet", unsafe { string_array.value_unchecked(2) });
        assert_eq!(5, string_array.value_offsets()[2]);
        assert_eq!(7, string_array.value_length(2));
        for i in 0..3 {
            assert!(string_array.is_valid(i));
            assert!(!string_array.is_null(i));
        }
    }

    #[test]
    fn test_nested_string_array() {
        let string_builder = StringBuilder::new(3);
        let mut list_of_string_builder = ListBuilder::new(string_builder);

        list_of_string_builder.values().append_value("foo").unwrap();
        list_of_string_builder.values().append_value("bar").unwrap();
        list_of_string_builder.append(true).unwrap();

        list_of_string_builder
            .values()
            .append_value("foobar")
            .unwrap();
        list_of_string_builder.append(true).unwrap();
        let list_of_strings = list_of_string_builder.finish();

        assert_eq!(list_of_strings.len(), 2);

        let first_slot = list_of_strings.value(0);
        let first_list = first_slot.as_any().downcast_ref::<StringArray>().unwrap();
        assert_eq!(first_list.len(), 2);
        assert_eq!(first_list.value(0), "foo");
        assert_eq!(unsafe { first_list.value_unchecked(0) }, "foo");
        assert_eq!(first_list.value(1), "bar");
        assert_eq!(unsafe { first_list.value_unchecked(1) }, "bar");

        let second_slot = list_of_strings.value(1);
        let second_list = second_slot.as_any().downcast_ref::<StringArray>().unwrap();
        assert_eq!(second_list.len(), 1);
        assert_eq!(second_list.value(0), "foobar");
        assert_eq!(unsafe { second_list.value_unchecked(0) }, "foobar");
    }

    #[test]
    #[should_panic(expected = "StringArray out of bounds access")]
    fn test_string_array_get_value_index_out_of_bound() {
        let values: [u8; 12] = [
            b'h', b'e', b'l', b'l', b'o', b'p', b'a', b'r', b'q', b'u', b'e', b't',
        ];
        let offsets: [i32; 4] = [0, 5, 5, 12];
        let array_data = ArrayData::builder(DataType::Utf8)
            .len(3)
            .add_buffer(Buffer::from_slice_ref(&offsets))
            .add_buffer(Buffer::from_slice_ref(&values))
            .build()
            .unwrap();
        let string_array = StringArray::from(array_data);
        string_array.value(4);
    }

    #[test]
    fn test_string_array_fmt_debug() {
        let arr: StringArray = vec!["hello", "arrow"].into();
        assert_eq!(
            "StringArray\n[\n  \"hello\",\n  \"arrow\",\n]",
            format!("{:?}", arr)
        );
    }

    #[test]
    fn test_large_string_array_fmt_debug() {
        let arr: LargeStringArray = vec!["hello", "arrow"].into();
        assert_eq!(
            "LargeStringArray\n[\n  \"hello\",\n  \"arrow\",\n]",
            format!("{:?}", arr)
        );
    }

    #[test]
    fn test_string_array_from_iter() {
        let data = [Some("hello"), None, Some("arrow")];
        let data_vec = data.to_vec();
        // from Vec<Option<&str>>
        let array1 = StringArray::from(data_vec.clone());
        // from Iterator<Option<&str>>
        let array2: StringArray = data_vec.clone().into_iter().collect();
        // from Iterator<Option<String>>
        let array3: StringArray = data_vec
            .into_iter()
            .map(|x| x.map(|s| s.to_string()))
            .collect();
        // from Iterator<&Option<&str>>
        let array4: StringArray = data.iter().collect::<StringArray>();

        assert_eq!(array1, array2);
        assert_eq!(array2, array3);
        assert_eq!(array3, array4);
    }

    #[test]
    fn test_string_array_from_iter_values() {
        let data = vec!["hello", "hello2"];
        let array1 = StringArray::from_iter_values(data.iter());

        assert_eq!(array1.value(0), "hello");
        assert_eq!(array1.value(1), "hello2");
    }

    #[test]
    fn test_string_array_from_unbound_iter() {
        // iterator that doesn't declare (upper) size bound
        let string_iter = (0..)
            .scan(0usize, |pos, i| {
                if *pos < 10 {
                    *pos += 1;
                    Some(Some(format!("value {}", i)))
                } else {
                    // actually returns up to 10 values
                    None
                }
            })
            // limited using take()
            .take(100);

        let (_, upper_size_bound) = string_iter.size_hint();
        // the upper bound, defined by take above, is 100
        assert_eq!(upper_size_bound, Some(100));
        let string_array: StringArray = string_iter.collect();
        // but the actual number of items in the array should be 10
        assert_eq!(string_array.len(), 10);
    }

    #[test]
    fn test_string_array_all_null() {
        let data = vec![None];
        let array = StringArray::from(data);
        array
            .data()
            .validate_full()
            .expect("All null array has valid array data");
    }

    #[test]
    fn test_large_string_array_all_null() {
        let data = vec![None];
        let array = LargeStringArray::from(data);
        array
            .data()
            .validate_full()
            .expect("All null array has valid array data");
    }
}