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use std::io::BufRead;
use fallible_streaming_iterator::FallibleStreamingIterator;
use indexmap::set::IndexSet as HashSet;
use json_deserializer::parse;
use crate::{
datatypes::DataType,
error::{Error, Result},
};
use super::super::super::json::read::{coerce_data_type, infer as infer_json};
fn read_rows<R: BufRead>(reader: &mut R, rows: &mut [String], limit: usize) -> Result<usize> {
if limit == 0 {
return Ok(0);
}
let mut row_number = 0;
for row in rows.iter_mut() {
loop {
row.clear();
let _ = reader
.read_line(row)
.map_err(|e| Error::External(format!(" at line {}", row_number), Box::new(e)))?;
if row.is_empty() {
break;
}
if !row.trim().is_empty() {
break;
}
}
if row.is_empty() {
break;
}
row_number += 1;
if row_number == limit {
break;
}
}
Ok(row_number)
}
pub struct FileReader<R: BufRead> {
reader: R,
rows: Vec<String>,
number_of_rows: usize,
remaining: usize,
}
impl<R: BufRead> FileReader<R> {
pub fn new(reader: R, rows: Vec<String>, limit: Option<usize>) -> Self {
Self {
reader,
rows,
remaining: limit.unwrap_or(usize::MAX),
number_of_rows: 0,
}
}
pub fn into_inner(self) -> (R, Vec<String>) {
(self.reader, self.rows)
}
}
impl<R: BufRead> FallibleStreamingIterator for FileReader<R> {
type Error = Error;
type Item = [String];
fn advance(&mut self) -> Result<()> {
self.number_of_rows = read_rows(&mut self.reader, &mut self.rows, self.remaining)?;
self.remaining -= self.number_of_rows;
Ok(())
}
fn get(&self) -> Option<&Self::Item> {
if self.number_of_rows > 0 {
Some(&self.rows[..self.number_of_rows])
} else {
None
}
}
}
pub fn infer<R: std::io::BufRead>(
reader: &mut R,
number_of_rows: Option<usize>,
) -> Result<DataType> {
if reader.fill_buf().map(|b| b.is_empty())? {
return Err(Error::ExternalFormat(
"Cannot infer NDJSON types on empty reader because empty string is not a valid JSON value".to_string(),
));
}
let rows = vec!["".to_string(); 1]; let mut reader = FileReader::new(reader, rows, number_of_rows);
let mut data_types = HashSet::new();
while let Some(rows) = reader.next()? {
let value = parse(rows[0].as_bytes())?; let data_type = infer_json(&value)?;
if data_type != DataType::Null {
data_types.insert(data_type);
}
}
let v: Vec<&DataType> = data_types.iter().collect();
Ok(coerce_data_type(&v))
}
pub fn infer_iter<A: AsRef<str>>(rows: impl Iterator<Item = A>) -> Result<DataType> {
let mut data_types = HashSet::new();
for row in rows {
let v = parse(row.as_ref().as_bytes())?;
let data_type = infer_json(&v)?;
if data_type != DataType::Null {
data_types.insert(data_type);
}
}
let v: Vec<&DataType> = data_types.iter().collect();
Ok(coerce_data_type(&v))
}