106 lines
3.0 KiB
Rust
106 lines
3.0 KiB
Rust
// Licensed to the Apache Software Foundation (ASF) under one
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// or more contributor license agreements. See the NOTICE file
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// distributed with this work for additional information
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// regarding copyright ownership. The ASF licenses this file
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// to you under the Apache License, Version 2.0 (the
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// "License"); you may not use this file except in compliance
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// with the License. You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing,
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// software distributed under the License is distributed on an
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// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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// KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations
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// under the License.
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//! String Writer
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//! This string writer encapsulates `std::string::String` and
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//! implements `std::io::Write` trait, which makes String as a
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//! writable object like File.
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//!
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//! Example:
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//!
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//! ```
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//! #[cfg(feature = "csv")]
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//! {
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//! use arrow::array::*;
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//! use arrow::csv;
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//! use arrow::datatypes::*;
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//! use arrow::record_batch::RecordBatch;
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//! use arrow::util::string_writer::StringWriter;
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//! use std::sync::Arc;
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//!
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//! let schema = Schema::new(vec![
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//! Field::new("c1", DataType::Utf8, false),
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//! Field::new("c2", DataType::Float64, true),
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//! Field::new("c3", DataType::UInt32, false),
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//! Field::new("c3", DataType::Boolean, true),
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//! ]);
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//! let c1 = StringArray::from(vec![
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//! "Lorem ipsum dolor sit amet",
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//! "consectetur adipiscing elit",
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//! "sed do eiusmod tempor",
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//! ]);
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//! let c2 = PrimitiveArray::<Float64Type>::from(vec![
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//! Some(123.564532),
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//! None,
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//! Some(-556132.25),
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//! ]);
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//! let c3 = PrimitiveArray::<UInt32Type>::from(vec![3, 2, 1]);
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//! let c4 = BooleanArray::from(vec![Some(true), Some(false), None]);
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//!
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//! let batch = RecordBatch::try_new(
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//! Arc::new(schema),
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//! vec![Arc::new(c1), Arc::new(c2), Arc::new(c3), Arc::new(c4)],
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//! )
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//! .unwrap();
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//!
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//! let sw = StringWriter::new();
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//! let mut writer = csv::Writer::new(sw);
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//! writer.write(&batch).unwrap();
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//! }
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//! ```
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use core::str;
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use std::fmt::Formatter;
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use std::io::{Error, ErrorKind, Result, Write};
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/// A writer that allows writing to a `String`
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/// like an `std::io::Write` object.
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#[derive(Debug, Default)]
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pub struct StringWriter {
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data: String,
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}
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impl StringWriter {
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/// Create a new `StringWriter`
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pub fn new() -> Self {
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Self::default()
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}
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}
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impl std::fmt::Display for StringWriter {
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fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
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write!(f, "{}", self.data)
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}
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}
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impl Write for StringWriter {
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fn write(&mut self, buf: &[u8]) -> Result<usize> {
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let string = match str::from_utf8(buf) {
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Ok(x) => x,
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Err(e) => {
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return Err(Error::new(ErrorKind::InvalidData, e));
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}
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};
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self.data.push_str(string);
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Ok(string.len())
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}
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fn flush(&mut self) -> Result<()> {
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Ok(())
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}
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}
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