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// 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. //! String Writer //! This string writer encapsulates `std::string::String` and //! implements `std::io::Write` trait, which makes String as a //! writable object like File. //! //! Example: //! //! ``` //! use arrow::array::*; //! use arrow::csv; //! use arrow::datatypes::*; //! use arrow::record_batch::RecordBatch; //! use arrow::util::string_writer::StringWriter; //! use std::sync::Arc; //! //! let schema = Schema::new(vec![ //! Field::new("c1", DataType::Utf8, false), //! Field::new("c2", DataType::Float64, true), //! Field::new("c3", DataType::UInt32, false), //! Field::new("c3", DataType::Boolean, true), //! ]); //! let c1 = StringArray::from(vec![ //! "Lorem ipsum dolor sit amet", //! "consectetur adipiscing elit", //! "sed do eiusmod tempor", //! ]); //! let c2 = PrimitiveArray::<Float64Type>::from(vec![ //! Some(123.564532), //! None, //! Some(-556132.25), //! ]); //! let c3 = PrimitiveArray::<UInt32Type>::from(vec![3, 2, 1]); //! let c4 = BooleanArray::from(vec![Some(true), Some(false), None]); //! //! let batch = RecordBatch::try_new( //! Arc::new(schema), //! vec![Arc::new(c1), Arc::new(c2), Arc::new(c3), Arc::new(c4)], //! ) //! .unwrap(); //! //! let sw = StringWriter::new(); //! let mut writer = csv::Writer::new(sw); //! writer.write(&batch).unwrap(); //! ``` use std::io::{Error, ErrorKind, Result, Write}; #[derive(Debug)] pub struct StringWriter { data: String, } impl StringWriter { pub fn new() -> Self { StringWriter { data: String::new(), } } } impl Default for StringWriter { fn default() -> Self { Self::new() } } impl ToString for StringWriter { fn to_string(&self) -> String { self.data.clone() } } impl Write for StringWriter { fn write(&mut self, buf: &[u8]) -> Result<usize> { let string = match String::from_utf8(buf.to_vec()) { Ok(x) => x, Err(e) => { return Err(Error::new(ErrorKind::InvalidData, e)); } }; self.data.push_str(&string); Ok(string.len()) } fn flush(&mut self) -> Result<()> { Ok(()) } }