76 lines
2.0 KiB
Swift
76 lines
2.0 KiB
Swift
// (c) 2019 and onwards Robert Muckle-Jones (Apache 2.0 License).
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import Foundation
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import SwiftExtension
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public class LineReader {
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let encoding: String.Encoding
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let chunkSize: Int
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var fileHandle: FileHandle
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let delimData: Data
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var buffer: Data
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var atEof: Bool
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public init(
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file: FileHandle, encoding: String.Encoding = .utf8,
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chunkSize: Int = 4096
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) throws {
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let fileHandle = file
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self.encoding = encoding
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self.chunkSize = chunkSize
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self.fileHandle = fileHandle
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delimData = "\n".data(using: encoding)!
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buffer = Data(capacity: chunkSize)
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atEof = false
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}
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/// Return next line, or nil on EOF.
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public func nextLine() -> String? {
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// Read data chunks from file until a line delimiter is found:
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while !atEof {
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// get a data from the buffer up to the next delimiter
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if let range = buffer.range(of: delimData) {
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// convert data to a string
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let line = String(data: buffer.subdata(in: 0 ..< range.lowerBound), encoding: encoding)!
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// remove that data from the buffer
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buffer.removeSubrange(0 ..< range.upperBound)
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return line.trimmingCharacters(in: .newlines)
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}
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fileRead: do {
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let nextData = try fileHandle.read(upToCount: chunkSize)
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if let nextData = nextData, !nextData.isEmpty {
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buffer.append(nextData)
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continue
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}
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} catch {
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break fileRead
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}
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// End of file or read error
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atEof = true
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if !buffer.isEmpty {
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// Buffer contains last line in file (not terminated by delimiter).
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let line = String(data: buffer as Data, encoding: encoding)!
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return line.trimmingCharacters(in: .newlines)
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}
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}
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return nil
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}
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/// Start reading from the beginning of file.
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public func rewind() {
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fileHandle.seek(toFileOffset: 0)
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buffer.count = 0
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atEof = false
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}
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}
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extension LineReader: Sequence {
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public func makeIterator() -> AnyIterator<String> {
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AnyIterator {
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self.nextLine()
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}
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}
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}
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