My Shortest CSV Parser

CsvBasic.fs

(*		
 * This work (My Shortest CSV Parser:CsvBasic.fs by James Tuley), 		
 * identified by James Tuley, is free of known copyright restrictions		
 * Source: https://gist.github.com/jbtule/83e330335b1afc924d508ce49b0927fc		
 * http://creativecommons.org/publicdomain/mark/1.0/ 		
 *)
module CsvBasic
open System.IO
type SB = System.Text.StringBuilder
[<Struct>] type internal Quote = None | Open | Closed
[<Struct>] type internal CsvState = { Table: string list list; Row: string list; Cell: SB; Quote: Quote }
let parseCsv (read:TextReader) =
    let empty () = { Table = []; Row = []; Cell = SB(); Quote = None }
    let finalizeCell = function | { Row = []; } as cs when cs.Cell.Length = 0 -> { empty () with Table = cs.Table }
                                | cs -> { empty () with Table = cs.Table; Row = (cs.Cell.ToString())::cs.Row }
    let finalizeRow = finalizeCell >> function | { Row = [] } as cs -> {empty () with Table = cs.Table }
                                               | cs -> { empty () with Table = (List.rev cs.Row)::cs.Table }
    let finalizeTable = finalizeRow >> fun cs -> List.rev cs.Table
    seq { while read.Peek() >= 0 do yield read.Read() |> char }
    |> Seq.fold (fun cs c -> let pos  = lazy (cs.Table.Length + 1, cs.Row.Length + 1)
                             let includeWhileQuoteIs q = { cs with Cell = cs.Cell.Append(c); Quote = q }
                             match struct (c, cs.Cell, cs.Quote) with
                             | struct ('\"', sb, None) when sb.Length = 0 -> { cs with Quote = Open }
                             | struct ('\"',  _, None) -> failwithf "Unescaped quote in cell %A" pos.Value
                             | struct ('\"',  _, Open) -> { cs with Quote = Closed }
                             | struct ('\"',  _, Closed) | struct (   _, _, Open) -> includeWhileQuoteIs Open
                             | struct ( ',',  _, Closed) | struct ( ',', _, None) -> finalizeCell cs
                             | struct ('\r',  _, Closed) | struct ('\r', _, None) -> cs
                             | struct ('\n',  _, Closed) | struct ('\n', _, None) -> finalizeRow cs
                             | struct (   _,  _, Closed) -> failwithf "Extra char '%c' outside of cell %A" c pos.Value
                             | struct (   _,  _, None)   -> includeWhileQuoteIs None) (empty ())
    |> finalizeTable
let parseCsvFile enc path =
    let stream = let s = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)
                 new StreamReader(s, encoding = enc, detectEncodingFromByteOrderMarks = false)
    using stream parseCsv 

CsvLazy.fs

(*		
 * This work (My Shortest CSV Parser:CsvLazy.fs by James Tuley), 		
 * identified by James Tuley, is free of known copyright restrictions		
 * Source: https://gist.github.com/jbtule/83e330335b1afc924d508ce49b0927fc		
 * http://creativecommons.org/publicdomain/mark/1.0/ 		
 *)
module CsvLazy
open System.IO
type SB = System.Text.StringBuilder
[<Struct>] type internal Quote = None | Open | Closed
[<Struct>] type internal CsvState = { Yield: string list; Len:int; Row: string list; Cell: SB; Quote: Quote }
let parseCsv (read:TextReader) =
    let empty len = {Yield=[]; Len=len; Row = []; Cell = SB(); Quote = None }
    let finalizeCell = function | { Row = []; } as cs when cs.Cell.Length = 0 -> empty cs.Len
                                | cs -> { empty cs.Len with Row = (cs.Cell.ToString())::cs.Row }
    let finalizeRow = finalizeCell >> function | { Row = [] } as cs -> empty cs.Len
                                               | cs -> { empty (cs.Len + 1) with Yield = (List.rev cs.Row) }
    seq { let mutable ms = empty 0
          for c in seq { while read.Peek() >= 0 do yield read.Read() |> char } do
              let pos  = lazy (ms.Len + 1, ms.Row.Length + 1)
              let includeWhileQuoteIs q = { ms with Cell = ms.Cell.Append(c); Quote = q }
              match struct (c, ms.Cell, ms.Quote) with
              | struct ('\"', sb, None) when sb.Length = 0 -> ms <- { ms with Quote = Open }
              | struct ('\"',  _, None) -> failwithf "Unescaped quote in cell %A" pos.Value
              | struct ('\"',  _, Open) -> ms <- { ms with Quote = Closed }
              | struct ('\"',  _, Closed) | struct (   _, _, Open) -> ms <- includeWhileQuoteIs Open
              | struct ( ',',  _, Closed) | struct ( ',', _, None) -> ms <- finalizeCell ms
              | struct ('\r',  _, Closed) | struct ('\r', _, None) -> ()
              | struct ('\n',  _, Closed) | struct ('\n', _, None) -> ms <- finalizeRow ms; yield ms.Yield; 
              | struct (   _,  _, Closed) -> failwithf "Extra char '%c' outside of cell %A" c pos.Value
              | struct (   _,  _, None)   -> ms <- includeWhileQuoteIs None }
let parseCsvFile enc path =
    seq { use stream = let s = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)
                       new StreamReader(s, encoding = enc, detectEncodingFromByteOrderMarks = false)
          for row in parseCsv stream do yield row }