git clone ''

(ql:quickload :read-csv)


1 Overview

read-csv is a stream oriented CSV (comma-separated value) reader that supports excel .csv files.

(with-open-file (s "/path/to/csv")
  (parse-csv s))

;; Returns a list of lists of strings.

1.1 Features

2 Installation

2.1 Quick Lisp

Install Quick Lisp and then run:

(ql:quickload 'read-csv)

If you have problems, see the support section, and you may want to run the tests.

2.2 Gentoo

As root,

emerge read-csv

Once the emerge is finished, the package can be loaded using ASDF:

(asdf:operate 'asdf:load-op :read-csv)

If you have problems, see the support section, otherwise you may want to run the tests.

2.3 Ubunto

sudo apt-get install read-csv

Once the installation is finished, the package is loadable using ASDF:

(asdf:operate 'asdf:load-op :read-csv)

If you have problems, see the support section, otherwise you may want to run the tests.

2.4 Manual Installation

In summary: Untar the .tar package and then symlink the .asd files into a place where ASDF can find them.

  1. Untar the files where you want them to be. On windows download the .zip and unzip it instead, it's the same files.
  2. ASDF could be looking anywhere – it depends on your setup. Run this in your lisp repl to get a clue as to where ASDF is seeking libraries[1]:

(mapcan #'funcall asdf:default-source-registries)

  1. Symlink the .asd files to the source directory. If you use windows, these instructions on symlink alternatives apply to you.

Once the files are in place, the package can be loaded with ASDF by:

(asdf:operate 'asdf:load-op :read-csv)

If you have problems, see the support section. If you don't have problems you may want to run the tests anyway, because you can.

2.5 Running the Tests

Once the system is loaded, it can be tested with asdf.

(asdf:operate 'asdf:test-op :read-csv)

This should display something like the following. There should be zero failures, if you have failures see the support section of this document.

RUNNING READ-CSV TESTS… READ-CSV TEST RESULTS: Tests: 519 Success: 519 Failures: 0

[support]: #support

2.6 Getting Support

You can find support on this libraries website and/or github repository. Or you can email Warren Wilkinson.

3 Implementation

Most Lisp CSV readers hover around 400 lines of code. This one is 68.

The difference is this one is coded as state machine in a dense 2D grid, as described in FINITE State Machines in Forth. “If you are in this /state/ and you see this /character/ then you …”

state white return linefeed quote separator other
———–+—————-+—————+————–+—————-+————–+—————- start noop →start ship →return ship →done! noop →quote next →start addc →unquote
return noop →start ship →return noop →done! noop →start next →start addc →unquote
unquote addc →unquote ship →return ship →done! addc →unquote next →start addc →unquote
quote addc →quote noop →q+ret addl →quote noop →q+quote addc →quote addc →quote
q+ret addc →quote noop →q+ret addl →quote noop →q+quote addc →quote addc →quote
q+quote noop →q+q&w ship →return ship →done! addc →quote next →start addc →unquote
q+q&w noop →q+q&w ship →return ship →done! addc →quote next →start addc →unquote

1) perform the designated function, and 2) transition to the designated new state.

For example, if we start /(e.g. state start)/ and spot quote, then we perform noop and change to quote state. Then, in the quote state, if we spot ‘/A/’, perform ‘addc’ (add character) and remain in the quote state.

3.1 Collecting the Input

The functions used by the above table are:

noop: Do no action addc: Add a character to the current CSV record. addl: Add a newline character to the current CSV record. next: Finish the current CSV record and start the next. ship: Cleanup the current set of CSV records for returning them to the end user.

Internally, these methods play with three dynamic variables: *record* and *records* and *white-char-count*. The first, during run time, holds a list of characters – in reverse order. The second holds the list of parsed records – also in reverse order (but each record in proper order). The next method reverses the order and coerces the csv data to a string. The ship method reverses the *records* list so it's in proper order.

The last variable, *white-char-count* keeps a count of how many characters we've seen since after the quote. It's used to let us to remove whitespace characters after the closing quote without removing whitespace characters within the quotes.

(defun noop (c) (declare (ignore c))) (defun addc (c) (push c record)) (defun addl (c) (declare (ignore c)) (push #\Newline record)) (flet ((white (c) (or (char= c #\Space) (char= c #\Tab)))) (defun next (c) (declare (ignore c)) (let ((eow (or (position-if-not #'white record) (length record)))) (push (coerce (nreverse (nthcdr (max 0 (min eow (1- white-char-count))) record)) 'string) records)) (setf record nil))) (defun ship (c) (next c) (setf records (nreverse records)))

3.2 Traversing the Input

We read CSV by running our state machine until the /done/ state is reached.

(defun char-class (sep char) (case char (#\Space 0) (#\Return 1) (#\Linefeed 2) (#" 3) (otherwise (if (char= sep char) 4 5))))

(defun read-csv (stream &optional (sep #\,) (eof-error-p t) eof-value) “Return CSV data and a second value that's true if row ended by EOF.” (let ((records nil) (record nil) (white-char-count 0)) (declare (special record records white-char-count)) (loop with state = start for char = (read-char stream (and (null records) eof-error-p) :eof) when (eq char :eof) do (return-from read-csv (values (if records (ship :eof) eof-value) t)) do (incf white-char-count) do (let ((class (char-class sep char))) (when (= class quote) (setf white-char-count 0)) (funcall (aref +csv-table+ state class 0) char) (setf state (aref +csv-table+ state class 1))) until (eq state done!)) (values records (eq :eof (peek-char nil stream nil :eof)))))

3.3 Parsing whole files: parse-csv

To parse a whole file, the utility parse-csv calls read-csv until the end-of-file.

(defun parse-csv (stream &optional (sep #\,)) (loop for (line end-p) = (multiple-value-list (read-csv stream sep nil :eof)) unless (eq line :eof) collect line until end-p))

3.4 Test Framework

The test framework combines jumbles of CSV statements and calls read-csv on them. In practice it means I take (upto) 5 patterns, sequentially, from the a predefined list of hard patterns. Then I take all permutations (120, if 5 patterns) and combine them as 1 record per row (and 5 rows), 2 per row, 3 per row, 4 per row and 5 per row. Then I test that I can parse it back correctly.

The jumbler is shown below, but I also test parse-csv by parsing larger examples but that is not shown here.

(defun concat-with (strings item) (if (null strings) "" (apply #'concatenate ‘string (first strings) (mapcan #’(lambda (a) (list item a)) (rest strings)))))

(defun build-answers (i strings) (loop while strings collect (loop for n upto (1- i) while strings collect (car strings) do (setf strings (cdr strings)))))

(defun build-string (i strings) (concatenate ‘string (concat-with (mapcar #’(lambda (s) (concat-with s “,”)) (build-answers i strings)) (list #\Newline)) '(#\Newline)))

(defun all-combinations (patterns) (if (null (cdr patterns)) (list patterns) (loop for i in patterns nconc (mapcar #'(lambda (p) (cons i p)) (all-combinations (remove i patterns))))))

(defun make-test (description) #'(lambda () (block test ;(loop for pattern in (all-combinations description) (format t “~%Pattern: ~s” (substitute #' #" (remove #\Newline (build-string (length description) (mapcar #'car description))))) (dotimes (i (length description) t) (format t “~% @~d” i) (let ((string (build-string (1+ i) (mapcar #'car description))) (answers (build-answers (1+ i) (mapcar #'cdr description)))) (with-input-from-string (s string) (loop for answer in answers for (got end) = (multiple-value-list (read-csv s)) unless (equalp answer got) do (format t “~%Expected ~a, got ~a” answer got) and do (return-from test nil) if (eq answer (car (last answers))) unless end do (format t “~%Expected EOF, but didn't see it!”) unless (not end) do (format t “~%Did not expect EOF, but saw it!”)) (let ((read-more (read-csv s #\, nil :eof))) (unless (eq read-more :eof) (format t “~%Could read past end: ~s” read-more) (return-from test nil)))))))))

3.4.1 Parse-csv tests ~~~~~~~~~~~~~~~~~~~~~~

These tests were yanked from CL-CSV, another Lisp CSV parser.

(defmacro deftest (name code result) `(defun ,name () (format t “~%~a” ',name) (let ((expect ,result) (got ,code)) (if (equalp expect got) t (progn (format t “~%Expected~% ~s~%but got~%~s” expect got) nil)))))

(defvar a-tough-example-answer '((“very tough” “easier to do”))) (defun a-tough-example () (with-input-from-string (s “ "very tough" , easier to do
”) (parse-csv s)))

(deftest test-tough (a-tough-example) a-tough-example-answer)

(defvar big-example-answer '((“first name” “last name” “job "title"” “number of hours” “id”) (“Russ” “Tyndall” “Software Developer's, "Position"” “26.2” “1”) (“Adam” “Smith” “Economist” “37.5” “2”) (“John” “Doe” “Anonymous Human” “42.1” “3”) (“Chuck” “Darwin” “Natural Philosopher” “17.68” “4”) (“Bill” “Shakespeare” “Bard” “12.2” “5”) (“James” “Kirk” “Starship Captain” “13.1” “6”) (“Bob” “Anon” "“ ”13.1“ ”6“) (”Mr“ ”Iñtërnâtiônàlizætiøn“ ”“ ”1.1“ ”0")))

(defun big-example () (with-input-from-string (s “first name,last name,"job ""title""",number of hours,id Russ,Tyndall,"Software Developer's, ""Position""",26.2,1 Adam,Smith,Economist,37.5,2 John,Doe,Anonymous Human,42.1,3 Chuck,Darwin,Natural Philosopher,17.68,4 Bill,Shakespeare,Bard,12.2,5 James,Kirk,Starship Captain,13.1,6 Bob,Anon,,13.1,6 Mr,Iñtërnâtiônàlizætiøn,,1.1,0”) (parse-csv s)))

(defun quoted-big-example () (with-input-from-string (s “"first name","last name","job ""title""","number of hours","id" "Russ","Tyndall","Software Developer's, ""Position""","26.2","1" "Adam","Smith","Economist","37.5","2" "John","Doe","Anonymous Human","42.1","3" "Chuck","Darwin","Natural Philosopher","17.68","4" "Bill","Shakespeare","Bard","12.2","5" "James","Kirk","Starship Captain","13.1","6" "Bob","Anon","","13.1","6" "Mr","Iñtërnâtiônàlizætiøn","","1.1","0"”) (parse-csv s)))

(deftest test-big (big-example) big-example-answer) (deftest test-quoted-big (quoted-big-example) big-example-answer)

(defvar multiline-answer '((“this” “is” “a” “test of multiline” “data”) (“row2” “of” “the” “test of multiline” “data”)))

(defun multiline-unix-example () (with-input-from-string (s “this,is,a,"test of multiline", data row2,of,the,"test of multiline", data”) (parse-csv s)))

(defun multiline-dos-example () (with-input-from-string (s (concatenate 'string “this,is,a,"test” (list #\Return #\Linefeed) “of” (list #\Return #\Linefeed) “multiline", data” (list #\Return #\Linefeed) “row2,of,the,"test” (list #\Return #\Linefeed) “of” (list #\Return #\Linefeed) “multiline", data” (list #\Return #\Linefeed))) (parse-csv s)))

(defun multiline-mixed-example () (with-input-from-string (s (concatenate 'string “this,is,a,"test” (list #\Linefeed) “of” (list #\Return #\Linefeed) “multiline", data” (list #\Return #\Linefeed) “row2,of,the,"test” (list #\Linefeed) “of” (list #\Return #\Linefeed) “multiline", data” (list #\Linefeed))) (parse-csv s)))

(deftest test-multiline-unix (multiline-unix-example) multiline-answer) (deftest test-multiline-dos (multiline-dos-example) multiline-answer) (deftest test-multiline-mixed (multiline-mixed-example) multiline-answer)

3.4.2 Running Tests ~~~~~~~~~~~~~~~~~~~~

(defstruct results (tests 0) (failures nil)) (defun results-failure-count (results) (length (results-failures results))) (defun results-successes (results) (- (results-tests results) (results-failure-count results)))

(defun runtest (fun results) (let* ((success t) (output (with-output-to-string (standard-output) (setf success (handler-case (funcall fun) (error (e) (princ e) nil)))))) (make-results :tests (1+ (results-tests results)) :failures (if success (results-failures results) (acons fun output (results-failures results))))))

(defun present-failures (results) (format t “~%READ-CSV FAILURES:~%”) (loop for (fn . problems) in (results-failures results) do (format t “~%~a~a~%” fn problems))) (defun present-results (results) (format t “~%READ-CSV TEST RESULTS:”) (format t “~% Tests: ~a~% Success: ~a~% Failures: ~a” (results-tests results) (results-successes results) (results-failure-count results)) (when (results-failures results) (present-failures results)))

(defun run-combination-tests (starting-results) (reduce #‘(lambda (description results) (runtest (make-test description) results)) (nreverse (mapcan #’(lambda (thing) (all-combinations (subseq thing 0 (min (length thing) 5)))) (loop for i on (reverse all-statements) collecting i))) :from-end t :initial-value starting-results))

(defun run-explicit-tests (starting-results) (reduce #'(lambda (results function) (runtest function results)) (list #'test-tough #'test-big #'test-quoted-big #'test-multiline-unix #'test-multiline-dos #'test-multiline-mixed) :initial-value starting-results))

(defun run-tests () (format t “~%RUNNING READ-CSV TESTS…”) (present-results (run-explicit-tests (run-combination-tests (make-results)))))

The bulk of the test code just has to do with collecting results and making pretty output.

4 Tests Expressions

This package is tested by combining tricky CSV parts in numerous ways, and then ensuring the parser can parse them correctly.

4.1 Blanks

CSV Should Parse Note
———-+—————-+——————————————————– >< >< blank input > \t < >< whitespace input, should be ignored.
>"“< >< blank input, but quoted, should be empty
>” \t "< > \t < blank input, but quoted, should keep the whitespace.

4.2 Quotes and Tricky Characters

CSV Should Parse Note
—————–+—————-+——————————————— >“multi\nline”< >multi\nline< Multiline input should work >“,”< >,< Should be able to have seperator characters >"""“< >”< Double quotes should become a single quote.

4.3 International Text

CSV Should Parse Note
—————————–+————————–+——————– >“êve,y\nth还ng\tat”“once”< >êve,y\nth还ng\tat"once< Everything at once

5 License

Read-csv is distributed under the LGPL2 License.

[1] you might need to (require 'asdf) before running this example