Permalink
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
266 lines (244 sloc) 7.86 KB
#
#
# Nim's Runtime Library
# (c) Copyright 2009 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## This module implements a simple high performance `CSV`:idx:
## (`comma separated value`:idx:) parser.
##
## Example: How to use the parser
## ==============================
##
## .. code-block:: nim
## import os, parsecsv, streams
## var s = newFileStream(paramStr(1), fmRead)
## if s == nil: quit("cannot open the file" & paramStr(1))
## var x: CsvParser
## open(x, s, paramStr(1))
## while readRow(x):
## echo "new row: "
## for val in items(x.row):
## echo "##", val, "##"
## close(x)
##
## For CSV files with a header row, the header can be read and then used as a
## reference for item access with `rowEntry <#rowEntry.CsvParser.string>`_:
##
## .. code-block:: nim
## import parsecsv
## import os
## # Prepare a file
## let content = """One,Two,Three,Four
## 1,2,3,4
## 10,20,30,40
## 100,200,300,400
## """
## writeFile("temp.csv", content)
##
## var p: CsvParser
## p.open("temp.csv")
## p.readHeaderRow()
## while p.readRow():
## echo "new row: "
## for col in items(p.headers):
## echo "##", col, ":", p.rowEntry(col), "##"
## p.close()
import
lexbase, streams
type
CsvRow* = seq[string] ## a row in a CSV file
CsvParser* = object of BaseLexer ## the parser object.
row*: CsvRow ## the current row
filename: string
sep, quote, esc: char
skipWhite: bool
currRow: int
headers*: seq[string] ## The columns that are defined in the csv file
## (read using `readHeaderRow <#readHeaderRow.CsvParser>`_).
## Used with `rowEntry <#rowEntry.CsvParser.string>`_).
CsvError* = object of IOError ## exception that is raised if
## a parsing error occurs
proc raiseEInvalidCsv(filename: string, line, col: int,
msg: string) {.noreturn.} =
var e: ref CsvError
new(e)
if filename.len == 0:
e.msg = "Error: " & msg
else:
e.msg = filename & "(" & $line & ", " & $col & ") Error: " & msg
raise e
proc error(my: CsvParser, pos: int, msg: string) =
raiseEInvalidCsv(my.filename, my.lineNumber, getColNumber(my, pos), msg)
proc open*(my: var CsvParser, input: Stream, filename: string,
separator = ',', quote = '"', escape = '\0',
skipInitialSpace = false) =
## initializes the parser with an input stream. `Filename` is only used
## for nice error messages. The parser's behaviour can be controlled by
## the diverse optional parameters:
## - `separator`: character used to separate fields
## - `quote`: Used to quote fields containing special characters like
## `separator`, `quote` or new-line characters. '\0' disables the parsing
## of quotes.
## - `escape`: removes any special meaning from the following character;
## '\0' disables escaping; if escaping is disabled and `quote` is not '\0',
## two `quote` characters are parsed one literal `quote` character.
## - `skipInitialSpace`: If true, whitespace immediately following the
## `separator` is ignored.
lexbase.open(my, input)
my.filename = filename
my.sep = separator
my.quote = quote
my.esc = escape
my.skipWhite = skipInitialSpace
my.row = @[]
my.currRow = 0
proc open*(my: var CsvParser, filename: string,
separator = ',', quote = '"', escape = '\0',
skipInitialSpace = false) =
## same as the other `open` but creates the file stream for you.
var s = newFileStream(filename, fmRead)
if s == nil: my.error(0, "cannot open: " & filename)
open(my, s, filename, separator,
quote, escape, skipInitialSpace)
proc parseField(my: var CsvParser, a: var string) =
var pos = my.bufpos
var buf = my.buf
if my.skipWhite:
while buf[pos] in {' ', '\t'}: inc(pos)
setLen(a, 0) # reuse memory
if buf[pos] == my.quote and my.quote != '\0':
inc(pos)
while true:
let c = buf[pos]
if c == '\0':
my.bufpos = pos # can continue after exception?
error(my, pos, my.quote & " expected")
break
elif c == my.quote:
if my.esc == '\0' and buf[pos+1] == my.quote:
add(a, my.quote)
inc(pos, 2)
else:
inc(pos)
break
elif c == my.esc:
add(a, buf[pos+1])
inc(pos, 2)
else:
case c
of '\c':
pos = handleCR(my, pos)
buf = my.buf
add(a, "\n")
of '\l':
pos = handleLF(my, pos)
buf = my.buf
add(a, "\n")
else:
add(a, c)
inc(pos)
else:
while true:
let c = buf[pos]
if c == my.sep: break
if c in {'\c', '\l', '\0'}: break
add(a, c)
inc(pos)
my.bufpos = pos
proc processedRows*(my: var CsvParser): int =
## returns number of the processed rows
return my.currRow
proc readRow*(my: var CsvParser, columns = 0): bool =
## reads the next row; if `columns` > 0, it expects the row to have
## exactly this many columns. Returns false if the end of the file
## has been encountered else true.
##
## Blank lines are skipped.
var col = 0 # current column
let oldpos = my.bufpos
while my.buf[my.bufpos] != '\0':
let oldlen = my.row.len
if oldlen < col+1:
setLen(my.row, col+1)
my.row[col] = ""
parseField(my, my.row[col])
inc(col)
if my.buf[my.bufpos] == my.sep:
inc(my.bufpos)
else:
case my.buf[my.bufpos]
of '\c', '\l':
# skip empty lines:
while true:
case my.buf[my.bufpos]
of '\c': my.bufpos = handleCR(my, my.bufpos)
of '\l': my.bufpos = handleLF(my, my.bufpos)
else: break
of '\0': discard
else: error(my, my.bufpos, my.sep & " expected")
break
setLen(my.row, col)
result = col > 0
if result and col != columns and columns > 0:
error(my, oldpos+1, $columns & " columns expected, but found " &
$col & " columns")
inc(my.currRow)
proc close*(my: var CsvParser) {.inline.} =
## closes the parser `my` and its associated input stream.
lexbase.close(my)
proc readHeaderRow*(my: var CsvParser) =
## Reads the first row and creates a look-up table for column numbers
## See also `rowEntry <#rowEntry.CsvParser.string>`_.
let present = my.readRow()
if present:
my.headers = my.row
proc rowEntry*(my: var CsvParser, entry: string): var string =
## Acceses a specified `entry` from the current row.
##
## Assumes that `readHeaderRow <#readHeaderRow.CsvParser>`_ has already been
## called.
let index = my.headers.find(entry)
if index >= 0:
result = my.row[index]
when not defined(testing) and isMainModule:
import os
var s = newFileStream(paramStr(1), fmRead)
if s == nil: quit("cannot open the file" & paramStr(1))
var x: CsvParser
open(x, s, paramStr(1))
while readRow(x):
echo "new row: "
for val in items(x.row):
echo "##", val, "##"
close(x)
when isMainModule:
import os
import strutils
block: # Tests for reading the header row
let content = "One,Two,Three,Four\n1,2,3,4\n10,20,30,40,\n100,200,300,400\n"
writeFile("temp.csv", content)
var p: CsvParser
p.open("temp.csv")
p.readHeaderRow()
while p.readRow():
let zeros = repeat('0', p.currRow-2)
doAssert p.rowEntry("One") == "1" & zeros
doAssert p.rowEntry("Two") == "2" & zeros
doAssert p.rowEntry("Three") == "3" & zeros
doAssert p.rowEntry("Four") == "4" & zeros
p.close()
when not defined(testing):
var parser: CsvParser
parser.open("temp.csv")
parser.readHeaderRow()
while parser.readRow():
echo "new row: "
for col in items(parser.headers):
echo "##", col, ":", parser.rowEntry(col), "##"
parser.close()
removeFile("temp.csv")
# Tidy up
removeFile("temp.csv")