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#
#
# The Nim Compiler
# (c) Copyright 2021 Nim Contributors
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## This module provides some high performance string operations.
##
## Experimental API, subject to change.
const whitespaces = {' ', '\t', '\v', '\r', '\l', '\f'}
proc add*(x: var string, y: openArray[char]) =
## Concatenates `x` and `y` in place. `y` must not overlap with `x` to
## allow future `memcpy` optimizations.
# Use `{.noalias.}` ?
let n = x.len
x.setLen n + y.len
# pending https://github.com/nim-lang/Nim/issues/14655#issuecomment-643671397
# use x.setLen(n + y.len, isInit = false)
var i = 0
while i < y.len:
x[n + i] = y[i]
i.inc
# xxx use `nimCopyMem(x[n].addr, y[0].addr, y.len)` after some refactoring
func stripSlice(s: openArray[char], leading = true, trailing = true, chars: set[char] = whitespaces): Slice[int] =
## Returns the slice range of `s` which is stripped `chars`.
runnableExamples:
assert stripSlice(" abc ") == 1 .. 3
var
first = 0
last = high(s)
if leading:
while first <= last and s[first] in chars: inc(first)
if trailing:
while last >= first and s[last] in chars: dec(last)
result = first .. last
func setSlice*(s: var string, slice: Slice[int]) =
## Inplace version of `substr`.
runnableExamples:
import std/sugar
var a = "Hello, Nim!"
doassert a.dup(setSlice(7 .. 9)) == "Nim"
doAssert a.dup(setSlice(0 .. 0)) == "H"
doAssert a.dup(setSlice(0 .. 1)) == "He"
doAssert a.dup(setSlice(0 .. 10)) == a
doAssert a.dup(setSlice(1 .. 0)).len == 0
doAssert a.dup(setSlice(20 .. -1)).len == 0
doAssertRaises(AssertionDefect):
discard a.dup(setSlice(-1 .. 1))
doAssertRaises(AssertionDefect):
discard a.dup(setSlice(1 .. 11))
let first = slice.a
let last = slice.b
assert first >= 0
assert last <= s.high
if first > last:
s.setLen(0)
return
template impl =
for index in first .. last:
s[index - first] = s[index]
if first > 0:
when nimvm: impl()
else:
# not JS and not Nimscript
when not declared(moveMem):
impl()
else:
when defined(nimSeqsV2):
prepareMutation(s)
moveMem(addr s[0], addr s[first], last - first + 1)
s.setLen(last - first + 1)
func strip*(a: var string, leading = true, trailing = true, chars: set[char] = whitespaces) {.inline.} =
## Inplace version of `strip`. Strips leading or
## trailing `chars` (default: whitespace characters).
##
## If `leading` is true (default), leading `chars` are stripped.
## If `trailing` is true (default), trailing `chars` are stripped.
## If both are false, the string is unchanged.
runnableExamples:
var a = " vhellov "
strip(a)
assert a == "vhellov"
a = " vhellov "
a.strip(leading = false)
assert a == " vhellov"
a = " vhellov "
a.strip(trailing = false)
assert a == "vhellov "
var c = "blaXbla"
c.strip(chars = {'b', 'a'})
assert c == "laXbl"
c = "blaXbla"
c.strip(chars = {'b', 'a', 'l'})
assert c == "X"
setSlice(a, stripSlice(a, leading, trailing, chars))
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