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improve fast returns of find and rfind (#18127)

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n5m 2021-05-31 09:20:15 +00:00 • committed by GitHub
commit 064fe18de6
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2 changed files with 31 additions and 1 deletions
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4
lib/pure/strutils.nim
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@ -1890,7 +1890,7 @@ func find*(s, sub: string, start: Natural = 0, last = 0): int {.rtl,
## See also: ## See also:
## * `rfind func<#rfind,string,string,Natural>`_ ## * `rfind func<#rfind,string,string,Natural>`_
## * `replace func<#replace,string,string,string>`_ ## * `replace func<#replace,string,string,string>`_
if sub.len > s.len: return -1 if sub.len > s.len - start: return -1
if sub.len == 1: return find(s, sub[0], start, last) if sub.len == 1: return find(s, sub[0], start, last)
template useSkipTable {.dirty.} = template useSkipTable {.dirty.} =
@ -1967,6 +1967,8 @@ func rfind*(s, sub: string, start: Natural = 0, last = -1): int {.rtl,
## * `find func<#find,string,string,Natural,int>`_ ## * `find func<#find,string,string,Natural,int>`_
if sub.len == 0: if sub.len == 0:
return -1 return -1
if sub.len > s.len - start:
return -1
let last = if last == -1: s.high else: last let last = if last == -1: s.high else: last
result = 0 result = 0
for i in countdown(last - sub.len + 1, start): for i in countdown(last - sub.len + 1, start):

28
tests/stdlib/tstrutils.nim
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@ -243,6 +243,34 @@ template main() =
doAssert "/1/2/3".rfind('/', last=1) == 0 doAssert "/1/2/3".rfind('/', last=1) == 0
doAssert "/1/2/3".rfind('0') == -1 doAssert "/1/2/3".rfind('0') == -1
block:
const haystack: string = "ABCABABABABCAB"
doAssert haystack.len == 14
doAssert haystack.rfind("ABC") == 9
doAssert haystack.rfind("ABC", last=13) == 9
doAssert haystack.rfind("ABC", last=12) == 9
doAssert haystack.rfind("ABC", last=11) == 9
doAssert haystack.rfind("ABC", last=10) == 0
doAssert haystack.rfind("ABC", start=0) == 9
doAssert haystack.rfind("ABC", start=1) == 9
doAssert haystack.rfind("ABC", start=2) == 9
doAssert haystack.rfind("ABC", start=9) == 9
doAssert haystack.rfind("ABC", start=10) == -1
doAssert haystack.rfind("ABC", start=11) == -1
doAssert haystack.rfind("ABC", start=12) == -1
doAssert haystack.rfind("ABC", start=0, last=13) == 9
doAssert haystack.rfind("ABC", start=0, last=12) == 9
doAssert haystack.rfind("ABC", start=0, last=11) == 9
doAssert haystack.rfind("ABC", start=0, last=10) == 0
doAssert haystack.rfind("ABC", start=1, last=10) == -1
doAssert "".rfind("/") == -1
doAssert "/".rfind("/") == 0
doAssert "/".rfind("//") == -1
doAssert "///".rfind("//", start=3) == -1
block: # trimZeros block: # trimZeros
var x = "1200" var x = "1200"
x.trimZeros() x.trimZeros()