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Fix find routines' api to default to last=-1 (#19761)
This changes the default for the `last` parameter of various `find` routines from `0` to `-1`. Previous default prevents limiting the search to the first character. This is a logic error, as full text search was performed for 2 *valid* values of `last`: `0` and `last.high()`. Adds an overload for `initSkipTable` which returns a newly initialized table. This encapsulates every single usage of a `var`-acting original func in this module. Co-authored-by: flywind <xzsflywind@gmail.com>
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@@ -1815,6 +1815,7 @@ func initSkipTable*(a: var SkipTable, sub: string) {.rtl,
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## Initializes table `a` for efficient search of substring `sub`.
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##
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## See also:
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## * `initSkipTable func<#initSkipTable,string>`_
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## * `find func<#find,SkipTable,string,string,Natural,int>`_
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# TODO: this should be the `default()` initializer for the type.
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let m = len(sub)
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@@ -1823,7 +1824,16 @@ func initSkipTable*(a: var SkipTable, sub: string) {.rtl,
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for i in 0 ..< m - 1:
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a[sub[i]] = m - 1 - i
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func find*(a: SkipTable, s, sub: string, start: Natural = 0, last = 0): int {.
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func initSkipTable*(sub: string): SkipTable {.noinit, rtl,
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extern: "nsuInitNewSkipTable".} =
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## Returns a new table initialized for `sub`.
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##
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## See also:
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## * `initSkipTable func<#initSkipTable,SkipTable,string>`_
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## * `find func<#find,SkipTable,string,string,Natural,int>`_
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initSkipTable(result, sub)
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func find*(a: SkipTable, s, sub: string, start: Natural = 0, last = -1): int {.
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rtl, extern: "nsuFindStrA".} =
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## Searches for `sub` in `s` inside range `start..last` using preprocessed
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## table `a`. If `last` is unspecified, it defaults to `s.high` (the last
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@@ -1832,9 +1842,10 @@ func find*(a: SkipTable, s, sub: string, start: Natural = 0, last = 0): int {.
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## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
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##
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## See also:
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## * `initSkipTable func<#initSkipTable,string>`_
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## * `initSkipTable func<#initSkipTable,SkipTable,string>`_
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let
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last = if last == 0: s.high else: last
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last = if last < 0: s.high else: last
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subLast = sub.len - 1
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if subLast == -1:
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@@ -1844,6 +1855,7 @@ func find*(a: SkipTable, s, sub: string, start: Natural = 0, last = 0): int {.
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# This is an implementation of the Boyer-Moore Horspool algorithms
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# https://en.wikipedia.org/wiki/Boyer%E2%80%93Moore%E2%80%93Horspool_algorithm
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result = -1
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var skip = start
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while last - skip >= subLast:
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@@ -1853,7 +1865,6 @@ func find*(a: SkipTable, s, sub: string, start: Natural = 0, last = 0): int {.
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return skip
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dec i
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inc skip, a[s[skip + subLast]]
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return -1
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when not (defined(js) or defined(nimdoc) or defined(nimscript)):
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func c_memchr(cstr: pointer, c: char, n: csize_t): pointer {.
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@@ -1865,10 +1876,10 @@ when not (defined(js) or defined(nimdoc) or defined(nimscript)):
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else:
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const hasCStringBuiltin = false
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func find*(s: string, sub: char, start: Natural = 0, last = 0): int {.rtl,
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func find*(s: string, sub: char, start: Natural = 0, last = -1): int {.rtl,
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extern: "nsuFindChar".} =
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## Searches for `sub` in `s` inside range `start..last` (both ends included).
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## If `last` is unspecified, it defaults to `s.high` (the last element).
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## If `last` is unspecified or negative, it defaults to `s.high` (the last element).
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##
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## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
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## Otherwise the index returned is relative to `s[0]`, not `start`.
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@@ -1877,26 +1888,30 @@ func find*(s: string, sub: char, start: Natural = 0, last = 0): int {.rtl,
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## See also:
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## * `rfind func<#rfind,string,char,Natural,int>`_
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## * `replace func<#replace,string,char,char>`_
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let last = if last == 0: s.high else: last
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when nimvm:
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result = -1
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let last = if last < 0: s.high else: last
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template findImpl =
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for i in int(start)..last:
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if sub == s[i]: return i
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if s[i] == sub:
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return i
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when nimvm:
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findImpl()
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else:
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when hasCStringBuiltin:
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let L = last-start+1
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if L > 0:
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let found = c_memchr(s[start].unsafeAddr, sub, cast[csize_t](L))
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let length = last-start+1
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if length > 0:
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let found = c_memchr(s[start].unsafeAddr, sub, cast[csize_t](length))
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if not found.isNil:
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return cast[ByteAddress](found) -% cast[ByteAddress](s.cstring)
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else:
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for i in int(start)..last:
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if sub == s[i]: return i
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return -1
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findImpl()
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func find*(s: string, chars: set[char], start: Natural = 0, last = 0): int {.
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func find*(s: string, chars: set[char], start: Natural = 0, last = -1): int {.
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rtl, extern: "nsuFindCharSet".} =
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## Searches for `chars` in `s` inside range `start..last` (both ends included).
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## If `last` is unspecified, it defaults to `s.high` (the last element).
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## If `last` is unspecified or negative, it defaults to `s.high` (the last element).
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##
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## If `s` contains none of the characters in `chars`, -1 is returned.
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## Otherwise the index returned is relative to `s[0]`, not `start`.
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@@ -1905,15 +1920,16 @@ func find*(s: string, chars: set[char], start: Natural = 0, last = 0): int {.
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## See also:
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## * `rfind func<#rfind,string,set[char],Natural,int>`_
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## * `multiReplace func<#multiReplace,string,varargs[]>`_
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let last = if last == 0: s.high else: last
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result = -1
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let last = if last < 0: s.high else: last
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for i in int(start)..last:
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if s[i] in chars: return i
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return -1
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if s[i] in chars:
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return i
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func find*(s, sub: string, start: Natural = 0, last = 0): int {.rtl,
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func find*(s, sub: string, start: Natural = 0, last = -1): int {.rtl,
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extern: "nsuFindStr".} =
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## Searches for `sub` in `s` inside range `start..last` (both ends included).
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## If `last` is unspecified, it defaults to `s.high` (the last element).
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## If `last` is unspecified or negative, it defaults to `s.high` (the last element).
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##
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## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
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## Otherwise the index returned is relative to `s[0]`, not `start`.
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@@ -1925,28 +1941,23 @@ func find*(s, sub: string, start: Natural = 0, last = 0): int {.rtl,
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if sub.len > s.len - start: return -1
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if sub.len == 1: return find(s, sub[0], start, last)
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template useSkipTable {.dirty.} =
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var a {.noinit.}: SkipTable
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initSkipTable(a, sub)
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result = find(a, s, sub, start, last)
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template useSkipTable =
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result = find(initSkipTable(sub), s, sub, start, last)
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when not hasCStringBuiltin:
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when nimvm:
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useSkipTable()
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else:
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when nimvm:
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useSkipTable()
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else:
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when hasCStringBuiltin:
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if last == 0 and s.len > start:
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let found = c_strstr(s[start].unsafeAddr, sub)
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if not found.isNil:
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result = cast[ByteAddress](found) -% cast[ByteAddress](s.cstring)
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when hasCStringBuiltin:
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if last < 0 and start < s.len:
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let found = c_strstr(s[start].unsafeAddr, sub)
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result = if not found.isNil:
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cast[ByteAddress](found) -% cast[ByteAddress](s.cstring)
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else:
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result = -1
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else:
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useSkipTable()
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-1
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else:
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useSkipTable()
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else:
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useSkipTable()
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func rfind*(s: string, sub: char, start: Natural = 0, last = -1): int {.rtl,
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extern: "nsuRFindChar".} =
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@@ -2121,8 +2132,7 @@ func replace*(s, sub: string, by = ""): string {.rtl,
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# copy the rest:
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add result, substr(s, i)
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else:
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var a {.noinit.}: SkipTable
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initSkipTable(a, sub)
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var a = initSkipTable(sub)
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let last = s.high
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var i = 0
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while true:
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@@ -2162,9 +2172,8 @@ func replaceWord*(s, sub: string, by = ""): string {.rtl,
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## replaced.
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if sub.len == 0: return s
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const wordChars = {'a'..'z', 'A'..'Z', '0'..'9', '_', '\128'..'\255'}
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var a {.noinit.}: SkipTable
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result = ""
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initSkipTable(a, sub)
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var a = initSkipTable(sub)
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var i = 0
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let last = s.high
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let sublen = sub.len
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@@ -232,18 +232,22 @@ template main() =
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{.pop.}
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block: # find
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doAssert "0123456789ABCDEFGH".find('A') == 10
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doAssert "0123456789ABCDEFGH".find('A', 5) == 10
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doAssert "0123456789ABCDEFGH".find('A', 5, 10) == 10
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doAssert "0123456789ABCDEFGH".find('A', 5, 9) == -1
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doAssert "0123456789ABCDEFGH".find("A") == 10
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doAssert "0123456789ABCDEFGH".find("A", 5) == 10
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doAssert "0123456789ABCDEFGH".find("A", 5, 10) == 10
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doAssert "0123456789ABCDEFGH".find("A", 5, 9) == -1
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doAssert "0123456789ABCDEFGH".find({'A'..'C'}) == 10
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doAssert "0123456789ABCDEFGH".find({'A'..'C'}, 5) == 10
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doAssert "0123456789ABCDEFGH".find({'A'..'C'}, 5, 10) == 10
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doAssert "0123456789ABCDEFGH".find({'A'..'C'}, 5, 9) == -1
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const haystack: string = "0123456789ABCDEFGH"
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doAssert haystack.find('A') == 10
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doAssert haystack.find('A', 5) == 10
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doAssert haystack.find('A', 5, 10) == 10
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doAssert haystack.find('A', 5, 9) == -1
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doAssert haystack.find("A") == 10
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doAssert haystack.find("A", 5) == 10
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doAssert haystack.find("A", 5, 10) == 10
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doAssert haystack.find("A", 5, 9) == -1
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doAssert haystack.find({'A'..'C'}) == 10
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doAssert haystack.find({'A'..'C'}, 5) == 10
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doAssert haystack.find({'A'..'C'}, 5, 10) == 10
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doAssert haystack.find({'A'..'C'}, 5, 9) == -1
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doAssert haystack.find('A', 0, 0) == -1 # search limited to the first char
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doAssert haystack.find('A', 5, 0) == -1 # last < start
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doAssert haystack.find('A', 5, 4) == -1 # last < start
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block:
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const haystack: string = "ABCABABABABCAB"
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@@ -290,17 +294,17 @@ template main() =
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# when last <= start, searching for non-empty string
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block:
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let last: int = -1
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doAssert "abcd".find("ab", start=0, last=last) == -1
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doAssert "abcd".find("ab", start=1, last=last) == -1
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doAssert "abcd".find("bc", start=1, last=last) == -1
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doAssert "abcd".find("bc", start=2, last=last) == -1
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block:
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let last: int = 0
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let last: int = -1 # searching through whole line
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doAssert "abcd".find("ab", start=0, last=last) == 0
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doAssert "abcd".find("ab", start=1, last=last) == -1
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doAssert "abcd".find("bc", start=1, last=last) == 1
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doAssert "abcd".find("bc", start=2, last=last) == -1
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block:
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let last: int = 0
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doAssert "abcd".find("ab", start=0, last=last) == -1
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doAssert "abcd".find("ab", start=1, last=last) == -1
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doAssert "abcd".find("bc", start=1, last=last) == -1
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doAssert "abcd".find("bc", start=2, last=last) == -1
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block:
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let last: int = 1
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doAssert "abcd".find("ab", start=0, last=last) == 0
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