Add strutils in-place

changelog.md

@@ -94,6 +94,8 @@ echo f
 - Added `times.isLeapDay`
 - Added a new module, `std / compilesettings` for querying the compiler about
   diverse configuration settings.
+- Added in-place `strutils.toLowerAsciiInPlace`,  `strutils.toUpperAsciiInPlace`, `strutils.capitalizeAsciiInPlace`,
+  faster than the copy versions, at least from ~1.5x to ~5x performance approx.
 
 
 ## Library changes

lib/pure/strutils.nim

@@ -2860,6 +2860,79 @@ proc isNilOrWhitespace*(s: string): bool {.noSideEffect, procvar, rtl,
   ## Alias for isEmptyOrWhitespace
   result = isEmptyOrWhitespace(s)
 
+
+since (1, 1):
+  template toLowerAsciiInPlace(c: var char) =
+    if c in {'A'..'Z'}: c = chr(ord(c) + (ord('a') - ord('A')))
+
+  template toUpperAsciiInPlace(c: var char) =
+    if c in {'a'..'z'}: c = chr(ord(c) - (ord('a') - ord('A')))
+
+
+  func toLowerAsciiInPlace*(s: var string) {.inline.} =
+    ## Converts string `s` into lower case.
+    ##
+    ## This works only for the letters ``A-Z``. See `unicode.toLower
+    ## <unicode.html#toLower,string>`_ for a version that works for any Unicode
+    ## character.
+    ##
+    ## See also:
+    ## * `normalize proc<#normalize,string>`_
+    runnableExamples:
+      var stringy = "ABCDEF"
+      toLowerAsciiInPlace(stringy)
+      doAssert stringy == "abcdef"
+      var strng = "NIM"
+      toLowerAsciiInPlace(strng)
+      doAssert strng == "nim"
+    var i = 0
+    for c in mitems(s):
+      toLowerAsciiInPlace(c)
+      s[i] = c
+      inc i
+
+
+  func toUpperAsciiInPlace*(s: var string) {.inline.} =
+    ## Converts string `s` into upper case.
+    ##
+    ## This works only for the letters ``A-Z``.  See `unicode.toUpper
+    ## <unicode.html#toUpper,string>`_ for a version that works for any Unicode
+    ## character.
+    ##
+    ## See also:
+    ## * `capitalizeAscii proc<#capitalizeAscii,string>`_
+    runnableExamples:
+      var stringo = "abcdef"
+      toUpperAsciiInPlace(stringo)
+      doAssert stringo == "ABCDEF"
+      var strng = "nim"
+      toUpperAsciiInPlace(strng)
+      doAssert strng == "NIM"
+    var i = 0
+    for c in mitems(s):
+      toUpperAsciiInPlace(c)
+      s[i] = c
+      inc i
+
+
+  func capitalizeAsciiInPlace*(s: var string) {.inline.} =
+    ## Converts the first character of string `s` into upper case.
+    ##
+    ## This works only for the letters ``A-Z``.
+    ## Use `Unicode module<unicode.html>`_ for UTF-8 support.
+    ##
+    ## See also:
+    ## * `toUpperAscii proc<#toUpperAscii,char>`_
+    runnableExamples:
+      var stringu = "foo"
+      capitalizeAsciiInPlace(stringu)
+      doAssert stringu == "Foo"
+      var stringx = "-bar"
+      capitalizeAsciiInPlace(stringx)
+      doAssert stringx == "-bar"
+    toUpperAsciiInPlace(s[0])
+
+
 when isMainModule:
   proc nonStaticTests =
     doAssert formatBiggestFloat(1234.567, ffDecimal, -1) == "1234.567000"