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-rw-r--r--lib/impure/re.nim514
1 files changed, 222 insertions, 292 deletions
diff --git a/lib/impure/re.nim b/lib/impure/re.nim
index 809180774..053c6ab55 100644
--- a/lib/impure/re.nim
+++ b/lib/impure/re.nim
@@ -7,6 +7,9 @@
 #    distribution, for details about the copyright.
 #
 
+when defined(js):
+  {.error: "This library needs to be compiled with a c-like backend, and depends on PCRE; See jsre for JS backend.".}
+
 ## Regular expression support for Nim.
 ##
 ## This module is implemented by providing a wrapper around the
@@ -14,27 +17,43 @@
 ## C library. This means that your application will depend on the PCRE
 ## library's licence when using this module, which should not be a problem
 ## though.
+##
+## .. note:: There are also alternative nimble packages such as [tinyre](https://github.com/khchen/tinyre)
+##   and [regex](https://github.com/nitely/nim-regex).
+##
 ## PCRE's licence follows:
 ##
 ## .. include:: ../../doc/regexprs.txt
 ##
 
+runnableExamples:
+  ## Unless specified otherwise, `start` parameter in each proc indicates
+  ## where the scan starts, but outputs are relative to the start of the input
+  ## string, not to `start`:
+  doAssert find("uxabc", re"(?<=x|y)ab", start = 1) == 2 # lookbehind assertion
+  doAssert find("uxabc", re"ab", start = 3) == -1 # we're past `start` => not found
+  doAssert not match("xabc", re"^abc$", start = 1)
+    # can't match start of string since we're starting at 1
+
 import
-  pcre, strutils, rtarrays
+  std/[pcre, strutils, rtarrays]
+
+when defined(nimPreviewSlimSystem):
+  import std/syncio
 
 const
   MaxSubpatterns* = 20
     ## defines the maximum number of subpatterns that can be captured.
-    ## This limit still exists for ``replacef`` and ``parallelReplace``.
+    ## This limit still exists for `replacef` and `parallelReplace`.
 
 type
   RegexFlag* = enum     ## options for regular expressions
-    reIgnoreCase = 0,    ## do caseless matching
-    reMultiLine = 1,     ## ``^`` and ``$`` match newlines within data
-    reDotAll = 2,        ## ``.`` matches anything including NL
-    reExtended = 3,      ## ignore whitespace and ``#`` comments
-    reStudy = 4          ## study the expression (may be omitted if the
-                         ## expression will be used only once)
+    reIgnoreCase = 0,   ## do caseless matching
+    reMultiLine = 1,    ## `^` and `$` match newlines within data
+    reDotAll = 2,       ## `.` matches anything including NL
+    reExtended = 3,     ## ignore whitespace and `#` comments
+    reStudy = 4         ## study the expression (may be omitted if the
+                        ## expression will be used only once)
 
   RegexDesc = object
     h: ptr Pcre
@@ -46,10 +65,16 @@ type
     ## is raised if the pattern is no valid regular expression.
 
 when defined(gcDestructors):
-  proc `=destroy`(x: var RegexDesc) =
-    pcre.free_substring(cast[cstring](x.h))
-    if not isNil(x.e):
-      pcre.free_study(x.e)
+  when defined(nimAllowNonVarDestructor):
+    proc `=destroy`(x: RegexDesc) =
+      pcre.free_substring(cast[cstring](x.h))
+      if not isNil(x.e):
+        pcre.free_study(x.e)
+  else:
+    proc `=destroy`(x: var RegexDesc) =
+      pcre.free_substring(cast[cstring](x.h))
+      if not isNil(x.e):
+        pcre.free_study(x.e)
 
 proc raiseInvalidRegex(msg: string) {.noinline, noreturn.} =
   var e: ref RegexError
@@ -67,7 +92,7 @@ proc rawCompile(pattern: string, flags: cint): ptr Pcre =
 
 proc finalizeRegEx(x: Regex) =
   # XXX This is a hack, but PCRE does not export its "free" function properly.
-  # Sigh. The hack relies on PCRE's implementation (see ``pcre_get.c``).
+  # Sigh. The hack relies on PCRE's implementation (see `pcre_get.c`).
   # Fortunately the implementation is unlikely to change.
   pcre.free_substring(cast[cstring](x.h))
   if not isNil(x.e):
@@ -77,8 +102,8 @@ proc re*(s: string, flags = {reStudy}): Regex =
   ## Constructor of regular expressions.
   ##
   ## Note that Nim's
-  ## extended raw string literals support the syntax ``re"[abc]"`` as
-  ## a short form for ``re(r"[abc]")``. Also note that since this
+  ## extended raw string literals support the syntax `re"[abc]"` as
+  ## a short form for `re(r"[abc]")`. Also note that since this
   ## compiles the regular expression, which is expensive, you should
   ## avoid putting it directly in the arguments of the functions like
   ## the examples show below if you plan to use it a lot of times, as
@@ -129,13 +154,20 @@ proc matchOrFind(buf: cstring, pattern: Regex, matches: var openArray[string],
     else: matches[i-1] = ""
   return rawMatches[1] - rawMatches[0]
 
+const MaxReBufSize* = high(cint)
+  ## Maximum PCRE (API 1) buffer start/size equal to `high(cint)`, which even
+  ## for 64-bit systems can be either 2`31`:sup:-1 or 2`63`:sup:-1.
+
 proc findBounds*(buf: cstring, pattern: Regex, matches: var openArray[string],
                  start = 0, bufSize: int): tuple[first, last: int] =
-  ## returns the starting position and end position of ``pattern`` in ``buf``
-  ## (where ``buf`` has length ``bufSize`` and is not necessarily ``'\0'`` terminated),
+  ## returns the starting position and end position of `pattern` in `buf`
+  ## (where `buf` has length `bufSize` and is not necessarily `'\0'` terminated),
   ## and the captured
-  ## substrings in the array ``matches``. If it does not match, nothing
-  ## is written into ``matches`` and ``(-1,0)`` is returned.
+  ## substrings in the array `matches`. If it does not match, nothing
+  ## is written into `matches` and `(-1,0)` is returned.
+  ##
+  ## Note: The memory for `matches` needs to be allocated before this function is
+  ## called, otherwise it will just remain empty.
   var
     rtarray = initRtArray[cint]((matches.len+1)*3)
     rawMatches = rtarray.getRawData
@@ -151,20 +183,31 @@ proc findBounds*(buf: cstring, pattern: Regex, matches: var openArray[string],
 
 proc findBounds*(s: string, pattern: Regex, matches: var openArray[string],
                  start = 0): tuple[first, last: int] {.inline.} =
-  ## returns the starting position and end position of ``pattern`` in ``s``
-  ## and the captured substrings in the array ``matches``.
+  ## returns the starting position and end position of `pattern` in `s`
+  ## and the captured substrings in the array `matches`.
   ## If it does not match, nothing
-  ## is written into ``matches`` and ``(-1,0)`` is returned.
-  result = findBounds(cstring(s), pattern, matches, start, s.len)
+  ## is written into `matches` and `(-1,0)` is returned.
+  ##
+  ## .. note:: The memory for `matches` needs to be allocated before this function is called, otherwise it will just remain empty.
+  runnableExamples:
+    var matches = newSeq[string](1)
+    let (first, last) = findBounds("Hello World", re"(W\w+)", matches)
+    doAssert first == 6
+    doAssert last == 10
+    doAssert matches[0] == "World"
+  result = findBounds(cstring(s), pattern, matches,
+      min(start, MaxReBufSize), min(s.len, MaxReBufSize))
 
 proc findBounds*(buf: cstring, pattern: Regex,
                  matches: var openArray[tuple[first, last: int]],
-                 start = 0, bufSize = 0): tuple[first, last: int] =
-  ## returns the starting position and end position of ``pattern`` in ``buf``
-  ## (where ``buf`` has length ``bufSize`` and is not necessarily ``'\0'`` terminated),
-  ## and the captured substrings in the array ``matches``.
-  ## If it does not match, nothing is written into ``matches`` and
-  ## ``(-1,0)`` is returned.
+                 start = 0, bufSize: int): tuple[first, last: int] =
+  ## returns the starting position and end position of `pattern` in `buf`
+  ## (where `buf` has length `bufSize` and is not necessarily `'\0'` terminated),
+  ## and the captured substrings in the array `matches`.
+  ## If it does not match, nothing is written into `matches` and
+  ## `(-1,0)` is returned.
+  ##
+  ## .. note:: The memory for `matches` needs to be allocated before this function is called, otherwise it will just remain empty.
   var
     rtarray = initRtArray[cint]((matches.len+1)*3)
     rawMatches = rtarray.getRawData
@@ -181,17 +224,38 @@ proc findBounds*(buf: cstring, pattern: Regex,
 proc findBounds*(s: string, pattern: Regex,
                  matches: var openArray[tuple[first, last: int]],
                  start = 0): tuple[first, last: int] {.inline.} =
-  ## returns the starting position and end position of ``pattern`` in ``s``
-  ## and the captured substrings in the array ``matches``.
-  ## If it does not match, nothing is written into ``matches`` and
-  ## ``(-1,0)`` is returned.
-  result = findBounds(cstring(s), pattern, matches, start, s.len)
+  ## returns the starting position and end position of `pattern` in `s`
+  ## and the captured substrings in the array `matches`.
+  ## If it does not match, nothing is written into `matches` and
+  ## `(-1,0)` is returned.
+  ##
+  ## .. note:: The memory for `matches` needs to be allocated before this function is called, otherwise it will just remain empty.
+  runnableExamples:
+    var matches = newSeq[tuple[first, last: int]](1)
+    let (first, last) = findBounds("Hello World", re"(\w+)", matches)
+    doAssert first == 0
+    doAssert last == 4
+    doAssert matches[0] == (0, 4)
+  result = findBounds(cstring(s), pattern, matches,
+      min(start, MaxReBufSize), min(s.len, MaxReBufSize))
+
+proc findBoundsImpl(buf: cstring, pattern: Regex,
+                    start = 0, bufSize = 0, flags = 0): tuple[first, last: int] =
+  var rtarray = initRtArray[cint](3)
+  let rawMatches = rtarray.getRawData
+  let res = pcre.exec(pattern.h, pattern.e, buf, bufSize.cint, start.cint, flags.int32,
+                cast[ptr cint](rawMatches), 3)
+
+  if res < 0'i32:
+    result = (-1, 0)
+  else:
+    result = (int(rawMatches[0]), int(rawMatches[1]-1))
 
 proc findBounds*(buf: cstring, pattern: Regex,
                  start = 0, bufSize: int): tuple[first, last: int] =
-  ## returns the ``first`` and ``last`` position of ``pattern`` in ``buf``,
-  ## where ``buf`` has length ``bufSize`` (not necessarily ``'\0'`` terminated).
-  ## If it does not match, ``(-1,0)`` is returned.
+  ## returns the `first` and `last` position of `pattern` in `buf`,
+  ## where `buf` has length `bufSize` (not necessarily `'\0'` terminated).
+  ## If it does not match, `(-1,0)` is returned.
   var
     rtarray = initRtArray[cint](3)
     rawMatches = rtarray.getRawData
@@ -202,16 +266,14 @@ proc findBounds*(buf: cstring, pattern: Regex,
 
 proc findBounds*(s: string, pattern: Regex,
                  start = 0): tuple[first, last: int] {.inline.} =
-  ## returns the ``first`` and ``last`` position of ``pattern`` in ``s``.
-  ## If it does not match, ``(-1,0)`` is returned.
+  ## returns the `first` and `last` position of `pattern` in `s`.
+  ## If it does not match, `(-1,0)` is returned.
   ##
   ## Note: there is a speed improvement if the matches do not need to be captured.
-  ##
-  ## Example:
-  ##
-  ## .. code-block:: nim
-  ##   assert findBounds("01234abc89", re"abc") == (5,7)
-  result = findBounds(cstring(s), pattern, start, s.len)
+  runnableExamples:
+    assert findBounds("01234abc89", re"abc") == (5,7)
+  result = findBounds(cstring(s), pattern,
+      min(start, MaxReBufSize), min(s.len, MaxReBufSize))
 
 proc matchOrFind(buf: cstring, pattern: Regex, start, bufSize: int, flags: cint): cint =
   var
@@ -224,72 +286,77 @@ proc matchOrFind(buf: cstring, pattern: Regex, start, bufSize: int, flags: cint)
 
 proc matchLen*(s: string, pattern: Regex, matches: var openArray[string],
               start = 0): int {.inline.} =
-  ## the same as ``match``, but it returns the length of the match,
-  ## if there is no match, ``-1`` is returned. Note that a match length
+  ## the same as `match`, but it returns the length of the match,
+  ## if there is no match, `-1` is returned. Note that a match length
   ## of zero can happen.
+  ##
+  ## .. note:: The memory for `matches` needs to be allocated before this function is called, otherwise it will just remain empty.
   result = matchOrFind(cstring(s), pattern, matches, start.cint, s.len.cint, pcre.ANCHORED)
 
 proc matchLen*(buf: cstring, pattern: Regex, matches: var openArray[string],
               start = 0, bufSize: int): int {.inline.} =
-  ## the same as ``match``, but it returns the length of the match,
-  ## if there is no match, ``-1`` is returned. Note that a match length
+  ## the same as `match`, but it returns the length of the match,
+  ## if there is no match, `-1` is returned. Note that a match length
   ## of zero can happen.
+  ##
+  ## .. note:: The memory for `matches` needs to be allocated before this function is called, otherwise it will just remain empty.
   return matchOrFind(buf, pattern, matches, start.cint, bufSize.cint, pcre.ANCHORED)
 
 proc matchLen*(s: string, pattern: Regex, start = 0): int {.inline.} =
-  ## the same as ``match``, but it returns the length of the match,
-  ## if there is no match, ``-1`` is returned. Note that a match length
+  ## the same as `match`, but it returns the length of the match,
+  ## if there is no match, `-1` is returned. Note that a match length
   ## of zero can happen.
   ##
-  ## Example:
-  ##
-  ## .. code-block:: nim
-  ##   echo matchLen("abcdefg", re"cde", 2)  # =>  3
-  ##   echo matchLen("abcdefg", re"abcde")   # =>  5
-  ##   echo matchLen("abcdefg", re"cde")     # => -1
+  runnableExamples:
+    doAssert matchLen("abcdefg", re"cde", 2) == 3
+    doAssert matchLen("abcdefg", re"abcde") == 5
+    doAssert matchLen("abcdefg", re"cde") == -1
   result = matchOrFind(cstring(s), pattern, start.cint, s.len.cint, pcre.ANCHORED)
 
 proc matchLen*(buf: cstring, pattern: Regex, start = 0, bufSize: int): int {.inline.} =
-  ## the same as ``match``, but it returns the length of the match,
-  ## if there is no match, ``-1`` is returned. Note that a match length
+  ## the same as `match`, but it returns the length of the match,
+  ## if there is no match, `-1` is returned. Note that a match length
   ## of zero can happen.
   result = matchOrFind(buf, pattern, start.cint, bufSize, pcre.ANCHORED)
 
 proc match*(s: string, pattern: Regex, start = 0): bool {.inline.} =
-  ## returns ``true`` if ``s[start..]`` matches the ``pattern``.
+  ## returns `true` if `s[start..]` matches the `pattern`.
   result = matchLen(cstring(s), pattern, start, s.len) != -1
 
 proc match*(s: string, pattern: Regex, matches: var openArray[string],
            start = 0): bool {.inline.} =
-  ## returns ``true`` if ``s[start..]`` matches the ``pattern`` and
-  ## the captured substrings in the array ``matches``. If it does not
-  ## match, nothing is written into ``matches`` and ``false`` is
+  ## returns `true` if `s[start..]` matches the `pattern` and
+  ## the captured substrings in the array `matches`. If it does not
+  ## match, nothing is written into `matches` and `false` is
   ## returned.
   ##
-  ## Example:
-  ##
-  ## .. code-block:: nim
-  ##   var matches: array[2, string]
-  ##   if match("abcdefg", re"c(d)ef(g)", matches, 2):
-  ##     for s in matches:
-  ##       echo s       # => d g
+  ## .. note:: The memory for `matches` needs to be allocated before this function is called, otherwise it will just remain empty.
+  runnableExamples:
+    import std/sequtils
+    var matches: array[2, string]
+    if match("abcdefg", re"c(d)ef(g)", matches, 2):
+      doAssert toSeq(matches) == @["d", "g"]
   result = matchLen(cstring(s), pattern, matches, start, s.len) != -1
 
 proc match*(buf: cstring, pattern: Regex, matches: var openArray[string],
            start = 0, bufSize: int): bool {.inline.} =
-  ## returns ``true`` if ``buf[start..<bufSize]`` matches the ``pattern`` and
-  ## the captured substrings in the array ``matches``. If it does not
-  ## match, nothing is written into ``matches`` and ``false`` is
+  ## returns `true` if `buf[start..<bufSize]` matches the `pattern` and
+  ## the captured substrings in the array `matches`. If it does not
+  ## match, nothing is written into `matches` and `false` is
   ## returned.
-  ## ``buf`` has length ``bufSize`` (not necessarily ``'\0'`` terminated).
+  ## `buf` has length `bufSize` (not necessarily `'\0'` terminated).
+  ##
+  ## .. note:: The memory for `matches` needs to be allocated before this function is called, otherwise it will just remain empty.
   result = matchLen(buf, pattern, matches, start, bufSize) != -1
 
 proc find*(buf: cstring, pattern: Regex, matches: var openArray[string],
-           start = 0, bufSize = 0): int =
-  ## returns the starting position of ``pattern`` in ``buf`` and the captured
-  ## substrings in the array ``matches``. If it does not match, nothing
-  ## is written into ``matches`` and ``-1`` is returned.
-  ## ``buf`` has length ``bufSize`` (not necessarily ``'\0'`` terminated).
+           start = 0, bufSize: int): int =
+  ## returns the starting position of `pattern` in `buf` and the captured
+  ## substrings in the array `matches`. If it does not match, nothing
+  ## is written into `matches` and `-1` is returned.
+  ## `buf` has length `bufSize` (not necessarily `'\0'` terminated).
+  ##
+  ## .. note:: The memory for `matches` needs to be allocated before this function is called, otherwise it will just remain empty.
   var
     rtarray = initRtArray[cint]((matches.len+1)*3)
     rawMatches = rtarray.getRawData
@@ -305,15 +372,17 @@ proc find*(buf: cstring, pattern: Regex, matches: var openArray[string],
 
 proc find*(s: string, pattern: Regex, matches: var openArray[string],
            start = 0): int {.inline.} =
-  ## returns the starting position of ``pattern`` in ``s`` and the captured
-  ## substrings in the array ``matches``. If it does not match, nothing
-  ## is written into ``matches`` and ``-1`` is returned.
+  ## returns the starting position of `pattern` in `s` and the captured
+  ## substrings in the array `matches`. If it does not match, nothing
+  ## is written into `matches` and `-1` is returned.
+  ##
+  ## .. note:: The memory for `matches` needs to be allocated before this function is called, otherwise it will just remain empty.
   result = find(cstring(s), pattern, matches, start, s.len)
 
 proc find*(buf: cstring, pattern: Regex, start = 0, bufSize: int): int =
-  ## returns the starting position of ``pattern`` in ``buf``,
-  ## where ``buf`` has length ``bufSize`` (not necessarily ``'\0'`` terminated).
-  ## If it does not match, ``-1`` is returned.
+  ## returns the starting position of `pattern` in `buf`,
+  ## where `buf` has length `bufSize` (not necessarily `'\0'` terminated).
+  ## If it does not match, `-1` is returned.
   var
     rtarray = initRtArray[cint](3)
     rawMatches = rtarray.getRawData
@@ -323,15 +392,16 @@ proc find*(buf: cstring, pattern: Regex, start = 0, bufSize: int): int =
   return rawMatches[0]
 
 proc find*(s: string, pattern: Regex, start = 0): int {.inline.} =
-  ## returns the starting position of ``pattern`` in ``s``. If it does not
-  ## match, ``-1`` is returned.
-  ##
-  ## Example:
-  ##
-  ## .. code-block:: nim
-  ##  echo find("abcdefg", re"cde")  # => 2
-  ##  echo find("abcdefg", re"abc")  # => 0
-  ##  echo find("abcdefg", re"zz")  # => -1
+  ## returns the starting position of `pattern` in `s`. If it does not
+  ## match, `-1` is returned. We start the scan at `start`.
+  runnableExamples:
+    doAssert find("abcdefg", re"cde") == 2
+    doAssert find("abcdefg", re"abc") == 0
+    doAssert find("abcdefg", re"zz") == -1 # not found
+    doAssert find("abcdefg", re"cde", start = 2) == 2 # still 2
+    doAssert find("abcdefg", re"cde", start = 3) == -1 # we're past the start position
+    doAssert find("xabc", re"(?<=x|y)abc", start = 1) == 1
+      # lookbehind assertion `(?<=x|y)` can look behind `start`
   result = find(cstring(s), pattern, start, s.len)
 
 iterator findAll*(s: string, pattern: Regex, start = 0): string =
@@ -354,7 +424,7 @@ iterator findAll*(s: string, pattern: Regex, start = 0): string =
     i = b
 
 iterator findAll*(buf: cstring, pattern: Regex, start = 0, bufSize: int): string =
-  ## Yields all matching `substrings` of ``s`` that match ``pattern``.
+  ## Yields all matching `substrings` of `s` that match `pattern`.
   ##
   ## Note that since this is an iterator you should not modify the string you
   ## are iterating over: bad things could happen.
@@ -375,32 +445,25 @@ iterator findAll*(buf: cstring, pattern: Regex, start = 0, bufSize: int): string
     i = b
 
 proc findAll*(s: string, pattern: Regex, start = 0): seq[string] {.inline.} =
-  ## returns all matching `substrings` of ``s`` that match ``pattern``.
-  ## If it does not match, @[] is returned.
+  ## returns all matching `substrings` of `s` that match `pattern`.
+  ## If it does not match, `@[]` is returned.
   result = @[]
   for x in findAll(s, pattern, start): result.add x
 
-when not defined(nimhygiene):
-  {.pragma: inject.}
-
 template `=~` *(s: string, pattern: Regex): untyped =
-  ## This calls ``match`` with an implicit declared ``matches`` array that
-  ## can be used in the scope of the ``=~`` call:
-  ##
-  ## .. code-block:: nim
-  ##
-  ##   if line =~ re"\s*(\w+)\s*\=\s*(\w+)":
-  ##     # matches a key=value pair:
-  ##     echo("Key: ", matches[0])
-  ##     echo("Value: ", matches[1])
-  ##   elif line =~ re"\s*(\#.*)":
-  ##     # matches a comment
-  ##     # note that the implicit ``matches`` array is different from the
-  ##     # ``matches`` array of the first branch
-  ##     echo("comment: ", matches[0])
-  ##   else:
-  ##     echo("syntax error")
-  ##
+  ## This calls `match` with an implicit declared `matches` array that
+  ## can be used in the scope of the `=~` call:
+  runnableExamples:
+    proc parse(line: string): string =
+      if line =~ re"\s*(\w+)\s*\=\s*(\w+)": # matches a key=value pair:
+        result = $(matches[0], matches[1])
+      elif line =~ re"\s*(\#.*)": # matches a comment
+        # note that the implicit `matches` array is different from 1st branch
+        result = $(matches[0],)
+      else: raiseAssert "unreachable"
+      doAssert not declared(matches)
+    doAssert parse("NAME = LENA") == """("NAME", "LENA")"""
+    doAssert parse("   # comment ... ") == """("# comment ... ",)"""
   bind MaxSubpatterns
   when not declaredInScope(matches):
     var matches {.inject.}: array[MaxSubpatterns, string]
@@ -409,12 +472,14 @@ template `=~` *(s: string, pattern: Regex): untyped =
 # ------------------------- more string handling ------------------------------
 
 proc contains*(s: string, pattern: Regex, start = 0): bool {.inline.} =
-  ## same as ``find(s, pattern, start) >= 0``
+  ## same as `find(s, pattern, start) >= 0`
   return find(s, pattern, start) >= 0
 
 proc contains*(s: string, pattern: Regex, matches: var openArray[string],
               start = 0): bool {.inline.} =
-  ## same as ``find(s, pattern, matches, start) >= 0``
+  ## same as `find(s, pattern, matches, start) >= 0`
+  ##
+  ## .. note:: The memory for `matches` needs to be allocated before this function is called, otherwise it will just remain empty.
   return find(s, pattern, matches, start) >= 0
 
 proc startsWith*(s: string, prefix: Regex): bool {.inline.} =
@@ -427,44 +492,32 @@ proc endsWith*(s: string, suffix: Regex): bool {.inline.} =
     if matchLen(s, suffix, i) == s.len - i: return true
 
 proc replace*(s: string, sub: Regex, by = ""): string =
-  ## Replaces ``sub`` in ``s`` by the string ``by``. Captures cannot be
-  ## accessed in ``by``.
-  ##
-  ## Example:
-  ##
-  ## .. code-block:: nim
-  ##   "var1=key; var2=key2".replace(re"(\w+)=(\w+)")
-  ##
-  ## Results in:
-  ##
-  ## .. code-block:: nim
-  ##
-  ##   "; "
+  ## Replaces `sub` in `s` by the string `by`. Captures cannot be
+  ## accessed in `by`.
+  runnableExamples:
+    doAssert "var1=key; var2=key2".replace(re"(\w+)=(\w+)") == "; "
+    doAssert "var1=key; var2=key2".replace(re"(\w+)=(\w+)", "?") == "?; ?"
   result = ""
   var prev = 0
+  var flags = int32(0)
   while prev < s.len:
-    var match = findBounds(s, sub, prev)
+    var match = findBoundsImpl(s.cstring, sub, prev, s.len, flags)
+    flags = 0
     if match.first < 0: break
     add(result, substr(s, prev, match.first-1))
     add(result, by)
-    if match.last + 1 == prev: break
+    if match.first > match.last:
+      # 0-len match
+      flags = pcre.NOTEMPTY_ATSTART
     prev = match.last + 1
   add(result, substr(s, prev))
 
 proc replacef*(s: string, sub: Regex, by: string): string =
-  ## Replaces ``sub`` in ``s`` by the string ``by``. Captures can be accessed in ``by``
-  ## with the notation ``$i`` and ``$#`` (see strutils.\`%\`).
-  ##
-  ## Example:
-  ##
-  ## .. code-block:: nim
-  ##   "var1=key; var2=key2".replacef(re"(\w+)=(\w+)", "$1<-$2$2")
-  ##
-  ## Results in:
-  ##
-  ## .. code-block:: nim
-  ##
-  ## "var1<-keykey; var2<-key2key2"
+  ## Replaces `sub` in `s` by the string `by`. Captures can be accessed in `by`
+  ## with the notation `$i` and `$#` (see strutils.\`%\`).
+  runnableExamples:
+    doAssert "var1=key; var2=key2".replacef(re"(\w+)=(\w+)", "$1<-$2$2") ==
+      "var1<-keykey; var2<-key2key2"
   result = ""
   var caps: array[MaxSubpatterns, string]
   var prev = 0
@@ -479,7 +532,7 @@ proc replacef*(s: string, sub: Regex, by: string): string =
 
 proc multiReplace*(s: string, subs: openArray[
                    tuple[pattern: Regex, repl: string]]): string =
-  ## Returns a modified copy of ``s`` with the substitutions in ``subs``
+  ## Returns a modified copy of `s` with the substitutions in `subs`
   ## applied in parallel.
   result = ""
   var i = 0
@@ -497,58 +550,41 @@ proc multiReplace*(s: string, subs: openArray[
   # copy the rest:
   add(result, substr(s, i))
 
-proc parallelReplace*(s: string, subs: openArray[
-  tuple[pattern: Regex, repl: string]]): string {.deprecated:
-  "Deprecated since v0.18.0: Use ``multiReplace`` instead.".} =
-  ## Returns a modified copy of ``s`` with the substitutions in ``subs``
-  ## applied in parallel.
-  result = multiReplace(s, subs)
-
 proc transformFile*(infile, outfile: string,
                     subs: openArray[tuple[pattern: Regex, repl: string]]) =
-  ## reads in the file ``infile``, performs a parallel replacement (calls
-  ## ``parallelReplace``) and writes back to ``outfile``. Raises ``IOError`` if an
+  ## reads in the file `infile`, performs a parallel replacement (calls
+  ## `parallelReplace`) and writes back to `outfile`. Raises `IOError` if an
   ## error occurs. This is supposed to be used for quick scripting.
-  var x = readFile(infile).string
+  var x = readFile(infile)
   writeFile(outfile, x.multiReplace(subs))
 
 iterator split*(s: string, sep: Regex; maxsplit = -1): string =
-  ## Splits the string ``s`` into substrings.
-  ##
-  ## Substrings are separated by the regular expression ``sep``
-  ## (and the portion matched by ``sep`` is not returned).
-  ##
-  ## Example:
-  ##
-  ## .. code-block:: nim
-  ##   for word in split("00232this02939is39an22example111", re"\d+"):
-  ##     writeLine(stdout, word)
-  ##
-  ## Results in:
-  ##
-  ## .. code-block:: nim
-  ##   ""
-  ##   "this"
-  ##   "is"
-  ##   "an"
-  ##   "example"
-  ##   ""
-  ##
+  ## Splits the string `s` into substrings.
+  ##
+  ## Substrings are separated by the regular expression `sep`
+  ## (and the portion matched by `sep` is not returned).
+  runnableExamples:
+    import std/sequtils
+    doAssert toSeq(split("00232this02939is39an22example111", re"\d+")) ==
+      @["", "this", "is", "an", "example", ""]
   var last = 0
   var splits = maxsplit
-  var x: int
+  var x = -1
+  if len(s) == 0:
+    last = 1
+  if matchLen(s, sep, 0) == 0:
+    x = 0
   while last <= len(s):
     var first = last
     var sepLen = 1
+    if x == 0:
+      inc(last)
     while last < len(s):
       x = matchLen(s, sep, last)
       if x >= 0:
         sepLen = x
         break
       inc(last)
-    if x == 0:
-      if last >= len(s): break
-      inc last
     if splits == 0: last = len(s)
     yield substr(s, first, last-1)
     if splits == 0: break
@@ -556,14 +592,14 @@ iterator split*(s: string, sep: Regex; maxsplit = -1): string =
     inc(last, sepLen)
 
 proc split*(s: string, sep: Regex, maxsplit = -1): seq[string] {.inline.} =
-  ## Splits the string ``s`` into a seq of substrings.
+  ## Splits the string `s` into a seq of substrings.
   ##
-  ## The portion matched by ``sep`` is not returned.
+  ## The portion matched by `sep` is not returned.
   result = @[]
   for x in split(s, sep, maxsplit): result.add x
 
 proc escapeRe*(s: string): string =
-  ## escapes ``s`` so that it is matched verbatim when used as a regular
+  ## escapes `s` so that it is matched verbatim when used as a regular
   ## expression.
   result = ""
   for c in items(s):
@@ -573,109 +609,3 @@ proc escapeRe*(s: string): string =
     else:
       result.add("\\x")
       result.add(toHex(ord(c), 2))
-
-when isMainModule:
-  doAssert match("(a b c)", rex"\( .* \)")
-  doAssert match("WHiLe", re("while", {reIgnoreCase}))
-
-  doAssert "0158787".match(re"\d+")
-  doAssert "ABC 0232".match(re"\w+\s+\d+")
-  doAssert "ABC".match(rex"\d+ | \w+")
-
-  {.push warnings:off.}
-  doAssert matchLen("key", re"\b[a-zA-Z_]+[a-zA-Z_0-9]*\b") == 3
-  {.pop.}
-
-  var pattern = re"[a-z0-9]+\s*=\s*[a-z0-9]+"
-  doAssert matchLen("key1=  cal9", pattern) == 11
-
-  doAssert find("_____abc_______", re"abc") == 5
-  doAssert findBounds("_____abc_______", re"abc") == (5,7)
-
-  var matches: array[6, string]
-  if match("abcdefg", re"c(d)ef(g)", matches, 2):
-    doAssert matches[0] == "d"
-    doAssert matches[1] == "g"
-  else:
-    doAssert false
-
-  if "abc" =~ re"(a)bcxyz|(\w+)":
-    doAssert matches[1] == "abc"
-  else:
-    doAssert false
-
-  if "abc" =~ re"(cba)?.*":
-    doAssert matches[0] == ""
-  else: doAssert false
-
-  if "abc" =~ re"().*":
-    doAssert matches[0] == ""
-  else: doAssert false
-
-  doAssert "var1=key; var2=key2".endsWith(re"\w+=\w+")
-  doAssert("var1=key; var2=key2".replacef(re"(\w+)=(\w+)", "$1<-$2$2") ==
-         "var1<-keykey; var2<-key2key2")
-  doAssert("var1=key; var2=key2".replace(re"(\w+)=(\w+)", "$1<-$2$2") ==
-         "$1<-$2$2; $1<-$2$2")
-
-  var accum: seq[string] = @[]
-  for word in split("00232this02939is39an22example111", re"\d+"):
-    accum.add(word)
-  doAssert(accum == @["", "this", "is", "an", "example", ""])
-
-  accum = @[]
-  for word in split("00232this02939is39an22example111", re"\d+", maxsplit=2):
-    accum.add(word)
-  doAssert(accum == @["", "this", "is39an22example111"])
-
-  accum = @[]
-  for word in split("AAA :   : BBB", re"\s*:\s*"):
-    accum.add(word)
-  doAssert(accum == @["AAA", "", "BBB"])
-
-  doAssert(split("abc", re"") == @["a", "b", "c"])
-  doAssert(split("", re"") == @[])
-
-  doAssert(split("a;b;c", re";") == @["a", "b", "c"])
-  doAssert(split(";a;b;c", re";") == @["", "a", "b", "c"])
-  doAssert(split(";a;b;c;", re";") == @["", "a", "b", "c", ""])
-  doAssert(split("a;b;c;", re";") == @["a", "b", "c", ""])
-  doAssert(split("00232this02939is39an22example111", re"\d+", maxsplit=2) == @["", "this", "is39an22example111"])
-
-
-  for x in findAll("abcdef", re"^{.}", 3):
-    doAssert x == "d"
-  accum = @[]
-  for x in findAll("abcdef", re".", 3):
-    accum.add(x)
-  doAssert(accum == @["d", "e", "f"])
-
-  doAssert("XYZ".find(re"^\d*") == 0)
-  doAssert("XYZ".match(re"^\d*") == true)
-
-  block:
-    var matches: array[16, string]
-    if match("abcdefghijklmnop", re"(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)(l)(m)(n)(o)(p)", matches):
-      for i in 0..matches.high:
-        doAssert matches[i] == $chr(i + 'a'.ord)
-    else:
-      doAssert false
-
-  block:   # Buffer based RE
-    var cs: cstring = "_____abc_______"
-    doAssert(cs.find(re"abc", bufSize=15) == 5)
-    doAssert(cs.matchLen(re"_*abc", bufSize=15) == 8)
-    doAssert(cs.matchLen(re"abc", start=5, bufSize=15) == 3)
-    doAssert(cs.matchLen(re"abc", start=5, bufSize=7) == -1)
-    doAssert(cs.matchLen(re"abc_*", start=5, bufSize=10) == 5)
-    var accum: seq[string] = @[]
-    for x in cs.findAll(re"[a-z]", start=3, bufSize=15):
-      accum.add($x)
-    doAssert(accum == @["a","b","c"])
-
-  block:
-    # bug #9306
-    doAssert replace("bar", re"^", "foo") == "foobar"
-    doAssert replace("foo", re"", "-") == "-foo"
-    doAssert replace("foo", re"$", "bar") == "foobar"
-