Better docs, and optimizations for the chop functions

base/regex.jl

@@ -363,20 +363,36 @@ function endswith(s::SubString{String}, r::Regex)
     return PCRE.exec_r(r.regex, s, 0, r.match_options | PCRE.ENDANCHORED)
 end
 
+
+# https://stackoverflow.com/questions/5663987/how-to-properly-escape-characters-in-regexp
+_is_regex_escape(c) = in(c, raw"()[{*+.$^\|?")
+
 function chopprefix(s::AbstractString, prefix::Regex)
+    pattern = prefix.pattern
+
+    # fast path
+    startswith(s, pattern) && any(!_is_regex_escape, pattern) && return chopprefix(s, pattern)
+
     m = match(prefix, s, firstindex(s), PCRE.ANCHORED)
     m === nothing && return SubString(s)
     return SubString(s, ncodeunits(m.match) + 1)
 end
 
 function chopsuffix(s::AbstractString, suffix::Regex)
+    pattern = suffix.pattern
+
+    # fast path for regexes meant for file endings
+    startswith(pattern, raw"\.") && any(!_is_regex_escape, @view pattern[3:end]) && endswith(s, @view pattern[2:end]) && return chopsuffix(s, @view pattern[2:end])
+
+    # more general fast path
+    endswith(s, pattern) && any(!_is_regex_escape, pattern) && return chopsuffix(s, pattern)
+
     m = match(suffix, s, firstindex(s), PCRE.ENDANCHORED)
     m === nothing && return SubString(s)
     isempty(m.match) && return SubString(s)
     return SubString(s, firstindex(s), prevind(s, m.offset))
 end
 
-
 """
     match(r::Regex, s::AbstractString[, idx::Integer[, addopts]])
 

base/strings/util.jl

@@ -224,6 +224,8 @@ end
     chopprefix(s::AbstractString, prefix::Union{AbstractString,Regex}) -> SubString
 
 Remove the prefix `prefix` from `s`. If `s` does not start with `prefix`, a string equal to `s` is returned.
+Note that `prefix` can also be a regular expression, which makes this quite powerful. For example, one can
+use such to make the prefix comparison case-insensitive, with the i-modifier, see below.
 
 See also [`chopsuffix`](@ref).
 
@@ -237,6 +239,9 @@ julia> chopprefix("Hamburger", "Ham")
 
 julia> chopprefix("Hamburger", "hotdog")
 "Hamburger"
+
+julia> chopprefix("HTTP://abc.com", r"https?://"i)  # The regex with i, and "s?", to also match e.g. http and httpS (the secure variant)
+"abc.com"
 ```
 """
 function chopprefix(s::AbstractString, prefix::AbstractString)
@@ -265,6 +270,8 @@ end
     chopsuffix(s::AbstractString, suffix::Union{AbstractString,Regex}) -> SubString
 
 Remove the suffix `suffix` from `s`. If `s` does not end with `suffix`, a string equal to `s` is returned.
+Note that `suffix` can also be a regular expression, which makes this quite powerful. For example, one can
+use such to make the suffix comparison case-insensitive, with the i-modifier, see below.
 
 See also [`chopprefix`](@ref).
 
@@ -278,6 +285,9 @@ julia> chopsuffix("Hamburger", "er")
 
 julia> chopsuffix("Hamburger", "hotdog")
 "Hamburger"
+
+julia> chopsuffix("my_Julia_program.jl", r"\.jl"i)  # The regex with i, to also match e.g. .JL
+"my_Julia_program"
 ```
 """
 function chopsuffix(s::AbstractString, suffix::AbstractString)