Add RepString from Base (#9)

* Add RepString from Base

* Use isdefined

* Mention RepString in the README

[ci skip]

Author: ararslan

README.md

@@ -6,14 +6,15 @@
 [![Julia 0.4 Status](http://pkg.julialang.org/badges/LegacyStrings_0.4.svg)](http://pkg.julialang.org/?pkg=LegacyStrings&ver=0.4)
 [![Julia 0.5 Status](http://pkg.julialang.org/badges/LegacyStrings_0.5.svg)](http://pkg.julialang.org/?pkg=LegacyStrings&ver=0.5)
 
-The LegacyStrings package provides compatibility string types from Julia 0.4 (and earlier), which were removed in Julia 0.5, including:
+The LegacyStrings package provides compatibility string types from Julia 0.5 (and earlier), which were removed in subsequent versions, including:
 
 - `ASCIIString`: a single-byte-per character string type that can only hold ASCII string data.
 - `UTF8String`: a string type with single byte code units (`UInt8`), encoding strings as UTF-8.
 - `UTF16String`: a string type with two-byte native-endian code units (`UInt16`), encoding strings as UTF-16.
 - `UTF32String`: a string type with four-byte native-endian code units (`UInt32`), encoding strings as UTF-32.
 - `ByteString`: a type alias for `Union{ASCIIString,UTF8String}`, i.e. strings that can be passed to C directly.
 - `WString`: an alias for `UTF16String` if `Cwchart_t` is two bytes (i.e. Windows) or `UTF32String` otherwise.
+- `RepString`: a string type for efficient handling of repeated strings.
 
 LegacyStrings also defines and exports converter functions for these types, i.e.:
 

src/LegacyStrings.jl

@@ -7,6 +7,7 @@ module LegacyStrings
 export
     ByteString,
     ASCIIString,
+    RepString,
     UTF8String,
     UTF16String,
     UTF32String,
@@ -81,4 +82,10 @@ import Base:
     else
         using Base: UTF_ERR_SHORT, checkstring
     end
+
+    if isdefined(Base, :RepString)
+        using Base: RepString
+    else
+        include("rep.jl")
+    end
 end # module

src/rep.jl

@@ -0,0 +1,33 @@
+# This file includes code that was formerly a part of Julia. License is MIT: http://julialang.org/license
+
+immutable RepString <: AbstractString
+    string::AbstractString
+    repeat::Integer
+end
+
+function endof(s::RepString)
+    e = endof(s.string)
+    (next(s.string,e)[2]-1) * (s.repeat-1) + e
+end
+length(s::RepString) = length(s.string)*s.repeat
+sizeof(s::RepString) = sizeof(s.string)*s.repeat
+
+function next(s::RepString, i::Int)
+    if i < 1
+        throw(BoundsError(s, i))
+    end
+    e = endof(s.string)
+    sz = next(s.string,e)[2]-1
+
+    r, j = divrem(i-1, sz)
+    j += 1
+
+    if r >= s.repeat || j > e
+        throw(BoundsError(s, i))
+    end
+
+    c, k = next(s.string, j)
+    c, k-j+i
+end
+
+convert(::Type{RepString}, s::AbstractString) = RepString(s,1)

test/runtests.jl

@@ -518,3 +518,31 @@ let str = ascii("this ")
 end
 
 @test isvalid(Char['f','o','o','b','a','r'])
+
+
+## Repeat strings ##
+
+# Base Julia issue #7764
+let
+    rs = RepString("foo", 2)
+    @test length(rs) == 6
+    @test sizeof(rs) == 6
+    @test isascii(rs)
+    @test convert(RepString, "foobar") == "foobar"
+    @test typeof(convert(RepString, "foobar")) == RepString
+
+    srep = RepString("Σβ",2)
+    s="Σβ"
+    ss=SubString(s,1,endof(s))
+
+    @test ss^2 == "ΣβΣβ"
+    @test RepString(ss,2) == "ΣβΣβ"
+
+    @test endof(srep) == 7
+
+    @test next(srep, 3) == ('β',5)
+    @test next(srep, 7) == ('β',9)
+
+    @test srep[7] == 'β'
+    @test_throws BoundsError srep[8]
+end