add StringView(iobuffer) (#17)

* add StringView(iobuffer)

* more restrictive type, more tests

Author: stevengj

Project.toml

@@ -1,7 +1,7 @@
 name = "StringViews"
 uuid = "354b36f9-a18e-4713-926e-db85100087ba"
 authors = ["Steven G. Johnson <[email protected]>"]
-version = "1.2.0"
+version = "1.3.0"
 
 [compat]
 julia = "1.6"

README.md

@@ -8,7 +8,9 @@ that provides a string representation of any underlying array of bytes
 
 Unlike Julia's built-in `String` type (which also wraps UTF-8 data), the
 `StringView` type is a copy-free wrap of *any* `AbstractVector{UInt8}`
-instance, and does not take "ownership" of or modify the array.   Otherwise,
+instance, and does not take "ownership" of or modify the array.
+You can also use `StringView(buf)` with a `buf::IOBuffer`, as
+a non-destructive alternative to `String(take!(buf))`.  Otherwise,
 a `StringView` is intended to be usable in any context where you might
 have otherwise used `String`.
 
@@ -36,6 +38,25 @@ julia> abc = StringView(0x61:0x63) # and for other array types
 "abc"
 ```
 
+Or, with an `IOBuffer`:
+
+```jl
+julia> buf = IOBuffer();
+
+julia> write(buf, b);
+
+julia> print(buf, "baz")
+
+julia> StringView(buf) # does not modify buf
+"foobarbaz"
+
+julia> String(take!(buf)) # clears buf
+"foobarbaz"
+
+julia> StringView(buf) # now empty
+""
+```
+
 Other optimized (copy-free) operations include I/O, hashing, iteration/indexing,
 comparisons, parsing, searching, and validation.  Working with a `SubString` of
 a `StringView` is similarly efficient.

src/StringViews.jl

@@ -18,6 +18,12 @@ export StringView, SVRegexMatch
 `StringView(array)` creates an `AbstractString` representation of
 any `array` of `UInt8` data, interpreted as UTF-8 encoded Unicode.
 It does *not* make a copy of or modify `array`.
+
+`StringView(buf::IOBuffer)` returns a string view of the
+current contents of the `buf`, equivalent to `String(take!(buf))`
+but without making a copy.   `StringView(buf::IOBuffer, range)`
+is a view of the bytes `range` (defaults to `1:position(buf)-1`)
+in the buffer.
 """
 struct StringView{T<:AbstractVector{UInt8}} <: AbstractString
     data::T
@@ -35,6 +41,10 @@ Base.String(s::StringViewAndSub) = String(copyto!(Base.StringVector(ncodeunits(s
 StringView(s::StringView) = s
 StringView(s::String) = StringView(codeunits(s))
 
+# iobuffer constructor (note that buf.data is always 1-based)
+StringView(buf::IOBuffer, r::OrdinalRange{<:Integer,<:Integer}=Base.OneTo(buf.ptr-1)) =
+    StringView(@view buf.data[r])
+
 Base.copy(s::StringView) = StringView(copy(s.data))
 
 Base.Symbol(s::DenseStringViewAndSub) =

test/runtests.jl

@@ -20,6 +20,16 @@ su = StringView("föôẞαr")
     @test c == "foobar"
     @test c.data !== s.data
 
+    buf = IOBuffer()
+    write(buf, s)
+    @test StringView(buf) == s == StringView(buf, 0x01:0x06)
+    @test StringView(buf, 3:5) == "oba" == StringView(buf, 0x03:0x01:0x05)
+    write(buf, "baz")
+    @test StringView(buf) == s * "baz"
+    @test String(take!(buf)) == s * "baz"
+    @test StringView(buf) == ""
+    @test_throws BoundsError StringView(buf, 3:4)
+
     @test StringView("foo") isa StringView{Base.CodeUnits{UInt8,String}}
 
     @test s isa StringViews.DenseStringView