This Julia package implements a new type of AbstractString, a StringView, that provides a string representation of any underlying array of bytes (any AbstractVector{UInt8}), interpreted as UTF-8 encoded Unicode data.

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. 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.

(In particular, as much as possible we try to implement efficient copy-free String-like operations on StringView, such as iteration and regular-expression searching, as long as the underlying UInt8 array is a contiguous dense array.)

For example:

julia> b = [0x66, 0x6f, 0x6f, 0x62, 0x61, 0x72];
julia> s = StringView(b) # does not make a copy
"foobar"
julia> collect(eachmatch(r"[aeiou]+", s))
2-element Vector{SVRegexMatch{StringView{Vector{UInt8}}}}:
 SVRegexMatch("oo")
 SVRegexMatch("a")
julia> StringView(@view b[1:3]) # also works for subarrays, with no copy
"foo"
julia> abc = StringView(0x61:0x63) # and for other array types
"abc"

Or, with an IOBuffer:

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.