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add bytes2hex(io, a) method #27124

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May 20, 2018
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add bytes2hex(io, a) method #27124

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3 changes: 3 additions & 0 deletions NEWS.md
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Original file line number Diff line number Diff line change
Expand Up @@ -478,6 +478,9 @@ Library improvements
* `Char` is now a subtype of `AbstractChar`, and most of the functions that
take character arguments now accept any `AbstractChar` ([#26286]).

* `bytes2hex` now accepts an optional `io` argument to output to a hexadecimal stream
without allocating a `String` first ([#27121]).

* `String(array)` now accepts an arbitrary `AbstractVector{UInt8}`. For `Vector`
inputs, it "steals" the memory buffer, leaving them with an empty buffer which
is guaranteed not to be shared with the `String` object. For other types of vectors
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5 changes: 3 additions & 2 deletions base/loading.jl
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Expand Up @@ -91,10 +91,11 @@ struct SHA1
end
end
SHA1(s::AbstractString) = SHA1(hex2bytes(s))

string(hash::SHA1) = bytes2hex(hash.bytes)
print(io::IO, hash::SHA1) = print(io, string(hash))
print(io::IO, hash::SHA1) = bytes2hex(io, hash.bytes)
show(io::IO, hash::SHA1) = print(io, "SHA1(\"", hash, "\")")

show(io::IO, hash::SHA1) = print(io, "SHA1(\"", string(hash), "\")")
isless(a::SHA1, b::SHA1) = lexless(a.bytes, b.bytes)
hash(a::SHA1, h::UInt) = hash((SHA1, a.bytes), h)
==(a::SHA1, b::SHA1) = a.bytes == b.bytes
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18 changes: 14 additions & 4 deletions base/strings/util.jl
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Expand Up @@ -547,10 +547,13 @@ end
throw(ArgumentError("byte is not an ASCII hexadecimal digit"))

"""
bytes2hex(bin_arr::Array{UInt8, 1}) -> String
bytes2hex(a::AbstractArray{UInt8}) -> String
bytes2hex(io::IO, a::AbstractArray{UInt8})

Convert an array `a` of bytes to its hexadecimal string representation, either
returning a `String` via `bytes2hex(a)` or writing the string to an `io` stream
via `bytes2hex(io, a)`. The hexadecimal characters are all lowercase.

Convert an array of bytes to its hexadecimal representation.
All characters are in lower-case.
# Examples
```jldoctest
julia> a = string(12345, base = 16)
Expand All @@ -565,8 +568,10 @@ julia> bytes2hex(b)
"3039"
```
"""
function bytes2hex end

function bytes2hex(a::AbstractArray{UInt8})
b = Vector{UInt8}(undef, 2*length(a))
b = Base.StringVector(2*length(a))
i = 0
for x in a
b[i += 1] = hex_chars[1 + x >> 4]
Expand All @@ -575,6 +580,11 @@ function bytes2hex(a::AbstractArray{UInt8})
return String(b)
end

bytes2hex(io::IO, a::AbstractArray{UInt8}) =
for x in a
print(io, Char(hex_chars[1 + x >> 4]), Char(hex_chars[1 + x & 0xf]))
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write(io, hex_chars[1 + (x >> 4)]) would probably be faster, since it'll save us from needing to decode the Char into the stream

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Faster but wrong, unfortunately. Writing bytes directly assumes that io uses an ASCII-compatible encoding (#26286). We would need an ASCIIChar type to get both encoding-independence and maximum performance here.

end

# check for pure ASCII-ness

function ascii(s::String)
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3 changes: 1 addition & 2 deletions base/uuid.jl
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Expand Up @@ -50,8 +50,7 @@ let groupings = [36:-1:25; 23:-1:20; 18:-1:15; 13:-1:10; 8:-1:1]
u = u.value
a = Base.StringVector(36)
for i in groupings
d = u & 0xf
a[i] = '0' + d + 39*(d > 9)
a[i] = hex_chars[1 + u & 0xf]
u >>= 4
end
a[24] = a[19] = a[14] = a[9] = '-'
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2 changes: 1 addition & 1 deletion test/loading.jl
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Expand Up @@ -96,7 +96,7 @@ end
let uuidstr = "ab"^4 * "-" * "ab"^2 * "-" * "ab"^2 * "-" * "ab"^2 * "-" * "ab"^6
uuid = UUID(uuidstr)
@test uuid == eval(Meta.parse(repr(uuid))) # check show method
@test string(uuid) == uuidstr
@test string(uuid) == uuidstr == sprint(print, uuid)
@test "check $uuid" == "check $uuidstr"
end

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2 changes: 1 addition & 1 deletion test/strings/util.jl
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Expand Up @@ -324,7 +324,7 @@ end
bin_val = hex2bytes(hex_str)

@test div(length(hex_str), 2) == length(bin_val)
@test hex_str == bytes2hex(bin_val)
@test hex_str == bytes2hex(bin_val) == sprint(bytes2hex, bin_val)

bin_val = hex2bytes("07bf")
@test bin_val[1] == 7
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