Fix JuliaLang#14341, rewrite bytes2hex to be more efficient

Add hex(x::Vector{UInt8}) & hex(x::ByteString)

base/floatfuncs.jl

@@ -26,16 +26,16 @@ maxintfloat() = maxintfloat(Float64)
 
 isinteger(x::AbstractFloat) = (trunc(x)==x)&isfinite(x)
 
-num2hex(x::Float16) = hex(reinterpret(UInt16,x), 4)
-num2hex(x::Float32) = hex(box(UInt32,unbox(Float32,x)),8)
-num2hex(x::Float64) = hex(box(UInt64,unbox(Float64,x)),16)
+hex(x::Float16) = hex(reinterpret(UInt16,x), 4)
+hex(x::Float32) = hex(box(UInt32,unbox(Float32,x)),8)
+hex(x::Float64) = hex(box(UInt64,unbox(Float64,x)),16)
 
-function hex2num(s::AbstractString)
-    if length(s) <= 8
-        return box(Float32,unbox(UInt32,parse(UInt32,s,16)))
-    end
-    return box(Float64,unbox(UInt64,parse(UInt64,s,16)))
-end
+num2hex{T<:Union{Float16, Float32, Float64}}(x::T) = hex(x)
+
+hex2num(s::AbstractString) =
+    (length(s) <= 8
+     ? box(Float32,unbox(UInt32,parse(UInt32,s,16)))
+     : box(Float64,unbox(UInt64,parse(UInt64,s,16))))
 
 @vectorize_1arg Number abs
 @vectorize_1arg Number abs2

base/intfuncs.jl

@@ -267,7 +267,7 @@ function hex(x::Unsigned, pad::Int, neg::Bool)
         x >>= 4
         i -= 1
     end
-    if neg; a[1]='-'; end
+    neg && (a[1] = '-')
     ASCIIString(a)
 end
 

base/strings/util.jl

@@ -234,4 +234,19 @@ function hex2bytes(s::AbstractString)
     return a
 end
 
-bytes2hex(arr::Vector{UInt8}) = join([hex(i,2) for i in arr])
+function hex(arr::Vector{UInt8})
+    out = Vector{UInt8}(sizeof(arr)<<1)
+    o = 0
+    for i = 1:sizeof(arr)
+        v = arr[i]
+        d = v>>4
+        out[o += 1] = ('0' + d + 39 * (d > 9))
+        d = v & 0xf
+        out[o += 1] = ('0' + d + 39 * (d > 9))
+    end
+    ASCIIString(out)
+end
+
+hex(str::ByteString) = hex(str.data)
+
+bytes2hex(arr::Vector{UInt8}) = hex(arr)