show(io, float) optimization

base/ryu/Ryu.jl

@@ -1,6 +1,7 @@
 module Ryu
 
 import .Base: significand_bits, significand_mask, exponent_bits, exponent_mask, exponent_bias, exponent_max, uinttype
+import .Base: with_scratch
 
 include("utils.jl")
 include("shortest.jl")
@@ -45,9 +46,10 @@ function writeshortest(x::T,
         decchar::UInt8=UInt8('.'),
         typed::Bool=false,
         compact::Bool=false) where {T <: Base.IEEEFloat}
-    buf = Base.StringVector(neededdigits(T))
-    pos = writeshortest(buf, 1, x, plus, space, hash, precision, expchar, padexp, decchar, typed, compact)
-    return String(resize!(buf, pos - 1))
+    with_scratch(neededdigits(T)) do buf
+        pos = writeshortest(buf, 1, x, plus, space, hash, precision, expchar, padexp, decchar, typed, compact)
+        return String(@inbounds view(buf, 1:pos - 1))
+    end
 end
 
 """
@@ -73,9 +75,10 @@ function writefixed(x::T,
     hash::Bool=false,
     decchar::UInt8=UInt8('.'),
     trimtrailingzeros::Bool=false) where {T <: Base.IEEEFloat}
-    buf = Base.StringVector(precision + neededdigits(T))
-    pos = writefixed(buf, 1, x, precision, plus, space, hash, decchar, trimtrailingzeros)
-    return String(resize!(buf, pos - 1))
+    with_scratch(precision + neededdigits(T)) do buf
+        pos = writefixed(buf, 1, x, precision, plus, space, hash, decchar, trimtrailingzeros)
+        return String(@inbounds view(buf, 1:pos - 1))
+    end
 end
 
 """
@@ -103,26 +106,29 @@ function writeexp(x::T,
     expchar::UInt8=UInt8('e'),
     decchar::UInt8=UInt8('.'),
     trimtrailingzeros::Bool=false) where {T <: Base.IEEEFloat}
-    buf = Base.StringVector(precision + neededdigits(T))
-    pos = writeexp(buf, 1, x, precision, plus, space, hash, expchar, decchar, trimtrailingzeros)
-    return String(resize!(buf, pos - 1))
+    with_scratch(precision + neededdigits(T)) do buf
+        pos = writeexp(buf, 1, x, precision, plus, space, hash, expchar, decchar, trimtrailingzeros)
+        return String(@inbounds view(buf, 1:pos - 1))
+    end
 end
 
 function Base.show(io::IO, x::T, forceuntyped::Bool=false, fromprint::Bool=false) where {T <: Base.IEEEFloat}
     compact = get(io, :compact, false)::Bool
-    buf = Base.StringVector(neededdigits(T))
-    typed = !forceuntyped && !compact && get(io, :typeinfo, Any) != typeof(x)
-    pos = writeshortest(buf, 1, x, false, false, true, -1,
-        (x isa Float32 && !fromprint) ? UInt8('f') : UInt8('e'), false, UInt8('.'), typed, compact)
-    write(io, resize!(buf, pos - 1))
-    return
+    with_scratch(neededdigits(T)) do buf
+        typed = !forceuntyped && !compact && get(io, :typeinfo, Any) != typeof(x)
+        pos = writeshortest(buf, 1, x, false, false, true, -1,
+            (x isa Float32 && !fromprint) ? UInt8('f') : UInt8('e'), false, UInt8('.'), typed, compact)
+        write(io, @inbounds view(buf, 1:pos - 1))
+        return
+    end
 end
 
 function Base.string(x::T) where {T <: Base.IEEEFloat}
-    buf = Base.StringVector(neededdigits(T))
-    pos = writeshortest(buf, 1, x, false, false, true, -1,
-        UInt8('e'), false, UInt8('.'), false, false)
-    return String(resize!(buf, pos - 1))
+    with_scratch(neededdigits(T)) do buf
+        pos = writeshortest(buf, 1, x, false, false, true, -1,
+            UInt8('e'), false, UInt8('.'), false, false)
+        return String(@inbounds view(buf, 1:pos - 1))
+    end
 end
 
 Base.print(io::IO, x::Union{Float16, Float32}) = show(io, x, true, true)

base/ryu/shortest.jl

@@ -224,7 +224,7 @@ integer. If a `maxsignif` argument is provided, then `b < maxsignif`.
     return b, e10
 end
 
-function writeshortest(buf::Vector{UInt8}, pos, x::T,
+function writeshortest(buf, pos, x::T,
                        plus=false, space=false, hash=true,
                        precision=-1, expchar=UInt8('e'), padexp=false, decchar=UInt8('.'),
                        typed=false, compact=false) where {T}

base/scratch.jl

@@ -1,4 +1,5 @@
-const PRINT_SCRATCH_LENGTH = 256
+# NOTE: ryu/Ryu.jl: neededdigits(::Type{Float64}) = 309 + 17
+const PRINT_SCRATCH_LENGTH = 309 + 17
 struct ScratchBuf
     data::NTuple{PRINT_SCRATCH_LENGTH,UInt8}
 
@@ -11,16 +12,45 @@ struct Scratch
 end
 
 function with_scratch(f, n)
-    buf = Ref(ScratchBuf(undef))
-    GC.@preserve buf f(Scratch(pointer_from_objref(buf), unsafe_trunc(UInt64, n)))
+    if n <= PRINT_SCRATCH_LENGTH
+        buf = Ref(ScratchBuf(undef))
+        GC.@preserve buf f(Scratch(pointer_from_objref(buf), unsafe_trunc(UInt64, n)))
+    else
+        tls = task_local_storage()
+        buf = get!(tls, :PRINT_SCRATCH) do
+            Vector{UInt8}(undef, n)
+        end::Vector{UInt8}
+        resize!(buf, n)
+        GC.@preserve buf f(Scratch(pointer(buf), length(buf)))
+    end
 end
 
 @propagate_inbounds function setindex!(a::Scratch, v, i)
-    @boundscheck (i <= a.length || throw(BoundsError(a, i)))
+    @boundscheck (1 <= i <= a.length || throw(BoundsError(a, i)))
     unsafe_store!(a.p, convert(UInt8, v), i)
     a
 end
 
+@propagate_inbounds function getindex(a::Scratch, i)
+    @boundscheck (1 <= i <= a.length || throw(BoundsError(a, i)))
+    unsafe_load(a.p, i)
+end
+
+@propagate_inbounds function view(a::Scratch, index::UnitRange)
+    @boundscheck ((index.start > 0 && index.stop <= a.length) || throw(BoundsError))
+    index.start > index.stop && return Scratch(Ptr{UInt8}(), 0)
+    Scratch(a.p + index.start - 1, unsafe_trunc(UInt64, index.stop - index.start + 1))
+end
+
+pointer(a::Scratch) = a.p
+pointer(a::Scratch, pos) = a.p + pos - 1
+length(a::Scratch) = a.length
+@inline function unsafe_copyto!(dst::Scratch, dst_pos, src::Vector{UInt8}, src_pos, N)
+    GC.@preserve dst, src, begin
+        unsafe_copyto!(pointer(dst, dst_pos), pointer(src, src_pos), N)
+    end
+end
+
 write(io::IO, a::Scratch) = unsafe_write(io, a.p, a.length)
 
 String(s::Scratch) = unsafe_string(s.p, s.length)