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require "benchmark" | |
struct Int | |
DIGITS = | |
"0001020304050607080910111213141516171819" \ | |
"2021222324252627282930313233343536373839" \ | |
"4041424344454647484950515253545556575859" \ | |
"6061626364656667686970717273747576777879" \ | |
"8081828384858687888990919293949596979899" | |
def fast_to_s(base : Int = 10, *, upcase : Bool = false) : String | |
raise ArgumentError.new("Invalid base #{base}") unless 2 <= base <= 36 || base == 62 | |
raise ArgumentError.new("upcase must be false for base 62") if upcase && base == 62 | |
case self | |
when 0 | |
"0" | |
when 1 | |
"1" | |
else | |
fast_internal_to_s(base, upcase) do |ptr, count| | |
String.new(ptr, count, count) | |
end | |
end | |
end | |
def fast_to_s(io : IO, base : Int = 10, *, upcase : Bool = false) : Nil | |
raise ArgumentError.new("Invalid base #{base}") unless 2 <= base <= 36 || base == 62 | |
raise ArgumentError.new("upcase must be false for base 62") if upcase && base == 62 | |
case self | |
when 0 | |
io << '0' | |
when 1 | |
io << '1' | |
else | |
fast_internal_to_s(base, upcase) do |ptr, count| | |
io.write_utf8 Slice.new(ptr, count) | |
end | |
end | |
end | |
private def fast_internal_to_s(base, upcase = false) | |
# Given sizeof(self) <= 128 bits, we need at most 128 bytes for a base 2 | |
# representation, plus one byte for the trailing 0. | |
chars = uninitialized UInt8[129] | |
ptr_end = chars.to_unsafe + 128 | |
ptr = ptr_end | |
num = self | |
neg = num < 0 | |
if base == 10 | |
digits = DIGITS.to_unsafe | |
while num >= 100 || num <= -100 | |
ptr -= 2 | |
ptr.copy_from(digits + num.remainder(100).abs &* 2, 2) | |
num = num.tdiv(100) | |
end | |
if num >= 10 || num <= -10 | |
ptr -= 2 | |
ptr.copy_from(digits + num.abs &* 2, 2) | |
elsif num != 0 | |
ptr -= 1 | |
ptr.value = 0x30u8 &+ num.abs | |
end | |
else | |
digits = (base == 62 ? DIGITS_BASE62 : (upcase ? DIGITS_UPCASE : DIGITS_DOWNCASE)).to_unsafe | |
while num != 0 | |
ptr -= 1 | |
ptr.value = digits[num.remainder(base).abs] | |
num = num.tdiv(base) | |
end | |
end | |
if neg | |
ptr -= 1 | |
ptr.value = '-'.ord.to_u8 | |
end | |
count = (ptr_end - ptr).to_i32 | |
yield ptr, count | |
end | |
end | |
Benchmark.ips do |x| | |
x.report("to_s") do | |
1000.times { |i| (i * 123).to_s } | |
end | |
x.report("fast_to_s") do | |
1000.times { |i| (i * 123).fast_to_s } | |
end | |
end |
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