105 lines
2.6 KiB
Ruby
105 lines
2.6 KiB
Ruby
# frozen_string_literal: true
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module Gitlab
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module Utils
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# This class estimates the JSON blob byte size of a ruby object using as
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# little allocations as possible.
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# The estimation should be quite accurate when using simple objects.
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#
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# Example:
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#
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# Gitlab::Utils::JsonSizeEstimator.estimate(["a", { b: 12, c: nil }])
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class JsonSizeEstimator
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ARRAY_BRACKETS_SIZE = 2 # []
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OBJECT_BRACKETS_SIZE = 2 # {}
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DOUBLEQUOTE_SIZE = 2 # ""
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COLON_SIZE = 1 # : character size from {"a": 1}
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MINUS_SIGN_SIZE = 1 # - character size from -1
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NULL_SIZE = 4 # null
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class << self
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# Returns: integer (number of bytes)
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def estimate(object)
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case object
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when Hash
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estimate_hash(object)
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when Array
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estimate_array(object)
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when String
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estimate_string(object)
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when Integer
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estimate_integer(object)
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when Float
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estimate_float(object)
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when DateTime, Time
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estimate_time(object)
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when NilClass
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NULL_SIZE
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else
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# might be incorrect, but #to_s is safe, #to_json might be disabled for some objects: User
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estimate_string(object.to_s)
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end
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end
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private
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def estimate_hash(hash)
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size = 0
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item_count = 0
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hash.each do |key, value|
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item_count += 1
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size += estimate(key.to_s) + COLON_SIZE + estimate(value)
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end
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size + OBJECT_BRACKETS_SIZE + comma_count(item_count)
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end
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def estimate_array(array)
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size = 0
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item_count = 0
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array.each do |item|
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item_count += 1
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size += estimate(item)
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end
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size + ARRAY_BRACKETS_SIZE + comma_count(item_count)
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end
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def estimate_string(string)
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string.bytesize + DOUBLEQUOTE_SIZE
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end
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def estimate_float(float)
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float.to_s.bytesize
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end
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def estimate_integer(integer)
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if integer > 0
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integer_string_size(integer)
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elsif integer < 0
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integer_string_size(integer.abs) + MINUS_SIGN_SIZE
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else # 0
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1
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end
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end
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def estimate_time(time)
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time.to_json.size
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end
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def integer_string_size(integer)
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Math.log10(integer).floor + 1
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end
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def comma_count(item_count)
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item_count == 0 ? 0 : item_count - 1
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end
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end
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end
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end
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end
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