`class Cache`

Cache for storing and looking up allocation metadata. Caches gem names, file locations, class names, and string values to reduce memory overhead during profiling.

Definitions

`def initialize`

Initialize a new cache with empty lookup tables.

Implementation

def initialize
	@gem_guess_cache = Hash.new
	@location_cache = Hash.new{|h, k| h[k] = Hash.new.compare_by_identity}
	@class_name_cache = Hash.new.compare_by_identity
	@string_cache = Hash.new
end

`def guess_gem(path)`

Guess the gem or library name from a file path.

Signature

parameter　path　String: The file path to analyze.
returns　String: The guessed gem name, stdlib component, or "other".

Implementation

def guess_gem(path)
	@gem_guess_cache[path] ||=
		if /(\/gems\/.*)*\/gems\/(?<gemname>[^\/]+)/ =~ path
			gemname
		elsif /\/rubygems[\.\/]/ =~ path
			"rubygems"
		elsif /ruby\/2\.[^\/]+\/(?<stdlib>[^\/\.]+)/ =~ path
			stdlib
		elsif /(?<app>[^\/]+\/(bin|app|lib))/ =~ path
			app
		else
			"other"
		end
end

`def lookup_location(file, line)`

Look up and cache a file location string.

Signature

parameter　file　String: The source file path.
parameter　line　Integer: The line number.
returns　String: The formatted location string "file:line".

Implementation

def lookup_location(file, line)
	@location_cache[file][line] ||= "#{file}:#{line}"
end

`def lookup_class_name(klass)`

Look up and cache a class name.

Signature

parameter　klass　Class: The class object.
returns　String: The class name or unknown if unavailable.

Implementation

def lookup_class_name(klass)
	@class_name_cache[klass] ||= ((klass.is_a?(Class) && klass.name) || "unknown").to_s
end

`def lookup_string(obj)`

Look up and cache a string value.

This maps the original string to a shortened representation.

Strings are truncated to 64 characters to reduce memory usage.

Signature

parameter　obj　String: The string object to cache.
returns　String: A cached copy of the string (truncated to 64 characters).

Implementation

def lookup_string(obj)
	# This string is shortened to 64 characters which is what the string report shows. The string report (by value) can still list unique strings longer than 64 characters separately because the `object_id` of the shortened string will be different.
	@string_cache[obj] ||= obj[0, 64]
rescue RuntimeError => error
	# It is possible for the String to be temporarily locked from another Fiber which raises an error when we try to use it as a hash key. i.e: `Socket#read` locks a buffer string while reading data into it. In this case we `#dup`` the string to get an unlocked copy.
	if error.message == "can't modify string; temporarily locked"
		@string_cache[obj.dup] ||= obj[0, 64]
	else
		raise
	end
end