Add more examples

.gitignore

@@ -4,3 +4,6 @@
 # Ignore Vim swap files
 *.swp
 
+# Ignore data files
+*.csv
+

003_wrapper_ex.rb

@@ -0,0 +1,16 @@
+require 'wrapper'
+require 'csv'
+
+measure do
+  data = CSV.open('003_10mb.csv')
+  output = data.readlines.map do |line|
+    line.map do |col|
+      col.downcase.gsub(/\b('?[a-z])/) { $1.capitalize }
+    end
+  end
+
+  File.open('003_10mb_output.csv', 'w+') do |file|
+    file.write output.join('\n')
+  end
+end
+

004_array_bang.rb

@@ -0,0 +1,12 @@
+require 'wrapper'
+
+data = Array.new(100) { 'x' * 1024 * 1024 } # 100 Mb
+
+measure do
+  data.map { |str| str.upcase }
+end
+
+measure do
+  data.map! { |str| str.upcase! }
+end
+

004_string_bang.rb

@@ -0,0 +1,12 @@
+require 'wrapper'
+
+str = 'X' * 1024 * 1024 * 10 # 10Mb string
+
+measure do
+  str = str.downcase
+end
+
+measure do
+  str = str.downcase!
+end
+

005_files.rb

@@ -0,0 +1,36 @@
+require 'wrapper'
+require 'csv'
+
+puts 'Just read file in memory:'
+measure do
+  File.read('003_10mb.csv')
+end
+
+puts 'Read file and manipulate string:'
+measure do
+  File.readlines('003_10mb.csv').map! do |line|
+    line.split(',')
+  end
+end
+
+puts 'Just read file in memory with CSV lib:'
+measure do
+  CSV.read('003_10mb.csv')
+end
+
+puts 'Read file line by line:'
+measure do
+  file = File.open('003_10mb.csv', 'r')
+  while line = file.gets
+    line.split(',')
+  end
+end
+
+puts 'Read file line by line with CSV lib:'
+measure do
+  file = CSV.open('003_10mb.csv')
+  while line = file.readline
+    line
+  end
+end
+

README.md

@@ -15,3 +15,17 @@ See [001_gc.rb].
 
 See [002_memory.rb]
 
+GC::Profiler has memory and CPU overhead (See [wrapper.rb] for custom wrapper example).
+
+Save memory by avoiding copiyng objects, modify them in place if it is possible (use ! methods).
+
+See [004_string_bang.rb]
+
+If your String is less than 40 bytes - user '<<', not '+=' method to concatenate it and Ruby will not allocate additional object.
+
+See [004_array_bang.rb] (w/ GC)
+
+Read files line by line. And keep in mind not only total memory consumption but also peaks.
+
+See [005_files.rb] (w/ and w/o GC)
+

wrapper.rb

@@ -0,0 +1,39 @@
+require 'json'
+require 'benchmark'
+require 'ap'
+
+def measure(&block)
+  no_gc = (ARGV[0] == '--no-gc')
+
+  if no_gc
+    GC.disable
+  else
+    GC.start
+  end
+
+  memory_before = `ps -o rss= -p #{Process.pid}`.to_i/1024
+  gc_stats_before = GC.stat
+
+  time = Benchmark.realtime do
+    yield
+  end
+
+  puts "Objects: #{ObjectSpace.count_objects}"
+  unless no_gc
+    GC.start(full_mark: true, immediate_sweep: true, immediate_mark: false)
+    puts "Objects after GC: #{ObjectSpace.count_objects}"
+  end
+
+  gc_stats_after = GC.stat
+  memory_after = `ps -o rss= -p #{Process.pid}`.to_i/1024
+
+  ap({
+    RUBY_VERSION => {
+      gc: no_gc ? 'disabled' : 'enabled',
+      time: time.round(2),
+      gc_count: gc_stats_after[:count] - gc_stats_before[:count],
+      memory: "%d MB" % (memory_after - memory_before)
+    }
+  })
+end
+