Reset concurrency to the initial default

lib/vips.rb

@@ -626,6 +626,10 @@ def to_s
   attach_function :vips_leak_set, [:int], :void
   attach_function :vips_vector_set_enabled, [:int], :void
   attach_function :vips_concurrency_set, [:int], :void
+  attach_function :vips_concurrency_get, [], :int
+
+  # Track the original default concurrency so we can reset to it.
+  DEFAULT_CONCURRENCY = vips_concurrency_get
 
   # vips_foreign_get_suffixes was added in libvips 8.8
   begin
@@ -663,10 +667,23 @@ def self.cache_set_max_files size
     vips_cache_set_max_files size
   end
 
-  # Set the size of the libvips worker pool. This defaults to the number of
-  # hardware threads on your computer. Set to 1 to disable threading.
+  # Get the size of libvips worker pools. Defaults to the VIPS_CONCURRENCY env
+  # var or the number of hardware threads on your computer.
+  def self.concurrency
+    vips_concurrency_get
+  end
+
+  # Get the default size of libvips worker pools.
+  def self.concurrency_default
+    DEFAULT_CONCURRENCY
+  end
+
+  # Set the size of each libvips worker pool. Max 1024 threads. Set to 1 to
+  # disable threading. Set to 0 or nil to reset to default.
   def self.concurrency_set n
+    n = DEFAULT_CONCURRENCY if n.to_i == 0
     vips_concurrency_set n
+    concurrency
   end
 
   # Enable or disable SIMD and the run-time compiler. This can give a nice

spec/spec_helper.rb

@@ -1,3 +1,11 @@
+# Set default concurrency so we can check against it later. Must be set
+# before Vips.init sets concurrency to the default.
+DEFAULT_VIPS_CONCURRENCY = 5
+ENV["VIPS_CONCURRENCY"] = DEFAULT_VIPS_CONCURRENCY.to_s
+
+# Disable stderr output since we purposefully trigger warn-able behavior.
+ENV["VIPS_WARNING"] = "1"
+
 require "vips"
 
 require "tempfile"

spec/vips_spec.rb

@@ -2,8 +2,31 @@
 
 RSpec.describe Vips do
   describe "Vips" do
+    it "can get default concurrency" do
+      expect(Vips.concurrency_default).to eq DEFAULT_VIPS_CONCURRENCY
+    end
+
+    it "can get concurrency" do
+      expect(Vips.concurrency).to eq Vips.concurrency_default
+    end
+
     it "can set concurrency" do
-      Vips.concurrency_set 12
+      expect(Vips.concurrency_set(12)).to eq 12
+      expect(Vips.concurrency).to eq 12
+    end
+
+    it "clips concurrency to 1024" do
+      expect(Vips.concurrency_set(1025)).to eq 1024
+    end
+
+    it "can set concurrency to 0 to reset to default" do
+      Vips.concurrency_set(rand(100))
+      expect(Vips.concurrency_set(0)).to eq Vips.concurrency_default
+    end
+
+    it "can set concurrency to nil to reset to default" do
+      Vips.concurrency_set(rand(100))
+      expect(Vips.concurrency_set(nil)).to eq Vips.concurrency_default
     end
 
     it "can set SIMD" do