1 files changed, 40 insertions, 0 deletions
diff --git a/lib/gitlab/ci/config/interpolation/functions/truncate.rb b/lib/gitlab/ci/config/interpolation/functions/truncate.rb
new file mode 100644
index 00000000000..3771756ba48
--- /dev/null
+++ b/lib/gitlab/ci/config/interpolation/functions/truncate.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    class Config
+      module Interpolation
+        module Functions
+          class Truncate < Base
+            def self.function_expression_pattern
+              /^#{name}\(\s*(?<offset>\d+)\s*,\s*(?<length>\d+)\s*\)?$/
+            end
+
+            def self.name
+              'truncate'
+            end
+
+            def execute(input_value)
+              if input_value.is_a?(String)
+                input_value[offset, length].to_s
+              else
+                error('invalid input type: truncate can only be used with string inputs')
+                nil
+              end
+            end
+
+            private
+
+            def offset
+              function_args[:offset].to_i
+            end
+
+            def length
+              function_args[:length].to_i
+            end
+          end
+        end
+      end
+    end
+  end
+end