1 files changed, 63 insertions, 0 deletions
diff --git a/app/services/packages/nuget/symbols/extract_symbol_signature_service.rb b/app/services/packages/nuget/symbols/extract_symbol_signature_service.rb
new file mode 100644
index 00000000000..c2ccdb517b5
--- /dev/null
+++ b/app/services/packages/nuget/symbols/extract_symbol_signature_service.rb
@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+module Packages
+  module Nuget
+    module Symbols
+      class ExtractSymbolSignatureService
+        include Gitlab::Utils::StrongMemoize
+
+        # More information about the GUID format can be found here:
+        # https://github.com/dotnet/symstore/blob/main/docs/specs/SSQP_Key_Conventions.md#key-formatting-basic-rules
+        GUID_START_INDEX = 7
+        GUID_END_INDEX = 22
+        GUID_PARTS_LENGTHS = [4, 2, 2, 8].freeze
+        GUID_AGE_PART = 'FFFFFFFF'
+        TWO_CHARACTER_HEX_REGEX = /\h{2}/
+
+        # The extraction of the signature in this service is based on the following documentation:
+        # https://github.com/dotnet/symstore/blob/main/docs/specs/SSQP_Key_Conventions.md#portable-pdb-signature
+
+        def initialize(symbol_content)
+          @symbol_content = symbol_content
+        end
+
+        def execute
+          return error_response unless signature
+
+          ServiceResponse.success(payload: signature)
+        end
+
+        private
+
+        attr_reader :symbol_content
+
+        def signature
+          # Find the index of the first occurrence of 'Blob'
+          guid_index = symbol_content.index('Blob')
+          return if guid_index.nil?
+
+          # Extract the binary GUID from the symbol content
+          guid = symbol_content[(guid_index + GUID_START_INDEX)..(guid_index + GUID_END_INDEX)]
+          return if guid.nil?
+
+          # Convert the GUID into an array of two-character hex strings
+          guid = guid.unpack('H*').flat_map { |el| el.scan(TWO_CHARACTER_HEX_REGEX) }
+
+          # Reorder the GUID parts based on arbitrary lengths
+          guid = GUID_PARTS_LENGTHS.map { |length| guid.shift(length) }
+
+          # Concatenate the parts of the GUID back together
+          result = guid.first(3).map(&:reverse)
+          result << guid.last
+          result = result.join
+          result << GUID_AGE_PART
+        end
+        strong_memoize_attr :signature
+
+        def error_response
+          ServiceResponse.error(message: 'Could not find the signature in the symbol file')
+        end
+      end
+    end
+  end
+end