From 692b2cda6af27072ff7d58897e7c01fec527f250 Mon Sep 17 00:00:00 2001
From: Paul Fd <paul@ferrand.cc>
Date: Thu, 5 Mar 2020 16:07:23 +0100
Subject: [PATCH] Silently ignore ampersands in opcode name

---
 src/sfizz/Opcode.cpp          |  4 ++--
 src/sfizz/StringViewHelpers.h | 21 +++++++++++++++++++++
 tests/OpcodeT.cpp             | 28 ++++++++++++++++++++++++++++
 3 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/src/sfizz/Opcode.cpp b/src/sfizz/Opcode.cpp
index 344c31e9..cc022c11 100644
--- a/src/sfizz/Opcode.cpp
+++ b/src/sfizz/Opcode.cpp
@@ -20,7 +20,7 @@ sfz::Opcode::Opcode(absl::string_view inputOpcode, absl::string_view inputValue)
     while (nextNumIndex != opcode.npos) {
         const auto numLetters = nextNumIndex - nextCharIndex;
         parameterPosition += numLetters;
-        lettersOnlyHash = hash(opcode.substr(nextCharIndex, numLetters), lettersOnlyHash);
+        lettersOnlyHash = hashNoAmpersand(opcode.substr(nextCharIndex, numLetters), lettersOnlyHash);
         nextCharIndex = opcode.find_first_not_of("1234567890", nextNumIndex);
 
         uint32_t returnedValue;
@@ -34,5 +34,5 @@ sfz::Opcode::Opcode(absl::string_view inputOpcode, absl::string_view inputValue)
     }
 
     if (nextCharIndex != opcode.npos)
-        lettersOnlyHash = hash(opcode.substr(nextCharIndex), lettersOnlyHash);
+        lettersOnlyHash = hashNoAmpersand(opcode.substr(nextCharIndex), lettersOnlyHash);
 }
diff --git a/src/sfizz/StringViewHelpers.h b/src/sfizz/StringViewHelpers.h
index 0cc49d38..aeb2f2bd 100644
--- a/src/sfizz/StringViewHelpers.h
+++ b/src/sfizz/StringViewHelpers.h
@@ -66,3 +66,24 @@ constexpr uint64_t hash(absl::string_view s, uint64_t h = Fnv1aBasis)
 
     return h;
 }
+
+/**
+ * @brief Same function as `hash()` but ignores ampersands (&)
+ *
+ * See e.g. the Region.cpp file
+ *
+ * @param s the input string to be hashed
+ * @param h the hashing seed to use
+ * @return uint64_t
+ */
+constexpr uint64_t hashNoAmpersand(absl::string_view s, uint64_t h = Fnv1aBasis)
+{
+    if (s.length() > 0) {
+        if (s.front() == '&')
+            return hashNoAmpersand( { s.data() + 1, s.length() - 1 }, h );
+        else
+            return hashNoAmpersand( { s.data() + 1, s.length() - 1 }, (h ^ s.front()) * Fnv1aPrime );
+    }
+
+    return h;
+}
diff --git a/tests/OpcodeT.cpp b/tests/OpcodeT.cpp
index d55d7aff..ffbb07ab 100644
--- a/tests/OpcodeT.cpp
+++ b/tests/OpcodeT.cpp
@@ -28,6 +28,24 @@ TEST_CASE("[Opcode] Construction")
         REQUIRE(opcode.value == "dummy");
     }
 
+    SECTION("Normal construction with ampersand")
+    {
+        sfz::Opcode opcode { "sample&_ampersand", "dummy" };
+        REQUIRE(opcode.opcode == "sample&_ampersand");
+        REQUIRE(opcode.lettersOnlyHash == hash("sample_ampersand"));
+        REQUIRE(opcode.parameters.empty());
+        REQUIRE(opcode.value == "dummy");
+    }
+
+    SECTION("Normal construction with multiple ampersands")
+    {
+        sfz::Opcode opcode { "&sample&_ampersand&", "dummy" };
+        REQUIRE(opcode.opcode == "&sample&_ampersand&");
+        REQUIRE(opcode.lettersOnlyHash == hash("sample_ampersand"));
+        REQUIRE(opcode.parameters.empty());
+        REQUIRE(opcode.value == "dummy");
+    }
+
     SECTION("Parameterized opcode")
     {
         sfz::Opcode opcode { "sample123", "dummy" };
@@ -38,6 +56,16 @@ TEST_CASE("[Opcode] Construction")
         REQUIRE(opcode.parameters == std::vector<uint16_t>({ 123 }));
     }
 
+    SECTION("Parameterized opcode with ampersand")
+    {
+        sfz::Opcode opcode { "sample&123", "dummy" };
+        REQUIRE(opcode.opcode == "sample&123");
+        REQUIRE(opcode.lettersOnlyHash == hash("sample&"));
+        REQUIRE(opcode.value == "dummy");
+        REQUIRE(opcode.parameters.size() == 1);
+        REQUIRE(opcode.parameters == std::vector<uint16_t>({ 123 }));
+    }
+
     SECTION("Parameterized opcode with underscore")
     {
         sfz::Opcode opcode { "sample_underscore123", "dummy" };