From ecc6a8679b1dda4cd7a9b70ae3ead8b13e17c5b7 Mon Sep 17 00:00:00 2001
From: Alexander Batalov <alex.batalov@gmail.com>
Date: Thu, 20 Apr 2023 09:53:50 +0300
Subject: [PATCH] Add math opcodes

---
 src/interpreter.cc   | 25 ++++++++++++++++
 src/interpreter.h    |  3 ++
 src/sfall_opcodes.cc | 69 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 97 insertions(+)

diff --git a/src/interpreter.cc b/src/interpreter.cc
index 8729fd5..23793ac 100644
--- a/src/interpreter.cc
+++ b/src/interpreter.cc
@@ -3268,4 +3268,29 @@ bool ProgramValue::isEmpty()
     return true;
 }
 
+// Matches Sfall implementation.
+bool ProgramValue::isInt()
+{
+    return opcode == VALUE_TYPE_INT;
+}
+
+// Matches Sfall implementation.
+bool ProgramValue::isFloat()
+{
+    return opcode == VALUE_TYPE_FLOAT;
+}
+
+// Matches Sfall implementation.
+float ProgramValue::asFloat()
+{
+    switch (opcode) {
+    case VALUE_TYPE_INT:
+        return static_cast<float>(integerValue);
+    case VALUE_TYPE_FLOAT:
+        return floatValue;
+    default:
+        return 0.0;
+    }
+}
+
 } // namespace fallout
diff --git a/src/interpreter.h b/src/interpreter.h
index 91d27bb..f84347f 100644
--- a/src/interpreter.h
+++ b/src/interpreter.h
@@ -149,6 +149,9 @@ typedef struct ProgramValue {
     };
 
     bool isEmpty();
+    bool isInt();
+    bool isFloat();
+    float asFloat();
 } ProgramValue;
 
 typedef std::vector<ProgramValue> ProgramStack;
diff --git a/src/sfall_opcodes.cc b/src/sfall_opcodes.cc
index bef609d..dd1580c 100644
--- a/src/sfall_opcodes.cc
+++ b/src/sfall_opcodes.cc
@@ -175,6 +175,25 @@ static void op_set_bodypart_hit_modifier(Program* program)
     combat_set_hit_location_penalty(hit_location, penalty);
 }
 
+// sqrt
+static void op_sqrt(Program* program)
+{
+    ProgramValue programValue = programStackPopValue(program);
+    programStackPushFloat(program, sqrtf(programValue.asFloat()));
+}
+
+// abs
+static void op_abs(Program* program)
+{
+    ProgramValue programValue = programStackPopValue(program);
+
+    if (programValue.isInt()) {
+        programStackPushInteger(program, abs(programValue.integerValue));
+    } else {
+        programStackPushFloat(program, abs(programValue.asFloat()));
+    }
+}
+
 // get_proto_data
 static void op_get_proto_data(Program* program)
 {
@@ -395,6 +414,13 @@ static void opParseInt(Program* program)
     programStackPushInteger(program, static_cast<int>(strtol(string, nullptr, 0)));
 }
 
+// atof
+static void op_atof(Program* program)
+{
+    const char* string = programStackPopString(program);
+    programStackPushFloat(program, static_cast<float>(atof(string)));
+}
+
 // strlen
 static void opGetStringLength(Program* program)
 {
@@ -402,6 +428,22 @@ static void opGetStringLength(Program* program)
     programStackPushInteger(program, static_cast<int>(strlen(string)));
 }
 
+// pow (^)
+static void op_power(Program* program)
+{
+    ProgramValue expValue = programStackPopValue(program);
+    ProgramValue baseValue = programStackPopValue(program);
+
+    // CE: Implementation is slightly different, check.
+    float result = powf(baseValue.asFloat(), expValue.asFloat());
+
+    if (baseValue.isInt() && expValue.isInt()) {
+        programStackPushInteger(program, static_cast<int>(result));
+    } else {
+        programStackPushFloat(program, result);
+    }
+}
+
 // message_str_game
 static void opGetMessage(Program* program)
 {
@@ -430,6 +472,28 @@ static void opArtExists(Program* program)
     programStackPushInteger(program, artExists(fid));
 }
 
+// div (/)
+static void op_div(Program* program)
+{
+    ProgramValue divisorValue = programStackPopValue(program);
+    ProgramValue dividendValue = programStackPopValue(program);
+
+    if (divisorValue.integerValue == 0) {
+        debugPrint("Division by zero");
+
+        // TODO: Looks like execution is not halted in Sfall's div, check.
+        programStackPushInteger(program, 0);
+        return;
+    }
+
+    if (dividendValue.isFloat() || divisorValue.isFloat()) {
+        programStackPushFloat(program, dividendValue.asFloat() / divisorValue.asFloat());
+    } else {
+        // Unsigned divison.
+        programStackPushInteger(program, static_cast<unsigned int>(dividendValue.integerValue) / static_cast<unsigned int>(divisorValue.integerValue));
+    }
+}
+
 void sfallOpcodesInit()
 {
     interpreterRegisterOpcode(0x8156, opReadByte);
@@ -448,6 +512,8 @@ void sfallOpcodesInit()
     interpreterRegisterOpcode(0x81B6, op_set_car_current_town);
     interpreterRegisterOpcode(0x81DF, op_get_bodypart_hit_modifier);
     interpreterRegisterOpcode(0x81E0, op_set_bodypart_hit_modifier);
+    interpreterRegisterOpcode(0x81EC, op_sqrt);
+    interpreterRegisterOpcode(0x81ED, op_abs);
     interpreterRegisterOpcode(0x8204, op_get_proto_data);
     interpreterRegisterOpcode(0x8205, op_set_proto_data);
     interpreterRegisterOpcode(0x820D, opListBegin);
@@ -465,10 +531,13 @@ void sfallOpcodesInit()
     interpreterRegisterOpcode(0x8220, opGetScreenWidth);
     interpreterRegisterOpcode(0x8221, opGetScreenHeight);
     interpreterRegisterOpcode(0x8237, opParseInt);
+    interpreterRegisterOpcode(0x8238, op_atof);
     interpreterRegisterOpcode(0x824F, opGetStringLength);
+    interpreterRegisterOpcode(0x8263, op_power);
     interpreterRegisterOpcode(0x826B, opGetMessage);
     interpreterRegisterOpcode(0x8267, opRound);
     interpreterRegisterOpcode(0x8274, opArtExists);
+    interpreterRegisterOpcode(0x827F, op_div);
 }
 
 void sfallOpcodesExit()