[pcr] address checks in Program counter

src/emu/mod.rs

@@ -2,4 +2,4 @@ pub mod cpu;
 pub mod mmu;
 pub mod ram;
 pub mod iomem;
-mod program_counter;
+pub mod program_counter;

src/emu/program_counter.rs

@@ -1,27 +1,37 @@
-use crate::emu::mmu::Memory;
+use crate::emu::mmu::{Memory, RAM_MEM_END};
 use crate::misc::emulator_error::DeviceType::PC;
 use crate::misc::emulator_error::EmulatorError;
 use crate::misc::endian::{read_big_endian_u24, write_big_endian_u24};
 use crate::misc::result::EmulatorResult;
 
 
-#[derive(Debug,Default, Copy, Clone)]
+#[derive(Debug, Default, Copy, Clone)]
 pub struct ProgramCounter {
     /// 24bit location register
     program_counter_register: [u8; 3],
 }
 
 impl ProgramCounter {
+    pub fn new() -> ProgramCounter {
+        ProgramCounter {
+            program_counter_register: [0; 3]
+        }
+    }
     // get the current program counter as an address
     pub fn get_pc_value(&self) -> u32 {
         read_big_endian_u24(&self.program_counter_register)
     }
     // assign a value of PC to start execution
-    pub fn set_address(&mut self, address: u32) {
+    pub fn set_address(&mut self, address: u32) -> EmulatorResult<()> {
         log::debug!("Setting PC as {}",address);
-        write_big_endian_u24(address, &mut self.program_counter_register)
+        if address >= (2 << 24) {
+            return Err(EmulatorError::UnreachableMemory(PC, address));
+        }
+        write_big_endian_u24(address, &mut self.program_counter_register);
+        Ok(())
     }
 }
+
 /// Allow Using Program counter as mapped memory
 impl Memory for ProgramCounter {
     fn try_get_byte(&self, address: u32) -> EmulatorResult<u8> {
@@ -35,4 +45,27 @@ impl Memory for ProgramCounter {
         log::error!("Unsupported Method!");
         todo!()
     }
+}
+
+
+#[cfg(test)]
+mod test {
+    use crate::emu::program_counter::ProgramCounter;
+
+    #[test]
+    pub fn setting_address_works() {
+        const ADDRESS: u32 = 4;
+        let mut pc = ProgramCounter::new();
+        let res = pc.set_address(ADDRESS);
+        assert!(res.is_ok());
+        assert_eq!(ADDRESS, pc.get_pc_value());
+    }
+
+    #[test]
+    pub fn set_invalid_addr_returns_error() {
+        const ADDRESS: u32 = 2 << 24;
+        let mut pc = ProgramCounter::new();
+        let res = pc.set_address(ADDRESS);
+        assert!(res.is_err());
+    }
 }

src/main.rs

@@ -2,7 +2,8 @@ use simple_logger::SimpleLogger;
 use crate::emu::iomem::MemoryMappedIO;
 use crate::emu::ram::RamMemory;
 use crate::emu::mmu::{Memory, MappedMemory};
-use crate::misc::emulator_error::EmulatorError;
+use crate::emu::program_counter::ProgramCounter;
+
 use crate::misc::result::EmulatorResult;
 
 mod emu;
@@ -12,8 +13,8 @@ mod graphics;
 
 fn main() -> EmulatorResult<()> {
     SimpleLogger::new().env().init().unwrap();
-
-    let mmio = MemoryMappedIO::new();
+    let program_counter = ProgramCounter::new();
+    let mmio = MemoryMappedIO::new(program_counter);
     let ram = RamMemory::try_new()?;
     let mmu = MappedMemory::new(mmio, ram);
     for i in 0..10 {