1 files changed, 112 insertions, 0 deletions
diff --git a/pyscv/memory.py b/pyscv/memory.py
new file mode 100644
index 0000000..84bf0bd
--- /dev/null
+++ b/pyscv/memory.py
@@ -0,0 +1,112 @@
+from ctypes import c_uint8, c_uint16, c_uint32
+
+class Addressable:
+    def __init__(self, start=0, end=0):
+        self.start      = start
+        self.end        = end
+    def addr_to_pos(self, addr):
+        if not (self.start <= addr < self.end):
+            raise KeyError("Address out of space")
+        return addr - self.start
+
+def merge_bytes (byte_iter):
+    val = 0
+    for i,v in enumerate(byte_ouput):
+        val += v.value << 8 * i
+    return val
+def split_bytes (val, byte_count):
+    return tuple( c_uint8(val >> 8 * i) for i in range(byte_count) )
+
+class Memory32 (Addressable):
+    """
+    This is a raw 32-bit word memory addressable at a byte level.
+    Internally it is defined as c_uint8 list.
+    Special functions are needed to access halfs (c_uint16) and words
+    (c_uint32).
+    """
+
+    def __init__(self, start=0, end=0, bigEndian=False):
+        super().__init__(start, end)
+        self.bigEndian  = bigEndian
+        self.lastChange = None
+        # Pre-allocate or allocate or allocate per write?
+        self.data       = [None] * (end - start)
+
+    def get_byte(self, addr):
+        return self.data[ self.addr_to_pos(addr) ]
+    def set_byte(self, addr, val):
+        if not isinstance(val, c_uint8):
+            if val > 0xFF:
+                raise ValueError("Value is larger than a byte")
+        self.data[ self.addr_to_pos(addr) ] = val if isinstance(val, c_uint8) else c_uint8(val)
+        self.lastChange = range(addr, addr+1)
+
+
+    def get_half(self,addr):
+        byte_output = (get_byte(addr), get_byte(addr+1))
+        if self.bigEndian:
+            byte_output = reversed(byte_output)
+        return c_uint16( merge_bytes(byte_output) )
+
+    def set_half(self, addr, val):
+        if not isinstance(val, c_uint16):
+            if val > 0xFFFF:
+                raise ValueError("Value is larger than a half")
+        bytes = split_bytes(val, 2)
+        if self.bigEndian:
+            bytes = reversed(bytes)
+        for i,v in enumerate(bytes):
+            self.set_byte(addr+i, v)
+        self.lastChange = range(addr,addr+2)
+
+    def get_word(self, pos):
+        byte_output = tuple(get_byte(addr+i) for i in range(4))
+        if self.bigEndian:
+            byte_output = reversed(byte_output)
+        return c_uint32( merge_bytes(byte_output) )
+
+    def set_word(self, addr, val):
+        if not isinstance(val, c_uint32):
+            if val > 0xFFFFFFFF:
+                raise ValueError("Value is larger than a word")
+        bytes = split_bytes(val, 4)
+        if self.bigEndian:
+            bytes = reversed(bytes)
+        for i,v in enumerate(bytes):
+            self.set_byte(addr+i, v)
+        self.lastChange = range(addr,addr+4)
+
+    def __str__(self):
+        out = "   "
+        out += "-" * 50
+        out += "\n"
+        for i,d in enumerate(self.data):
+            if d is not None:
+                addr = i+self.start
+                out += "->" if addr in self.lastChange  else "  "
+                out += f"| {addr:#20x} | {d.value:#5} | {d.value:#04x} | {d.value:#010b} |"
+                out += "\n"
+        out += "   "
+        out += "-" * 50
+        out += "\n"
+        return out
+
+
+class Memory32RO (Memory32):
+    def set_byte(self, addr, val):
+        raise NotImplementedError("Trying to write in a read-only memory")
+    def set_half(self, addr, val):
+        raise NotImplementedError("Trying to write in a read-only memory")
+    def set_word(self, addr, val):
+        raise NotImplementedError("Trying to write in a read-only memory")
+
+class CodeMemory32 (Memory32RO):
+    def __init__(self, start=0, end=0):
+        super().__init__(writable=False,start=start,end=end)
+
+
+if __name__ == "__main__":
+    m = Memory32(start=100,end=200)
+    print(m.start, m.end)
+    m.set_byte(100, 246)
+    print(m)