Use Buffer in cloud server instead of opaques (#9875)

Not-quite-required but makes cloud graph a *lot* cleaner because unlike
raw compiled programs `GraphRunner` takes `Buffer`s like other runners.

Otherwise either of: adding a new option to not free on `__del__`,
(ab)using `external_ptr` to prevent free, or making something like a
`FakeBuffer` is required.

tinygrad/runtime/ops_cloud.py

@@ -13,7 +13,7 @@ from http.server import HTTPServer, BaseHTTPRequestHandler
 from tinygrad.renderer import Renderer
 from tinygrad.dtype import dtypes
 from tinygrad.helpers import getenv, DEBUG, fromimport, unwrap, Timing
-from tinygrad.device import Compiled, Allocator, Compiler, Device, BufferSpec
+from tinygrad.device import Compiled, Buffer, Allocator, Compiler, Device, BufferSpec
 
 # ***** API *****
 
@@ -75,8 +75,7 @@ class BatchRequest:
 @dataclass
 class CloudSession:
   programs: dict[tuple[str, str], Any] = field(default_factory=dict)
-  # TODO: the buffer should track this internally
-  buffers: dict[int, tuple[Any, int, Optional[BufferSpec]]] = field(default_factory=dict)
+  buffers: dict[int, Buffer] = field(default_factory=dict)
 
 class CloudHandler(BaseHTTPRequestHandler):
   protocol_version = 'HTTP/1.1'
@@ -99,21 +98,16 @@ class CloudHandler(BaseHTTPRequestHandler):
         match c:
           case BufferAlloc():
             assert c.buffer_num not in session.buffers, f"buffer {c.buffer_num} already allocated"
-            session.buffers[c.buffer_num] = (Device[CloudHandler.device].allocator.alloc(c.size, c.options), c.size, c.options)
-          case BufferFree():
-            buf,sz,buffer_options = session.buffers[c.buffer_num]
-            Device[CloudHandler.device].allocator.free(buf,sz,buffer_options)
-            del session.buffers[c.buffer_num]
-          case CopyIn(): Device[CloudHandler.device].allocator._copyin(session.buffers[c.buffer_num][0], memoryview(bytearray(req._h[c.datahash])))
-          case CopyOut():
-            buf,sz,_ = session.buffers[c.buffer_num]
-            Device[CloudHandler.device].allocator._copyout(memoryview(ret:=bytearray(sz)), buf)
+            session.buffers[c.buffer_num] = Buffer(CloudHandler.device, c.size, dtypes.uint8, options=c.options, preallocate=True)
+          case BufferFree(): del session.buffers[c.buffer_num]
+          case CopyIn(): session.buffers[c.buffer_num].copyin(memoryview(bytearray(req._h[c.datahash])))
+          case CopyOut(): session.buffers[c.buffer_num].copyout(memoryview(ret:=bytearray(session.buffers[c.buffer_num].nbytes)))
           case ProgramAlloc():
             lib = Device[CloudHandler.device].compiler.compile_cached(req._h[c.datahash].decode())
             session.programs[(c.name, c.datahash)] = Device[CloudHandler.device].runtime(c.name, lib)
           case ProgramFree(): del session.programs[(c.name, c.datahash)]
           case ProgramExec():
-            bufs = [session.buffers[x][0] for x in c.bufs]
+            bufs = [session.buffers[x]._buf for x in c.bufs]
             extra_args = {k:v for k,v in [("global_size", c.global_size), ("local_size", c.local_size)] if v is not None}
             r = session.programs[(c.name, c.datahash)](*bufs, vals=c.vals, wait=c.wait, **extra_args)
             if r is not None: ret = str(r).encode()