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Updated ...md (markdown)

manojampalam 2016-02-24 13:48:48 -08:00
parent 89a602520a
commit 4ce35c1462
1 changed files with 11 additions and 2 deletions
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@ -32,9 +32,18 @@ Brief design details of POSIX wrapper
- IO completions
- Signals
- Timers
+ All underlying Win32 IO API calls are made asynchronous (non-blocking). Blocking semantics are implemented within the wrapper by an explicit wait for IO to complete.
+ All underlying Win32 IO API calls are made asynchronous (non-blocking). Blocking semantics are implemented within the wrapper by an explicit "wait_for_any" for IO to complete.
+ Uses [APCs](https://msdn.microsoft.com/en-us/library/windows/desktop/ms681951(v=vs.85).aspx) wherever available and minimzing use of [events](https://msdn.microsoft.com/en-us/library/windows/desktop/ms682655(v=vs.85).aspx). This simplifies code and has performance benefits.
+ Maintains internal buffers to accommodate an underlying fundamental difference between POSIX and Win32 IO APIs - IOReady Vs IOComplete (Ex for a Read operation, POSIX APIs signal when IO is ready - date will be subsequently, explicitly read, Win32 APIs signal when IO has completed - data is already copied to a user provided buffer.
+ Maintains internal buffers to accommodate an underlying fundamental difference between POSIX and Win32 IO APIs - IOReady Vs IOComplete (Ex for a Read operation, POSIX APIs signal when IO is ready - date will be subsequently, explicitly read, Win32 APIs signal when IO has completed - data is already copied to a user provided buffer. Though this may be perceived as a performance hit, a validation exercise did not show any major impact. It in fact proved beneficial in reducing kernel calls during "read"s (ex. reading a header, would fetch the entire packet in a single call).
+ Additional details on underlying Win32 calls used
| POSIX IO call | Underlying Win32 IO call | Additional details |
|-----|-----|
| accept | AcceptEx | No APC semantics so, explicit event used for async IO |
| connect | ConnectEx | No APC semantics so, explicit event used for async IO |
| send | WSASend | |
| recv | WSARecv | |
| open | CreateFile | |
| pipe | CreateNamedPipe | A uni directional named pipe with and internal name is created, CreateFile called to connect from other end |