Added a comment documenting the format of the messages

between SM and clients.

include/messageFormat.h

@@ -8,16 +8,98 @@ namespace storagemanager
 {
 
 static const uint SM_MSG_START=0xbf65a7e1;
+static const char *socket_name = "\0storagemanager";
 
 enum Opcodes {
     OPEN,
     READ,
     WRITE,
     STAT,
-    UNLINK
+    UNLINK,
+    APPEND,
+    TRUNCATE,
+    LIST_DIRECTORY,
+    PING
 };
 
-}
+/*
+    All commands sent to and from StorageManager begin with
+    SM_MSG_START, and a uint32_t for the length of the payload.
+    
+    In the payload, all responses from StorageManager begin with
+    a return code, which is the same as the corresponding syscall.
+    If the return code is an error (usually < 0), then a 4-byte
+    value for errno follows.  On success, no errno is sent.
+
+    On success, what follows is any output parameters from the call.
+
+    OPEN
+    ----
+    command format:
+    opcode|4-byte filename length|filename|4-byte openmode
+
+    response format:
+    struct stat
+
+    READ
+    ----
+    command format:
+    opcode|4-byte filename length|filename|size_t count|off_t offset
+
+    response format:
+    data (size is stored in the return code)
+
+    WRITE
+    -----
+    command format:
+    opcode|4-byte filename length|filename|size_t count|off_t offset|data
+
+    response format:
+
+    APPEND
+    ------
+    command format:
+    opcode|4-byte filename length|filename|size_t count|data
+
+    response format:
+
+    UNLINK
+    ------
+    command format:
+    opcode|4-byte filename length|filename
+
+    response format:
+    
+    STAT
+    ----
+    command format:
+    opcode|4-byte filename length|filename
+
+    response format:
+    struct stat
+
+    TRUNCATE
+    --------
+    command format:
+    opcode|4-byte filename length|filename|off64_t length
+   
+    response format:
+    
+    LIST_DIRECTORY
+    --------------
+    command format:
+    opcode|4-byte path length|pathname
+
+    response format:
+    4-byte num elements|
+    (4-byte filename length|filename) * num elements
+    
+    PING
+    ----
+    command format:
+    opcode
+
+    reponse format:
 
 #endif