ksung@uiucdcsm.cs.uiuc.edu (06/24/88)
I've noticed some inconsistency between the PEX protocol specification
and the encoding documentation (Version 3.1)
In the version 3.1 protocol spec., PEX_FetchStructure and
PEX_FetchElementRange protocols are removed and PEX_FetchElements is added in.
However, the encoding scheme for FetchStructure and FetchElementRange
still exists in 3.1 encoding documentation, while there's no documentation
on how to encode FetchElements.
Also, in the header file :
PEX.h - opcode for PEX_FetchStructure & PEX_FetchElementRange
are still there, but there's no opcode for PEX_FetchElements
Another thing I noticed is the inconsistency betweem the encoding
documentation and the header file PEXproto.h. Some examples are:
Encoding documentation says:
Get Extension reply
(1)--> 1 CARD8 reply opcode
(2)--> 1 1 PEX opcode
(3)--> 2 CARD16 sequence number
(4)--> 2 n length of vendor name
(5)--> 4 (n+p)/4 reply length (# additional (>5) words in reply)
(6)--> 2 CARD16 protocol major version
(7)--> 2 CARD16 protocol minor version
(8)--> 4 CARD32 release number
(9)--> 4 CARD32 subset information
(10)-->12 unused
while in PEXproto.h the reply structure is defined as :
typedef struct {
(1)--> BYTE type; /* X_Reply */
(2)--> CARD8 what;
(3)--> CARD16 sequenceNumber B16;
(4)--> CARD32 length B32; /* not 0 */
(5)--> CARD16 majorVersion B16;
(6)--> CARD16 minorVersion B16;
(7)--> CARD32 release B32;
(8)--> CARD32 lengthName B32;
(9)--> CARD32 subsetInfo B32;
(10)--> BYTE pad[8];
} pexGetExtensinoInfoReply;
Notice, length_of_vendor_name is defined to be 2 bytes in encoding
ducoment, while PEXproto.h defined it to be 4 bytes. Also, the
release_number comes before subset_information in encoding
document, while it's another way around in PEXproto.h
Another example is ElementSearchReq :
Encoding Document says:
Element Search
1 CARD8 opcode (x11 assigned)
1 42 PEX opcode
2 5+i+e request length
4 CARD32 Structure ID
2 whence
0 Beginning
1 Current
2 End
2 direction
0 Forward
1 Backward
4 offset
2 i number of elements in incl list
2 unused
4i LISTofELEMENT_TYPE (incl)
2 e number of elements in excl list
2 unused
4e LISTofELEMENT_TYPE (excl)
while in PEXproto.h the request structure is defined as :
typedef struct {
CARD8 reqType;
CARD8 opcode;
CARD16 length B16;
pexStructure sid B32;
pexElementPos position;
CARD32 direction B32;
CARD32 numIncls B32;
CARD32 numExcls B32;
} pexElementSearchReq;
pexElementPos is defined in PEXprotostr as:
typedef struct {
CARD16 whence B16;
CARD16 pad B16;
INT32 offset B32;
} pexElementPos;
In the encoding document the 11th & 12th bytes specifies direction while in
PEXproto.h the 11th & 12th bytes are not used.
In situiations like this (when things do not agree), which one should
we believe?
Another question is: Is the documentation for version 3.1 PEX overview
ready yet? If yes, where can I get it? If no,
anyone has any idea when it will be ready?
ksung@m.cs.uiuc.edu