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Extend PacketQueue to take PktOut as well.

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Some upcoming restructuring I've got planned will need to pass output
packets back and forth on queues, as well as input ones. So here's a
change that arranges that we can have a PktInQueue and a PktOutQueue,
sharing most of their implementation via a PacketQueueBase structure
which links together the PacketQueueNode fields in the two packet
structures.

There's a tricksy bit of macro manoeuvring to get all of this
type-checked, so that I can't accidentally link a PktOut on to a
PktInQueue or vice versa. It works by having the main queue functions
wrapped by macros; when receiving a packet structure on input, they
type-check it against the queue structure and then automatically look
up its qnode field to pass to the underlying PacketQueueBase function;
on output, they translate a returned PacketQueueNode back to its
containing packet type by calling a 'get' function pointer.
This commit is contained in:
Simon Tatham
2018-09-19 21:56:11 +01:00
parent 63a14f26f7
commit 6e24b7d589
3 changed files with 113 additions and 85 deletions
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44
ssh.h
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@ -81,20 +81,46 @@ typedef struct PktOut {
unsigned downstream_id;
const char *additional_log_text;
PacketQueueNode qnode; /* for linking this packet on to a queue */
BinarySink_IMPLEMENTATION;
} PktOut;
typedef struct PacketQueue {
typedef struct PacketQueueBase {
PacketQueueNode end;
} PacketQueue;
} PacketQueueBase;
void pq_init(struct PacketQueue *pq);
void pq_push(struct PacketQueue *pq, PktIn *pkt);
void pq_push_front(struct PacketQueue *pq, PktIn *pkt);
PktIn *pq_peek(struct PacketQueue *pq);
PktIn *pq_pop(struct PacketQueue *pq);
void pq_clear(struct PacketQueue *pq);
int pq_empty_on_to_front_of(struct PacketQueue *src, struct PacketQueue *dest);
typedef struct PktInQueue {
PacketQueueBase pqb;
PktIn *(*get)(PacketQueueBase *, int pop);
} PktInQueue;
typedef struct PktOutQueue {
PacketQueueBase pqb;
PktOut *(*get)(PacketQueueBase *, int pop);
} PktOutQueue;
void pq_base_init(PacketQueueBase *pqb);
void pq_base_push(PacketQueueBase *pqb, PacketQueueNode *node);
void pq_base_push_front(PacketQueueBase *pqb, PacketQueueNode *node);
int pq_base_empty_on_to_front_of(PacketQueueBase *src, PacketQueueBase *dest);
void pq_in_init(PktInQueue *pq);
void pq_out_init(PktOutQueue *pq);
void pq_in_clear(PktInQueue *pq);
void pq_out_clear(PktOutQueue *pq);
#define pq_push(pq, pkt) \
TYPECHECK((pq)->get(&(pq)->pqb, FALSE) == pkt, \
pq_base_push(&(pq)->pqb, &(pkt)->qnode))
#define pq_push_front(pq, pkt) \
TYPECHECK((pq)->get(&(pq)->pqb, FALSE) == pkt, \
pq_base_push_front(&(pq)->pqb, &(pkt)->qnode))
#define pq_peek(pq) ((pq)->get(&(pq)->pqb, FALSE))
#define pq_pop(pq) ((pq)->get(&(pq)->pqb, TRUE))
#define pq_empty_on_to_front_of(src, dst) \
TYPECHECK((src)->get(&(src)->pqb, FALSE) == \
(dst)->get(&(dst)->pqb, FALSE), \
pq_base_empty_on_to_front_of(&(src)->pqb, &(dst)->pqb))
/*
* Packet type contexts, so that ssh2_pkt_type can correctly decode