Mailboxes should be implemented as a queue which allows multiple messages to be posted (implementing as a rendez-vous point where only one message can be posted at a time can have a highly negative impact on performance). A message in a mailbox is just a pointer, nothing more.
◆ sys_arch_mbox_fetch()
u32_t sys_arch_mbox_fetch |
( |
sys_mbox_t * |
mbox, |
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void ** |
msg, |
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u32_t |
timeout |
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) |
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Blocks the thread until a message arrives in the mailbox, but does not block the thread longer than "timeout" milliseconds (similar to the sys_arch_sem_wait() function). If "timeout" is 0, the thread should be blocked until a message arrives. The "msg" argument is a result parameter that is set by the function (i.e., by doing "*msg =
ptr"). The "msg" parameter maybe NULL to indicate that the message should be dropped. The return values are the same as for the sys_arch_sem_wait() function: SYS_ARCH_TIMEOUT if there was a timeout, any other value if a messages is received.
Note that a function with a similar name, sys_mbox_fetch(), is implemented by lwIP.
- Parameters
-
mbox | mbox to get a message from |
msg | pointer where the message is stored |
timeout | maximum time (in milliseconds) to wait for a message (0 = wait forever) |
- Returns
- SYS_ARCH_TIMEOUT on timeout, any other value if a message has been received
◆ sys_arch_mbox_tryfetch()
u32_t sys_arch_mbox_tryfetch |
( |
sys_mbox_t * |
mbox, |
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void ** |
msg |
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) |
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This is similar to sys_arch_mbox_fetch, however if a message is not present in the mailbox, it immediately returns with the code SYS_MBOX_EMPTY. On success 0 is returned. To allow for efficient implementations, this can be defined as a function-like macro in sys_arch.h instead of a normal function. For example, a naive implementation could be: #define sys_arch_mbox_tryfetch(mbox,msg) sys_arch_mbox_fetch(mbox,msg,1) although this would introduce unnecessary delays.
- Parameters
-
mbox | mbox to get a message from |
msg | pointer where the message is stored |
- Returns
- 0 (milliseconds) if a message has been received or SYS_MBOX_EMPTY if the mailbox is empty
◆ sys_mbox_free()
void sys_mbox_free |
( |
sys_mbox_t * |
mbox | ) |
|
Deallocates a mailbox. If there are messages still present in the mailbox when the mailbox is deallocated, it is an indication of a programming error in lwIP and the developer should be notified.
- Parameters
-
◆ sys_mbox_new()
err_t sys_mbox_new |
( |
sys_mbox_t * |
mbox, |
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int |
size |
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) |
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Creates an empty mailbox for maximum "size" elements. Elements stored in mailboxes are pointers. You have to define macros "_MBOX_SIZE" in your lwipopts.h, or ignore this parameter in your implementation and use a default size. If the mailbox has been created, ERR_OK should be returned. Returning any other error will provide a hint what went wrong, but except for assertions, no real error handling is implemented.
- Parameters
-
mbox | pointer to the mbox to create |
size | (minimum) number of messages in this mbox |
- Returns
- ERR_OK if successful, another err_t otherwise
◆ sys_mbox_post()
void sys_mbox_post |
( |
sys_mbox_t * |
mbox, |
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void * |
msg |
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) |
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Post a message to an mbox - may not fail -> blocks if full, only to be used from tasks NOT from ISR!
- Parameters
-
mbox | mbox to posts the message |
msg | message to post (ATTENTION: can be NULL) |
◆ sys_mbox_set_invalid()
void sys_mbox_set_invalid |
( |
sys_mbox_t * |
mbox | ) |
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Invalidate a mailbox so that sys_mbox_valid() returns 0. ATTENTION: This does NOT mean that the mailbox shall be deallocated: sys_mbox_free() is always called before calling this function! This may also be a define, in which case the function is not prototyped.
◆ sys_mbox_trypost()
err_t sys_mbox_trypost |
( |
sys_mbox_t * |
mbox, |
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void * |
msg |
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) |
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Try to post a message to an mbox - may fail if full. Can be used from ISR (if the sys arch layer allows this). Returns ERR_MEM if it is full, else, ERR_OK if the "msg" is posted.
- Parameters
-
mbox | mbox to posts the message |
msg | message to post (ATTENTION: can be NULL) |
◆ sys_mbox_trypost_fromisr()
err_t sys_mbox_trypost_fromisr |
( |
sys_mbox_t * |
mbox, |
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void * |
msg |
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) |
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Try to post a message to an mbox - may fail if full. To be be used from ISR. Returns ERR_MEM if it is full, else, ERR_OK if the "msg" is posted.
- Parameters
-
mbox | mbox to posts the message |
msg | message to post (ATTENTION: can be NULL) |
◆ sys_mbox_valid()
int sys_mbox_valid |
( |
sys_mbox_t * |
mbox | ) |
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Returns 1 if the mailbox is valid, 0 if it is not valid. When using pointers, a simple way is to check the pointer for != NULL. When directly using OS structures, implementing this may be more complex. This may also be a define, in which case the function is not prototyped.