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buflib: Add a define telling the per-alloc overhead.

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This allows buflib clients to more accurately estimate the total memory usage.
It's still not 100% accurate because the handle table grows in blocks, thus
buflib might use more memory that caused by allocations directly.

Change-Id: I68338bb94f510ad188fcb588aebf895b5f9197c5
This commit is contained in:
Thomas Martitz 2014-01-28 06:58:09 +01:00
parent 4ce1deacfd
commit 4ce39f7e73
2 changed files with 13 additions and 0 deletions
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2
firmware/buflib.c
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@ -55,6 +55,8 @@
* to find the start of the character array (and therefore the start of the
* entire block) when only the handle or payload start is known.
*
* UPDATE BUFLIB_ALLOC_OVERHEAD (buflib.h) WHEN THIS COOKIE CHANGES!
*
* Example:
* |<- alloc block #1 ->|<- unalloc block ->|<- alloc block #2 ->|<-handle table->|
* |L|H|C|cccc|L2|crc|XXXXXX|-L|YYYYYYYYYYYYYYYY|L|H|C|cc|L2|crc|XXXXXXXXXXXXX|AAA|

11
firmware/include/buflib.h
View file

@ -53,6 +53,17 @@ struct buflib_context
bool compact;
};
/**
* This declares the minimal overhead that is required per alloc. These
* are bytes that are allocated from the context's pool in addition
* to the actually requested number of bytes.
*
* The total number of bytes consumed by an allocation is
* BUFLIB_ALLOC_OVERHEAD + requested bytes + strlen(<name passed to
* buflib_alloc_ex()) + pad to pointer size
*/
#define BUFLIB_ALLOC_OVERHEAD (6*sizeof(union buflib_data))
/**
* Callbacks used by the buflib to inform allocation that compaction
* is happening (before data is moved)