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AP_Common: expanding array uses realloc

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also make chunk_size const and recommend factor of 2
also reduce top level array's initial size to 32 elements
This commit is contained in:
Randy Mackay 2019-06-19 07:38:14 +09:00
parent da645c32ff
commit 2cb89d9a02
1 changed files with 4 additions and 9 deletions
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13
libraries/AP_Common/AP_ExpandingArray.h
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@ -31,6 +31,7 @@
* Warnings:
* 1. memset, memcpy, memcmp cannot be used because the individual elements are not guaranteed to be next to each other in memory
* 2. operator[] functions do not perform any range checking so max_items() should be used when necessary to avoid out-of-bound memory access
* 3. elements_per_chunk (provided in constructor) should be a factor of 2 (i.e. 16, 32, 64) for best performance
*/
#pragma once
@ -75,15 +76,10 @@ public:
// expand chunk_ptrs array if necessary
if (chunk_count + num_chunks >= chunk_count_max) {
uint16_t chunk_ptr_size = chunk_count + num_chunks + chunk_ptr_increment;
chunk_ptr_t *chunk_ptrs_new = (chunk_ptr_t*)calloc(chunk_ptr_size, sizeof(T*));
chunk_ptr_t *chunk_ptrs_new = (chunk_ptr_t*)realloc(chunk_ptrs, chunk_ptr_size * sizeof(T*));
if (chunk_ptrs_new == nullptr) {
return false;
}
// copy pointers to new points array
memcpy(chunk_ptrs_new, chunk_ptrs, chunk_count_max * sizeof(T*));
// free old pointers array
free(chunk_ptrs);
// use new pointers array
chunk_ptrs = chunk_ptrs_new;
@ -116,12 +112,11 @@ public:
private:
// chunk_ptrs array is grown by this many elements each time it fills
const uint16_t chunk_ptr_increment = 50;
const uint16_t chunk_size; // the number of T elements in each chunk
const uint16_t chunk_ptr_increment = 32; // chunk_ptrs array is grown by this many elements each time it fills
typedef T* chunk_ptr_t; // pointer to a chunk
uint16_t chunk_size; // the number of T elements in each chunk
chunk_ptr_t *chunk_ptrs; // array of pointers to allocated chunks
uint16_t chunk_count_max; // number of elements in chunk_ptrs array
uint16_t chunk_count; // number of allocated chunks