From 964fea7500f4bcba3bf2629e959df415ee0ce48f Mon Sep 17 00:00:00 2001 From: Matthew Sotoudeh Date: Thu, 16 May 2024 11:15:19 -0700 Subject: more documentation --- buddy.h | 30 +++++++++++++++++++++++++++--- magic_buddy.c | 8 ++++++++ 2 files changed, 35 insertions(+), 3 deletions(-) diff --git a/buddy.h b/buddy.h index ad4f4aa..c8778d6 100644 --- a/buddy.h +++ b/buddy.h @@ -12,20 +12,44 @@ struct buddy { void *base; }; -// NOTE: after init_buddy, *state should never move. +// Initialize a buddy with (constant) global state stored in @state. +// NOTE: after initializing the buddy, you should always pass the exact same +// pointer in for @state in future calls. If you need to move @state, use +// move_buddy(...). void init_buddy(uint8_t *base, size_t size, uint8_t magic[MAGIC_COOKIE_BYTES], struct buddy *state); +// Allocate a block of size >= @size void *allocate(size_t size, struct buddy *state); + +// Liberate a block of size @size starting at @base. void liberate(void *base, size_t size, struct buddy *state); +// Print debug information for the allocator. void debug_buddy(struct buddy *state); +// Simulates @new = allocate, memcpy(@new, @old), free(@old), with some +// optimizations for cases where the reallocation can be done in place. void *reallocate(void *old, size_t old_size, size_t new_size, struct buddy *state); + +// Attempts to reserve a range [@start,@start+@size). +// Returns 1 if success, 0 otherwise. +// Whenever possible, we avoid writing anything into the reserved region. int reserve(void *start, size_t size, struct buddy *state); -// grow can also be used to move the buddy. grow can never fail. +// Update @state to assume the memory pool has been copied to +// [@new_base,@new_base+@new_size) +// Can *ONLY* be used when @new_size >= the existing size. void grow_buddy(uint8_t *new_base, size_t new_size, struct buddy *state); -// 0 -> failure. always in-place. to do out-of-place, first shrink then grow. + +// Update @state to only use the subset of the pool in range +// [@state->base,@state->base+new_size) +// Can *ONLY* be used when @new_size <= the existing size. +// This *CAN* write to anything in the old pool. +// This *CAN* fail, in which case everything is unmodified and 0 is returned. +// Upon success, 1 is returned. int shrink_buddy(size_t new_size, struct buddy *state); + +// Used to move the global state of the buddy. +void move_buddy(struct buddy *new_state, struct buddy *old_state); diff --git a/magic_buddy.c b/magic_buddy.c index a741132..1e88c21 100644 --- a/magic_buddy.c +++ b/magic_buddy.c @@ -311,3 +311,11 @@ int shrink_buddy(size_t new_size, struct buddy *state) { state->root_logsize = logsize; return 1; } + +void move_buddy(struct buddy *new_state, struct buddy *old_state) { + memcpy(new_state, old_state, sizeof(struct buddy)); + for (size_t i = 0; i < ADDRESS_BITS; i++) { + if (!new_state->avail[i]) continue; + new_state->avail[i]->pprev = &(new_state->avail[i]); + } +} -- cgit v1.2.3