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scratch: replace frames with "checkpoint" system

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This commit is contained in:
Andrew Poelstra
2019-05-25 14:15:38 +00:00
parent 7623cf2b97
commit 98836b11f0
4 changed files with 101 additions and 83 deletions
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22
src/scratch.h
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@@ -7,17 +7,17 @@
#ifndef _SECP256K1_SCRATCH_
#define _SECP256K1_SCRATCH_
#define SECP256K1_SCRATCH_MAX_FRAMES 5
/* The typedef is used internally; the struct name is used in the public API
* (where it is exposed as a different typedef) */
typedef struct secp256k1_scratch_space_struct {
/** guard against interpreting this object as other types */
unsigned char magic[8];
/** actual allocated data */
void *data;
void *current_frame;
size_t offset[SECP256K1_SCRATCH_MAX_FRAMES];
size_t frame_size[SECP256K1_SCRATCH_MAX_FRAMES];
size_t frame;
/** amount that has been allocated (i.e. `data + offset` is the next
* available pointer) */
size_t alloc_size;
/** maximum size available to allocate */
size_t max_size;
} secp256k1_scratch;
@@ -25,11 +25,13 @@ static secp256k1_scratch* secp256k1_scratch_create(const secp256k1_callback* err
static void secp256k1_scratch_destroy(const secp256k1_callback* error_callback, secp256k1_scratch* scratch);
/** Attempts to allocate a new stack frame with `n` available bytes. Returns 1 on success, 0 on failure */
static int secp256k1_scratch_allocate_frame(const secp256k1_callback* error_callback, secp256k1_scratch* scratch, size_t n, size_t objects);
/** Returns an opaque object used to "checkpoint" a scratch space. Used
* with `secp256k1_scratch_apply_checkpoint` to undo allocations. */
static size_t secp256k1_scratch_checkpoint(const secp256k1_callback* error_callback, const secp256k1_scratch* scratch);
/** Deallocates a stack frame */
static void secp256k1_scratch_deallocate_frame(const secp256k1_callback* error_callback, secp256k1_scratch* scratch);
/** Applies a check point received from `secp256k1_scratch_checkpoint`,
* undoing all allocations since that point. */
static void secp256k1_scratch_apply_checkpoint(const secp256k1_callback* error_callback, secp256k1_scratch* scratch, size_t checkpoint);
/** Returns the maximum allocation the scratch space will allow */
static size_t secp256k1_scratch_max_allocation(const secp256k1_callback* error_callback, const secp256k1_scratch* scratch, size_t n_objects);