1 files changed, 17 insertions, 14 deletions
diff --git a/src/secp256k1/src/scratch.h b/src/secp256k1/src/scratch.h
index fef377af0d..77b35d126b 100644
--- a/src/secp256k1/src/scratch.h
+++ b/src/secp256k1/src/scratch.h
@@ -7,33 +7,36 @@
 #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 {
-    void *data[SECP256K1_SCRATCH_MAX_FRAMES];
-    size_t offset[SECP256K1_SCRATCH_MAX_FRAMES];
-    size_t frame_size[SECP256K1_SCRATCH_MAX_FRAMES];
-    size_t frame;
+    /** guard against interpreting this object as other types */
+    unsigned char magic[8];
+    /** actual allocated data */
+    void *data;
+    /** 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;
-    const secp256k1_callback* error_callback;
 } secp256k1_scratch;
 
 static secp256k1_scratch* secp256k1_scratch_create(const secp256k1_callback* error_callback, size_t max_size);
 
-static void secp256k1_scratch_destroy(secp256k1_scratch* scratch);
+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(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(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_scratch* scratch, size_t n_objects);
+static size_t secp256k1_scratch_max_allocation(const secp256k1_callback* error_callback, const secp256k1_scratch* scratch, size_t n_objects);
 
 /** Returns a pointer into the most recently allocated frame, or NULL if there is insufficient available space */
-static void *secp256k1_scratch_alloc(secp256k1_scratch* scratch, size_t n);
+static void *secp256k1_scratch_alloc(const secp256k1_callback* error_callback, secp256k1_scratch* scratch, size_t n);
 
 #endif