1 files changed, 47 insertions, 45 deletions

diff --git a/src/secp256k1/src/scratch_impl.h b/src/secp256k1/src/scratch_impl.h
index abed713b21..4cee700001 100644
--- a/src/secp256k1/src/scratch_impl.h
+++ b/src/secp256k1/src/scratch_impl.h
@@ -7,78 +7,80 @@
 #ifndef _SECP256K1_SCRATCH_IMPL_H_
 #define _SECP256K1_SCRATCH_IMPL_H_
 
+#include "util.h"
 #include "scratch.h"
 
-/* Using 16 bytes alignment because common architectures never have alignment
- * requirements above 8 for any of the types we care about. In addition we
- * leave some room because currently we don't care about a few bytes.
- * TODO: Determine this at configure time. */
-#define ALIGNMENT 16
-
-static secp256k1_scratch* secp256k1_scratch_create(const secp256k1_callback* error_callback, size_t max_size) {
-    secp256k1_scratch* ret = (secp256k1_scratch*)checked_malloc(error_callback, sizeof(*ret));
+static secp256k1_scratch* secp256k1_scratch_create(const secp256k1_callback* error_callback, size_t size) {
+    const size_t base_alloc = ((sizeof(secp256k1_scratch) + ALIGNMENT - 1) / ALIGNMENT) * ALIGNMENT;
+    void *alloc = checked_malloc(error_callback, base_alloc + size);
+    secp256k1_scratch* ret = (secp256k1_scratch *)alloc;
     if (ret != NULL) {
         memset(ret, 0, sizeof(*ret));
-        ret->max_size = max_size;
-        ret->error_callback = error_callback;
+        memcpy(ret->magic, "scratch", 8);
+        ret->data = (void *) ((char *) alloc + base_alloc);
+        ret->max_size = size;
     }
     return ret;
 }
 
-static void secp256k1_scratch_destroy(secp256k1_scratch* scratch) {
+static void secp256k1_scratch_destroy(const secp256k1_callback* error_callback, secp256k1_scratch* scratch) {
     if (scratch != NULL) {
-        VERIFY_CHECK(scratch->frame == 0);
+        VERIFY_CHECK(scratch->alloc_size == 0); /* all checkpoints should be applied */
+        if (memcmp(scratch->magic, "scratch", 8) != 0) {
+            secp256k1_callback_call(error_callback, "invalid scratch space");
+            return;
+        }
+        memset(scratch->magic, 0, sizeof(scratch->magic));
         free(scratch);
     }
 }
 
-static size_t secp256k1_scratch_max_allocation(const secp256k1_scratch* scratch, size_t objects) {
-    size_t i = 0;
-    size_t allocated = 0;
-    for (i = 0; i < scratch->frame; i++) {
-        allocated += scratch->frame_size[i];
-    }
-    if (scratch->max_size - allocated <= objects * ALIGNMENT) {
+static size_t secp256k1_scratch_checkpoint(const secp256k1_callback* error_callback, const secp256k1_scratch* scratch) {
+    if (memcmp(scratch->magic, "scratch", 8) != 0) {
+        secp256k1_callback_call(error_callback, "invalid scratch space");
         return 0;
     }
-    return scratch->max_size - allocated - objects * ALIGNMENT;
+    return scratch->alloc_size;
 }
 
-static int secp256k1_scratch_allocate_frame(secp256k1_scratch* scratch, size_t n, size_t objects) {
-    VERIFY_CHECK(scratch->frame < SECP256K1_SCRATCH_MAX_FRAMES);
-
-    if (n <= secp256k1_scratch_max_allocation(scratch, objects)) {
-        n += objects * ALIGNMENT;
-        scratch->data[scratch->frame] = checked_malloc(scratch->error_callback, n);
-        if (scratch->data[scratch->frame] == NULL) {
-            return 0;
-        }
-        scratch->frame_size[scratch->frame] = n;
-        scratch->offset[scratch->frame] = 0;
-        scratch->frame++;
-        return 1;
-    } else {
-        return 0;
+static void secp256k1_scratch_apply_checkpoint(const secp256k1_callback* error_callback, secp256k1_scratch* scratch, size_t checkpoint) {
+    if (memcmp(scratch->magic, "scratch", 8) != 0) {
+        secp256k1_callback_call(error_callback, "invalid scratch space");
+        return;
+    }
+    if (checkpoint > scratch->alloc_size) {
+        secp256k1_callback_call(error_callback, "invalid checkpoint");
+        return;
     }
+    scratch->alloc_size = checkpoint;
 }
 
-static void secp256k1_scratch_deallocate_frame(secp256k1_scratch* scratch) {
-    VERIFY_CHECK(scratch->frame > 0);
-    scratch->frame -= 1;
-    free(scratch->data[scratch->frame]);
+static size_t secp256k1_scratch_max_allocation(const secp256k1_callback* error_callback, const secp256k1_scratch* scratch, size_t objects) {
+    if (memcmp(scratch->magic, "scratch", 8) != 0) {
+        secp256k1_callback_call(error_callback, "invalid scratch space");
+        return 0;
+    }
+    if (scratch->max_size - scratch->alloc_size <= objects * (ALIGNMENT - 1)) {
+        return 0;
+    }
+    return scratch->max_size - scratch->alloc_size - objects * (ALIGNMENT - 1);
 }
 
-static void *secp256k1_scratch_alloc(secp256k1_scratch* scratch, size_t size) {
+static void *secp256k1_scratch_alloc(const secp256k1_callback* error_callback, secp256k1_scratch* scratch, size_t size) {
     void *ret;
-    size_t frame = scratch->frame - 1;
-    size = ((size + ALIGNMENT - 1) / ALIGNMENT) * ALIGNMENT;
+    size = ROUND_TO_ALIGN(size);
+
+    if (memcmp(scratch->magic, "scratch", 8) != 0) {
+        secp256k1_callback_call(error_callback, "invalid scratch space");
+        return NULL;
+    }
 
-    if (scratch->frame == 0 || size + scratch->offset[frame] > scratch->frame_size[frame]) {
+    if (size > scratch->max_size - scratch->alloc_size) {
         return NULL;
     }
-    ret = (void *) ((unsigned char *) scratch->data[frame] + scratch->offset[frame]);
+    ret = (void *) ((char *) scratch->data + scratch->alloc_size);
     memset(ret, 0, size);
-    scratch->offset[frame] += size;
+    scratch->alloc_size += size;
 
     return ret;
 }