export SECP256K1_SURJECTIONPROOF_RAW_SIZE

include/secp256k1_surjectionproof.h

@@ -33,6 +33,11 @@ extern "C" {
  *  and secp256k1_surjectionproof_serialize to encode/decode proofs into a
  *  well-defined format.
  *
+ *  If you need to allocate new secp256k1_surjectionproof structure
+ *  for use with secp256k1_surjectionproof_initialize, you should allocate
+ *  a buffer of size SECP256K1_SURJECTIONPROOF_RAW_SIZE, and then treat the
+ *  data in this buffer as opaque data, as described above.
+ *
  *  The representation is exposed to allow creation of these objects on the
  *  stack; please *do not* use these internals directly.
  */
@@ -49,6 +54,8 @@ typedef struct {
     unsigned char data[32 * (1 + SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS)];
 } secp256k1_surjectionproof;
 
+SECP256K1_API const int SECP256K1_SURJECTIONPROOF_RAW_SIZE;
+
 /** Parse a surjection proof
  *
  *  Returns: 1 when the proof could be parsed, 0 otherwise.

src/secp256k1.c

@@ -632,4 +632,5 @@ int secp256k1_ec_pubkey_combine(const secp256k1_context* ctx, secp256k1_pubkey *
 
 #ifdef ENABLE_MODULE_SURJECTIONPROOF
 # include "modules/surjection/main_impl.h"
+const int SECP256K1_SURJECTIONPROOF_RAW_SIZE = sizeof(secp256k1_surjectionproof);
 #endif