allow reducing surjection proof size (to lower generation stack usage)

include/secp256k1_surjectionproof.h

@@ -12,7 +12,7 @@ extern "C" {
 #define SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS 256
 
 /** Maximum number of inputs that may be used in a surjection proof */
-#define SECP256K1_SURJECTIONPROOF_MAX_USED_INPUTS 16
+#define SECP256K1_SURJECTIONPROOF_MAX_USED_INPUTS 256
 
 /** Number of bytes a serialized surjection proof requires given the
  *  number of inputs and the number of used inputs.
@@ -52,6 +52,7 @@ typedef struct {
     unsigned char data[32 * (1 + SECP256K1_SURJECTIONPROOF_MAX_USED_INPUTS)];
 } secp256k1_surjectionproof;
 
+#ifndef USE_REDUCED_SURJECTION_PROOF_SIZE
 /** Parse a surjection proof
  *
  *  Returns: 1 when the proof could be parsed, 0 otherwise.
@@ -73,6 +74,7 @@ SECP256K1_API int secp256k1_surjectionproof_parse(
   const unsigned char *input,
   size_t inputlen
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+#endif
 
 /** Serialize a surjection proof
  *
@@ -241,6 +243,7 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_surjectionproof_generat
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(5) SECP256K1_ARG_NONNULL(7) SECP256K1_ARG_NONNULL(8);
 
 
+#ifndef USE_REDUCED_SURJECTION_PROOF_SIZE
 /** Surjection proof verification function
  * Returns 0: proof was invalid
  *         1: proof was valid
@@ -258,6 +261,7 @@ SECP256K1_API int secp256k1_surjectionproof_verify(
   size_t n_ephemeral_input_tags,
   const secp256k1_generator* ephemeral_output_tag
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(5);
+#endif
 
 #ifdef __cplusplus
 }