Merge bitcoin-core/secp256k1#1305: Remove unused scratch space from API

712e7f8 Remove unused scratch space from API (Jonas Nick)

Pull request description:

  Not sure if we want the typedef and `secp256k1_scratch_space_{create,destroy}` but if we don't keep them then this PR will be a rather large diff.

ACKs for top commit:
  sipa:
    ACK 712e7f8
  real-or-random:
    utACK 712e7f8

Tree-SHA512: b3a8feb0fe4639d5e48b708ccbf355bca5da658a291f63899086d2bbeb6d0ab33e3dcd55d8984ec7fa803f757b7d02e71bcb7e7eeecaab52ffc70ae85dce8c44

Author: real-or-random

include/secp256k1.h

@@ -49,19 +49,6 @@ extern "C" {
  */
 typedef struct secp256k1_context_struct secp256k1_context;
 
-/** Opaque data structure that holds rewritable "scratch space"
- *
- *  The purpose of this structure is to replace dynamic memory allocations,
- *  because we target architectures where this may not be available. It is
- *  essentially a resizable (within specified parameters) block of bytes,
- *  which is initially created either by memory allocation or TODO as a pointer
- *  into some fixed rewritable space.
- *
- *  Unlike the context object, this cannot safely be shared between threads
- *  without additional synchronization logic.
- */
-typedef struct secp256k1_scratch_space_struct secp256k1_scratch_space;
-
 /** Opaque data structure that holds a parsed and valid public key.
  *
  *  The exact representation of data inside is implementation defined and not
@@ -385,29 +372,6 @@ SECP256K1_API void secp256k1_context_set_error_callback(
     const void *data
 ) SECP256K1_ARG_NONNULL(1);
 
-/** Create a secp256k1 scratch space object.
- *
- *  Returns: a newly created scratch space.
- *  Args: ctx:  an existing context object.
- *  In:   size: amount of memory to be available as scratch space. Some extra
- *              (<100 bytes) will be allocated for extra accounting.
- */
-SECP256K1_API SECP256K1_WARN_UNUSED_RESULT secp256k1_scratch_space *secp256k1_scratch_space_create(
-    const secp256k1_context *ctx,
-    size_t size
-) SECP256K1_ARG_NONNULL(1);
-
-/** Destroy a secp256k1 scratch space.
- *
- *  The pointer may not be used afterwards.
- *  Args:       ctx: a secp256k1 context object.
- *          scratch: space to destroy
- */
-SECP256K1_API void secp256k1_scratch_space_destroy(
-    const secp256k1_context *ctx,
-    secp256k1_scratch_space *scratch
-) SECP256K1_ARG_NONNULL(1);
-
 /** Parse a variable-length public key into the pubkey object.
  *
  *  Returns: 1 if the public key was fully valid.

src/scratch.h

@@ -21,6 +21,8 @@ typedef struct secp256k1_scratch_space_struct {
     size_t max_size;
 } secp256k1_scratch;
 
+typedef struct secp256k1_scratch_space_struct secp256k1_scratch_space;
+
 static secp256k1_scratch* secp256k1_scratch_create(const secp256k1_callback* error_callback, size_t max_size);
 
 static void secp256k1_scratch_destroy(const secp256k1_callback* error_callback, secp256k1_scratch* scratch);

src/secp256k1.c

@@ -219,12 +219,12 @@ void secp256k1_context_set_error_callback(secp256k1_context* ctx, void (*fun)(co
     ctx->error_callback.data = data;
 }
 
-secp256k1_scratch_space* secp256k1_scratch_space_create(const secp256k1_context* ctx, size_t max_size) {
+static secp256k1_scratch_space* secp256k1_scratch_space_create(const secp256k1_context* ctx, size_t max_size) {
     VERIFY_CHECK(ctx != NULL);
     return secp256k1_scratch_create(&ctx->error_callback, max_size);
 }
 
-void secp256k1_scratch_space_destroy(const secp256k1_context *ctx, secp256k1_scratch_space* scratch) {
+static void secp256k1_scratch_space_destroy(const secp256k1_context *ctx, secp256k1_scratch_space* scratch) {
     VERIFY_CHECK(ctx != NULL);
     secp256k1_scratch_destroy(&ctx->error_callback, scratch);
 }