Move _preallocated functions to separate header

Makefile.am

@@ -8,6 +8,7 @@ else
 JNI_LIB =
 endif
 include_HEADERS = include/secp256k1.h
+include_HEADERS += include/secp256k1_preallocated.h
 noinst_HEADERS =
 noinst_HEADERS += src/scalar.h
 noinst_HEADERS += src/scalar_4x64.h

include/secp256k1.h

@@ -191,7 +191,8 @@ SECP256K1_API extern const secp256k1_context *secp256k1_context_no_precomp;
 /** Create a secp256k1 context object (in dynamically allocated memory).
  *
  *  This function uses malloc to allocate memory. It is guaranteed that malloc is
- *  called at most once for every call of this function.
+ *  called at most once for every call of this function. If you need to avoid dynamic
+ *  memory allocation entirely, see the functions in secp256k1_preallocated.h.
  *
  *  Returns: a newly created context object.
  *  In:      flags: which parts of the context to initialize.
@@ -205,7 +206,8 @@ SECP256K1_API secp256k1_context* secp256k1_context_create(
 /** Copy a secp256k1 context object (into dynamically allocated memory).
  *
  *  This function uses malloc to allocate memory. It is guaranteed that malloc is
- *  called at most once for every call of this function.
+ *  called at most once for every call of this function. If you need to avoid dynamic
+ *  memory allocation entirely, see the functions in secp256k1_preallocated.h.
  *
  *  Returns: a newly created context object.
  *  Args:    ctx: an existing context to copy (cannot be NULL)
@@ -230,81 +232,6 @@ SECP256K1_API secp256k1_context* secp256k1_context_clone(
 SECP256K1_API void secp256k1_context_destroy(
     secp256k1_context* ctx
 );
-/** Determine the memory size of a secp256k1 context object to be created in
- *  caller-provided memory.
- *
- *  The purpose of this function is to determine how much memory must be provided
- *  to secp256k1_context_preallocated_create.
- *
- *  Returns: the required size of the caller-provided memory block
- *  In:      flags:    which parts of the context to initialize.
- */
-
-SECP256K1_API size_t secp256k1_context_preallocated_size(
-    unsigned int flags
-) SECP256K1_WARN_UNUSED_RESULT;
-
-/** Create a secp256k1 context object in caller-provided memory.
- *
- *  Returns: a newly created context object.
- *  In:      prealloc: a pointer to a rewritable contiguous block of memory of
- *                     size at least secp256k1_context_preallocated_size(flags)
- *                     bytes, suitably aligned to hold an object of any type
- *                     (cannot be NULL)
- *           flags:    which parts of the context to initialize.
- *
- *  See also secp256k1_context_randomize.
- */
-SECP256K1_API secp256k1_context* secp256k1_context_preallocated_create(
-    void* prealloc,
-    unsigned int flags
-) SECP256K1_ARG_NONNULL(1) SECP256K1_WARN_UNUSED_RESULT;
-
-/** Determine the memory size of a secp256k1 context object to be copied into
- *  caller-provided memory.
- *
- *  The purpose of this function is to determine how much memory must be provided
- *  to secp256k1_context_preallocated_clone when copying the context ctx.
- *
- *  Returns: the required size of the caller-provided memory block.
- *  In:      ctx: an existing context to copy (cannot be NULL)
- */
-SECP256K1_API size_t secp256k1_context_preallocated_clone_size(
-    const secp256k1_context* ctx
-) SECP256K1_ARG_NONNULL(1) SECP256K1_WARN_UNUSED_RESULT;
-
-/** Copy a secp256k1 context object into caller-provided memory.
- *
- *  Returns: a newly created context object.
- *  Args:    ctx:      an existing context to copy (cannot be NULL)
- *  In:      prealloc: a pointer to a rewritable contiguous block of memory of
- *                     size at least secp256k1_context_preallocated_size(flags)
- *                     bytes, suitably aligned to hold an object of any type
- *                     (cannot be NULL)
- */
-SECP256K1_API secp256k1_context* secp256k1_context_preallocated_clone(
-    const secp256k1_context* ctx,
-    void* prealloc
-) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_WARN_UNUSED_RESULT;
-
-/** Destroy a secp256k1 context object that has been created in
- *  caller-provided memory.
- *
- *  The context pointer may not be used afterwards.
- *
- *  The context to destroy must have been created using
- *  secp256k1_context_preallocated_create or secp256k1_context_preallocated_clone.
- *  If the context has instead been created using secp256k1_context_create or
- *  secp256k1_context_clone, the behaviour is undefined. In that case,
- *  secp256k1_context_destroy must be used instead.
- *
- *  Args:   ctx: an existing context to destroy, constructed using
- *               secp256k1_context_preallocated_create or
- *               secp256k1_context_preallocated_clone (cannot be NULL)
- */
-SECP256K1_API void secp256k1_context_preallocated_destroy(
-    secp256k1_context* ctx
-);
 
 /** Set a callback function to be called when an illegal argument is passed to
  *  an API call. It will only trigger for violations that are mentioned

include/secp256k1_preallocated.h

@@ -0,0 +1,98 @@
+#ifndef SECP256K1_PREALLOCATED_H
+#define SECP256K1_PREALLOCATED_H
+
+#include "secp256k1.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* The module provided by this header file is intended for settings in which it
+ * is not possible or desirable to rely on dynamic memory allocation. It provides
+ * functions for creating, cloning, and destroying secp256k1 context objects in a
+ * contiguous fixed-size block of memory provided by the caller.
+ *
+ * It is guaranteed that functions in this module will not call malloc or its
+ * friends realloc, calloc, and free.
+ */
+
+/** Determine the memory size of a secp256k1 context object to be created in
+ *  caller-provided memory.
+ *
+ *  The purpose of this function is to determine how much memory must be provided
+ *  to secp256k1_context_preallocated_create.
+ *
+ *  Returns: the required size of the caller-provided memory block
+ *  In:      flags:    which parts of the context to initialize.
+ */
+SECP256K1_API size_t secp256k1_context_preallocated_size(
+    unsigned int flags
+) SECP256K1_WARN_UNUSED_RESULT;
+
+/** Create a secp256k1 context object in caller-provided memory.
+ *
+ *  Returns: a newly created context object.
+ *  In:      prealloc: a pointer to a rewritable contiguous block of memory of
+ *                     size at least secp256k1_context_preallocated_size(flags)
+ *                     bytes, suitably aligned to hold an object of any type
+ *                     (cannot be NULL)
+ *           flags:    which parts of the context to initialize.
+ *
+ *  See also secp256k1_context_randomize.
+ */
+SECP256K1_API secp256k1_context* secp256k1_context_preallocated_create(
+    void* prealloc,
+    unsigned int flags
+) SECP256K1_ARG_NONNULL(1) SECP256K1_WARN_UNUSED_RESULT;
+
+/** Determine the memory size of a secp256k1 context object to be copied into
+ *  caller-provided memory.
+ *
+ *  The purpose of this function is to determine how much memory must be provided
+ *  to secp256k1_context_preallocated_clone when copying the context ctx.
+ *
+ *  Returns: the required size of the caller-provided memory block.
+ *  In:      ctx: an existing context to copy (cannot be NULL)
+ */
+SECP256K1_API size_t secp256k1_context_preallocated_clone_size(
+    const secp256k1_context* ctx
+) SECP256K1_ARG_NONNULL(1) SECP256K1_WARN_UNUSED_RESULT;
+
+/** Copy a secp256k1 context object into caller-provided memory.
+ *
+ *  Returns: a newly created context object.
+ *  Args:    ctx:      an existing context to copy (cannot be NULL)
+ *  In:      prealloc: a pointer to a rewritable contiguous block of memory of
+ *                     size at least secp256k1_context_preallocated_size(flags)
+ *                     bytes, suitably aligned to hold an object of any type
+ *                     (cannot be NULL)
+ */
+SECP256K1_API secp256k1_context* secp256k1_context_preallocated_clone(
+    const secp256k1_context* ctx,
+    void* prealloc
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_WARN_UNUSED_RESULT;
+
+/** Destroy a secp256k1 context object that has been created in
+ *  caller-provided memory.
+ *
+ *  The context pointer may not be used afterwards.
+ *
+ *  The context to destroy must have been created using
+ *  secp256k1_context_preallocated_create or secp256k1_context_preallocated_clone.
+ *  If the context has instead been created using secp256k1_context_create or
+ *  secp256k1_context_clone, the behaviour is undefined. In that case,
+ *  secp256k1_context_destroy must be used instead.
+ *
+ *  Args:   ctx: an existing context to destroy, constructed using
+ *               secp256k1_context_preallocated_create or
+ *               secp256k1_context_preallocated_clone (cannot be NULL)
+ */
+SECP256K1_API void secp256k1_context_preallocated_destroy(
+    secp256k1_context* ctx
+);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SECP256K1_PREALLOCATED_H */

src/secp256k1.c

@@ -5,6 +5,7 @@
  **********************************************************************/
 
 #include "include/secp256k1.h"
+#include "include/secp256k1_preallocated.h"
 
 #include "util.h"
 #include "num_impl.h"

src/tests.c

@@ -16,6 +16,7 @@
 
 #include "secp256k1.c"
 #include "include/secp256k1.h"
+#include "include/secp256k1_preallocated.h"
 #include "testrand_impl.h"
 
 #ifdef ENABLE_OPENSSL_TESTS