Inside Bitcoin

1#ifndef SECP256K1_PREALLOCATED_H
2#define SECP256K1_PREALLOCATED_H
3
4#include "secp256k1.h"
5
6#ifdef __cplusplus
7extern "C" {
8#endif
9
10/* The module provided by this header file is intended for settings in which it
11 * is not possible or desirable to rely on dynamic memory allocation. It provides
12 * functions for creating, cloning, and destroying secp256k1 context objects in a
13 * contiguous fixed-size block of memory provided by the caller.
14 *
15 * Context objects created by functions in this module can be used like contexts
16 * objects created by functions in secp256k1.h, i.e., they can be passed to any
17 * API function that expects a context object (see secp256k1.h for details). The
18 * only exception is that context objects created by functions in this module
19 * must be destroyed using secp256k1_context_preallocated_destroy (in this
20 * module) instead of secp256k1_context_destroy (in secp256k1.h).
21 *
22 * It is guaranteed that functions in this module will not call malloc or its
23 * friends realloc, calloc, and free.
24 */
25
26/** Determine the memory size of a secp256k1 context object to be created in
27 *  caller-provided memory.
28 *
29 *  The purpose of this function is to determine how much memory must be provided
30 *  to secp256k1_context_preallocated_create.
31 *
32 *  Returns: the required size of the caller-provided memory block
33 *  In:      flags:    which parts of the context to initialize.
34 */
35SECP256K1_API size_t secp256k1_context_preallocated_size(
36    unsigned int flags
37) SECP256K1_WARN_UNUSED_RESULT;
38
39/** Create a secp256k1 context object in caller-provided memory.
40 *
41 *  The caller must provide a pointer to a rewritable contiguous block of memory
42 *  of size at least secp256k1_context_preallocated_size(flags) bytes, suitably
43 *  aligned to hold an object of any type.
44 *
45 *  The block of memory is exclusively owned by the created context object during
46 *  the lifetime of this context object, which begins with the call to this
47 *  function and ends when a call to secp256k1_context_preallocated_destroy
48 *  (which destroys the context object again) returns. During the lifetime of the
49 *  context object, the caller is obligated not to access this block of memory,
50 *  i.e., the caller may not read or write the memory, e.g., by copying the memory
51 *  contents to a different location or trying to create a second context object
52 *  in the memory. In simpler words, the prealloc pointer (or any pointer derived
53 *  from it) should not be used during the lifetime of the context object.
54 *
55 *  Returns: pointer to newly created context object.
56 *  In:      prealloc: pointer to a rewritable contiguous block of memory of
57 *                     size at least secp256k1_context_preallocated_size(flags)
58 *                     bytes, as detailed above.
59 *           flags:    which parts of the context to initialize.
60 *
61 *  See secp256k1_context_create (in secp256k1.h) for further details.
62 *
63 *  See also secp256k1_context_randomize (in secp256k1.h)
64 *  and secp256k1_context_preallocated_destroy.
65 */
66SECP256K1_API secp256k1_context *secp256k1_context_preallocated_create(
67    void *prealloc,
68    unsigned int flags
69) SECP256K1_ARG_NONNULL(1) SECP256K1_WARN_UNUSED_RESULT;
70
71/** Determine the memory size of a secp256k1 context object to be copied into
72 *  caller-provided memory.
73 *
74 *  Returns: the required size of the caller-provided memory block.
75 *  In:      ctx: pointer to a context to copy.
76 */
77SECP256K1_API size_t secp256k1_context_preallocated_clone_size(
78    const secp256k1_context *ctx
79) SECP256K1_ARG_NONNULL(1) SECP256K1_WARN_UNUSED_RESULT;
80
81/** Copy a secp256k1 context object into caller-provided memory.
82 *
83 *  The caller must provide a pointer to a rewritable contiguous block of memory
84 *  of size at least secp256k1_context_preallocated_size(flags) bytes, suitably
85 *  aligned to hold an object of any type.
86 *
87 *  The block of memory is exclusively owned by the created context object during
88 *  the lifetime of this context object, see the description of
89 *  secp256k1_context_preallocated_create for details.
90 *
91 *  Cloning secp256k1_context_static is not possible, and should not be emulated by
92 *  the caller (e.g., using memcpy). Create a new context instead.
93 *
94 *  Returns: pointer to a newly created context object.
95 *  Args:    ctx:      pointer to a context to copy (not secp256k1_context_static).
96 *  In:      prealloc: pointer to a rewritable contiguous block of memory of
97 *                     size at least secp256k1_context_preallocated_size(flags)
98 *                     bytes, as detailed above.
99 */
100SECP256K1_API secp256k1_context *secp256k1_context_preallocated_clone(
101    const secp256k1_context *ctx,
102    void *prealloc
103) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_WARN_UNUSED_RESULT;
104
105/** Destroy a secp256k1 context object that has been created in
106 *  caller-provided memory.
107 *
108 *  The context pointer may not be used afterwards.
109 *
110 *  The context to destroy must have been created using
111 *  secp256k1_context_preallocated_create or secp256k1_context_preallocated_clone.
112 *  If the context has instead been created using secp256k1_context_create or
113 *  secp256k1_context_clone, the behaviour is undefined. In that case,
114 *  secp256k1_context_destroy must be used instead.
115 *
116 *  If required, it is the responsibility of the caller to deallocate the block
117 *  of memory properly after this function returns, e.g., by calling free on the
118 *  preallocated pointer given to secp256k1_context_preallocated_create or
119 *  secp256k1_context_preallocated_clone.
120 *
121 *  Args:   ctx: pointer to a context to destroy, constructed using
122 *               secp256k1_context_preallocated_create or
123 *               secp256k1_context_preallocated_clone
124 *               (i.e., not secp256k1_context_static).
125 */
126SECP256K1_API void secp256k1_context_preallocated_destroy(
127    secp256k1_context *ctx
128) SECP256K1_ARG_NONNULL(1);
129
130#ifdef __cplusplus
131}
132#endif
133
134#endif /* SECP256K1_PREALLOCATED_H */
135