1 // Protocol Buffers - Google's data interchange format
2 // Copyright 2023 Google LLC. All rights reserved.
3 //
4 // Use of this source code is governed by a BSD-style
5 // license that can be found in the LICENSE file or at
6 // https://developers.google.com/open-source/licenses/bsd
7
8 #ifndef UPB_MEM_INTERNAL_ARENA_H_
9 #define UPB_MEM_INTERNAL_ARENA_H_
10
11 #include <stddef.h>
12 #include <stdint.h>
13 #include <string.h>
14
15 // Must be last.
16 #include "upb/port/def.inc"
17
18 // This is QUITE an ugly hack, which specifies the number of pointers needed
19 // to equal (or exceed) the storage required for one upb_Arena.
20 //
21 // We need this because the decoder inlines a upb_Arena for performance but
22 // the full struct is not visible outside of arena.c. Yes, I know, it's awful.
23 #define UPB_ARENA_SIZE_HACK 7
24
25 // LINT.IfChange(upb_Arena)
26
27 struct upb_Arena {
28 char* UPB_ONLYBITS(ptr);
29 char* UPB_ONLYBITS(end);
30 };
31
32 // LINT.ThenChange(//depot/google3/third_party/upb/bits/typescript/arena.ts:upb_Arena)
33
34 #ifdef __cplusplus
35 extern "C" {
36 #endif
37
38 void UPB_PRIVATE(_upb_Arena_SwapIn)(struct upb_Arena* des,
39 const struct upb_Arena* src);
40 void UPB_PRIVATE(_upb_Arena_SwapOut)(struct upb_Arena* des,
41 const struct upb_Arena* src);
42
UPB_PRIVATE(_upb_ArenaHas)43 UPB_INLINE size_t UPB_PRIVATE(_upb_ArenaHas)(const struct upb_Arena* a) {
44 return (size_t)(a->UPB_ONLYBITS(end) - a->UPB_ONLYBITS(ptr));
45 }
46
UPB_PRIVATE(_upb_Arena_Malloc)47 UPB_INLINE void* UPB_PRIVATE(_upb_Arena_Malloc)(struct upb_Arena* a,
48 size_t size) {
49 void* UPB_PRIVATE(_upb_Arena_SlowMalloc)(struct upb_Arena * a, size_t size);
50
51 size = UPB_ALIGN_MALLOC(size);
52 const size_t span = size + UPB_ASAN_GUARD_SIZE;
53 if (UPB_UNLIKELY(UPB_PRIVATE(_upb_ArenaHas)(a) < span)) {
54 return UPB_PRIVATE(_upb_Arena_SlowMalloc)(a, span);
55 }
56
57 // We have enough space to do a fast malloc.
58 void* ret = a->UPB_ONLYBITS(ptr);
59 UPB_ASSERT(UPB_ALIGN_MALLOC((uintptr_t)ret) == (uintptr_t)ret);
60 UPB_ASSERT(UPB_ALIGN_MALLOC(size) == size);
61 UPB_UNPOISON_MEMORY_REGION(ret, size);
62
63 a->UPB_ONLYBITS(ptr) += span;
64
65 return ret;
66 }
67
UPB_PRIVATE(_upb_Arena_Realloc)68 UPB_INLINE void* UPB_PRIVATE(_upb_Arena_Realloc)(struct upb_Arena* a, void* ptr,
69 size_t oldsize, size_t size) {
70 oldsize = UPB_ALIGN_MALLOC(oldsize);
71 size = UPB_ALIGN_MALLOC(size);
72 bool is_most_recent_alloc =
73 (uintptr_t)ptr + oldsize == (uintptr_t)a->UPB_ONLYBITS(ptr);
74
75 if (is_most_recent_alloc) {
76 ptrdiff_t diff = size - oldsize;
77 if ((ptrdiff_t)UPB_PRIVATE(_upb_ArenaHas)(a) >= diff) {
78 a->UPB_ONLYBITS(ptr) += diff;
79 return ptr;
80 }
81 } else if (size <= oldsize) {
82 return ptr;
83 }
84
85 void* ret = UPB_PRIVATE(_upb_Arena_Malloc)(a, size);
86
87 if (ret && oldsize > 0) {
88 memcpy(ret, ptr, UPB_MIN(oldsize, size));
89 }
90
91 return ret;
92 }
93
UPB_PRIVATE(_upb_Arena_ShrinkLast)94 UPB_INLINE void UPB_PRIVATE(_upb_Arena_ShrinkLast)(struct upb_Arena* a,
95 void* ptr, size_t oldsize,
96 size_t size) {
97 oldsize = UPB_ALIGN_MALLOC(oldsize);
98 size = UPB_ALIGN_MALLOC(size);
99 // Must be the last alloc.
100 UPB_ASSERT((char*)ptr + oldsize ==
101 a->UPB_ONLYBITS(ptr) - UPB_ASAN_GUARD_SIZE);
102 UPB_ASSERT(size <= oldsize);
103 a->UPB_ONLYBITS(ptr) = (char*)ptr + size;
104 }
105
106 #ifdef __cplusplus
107 } /* extern "C" */
108 #endif
109
110 #include "upb/port/undef.inc"
111
112 #endif /* UPB_MEM_INTERNAL_ARENA_H_ */
113