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
43 // Returns whether |ptr| was allocated directly by |a| (so care must be used
44 // with fused arenas).
45 UPB_API bool UPB_ONLYBITS(_upb_Arena_Contains)(const struct upb_Arena* a,
46 void* ptr);
47
UPB_PRIVATE(_upb_ArenaHas)48 UPB_INLINE size_t UPB_PRIVATE(_upb_ArenaHas)(const struct upb_Arena* a) {
49 return (size_t)(a->UPB_ONLYBITS(end) - a->UPB_ONLYBITS(ptr));
50 }
51
upb_Arena_Malloc(struct upb_Arena * a,size_t size)52 UPB_API_INLINE void* upb_Arena_Malloc(struct upb_Arena* a, size_t size) {
53 void* UPB_PRIVATE(_upb_Arena_SlowMalloc)(struct upb_Arena * a, size_t size);
54
55 size = UPB_ALIGN_MALLOC(size);
56 const size_t span = size + UPB_ASAN_GUARD_SIZE;
57 if (UPB_UNLIKELY(UPB_PRIVATE(_upb_ArenaHas)(a) < span)) {
58 return UPB_PRIVATE(_upb_Arena_SlowMalloc)(a, span);
59 }
60
61 // We have enough space to do a fast malloc.
62 void* ret = a->UPB_ONLYBITS(ptr);
63 UPB_ASSERT(UPB_ALIGN_MALLOC((uintptr_t)ret) == (uintptr_t)ret);
64 UPB_ASSERT(UPB_ALIGN_MALLOC(size) == size);
65 UPB_UNPOISON_MEMORY_REGION(ret, size);
66
67 a->UPB_ONLYBITS(ptr) += span;
68
69 return ret;
70 }
71
upb_Arena_Realloc(struct upb_Arena * a,void * ptr,size_t oldsize,size_t size)72 UPB_API_INLINE void* upb_Arena_Realloc(struct upb_Arena* a, void* ptr,
73 size_t oldsize, size_t size) {
74 oldsize = UPB_ALIGN_MALLOC(oldsize);
75 size = UPB_ALIGN_MALLOC(size);
76 bool is_most_recent_alloc =
77 (uintptr_t)ptr + oldsize == (uintptr_t)a->UPB_ONLYBITS(ptr);
78
79 if (is_most_recent_alloc) {
80 ptrdiff_t diff = size - oldsize;
81 if ((ptrdiff_t)UPB_PRIVATE(_upb_ArenaHas)(a) >= diff) {
82 a->UPB_ONLYBITS(ptr) += diff;
83 return ptr;
84 }
85 } else if (size <= oldsize) {
86 return ptr;
87 }
88
89 void* ret = upb_Arena_Malloc(a, size);
90
91 if (ret && oldsize > 0) {
92 memcpy(ret, ptr, UPB_MIN(oldsize, size));
93 }
94
95 return ret;
96 }
97
upb_Arena_ShrinkLast(struct upb_Arena * a,void * ptr,size_t oldsize,size_t size)98 UPB_API_INLINE void upb_Arena_ShrinkLast(struct upb_Arena* a, void* ptr,
99 size_t oldsize, size_t size) {
100 oldsize = UPB_ALIGN_MALLOC(oldsize);
101 size = UPB_ALIGN_MALLOC(size);
102 // Must be the last alloc.
103 UPB_ASSERT((char*)ptr + oldsize ==
104 a->UPB_ONLYBITS(ptr) - UPB_ASAN_GUARD_SIZE);
105 UPB_ASSERT(size <= oldsize);
106 a->UPB_ONLYBITS(ptr) = (char*)ptr + size;
107 }
108
109 #ifdef __cplusplus
110 } /* extern "C" */
111 #endif
112
113 #include "upb/port/undef.inc"
114
115 #endif /* UPB_MEM_INTERNAL_ARENA_H_ */
116