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39
40 #include "qplatformdefs.h"
41
42 #include <stdlib.h>
43 #include <string.h>
44
45 /*
46 Define the container allocation functions in a separate file, so that our
47 users can easily override them.
48 */
49
50 QT_BEGIN_NAMESPACE
51
52 #if !QT_DEPRECATED_SINCE(5, 0)
53 // Make sure they're defined to be exported
54 Q_CORE_EXPORT void *qMalloc(size_t size) Q_ALLOC_SIZE(1);
55 Q_CORE_EXPORT void qFree(void *ptr);
56 Q_CORE_EXPORT void *qRealloc(void *ptr, size_t size) Q_ALLOC_SIZE(2);
57 #endif
58
59
qMalloc(size_t size)60 void *qMalloc(size_t size)
61 {
62 return ::malloc(size);
63 }
64
qFree(void * ptr)65 void qFree(void *ptr)
66 {
67 ::free(ptr);
68 }
69
qRealloc(void * ptr,size_t size)70 void *qRealloc(void *ptr, size_t size)
71 {
72 return ::realloc(ptr, size);
73 }
74
qMallocAligned(size_t size,size_t alignment)75 void *qMallocAligned(size_t size, size_t alignment)
76 {
77 return qReallocAligned(nullptr, size, 0, alignment);
78 }
79
qReallocAligned(void * oldptr,size_t newsize,size_t oldsize,size_t alignment)80 void *qReallocAligned(void *oldptr, size_t newsize, size_t oldsize, size_t alignment)
81 {
82 // fake an aligned allocation
83 void *actualptr = oldptr ? static_cast<void **>(oldptr)[-1] : nullptr;
84 if (alignment <= sizeof(void*)) {
85 // special, fast case
86 void **newptr = static_cast<void **>(realloc(actualptr, newsize + sizeof(void*)));
87 if (!newptr)
88 return nullptr;
89 if (newptr == actualptr) {
90 // realloc succeeded without reallocating
91 return oldptr;
92 }
93
94 *newptr = newptr;
95 return newptr + 1;
96 }
97
98 // malloc returns pointers aligned at least at sizeof(size_t) boundaries
99 // but usually more (8- or 16-byte boundaries).
100 // So we overallocate by alignment-sizeof(size_t) bytes, so we're guaranteed to find a
101 // somewhere within the first alignment-sizeof(size_t) that is properly aligned.
102
103 // However, we need to store the actual pointer, so we need to allocate actually size +
104 // alignment anyway.
105
106 void *real = realloc(actualptr, newsize + alignment);
107 if (!real)
108 return nullptr;
109
110 quintptr faked = reinterpret_cast<quintptr>(real) + alignment;
111 faked &= ~(alignment - 1);
112 void **faked_ptr = reinterpret_cast<void **>(faked);
113
114 if (oldptr) {
115 qptrdiff oldoffset = static_cast<char *>(oldptr) - static_cast<char *>(actualptr);
116 qptrdiff newoffset = reinterpret_cast<char *>(faked_ptr) - static_cast<char *>(real);
117 if (oldoffset != newoffset)
118 memmove(faked_ptr, static_cast<char *>(real) + oldoffset, qMin(oldsize, newsize));
119 }
120
121 // now save the value of the real pointer at faked-sizeof(void*)
122 // by construction, alignment > sizeof(void*) and is a power of 2, so
123 // faked-sizeof(void*) is properly aligned for a pointer
124 faked_ptr[-1] = real;
125
126 return faked_ptr;
127 }
128
qFreeAligned(void * ptr)129 void qFreeAligned(void *ptr)
130 {
131 if (!ptr)
132 return;
133 void **ptr2 = static_cast<void **>(ptr);
134 free(ptr2[-1]);
135 }
136
137 QT_END_NAMESPACE
138
139