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modified post 776ea26 by Anonymous on Mon 15th Aug 2022 20:30
original post 4c6 by Anonymous on Mon 15th Aug 2022 20:30
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/*

1	1		/*
2		-	* custom_c++_operator_new1.cpp - custom allocator demo
	2	+	* custom_c++_operator_new2.cpp - custom allocator demo
3	3		*
4	4		* Written by Roland Mainz <roland.mainz@nrubsig.org>
7	5		*
	6	+	* - Compile with:
8	11		*/
9	12
	13	+	#define USE_STATIC_BUFFER_ALLOC 0
13	16
	17	+	#define STATIC_BUFFER_ALLOC_BUFFER_SIZE (512)
14	18
	19	+	#include <iostream>
15	24		/* required for \|main()\| test/demo code */
16	25		#include <unistd.h>
17	26		#include <stdlib.h>
18	27		#include <stdio.h>
19	28		#include <string.h>
20	29		#include <inttypes.h>
21	30
	31	+	#if USE_TLSF_ALLOC
22	37		/* misc */
23	38		#define STDERR_MSG(msg) \
24	39		(void)write(STDERR_FILENO, (msg), strlen(msg))
25	40
27	41
28	42
29	43		#if USE_STATIC_BUFFER_ALLOC
	44	+	extern "C" {
30	45		static struct
31	46		{
32		-	char buffer[512];
	47	+	char buffer[STATIC_BUFFER_ALLOC_BUFFER_SIZE];
33	48		/* more complex cases would require \|pthread_once()\| */
34	49		char *buf_ptr = buffer;
35	50		} buf_alloc;
36	51
37	52		void *my_buffer_alloc(size_t size)
38	53		{
39	54		#define SIZE_ALIGN(size, align) \
40	55		((size)+((align)-1)-((size)-1)%(align))
41	56
42	57		void *mem;
43	58		size_t bs;
44	59
45	60		STDERR_MSG("my_buffer_alloc\n");
46	61
47	62		bs = SIZE_ALIGN(size, 16);
48	63
49	64		mem = buf_alloc.buf_ptr;
50	65		buf_alloc.buf_ptr += bs;
51	66
52	67		/* could we satisfy the allocation request ? */
53	68		if ((buf_alloc.buf_ptr - buf_alloc.buffer) >= sizeof(buf_alloc.buffer))
54	69		return NULL;
55	70
56		-	#if 1
	71	+	#if 0
57	72		(void)fprintf(stderr, "my_buffer_alloc(size=%ld, bs=%ld, mem=%lx\n",
58	73		(long)size, (long)bs, (long)mem);
59	74		#endif
60	75
61	76		return mem;
62	77		}
63	78
64	79		void my_buffer_dealloc(void *ptr)
65	80		{
66	81		/*
67		-	* range check - pointer must be within \|buf_alloc.buffer\|!
	82	+	* range check - pointer must point within \|buf_alloc.buffer\|!
68	83		*
69	84		* We use this simple (and cheap) check to catch invalid
70	85		* pointers, or (more important) pointers to memory from
71	86		* other allocators (if we mix&match multiple different
72	87		* allocators or different memory pools from the same
73	88		* allocator system).
74	89		*/
75	90		ptrdiff_t x = (char *)ptr - buf_alloc.buffer;
76	91		if ((x < 0) \|\| (x >= (ptrdiff_t)sizeof(buf_alloc.buffer))) {
77	92		/* BUG: LAZY - we should not use stdio here... */
78	93		(void)fprintf(stderr, "delete(): bad pointer %lx!\n", (long)x);
79	94		}
80	95		}
	96	+	} /* extern "C" */
81	97		#endif /* USE_STATIC_BUFFER_ALLOC */
82	98
83	99
84	100		void *
85	101		operator new(std::size_t size)
86	102		// throw(std::bad_alloc)
87	103		{
88	104		STDERR_MSG("##new\n");
89	105		if (size == 0)
90	106		size = 1;
91	107		void* p;
92	108		#if USE_STATIC_BUFFER_ALLOC
93	109		if ((p = my_buffer_alloc(size)) == 0)
	110	+	#elif USE_TLSF_ALLOC
95	113		if ((p = ::malloc(size)) == 0)
	114	+	#else
96	116		#endif /* USE_STATIC_BUFFER_ALLOC */
97	117		{
98	118		throw std::bad_alloc();
99	119		}
100	120		return p;
101	121		}
102	122
103	123
104	124		void
105	125		operator delete(void* ptr) _GLIBCXX_USE_NOEXCEPT
106	126		{
107	127		STDERR_MSG("##delete\n");
108	128		#if USE_STATIC_BUFFER_ALLOC
109	129		my_buffer_dealloc(ptr);
	130	+	#elif USE_TLSF_ALLOC
111	131		if (ptr)
	132	+	::tlsf_free(ptr);
112	135		::free(ptr);
	136	+	#else
113	138		#endif /* USE_STATIC_BUFFER_ALLOC */
114	139		}
115	140
116	141
117	142		/*
118	143		* static variables:
119	144		* Their memory is allocated/constructor called before calling
120	145		* \|main()\|, and their destructor is called and memory deallocated
121	146		* after \|main()\| returned.
122	147		* This causes some nasty headaches for custom \|operator new\|, e.g.
123	148		* in case we want to rely on stdio, C++ iostream, or other
124	149		* libc/libc++ modules. And don't even start to ask about headaches
125		-	* related to STL...
	150	+	* related to STL and C++ exceptions...
126	151		*/
127	152		static int *s_f = new int(59);
128	153
129		-	static std::string s = "xjsdsqwertzuiopasdfghjklöxcvbnm,poiuztrewlkjhgfdmnbvcxjsddljkjklsdfjklsddfljkx";
	154	+	static std::string s = "xjsdsqwertzuiopasdfghjklxcvbnm,poiuztrewlkjhgfdmnbvcxjsddljkjklsdfjklsddfljkx";
130	155
131	156
132	157		int main(int ac, char *av[])
133	158		{
134	159		(void)puts("# >> main:start.");
135	160
136	161		int *f = new int(84);
137	162
138	163
139	164		std::string s = "13123123123122354245234534534534534534656456456456456456242342341233423423524542hello";
140	165		s+=" ";
141	166		s+="world";
142	167
143	168		std::cout << s << "#" << f << "," << s_f << "#" << std::endl;
144	169
145	170		delete f;
146	171
147	172		#if 0
148	173		/* test if pointer validation of \|my_buffer_dealloc()\| works */
149	174		delete (int *)malloc(5);
150	175		#endif
151	176
152	177		(void)puts("# >> main:done.");
153	178		return EXIT_SUCCESS;
154	179		}
155	180