5 Author: Pekka Riikonen <priikone@silcnet.org>
7 Copyright (C) 2003 - 2007 Pekka Riikonen
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; version 2 of the License.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
20 /****h* silcutil/SilcStack Interface
24 * Implementation of data stack which can be used to allocate memory from
25 * the stack. Basically SilcStack is a pre-allocated memory pool system
26 * which allows fast memory allocation for routines and applications that
27 * frequently allocate small amounts of memory. Other advantage of this
28 * system is that there are no memory leaks, as long as the stack is
29 * freed eventually. Since the stack is usually allocated only once this
32 * SilcStack supports stack pushing and popping allowing to push the stack,
33 * allocate memory and then pop it to free the allocated memory. The freeing
34 * does not actually do any real memory freeing so it is optimized for
35 * performance. The memory alignment may also be specified by user for
36 * the stack. This allows the caller to use special alignment for memory
37 * allocations, if needed.
39 * SilcStack is also a full featured memory pool which allows user to group
40 * together multiple stacks. Child stacks may be created from a parent stack
41 * without consuming the parent stack. When the child is freed, its memory
42 * is returned back to the parent and can be used again by other childs.
43 * It is also possible to create child stacks from another child stack.
45 * A basic set of utility functions are provided for application that wish
46 * to use the SilcStack as their primary memory allocation source. The
47 * following functions support SilcStack:
49 * silc_smalloc, silc_smalloc, silc_scalloc, silc_srealloc, silc_smemdup,
50 * silc_sfree, silc_sstrdup, silc_buffer_salloc, silc_buffer_salloc_size,
51 * silc_buffer_srealloc, silc_buffer_srealloc_size, silc_buffer_scopy,
52 * silc_buffer_sclone, silc_buffer_sformat, silc_buffer_sformat_vp,
53 * silc_buffer_sstrformat, silc_buffer_senlarge, silc_mp_sinit,
54 * silc_dlist_sinit, silc_hash_table_alloc
56 * The SilcStack is not thread-safe so that same context could be used for
57 * allocations from multiple threads. It is however safe to create and use
58 * child stacks in a different thread from the parent stack. Each thread
59 * should allocate their own SilcStack, however they may be child stacks.
66 /****s* silcutil/SilcStackAPI/SilcStack
70 * typedef struct SilcStackStruct *SilcStack;
74 * This context represents the stack and it is allocated by
75 * silc_stack_alloc and is destroyed with silc_stack_free functions.
76 * The context is given as argument to all routines that use this
77 * stack allocation library.
80 typedef struct SilcStackStruct *SilcStack;
82 /****s* silcutil/SilcStackAPI/SilcStackFrame
86 * typedef struct SilcStackFrameStruct SilcStackFrame;
90 * Static stack frame context that optionally can be used as stack
91 * frame in SilcStack. By default silc_stack_push use pre-allocated
92 * stack frame, but user may also use statically allocated SilcStackFrame
93 * instead. This is recommended when using SilcStack in recursive routine
94 * and the recursion may become deep. Using static frame assures that
95 * during recursion frames never run out.
98 typedef struct SilcStackFrameStruct SilcStackFrame;
100 /****f* silcutil/SilcStackAPI/SilcStackOomHandler
104 * typedef void (*SilcStackOomHandler)(SilcStack stack, void *context);
108 * Callback of this type can be given to silc_stack_set_oom_handler
109 * to set Out of Memory handler to `stack'. If memory allocation from
110 * `stack' fails this callback is called to indicate error. The `context'
111 * is the context given to silc_stack_set_oom_handler.
114 typedef void (*SilcStackOomHandler)(SilcStack stack, void *context);
116 /****f* silcutil/SilcStackAPI/silc_stack_alloc
120 * SilcStack silc_stack_alloc(SilcUInt32 stack_size, SilcStack parent);
124 * Allocates new data stack that can be used as stack for fast memory
125 * allocation by various routines. Returns the pointer to the stack
126 * that must be freed with silc_stack_free function when it is not
127 * needed anymore. If the `stack_size' is zero (0) by default a
128 * 1 kilobyte (1024 bytes) stack is allocated. If the `stack_size'
129 * is non-zero the byte value must be multiple by 8.
131 * If `parent' is non-NULL the created stack is a child of the `parent'
132 * stack. All of childs the memory is allocated from the `parent' and
133 * will be returned back to the parent when the child is freed. Note
134 * that, even though child allocates memory from the parent, the parent's
135 * stack is not consumed.
137 * Returns NULL on error.
140 SilcStack silc_stack_alloc(SilcUInt32 stack_size, SilcStack parent);
142 /****f* silcutil/SilcStackAPI/silc_stack_free
146 * void silc_stack_free(SilcStack stack);
150 * Frees the data stack context. The stack cannot be used anymore after
151 * this and all allocated memory are freed.
153 * If `stack' is a child stack, its memory is returned back to its
154 * parent. If `stack' is NULL this function does nothing.
157 void silc_stack_free(SilcStack stack);
159 /****f* silcutil/SilcStackAPI/silc_stack_push
163 * SilcUInt32 silc_stack_push(SilcStack stack, SilcStackFrame *frame);
167 * Push the top of the stack down which becomes the new top of the stack.
168 * For every silc_stack_push call there must be silc_stack_pop call. All
169 * allocations between these two calls will be done from the top of the
170 * stack and all allocated memory is freed after the next silc_stack_pop
171 * is called. This returns so called stack pointer for the new stack
172 * frame, which the caller may use to check that all calls to
173 * silc_stack_pop has been made.
175 * If the `frame' is non-NULL then that SilcStackFrame is used as
176 * stack frame. Usually `frame' is set to NULL by user. Statically
177 * allocated SilcStackFrame should be used when using silc_stack_push
178 * in recursive function and the recursion may become deep. In this
179 * case using statically allocated SilcStackFrame is recommended since
180 * it assures that frames never run out. If your routine is not recursive
181 * then setting `frame' to NULL is recommended.
183 * This function is used when a routine is doing frequent allocations
184 * from the stack. If the stack is not pushed and later popped all
185 * allocations are made from the stack and the stack eventually runs out
186 * (it gets enlarged by normal memory allocation). By pushing and then
187 * later popping the frequent allocations does not consume the stack.
189 * If `stack' is NULL this call has no effect. This function does not
190 * allocate any memory.
194 * All memory allocations in silc_foo_parse_packet will be done in
195 * a fresh stack frame and that data is freed after the parsing is
198 * silc_stack_push(stack, NULL);
199 * silc_foo_parse_packet(packet, stack);
200 * silc_stack_pop(stack);
202 * Another example with recursion and using statically allocated
203 * SilcStackFrame. After popping the statically allocated frame can
204 * be reused if necessary.
206 * void silc_foo_this_function(SilcStack stack)
208 * SilcStackFrame frame;
210 * silc_stack_push(stack, &frame);
211 * silc_foo_this_function(stack); // Call recursively
212 * silc_stack_pop(stack);
217 SilcUInt32 silc_stack_push(SilcStack stack, SilcStackFrame *frame);
219 /****f* silcutil/SilcStackAPI/silc_stack_pop
223 * SilcUInt32 silc_stack_pop(SilcStack stack);
227 * Pop the top of the stack which removes the previous stack frame and
228 * becomes the top of the stack. After popping, memory allocated in
229 * the old frame is freed. For each silc_stack_push call there must be
230 * silc_stack_pop call to free all memory (in reality any memory is not
231 * freed but within the stack it is). This returns the stack pointer of
232 * old frame after popping and caller may check that it is same as
233 * returned by the silc_stack_push. If it they differ, some routine
234 * has called silc_stack_push but has not called silc_stack_pop, or
235 * silc_stack_pop has been called too many times. Application should
236 * treat this as a fatal error, as it is a bug in the application code.
238 * If `stack' is NULL this call has no effect. This function does not
239 * allocate any memory.
243 * This example saves the stack pointer which is checked when popping
244 * the current stack frame. If the stack pointer differs then someone
245 * has pushed the stack frame but forgot to pop it (or has called it
248 * sp = silc_stack_push(stack, NULL);
249 * silc_foo_parse_packet(packet, stack);
250 * if (silc_stack_pop(stack) != sp)
251 * fatal("corrupted stack");
254 SilcUInt32 silc_stack_pop(SilcStack stack);
256 /****f* silcutil/SilcStackAPI/silc_stack_malloc
260 * void *silc_stack_malloc(SilcStack stack, SilcUInt32 size);
264 * Low level memory allocation routine. Allocates memory block of size of
265 * `size' from the `stack'. The allocated memory is aligned so it can be
266 * used to allocate memory for structures, for example. Returns the
267 * allocated memory address or NULL if memory could not be allocated from
272 * This function should be used only if low level memory allocation with
273 * SilcStack is needed. Instead, silc_smalloc and silc_scalloc could
277 void *silc_stack_malloc(SilcStack stack, SilcUInt32 size);
279 /****f* silcutil/SilcStackAPI/silc_stack_realloc
283 * void *silc_stack_realloc(SilcStack stack, SilcUInt32 old_size,
284 * *void *ptr, SilcUInt32 size);
288 * Attempts to reallocate memory by changing the size of the `ptr' into
289 * `size'. This routine works only if the previous allocation to `stack'
290 * was `ptr'. If there is another memory allocation between allocating
291 * `ptr' and this call this routine will return NULL. NULL is also
292 * returned if the `size' does not fit into the current stack block.
293 * If NULL is returned the old memory remains intact.
297 * This function should be used only if low level memory allocation with
298 * SilcStack is needed. Instead, silc_srealloc could be used.
301 void *silc_stack_realloc(SilcStack stack, SilcUInt32 old_size,
302 void *ptr, SilcUInt32 size);
304 /****f* silcutil/SilcStackAPI/silc_stack_set_oom_handler
308 * void silc_stack_set_oom_handler(SilcStack stack,
309 * SilcStackOomHandler oom_handler,
314 * Sets Out of Memory handler `oom_handler' to `stack' to be called
315 * if memory allocation from `stack' fails. The `context' is delivered
318 * Usually Out of Memory handler is set only when failed memory allocation
319 * is a fatal error. In this case the application would abort() inside
320 * the `oom_handler'. It may also be set if in case of failed allocation
321 * application wants to do clean up properly.
324 void silc_stack_set_oom_handler(SilcStack stack,
325 SilcStackOomHandler oom_handler,
328 /****f* silcutil/SilcStackAPI/silc_stack_set_alignment
332 * void silc_stack_set_alignment(SilcStack stack, SilcUInt32 alignment);
336 * Sets/changes the memory alignment in the `stack' to `alignment' which
337 * is the alignment in bytes. By default, the SilcStack will use alignment
338 * suited for the platform where it is used. This function can be used
339 * to change this alignment, if such change is needed. You may check the
340 * current alignment by calling silc_stack_get_alignment.
344 * It is not mandatory to call this function. By default the SilcStack
345 * will always use alignment suited for the used platform. This function
346 * should be called only if the alignment needs to be changed to something
347 * other than the default on the used platform. For example, some
348 * hardware device, such as crypto accelerator, may require special
352 void silc_stack_set_alignment(SilcStack stack, SilcUInt32 alignment);
354 /****f* silcutil/SilcStackAPI/silc_stack_get_alignment
358 * SilcUInt32 silc_stack_get_alignment(SilcStack stack);
362 * Returns the memory alignment used with `stack'. The alignment is in
366 SilcUInt32 silc_stack_get_alignment(SilcStack stack);
368 /****f* silcutil/SilcStackAPI/silc_stack_purge
372 * SilcBool silc_stack_purge(SilcStack stack);
376 * Purges the `stack' from extra unused memory. This purges only `stack'
377 * and not its parent if `stack' is a child. This purges only large
378 * allocations. The 1024, 2048, 4096 and 8192 bytes of allocations remain.
379 * Call this multiple times to purge even more. Returns FALSE when there
380 * is no more to purge. This does not purge memory blocks that currently
381 * have allocations. No memory allocations from the stack are lost, so
382 * this is always safe to call.
385 SilcBool silc_stack_purge(SilcStack stack);
387 #include "silcstack_i.h"
389 #endif /* SILCSTACK_H */