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 context is not thread-safe. If the same SilcStack must be
57 * used in multithreaded environment concurrency control must be employed.
58 * Each thread should allocate their own SilcStack.
65 /****s* silcutil/SilcStackAPI/SilcStack
69 * typedef struct SilcStackStruct *SilcStack;
73 * This context represents the stack and it is allocated by
74 * silc_stack_alloc and is destroyed with silc_stack_free functions.
75 * The context is given as argument to all routines that use this
76 * stack allocation library.
79 typedef struct SilcStackStruct *SilcStack;
81 /****s* silcutil/SilcStackAPI/SilcStackFrame
85 * typedef struct SilcStackFrameStruct SilcStackFrame;
89 * Static stack frame context that optionally can be used as stack
90 * frame in SilcStack. By default silc_stack_push use pre-allocated
91 * stack frame, but user may also use statically allocated SilcStackFrame
92 * instead. This is recommended when using SilcStack in recursive routine
93 * and the recursion may become deep. Using static frame assures that
94 * during recursion frames never run out.
97 typedef struct SilcStackFrameStruct SilcStackFrame;
99 /****f* silcutil/SilcStackAPI/silc_stack_alloc
103 * SilcStack silc_stack_alloc(SilcUInt32 stack_size, SilcStack parent);
107 * Allocates new data stack that can be used as stack for fast memory
108 * allocation by various routines. Returns the pointer to the stack
109 * that must be freed with silc_stack_free function when it is not
110 * needed anymore. If the `stack_size' is zero (0) by default a
111 * 2 kilobytes (2048 bytes) stack is allocated. If the `stack_size'
112 * is non-zero the byte value must be multiple by 8.
114 * If `parent' is non-NULL the created stack is a child of the `parent'
115 * stack. All of childs the memory is allocated from the `parent' and
116 * will be returned back to the parent when the child is freed. Note
117 * that, even though child allocated memory from the parent, the parent's
118 * stack is not consumed.
120 * Returns NULL on error.
123 SilcStack silc_stack_alloc(SilcUInt32 stack_size, SilcStack parent);
125 /****f* silcutil/SilcStackAPI/silc_stack_free
129 * void silc_stack_free(SilcStack stack);
133 * Frees the data stack context. The stack cannot be used anymore after
134 * this and all allocated memory are freed.
136 * If `stack' is a child stack, its memory is returned back to its
140 void silc_stack_free(SilcStack stack);
142 /****f* silcutil/SilcStackAPI/silc_stack_push
146 * SilcUInt32 silc_stack_push(SilcStack stack, SilcStackFrame *frame);
150 * Push the top of the stack down which becomes the new top of the stack.
151 * For every silc_stack_push call there must be silc_stack_pop call. All
152 * allocations between these two calls will be done from the top of the
153 * stack and all allocated memory is freed after the next silc_stack_pop
154 * is called. This returns so called stack pointer for the new stack
155 * frame, which the caller may use to check that all calls to
156 * silc_stack_pop has been made. This call may do a small memory
157 * allocation in some cases, but usually it does not allocate any memory.
158 * If this returns zero (0) the system is out of memory.
160 * If the `frame' is non-NULL then that SilcStackFrame is used as
161 * stack frame. Usually `frame' is set to NULL by user. Statically
162 * allocated SilcStackFrame should be used when using silc_stack_push
163 * in recursive function and the recursion may become deep. In this
164 * case using statically allocated SilcStackFrame is recommended since
165 * it assures that frames never run out and silc_stack_push never
166 * allocates any memory. If your routine is not recursive then
167 * setting `frame' to NULL is recommended, unless performance is
170 * This function is used when a routine is doing frequent allocations
171 * from the stack. If the stack is not pushed and later popped all
172 * allocations are made from the stack and the stack eventually runs out
173 * (it gets enlarged by normal memory allocation). By pushing and then
174 * later popping the frequent allocations does not consume the stack.
176 * If `stack' is NULL this call has no effect.
180 * All memory allocations in silc_foo_parse_packet will be done in
181 * a fresh stack frame and that data is freed after the parsing is
184 * silc_stack_push(stack, NULL);
185 * silc_foo_parse_packet(packet, stack);
186 * silc_stack_pop(stack);
188 * Another example with recursion and using statically allocated
189 * SilcStackFrame. After popping the statically allocated frame can
190 * be reused if necessary.
192 * void silc_foo_this_function(SilcStack stack)
194 * SilcStackFrame frame;
196 * silc_stack_push(stack, &frame);
197 * silc_foo_this_function(stack); // Call recursively
198 * silc_stack_pop(stack);
203 SilcUInt32 silc_stack_push(SilcStack stack, SilcStackFrame *frame);
205 /****f* silcutil/SilcStackAPI/silc_stack_pop
209 * SilcUInt32 silc_stack_pop(SilcStack stack);
213 * Pop the top of the stack upwards which reveals the previous stack frame
214 * and becomes the top of the stack. After popping, memory allocated in
215 * the old frame is freed. For each silc_stack_push call there must be
216 * silc_stack_pop call to free all memory (in reality any memory is not
217 * freed but within the stack it is). This returns the stack pointer of
218 * old frame after popping and caller may check that it is same as
219 * returned by the silc_stack_push. If it they differ, some routine
220 * has called silc_stack_push but has not called silc_stack_pop, or
221 * silc_stack_pop has been called too many times. Application should
222 * treat this as a fatal error, as it is a bug in the application code.
224 * If `stack' is NULL this call has no effect.
228 * This example saves the stack pointer which is checked when popping
229 * the current stack frame. If the stack pointer differs then someone
230 * has pushed the stack frame but forgot to pop it (or has called it
233 * sp = silc_stack_push(stack, NULL);
234 * silc_foo_parse_packet(packet, stack);
235 * if (silc_stack_pop(stack) != sp)
236 * fatal("corrupted stack");
239 SilcUInt32 silc_stack_pop(SilcStack stack);
241 /****f* silcutil/SilcStackAPI/silc_stack_malloc
245 * void *silc_stack_malloc(SilcStack stack, SilcUInt32 size);
249 * Low level memory allocation routine. Allocates memor block of size of
250 * `size' from the `stack'. The allocated memory is aligned so it can be
251 * used to allocate memory for structures, for example. Returns the
252 * allocated memory address or NULL if memory could not be allocated from
257 * This function should be used only if low level memory allocation with
258 * SilcStack is needed. Instead, silc_smalloc, could be used.
261 void *silc_stack_malloc(SilcStack stack, SilcUInt32 size);
263 /****f* silcutil/SilcStackAPI/silc_stack_realloc
267 * void *silc_stack_realloc(SilcStack stack, SilcUInt32 old_size,
268 * *void *ptr, SilcUInt32 size);
272 * Attempts to reallocate memory by changing the size of the `ptr' into
273 * `size'. This routine works only if the previous allocation to `stack'
274 * was `ptr'. If there is another memory allocation between allocating
275 * `ptr' and this call this routine will return NULL. NULL is also
276 * returned if the `size' does not fit into the current block. If NULL
277 * is returned the old memory remains intact.
281 * This function should be used only if low level memory allocation with
282 * SilcStack is needed. Instead, silc_srealloc, could be used.
285 void *silc_stack_realloc(SilcStack stack, SilcUInt32 old_size,
286 void *ptr, SilcUInt32 size);
288 /****f* silcutil/SilcStackAPI/silc_stack_set_alignment
292 * void silc_stack_set_alignment(SilcStack stack, SilcUInt32 alignment);
296 * Sets/changes the memory alignment in the `stack' to `alignment' which
297 * is the alignment in bytes. By default, the SilcStack will use alignment
298 * suited for the platform where it is used. This function can be used
299 * change this alignment, if such change is needed. You may check the
300 * current alignment by calling silc_stack_get_alignment.
304 * It is not mandatory to call this function. By default the SilcStack
305 * will always use alignment suited for the used platform. This function
306 * should be called only if the alignment needs to be changed to something
307 * other than the default on the used platform. For example, some
308 * hardware device, such as crypto accelerator, may require special
312 void silc_stack_set_alignment(SilcStack stack, SilcUInt32 alignment);
314 /****f* silcutil/SilcStackAPI/silc_stack_get_alignment
318 * SilcUInt32 silc_stack_get_alignment(SilcStack stack);
322 * Returns the memory alignment used with `stack'. The alignment is in
326 SilcUInt32 silc_stack_get_alignment(SilcStack stack);
328 #include "silcstack_i.h"
330 #endif /* SILCSTACK_H */