Mercurial > prosody-hg

annotate util-src/managed_pointer.h @ 13135:3fd24e1945b0

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mod_storage_internal: Lazy-load archive items while iterating Very large list files previously ran into limits of the Lua parser, or just caused Prosody to freeze while parsing. Using the new index we can parse individual items one at a time. This probably won't reduce overall CPU usage, probably the opposite, but it will reduce the number of items in memory at once and allow collection of items after we iterated past them.
author Kim Alvefur <zash@zash.se>
date Wed, 12 May 2021 01:25:44 +0200
parents b001b0f42512
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 /* managed_pointer.h
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2
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3 These macros allow wrapping an allocator/deallocator into an object that is
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4 owned and managed by the Lua garbage collector.
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5
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6 Why? It is too easy to leak objects that need to be manually released, especially
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7 when dealing with the Lua API which can throw errors from many operations.
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8
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9 USAGE
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10 -----
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11
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12 For example, given an object that can be created or released with the following
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13 functions:
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14
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15 fancy_buffer* new_buffer();
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16 void free_buffer(fancy_buffer* p_buffer)
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17
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18 You could declare a managed version like so:
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19
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20 MANAGED_POINTER_ALLOCATOR(new_managed_buffer, fancy_buffer*, new_buffer, free_buffer)
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21
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22 And then, when you need to create a new fancy_buffer in your code:
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23
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24 fancy_buffer *my_buffer = new_managed_buffer(L);
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25
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26 NOTES
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27 -----
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28
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29 Managed objects MUST NOT be freed manually. They will automatically be
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30 freed during the next GC sweep after your function exits (even if via an error).
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31
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32 The managed object is pushed onto the stack, but should generally be ignored,
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33 but you'll need to bear this in mind when creating managed pointers in the
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34 middle of a sequence of stack operations.
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35 */
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36
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37 #define MANAGED_POINTER_MT(wrapped_type) #wrapped_type "_managedptr_mt"
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38
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39 #define MANAGED_POINTER_ALLOCATOR(name, wrapped_type, wrapped_alloc, wrapped_free) \
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40 static int _release_ ## name(lua_State *L) { \
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41 wrapped_type *p = (wrapped_type*)lua_topointer(L, 1); \
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42 if(*p != NULL) { \
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43 wrapped_free(*p); \
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44 } \
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45 return 0; \
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46 } \
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47 static wrapped_type name(lua_State *L) { \
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48 wrapped_type *p = (wrapped_type*)lua_newuserdata(L, sizeof(wrapped_type)); \
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49 if(luaL_newmetatable(L, MANAGED_POINTER_MT(wrapped_type)) != 0) { \
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50 lua_pushcfunction(L, _release_ ## name); \
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51 lua_setfield(L, -2, "__gc"); \
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52 } \
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53 lua_setmetatable(L, -2); \
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54 *p = wrapped_alloc(); \
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55 if(*p == NULL) { \
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56 lua_pushliteral(L, "not enough memory"); \
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57 lua_error(L); \
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58 } \
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59 return *p; \
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60 }
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