prosody
2db7b3b65363
util-src/managed_pointer.h

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util-src/managed_pointer.h @ 13627:2db7b3b65363

core.configmanager: Add function for getting secrets from separate files Idea is to enable easily retrieving of secret values from files outside of the config, e.g. via the method used by systemd credentials. CREDENTIALS_DIRECTORY is expected to be set by the process manager invoking Prosody, so being unset and unavailable from prosodyctl is going to be normal and a warning is reported in that case. Care will have to be taken to make it clear that prosodyctl check will not work with such values. An error is thrown if the directory is unavailable when running under Prosody.
author Kim Alvefur <zash@zash.se>
date Thu, 16 Jan 2025 15:21:34 +0100
parent 12692:b001b0f42512
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b001b0f42512 util-src: Add new utility header managed_pointer.h
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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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