1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
|
/* Copyright (c) 2021 Dovecot authors, see the included COPYING file */
#include "lib.h"
#include "ioloop.h"
#include "dlua-script-private.h"
#define PCALL_RESUME_STATE "pcall-resume-state"
#define RESUME_TIMEOUT "resume-timeout"
#define RESUME_NARGS "resume-nargs"
struct dlua_pcall_resume_state {
dlua_pcall_yieldable_callback_t *callback;
void *context;
struct timeout *to;
int status;
};
#ifdef DLUA_WITH_YIELDS
static void call_resume_callback(lua_State *L)
{
struct dlua_pcall_resume_state *state = dlua_tls_get_ptr(L, PCALL_RESUME_STATE);
timeout_remove(&state->to);
dlua_tls_clear(L, PCALL_RESUME_STATE);
state->callback(L, state->context, state->status);
i_free(state);
}
static void queue_resume_callback(lua_State *L, int status)
{
struct dlua_pcall_resume_state *state = dlua_tls_get_ptr(L, PCALL_RESUME_STATE);
i_assert(status != LUA_YIELD);
if (status != LUA_OK) {
int ret;
/* error occured: run debug.traceback() */
/* stack: ..., error (top) */
lua_getglobal(L, "debug");
/* stack: ..., error, debug table (top) */
lua_getfield(L, -1, "traceback");
/* stack: ..., error, debug table, traceback function (top) */
lua_remove(L, -2);
/* stack: ..., error, traceback function (top) */
lua_pushvalue(L, -2); /* duplicate original error */
/* stack: ..., error, traceback function, error (top) */
/*
* Note that we kept the original error on the stack as well
* as passed it to debug.traceback(). The reason for that
* is that debug.traceback() itself can fail. If it fails,
* it'll generate its own error - which, ultimately, we
* don't care about. For example, consider the following
* function:
*
* function foo()
* debug.traceback = nil
* error("abc")
* end
*
* If we executed this function, it would error out - but
* it'd also cause our pcall to debug.traceback() to fail
* with "attempt to call a nil value". We want to discard
* the nil error, and just use the original ("abc"). This
* is ok because debug.traceback() simply "improves" the
* passed in error message to include a traceback and no
* traceback is better than a very mysterious error message.
*/
ret = lua_pcall(L, 1, 1, 0);
/* stack: ..., orig error, traceback result/error (top) */
if (ret != LUA_OK) {
/* traceback failed, remove its error */
lua_remove(L, -1);
} else {
/* traceback succeeded, remove original error */
lua_remove(L, -2);
}
}
/*
* Mangle the passed in status to match dlua_pcall(). Namely, turn
* it into -1 on error, and 0+ to indicate the number of return
* values.
*/
if (status == LUA_OK)
state->status = lua_gettop(L);
else
state->status = -1;
i_assert(state->to == NULL);
state->to = timeout_add_short(0, call_resume_callback, L);
}
static void dlua_pcall_yieldable_continue(lua_State *L)
{
struct timeout *to;
int nargs, nresults;
int ret;
nargs = dlua_tls_get_int(L, RESUME_NARGS);
to = dlua_tls_get_ptr(L, RESUME_TIMEOUT);
timeout_remove(&to);
dlua_tls_clear(L, RESUME_TIMEOUT);
dlua_tls_clear(L, RESUME_NARGS);
ret = lua_resume(L, L, nargs, &nresults);
if (ret == LUA_YIELD) {
/*
* thread yielded - nothing to do
*
* We assume something will call lua_resume(). We don't
* care if it is a io related callback or just a timeout.
*/
} else if (ret == LUA_OK) {
/* thread completed - invoke callback */
queue_resume_callback(L, ret);
} else {
/* error occurred - invoke callback */
queue_resume_callback(L, ret);
}
}
void dlua_pcall_yieldable_resume(lua_State *L, int nargs)
{
struct timeout *to;
to = timeout_add_short(0, dlua_pcall_yieldable_continue, L);
dlua_tls_set_ptr(L, RESUME_TIMEOUT, to);
dlua_tls_set_int(L, RESUME_NARGS, nargs);
}
/*
* Call a function with nargs arguments in a way that supports yielding.
* When the function execution completes, the passed in callback is called.
*
* Returns -1 on error or 0 on success.
*/
#undef dlua_pcall_yieldable
int dlua_pcall_yieldable(lua_State *L, const char *func_name, int nargs,
dlua_pcall_yieldable_callback_t *callback,
void *context, const char **error_r)
{
struct dlua_pcall_resume_state *state;
int ret;
int nresults;
i_assert(lua_status(L) == LUA_OK);
lua_getglobal(L, func_name);
if (!lua_isfunction(L, -1)) {
/* clean up the stack - function + arguments */
lua_pop(L, nargs + 1);
*error_r = t_strdup_printf("'%s' is not a function", func_name);
return -1;
}
/* allocate and stash in TLS callback state */
state = i_new(struct dlua_pcall_resume_state, 1);
state->callback = callback;
state->context = context;
dlua_tls_set_ptr(L, PCALL_RESUME_STATE, state);
/* stack: args, func (top) */
lua_insert(L, -(nargs + 1));
/* stack: func, args (top) */
ret = lua_resume(L, L, nargs, &nresults);
if (ret == LUA_YIELD) {
/*
* thread yielded - nothing to do
*
* We assume something will call lua_resume(). We don't
* care if it is a io related callback or just a timeout.
*/
} else {
/*
* thread completed / errored
*
* Since there is nothing that will come back to this lua
* thread, we need to make sure the callback is called.
*
* We handle errors the same as successful completion in
* order to avoid forcing the callers to check for lua
* errors in two places - the call here and in the callback.
*/
queue_resume_callback(L, ret);
}
return 0;
}
#endif
|
