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
|
#include "queue.h"
#include "csapp.h"
#define CORO_STKSIZE 4096
#define CORO_STKALIGN 16 /* As required by SysV ABI ! */
#ifndef EOF
#define EOF (-1)
#endif
#ifndef NOTHING
#define NOTHING (-2)
#endif
typedef struct coro {
TAILQ_ENTRY(coro) co_link;
const char *co_name;
void *co_stack;
Jmpbuf co_ctx;
} coro_t;
static TAILQ_HEAD(, coro) runqueue = TAILQ_HEAD_INITIALIZER(runqueue);
static coro_t *running;
static Jmpbuf dispatcher;
/* Initialize coroutine stucture with stack. */
static void coro_init(coro_t *co, const char *name) {
memset(co, 0, sizeof(coro_t));
co->co_name = name;
/* Allocates a fresh stack for the coroutine! */
if (posix_memalign(&co->co_stack, CORO_STKALIGN, CORO_STKSIZE) < 0)
unix_error("posix_memalign error");
}
/* Detach a stack from coroutine structure. */
static void coro_destroy(coro_t *co) {
free(co->co_stack);
}
/*
* Switch between subsequent coroutines.
*
* Dead coroutines, i.e. ones that returned EOF, get removed from the run queue.
* Feed next coroutine (value returned from coro_yield) with the result from
* previous one (parameter passed to coro_yield).
* Return to dispatcher if there're no more coroutines to run.
*/
static noreturn void coro_switch(int v) {
coro_t *curr = running;
/* TODO: Use description above to implement the body. */
curr = TAILQ_NEXT(curr, co_link);
if (v == EOF) {
TAILQ_REMOVE(&runqueue, running, co_link);
}
if (TAILQ_EMPTY(&runqueue)) {
Longjmp(dispatcher, 1);
}
if (curr) {
running = curr;
Longjmp(running->co_ctx, v);
} else {
running = TAILQ_FIRST(&runqueue);
Longjmp(running->co_ctx, NOTHING);
}
}
/* Save caller context and switch back to next coroutine. */
static int coro_yield(int v) {
int nv = Setjmp(running->co_ctx);
if (nv == 0)
coro_switch(v);
return nv;
}
/* Configure coroutine context to be executed. */
static void coro_add(coro_t *co, void (*fn)(int)) {
int v = Setjmp(co->co_ctx);
if (v) {
/* This will get executed when coroutine is entered first time. */
fn(v);
/* Coroutine must pass EOF to be removed from runqueue! */
coro_switch(EOF);
}
/* Coroutine will be running on its private stack! */
co->co_ctx->rsp = co->co_stack + CORO_STKSIZE;
TAILQ_INSERT_TAIL(&runqueue, co, co_link);
}
/* Take first coroutine and feed it with passed value. */
static int coro_run(int v) {
running = TAILQ_FIRST(&runqueue);
int nv = Setjmp(dispatcher);
if (nv == 0)
Longjmp(running->co_ctx, v);
return nv;
}
/*
* Actual coroutines that perform some useful work.
*/
static void func_1(int _) {
int words = 0;
char prev_ch = ' ';
char ch;
while (Read(0, &ch, 1) > 0) {
if (isspace(ch)) {
if (isspace(prev_ch))
continue;
words++;
}
coro_yield(ch);
prev_ch = ch;
}
if (!isspace(ch))
words++;
dprintf(STDERR_FILENO, "\nfunc_1: words = %d\n", words);
}
static void func_2(int ch) {
int removed = 0;
while (ch != EOF) {
if (!isalpha(ch)) {
removed++;
ch = NOTHING;
}
ch = coro_yield(ch);
}
dprintf(STDERR_FILENO, "func_2: removed = %d\n", removed);
}
static void func_3(int ch) {
int printed = 0;
while (ch != EOF) {
if (ch != NOTHING) {
printed++;
if (islower(ch))
ch = toupper(ch);
else if (isupper(ch))
ch = tolower(ch);
Write(STDOUT_FILENO, &ch, 1);
}
ch = coro_yield(NOTHING);
}
dprintf(STDERR_FILENO, "func_3: printed = %d\n", printed);
}
int main(void) {
coro_t co[3];
coro_init(&co[0], "func_1");
coro_init(&co[1], "func_2");
coro_init(&co[2], "func_3");
coro_add(&co[0], func_1);
coro_add(&co[1], func_2);
coro_add(&co[2], func_3);
coro_run(NOTHING);
coro_destroy(&co[0]);
coro_destroy(&co[1]);
coro_destroy(&co[2]);
dprintf(STDERR_FILENO, "Bye, bye!\n");
return EXIT_SUCCESS;
}
|
