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Update readme & trim redundent code
jonroach 16 Jun 2026 14:15
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1#ifndef COROUTINE_H
2#define COROUTINE_H
3
4#include <stdbool.h>
5#include <stddef.h>
6#include <stdint.h>
7#include "coroutine_names_def.h"
8
9///////////////////////////////////////////////////////////////////////////////
10// Coroutine
11//
12// Coroutines for C, based on setjmp/longjmp.
13// Thread safe - each thread has its own coroutine system
14// Coroutines are cooperatively scheduled
15// Coroutines have their own stack (currently 16K each)
16// A coroutine can be continued, queried, or deleted on a different thread.
17//
18// Usage:
19// Coroutine_StartSystem(); // call once per thread before using coroutines
20// Coroutine *co = Coroutine_New(start_function);
21// void *result;
22// if (Coroutine_Run(co, initial_value, &result)) {
23// // Handle the failure
24// }
25// Coroutine_Delete(co);
26// Coroutine_StopSystem(); // call once per thread when done with coroutines
27//
28// Inside the coroutine function:
29// void *value = Coroutine_Yield(yield_value, on_yield, this);
30// ...
31// return return_value;
32//
33// To create a coroutine:
34// Coroutine *co = Coroutine_New(start_function);
35// To start or continue a coroutine:
36// void *result = Coroutine_Continue(co, value, early);
37// // early=true puts the coroutine at the head of the run queue
38// // early=false puts the coroutine at the tail of the run queue
39// To yield from inside a coroutine:
40// void *value = Coroutine_Yield(yield_value, on_yield, this);
41// // on_yield is called before the next coroutine is run
42// // 'this' is passed to on_yield as its parameter
43// // value is the value passed to Coroutine_Continue
44// To delete a coroutine:
45// Coroutine_Delete(co);
46// To get the value yielded from, or returned by a corotuine:
47// void *value = Coroutine_GetValue(co);
48// To get the currently running coroutine (NULL if none):
49// Coroutine *co = Coroutine_GetActive();
50// To check if a coroutine is currently running:
51// bool running = Coroutine_IsRunning(co);
52//
53// Notes:
54// Coroutine is not expected to be used directly, but as a foundation for
55// higher level constructs such as Generators, Async, etc.
56//
57///////////////////////////////////////////////////////////////////////////////
58
59
60// The stack is used as follows:
61// +------------------+ <- stack top
62// | coroutine header | <- more claimed as needed in Coroutine_New
63// +------------------+ <-
64// | coroutine stack | <-
65// +------------------+ <-
66// | coroutine header |
67// +------------------+
68// | coroutine stack |
69// +------------------+
70// | coroutine header |
71// +------------------+
72// | coroutine stack |
73// +------------------+
74// | coroutine header |
75// +------------------+
76// | coroutine stack |
77// +------------------+
78// | coroutine header |
79// +------------------+
80// | startup space | <- set aside by Coroutine_StartSystem
81// +------------------+
82// | caller | <- This calls Coroutine_StartSystem etc
83// +------------------+
84// | used stack |
85// +------------------+ <- stack bottom
86
87// Each coroutine has this much stack:
88// For Python, we set it to 17 * (enough for a PyEval_EvalDefault), so we get at least 7
89// calls deep before we need a new chunk, ie maximum multi-chunk wastage is under 6% address space.
90//
91// There's a trade-off between smaller chunk sizes, which allow more async tasks to co-exist
92// on a thread, and larger chunk sizes which waste less memory in part-used chunks.
93//
94// ... which means 10000 async tasks need a 2.6 GB stack, which fits comfortably in the address map.
95//
96// Note, when developing the use of Coroutine in Python, the author found the following used
97// excessive amounts of stack space:
98// Tk_Init: on an Intel 64 bit Mac it used 72k.
99// _decimal multplies of big decimal numbers: 256k+640 (2 x 128k buffers in squaretrans_pow2() + workings)
100//
101// On 64 bit macos, PYOS_STACK_MARGIN_BYTES is 2k * sizeof(void *), ie 16k, or 17 of those, 272k, should give enough slack to operate well.
102
103
104#ifndef Coroutine_API_FUNC
105 #define Coroutine_API_FUNC(T) extern T
106#endif
107
108// No coroutine will ask for less stack than this
109#ifndef COROUTINE_MINIMUM_STACK_SIZE
110 #define COROUTINE_MINIMUM_STACK_SIZE (4096 * sizeof(void *))
111#endif
112
113// When Coroutine is started, an amount of stack is set aside to give
114// the caller of Coroutine_StartSystem a bit of room to work before calling
115// Coroutine_Run(), that is this amount:
116#ifndef COROUTINE_STARTUP_STACK_SIZE
117 #ifndef _NDEBUG
118 #define COROUTINE_STARTUP_STACK_SIZE (1024 * sizeof(void *))
119 #else
120 #define COROUTINE_STARTUP_STACK_SIZE (128 * sizeof(void *))
121 #endif
122#endif
123
124// This is *expensive* to turn on, especially if you have lots of stack pieces (eg when there's lots of Tasks)
125#ifndef COROUTINE_CHECK_INTEGRITY_ON_STACK_CHECK
126 #define COROUTINE_CHECK_INTEGRITY_ON_STACK_CHECK 0
127#endif
128
129#ifndef COROUTINE_RECORD_LOWEST_HEADROOM
130 #define COROUTINE_RECORD_LOWEST_HEADROOM 1
131#endif
132
133// Returned by Coroutine_StopSystem(), this summarises the coroutine session
134typedef struct Coroutine_Report {
135 unsigned coroutines_created;
136 unsigned coroutines_pool_size;
137 size_t lowest_headroom;
138 size_t largest_stack;
139} Coroutine_Report;
140
141typedef enum Coroutine_Err {
142 Coroutine_OK = 0,
143 Coroutine_Err_SystemNotRunning,
144 Coroutine_Err_SystemRunning,
145 Coroutine_Err_NoStack,
146 Coroutine_Err_CoroutineFromWrongThread,
147 Coroutine_Err_ACoroutineIsAlreadyRunning,
148 Coroutine_Err_ExitWithRunningCoroutines,
149 Coroutine_Err_StackOverrun,
150 Coroutine_Err_InternalInsistency,
151 Coroutine_Err_CouldNotInitialiseSystem,
152 Coroutine_Err_WrongState,
153 Coroutine_Err_Canceled
154} Coroutine_Err;
155
156typedef struct Coroutine Coroutine;
157
158typedef void (*Coroutine_YieldCallback)(void *me);
159typedef Coroutine_Err (*Coroutine_SystemStart)(void *, Coroutine *);
160typedef void *(*Coroutine_Start)(void *);
161
162Coroutine_API_FUNC(void) Coroutine_SetStackLimit(void *);
163Coroutine_API_FUNC(Coroutine_Report) Coroutine_GetReport(void);
164#ifndef NDEBUG
165 Coroutine_API_FUNC(Coroutine_Err) Coroutine_CheckIntegrity(void);
166#else
167 static inline Coroutine_Err Coroutine_CheckIntegrity(void){return Coroutine_OK;}
168#endif
169Coroutine_API_FUNC(Coroutine *) Coroutine_New(size_t min_size, size_t min_headroom, Coroutine_Start start);
170Coroutine_API_FUNC(Coroutine_Err) Coroutine_RunSystem(size_t min_size, size_t min_headroom, Coroutine_SystemStart start, void *value);
171Coroutine_API_FUNC(Coroutine_Err) Coroutine_Run(size_t min_size, size_t min_headroom, Coroutine_Start start, void *value, void **result);
172Coroutine_API_FUNC(void) Coroutine_Delete(Coroutine *cor);
173Coroutine_API_FUNC(Coroutine_Err) Coroutine_Continue(Coroutine *cor, void *value, bool early);
174Coroutine_API_FUNC(void *) Coroutine_Yield(void *value, Coroutine_YieldCallback on_yield, void *me);
175Coroutine_API_FUNC(void *) Coroutine_GetValue(Coroutine *cor);
176Coroutine_API_FUNC(Coroutine *) Coroutine_GetActive(void);
177Coroutine_API_FUNC(ptrdiff_t) Coroutine_GetStackHeadroom(void);
178Coroutine_API_FUNC(void *) Coroutine_GetStackHWM(void);
179Coroutine_API_FUNC(void) Coroutine_ClearStackForHWM(void);
180Coroutine_API_FUNC(bool) Coroutine_CanStartCoroutine(size_t size);
181Coroutine_API_FUNC(void *) Coroutine_GetCStackTop(void);
182Coroutine_API_FUNC(Coroutine_Err) Coroutine_Chain(size_t min_size, size_t min_headroom, Coroutine_Start start, void *value, void **result);
183Coroutine_API_FUNC(bool) Coroutine_IsStarted(void);
184Coroutine_API_FUNC(bool) Coroutine_IsRunning(Coroutine *cor);
185Coroutine_API_FUNC(bool) Coroutine_IsComplete(Coroutine *cor);
186
187Coroutine_API_FUNC(void) Coroutine_Dump_(void);
188
189#include "coroutine_names_undef.h"
190#endif
191