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Collect platform specific bits into cor_platform
jonroach 20 Oct 2025 14:36
1 contributor
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8 months ago
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 #include "coroutine.h"
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 #include <assert.h>
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 #include <setjmp.h>
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 #include <stdbool.h>
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 #include <stddef.h>
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 #include <stdio.h>
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 #include <stdlib.h>
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 #include "cor_platform.h"
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 static void *mustmalloc(size_t size){
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 void *p = malloc(size);
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 assert(p);
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 return p;
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 }
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 #define New(type, ...) (type##_ctor((type *)mustmalloc(sizeof(type), ## __VA_ARGS__)))
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 #define Delete(ptr, type) ((ptr) ? (type##_dtor(ptr), free(ptr), (ptr) = NULL) : (void)0)
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 static void Coroutine_RunNext();
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 static void _Coroutine_Continue(Coroutine *cor, void *value, bool early);
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 ///////////////////////////////////////////////////////////////////////////////
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 // 2-way linked lists...
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 //
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 // Brought inline here to avoid namespace polution
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 ///////////////////////////////////////////////////////////////////////////////
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 typedef struct List_Link List_Link;
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 struct List_Link {
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 List_Link *next;
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 List_Link *prev;
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 };
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 typedef struct List_Head List_Head;
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 struct List_Head {
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 union {
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 struct {
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 List_Link link;
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 List_Link *filler;
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 } fwd;
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 struct {
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 List_Link *filler;
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 List_Link link;
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 } back;
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 };
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 };
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 static inline bool List_IsEmpty(
50
 const List_Head *list
51
 ){
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 return list->fwd.link.next == &list->back.link;
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 }
54
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 static inline List_Link *List_GetHead(
57
 const List_Head *list
58
 ){
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 return List_IsEmpty(list) ? NULL : list->fwd.link.next;
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 }
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62
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 // static inline List_Link *List_GetTail(
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 // const List_Head *list
65
 // ){
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 // return List_IsEmpty(list) ? NULL : list->back.link.prev;
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 // }
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69
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 #define OFFSETOF(Container, Field) ((char *)&((Container *)4)->Field - (char *)(Container *)4)
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 #define List_Link_Container(Container, Link, link) ((Container *)((char *)(link) - OFFSETOF(Container, Link)))
72
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 static inline void List_Init(
75
 List_Head *list
76
 ){
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 list->fwd.link.next = &list->back.link;
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 list->fwd.link.prev = NULL;
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 list->back.link.prev = &list->fwd.link;
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 }
81
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 static inline void List_AddHead(
84
 List_Head *list,
85
 List_Link *link
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 ){
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 List_Link *first = list->fwd.link.next;
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 link->next = first;
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 link->prev = &list->fwd.link;
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 first->prev = link;
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 list->fwd.link.next = link;
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 }
93
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95
 static inline void List_AddTail(
96
 List_Head *list,
97
 List_Link *link
98
 ){
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 List_Link *last = list->back.link.prev;
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 link->prev = last;
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 link->next = &list->back.link;
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 last->next = link;
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 list->back.link.prev = link;
104
 }
105
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107
 static inline void List_Remove(
108
 List_Link *link
109
 ){
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 link->prev->next = link->next;
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 link->next->prev = link->prev;
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 }
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114
 ///////////////////////////////////////////////////////////////////////////////
115
 // ...2-way linked lists
116
 ///////////////////////////////////////////////////////////////////////////////
117
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 typedef struct Coroutines Coroutines;
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120
 enum {
121
 Coroutines_Idle,
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 Coroutines_Starting,
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 Coroutines_Started,
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 Coroutines_Active,
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 Coroutines_Stopping
126
 };
127
128
 enum {
129
 Chunk_Initial,
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 Chunk_Create,
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 Chunk_Enter
132
 };
133
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 typedef enum Coroutine_State {
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 Coroutine_Constructing,
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 Coroutine_Free,
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 Coroutine_Idle,
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 Coroutine_Running,
139
 Coroutine_Waiting,
140
 Coroutine_Complete
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 } Coroutine_State;
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143
 enum {
144
 Coroutines_Init,
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 Coroutines_AllocatedChunk,
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 Coroutines_CoroutineComplete,
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 };
148
149
 struct Coroutine {
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 Coroutines *coroutines; // so can work with it off-thread
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 List_Link link; // for whichever list it's on
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 jmp_buf buf; // how to get back to it
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 unsigned char *guard; // where the stack overrun guard is
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 Coroutine_Start start; // entry point
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 void *entry_param; // to pass to start
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 void *value; // yielded/returned
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 Coroutine_State state;
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 };
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160
 struct Coroutines {
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 _Cor_Mutex mutex;
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 jmp_buf controller; // to return from Coroutine_Run
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 jmp_buf chunk_allocated;// for chunk allocation
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 unsigned char *guard; // the stack guard for the startup sequence
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166
 // singletons
167
 Coroutine *tip; // top of stack chunk
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 Coroutine *active; // currently running coroutine
169
 Coroutine *primary; // Coroutine_Run coroutine
170
171
 // lists
172
 List_Head free;
173
 List_Head inactive; // idle or complete
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 List_Head runable; // running or waiting to run
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 List_Head waiting; // yielded / waiting to run
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 _Cor_Mutex waiting_mutex;
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 // Summary of the system
179
 Coroutine_Report report;
180
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 // state
182
 char state;
183
 };
184
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 _Cor_thread_local Coroutines *g_c;
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187
 static void stack_chunk_chunk(Coroutine *parent);
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 static void stack_chunk_base(Coroutine *parent, unsigned char *guard);
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 // Check whether the guard is intact
192
 static inline bool Check_Guard(
193
 unsigned char *guard
194
 ){
195
 return guard[0] == 0xde &&
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 guard[1] == 0xad &&
197
 guard[2] == 0xbe &&
198
 guard[3] == 0xef;
199
 }
200
201
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 static void Coroutine_PrimeStackChunks()
203
 {
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 unsigned char chunk_of_stack[COROUTINE_STARTUP_STACK_SIZE];
205
 for (int i = 0; i < COROUTINE_STARTUP_STACK_SIZE-3; i += 4){
206
 chunk_of_stack[i+0] = 0xde;
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 chunk_of_stack[i+1] = 0xad;
208
 chunk_of_stack[i+2] = 0xbe;
209
 chunk_of_stack[i+3] = 0xef;
210
 }
211
 assert(Check_Guard(chunk_of_stack));
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213
 // Stacks grow down in memory (almost always), so if the caller of this function changes
214
 // the guard before entering the coroutine system, it has overrun the startup stack
215
 g_c->guard = chunk_of_stack;
216
217
 stack_chunk_base(NULL, NULL);
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218
 }
219
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221
 static void stack_chunk_chunk(
222
 Coroutine *parent
223
 ){
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 unsigned char chunk_of_stack[COROUTINE_STACK_SIZE];
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 for (int i = 0; i < COROUTINE_STACK_SIZE-3; i += 4){
226
 chunk_of_stack[i+0] = 0xde;
227
 chunk_of_stack[i+1] = 0xad;
228
 chunk_of_stack[i+2] = 0xbe;
229
 chunk_of_stack[i+3] = 0xef;
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 }
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 stack_chunk_base(parent, chunk_of_stack);
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232
 }
233
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235
 static void stack_chunk_base(
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 Coroutine *parent,
237
 unsigned char *guard
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 ){
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 Coroutine here;
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 here.state = Coroutine_Constructing;
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 switch (setjmp(here.buf)) {
242
 case Chunk_Initial:
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 // got here for the first time
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 // parent now has a chunk_of_stack - add it to the free list
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 if (parent) {
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 assert(parent->state == Coroutine_Constructing);
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 assert(Check_Guard(guard));
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 parent->guard = guard;
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 parent->state = Coroutine_Free;
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 List_AddHead(&g_c->free, &parent->link);
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 g_c->report.coroutines_pool_size += 1;
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 }
253
 // note that here is the tip of the chunk-claim stack
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 here.coroutines = g_c;
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 g_c->tip = &here;
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 // return to the coroutine allocator
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 longjmp(g_c->chunk_allocated, 1);
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 case Chunk_Create:
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 // request to create a new chunk on the stack
261
 assert(here.state == Coroutine_Constructing);
262
 stack_chunk_chunk(&here);
263
 assert(false);
264
 case Chunk_Enter:
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 // request to start a coroutine (ie use the chunk for a coroutine)
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 // arrive here with mutex locked
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 assert(here.state == Coroutine_Running);
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 g_c->active = &here;
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 _Cor_Mutex_Unlock(&g_c->mutex);
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 here.value = here.start(here.entry_param);
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272
 // check the guard
273
 if (!Check_Guard(here.guard)){
274
 printf("Coroutine has overrun its stack - checked after returning from coroutine function\n");
275
 exit(EXIT_FAILURE);
276
 }
277
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 _Cor_Mutex_Lock(&g_c->mutex);
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 g_c->active = NULL;
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 assert(here.state == Coroutine_Running);
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 List_Remove(&here.link);
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 here.state = Coroutine_Complete;
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 List_AddTail(&g_c->inactive, &here.link);
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 // coroutine has completed
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 if (g_c->primary == &here) {
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 // if primary coroutine - return to Coroutine_Run
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 longjmp(g_c->controller, Coroutines_CoroutineComplete);
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288
 }
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 _Cor_Mutex_Unlock(&g_c->mutex);
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 Coroutine_RunNext();
291
 assert(false);
292
 }
293
 }
294
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 static void Coroutine_RunNext()
297
 {
298
 // arrive here with mutex unlocked
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 _Cor_Mutex_Lock(&g_c->waiting_mutex);
300
 _Cor_Mutex_Lock(&g_c->mutex);
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301
 Coroutine *next = List_Link_Container(Coroutine, link, List_GetHead(&g_c->runable));
302
 assert(next->state == Coroutine_Running);
303
 longjmp(next->buf, Chunk_Enter);
304
 assert(false);
305
 }
306
307
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 void Coroutine_StartSystem()
309
 {
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 assert(!g_c);
311
 g_c = mustmalloc(sizeof(Coroutines));
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 g_c->state = Coroutines_Starting;
314
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 _Cor_Mutex_ctor(&g_c->mutex);
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 g_c->tip = NULL;
318
 g_c->active = NULL;
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8 months ago
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 List_Init(&g_c->free);
321
 List_Init(&g_c->inactive);
322
 List_Init(&g_c->runable);
323
 List_Init(&g_c->waiting);
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 _Cor_Mutex_ctor(&g_c->waiting_mutex);
325
 _Cor_Mutex_Lock(&g_c->waiting_mutex);
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 g_c->report.coroutines_created = 0;
328
 g_c->report.coroutines_pool_size = 0;
329
 g_c->report.lowest_headroom = COROUTINE_STACK_SIZE;
330
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 // prime the chunk system
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332
 if (!setjmp(g_c->chunk_allocated)){
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 Coroutine_PrimeStackChunks();
334
 assert(false);
335
 }
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337
 assert(g_c->state == Coroutines_Starting);
338
 g_c->state = Coroutines_Started;
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339
 }
340
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341
8 months ago
342
 Coroutine_Report Coroutine_StopSystem()
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343
 {
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344
 _Cor_Mutex_Lock(&g_c->mutex);
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 assert(g_c->state == Coroutines_Started);
346
 g_c->state = Coroutines_Stopping;
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347
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 int stackminheadroom = COROUTINE_STACK_SIZE;
349
 for (List_Link *link = g_c->free.fwd.link.next; link->next; link = link->next){
350
 Coroutine *cor = List_Link_Container(Coroutine, link, link);
351
 for (int i = 4; i < COROUTINE_STACK_SIZE-3; i += 4){
352
 if (!Check_Guard(&cor->guard[i])){
353
 stackminheadroom = i < stackminheadroom ? i : stackminheadroom;
354
 break;
355
 }
356
 }
357
 }
358
 g_c->report.lowest_headroom = stackminheadroom;
359
8 months ago
360
 assert(List_IsEmpty(&g_c->inactive));
7 months ago
361
 _Cor_Mutex_Unlock(&g_c->waiting_mutex);
362
 _Cor_Mutex_dtor(&g_c->waiting_mutex);
8 months ago
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363
8 months ago
364
 assert(g_c->state == Coroutines_Stopping);
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365
 _Cor_Mutex_Unlock(&g_c->mutex);
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366
 g_c->state = Coroutines_Idle;
7 months ago
367
 _Cor_Mutex_dtor(&g_c->mutex);
8 months ago
368
369
 Coroutine_Report res = g_c->report;
370
8 months ago
371
 free(g_c);
372
 g_c = NULL;
8 months ago
373
374
 return res;
8 months ago
4
375
 }
376
8 months ago
377
8 months ago
378
 void Coroutine_Run_Coroutine(
379
 Coroutine *cor,
8 months ago
380
 void *value
381
 ){
382
 Coroutines *cors = cor->coroutines;
383
 assert(g_c == cors);
7 months ago
384
 _Cor_Mutex_Lock(&cors->mutex);
8 months ago
385
 assert(cors->state == Coroutines_Started);
386
 cors->state = Coroutines_Active;
387
 cors->primary = cor;
8 months ago
388
7 months ago
389
 _Coroutine_Continue(cor, value, true);
8 months ago
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390
8 months ago
391
 if (!setjmp(cors->controller)){
7 months ago
392
 _Cor_Mutex_Unlock(&cors->mutex);
8 months ago
393
394
 // check the guard
395
 if (!Check_Guard(g_c->guard)){
396
 printf("Coroutine startup stack as has overrun - checked on entering the main coroutine\n");
397
 exit(EXIT_FAILURE);
398
 }
399
8 months ago
4
400
 // start the first coroutine
401
 Coroutine_RunNext();
402
 }
8 months ago
403
 // arrive here with mutex locked
8 months ago
404
 assert(List_IsEmpty(&cors->runable));
405
 assert(List_IsEmpty(&cors->waiting));
406
 assert(cors->state == Coroutines_Active);
407
 cors->state = Coroutines_Started;
7 months ago
408
 _Cor_Mutex_Unlock(&cors->mutex);
8 months ago
409
 }
410
411
412
 void *Coroutine_Run(
413
 Coroutine_Start start,
414
 void *value
415
 ){
416
 Coroutine *cor = Coroutine_New(start);
417
 Coroutine_Run_Coroutine(cor, value);
8 months ago
418
 void *res = Coroutine_GetValue(cor);
419
 Coroutine_Delete(cor);
420
 return res;
8 months ago
4
421
 }
422
423
8 months ago
424
 Coroutine *Coroutine_New(
425
 Coroutine_Start start
426
 ){
8 months ago
427
 assert((g_c->state == Coroutines_Started && List_IsEmpty(&g_c->inactive)) || g_c->state == Coroutines_Active);
8 months ago
428
8 months ago
4
429
 // if none free - add one
8 months ago
430
 if (List_IsEmpty(&g_c->free)){
431
 if (!setjmp(g_c->chunk_allocated)){
432
 longjmp(g_c->tip->buf, Chunk_Create);
8 months ago
4
433
 }
434
 }
435
8 months ago
436
 Coroutine *cor = List_Link_Container(Coroutine, link, List_GetHead(&g_c->free));
8 months ago
4
437
 assert(cor->state == Coroutine_Free);
438
 cor->state = Coroutine_Idle;
439
 cor->start = start;
440
 cor->value = NULL;
441
 List_Remove(&cor->link);
8 months ago
442
 List_AddHead(&g_c->inactive, &cor->link);
8 months ago
4
443
8 months ago
444
 g_c->report.coroutines_created += 1;
445
8 months ago
4
446
 return cor;
447
 }
448
8 months ago
449
450
 void Coroutine_Delete(
451
 Coroutine *cor
452
 ){
453
 Coroutines *cors = cor->coroutines;
7 months ago
454
 _Cor_Mutex_Lock(&cors->mutex);
8 months ago
4
455
 assert(cor->state == Coroutine_Idle || cor->state == Coroutine_Complete);
456
 cor->state = Coroutine_Free;
457
 List_Remove(&cor->link);
8 months ago
458
 List_AddTail(&cors->free, &cor->link);
7 months ago
459
 _Cor_Mutex_Unlock(&cors->mutex);
8 months ago
4
460
 }
461
8 months ago
462
7 months ago
463
 // Coroutine_Continue, assuming the mutex is claimed
464
 static void _Coroutine_Continue(
8 months ago
465
 Coroutine *cor,
466
 void *value,
467
 bool early
468
 ){
469
 Coroutines *cors = cor->coroutines;
8 months ago
4
470
 assert(cor->state == Coroutine_Idle || cor->state == Coroutine_Waiting);
471
 cor->entry_param = value;
472
 cor->state = Coroutine_Running;
473
 List_Remove(&cor->link);
474
 if ( early ) {
8 months ago
475
 List_AddHead(&cors->runable, &cor->link);
8 months ago
4
476
 } else {
8 months ago
477
 List_AddTail(&cors->runable, &cor->link);
8 months ago
4
478
 }
7 months ago
479
 _Cor_Mutex_Unlock(&cors->waiting_mutex);
7 months ago
480
 }
481
482
483
 void Coroutine_Continue(
484
 Coroutine *cor,
485
 void *value,
486
 bool early
487
 ){
488
 Coroutines *cors = cor->coroutines;
7 months ago
489
 _Cor_Mutex_Lock(&cors->mutex);
7 months ago
490
 _Coroutine_Continue(cor, value, early);
7 months ago
491
 _Cor_Mutex_Unlock(&cors->mutex);
8 months ago
4
492
 }
493
8 months ago
494
495
 void *Coroutine_Yield(
496
 void *value,
497
 Coroutine_YieldCallback on_yield,
8 months ago
498
 void *yield_me
8 months ago
499
 ){
8 months ago
500
 Coroutine *me = g_c->active;
501
 if (!Check_Guard(me->guard)){
502
 printf("Coroutine has overrun its stack - checked when yielding coroutine\n");
503
 exit(EXIT_FAILURE);
504
 }
505
7 months ago
506
 _Cor_Mutex_Lock(&g_c->mutex);
8 months ago
507
 Coroutines *cors = me->coroutines;
508
 assert(me && me->state == Coroutine_Running && cors == g_c);
8 months ago
4
509
 me->value = value;
510
 me->state = Coroutine_Waiting;
8 months ago
511
8 months ago
4
512
 List_Remove(&me->link);
7 months ago
513
 if (!List_IsEmpty(&cors->runable)){
7 months ago
514
 _Cor_Mutex_Unlock(&cors->waiting_mutex);
7 months ago
515
 }
8 months ago
516
 List_AddTail(&cors->waiting, &me->link);
8 months ago
517
8 months ago
518
 switch (setjmp(me->buf)){
519
 case Chunk_Initial:
7 months ago
520
 _Cor_Mutex_Unlock(&cors->mutex);
8 months ago
521
 on_yield(yield_me);
8 months ago
4
522
 Coroutine_RunNext();
8 months ago
523
 case Chunk_Create:
524
 assert(false);
525
 case Chunk_Enter:
526
 // arrive here with mutex locked
8 months ago
527
 cors->active = me;
8 months ago
528
 // when we return here - we are running again
529
 assert(me->state == Coroutine_Running);
530
 void *res = me->entry_param;
7 months ago
531
 _Cor_Mutex_Unlock(&cors->mutex);
8 months ago
532
 return res;
8 months ago
4
533
 }
8 months ago
534
 return NULL;
8 months ago
4
535
 }
536
8 months ago
537
538
 void *Coroutine_GetValue(
539
 Coroutine *cor
540
 ){
8 months ago
4
541
 return cor->value;
542
 }
543
8 months ago
544
8 months ago
4
545
 Coroutine *Coroutine_GetActive()
546
 {
8 months ago
547
 return g_c->active;
8 months ago
4
548
 }
549
8 months ago
550
8 months ago
551
 int Coroutine_GetStackHeadroom(){
552
 unsigned char tbuf[4];
553
 return tbuf - g_c->active->guard - 4;
554
 }
555
556
557
 bool Coroutine_HasCoroutinesInFreePool(){
558
 return !List_IsEmpty(&g_c->free);
559
 }
560
561
562
 void *Coroutine_GetCStackTop(){
563
 return g_c->tip;
564
 }
565
566
567
 struct Coroutine_ChainParam {
568
 Coroutine_Start start;
569
 void *value;
570
 Coroutine *ret;
571
 };
572
573
574
 static void *Coroutine_ChainFn(
575
 void *param
576
 ){
577
 struct Coroutine_ChainParam *params = (struct Coroutine_ChainParam *)param;
578
 Coroutine_Continue(params->ret, params->start(params->value), true);
579
 return NULL;
580
 }
581
582
583
 static void Coroutine_ChainYield(
584
 void *unused
585
 ){
586
 (void)unused;
587
 }
588
589
590
 void *Coroutine_Chain(
591
 Coroutine_Start start,
592
 void *value
593
 ){
594
 if (!Check_Guard(Coroutine_GetActive()->guard)){
595
 printf("Coroutine has overrun its stack - checked when chaining\n");
596
 exit(EXIT_FAILURE);
597
 }
598
 Coroutine *cor = Coroutine_New(Coroutine_ChainFn);
599
 struct Coroutine_ChainParam params = {
600
 start,
601
 value,
602
 Coroutine_GetActive()
603
 };
604
 Coroutine_Continue(cor, &params, true);
605
 void *res = Coroutine_Yield(NULL, Coroutine_ChainYield, NULL);
606
 Coroutine_Delete(cor);
607
 return res;
608
 }
609
610
8 months ago
611
 bool Coroutine_IsRunning(
612
 Coroutine *cor
613
 )
8 months ago
4
614
 {
8 months ago
615
 int state = cor->state;
616
 return state == Coroutine_Running || state == Coroutine_Waiting;
8 months ago
4
617
 }
8 months ago
618
619
620
 bool Coroutine_IsStarted(){
621
 return g_c != NULL;
622
 }
623