diff options
Diffstat (limited to 'windows/handle-io.c')
| -rw-r--r-- | windows/handle-io.c | 687 |
1 files changed, 687 insertions, 0 deletions
diff --git a/windows/handle-io.c b/windows/handle-io.c new file mode 100644 index 00000000..0f5b7e94 --- /dev/null +++ b/windows/handle-io.c @@ -0,0 +1,687 @@ +/* + * handle-io.c: Module to give Windows front ends the general + * ability to deal with consoles, pipes, serial ports, or any other + * type of data stream accessed through a Windows API HANDLE rather + * than a WinSock SOCKET. + * + * We do this by spawning a subthread to continuously try to read + * from the handle. Every time a read successfully returns some + * data, the subthread sets an event object which is picked up by + * the main thread, and the main thread then sets an event in + * return to instruct the subthread to resume reading. + * + * Output works precisely the other way round, in a second + * subthread. The output subthread should not be attempting to + * write all the time, because it hasn't always got data _to_ + * write; so the output thread waits for an event object notifying + * it to _attempt_ a write, and then it sets an event in return + * when one completes. + * + * (It's terribly annoying having to spawn a subthread for each + * direction of each handle. Technically it isn't necessary for + * serial ports, since we could use overlapped I/O within the main + * thread and wait directly on the event objects in the OVERLAPPED + * structures. However, we can't use this trick for some types of + * file handle at all - for some reason Windows restricts use of + * OVERLAPPED to files which were opened with the overlapped flag - + * and so we must use threads for those. This being the case, it's + * simplest just to use threads for everything rather than trying + * to keep track of multiple completely separate mechanisms.) + */ + +#include <assert.h> + +#include "putty.h" + +/* ---------------------------------------------------------------------- + * Generic definitions. + */ + +typedef struct handle_list_node handle_list_node; +struct handle_list_node { + handle_list_node *next, *prev; +}; +static void add_to_ready_list(handle_list_node *node); + +/* + * Maximum amount of backlog we will allow to build up on an input + * handle before we stop reading from it. + */ +#define MAX_BACKLOG 32768 + +struct handle_generic { + /* + * Initial fields common to both handle_input and handle_output + * structures. + * + * The three HANDLEs are set up at initialisation time and are + * thereafter read-only to both main thread and subthread. + * `moribund' is only used by the main thread; `done' is + * written by the main thread before signalling to the + * subthread. `defunct' and `busy' are used only by the main + * thread. + */ + HANDLE h; /* the handle itself */ + handle_list_node ready_node; /* for linking on to the ready list */ + HANDLE ev_from_main; /* event used to signal back to us */ + bool moribund; /* are we going to kill this soon? */ + bool done; /* request subthread to terminate */ + bool defunct; /* has the subthread already gone? */ + bool busy; /* operation currently in progress? */ + void *privdata; /* for client to remember who they are */ +}; + +typedef enum { HT_INPUT, HT_OUTPUT } HandleType; + +/* ---------------------------------------------------------------------- + * Input threads. + */ + +/* + * Data required by an input thread. + */ +struct handle_input { + /* + * Copy of the handle_generic structure. + */ + HANDLE h; /* the handle itself */ + handle_list_node ready_node; /* for linking on to the ready list */ + HANDLE ev_from_main; /* event used to signal back to us */ + bool moribund; /* are we going to kill this soon? */ + bool done; /* request subthread to terminate */ + bool defunct; /* has the subthread already gone? */ + bool busy; /* operation currently in progress? */ + void *privdata; /* for client to remember who they are */ + + /* + * Data set at initialisation and then read-only. + */ + int flags; + + /* + * Data set by the input thread before marking the handle ready, + * and read by the main thread after receiving that signal. + */ + char buffer[4096]; /* the data read from the handle */ + DWORD len; /* how much data that was */ + int readerr; /* lets us know about read errors */ + + /* + * Callback function called by this module when data arrives on + * an input handle. + */ + handle_inputfn_t gotdata; +}; + +/* + * The actual thread procedure for an input thread. + */ +static DWORD WINAPI handle_input_threadfunc(void *param) +{ + struct handle_input *ctx = (struct handle_input *) param; + OVERLAPPED ovl, *povl; + HANDLE oev; + bool readret, finished; + int readlen; + + if (ctx->flags & HANDLE_FLAG_OVERLAPPED) { + povl = &ovl; + oev = CreateEvent(NULL, true, false, NULL); + } else { + povl = NULL; + } + + if (ctx->flags & HANDLE_FLAG_UNITBUFFER) + readlen = 1; + else + readlen = sizeof(ctx->buffer); + + while (1) { + if (povl) { + memset(povl, 0, sizeof(OVERLAPPED)); + povl->hEvent = oev; + } + readret = ReadFile(ctx->h, ctx->buffer,readlen, &ctx->len, povl); + if (!readret) + ctx->readerr = GetLastError(); + else + ctx->readerr = 0; + if (povl && !readret && ctx->readerr == ERROR_IO_PENDING) { + WaitForSingleObject(povl->hEvent, INFINITE); + readret = GetOverlappedResult(ctx->h, povl, &ctx->len, false); + if (!readret) + ctx->readerr = GetLastError(); + else + ctx->readerr = 0; + } + + if (!readret) { + /* + * Windows apparently sends ERROR_BROKEN_PIPE when a + * pipe we're reading from is closed normally from the + * writing end. This is ludicrous; if that situation + * isn't a natural EOF, _nothing_ is. So if we get that + * particular error, we pretend it's EOF. + */ + if (ctx->readerr == ERROR_BROKEN_PIPE) + ctx->readerr = 0; + ctx->len = 0; + } + + if (readret && ctx->len == 0 && + (ctx->flags & HANDLE_FLAG_IGNOREEOF)) + continue; + + /* + * If we just set ctx->len to 0, that means the read operation + * has returned end-of-file. Telling that to the main thread + * will cause it to set its 'defunct' flag and dispose of the + * handle structure at the next opportunity, in which case we + * mustn't touch ctx at all after the SetEvent. (Hence we do + * even _this_ check before the SetEvent.) + */ + finished = (ctx->len == 0); + + add_to_ready_list(&ctx->ready_node); + + if (finished) + break; + + WaitForSingleObject(ctx->ev_from_main, INFINITE); + if (ctx->done) { + /* + * The main thread has asked us to shut down. Send back an + * event indicating that we've done so. Hereafter we must + * not touch ctx at all, because the main thread might + * have freed it. + */ + add_to_ready_list(&ctx->ready_node); + break; + } + } + + if (povl) + CloseHandle(oev); + + return 0; +} + +/* + * This is called after a successful read, or from the + * `unthrottle' function. It decides whether or not to begin a new + * read operation. + */ +static void handle_throttle(struct handle_input *ctx, int backlog) +{ + if (ctx->defunct) + return; + + /* + * If there's a read operation already in progress, do nothing: + * when that completes, we'll come back here and be in a + * position to make a better decision. + */ + if (ctx->busy) + return; + + /* + * Otherwise, we must decide whether to start a new read based + * on the size of the backlog. + */ + if (backlog < MAX_BACKLOG) { + SetEvent(ctx->ev_from_main); + ctx->busy = true; + } +} + +/* ---------------------------------------------------------------------- + * Output threads. + */ + +/* + * Data required by an output thread. + */ +struct handle_output { + /* + * Copy of the handle_generic structure. + */ + HANDLE h; /* the handle itself */ + handle_list_node ready_node; /* for linking on to the ready list */ + HANDLE ev_from_main; /* event used to signal back to us */ + bool moribund; /* are we going to kill this soon? */ + bool done; /* request subthread to terminate */ + bool defunct; /* has the subthread already gone? */ + bool busy; /* operation currently in progress? */ + void *privdata; /* for client to remember who they are */ + + /* + * Data set at initialisation and then read-only. + */ + int flags; + + /* + * Data set by the main thread before signalling ev_from_main, + * and read by the input thread after receiving that signal. + */ + const char *buffer; /* the data to write */ + DWORD len; /* how much data there is */ + + /* + * Data set by the input thread before marking this handle as + * ready, and read by the main thread after receiving that signal. + */ + DWORD lenwritten; /* how much data we actually wrote */ + int writeerr; /* return value from WriteFile */ + + /* + * Data only ever read or written by the main thread. + */ + bufchain queued_data; /* data still waiting to be written */ + enum { EOF_NO, EOF_PENDING, EOF_SENT } outgoingeof; + + /* + * Callback function called when the backlog in the bufchain + * drops. + */ + handle_outputfn_t sentdata; + struct handle *sentdata_param; +}; + +static DWORD WINAPI handle_output_threadfunc(void *param) +{ + struct handle_output *ctx = (struct handle_output *) param; + OVERLAPPED ovl, *povl; + HANDLE oev; + bool writeret; + + if (ctx->flags & HANDLE_FLAG_OVERLAPPED) { + povl = &ovl; + oev = CreateEvent(NULL, true, false, NULL); + } else { + povl = NULL; + } + + while (1) { + WaitForSingleObject(ctx->ev_from_main, INFINITE); + if (ctx->done) { + /* + * The main thread has asked us to shut down. Send back an + * event indicating that we've done so. Hereafter we must + * not touch ctx at all, because the main thread might + * have freed it. + */ + add_to_ready_list(&ctx->ready_node); + break; + } + if (povl) { + memset(povl, 0, sizeof(OVERLAPPED)); + povl->hEvent = oev; + } + + writeret = WriteFile(ctx->h, ctx->buffer, ctx->len, + &ctx->lenwritten, povl); + if (!writeret) + ctx->writeerr = GetLastError(); + else + ctx->writeerr = 0; + if (povl && !writeret && GetLastError() == ERROR_IO_PENDING) { + writeret = GetOverlappedResult(ctx->h, povl, + &ctx->lenwritten, true); + if (!writeret) + ctx->writeerr = GetLastError(); + else + ctx->writeerr = 0; + } + + add_to_ready_list(&ctx->ready_node); + if (!writeret) { + /* + * The write operation has suffered an error. Telling that + * to the main thread will cause it to set its 'defunct' + * flag and dispose of the handle structure at the next + * opportunity, so we must not touch ctx at all after + * this. + */ + break; + } + } + + if (povl) + CloseHandle(oev); + + return 0; +} + +static void handle_try_output(struct handle_output *ctx) +{ + if (!ctx->busy && bufchain_size(&ctx->queued_data)) { + ptrlen data = bufchain_prefix(&ctx->queued_data); + ctx->buffer = data.ptr; + ctx->len = min(data.len, ~(DWORD)0); + SetEvent(ctx->ev_from_main); + ctx->busy = true; + } else if (!ctx->busy && bufchain_size(&ctx->queued_data) == 0 && + ctx->outgoingeof == EOF_PENDING) { + ctx->sentdata(ctx->sentdata_param, 0, 0, true); + ctx->h = INVALID_HANDLE_VALUE; + ctx->outgoingeof = EOF_SENT; + } +} + +/* ---------------------------------------------------------------------- + * Unified code handling both input and output threads. + */ + +struct handle { + HandleType type; + union { + struct handle_generic g; + struct handle_input i; + struct handle_output o; + } u; +}; + +/* + * Linked list storing the current list of handles ready to have + * something done to them by the main thread. + */ +static handle_list_node ready_head[1]; +static CRITICAL_SECTION ready_critsec[1]; + +/* + * Event object used by all subthreads to signal that they've just put + * something on the ready list, i.e. that the ready list is non-empty. + */ +static HANDLE ready_event = INVALID_HANDLE_VALUE; + +static void add_to_ready_list(handle_list_node *node) +{ + /* + * Called from subthreads, when their handle has done something + * that they need the main thread to respond to. We append the + * given list node to the end of the ready list, and set + * ready_event to signal to the main thread that the ready list is + * now non-empty. + */ + EnterCriticalSection(ready_critsec); + node->next = ready_head; + node->prev = ready_head->prev; + node->next->prev = node->prev->next = node; + SetEvent(ready_event); + LeaveCriticalSection(ready_critsec); +} + +static void remove_from_ready_list(handle_list_node *node) +{ + /* + * Called from the main thread, just before destroying a 'struct + * handle' completely: as a precaution, we make absolutely sure + * it's not linked on the ready list, just in case somehow it + * still was. + */ + EnterCriticalSection(ready_critsec); + node->next->prev = node->prev; + node->prev->next = node->next; + node->next = node->prev = node; + LeaveCriticalSection(ready_critsec); +} + +static void handle_ready(struct handle *h); /* process one handle (below) */ + +static void handle_ready_callback(void *vctx) +{ + /* + * Called when the main thread detects ready_event, indicating + * that at least one handle is on the ready list. We empty the + * whole list and process the handles one by one. + * + * It's possible that other handles may be destroyed, and hence + * taken _off_ the ready list, during this processing. That + * shouldn't cause a deadlock, because according to the API docs, + * it's safe to call EnterCriticalSection twice in the same thread + * - the second call will return immediately because that thread + * already owns the critsec. (And then it takes two calls to + * LeaveCriticalSection to release it again, which is just what we + * want here.) + */ + EnterCriticalSection(ready_critsec); + while (ready_head->next != ready_head) { + handle_list_node *node = ready_head->next; + node->prev->next = node->next; + node->next->prev = node->prev; + node->next = node->prev = node; + handle_ready(container_of(node, struct handle, u.g.ready_node)); + } + LeaveCriticalSection(ready_critsec); +} + +static inline void ensure_ready_event_setup(void) +{ + if (ready_event == INVALID_HANDLE_VALUE) { + ready_head->prev = ready_head->next = ready_head; + InitializeCriticalSection(ready_critsec); + ready_event = CreateEvent(NULL, false, false, NULL); + add_handle_wait(ready_event, handle_ready_callback, NULL); + } +} + +struct handle *handle_input_new(HANDLE handle, handle_inputfn_t gotdata, + void *privdata, int flags) +{ + struct handle *h = snew(struct handle); + DWORD in_threadid; /* required for Win9x */ + + h->type = HT_INPUT; + h->u.i.h = handle; + h->u.i.ev_from_main = CreateEvent(NULL, false, false, NULL); + h->u.i.gotdata = gotdata; + h->u.i.defunct = false; + h->u.i.moribund = false; + h->u.i.done = false; + h->u.i.privdata = privdata; + h->u.i.flags = flags; + + ensure_ready_event_setup(); + HANDLE hThread = CreateThread(NULL, 0, handle_input_threadfunc, + &h->u.i, 0, &in_threadid); + if (hThread) + CloseHandle(hThread); /* we don't need the thread handle */ + h->u.i.busy = true; + + return h; +} + +struct handle *handle_output_new(HANDLE handle, handle_outputfn_t sentdata, + void *privdata, int flags) +{ + struct handle *h = snew(struct handle); + DWORD out_threadid; /* required for Win9x */ + + h->type = HT_OUTPUT; + h->u.o.h = handle; + h->u.o.ev_from_main = CreateEvent(NULL, false, false, NULL); + h->u.o.busy = false; + h->u.o.defunct = false; + h->u.o.moribund = false; + h->u.o.done = false; + h->u.o.privdata = privdata; + bufchain_init(&h->u.o.queued_data); + h->u.o.outgoingeof = EOF_NO; + h->u.o.sentdata = sentdata; + h->u.o.sentdata_param = h; + h->u.o.flags = flags; + + ensure_ready_event_setup(); + HANDLE hThread = CreateThread(NULL, 0, handle_output_threadfunc, + &h->u.o, 0, &out_threadid); + if (hThread) + CloseHandle(hThread); /* we don't need the thread handle */ + + return h; +} + +size_t handle_write(struct handle *h, const void *data, size_t len) +{ + assert(h->type == HT_OUTPUT); + assert(h->u.o.outgoingeof == EOF_NO); + bufchain_add(&h->u.o.queued_data, data, len); + handle_try_output(&h->u.o); + return bufchain_size(&h->u.o.queued_data); +} + +void handle_write_eof(struct handle *h) +{ + /* + * This function is called when we want to proactively send an + * end-of-file notification on the handle. We can only do this by + * actually closing the handle - so never call this on a + * bidirectional handle if we're still interested in its incoming + * direction! + */ + assert(h->type == HT_OUTPUT); + if (h->u.o.outgoingeof == EOF_NO) { + h->u.o.outgoingeof = EOF_PENDING; + handle_try_output(&h->u.o); + } +} + +static void handle_destroy(struct handle *h) +{ + if (h->type == HT_OUTPUT) + bufchain_clear(&h->u.o.queued_data); + CloseHandle(h->u.g.ev_from_main); + remove_from_ready_list(&h->u.g.ready_node); + sfree(h); +} + +void handle_free(struct handle *h) +{ + assert(h && !h->u.g.moribund); + if (h->u.g.busy) { + /* + * If the handle is currently busy, we cannot immediately free + * it, because its subthread is in the middle of something. + * (Exception: foreign handles don't have a subthread.) + * + * Instead we must wait until it's finished its current + * operation, because otherwise the subthread will write to + * invalid memory after we free its context from under it. So + * we set the moribund flag, which will be noticed next time + * an operation completes. + */ + h->u.g.moribund = true; + } else if (h->u.g.defunct) { + /* + * There isn't even a subthread; we can go straight to + * handle_destroy. + */ + handle_destroy(h); + } else { + /* + * The subthread is alive but not busy, so we now signal it + * to die. Set the moribund flag to indicate that it will + * want destroying after that. + */ + h->u.g.moribund = true; + h->u.g.done = true; + h->u.g.busy = true; + SetEvent(h->u.g.ev_from_main); + } +} + +static void handle_ready(struct handle *h) +{ + if (h->u.g.moribund) { + /* + * A moribund handle is one which we have either already + * signalled to die, or are waiting until its current I/O op + * completes to do so. Either way, it's treated as already + * dead from the external user's point of view, so we ignore + * the actual I/O result. We just signal the thread to die if + * we haven't yet done so, or destroy the handle if not. + */ + if (h->u.g.done) { + handle_destroy(h); + } else { + h->u.g.done = true; + h->u.g.busy = true; + SetEvent(h->u.g.ev_from_main); + } + return; + } + + switch (h->type) { + int backlog; + + case HT_INPUT: + h->u.i.busy = false; + + /* + * A signal on an input handle means data has arrived. + */ + if (h->u.i.len == 0) { + /* + * EOF, or (nearly equivalently) read error. + */ + h->u.i.defunct = true; + h->u.i.gotdata(h, NULL, 0, h->u.i.readerr); + } else { + backlog = h->u.i.gotdata(h, h->u.i.buffer, h->u.i.len, 0); + handle_throttle(&h->u.i, backlog); + } + break; + + case HT_OUTPUT: + h->u.o.busy = false; + + /* + * A signal on an output handle means we have completed a + * write. Call the callback to indicate that the output + * buffer size has decreased, or to indicate an error. + */ + if (h->u.o.writeerr) { + /* + * Write error. Send a negative value to the callback, + * and mark the thread as defunct (because the output + * thread is terminating by now). + */ + h->u.o.defunct = true; + h->u.o.sentdata(h, 0, h->u.o.writeerr, false); + } else { + bufchain_consume(&h->u.o.queued_data, h->u.o.lenwritten); + noise_ultralight(NOISE_SOURCE_IOLEN, h->u.o.lenwritten); + h->u.o.sentdata(h, bufchain_size(&h->u.o.queued_data), 0, false); + handle_try_output(&h->u.o); + } + break; + } +} + +void handle_unthrottle(struct handle *h, size_t backlog) +{ + assert(h->type == HT_INPUT); + handle_throttle(&h->u.i, backlog); +} + +size_t handle_backlog(struct handle *h) +{ + assert(h->type == HT_OUTPUT); + return bufchain_size(&h->u.o.queued_data); +} + +void *handle_get_privdata(struct handle *h) +{ + return h->u.g.privdata; +} + +static void handle_sink_write(BinarySink *bs, const void *data, size_t len) +{ + handle_sink *sink = BinarySink_DOWNCAST(bs, handle_sink); + handle_write(sink->h, data, len); +} + +void handle_sink_init(handle_sink *sink, struct handle *h) +{ + sink->h = h; + BinarySink_INIT(sink, handle_sink_write); +} |