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- /*
- * 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);
- }
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