--- /dev/null
+/*
+ * winhandl.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.
+ */
+
+/*
+ * TODO:
+ *
+ * - could do with some sort of private-data field in each handle
+ * structure.
+ */
+
+#include <assert.h>
+
+#include "putty.h"
+
+/* ----------------------------------------------------------------------
+ * Generic definitions.
+ */
+
+/*
+ * 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 ev_to_main; /* event used to signal main thread */
+ HANDLE ev_from_main; /* event used to signal back to us */
+ int moribund; /* are we going to kill this soon? */
+ int done; /* request subthread to terminate */
+ int defunct; /* has the subthread already gone? */
+ int busy; /* operation currently in progress? */
+};
+
+/* ----------------------------------------------------------------------
+ * Input threads.
+ */
+
+/*
+ * Data required by an input thread.
+ */
+struct handle_input {
+ /*
+ * Copy of the handle_generic structure.
+ */
+ HANDLE h; /* the handle itself */
+ HANDLE ev_to_main; /* event used to signal main thread */
+ HANDLE ev_from_main; /* event used to signal back to us */
+ int moribund; /* are we going to kill this soon? */
+ int done; /* request subthread to terminate */
+ int defunct; /* has the subthread already gone? */
+ int busy; /* operation currently in progress? */
+
+ /*
+ * Data set by the input thread before signalling ev_to_main,
+ * 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 readret; /* 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;
+
+ while (1) {
+ ctx->readret = ReadFile(ctx->h, ctx->buffer, sizeof(ctx->buffer),
+ &ctx->len, NULL);
+ if (!ctx->readret)
+ ctx->len = 0;
+
+ SetEvent(ctx->ev_to_main);
+
+ if (!ctx->len)
+ break;
+
+ WaitForSingleObject(ctx->ev_from_main, INFINITE);
+ if (ctx->done)
+ break; /* main thread told us to shut down */
+ }
+
+ return 0;
+}
+
+/*
+ * This is called after a succcessful 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)
+{
+ assert(!ctx->defunct);
+
+ /*
+ * 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 ev_to_main; /* event used to signal main thread */
+ HANDLE ev_from_main; /* event used to signal back to us */
+ int moribund; /* are we going to kill this soon? */
+ int done; /* request subthread to terminate */
+ int defunct; /* has the subthread already gone? */
+ int busy; /* operation currently in progress? */
+
+ /*
+ * Data set by the main thread before signalling ev_from_main,
+ * and read by the input thread after receiving that signal.
+ */
+ char *buffer; /* the data to write */
+ DWORD len; /* how much data there is */
+
+ /*
+ * Data set by the input thread before signalling ev_to_main,
+ * and read by the main thread after receiving that signal.
+ */
+ DWORD lenwritten; /* how much data we actually wrote */
+ int writeret; /* return value from WriteFile */
+
+ /*
+ * Data only ever read or written by the main thread.
+ */
+ bufchain queued_data; /* data still waiting to be written */
+
+ /*
+ * Callback function called when the backlog in the bufchain
+ * drops.
+ */
+ handle_outputfn_t sentdata;
+};
+
+static DWORD WINAPI handle_output_threadfunc(void *param)
+{
+ struct handle_output *ctx = (struct handle_output *) param;
+
+ while (1) {
+ WaitForSingleObject(ctx->ev_from_main, INFINITE);
+ if (ctx->done) {
+ SetEvent(ctx->ev_to_main);
+ break;
+ }
+ ctx->writeret = WriteFile(ctx->h, ctx->buffer, ctx->len,
+ &ctx->lenwritten, NULL);
+ SetEvent(ctx->ev_to_main);
+ if (!ctx->writeret)
+ break;
+ }
+
+ return 0;
+}
+
+static void handle_try_output(struct handle_output *ctx)
+{
+ void *senddata;
+ int sendlen;
+
+ if (!ctx->busy && bufchain_size(&ctx->queued_data)) {
+ bufchain_prefix(&ctx->queued_data, &senddata, &sendlen);
+ ctx->buffer = senddata;
+ ctx->len = sendlen;
+ SetEvent(ctx->ev_from_main);
+ ctx->busy = TRUE;
+ }
+}
+
+/* ----------------------------------------------------------------------
+ * Unified code handling both input and output threads.
+ */
+
+struct handle {
+ int output;
+ union {
+ struct handle_generic g;
+ struct handle_input i;
+ struct handle_output o;
+ } u;
+};
+
+static tree234 *handles_by_evtomain;
+
+static int handle_cmp_evtomain(void *av, void *bv)
+{
+ struct handle *a = (struct handle *)av;
+ struct handle *b = (struct handle *)bv;
+
+ if ((unsigned)a->u.g.ev_to_main < (unsigned)b->u.g.ev_to_main)
+ return -1;
+ else if ((unsigned)a->u.g.ev_to_main > (unsigned)b->u.g.ev_to_main)
+ return +1;
+ else
+ return 0;
+}
+
+static int handle_find_evtomain(void *av, void *bv)
+{
+ HANDLE *a = (HANDLE *)av;
+ struct handle *b = (struct handle *)bv;
+
+ if ((unsigned)*a < (unsigned)b->u.g.ev_to_main)
+ return -1;
+ else if ((unsigned)*a > (unsigned)b->u.g.ev_to_main)
+ return +1;
+ else
+ return 0;
+}
+
+struct handle *handle_input_new(HANDLE handle, handle_inputfn_t gotdata)
+{
+ struct handle *h = snew(struct handle);
+
+ h->output = FALSE;
+ h->u.i.h = handle;
+ h->u.i.ev_to_main = CreateEvent(NULL, FALSE, FALSE, NULL);
+ h->u.i.ev_from_main = CreateEvent(NULL, FALSE, FALSE, NULL);
+ h->u.i.gotdata = gotdata;
+ h->u.i.busy = FALSE;
+ h->u.i.defunct = FALSE;
+ h->u.i.moribund = FALSE;
+ h->u.i.done = FALSE;
+
+ if (!handles_by_evtomain)
+ handles_by_evtomain = newtree234(handle_cmp_evtomain);
+ add234(handles_by_evtomain, h);
+
+ CreateThread(NULL, 0, handle_input_threadfunc,
+ &h->u.i, 0, NULL);
+
+ handle_throttle(&h->u.i, 0); /* start first read operation */
+
+ return h;
+}
+
+struct handle *handle_output_new(HANDLE handle, handle_outputfn_t sentdata)
+{
+ struct handle *h = snew(struct handle);
+
+ h->output = TRUE;
+ h->u.o.h = handle;
+ h->u.o.ev_to_main = CreateEvent(NULL, FALSE, FALSE, NULL);
+ 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;
+ bufchain_init(&h->u.o.queued_data);
+ h->u.o.sentdata = sentdata;
+
+ if (!handles_by_evtomain)
+ handles_by_evtomain = newtree234(handle_cmp_evtomain);
+ add234(handles_by_evtomain, h);
+
+ CreateThread(NULL, 0, handle_output_threadfunc,
+ &h->u.i, 0, NULL);
+
+ return h;
+}
+
+int handle_write(struct handle *h, const void *data, int len)
+{
+ assert(h->output);
+ bufchain_add(&h->u.o.queued_data, data, len);
+ handle_try_output(&h->u.o);
+ return bufchain_size(&h->u.o.queued_data);
+}
+
+HANDLE *handle_get_events(int *nevents)
+{
+ HANDLE *ret;
+ struct handle *h;
+ int i, n, size;
+
+ /*
+ * Go through our tree counting the handle objects currently
+ * engaged in useful activity.
+ */
+ ret = NULL;
+ n = size = 0;
+ if (handles_by_evtomain) {
+ for (i = 0; (h = index234(handles_by_evtomain, i)) != NULL; i++) {
+ if (h->u.g.busy) {
+ if (n >= size) {
+ size += 32;
+ ret = sresize(ret, size, HANDLE);
+ }
+ ret[n++] = h->u.g.ev_to_main;
+ }
+ }
+ }
+
+ *nevents = n;
+ return ret;
+}
+
+static void handle_destroy(struct handle *h)
+{
+ if (h->output)
+ bufchain_clear(&h->u.o.queued_data);
+ CloseHandle(h->u.g.ev_from_main);
+ CloseHandle(h->u.g.ev_to_main);
+ del234(handles_by_evtomain, h);
+ sfree(h);
+}
+
+void handle_free(struct handle *h)
+{
+ /*
+ * If the handle is currently busy, we cannot immediately free
+ * it. 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.
+ */
+ assert(h && !h->u.g.moribund);
+ if (h->u.g.busy) {
+ /*
+ * Just 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;
+ SetEvent(h->u.g.ev_from_main);
+ }
+}
+
+void handle_got_event(HANDLE event)
+{
+ struct handle *h;
+
+ assert(handles_by_evtomain);
+ h = find234(handles_by_evtomain, &event, handle_find_evtomain);
+ if (!h) {
+ /*
+ * This isn't an error condition. If two or more event
+ * objects were signalled during the same select operation,
+ * and processing of the first caused the second handle to
+ * be closed, then it will sometimes happen that we receive
+ * an event notification here for a handle which is already
+ * deceased. In that situation we simply do nothing.
+ */
+ return;
+ }
+
+ if (h->u.g.moribund) {
+ /*
+ * A moribund handle is already treated as dead from the
+ * external user's point of view, so do nothing with the
+ * actual event. Just signal the thread to die if
+ * necessary, or destroy the handle if not.
+ */
+ if (h->u.g.done) {
+ handle_destroy(h);
+ } else {
+ h->u.g.done = TRUE;
+ SetEvent(h->u.g.ev_from_main);
+ }
+ return;
+ }
+
+ if (!h->output) {
+ int backlog;
+
+ 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.gotdata(h, NULL, (h->u.i.readret ? 0 : -1));
+ h->u.i.defunct = TRUE;
+ } else {
+ backlog = h->u.i.gotdata(h, h->u.i.buffer, h->u.i.len);
+ handle_throttle(&h->u.i, backlog);
+ }
+ } else {
+ 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.writeret) {
+ /*
+ * 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.sentdata(h, -1);
+ h->u.o.defunct = TRUE;
+ } else {
+ bufchain_consume(&h->u.o.queued_data, h->u.o.lenwritten);
+ h->u.o.sentdata(h, bufchain_size(&h->u.o.queued_data));
+ handle_try_output(&h->u.o);
+ }
+ }
+}
+
+void handle_unthrottle(struct handle *h, int backlog)
+{
+ assert(!h->output);
+ handle_throttle(&h->u.i, backlog);
+}
+
+int handle_backlog(struct handle *h)
+{
+ assert(h->output);
+ return bufchain_size(&h->u.o.queued_data);
+}
projects / u / mdw / putty / blobdiff