/*
* 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);
}