Factor out the HANDLE-to-Socket adapter from winproxy.c.

It's now kept in a separate module, where it can be reused
conveniently for other kinds of Windows HANDLE that I want to wrap in
the PuTTY Socket abstraction - for example, the named pipes that I
shortly plan to use for the Windows side of connection-sharing IPC.

[originally from svn r10066]

windows/winhsock.c

@@ -0,0 +1,159 @@
+/*
+ * General mechanism for wrapping up reading/writing of Windows
+ * HANDLEs into a PuTTY Socket abstraction.
+ */
+
+#include <stdio.h>
+#include <assert.h>
+
+#define DEFINE_PLUG_METHOD_MACROS
+#include "tree234.h"
+#include "putty.h"
+#include "network.h"
+
+typedef struct Socket_handle_tag *Handle_Socket;
+
+struct Socket_handle_tag {
+    const struct socket_function_table *fn;
+    /* the above variable absolutely *must* be the first in this structure */
+
+    HANDLE send_H, recv_H;
+    struct handle *send_h, *recv_h;
+
+    char *error;
+
+    Plug plug;
+
+    void *privptr;
+};
+
+static int handle_gotdata(struct handle *h, void *data, int len)
+{
+    Handle_Socket ps = (Handle_Socket) handle_get_privdata(h);
+
+    if (len < 0) {
+	return plug_closing(ps->plug, "Read error from handle",
+			    0, 0);
+    } else if (len == 0) {
+	return plug_closing(ps->plug, NULL, 0, 0);
+    } else {
+	return plug_receive(ps->plug, 0, data, len);
+    }
+}
+
+static void handle_sentdata(struct handle *h, int new_backlog)
+{
+    Handle_Socket ps = (Handle_Socket) handle_get_privdata(h);
+    
+    plug_sent(ps->plug, new_backlog);
+}
+
+static Plug sk_handle_plug(Socket s, Plug p)
+{
+    Handle_Socket ps = (Handle_Socket) s;
+    Plug ret = ps->plug;
+    if (p)
+	ps->plug = p;
+    return ret;
+}
+
+static void sk_handle_close(Socket s)
+{
+    Handle_Socket ps = (Handle_Socket) s;
+
+    handle_free(ps->send_h);
+    handle_free(ps->recv_h);
+    CloseHandle(ps->send_H);
+    if (ps->recv_H != ps->send_H)
+        CloseHandle(ps->recv_H);
+
+    sfree(ps);
+}
+
+static int sk_handle_write(Socket s, const char *data, int len)
+{
+    Handle_Socket ps = (Handle_Socket) s;
+
+    return handle_write(ps->send_h, data, len);
+}
+
+static int sk_handle_write_oob(Socket s, const char *data, int len)
+{
+    /*
+     * oob data is treated as inband; nasty, but nothing really
+     * better we can do
+     */
+    return sk_handle_write(s, data, len);
+}
+
+static void sk_handle_write_eof(Socket s)
+{
+    Handle_Socket ps = (Handle_Socket) s;
+
+    handle_write_eof(ps->send_h);
+}
+
+static void sk_handle_flush(Socket s)
+{
+    /* Handle_Socket ps = (Handle_Socket) s; */
+    /* do nothing */
+}
+
+static void sk_handle_set_private_ptr(Socket s, void *ptr)
+{
+    Handle_Socket ps = (Handle_Socket) s;
+    ps->privptr = ptr;
+}
+
+static void *sk_handle_get_private_ptr(Socket s)
+{
+    Handle_Socket ps = (Handle_Socket) s;
+    return ps->privptr;
+}
+
+static void sk_handle_set_frozen(Socket s, int is_frozen)
+{
+    Handle_Socket ps = (Handle_Socket) s;
+
+    /*
+     * FIXME
+     */
+}
+
+static const char *sk_handle_socket_error(Socket s)
+{
+    Handle_Socket ps = (Handle_Socket) s;
+    return ps->error;
+}
+
+Socket make_handle_socket(HANDLE send_H, HANDLE recv_H, Plug plug,
+                          int overlapped)
+{
+    static const struct socket_function_table socket_fn_table = {
+	sk_handle_plug,
+	sk_handle_close,
+	sk_handle_write,
+	sk_handle_write_oob,
+	sk_handle_write_eof,
+	sk_handle_flush,
+	sk_handle_set_private_ptr,
+	sk_handle_get_private_ptr,
+	sk_handle_set_frozen,
+	sk_handle_socket_error
+    };
+
+    Handle_Socket ret;
+    int flags = (overlapped ? HANDLE_FLAG_OVERLAPPED : 0);
+
+    ret = snew(struct Socket_handle_tag);
+    ret->fn = &socket_fn_table;
+    ret->plug = plug;
+    ret->error = NULL;
+
+    ret->recv_H = recv_H;
+    ret->recv_h = handle_input_new(ret->recv_H, handle_gotdata, ret, flags);
+    ret->send_H = send_H;
+    ret->send_h = handle_output_new(ret->send_H, handle_sentdata, ret, flags);
+
+    return (Socket) ret;
+}