Introduce stackable IO streams

We currently have gitno for talking over TCP, but this needs to know
about both plaintext and OpenSSL connections and the code has gotten
somewhat messy with ifdefs determining which version of the function
should be called.

In order to clean this up and abstract away the details of sending over
the different types of streams, we can instead use an interface and
stack stream implementations.

We may not be able to use the stackability with all streams, but we
are definitely be able to use the abstraction which is currently spread
between different bits of gitno.

include/git2/sys/stream.h

+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_sys_git_stream_h__
+#define INCLUDE_sys_git_stream_h__
+
+#include "git2/common.h"
+#include "git2/types.h"
+
+GIT_BEGIN_DECL
+
+#define GIT_STREAM_VERSION 1
+
+/**
+ * Every stream must have this struct as its first element, so the
+ * API can talk to it. You'd define your stream as
+ *
+ *     struct my_stream {
+ *             git_stream parent;
+ *             ...
+ *     }
+ *
+ * and fill the functions
+ */
+typedef struct git_stream {
+	int version;
+
+	int encrypted;
+	int (*connect)(struct git_stream *);
+	int (*certificate)(git_cert **, struct git_stream *);
+	ssize_t (*read)(struct git_stream *, void *, size_t);
+	ssize_t (*write)(struct git_stream *, void *, size_t, int);
+	int (*close)(struct git_stream *);
+	void (*free)(struct git_stream *);
+} git_stream;
+
+#endif

src/socket_stream.c

+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "common.h"
+#include "posix.h"
+#include "stream.h"
+#include "netops.h"
+
+#ifndef _WIN32
+#	include <sys/types.h>
+#	include <sys/socket.h>
+#	include <sys/select.h>
+#	include <sys/time.h>
+#	include <netdb.h>
+#	include <netinet/in.h>
+#       include <arpa/inet.h>
+#else
+#	include <winsock2.h>
+#	include <ws2tcpip.h>
+#	ifdef _MSC_VER
+#		pragma comment(lib, "ws2_32")
+#	endif
+#endif
+
+#ifdef GIT_WIN32
+static void net_set_error(const char *str)
+{
+	int error = WSAGetLastError();
+	char * win32_error = git_win32_get_error_message(error);
+
+	if (win32_error) {
+		giterr_set(GITERR_NET, "%s: %s", str, win32_error);
+		git__free(win32_error);
+	} else {
+		giterr_set(GITERR_NET, str);
+	}
+}
+#else
+static void net_set_error(const char *str)
+{
+	giterr_set(GITERR_NET, "%s: %s", str, strerror(errno));
+}
+#endif
+
+static int close_socket(GIT_SOCKET s)
+{
+	if (s == INVALID_SOCKET)
+		return 0;
+
+#ifdef GIT_WIN32
+	if (SOCKET_ERROR == closesocket(s))
+		return -1;
+
+	if (0 != WSACleanup()) {
+		giterr_set(GITERR_OS, "Winsock cleanup failed");
+		return -1;
+	}
+
+	return 0;
+#else
+	return close(s);
+#endif
+
+}
+
+typedef struct {
+	git_stream parent;
+	char *host;
+	char *port;
+	GIT_SOCKET s;
+} socket_stream;
+
+int socket_connect(git_stream *stream)
+{
+	struct addrinfo *info = NULL, *p;
+	struct addrinfo hints;
+	socket_stream *st = (socket_stream *) stream;
+	GIT_SOCKET s = INVALID_SOCKET;
+	int ret;
+
+#ifdef GIT_WIN32
+	/* on win32, the WSA context needs to be initialized
+	 * before any socket calls can be performed */
+	WSADATA wsd;
+
+	if (WSAStartup(MAKEWORD(2,2), &wsd) != 0) {
+		giterr_set(GITERR_OS, "Winsock init failed");
+		return -1;
+	}
+
+	if (LOBYTE(wsd.wVersion) != 2 || HIBYTE(wsd.wVersion) != 2) {
+		WSACleanup();
+		giterr_set(GITERR_OS, "Winsock init failed");
+		return -1;
+	}
+#endif
+
+	memset(&hints, 0x0, sizeof(struct addrinfo));
+	hints.ai_socktype = SOCK_STREAM;
+	hints.ai_family = AF_UNSPEC;
+
+	if ((ret = p_getaddrinfo(st->host, st->port, &hints, &info)) != 0) {
+		giterr_set(GITERR_NET,
+
+			   "Failed to resolve address for %s: %s", st->host, p_gai_strerror(ret));
+		return -1;
+	}
+
+	for (p = info; p != NULL; p = p->ai_next) {
+		s = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
+
+		if (s == INVALID_SOCKET) {
+			net_set_error("error creating socket");
+			break;
+		}
+
+		if (connect(s, p->ai_addr, (socklen_t)p->ai_addrlen) == 0)
+			break;
+
+		/* If we can't connect, try the next one */
+		close_socket(s);
+		s = INVALID_SOCKET;
+	}
+
+	/* Oops, we couldn't connect to any address */
+	if (s == INVALID_SOCKET && p == NULL) {
+		giterr_set(GITERR_OS, "Failed to connect to %s", st->host);
+		p_freeaddrinfo(info);
+		return -1;
+	}
+
+	st->s = s;
+	p_freeaddrinfo(info);
+	return 0;
+}
+
+ssize_t socket_write(git_stream *stream, void *data, size_t len, int flags)
+{
+	ssize_t ret;
+	size_t off = 0;
+	socket_stream *st = (socket_stream *) stream;
+
+	while (off < len) {
+		errno = 0;
+		ret = p_send(st->s, data + off, len - off, flags);
+		if (ret < 0) {
+			net_set_error("Error sending data");
+			return -1;
+		}
+
+		off += ret;
+	}
+
+	return off;
+}
+
+ssize_t socket_read(git_stream *stream, void *data, size_t len)
+{
+	ssize_t ret;
+	socket_stream *st = (socket_stream *) stream;
+
+	if ((ret = p_recv(st->s, data, len, 0)) < 0)
+		net_set_error("Error receiving socket data");
+
+	return ret;
+}
+
+int socket_close(git_stream *stream)
+{
+	socket_stream *st = (socket_stream *) stream;
+	int error;
+
+	error = close_socket(st->s);
+	st->s = INVALID_SOCKET;
+
+	return error;
+}
+
+void socket_free(git_stream *stream)
+{
+	socket_stream *st = (socket_stream *) stream;
+
+	git__free(st->host);
+	git__free(st->port);
+	git__free(st);
+}
+
+int git_socket_stream_new(git_stream **out, const char *host, const char *port)
+{
+	socket_stream *st;
+
+	assert(out && host);
+
+	st = git__calloc(1, sizeof(socket_stream));
+	GITERR_CHECK_ALLOC(st);
+
+	st->host = git__strdup(host);
+	GITERR_CHECK_ALLOC(st->host);
+
+	if (port) {
+		st->port = git__strdup(port);
+		GITERR_CHECK_ALLOC(st->port);
+	}
+
+	st->parent.version = GIT_STREAM_VERSION;
+	st->parent.connect = socket_connect;
+	st->parent.write = socket_write;
+	st->parent.read = socket_read;
+	st->parent.close = socket_close;
+	st->parent.free = socket_free;
+	st->s = INVALID_SOCKET;
+
+	*out = (git_stream *) st;
+	return 0;
+}

src/stream.h

+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_stream_h__
+#define INCLUDE_stream_h__
+
+#include "common.h"
+#include "git2/sys/stream.h"
+
+GIT_INLINE(int) git_stream_connect(git_stream *st)
+{
+	return st->connect(st);
+}
+
+GIT_INLINE(int) git_stream_certificate(git_cert **out, git_stream *st)
+{
+	if (!st->encrypted) {
+		giterr_set(GITERR_INVALID, "an unencrypted stream does not have a certificate");
+		return -1;
+	}
+
+	return st->certificate(out, st);
+}
+
+GIT_INLINE(ssize_t) git_stream_read(git_stream *st, void *data, size_t len)
+{
+	return st->read(st, data, len);
+}
+
+GIT_INLINE(ssize_t) git_stream_write(git_stream *st, void *data, size_t len, int flags)
+{
+	return st->write(st, data, len, flags);
+}
+
+GIT_INLINE(int) git_stream_close(git_stream *st)
+{
+	return st->close(st);
+}
+
+GIT_INLINE(void) git_stream_free(git_stream *st)
+{
+	return st->free(st);
+}
+
+#endif