Add bidirectional_transfer_loop()

This helper function copies bidirectional stream of data between
stdin/stdout and specified file descriptors.

Signed-off-by: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/compat/mingw.h b/compat/mingw.h
index 3b2477be5f658be665f19a12b48cc47fa07d1c6b..f27a7b69b1e30a560d8b17fc9613b065c37afe0a 100644 (file)
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -23,6 +23,9 @@ typedef int pid_t;
 #define WEXITSTATUS(x) ((x) & 0xff)
 #define WTERMSIG(x) SIGTERM
 
+#define EWOULDBLOCK EAGAIN
+#define SHUT_WR SD_SEND
+
 #define SIGHUP 1
 #define SIGQUIT 3
 #define SIGKILL 9
@@ -50,6 +53,8 @@ struct pollfd {
 };
 #define POLLIN 1
 #define POLLHUP 2
+#define POLLOUT 4
+#define POLLNVAL 8
 #endif
 
 typedef void (__cdecl *sig_handler_t)(int);

diff --git a/transport-helper.c b/transport-helper.c
index acfc88e3f1f0e99863512bf2c6ea82f1283cc35d..0c094d66c1e39423b9c0765c7690113b685c6cdc 100644 (file)
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -862,3 +862,314 @@ int transport_helper_init(struct transport *transport, const char *name)
        transport->smart_options = &(data->transport_options);
        return 0;
 }
+
+/*
+ * Linux pipes can buffer 65536 bytes at once (and most platforms can
+ * buffer less), so attempt reads and writes with up to that size.
+ */
+#define BUFFERSIZE 65536
+/* This should be enough to hold debugging message. */
+#define PBUFFERSIZE 8192
+
+/* Print bidirectional transfer loop debug message. */
+static void transfer_debug(const char *fmt, ...)
+{
+       va_list args;
+       char msgbuf[PBUFFERSIZE];
+       static int debug_enabled = -1;
+
+       if (debug_enabled < 0)
+               debug_enabled = getenv("GIT_TRANSLOOP_DEBUG") ? 1 : 0;
+       if (!debug_enabled)
+               return;
+
+       va_start(args, fmt);
+       vsnprintf(msgbuf, PBUFFERSIZE, fmt, args);
+       va_end(args);
+       fprintf(stderr, "Transfer loop debugging: %s\n", msgbuf);
+}
+
+/* Stream state: More data may be coming in this direction. */
+#define SSTATE_TRANSFERING 0
+/*
+ * Stream state: No more data coming in this direction, flushing rest of
+ * data.
+ */
+#define SSTATE_FLUSHING 1
+/* Stream state: Transfer in this direction finished. */
+#define SSTATE_FINISHED 2
+
+#define STATE_NEEDS_READING(state) ((state) <= SSTATE_TRANSFERING)
+#define STATE_NEEDS_WRITING(state) ((state) <= SSTATE_FLUSHING)
+#define STATE_NEEDS_CLOSING(state) ((state) == SSTATE_FLUSHING)
+
+/* Unidirectional transfer. */
+struct unidirectional_transfer {
+       /* Source */
+       int src;
+       /* Destination */
+       int dest;
+       /* Is source socket? */
+       int src_is_sock;
+       /* Is destination socket? */
+       int dest_is_sock;
+       /* Transfer state (TRANSFERING/FLUSHING/FINISHED) */
+       int state;
+       /* Buffer. */
+       char buf[BUFFERSIZE];
+       /* Buffer used. */
+       size_t bufuse;
+       /* Name of source. */
+       const char *src_name;
+       /* Name of destination. */
+       const char *dest_name;
+};
+
+/* Closes the target (for writing) if transfer has finished. */
+static void udt_close_if_finished(struct unidirectional_transfer *t)
+{
+       if (STATE_NEEDS_CLOSING(t->state) && !t->bufuse) {
+               t->state = SSTATE_FINISHED;
+               if (t->dest_is_sock)
+                       shutdown(t->dest, SHUT_WR);
+               else
+                       close(t->dest);
+               transfer_debug("Closed %s.", t->dest_name);
+       }
+}
+
+/*
+ * Tries to read read data from source into buffer. If buffer is full,
+ * no data is read. Returns 0 on success, -1 on error.
+ */
+static int udt_do_read(struct unidirectional_transfer *t)
+{
+       ssize_t bytes;
+
+       if (t->bufuse == BUFFERSIZE)
+               return 0;       /* No space for more. */
+
+       transfer_debug("%s is readable", t->src_name);
+       bytes = read(t->src, t->buf + t->bufuse, BUFFERSIZE - t->bufuse);
+       if (bytes < 0 && errno != EWOULDBLOCK && errno != EAGAIN &&
+               errno != EINTR) {
+               error("read(%s) failed: %s", t->src_name, strerror(errno));
+               return -1;
+       } else if (bytes == 0) {
+               transfer_debug("%s EOF (with %i bytes in buffer)",
+                       t->src_name, t->bufuse);
+               t->state = SSTATE_FLUSHING;
+       } else if (bytes > 0) {
+               t->bufuse += bytes;
+               transfer_debug("Read %i bytes from %s (buffer now at %i)",
+                       (int)bytes, t->src_name, (int)t->bufuse);
+       }
+       return 0;
+}
+
+/* Tries to write data from buffer into destination. If buffer is empty,
+ * no data is written. Returns 0 on success, -1 on error.
+ */
+static int udt_do_write(struct unidirectional_transfer *t)
+{
+       size_t bytes;
+
+       if (t->bufuse == 0)
+               return 0;       /* Nothing to write. */
+
+       transfer_debug("%s is writable", t->dest_name);
+       bytes = write(t->dest, t->buf, t->bufuse);
+       if (bytes < 0 && errno != EWOULDBLOCK && errno != EAGAIN &&
+               errno != EINTR) {
+               error("write(%s) failed: %s", t->dest_name, strerror(errno));
+               return -1;
+       } else if (bytes > 0) {
+               t->bufuse -= bytes;
+               if (t->bufuse)
+                       memmove(t->buf, t->buf + bytes, t->bufuse);
+               transfer_debug("Wrote %i bytes to %s (buffer now at %i)",
+                       (int)bytes, t->dest_name, (int)t->bufuse);
+       }
+       return 0;
+}
+
+
+/* State of bidirectional transfer loop. */
+struct bidirectional_transfer_state {
+       /* Direction from program to git. */
+       struct unidirectional_transfer ptg;
+       /* Direction from git to program. */
+       struct unidirectional_transfer gtp;
+};
+
+static void *udt_copy_task_routine(void *udt)
+{
+       struct unidirectional_transfer *t = (struct unidirectional_transfer *)udt;
+       while (t->state != SSTATE_FINISHED) {
+               if (STATE_NEEDS_READING(t->state))
+                       if (udt_do_read(t))
+                               return NULL;
+               if (STATE_NEEDS_WRITING(t->state))
+                       if (udt_do_write(t))
+                               return NULL;
+               if (STATE_NEEDS_CLOSING(t->state))
+                       udt_close_if_finished(t);
+       }
+       return udt;     /* Just some non-NULL value. */
+}
+
+#ifndef NO_PTHREADS
+
+/*
+ * Join thread, with apporiate errors on failure. Name is name for the
+ * thread (for error messages). Returns 0 on success, 1 on failure.
+ */
+static int tloop_join(pthread_t thread, const char *name)
+{
+       int err;
+       void *tret;
+       err = pthread_join(thread, &tret);
+       if (!tret) {
+               error("%s thread failed", name);
+               return 1;
+       }
+       if (err) {
+               error("%s thread failed to join: %s", name, strerror(err));
+               return 1;
+       }
+       return 0;
+}
+
+/*
+ * Spawn the transfer tasks and then wait for them. Returns 0 on success,
+ * -1 on failure.
+ */
+static int tloop_spawnwait_tasks(struct bidirectional_transfer_state *s)
+{
+       pthread_t gtp_thread;
+       pthread_t ptg_thread;
+       int err;
+       int ret = 0;
+       err = pthread_create(&gtp_thread, NULL, udt_copy_task_routine,
+               &s->gtp);
+       if (err)
+               die("Can't start thread for copying data: %s", strerror(err));
+       err = pthread_create(&ptg_thread, NULL, udt_copy_task_routine,
+               &s->ptg);
+       if (err)
+               die("Can't start thread for copying data: %s", strerror(err));
+
+       ret |= tloop_join(gtp_thread, "Git to program copy");
+       ret |= tloop_join(ptg_thread, "Program to git copy");
+       return ret;
+}
+#else
+
+/* Close the source and target (for writing) for transfer. */
+static void udt_kill_transfer(struct unidirectional_transfer *t)
+{
+       t->state = SSTATE_FINISHED;
+       /*
+        * Socket read end left open isn't a disaster if nobody
+        * attempts to read from it (mingw compat headers do not
+        * have SHUT_RD)...
+        *
+        * We can't fully close the socket since otherwise gtp
+        * task would first close the socket it sends data to
+        * while closing the ptg file descriptors.
+        */
+       if (!t->src_is_sock)
+               close(t->src);
+       if (t->dest_is_sock)
+               shutdown(t->dest, SHUT_WR);
+       else
+               close(t->dest);
+}
+
+/*
+ * Join process, with apporiate errors on failure. Name is name for the
+ * process (for error messages). Returns 0 on success, 1 on failure.
+ */
+static int tloop_join(pid_t pid, const char *name)
+{
+       int tret;
+       if (waitpid(pid, &tret, 0) < 0) {
+               error("%s process failed to wait: %s", name, strerror(errno));
+               return 1;
+       }
+       if (!WIFEXITED(tret) || WEXITSTATUS(tret)) {
+               error("%s process failed", name);
+               return 1;
+       }
+       return 0;
+}
+
+/*
+ * Spawn the transfer tasks and then wait for them. Returns 0 on success,
+ * -1 on failure.
+ */
+static int tloop_spawnwait_tasks(struct bidirectional_transfer_state *s)
+{
+       pid_t pid1, pid2;
+       int ret = 0;
+
+       /* Fork thread #1: git to program. */
+       pid1 = fork();
+       if (pid1 < 0)
+               die_errno("Can't start thread for copying data");
+       else if (pid1 == 0) {
+               udt_kill_transfer(&s->ptg);
+               exit(udt_copy_task_routine(&s->gtp) ? 0 : 1);
+       }
+
+       /* Fork thread #2: program to git. */
+       pid2 = fork();
+       if (pid2 < 0)
+               die_errno("Can't start thread for copying data");
+       else if (pid2 == 0) {
+               udt_kill_transfer(&s->gtp);
+               exit(udt_copy_task_routine(&s->ptg) ? 0 : 1);
+       }
+
+       /*
+        * Close both streams in parent as to not interfere with
+        * end of file detection and wait for both tasks to finish.
+        */
+       udt_kill_transfer(&s->gtp);
+       udt_kill_transfer(&s->ptg);
+       ret |= tloop_join(pid1, "Git to program copy");
+       ret |= tloop_join(pid2, "Program to git copy");
+       return ret;
+}
+#endif
+
+/*
+ * Copies data from stdin to output and from input to stdout simultaneously.
+ * Additionally filtering through given filter. If filter is NULL, uses
+ * identity filter.
+ */
+int bidirectional_transfer_loop(int input, int output)
+{
+       struct bidirectional_transfer_state state;
+
+       /* Fill the state fields. */
+       state.ptg.src = input;
+       state.ptg.dest = 1;
+       state.ptg.src_is_sock = (input == output);
+       state.ptg.dest_is_sock = 0;
+       state.ptg.state = SSTATE_TRANSFERING;
+       state.ptg.bufuse = 0;
+       state.ptg.src_name = "remote input";
+       state.ptg.dest_name = "stdout";
+
+       state.gtp.src = 0;
+       state.gtp.dest = output;
+       state.gtp.src_is_sock = 0;
+       state.gtp.dest_is_sock = (input == output);
+       state.gtp.state = SSTATE_TRANSFERING;
+       state.gtp.bufuse = 0;
+       state.gtp.src_name = "stdin";
+       state.gtp.dest_name = "remote output";
+
+       return tloop_spawnwait_tasks(&state);
+}

diff --git a/transport.h b/transport.h
index c59d97388e6fdb1dccd4dca0d41dccc3d129f8fb..e803c0e7baf3785fac35fca64072e05e4f668a26 100644 (file)
--- a/transport.h
+++ b/transport.h
@@ -154,6 +154,7 @@ int transport_connect(struct transport *transport, const char *name,
 
 /* Transport methods defined outside transport.c */
 int transport_helper_init(struct transport *transport, const char *name);
+int bidirectional_transfer_loop(int input, int output);
 
 /* common methods used by transport.c and builtin-send-pack.c */
 void transport_verify_remote_names(int nr_heads, const char **heads);