Add Process.runSync for running processe synchronously.

runtime/bin/process_linux.cc

Index: runtime/bin/process_linux.cc
diff --git a/runtime/bin/process_linux.cc b/runtime/bin/process_linux.cc
index 6102e704e6c4ed4cfc06ebd7de754a1d70542e21..47564c25145fdd145583b9d9f4317245e0aa1a20 100644
--- a/runtime/bin/process_linux.cc
+++ b/runtime/bin/process_linux.cc
@@ -568,6 +568,122 @@ int Process::Start(const char* path,
 }
 
 
+static bool ReadProcessBuffer(uint8_t** buffer,
+                              intptr_t* buffer_length,
+                              intptr_t available,
+                              int fd) {
+  uint8_t* tmp = new uint8_t[*buffer_length + available];
+  if (tmp == NULL) FATAL("Allocation failed");
+  memmove(tmp, *buffer, *buffer_length);
+  delete[] *buffer;
+  *buffer = tmp;
+  intptr_t bytes = TEMP_FAILURE_RETRY(read(
+      fd,
+      reinterpret_cast<void*>(*buffer + *buffer_length),
+      available));
+  if (bytes < 0) return false;
+  *buffer_length += bytes;
+  return true;
+}
+
+
+static bool CloseProcessBuffers(struct pollfd fds[3]) {
+  int e = errno;
+  VOID_TEMP_FAILURE_RETRY(close(fds[0].fd));
+  VOID_TEMP_FAILURE_RETRY(close(fds[1].fd));
+  VOID_TEMP_FAILURE_RETRY(close(fds[2].fd));
+  errno = e;
+  return false;
+}
+
+
+bool Process::Wait(intptr_t pid,
+                   intptr_t in,
+                   intptr_t out,
+                   intptr_t err,
+                   intptr_t exit_event,
+                   ProcessResult* result) {
+  // Close input to the process right away.
+  VOID_TEMP_FAILURE_RETRY(close(in));
+
+  uint8_t* out_data = NULL;
+  intptr_t out_data_length = 0;
+  uint8_t* err_data = NULL;
+  intptr_t err_data_length = 0;
+  union {
+    uint8_t bytes[8];
+    int32_t ints[2];
+  } exit_code_data;
+
+  struct pollfd fds[3];
+  fds[0].fd = out;
+  fds[1].fd = err;
+  fds[2].fd = exit_event;
+
+  for (int i = 0; i < 3; i++) {
+    fds[i].events = POLLIN;
+  }
+
+  int alive = 3;
+  while (alive > 0) {
+    if (TEMP_FAILURE_RETRY(poll(fds, alive, -1)) <= 0) {

[Bill Hesse, 2013/08/09 15:32:23]

Add comment - blocking call.  This implements a Dart synchronous function that
can block - the only one.

[Søren Gjesse, 2013/08/12 06:52:38]

Done.

+      return CloseProcessBuffers(fds);
+    }
+    for (int i = 0; i < alive; i++) {
+      if (fds[i].revents & POLLIN) {
+        intptr_t avail = FDUtils::AvailableBytes(fds[i].fd);
+        if (fds[i].fd == out) {
+          if (!ReadProcessBuffer(&out_data, &out_data_length, avail, out)) {
+            return CloseProcessBuffers(fds);
+          }
+        } else if (fds[i].fd == err) {
+          if (!ReadProcessBuffer(&err_data, &err_data_length, avail, err)) {
+            return CloseProcessBuffers(fds);
+          }
+        } else if (fds[i].fd == exit_event) {
+          intptr_t avail = FDUtils::AvailableBytes(fds[i].fd);
+          if (avail == 8) {
+            intptr_t bytes = 0;
+            do {
+              intptr_t b = TEMP_FAILURE_RETRY(read(fds[i].fd,
+                                                   exit_code_data.bytes, 8));

[Bill Hesse, 2013/08/09 15:32:23]

shouldn't this be read(fds[i].fd, exit_code_data.bytes + bytes, 8)

(or 8 - bytes)?

[Søren Gjesse, 2013/08/12 06:52:38]

Removed the while, as we know that there are 8 bytes available.

+              if (b > 0) {
+                bytes += b;
+              } else {
+                return CloseProcessBuffers(fds);
+              }
+            } while (bytes < 8);
+          }
+        } else {
+          UNREACHABLE();
+        }
+        continue;
+      }
+
+      if (fds[i].revents & POLLHUP) {
+        VOID_TEMP_FAILURE_RETRY(close(fds[i].fd));
+        alive--;
+        if (i < alive) {

[Bill Hesse, 2013/08/09 15:32:23]

This guard is not really needed.  But it is OK, since it skips unneeded work.

[Søren Gjesse, 2013/08/12 06:52:38]

This is needed as calling poll with closed file descriptors will fail with
invalid argument error.

+          fds[i] = fds[alive];
+        }
+      }
+    }
+  }
+
+  // All handles closed and all data read.
+  result->SetStdoutData(out_data, out_data_length);
+  result->SetStderrData(err_data, err_data_length);
+
+  // Calculate the exit code.
+  intptr_t exit_code = exit_code_data.ints[0];
+  intptr_t negative = exit_code_data.ints[1];
+  if (negative) exit_code = -exit_code;
+  result->set_exit_code(exit_code);
+
+  return true;
+}
+
+
 bool Process::Kill(intptr_t id, int signal) {
   return (TEMP_FAILURE_RETRY(kill(id, signal)) != -1);
 }