Initial checkin of gRPC to third_party/

third_party/grpc/src/objective-c/RxLibrary/GRXImmediateWriter.m

+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#import "GRXImmediateWriter.h"
+
+#import "NSEnumerator+GRXUtil.h"
+
+@implementation GRXImmediateWriter {
+  NSEnumerator *_enumerator;
+  NSError *_errorOrNil;
+  id<GRXWriteable> _writeable;
+}
+
+@synthesize state = _state;
+
+- (instancetype) init {
+  return [self initWithEnumerator:nil error:nil]; // results in an empty writer.
+}
+
+// Designated initializer
+- (instancetype)initWithEnumerator:(NSEnumerator *)enumerator error:(NSError *)errorOrNil {
+  if (((self = [super init]))) {
+    _enumerator = enumerator;
+    _errorOrNil = errorOrNil;
+    _state = GRXWriterStateNotStarted;
+  }
+  return self;
+}
+
+#pragma mark Convenience constructors
+
++ (instancetype)writerWithEnumerator:(NSEnumerator *)enumerator error:(NSError *)errorOrNil {
+  return [[self alloc] initWithEnumerator:enumerator error:errorOrNil];
+}
+
++ (GRXWriter *)writerWithEnumerator:(NSEnumerator *)enumerator {
+  return [self writerWithEnumerator:enumerator error:nil];
+}
+
++ (GRXWriter *)writerWithValueSupplier:(id (^)())block {
+  return [self writerWithEnumerator:[NSEnumerator grx_enumeratorWithValueSupplier:block]];
+}
+
++ (GRXWriter *)writerWithContainer:(id<NSFastEnumeration>)container {
+  return [self writerWithEnumerator:[NSEnumerator grx_enumeratorWithContainer:container]];;
+}
+
++ (GRXWriter *)writerWithValue:(id)value {
+  return [self writerWithEnumerator:[NSEnumerator grx_enumeratorWithSingleValue:value]];
+}
+
++ (GRXWriter *)writerWithError:(NSError *)error {
+  return [self writerWithEnumerator:nil error:error];
+}
+
++ (GRXWriter *)emptyWriter {
+  return [self writerWithEnumerator:nil error:nil];
+}
+
+#pragma mark Conformance with GRXWriter
+
+// Most of the complexity in this implementation is the result of supporting pause and resumption of
+// the GRXWriter. It's an important feature for instances of GRXWriter that are backed by a
+// container (which may be huge), or by a NSEnumerator (which may even be infinite).
+
+- (void)writeUntilPausedOrStopped {
+  id value;
+  while (value = [_enumerator nextObject]) {
+    [_writeable writeValue:value];
+    // If the writeable has a reference to us, it might change our state to paused or finished.
+    if (_state == GRXWriterStatePaused || _state == GRXWriterStateFinished) {
+      return;
+    }
+  }
+  [self finishWithError:_errorOrNil];
+}
+
+- (void)startWithWriteable:(id<GRXWriteable>)writeable {
+  _state = GRXWriterStateStarted;
+  _writeable = writeable;
+  [self writeUntilPausedOrStopped];
+}
+
+- (void)finishWithError:(NSError *)errorOrNil {
+  _state = GRXWriterStateFinished;
+  _enumerator = nil;
+  _errorOrNil = nil;
+  id<GRXWriteable> writeable = _writeable;
+  _writeable = nil;
+  [writeable writesFinishedWithError:errorOrNil];
+}
+
+- (void)setState:(GRXWriterState)newState {
+  // Manual transitions are only allowed from the started or paused states.
+  if (_state == GRXWriterStateNotStarted || _state == GRXWriterStateFinished) {
+    return;
+  }
+
+  switch (newState) {
+    case GRXWriterStateFinished:
+      _state = newState;
+      _enumerator = nil;
+      _errorOrNil = nil;
+      // Per GRXWriter's contract, setting the state to Finished manually
+      // means one doesn't wish the writeable to be messaged anymore.
+      _writeable = nil;
+      return;
+    case GRXWriterStatePaused:
+      _state = newState;
+      return;
+    case GRXWriterStateStarted:
+      if (_state == GRXWriterStatePaused) {
+        _state = newState;
+        [self writeUntilPausedOrStopped];
+      }
+      return;
+    case GRXWriterStateNotStarted:
+      return;
+  }
+}
+
+@end