Show bundle download progress on iOS

Summary:
This shows progress for the download of the JS bundle (different from the packager transform progress that we show already). This is useful especially when loading the JS bundle from a remote source or when developing on device (on simulator + localhost it pretty much just downloads instantly). This will be nice for the expo client since all bundles are loaded over the network and can take several seconds to load.

This depends on facebook/metro#28 to work but won't crash or anything without it, it just won't show the progress percentage.

![img_05070155d2cc-1](https://user-images.githubusercontent.com/2677334/28293828-2c08d974-6b24-11e7-9334-e106ef3326d9.jpeg)

**Test plan**
Tested that bundle download progress is shown properly in RNTester on both localhost + simulator and on real device with network conditionner to simulate a slow loading bundle.

Tested that it doesn't cause issues if the packager doesn't send the Content-Length header.
Closes #15066

Differential Revision: D5449073

Pulled By: shergin

fbshipit-source-id: 43a8fb559393bbdc04f77916500e21898695bac5

Author: janicduplessis

RNTester/RNTesterUnitTests/RCTMultipartStreamReaderTests.m

@@ -31,12 +31,12 @@ - (void)testSimpleCase {
   NSInputStream *inputStream = [NSInputStream inputStreamWithData:[response dataUsingEncoding:NSUTF8StringEncoding]];
   RCTMultipartStreamReader *reader = [[RCTMultipartStreamReader alloc] initWithInputStream:inputStream boundary:@"sample_boundary"];
   __block NSInteger count = 0;
-  BOOL success = [reader readAllParts:^(NSDictionary *headers, NSData *content, BOOL done) {
+  BOOL success = [reader readAllPartsWithCompletionCallback:^(NSDictionary *headers, NSData *content, BOOL done) {
     XCTAssertTrue(done);
     XCTAssertEqualObjects(headers[@"Content-Type"], @"application/json; charset=utf-8");
     XCTAssertEqualObjects([[NSString alloc] initWithData:content encoding:NSUTF8StringEncoding], @"{}");
     count++;
-  }];
+  } progressCallback: nil];
   XCTAssertTrue(success);
   XCTAssertEqual(count, 1);
 }
@@ -56,13 +56,13 @@ - (void)testMultipleParts {
   NSInputStream *inputStream = [NSInputStream inputStreamWithData:[response dataUsingEncoding:NSUTF8StringEncoding]];
   RCTMultipartStreamReader *reader = [[RCTMultipartStreamReader alloc] initWithInputStream:inputStream boundary:@"sample_boundary"];
   __block NSInteger count = 0;
-  BOOL success = [reader readAllParts:^(__unused NSDictionary *headers, NSData *content, BOOL done) {
+  BOOL success = [reader readAllPartsWithCompletionCallback:^(__unused NSDictionary *headers, NSData *content, BOOL done) {
     count++;
     XCTAssertEqual(done, count == 3);
     NSString *expectedBody = [NSString stringWithFormat:@"%ld", (long)count];
     NSString *actualBody = [[NSString alloc] initWithData:content encoding:NSUTF8StringEncoding];
     XCTAssertEqualObjects(actualBody, expectedBody);
-  }];
+  } progressCallback:nil];
   XCTAssertTrue(success);
   XCTAssertEqual(count, 3);
 }
@@ -73,9 +73,9 @@ - (void)testNoDelimiter {
   NSInputStream *inputStream = [NSInputStream inputStreamWithData:[response dataUsingEncoding:NSUTF8StringEncoding]];
   RCTMultipartStreamReader *reader = [[RCTMultipartStreamReader alloc] initWithInputStream:inputStream boundary:@"sample_boundary"];
   __block NSInteger count = 0;
-  BOOL success = [reader readAllParts:^(__unused NSDictionary *headers, __unused NSData *content, __unused BOOL done) {
+  BOOL success = [reader readAllPartsWithCompletionCallback:^(__unused NSDictionary *headers, __unused NSData *content, __unused BOOL done) {
     count++;
-  }];
+  } progressCallback:nil];
   XCTAssertFalse(success);
   XCTAssertEqual(count, 0);
 }
@@ -93,9 +93,9 @@ - (void)testNoCloseDelimiter {
   NSInputStream *inputStream = [NSInputStream inputStreamWithData:[response dataUsingEncoding:NSUTF8StringEncoding]];
   RCTMultipartStreamReader *reader = [[RCTMultipartStreamReader alloc] initWithInputStream:inputStream boundary:@"sample_boundary"];
   __block NSInteger count = 0;
-  BOOL success = [reader readAllParts:^(__unused NSDictionary *headers, __unused NSData *content, __unused BOOL done) {
+  BOOL success = [reader readAllPartsWithCompletionCallback:^(__unused NSDictionary *headers, __unused NSData *content, __unused BOOL done) {
     count++;
-  }];
+  } progressCallback:nil];
   XCTAssertFalse(success);
   XCTAssertEqual(count, 1);
 }

React/Base/RCTJavaScriptLoader.mm

@@ -198,7 +198,6 @@ static void attemptAsynchronousLoadOfBundleAtURL(NSURL *scriptURL, RCTSourceLoad
     return;
   }
 
-
   RCTMultipartDataTask *task = [[RCTMultipartDataTask alloc] initWithURL:scriptURL partHandler:^(NSInteger statusCode, NSDictionary *headers, NSData *data, NSError *error, BOOL done) {
     if (!done) {
       if (onProgress) {
@@ -261,6 +260,11 @@ static void attemptAsynchronousLoadOfBundleAtURL(NSURL *scriptURL, RCTSourceLoad
     }
 
     onComplete(nil, data, data.length);
+  } progressHandler:^(NSDictionary *headers, NSNumber *loaded, NSNumber *total) {
+    // Only care about download progress events for the javascript bundle part.
+    if ([headers[@"Content-Type"] isEqualToString:@"application/javascript"]) {
+      onProgress(progressEventFromDownloadProgress(loaded, total));
+    }
   }];
 
   [task startTask];
@@ -287,6 +291,16 @@ static void attemptAsynchronousLoadOfBundleAtURL(NSURL *scriptURL, RCTSourceLoad
   return progress;
 }
 
+static RCTLoadingProgress *progressEventFromDownloadProgress(NSNumber *total, NSNumber *done)
+{
+  RCTLoadingProgress *progress = [RCTLoadingProgress new];
+  progress.status = @"Downloading JavaScript bundle";
+  // Progress values are in bytes transform them to kilobytes for smaller numbers.
+  progress.done = done != nil ? @([done integerValue] / 1024) : nil;
+  progress.total = total != nil ? @([total integerValue] / 1024) : nil;
+  return progress;
+}
+
 static NSDictionary *userInfoForRawResponse(NSString *rawText)
 {
   NSDictionary *parsedResponse = RCTJSONParse(rawText, nil);

React/Base/RCTMultipartDataTask.h

@@ -15,7 +15,10 @@ typedef void (^RCTMultipartDataTaskCallback)(NSInteger statusCode, NSDictionary
 
 @interface RCTMultipartDataTask : NSObject
 
-- (instancetype)initWithURL:(NSURL *)url partHandler:(RCTMultipartDataTaskCallback)partHandler;
+- (instancetype)initWithURL:(NSURL *)url
+                partHandler:(RCTMultipartDataTaskCallback)partHandler
+            progressHandler:(RCTMultipartProgressCallback)progressHandler;
+
 - (void)startTask;
 
 @end

React/Base/RCTMultipartDataTask.m

@@ -30,17 +30,21 @@ static BOOL isStreamTaskSupported() {
 @implementation RCTMultipartDataTask {
   NSURL *_url;
   RCTMultipartDataTaskCallback _partHandler;
+  RCTMultipartProgressCallback _progressHandler;
   NSInteger _statusCode;
   NSDictionary *_headers;
   NSString *_boundary;
   NSMutableData *_data;
 }
 
-- (instancetype)initWithURL:(NSURL *)url partHandler:(RCTMultipartDataTaskCallback)partHandler
+- (instancetype)initWithURL:(NSURL *)url
+                partHandler:(RCTMultipartDataTaskCallback)partHandler
+            progressHandler:(RCTMultipartProgressCallback)progressHandler
 {
   if (self = [super init]) {
     _url = url;
     _partHandler = [partHandler copy];
+    _progressHandler = [progressHandler copy];
   }
   return self;
 }
@@ -117,9 +121,9 @@ - (void)URLSession:(__unused NSURLSession *)session
   _partHandler = nil;
   NSInteger statusCode = _statusCode;
 
-  BOOL completed = [reader readAllParts:^(NSDictionary *headers, NSData *content, BOOL done) {
+  BOOL completed = [reader readAllPartsWithCompletionCallback:^(NSDictionary *headers, NSData *content, BOOL done) {
     partHandler(statusCode, headers, content, nil, done);
-  }];
+  } progressCallback:_progressHandler];
   if (!completed) {
     partHandler(statusCode, nil, nil, [NSError errorWithDomain:NSURLErrorDomain code:NSURLErrorCancelled userInfo:nil], YES);
   }

React/Base/RCTMultipartStreamReader.h

@@ -10,13 +10,15 @@
 #import <Foundation/Foundation.h>
 
 typedef void (^RCTMultipartCallback)(NSDictionary *headers, NSData *content, BOOL done);
+typedef void (^RCTMultipartProgressCallback)(NSDictionary *headers, NSNumber *loaded, NSNumber *total);
 
 
 // RCTMultipartStreamReader can be used to parse responses with Content-Type: multipart/mixed
 // See https://www.w3.org/Protocols/rfc1341/7_2_Multipart.html
 @interface RCTMultipartStreamReader : NSObject
 
 - (instancetype)initWithInputStream:(NSInputStream *)stream boundary:(NSString *)boundary;
-- (BOOL)readAllParts:(RCTMultipartCallback)callback;
+- (BOOL)readAllPartsWithCompletionCallback:(RCTMultipartCallback)callback
+                          progressCallback:(RCTMultipartProgressCallback)progressCallback;
 
 @end

React/Base/RCTMultipartStreamReader.m

@@ -9,18 +9,22 @@
 
 #import "RCTMultipartStreamReader.h"
 
+#import <QuartzCore/CAAnimation.h>
+
 #define CRLF @"\r\n"
 
 @implementation RCTMultipartStreamReader {
   __strong NSInputStream *_stream;
   __strong NSString *_boundary;
+  CFTimeInterval _lastDownloadProgress;
 }
 
 - (instancetype)initWithInputStream:(NSInputStream *)stream boundary:(NSString *)boundary
 {
   if (self = [super init]) {
     _stream = stream;
     _boundary = boundary;
+    _lastDownloadProgress = CACurrentMediaTime();
   }
   return self;
 }
@@ -42,12 +46,17 @@ - (NSDictionary *)parseHeaders:(NSData *)data
   return headers;
 }
 
-- (void)emitChunk:(NSData *)data callback:(RCTMultipartCallback)callback done:(BOOL)done
+- (void)emitChunk:(NSData *)data headers:(NSDictionary *)headers callback:(RCTMultipartCallback)callback done:(BOOL)done
 {
   NSData *marker = [CRLF CRLF dataUsingEncoding:NSUTF8StringEncoding];
   NSRange range = [data rangeOfData:marker options:0 range:NSMakeRange(0, data.length)];
   if (range.location == NSNotFound) {
     callback(nil, data, done);
+  } else if (headers != nil) {
+    // If headers were parsed already just use that to avoid doing it twice.
+    NSInteger bodyStart = range.location + marker.length;
+    NSData *bodyData = [data subdataWithRange:NSMakeRange(bodyStart, data.length - bodyStart)];
+    callback(headers, bodyData, done);
   } else {
     NSData *headersData = [data subdataWithRange:NSMakeRange(0, range.location)];
     NSInteger bodyStart = range.location + marker.length;
@@ -56,14 +65,35 @@ - (void)emitChunk:(NSData *)data callback:(RCTMultipartCallback)callback done:(B
   }
 }
 
-- (BOOL)readAllParts:(RCTMultipartCallback)callback
+- (void)emitProgress:(NSDictionary *)headers
+       contentLength:(NSUInteger)contentLength
+               final:(BOOL)final
+            callback:(RCTMultipartProgressCallback)callback
+{
+  if (headers == nil) {
+    return;
+  }
+  // Throttle progress events so we don't send more that around 60 per second.
+  CFTimeInterval currentTime = CACurrentMediaTime();
+
+  NSUInteger headersContentLength = headers[@"Content-Length"] != nil ? [headers[@"Content-Length"] unsignedIntValue] : 0;
+  if (callback && (currentTime - _lastDownloadProgress > 0.016 || final)) {
+    _lastDownloadProgress = currentTime;
+    callback(headers, @(headersContentLength), @(contentLength));
+  }
+}
+
+- (BOOL)readAllPartsWithCompletionCallback:(RCTMultipartCallback)callback
+                          progressCallback:(RCTMultipartProgressCallback)progressCallback
 {
   NSInteger chunkStart = 0;
   NSInteger bytesSeen = 0;
 
   NSData *delimiter = [[NSString stringWithFormat:@"%@--%@%@", CRLF, _boundary, CRLF] dataUsingEncoding:NSUTF8StringEncoding];
   NSData *closeDelimiter = [[NSString stringWithFormat:@"%@--%@--%@", CRLF, _boundary, CRLF] dataUsingEncoding:NSUTF8StringEncoding];
   NSMutableData *content = [[NSMutableData alloc] initWithCapacity:1];
+  NSDictionary *currentHeaders = nil;
+  NSUInteger currentHeadersLength = 0;
 
   const NSUInteger bufferLen = 4 * 1024;
   uint8_t buffer[bufferLen];
@@ -75,13 +105,32 @@ - (BOOL)readAllParts:(RCTMultipartCallback)callback
     // to allow for the edge case when the delimiter is cut by read call
     NSInteger searchStart = MAX(bytesSeen - (NSInteger)closeDelimiter.length, chunkStart);
     NSRange remainingBufferRange = NSMakeRange(searchStart, content.length - searchStart);
+
+    // Check for delimiters.
     NSRange range = [content rangeOfData:delimiter options:0 range:remainingBufferRange];
     if (range.location == NSNotFound) {
       isCloseDelimiter = YES;
       range = [content rangeOfData:closeDelimiter options:0 range:remainingBufferRange];
     }
 
     if (range.location == NSNotFound) {
+      if (currentHeaders == nil) {
+        // Check for the headers delimiter.
+        NSData *headersMarker = [CRLF CRLF dataUsingEncoding:NSUTF8StringEncoding];
+        NSRange headersRange = [content rangeOfData:headersMarker options:0 range:remainingBufferRange];
+        if (headersRange.location != NSNotFound) {
+          NSData *headersData = [content subdataWithRange:NSMakeRange(chunkStart, headersRange.location - chunkStart)];
+          currentHeadersLength = headersData.length;
+          currentHeaders = [self parseHeaders:headersData];
+        }
+      } else {
+        // When headers are loaded start sending progress callbacks.
+        [self emitProgress:currentHeaders
+             contentLength:content.length - currentHeadersLength
+                     final:NO
+                  callback:progressCallback];
+      }
+
       bytesSeen = content.length;
       NSInteger bytesRead = [_stream read:buffer maxLength:bufferLen];
       if (bytesRead <= 0 || _stream.streamError) {
@@ -98,7 +147,13 @@ - (BOOL)readAllParts:(RCTMultipartCallback)callback
     // Ignore preamble
     if (chunkStart > 0) {
       NSData *chunk = [content subdataWithRange:NSMakeRange(chunkStart, length)];
-      [self emitChunk:chunk callback:callback done:isCloseDelimiter];
+      [self emitProgress:currentHeaders
+           contentLength:chunk.length - currentHeadersLength
+                   final:YES
+                callback:progressCallback];
+      [self emitChunk:chunk headers:currentHeaders callback:callback done:isCloseDelimiter];
+      currentHeaders = nil;
+      currentHeadersLength = 0;
     }
 
     if (isCloseDelimiter) {