I'm working in Xcode 4.3.2 + building for an app in iOS 5.
I've decided to use SBJson to parse streams of data from our server. I've verified that I'm receiving a valid JSON response from the server. My question concerns the design behind the classes SBJsonStreamParser and the SBJsonParser.
It appears that in SBJsonParser the method "objectWithData" takes the data received from the JSON response and uses the SBJsonStreamParserAccumulator to append the stream of data into a single JSON document. Once the data stream is gathered into one object, it is then parsed by the "parse" method in SBJsonStreamParser.
I've run into several issues when requesting larger JSON documents. The size of the responses seem to be reasonable (specially 9.4 KB response). It appears that the SBJsonStreamParser breaks when getting a data stream greater than a certain size. The parser succeeds when the response is small (~3KB), but fails when the response is larger (~10KB).
I used NSLog to verify that in both cases, pulling a small & large stream, the methods are successfully receiving the full json document - because it looks like [{"id": .... 123}]. I'm convinced that the issue is that the data stream is too long.
I'm wondering if I'm using SBJson incorrectly or is this simply a limitation of the parser? Is there anything that I can configure that allows SBJsonStreamParser to not throw an error for larger (but reasonable) data streams & continue to parse the full response?
Thanks in advance!
Actually you have the workings of objectWithData: backwards. SBJsonStreamParserAccumulator is used to accumulate the parsed output, not the unparsed data stream.
Related
I'm trying to implement the file storage ыукмшсу with basic S3 compatible API using akka-http.
I use s3 java sdk to test my service API and got the problem with the putObject(...) method. I can't consume file properly on my akka-http backend. I wrote simple route for the test purposes:
def putFile(bucket: String, file: String) = put{
extractRequestEntity{ ent =>
val finishedWriting = ent.dataBytes.runWith(FileIO.toPath(new File(s"/tmp/${file}").toPath))
onComplete(finishedWriting) { ioResult =>
complete("Finished writing data: " + ioResult)
}
}
}
It saves file, but file is always corrupted. Looking inside the file I found the lines like these:
"20000;chunk-signature=73c6b865ab5899b5b7596b8c11113a8df439489da42ddb5b8d0c861a0472f8a1".
When I try to PUT file with any other rest client it works as fine as expected.
I know S3 uses "Expect: 100-continue" header and may it he causes problems.
I really can't figure out how to deal with that. Any help appreciated.
This isn't exactly corrupted. Your service is not accounting for one of the four¹ ways S3 supports uploads to be sent on the wire, using Content-Encoding: aws-chunked and x-amz-content-sha256: STREAMING-AWS4-HMAC-SHA256-PAYLOAD.
It's a non-standards-based mechanism for streaming an object, and includes chunks that look exactly like this:
string(IntHexBase(chunk-size)) + ";chunk-signature=" + signature + \r\n + chunk-data + \r\n
...where IntHexBase() is pseudocode for a function that formats an integer as a hexadecimal number as a string.
This chunk-based algorithm is similar to, but not compatible with, Transfer-Encoding: chunked, because it embeds checksums in the stream.
Why did they make up a new HTTP transfer encoding? It's potentially useful on the client side because it eliminates the need to either "read your payload twice or buffer [the entire object payload] in memory [concurrently]" -- one or the other of which is otherwise necessary if you are going to calculate the x-amz-content-sha256 hash before the upload begins, as you otherwise must, since it's required for integrity checking.
I am not overly familiar with the internals of the Java SDK, but this type of upload might be triggered by using .withInputStream() or it might be standard behavor for files too, or for files over a certain size.
Your minimum workaround would be to throw an HTTP error if you see x-amz-content-sha256: STREAMING-AWS4-HMAC-SHA256-PAYLOAD in the request headers since you appear not to have implemented this in your API, but this would most likely only serve to prevent storing objects uploaded by this method. The fact that this isn't already what happens automatically suggests that you haven't implemented x-amz-content-sha256 handling at all, so you are not doing the server-side payload integrity checks that you need to be doing.
For full compatibility, you'll need to implement the algorithm supported by S3 and assumed to be available by the SDKs, unless the SDKs specifically support a mechanism for disabling this algorithm -- which seems unlikely, since it serves a useful purpose, particularly (it appears) for streams whose length is known but that aren't seekable.
¹ one of four -- the other three are a standard PUT, a web-based html form POST, and the multipart API that is recommended for large files and mandatory for files larger than 5 GB.
I have been writing iPhone applications for some time now, sending data to server, receiving data (via HTTP protocol), without thinking too much about it. Mostly I am theoretically familiar with process, but the part I am not so familiar is HTTP multipart request. I know its basic structure, but the core of it eludes me.
It seems that whenever I am sending something different than plain text (like photos, music), I have to use a multipart request. Can someone briefly explain to me why it is used and what are its advantages?
If I use it, why is it better way to send photos that way?
An HTTP multipart request is an HTTP request that HTTP clients construct to send files and data over to an HTTP Server. It is commonly used by browsers and HTTP clients to upload files to the server.
What it looks like
See Multipart Content-Type
See multipart/form-data
As the official specification says, "one or more different sets of data are combined in a single body". So when photos and music are handled as multipart messages as mentioned in the question, probably there is some plain text metadata associated as well, thus making the request containing different types of data (binary, text), which implies the usage of multipart.
I have found an excellent and relatively short explanation here.
A multipart request is a REST request containing several packed REST requests inside its entity.
I have a requirement where user can upload files present in app to SharePoint via same app.
I tried using http://schemas.microsoft.com/sharepoint/soap/CopyIntoItems method of sharepoint. But it needs file in base64 encoded format to be embedded into body of SOAP request . My code crashed on device when I tried to convert even a 30 MB file in base64 encoded string? Same code executed just fine on simulator
Is there any other alternative to upload files (like file streaming etc) onto sharepoint?? I may have to upload files upto 500 MB? Is there more efficient library to convert NSData into base64 encoded string for large file???
Should I read file in chunks and then convert that into base64 encoded string and upload file once complete file is converted? Any other appraoches???
First off, your code probably crashed because it ran out of memory. I would do a loop where I read chunks that I converted and then pushed to a open socket. This probably means that you need to go to a lower level than NSURLConnection, I have tried to search for NSURLConnection and chunked upload without much success.
Some seem to suggest using ASIHttp, but looking at the homepage it seems abandoned by the developer, so I can't recommend that.
AFNetworking looks really good, it has blocks support and I can see in the example on the first page how it could be used for you. Look at the streaming request example. Basically create a NSInputStream that you push chunked data to and use it in a AFHTTPURLConnectionOperation.
I consuming Web-Services that streams a pdf file to my iOS device. I used SOAP message to interact with web-services and using NSXMLParser:foundCharacters() after the stream is complete and I want to get the content of pdf file from my streamed xml file which was created in first step. The data I get is encoded in base64 and I have the methods to decode the content back.For small file the easiest approach is reading/collect all content with NSXMLParser:foundCharacters from first streamed file and call the decoding base64 method when I get whole data from parse:didEndElement
(the above approach works fine I tested for this case and I made the right pdf file out of it).
Now my question is what is the best approach(optimizing memory/speed) to read/decode/write to make the final pdf from a big streamed files.
Is there any code available or any thought to accomplish this in objective-C
I'm successfully using yajl-objc along with ASIHTTPRequest in an iPhone project that does network access and pulls down and parses JSON data. ASIHTTPRequest allows gzipped HTTP responses by default, which is great, but I'm using the streaming parser ability of YAJL and it rightfully chokes on gzipped data. I can wait until the HTTP request has finished then un-gzip and parse the response, but I'm going for speed here and would like to parse the gzipped data as it downloads.
Is it possible to un-gzip data on the fly, parse the JSON within, then forget about that chunk of gzipped data?
If this last part could be solved, this setup seems like it would make for a great system:
YAJL is one of the fastest JSON parsers around
ASIHTTPRequest is easy and asynchronous
Response bodies could be gzipped, saving on-the-wire traffic
JSON could be parsed without loading the whole tree into constrained device memory
Any guidance would be greatly appreciated!
YES: http://groups.google.com/group/asihttprequest/browse_thread/thread/ee2e44379b181439/7699dd200780cd32#7699dd200780cd32