MTBase64InputStream

v0.0.1

1. Description

MTBase64InputStream is a subclass of NSInputStream which encodes files to base64 format on the fly, removing the need to store large files in memory just to do that.

2. Purpose

Apple provides no built-in way to handle encoding and decoding large files to base64 format. While it provides a nice interface to handle encoding and decoding, it requires clients to load the file into memory to do that and if the client needs to do such operations on a large file, there is no way to track progress or prevent application from crashing under memory pressure. MTBase64InputStream's goal is to provide such api while conforming to NSStream lifecycle

3. Usage

Since MTBase64InputStream inherits from NSInputStream, it should be used as one. When creating buffers, please keep in mind that after encoding a file to base64 format, the output file will take a larger amount of space, therefore input buffer needs to be sufficiently larger that the maximum length when using read:maxLength: method. getBuffer:length: method will handle creating a proper buffer for you. The most simple usage in order to encode a file present at a given url would be:

  NSInteger length, bufferSize //Assume these exist
  NSInputStream *inputStream = [[MTBase64InputStream alloc] initWithURL:aURL];
  [inputStream open];
  uint8_t *buffer = malloc(bufferSize * sizeof(uint8_t));
  while ([inputStream hasBytesAvailable]) {
    NSInteger bytesRead = [inputStream read:buffer maxLength:length];
    //Do something with the data
  }
  [inputStream close];

Please refer to the unit tests for more examples.

4. License

MTBase64InputStream is under Apache 2 license, therefore you are free to use it in commercial or non-commercial projects. See the LICENSE file for details

5. TODO

• Add cocoapods support

• Write tests verifying NSStream lifecycle