InputStream Manual

Table of Contents

• About
• Usage
• Further Reading

About

An input stream is used to read data from a resource defined with a maxon::Url. maxon::InputStreamInterface is based on maxon::BaseStreamInterface.

Usage

maxon::InputStreamInterface provides these functions:

• maxon::InputStreamInterface::BytesAvailable(): Returns an estimate of the number of bytes that can be read.
• maxon::InputStreamInterface::Read(): Reads the given number of bytes into the given buffer.
• maxon::InputStreamInterface::ReadEOS(): Reads the given number of bytes into the given buffer or reads until the end of the stream.
• maxon::InputStreamInterface::Skip(): Skips over the given number of bytes.

  // This example reads a text file and loads the data into a maxon::String.
 
  // construct file URL
  const maxon::Url url = (targetFolder + maxon::Url("textfile.txt"_s))iferr_return;
 
  // check if file exists
  if (url.IoDetect() == maxon::IODETECT::FILE)
  {
    // open input stream and get file size
    const maxon::InputStreamRef inputStream = url.OpenInputStream() iferr_return;
    const maxon::Int length = inputStream.GetStreamLength() iferr_return;
 
    maxon::BaseArray<maxon::Char> data;
    data.Resize(length) iferr_return;
    inputStream.Read(data) iferr_return;
 
    // convert to string
    const maxon::String text { data };
    DiagnosticOutput("File Content: @", text);
  }

  // This example loads a file from the web and saves it to the local file system.
 
  // check if the given URL references a file on the web
  const maxon::UrlScheme scheme  = webFile.GetScheme();
  const maxon::Bool      isHTTP  = scheme == maxon::URLSCHEME_HTTP;
  const maxon::Bool      isHTTPS = scheme == maxon::URLSCHEME_HTTPS;
 
  if (isHTTP || isHTTPS)
  {
    // read data
 
    // input stream
    const maxon::InputStreamRef inputStream = webFile.OpenInputStream() iferr_return;
    const maxon::Int length = inputStream.GetStreamLength() iferr_return;
 
    maxon::BaseArray<maxon::Char> data;
    data.Resize(length) iferr_return;
 
    inputStream.Read(data) iferr_return;
    inputStream.Close() iferr_return;
 
    // save data to file
 
    // prepare file name
    const maxon::Url localFile = (targetFolder + webFile.GetName())iferr_return;
    // output stream
    const maxon::OutputStreamRef outputStream = localFile.OpenOutputStream() iferr_return;
    // write to file
    outputStream.Write(data) iferr_return;
    outputStream.Close() iferr_return;
  }

The input stream maxon::InputStreamInterface::FromBlock can be used to read data from a memory block.

  // This example shows how to access data from a memory block using an InputStreamRef.
 
  const auto memblock = maxon::CharToBlock("Hello World");
  const maxon::InputStreamRef inputStream = maxon::InputStreamInterface::FromBlock().Create(memblock, false) iferr_return;
 
  // read into a maxon::String
 
  // prepare memory
  const maxon::Int length = inputStream.GetStreamLength() iferr_return;
 
  maxon::BaseArray<maxon::Char> data;
  data.Resize(length) iferr_return;
  inputStream.Read(data) iferr_return;
 
  // convert to string
  const maxon::String text { data };
  DiagnosticOutput("Stream Content: @", text);

Further Reading

• Files & Media
• MAXON API Files & Media
• Url Manual
• OutputStream Manual