Convert Binary File Data To ArrayBuffer Sent From Python As Byte-Array String

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05-10-2024

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Converting Binary File Data to ArrayBuffer: Sending from Python as Byte-Array String

Problem: You have a binary file in Python and need to send its data to a JavaScript application as an ArrayBuffer. The challenge lies in efficiently transmitting the binary data across the network and converting it to a format that JavaScript can readily use.

Solution: This article explores a robust solution using Python's bytes type to represent the binary data and JavaScript's ArrayBuffer to handle it on the client-side.

Scenario:

Let's imagine you have a Python application that generates a binary file (e.g., an image). You want to send this file to a web browser to display it.

Python Code:

import base64

def send_binary_data(file_path):
  with open(file_path, "rb") as f:
    data = f.read()
    # Convert to base64 for safe transmission
    base64_data = base64.b64encode(data).decode("utf-8")
    return base64_data

# Example usage
file_path = "image.png"
base64_data = send_binary_data(file_path)

# Send base64_data to the JavaScript client 

JavaScript Code:

function displayImage(base64Data) {
  const arrayBuffer = base64ToArrayBuffer(base64Data);
  const blob = new Blob([arrayBuffer], { type: 'image/png' });
  const imageURL = URL.createObjectURL(blob);
  const img = document.createElement('img');
  img.src = imageURL;
  document.body.appendChild(img);
}

function base64ToArrayBuffer(base64) {
  const binaryString = atob(base64);
  const len = binaryString.length;
  const bytes = new Uint8Array(len);
  for (let i = 0; i < len; i++) {
    bytes[i] = binaryString.charCodeAt(i);
  }
  return bytes.buffer;
}

// Receive base64_data from Python and display image
displayImage(base64_data);

Analysis:

1. Encoding and Transmission: In Python, the bytes type is used to represent the binary data. Before sending it over the network, it's encoded using base64.b64encode to ensure safe transmission as a string.
2. Decoding and Conversion: On the JavaScript side, the received base64_data is first decoded using atob to obtain the raw binary string. Then, the string is converted into an ArrayBuffer by creating a Uint8Array and using its buffer property.
3. Displaying the Image: The ArrayBuffer is then used to construct a Blob object, which is then converted to a URL using URL.createObjectURL. This URL is set as the src attribute of an img element to display the image in the browser.

Benefits:

• Efficiency: Using base64 encoding allows for a compact and efficient representation of the binary data, reducing the size of the transmitted data.
• Compatibility: ArrayBuffer is a standard JavaScript API, ensuring compatibility across modern browsers.
• Data Integrity: base64 encoding preserves the original binary data without any loss.

Additional Value:

• You can adapt this approach to send any type of binary file, not just images.
• By using fetch API or other network protocols, you can streamline the data transmission process.
• For larger files, consider using chunking to avoid performance issues.

References:

• Base64 Encoding
• ArrayBuffer
• Blob

Conclusion:

This method provides a reliable and efficient way to send binary file data from Python to a JavaScript application using ArrayBuffer. By understanding the process and leveraging the tools provided by both languages, you can seamlessly transfer and handle binary data for various applications.