Read binary from a string instead of using fread

I have a binary file of data, where the binary data is split up periodically by a keyword to indicate segments. I've read in that entire string and split it up around the keywords so that I have each segment individually. I have then joined all these segments into one larger binary string. Is there a way I can read this binary string as if I was using fread on a binary file?

I know in theory I can write the entire string to a new file, and then read that, but is there a more efficient way?

Beautiful paint diagram trying to illustrate my point.

Answer 1

[MYBLOG]

Yes, you can achieve this without writing the entire string to a new file. Instead, you can use the memmapfile function in MATLAB to create a memory-mapped file object that allows you to treat a portion of memory as a binary file. This can be an efficient way to read the concatenated binary data as if you were using fread on a binary file.

Here's how you can do it:

1. Convert your concatenated binary string into a uint8 array.
2. Create a memory-mapped file object using memmapfile and specify the Format as 'uint8'.
3. Use the memory-mapped file object to read the data as if it were a binary file.

Here's an example:

% Sample concatenated binary string (replace this with your actual data)
concatenated_binary_string = '...'; % Your concatenated binary string here

% Convert binary string to uint8 array
binary_data = uint8(concatenated_binary_string);

% Define the size of each segment and the total number of segments
segment_size = 1000; % Example segment size
total_segments = numel(binary_data) / segment_size;

% Create a memory-mapped file object
mmf = memmapfile('temp.dat', 'Writable', true, 'Format', 'uint8');

% Write the binary data to the memory-mapped file
mmf.Data = binary_data;

% Read a segment from the memory-mapped file
segment_number = 1; % Example segment number
start_index = (segment_number - 1) * segment_size + 1;
end_index = start_index + segment_size - 1;
segment = mmf.Data(start_index:end_index);

% Use the segment as needed
disp(segment);

% Clean up: Close the memory-mapped file
clear mmf;

Keep in mind that memory-mapped files provide a way to access large data sets without loading the entire data into memory at once, which can be more memory-efficient. However, they do involve reading data from disk as needed, so their performance can depend on factors such as disk speed and the size of the segments you are reading.