Read a file into a byte array

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Revision as of 22:35, 16 December 2006 by 71.197.105.227 (Talk)

Implementations

Common Lisp

The following does not work with multibyte streams. The common lisp stream must be single-byte for this particular function.

; here's the function
(defun slurp-stream4 (stream)
  (let ((seq (make-string (file-length stream))))
    (read-sequence seq stream)
    seq))

;open up a stream:
(setq stream (open "filename.txt"))

;call the function and set the results variable equal to the string returned.
(setq results (slurp-stream4 stream))

;close the stream.
(close stream)

This is from [1].

Java

This method reads the entire content of a file into a byte array.

    // Returns the contents of the file in a byte array.
    public static byte[] getBytesFromFile(File file) throws IOException {
        InputStream is = new FileInputStream(file);
    
        // Get the size of the file
        long length = file.length();
    
        // You cannot create an array using a long type.
        // It needs to be an int type.
        // Before converting to an int type, check
        // to ensure that file is not larger than Integer.MAX_VALUE.
        if (length > Integer.MAX_VALUE) {
            // File is too large
        }
    
        // Create the byte array to hold the data
        byte[] bytes = new byte[(int)length];
    
        // Read in the bytes
        int offset = 0;
        int numRead = 0;
        while (offset < bytes.length
               && (numRead=is.read(bytes, offset, bytes.length-offset)) >= 0) {
            offset += numRead;
        }
    
        // Ensure all the bytes have been read in
        if (offset < bytes.length) {
            throw new IOException("Could not completely read file "+file.getName());
        }
    
        // Close the input stream and return bytes
        is.close();
        return bytes;
    }

OCaml

# let get_bytes_from_file filename =
    let ch = open_in filename in
    let buf = Buffer.create 1024 in
    (try Buffer.add_channel buf ch max_int with _ -> ());
    close_in ch;
    buf;;
val get_bytes_from_file : string -> Buffer.t = <fun>