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Decoding Binary Messages

Problem

You have a string containing the characters 0 and 1, representing, in binary, the ASCII values of some text. You want to convert this string into normal, readable, ASCII.

Solution

The solution has four steps:

1. Chop the string into its component parts. ASCII values are 8 bits long, so we chop the string into sub-strings that are 8 characters long
2. Convert each substring into the number it represents
3. Convert each number into the ASCII character it represents
4. Combine all the ASCII characters into a single string

500 Can't connect to 127.0.0.1:8778 (connect: Connection refused)

Discussion

RnRS defines procedures string->number and number->string to convert between a string containing the external (i.e. printed) representation of a number and number itself. For example:

500 Can't connect to 127.0.0.1:8778 (connect: Connection refused)

Both procedures take an optional second argument, which specifies the radix ("base") to use. The default is 10, but values of 2, 8, 10 or 16 may also be used. In the recipe above the radix 2 specifies that we are converting to numbers from a base 2 representation. If, for example, the numbers were represented in base 16 (hexadecimal) it would be a simple matter to replace binary-string->integer with the procedure:

500 Can't connect to 127.0.0.1:8778 (connect: Connection refused)

Contributors

-- GordonWeakliem - 06 Apr 2004

-- NoelWelsh - 14 Apr 2004

I made some fairly major changes. Hope you like. -- NoelWelsh - 14 Apr