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6.6.5.13 Representing Strings as Bytes

   Out in the cold world outside of Guile, not all strings are treated in the same
   way. Out there there are only bytes, and there are many ways of representing a
   strings (sequences of characters) as binary data (sequences of bytes).

   As a user, usually you don't have to think about this very much. When you type on
   your keyboard, your system encodes your keystrokes as bytes according to the
   locale that you have configured on your computer. Guile uses the locale to decode
   those bytes back into characters - hopefully the same characters that you typed
   in.

   All is not so clear when dealing with a system with multiple users, such as a web
   server. Your web server might get a request from one user for data encoded in the
   ISO-8859-1 character set, and then another request from a different user for
   UTF-8 data.

   Guile provides an iconv module for converting between strings and sequences of
   bytes. See [12]Bytevectors, for more on how Guile represents raw byte sequences.
   This module gets its name from the common UNIX command of the same name.

   Note that often it is sufficient to just read and write strings from ports
   instead of using these functions. To do this, specify the port encoding using
   set-port-encoding!. See [13]Ports, for more on ports and character encodings.

   Unlike the rest of the procedures in this section, you have to load the iconv
   module before having access to these procedures:
(use-modules (ice-9 iconv))

   Scheme Procedure: string->bytevector string encoding [conversion-strategy][14] ¶
          Encode string as a sequence of bytes.

          The string will be encoded in the character set specified by the encoding
          string. If the string has characters that cannot be represented in the
          encoding, by default this procedure raises an encoding-error. Pass a
          conversion-strategy argument to specify other behaviors.

          The return value is a bytevector. See [15]Bytevectors, for more on
          bytevectors. See [16]Ports, for more on character encodings and conversion
          strategies.

   Scheme Procedure: bytevector->string bytevector encoding
          [conversion-strategy][17] ¶
          Decode bytevector into a string.

          The bytes will be decoded from the character set by the encoding string.
          If the bytes do not form a valid encoding, by default this procedure
          raises an decoding-error. As with string->bytevector, pass the optional
          conversion-strategy argument to modify this behavior. See [18]Ports, for
          more on character encodings and conversion strategies.

   Scheme Procedure: call-with-output-encoded-string encoding proc
          [conversion-strategy][19] ¶
          Like call-with-output-string, but instead of returning a string, returns a
          encoding of the string according to encoding, as a bytevector. This
          procedure can be more efficient than collecting a string and then
          converting it via string->bytevector.
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References

   1. http://www.gnu.org/software/guile/manual/html_node/index.html
   2. http://www.gnu.org/software/guile/manual/html_node/Concept-Index.html
   3. http://www.gnu.org/software/guile/manual/html_node/index.html#SEC_Contents
   4. http://www.gnu.org/software/guile/manual/html_node/Strings.html
   5. http://www.gnu.org/software/guile/manual/html_node/Conversion-to_002ffrom-C.html
   6. http://www.gnu.org/software/guile/manual/html_node/Miscellaneous-String-Operations.html
   7. http://www.gnu.org/software/guile/manual/html_node/Conversion-to_002ffrom-C.html
   8. http://www.gnu.org/software/guile/manual/html_node/Miscellaneous-String-Operations.html
   9. http://www.gnu.org/software/guile/manual/html_node/Strings.html
  10. http://www.gnu.org/software/guile/manual/html_node/index.html#SEC_Contents
  11. http://www.gnu.org/software/guile/manual/html_node/Concept-Index.html
  12. http://www.gnu.org/software/guile/manual/html_node/Bytevectors.html
  13. http://www.gnu.org/software/guile/manual/html_node/Ports.html
  14. http://www.gnu.org/software/guile/manual/html_node/Representing-Strings-as-Bytes.html#index-string_002d_003ebytevector
  15. http://www.gnu.org/software/guile/manual/html_node/Bytevectors.html
  16. http://www.gnu.org/software/guile/manual/html_node/Ports.html
  17. http://www.gnu.org/software/guile/manual/html_node/Representing-Strings-as-Bytes.html#index-bytevector_002d_003estring
  18. http://www.gnu.org/software/guile/manual/html_node/Ports.html
  19. http://www.gnu.org/software/guile/manual/html_node/Representing-Strings-as-Bytes.html#index-call_002dwith_002doutput_002dencoded_002dstring
  20. http://www.gnu.org/software/guile/manual/html_node/Conversion-to_002ffrom-C.html
  21. http://www.gnu.org/software/guile/manual/html_node/Miscellaneous-String-Operations.html
  22. http://www.gnu.org/software/guile/manual/html_node/Strings.html
  23. http://www.gnu.org/software/guile/manual/html_node/index.html#SEC_Contents
  24. http://www.gnu.org/software/guile/manual/html_node/Concept-Index.html