Info Catalog elisp: Converting Representations elisp: Non-ASCII Characters elisp: Character Codes

elisp: Selecting a Representation

 
 32.4 Selecting a Representation
 ===============================
 
 Sometimes it is useful to examine an existing buffer or string as
 multibyte when it was unibyte, or vice versa.
 
  -- Function: set-buffer-multibyte multibyte
      Set the representation type of the current buffer.  If MULTIBYTE is
      non-‘nil’, the buffer becomes multibyte.  If MULTIBYTE is ‘nil’,
      the buffer becomes unibyte.
 
      This function leaves the buffer contents unchanged when viewed as a
      sequence of bytes.  As a consequence, it can change the contents
      viewed as characters; for instance, a sequence of three bytes which
      is treated as one character in multibyte representation will count
      as three characters in unibyte representation.  Eight-bit
      characters representing raw bytes are an exception.  They are
      represented by one byte in a unibyte buffer, but when the buffer is
      set to multibyte, they are converted to two-byte sequences, and
      vice versa.
 
      This function sets ‘enable-multibyte-characters’ to record which
      representation is in use.  It also adjusts various data in the
      buffer (including overlays, text properties and markers) so that
      they cover the same text as they did before.
 
      This function signals an error if the buffer is narrowed, since the
      narrowing might have occurred in the middle of multibyte character
      sequences.
 
      This function also signals an error if the buffer is an indirect
      buffer.  An indirect buffer always inherits the representation of
      its base buffer.
 
  -- Function: string-as-unibyte string
      If STRING is already a unibyte string, this function returns STRING
      itself.  Otherwise, it returns a new string with the same bytes as
      STRING, but treating each byte as a separate character (so that the
      value may have more characters than STRING); as an exception, each
      eight-bit character representing a raw byte is converted into a
      single byte.  The newly-created string contains no text properties.
 
  -- Function: string-as-multibyte string
      If STRING is a multibyte string, this function returns STRING
      itself.  Otherwise, it returns a new string with the same bytes as
      STRING, but treating each multibyte sequence as one character.
      This means that the value may have fewer characters than STRING
      has.  If a byte sequence in STRING is invalid as a multibyte
      representation of a single character, each byte in the sequence is
      treated as a raw 8-bit byte.  The newly-created string contains no
      text properties.
 

Info Catalog elisp: Converting Representations elisp: Non-ASCII Characters elisp: Character Codes