Here are the Lisp facilities for working with coding systems:
function coding-system-list \&optional base-only
This function returns a list of all coding system names (symbols). If
base-only is non-
nil, the value includes only the base coding systems. Otherwise, it includes alias and variant coding systems as well.
function coding-system-p object
This function returns
object is a coding system name or
function check-coding-system coding-system
This function checks the validity of
coding-system. If that is valid, it returns
nil, the function return
nil. For any other values, it signals an error whose
coding-system-error (see signal).
function coding-system-eol-type coding-system
This function returns the type of end-of-line (a.k.a. eol) conversion used by
coding-system specifies a certain eol conversion, the return value is an integer 0, 1, or 2, standing for
mac, respectively. If
coding-system doesn’t specify eol conversion explicitly, the return value is a vector of coding systems, each one with one of the possible eol conversion types, like this:
⇒ [latin-1-unix latin-1-dos latin-1-mac]
If this function returns a vector, Emacs will decide, as part of the text encoding or decoding process, what eol conversion to use. For decoding, the end-of-line format of the text is auto-detected, and the eol conversion is set to match it (e.g., DOS-style CRLF format will imply
dos eol conversion). For encoding, the eol conversion is taken from the appropriate default coding system (e.g., default value of
buffer-file-coding-system), or from the default eol conversion appropriate for the underlying platform.
function coding-system-change-eol-conversion coding-system eol-type
This function returns a coding system which is like
coding-system except for its eol conversion, which is specified by
eol-type should be
nil. If it is
nil, the returned coding system determines the end-of-line conversion from the data.
eol-type may also be 0, 1 or 2, standing for
function coding-system-change-text-conversion eol-coding text-coding
This function returns a coding system which uses the end-of-line conversion of
eol-coding, and the text conversion of
nil, it returns
undecided, or one of its variants according to
function find-coding-systems-region from to
This function returns a list of coding systems that could be used to encode a text between
to. All coding systems in the list can safely encode any multibyte characters in that portion of the text.
If the text contains no multibyte characters, the function returns the list
function find-coding-systems-string string
This function returns a list of coding systems that could be used to encode the text of
string. All coding systems in the list can safely encode any multibyte characters in
string. If the text contains no multibyte characters, this returns the list
function find-coding-systems-for-charsets charsets
This function returns a list of coding systems that could be used to encode all the character sets in the list
function check-coding-systems-region start end coding-system-list
This function checks whether coding systems in the list
coding-system-list can encode all the characters in the region between
end. If all of the coding systems in the list can encode the specified text, the function returns
nil. If some coding systems cannot encode some of the characters, the value is an alist, each element of which has the form
(coding-system1 pos1 pos2 …), meaning that
coding-system1 cannot encode characters at buffer positions
start may be a string, in which case
end is ignored and the returned value references string indices instead of buffer positions.
function detect-coding-region start end \&optional highest
This function chooses a plausible coding system for decoding the text from
end. This text should be a byte sequence, i.e., unibyte text or multibyte text with only ASCII and eight-bit characters (see Explicit Encoding).
Normally this function returns a list of coding systems that could handle decoding the text that was scanned. They are listed in order of decreasing priority. But if
highest is non-
nil, then the return value is just one coding system, the one that is highest in priority.
If the region contains only ASCII characters except for such ISO-2022 control characters ISO-2022 as
ESC, the value is
(undecided), or a variant specifying end-of-line conversion, if that can be deduced from the text.
If the region contains null bytes, the value is
no-conversion, even if the region contains text encoded in some coding system.
function detect-coding-string string \&optional highest
This function is like
detect-coding-region except that it operates on the contents of
string instead of bytes in the buffer.
If this variable has a non-
nil value, null bytes are ignored when detecting the encoding of a region or a string. This allows the encoding of text that contains null bytes to be correctly detected, such as Info files with Index nodes.
If this variable has a non-
nil value, ISO-2022 escape sequences are ignored when detecting the encoding of a region or a string. The result is that no text is ever detected as encoded in some ISO-2022 encoding, and all escape sequences become visible in a buffer. Warning: Use this variable with extreme caution, because many files in the Emacs distribution use ISO-2022 encoding.
function coding-system-charset-list coding-system
This function returns the list of character sets (see Character Sets) supported by
coding-system. Some coding systems that support too many character sets to list them all yield special values:
coding-systemsupports all Emacs characters, the value is
coding-systemsupports all Unicode characters, the value is
coding-systemsupports all ISO-2022 charsets, the value is
coding-systemsupports all the characters in the internal coding system used by Emacs version 21 (prior to the implementation of internal Unicode support), the value is
See Process Information, in particular the description of the functions
set-process-coding-system, for how to examine or set the coding systems used for I/O to a subprocess.