Here are the Lisp facilities for working with coding systems:
+@cindex list all coding systems
@defun coding-system-list &optional base-only
This function returns a list of all coding system names (symbols). If
@var{base-only} is non-@code{nil}, the value includes only the
name or @code{nil}.
@end defun
+@cindex validity of coding system
+@cindex coding system, validity check
@defun check-coding-system coding-system
This function checks the validity of @var{coding-system}. If that is
valid, it returns @var{coding-system}. If @var{coding-system} is
(@pxref{Signaling Errors, signal}).
@end defun
+@cindex eol type of coding system
@defun coding-system-eol-type coding-system
This function returns the type of end-of-line (a.k.a.@: @dfn{eol})
conversion used by @var{coding-system}. If @var{coding-system}
appropriate for the underlying platform.
@end defun
+@cindex eol conversion of coding system
@defun coding-system-change-eol-conversion coding-system eol-type
This function returns a coding system which is like @var{coding-system}
except for its eol conversion, which is specified by @code{eol-type}.
@code{dos} and @code{mac}, respectively.
@end defun
+@cindex text conversion of coding system
@defun coding-system-change-text-conversion eol-coding text-coding
This function returns a coding system which uses the end-of-line
conversion of @var{eol-coding}, and the text conversion of
@code{undecided}, or one of its variants according to @var{eol-coding}.
@end defun
+@cindex safely encode region
+@cindex coding systems for encoding region
@defun find-coding-systems-region from to
This function returns a list of coding systems that could be used to
encode a text between @var{from} and @var{to}. All coding systems in
list @code{(undecided)}.
@end defun
+@cindex safely encode a string
+@cindex coding systems for encoding a string
@defun find-coding-systems-string string
This function returns a list of coding systems that could be used to
encode the text of @var{string}. All coding systems in the list can
@code{(undecided)}.
@end defun
+@cindex charset, coding systems to encode
+@cindex safely encode characters in a charset
@defun 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 @var{charsets}.
operates on the contents of @var{string} instead of bytes in the buffer.
@end defun
+@cindex null bytes, and decoding text
@defvar inhibit-null-byte-detection
If this variable has a non-@code{nil} value, null bytes are ignored
when detecting the encoding of a region or a string. This allows to
because many files in the Emacs distribution use ISO-2022 encoding.}
@end defvar
+@cindex charsets supported by a coding system
@defun coding-system-charset-list coding-system
This function returns the list of character sets (@pxref{Character
Sets}) supported by @var{coding-system}. Some coding systems that
@node Default Coding Systems
@subsection Default Coding Systems
+@cindex default coding system
+@cindex coding system, automatically determined
This section describes variables that specify the default coding
system for certain files or when running certain subprograms, and the
@code{coding-system-for-read} and @code{coding-system-for-write}
(@pxref{Specifying Coding Systems}).
+@cindex file contents, and default coding system
@defvar auto-coding-regexp-alist
This variable is an alist of text patterns and corresponding coding
systems. Each element has the form @code{(@var{regexp}
reads them with no code conversions.
@end defvar
+@cindex file name, and default coding system
@defvar file-coding-system-alist
This variable is an alist that specifies the coding systems to use for
reading and writing particular files. Each element has the form
@code{undecided}, the normal code-detection is performed.
@end defvar
+@defvar auto-coding-alist
+This variable is an alist that specifies the coding systems to use for
+reading and writing particular files. Its form is like that of
+@code{file-coding-system-alist}, but, unlike the latter, this variable
+takes priority over any @code{coding:} tags in the file.
+@end defvar
+
+@cindex program name, and default coding system
@defvar process-coding-system-alist
This variable is an alist specifying which coding systems to use for a
subprocess, depending on which program is running in the subprocess. It
the end of line conversion---that is, one like @code{latin-1-unix},
rather than @code{undecided} or @code{latin-1}.
+@cindex port number, and default coding system
+@cindex network service name, and default coding system
@defvar network-coding-system-alist
This variable is an alist that specifies the coding system to use for
network streams. It works much like @code{file-coding-system-alist},
the subprocess, and @var{output-coding} applies to output to it.
@end defvar
+@cindex default coding system, functions to determine
@defvar auto-coding-functions
This variable holds a list of functions that try to determine a
coding system for a file based on its undecoded contents.
functions won't be called.
@end defvar
+@defun find-auto-coding filename size
+This function tries to determine a suitable coding system for
+@var{filename}. It examines the buffer visiting the named file, using
+the variables documented above in sequence, until it finds a match for
+one of the rules specified by these variables. It then returns a cons
+cell of the form @code{(@var{coding} . @var{source})}, where
+@var{coding} is the coding system to use and @var{source} is a symbol,
+one of @code{auto-coding-alist}, @code{auto-coding-regexp-alist},
+@code{:coding}, or @code{auto-coding-functions}, indicating which one
+supplied the matching rule. The value @code{:coding} means the coding
+system was specified by the @code{coding:} tag in the file
+(@pxref{Specify Coding,, coding tag, emacs, The GNU Emacs Manual}).
+The order of looking for a matching rule is @code{auto-coding-alist}
+first, then @code{auto-coding-regexp-alist}, then the @code{coding:}
+tag, and lastly @code{auto-coding-functions}. If no matching rule was
+found, the function returns @code{nil}.
+
+The second argument @var{size} is the size of text, in characters,
+following point. The function examines text only within @var{size}
+characters after point. Normally, the buffer should be positioned at
+the beginning when this function is called, because one of the places
+for the @code{coding:} tag is the first one or two lines of the file;
+in that case, @var{size} should be the size of the buffer.
+@end defun
+
+@defun set-auto-coding filename size
+This function returns a suitable coding system for file
+@var{filename}. It uses @code{find-auto-coding} to find the coding
+system. If no coding system could be determined, the function returns
+@code{nil}. The meaning of the argument @var{size} is like in
+@code{find-auto-coding}.
+@end defun
+
@defun find-operation-coding-system operation &rest arguments
This function returns the coding system to use (by default) for
performing @var{operation} with @var{arguments}. The value has this