@code{insert-file-contents}, @code{write-region},
@code{start-process}, @code{call-process}, @code{call-process-region},
or @code{open-network-stream}. These are the names of the Emacs I/O
-primitives that can do coding system conversion.
+primitives that can do character code and eol conversion.
The remaining arguments should be the same arguments that might be given
-to that I/O primitive. Depending on the primitive, one of those
-arguments is selected as the @dfn{target}. For example, if
+to the corresponding I/O primitive. Depending on the primitive, one
+of those arguments is selected as the @dfn{target}. For example, if
@var{operation} does file I/O, whichever argument specifies the file
name is the target. For subprocess primitives, the process name is the
target. For @code{open-network-stream}, the target is the service name
Depending on @var{operation}, this function looks up the target in
@code{file-coding-system-alist}, @code{process-coding-system-alist},
-or @code{network-coding-system-alist}.
+or @code{network-coding-system-alist}. If the target is found in the
+alist, @code{find-operation-coding-system} returns its association in
+the alist; otherwise it returns @code{nil}.
If @var{operation} is @code{insert-file-contents}, the argument
corresponding to the target may be a cons cell of the form
@code{(@var{filename} . @var{buffer})}). In that case, @var{filename}
-is a file name to look up, and @var{buffer} is a buffer that already
-contains the file's contents (not yet decoded). Functions specified
-in @code{file-coding-system-alist} must pay attention to this format
-of the target.
+is a file name to look up in @code{file-coding-system-alist}, and
+@var{buffer} is a buffer will contain the file's contents (not yet
+decoded). If the file's association in
+@code{file-coding-system-alist} specifies a function to call, and that
+function needs to examine the file's contents (as it usually does), it
+should examine the contents of @var{buffer} instead of reading the
+file.
@end defun
@node Specifying Coding Systems