elisp: Format Conversion Overview

 
 24.12.1 Overview
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 The function ‘insert-file-contents’:
 
    • initially, inserts bytes from the file into the buffer;
    • decodes bytes to characters as appropriate;
    • processes formats as defined by entries in ‘format-alist’; and
    • calls functions in ‘after-insert-file-functions’.
 
 The function ‘write-region’:
 
    • initially, calls functions in ‘write-region-annotate-functions’;
    • processes formats as defined by entries in ‘format-alist’;
    • encodes characters to bytes as appropriate; and
    • modifies the file with the bytes.
 
    This shows the symmetry of the lowest-level operations; reading and
 writing handle things in opposite order.  The rest of this section
 describes the two facilities surrounding the three variables named
 above, as well as some related functions.  SeeCoding Systems, for
 details on character encoding and decoding.