+const char * get_default_encoding (void);
+void set_default_encoding (const char *enc);
+
+bool set_encoding_from_locale (const char *loc);
+
+const char *uc_name (ucs4_t uc, char buffer[16]);
+\f
+/* Information about character encodings. */
+
+/* ISO C defines a set of characters that a C implementation must support at
+ runtime, called the C basic execution character set, which consists of the
+ following characters:
+
+ A B C D E F G H I J K L M
+ N O P Q R S T U V W X Y Z
+ a b c d e f g h i j k l m
+ n o p q r s t u v w x y z
+ 0 1 2 3 4 5 6 7 8 9
+ ! " # % & ' ( ) * + , - . / :
+ ; < = > ? [ \ ] ^ _ { | } ~
+ space \a \b \r \n \t \v \f \0
+
+ The following is true of every member of the C basic execution character
+ set in all "reasonable" encodings:
+
+ 1. Every member of the C basic character set is encoded.
+
+ 2. Every member of the C basic character set has the same width in
+ bytes, called the "unit width". Most encodings have a unit width of
+ 1 byte, but UCS-2 and UTF-16 have a unit width of 2 bytes and UCS-4
+ and UTF-32 have a unit width of 4 bytes.
+
+ 3. In a stateful encoding, the encoding of members of the C basic
+ character set does not vary with shift state.
+
+ 4. When a string is read unit-by-unit, a unit that has the encoded value
+ of a member of the C basic character set, EXCEPT FOR THE DECIMAL
+ DIGITS, always represents that member. That is, if the encoding has
+ multi-unit characters, the units that encode the C basic character
+ set are never part of a multi-unit character.
+
+ The exception for decimal digits is due to GB18030, which uses
+ decimal digits as part of multi-byte encodings.
+
+ All 8-bit and wider encodings that I have been able to find follow these
+ rules. 7-bit and narrower encodings (e.g. UTF-7) do not. I'm not too
+ concerned about that. */
+
+#include <stdbool.h>
+
+/* Maximum width of a unit, in bytes. UTF-32 with 4-byte units is the widest
+ that I am aware of. */
+#define MAX_UNIT 4
+
+/* Information about an encoding. */
+struct encoding_info
+ {
+ /* Encoding name. IANA says character set names may be up to 40 US-ASCII
+ characters. */
+ char name[41];
+
+ /* True if this encoding has a unit width of 1 byte, and every character
+ used in ASCII text files has the same value in this encoding. */
+ bool is_ascii_compatible;
+
+ /* Character information. */
+ int unit; /* Unit width, in bytes. */
+ char cr[MAX_UNIT]; /* \r in encoding, 'unit' bytes long. */
+ char lf[MAX_UNIT]; /* \n in encoding, 'unit' bytes long. */
+ };
+
+bool get_encoding_info (struct encoding_info *, const char *name);
+bool is_encoding_ascii_compatible (const char *encoding);
+