This interface defines operations on strings of 8-bit CHARs. They are represented by address of the first character of the string and the string's length in characters.

INTERFACE String8;

PROCEDURE Equal (a, b: ADDRESS;  len: CARDINAL): BOOLEAN;

Return TRUE if the strings of len characters starting at a and b have the same (case-sensitive) contents.

PROCEDURE Compare (a: ADDRESS;  len_a: CARDINAL;
                   b: ADDRESS;  len_b: CARDINAL): [-1..1];

Return -1 if string a occurs before string b, 0 if the strings are equal, and +1 if a occurs after b in lexicographic order.

PROCEDURE Hash (a: ADDRESS;  len: CARDINAL;  initial: INTEGER): INTEGER;

Return a hash function of the contents of string a starting with the value initial.

PROCEDURE FindChar (a: ADDRESS;  len: CARDINAL;  c: CHAR): INTEGER;

If c = a[i] for some i in [0~..~len-1], return the smallest such i; otherwise, return -1.

PROCEDURE FindCharR (a: ADDRESS;  len: CARDINAL;  c: CHAR): INTEGER;

If c = a[i] for some i in [0~..~len-1], return the largest such i; otherwise, return -1.

PROCEDURE ArrayStart (READONLY a: ARRAY OF CHAR): ADDRESS;

Returns the address of the first character of a if it is non-empty, otherwise returns NIL. WARNING: the returned address is only valid as long as a does not move. To prevent heap allocated arrays from moving, keep the returned address on the stack.

END String8.