; string.h -- Standard interface definitons for the Hawk string library.
; language:   SMAL32 assembly language, intended as an include file
; author:     Douglas W. Jones
; date:       Dec 1, 2019

;   Linkage conventions:
;     R1 -- used for return address linkage by all support routines.
;     R2 -- available for use as an activation record pointer.
;     R3 -- typically the first parameter and function return value
;     R4 -- typically the second parameter, if there is one.

;-------------------------------
; length

	EXT	STRLEN	; count the characters in a string
		 	;   takes R3=pointer to the string
		 	;   returns R3=length of the string, without NUL
                        ; C equivalent: length = strlen(string)

;-------------------------------
; copy and concatenate

	EXT	STRCPY	; copy a string with no length limit
	EXT	STRNCPY	; copy a string with a set length limit
			;   takes R3=pointer to destination string buffer
			;         R4=pointer to source
			;         R5=length limit (STRNCPY only)
		 	;   returns R3=unchanged
			;   wipes out R4-R7
                        ; C equivalent: dst = strcpy(dst,src)
			;               dst = strcpy(dst,src,limit)

	EXT	STRCAT	; concatenate a string to another with no limit
	EXT	STRNCAT	; concatenate a string with a set length limit
			;   takes R3=pointer to destination string
			;         R4=pointer to source
			;         R5=length limit (STRNCAT only)
		 	;   returns R3=unchanged
			;   wipes out R4-R7
                        ; C equivalent: dst = strcat(dst,src)
			;               dst = strcat(dst,src,limit)

;-------------------------------
; compare

	EXT	STRCMP	; compare two strings
			;   takes R3=pointer to string s1
			;         R4=pointer to string s2
		 	;   returns R3 < 0 if s1<s2
		 	;              = 0 if s1=s2
		 	;              > 0 if s1>s2
			;   wipes out R4-R6
			;         R5=length limit (STRNCAT only)
                        ; C equivalent: result = strcmp(s1,s2)