Add strings.ncompare (and backing strncmp_mem) to compare up to n characters of a string. (#164)

* Add strings.ncompare (and backing strncmp_mem) to compare up to n characters of a string.

* Document strings.ncompare.

compiler/res/prog8lib/prog8_lib.asm

@@ -304,6 +304,34 @@ _c1_zero        lda  (P8ZP_SCRATCH_W2),y
 +		rts
 		.pend
 
+strncmp_mem	.proc
+		; --   compares strings in s1 (AY) and s2 (P8ZP_SCRATCH_W2).
+                ;      Compares up to maximum length specified in X.
+		;      Returns -1,0,1 in A, depending on the ordering. Clobbers X & Y.
+		sta  P8ZP_SCRATCH_W1
+		sty  P8ZP_SCRATCH_W1+1
+		ldy  #0
+_loop           lda  (P8ZP_SCRATCH_W1),y
+		beq  _c1_zero
+		cmp  (P8ZP_SCRATCH_W2),y
+		beq  _equal
+		bmi  _less
+		lda  #1
+		rts
+_less           lda  #-1
+		rts
+_equal          dex
+		bne +
+		lda #0
+		rts
++		iny
+		bne  _loop
+_c1_zero        lda  (P8ZP_SCRATCH_W2),y
+		beq  +
+		lda  #-1
++		rts
+		.pend
+
 
 strlen          .proc
         ; -- returns the number of bytes in the string in AY, in Y. Clobbers A.

compiler/res/prog8lib/strings.p8

@@ -243,6 +243,19 @@ _str    .word 0
         }}
     }
 
+    asmsub ncompare(uword string1 @R0, uword string2 @AY, ubyte length @X) clobbers(X, Y) -> byte @A {
+        ; Compares two strings for sorting.
+        ; Returns -1 (255), 0 or 1, meaning: string1 sorts before, equal or after string2.
+        ; Only compares the strings from index 0 up to the length argument.
+        %asm {{
+		sta  P8ZP_SCRATCH_W2
+		sty  P8ZP_SCRATCH_W2+1
+		lda  cx16.r0
+		ldy  cx16.r0+1
+		jmp  prog8_lib.strncmp_mem
+        }}
+    }
+
     asmsub lower(uword st @AY) -> ubyte @Y {
         ; Lowercases the petscii string in-place. Returns length of the string.
         ; (for efficiency, non-letter characters > 128 will also not be left intact,

compiler/test/comparisons/more_compares.p8

@@ -22,6 +22,13 @@ main {
             txt.print("name2 fail!\n")
         }
 
+        if (strings.ncompare(name, "aaa", 3)==0) or (strings.compare(name, "johm", 3)==0) or (strings.compare(name, "bbb", 3)==0) {
+            txt.print("name1 ok\n")
+        }
+        if (strings.ncompare(name, "aaa", 2)==0) or (strings.ncompare(name, "zzz", 2)==0) or (strings.ncompare(name, "bbb", 2)==0) {
+            txt.print("name2 fail!\n")
+        }
+
         if name=="aaa" or name=="john" or name=="bbb"
             txt.print("name1b ok\n")
         if name=="aaa" or name=="zzz" or name=="bbb"

docs/source/libraries.rst

@@ -900,6 +900,12 @@ Provides string manipulation routines.
     using ``==``, ``<`` etcetera (it will use strings.compare for you under water automatically).
     This even works when dealing with uword (pointer) variables when comparing them to a string type.
 
+``ncompare (string1, string2, length) -> ubyte result``
+    Compares two strings up to the number of characters in the length parameter.
+    Returns -1, 0 or 1 depending on whether string1 sorts before, equal or after string2.
+    Note that lengths of 0 or 1 evaluate the same.  The first character is always compared.
+    A length larger than either string will function identically to compare.
+
 ``copy (from, to) -> ubyte length``
     Copy a string to another, overwriting that one. Returns the length of the string that was copied.
     Often you don't have to call this explicitly and can just write ``string1 = string2``

syntax-files/SublimeText/Prog8.sublime-syntax

@@ -154,7 +154,7 @@ contexts:
     - match: (\b(const)\b)
       scope: storage.modifier.prog8
   support:
-    - match: (\b(abs|atan|ceil|cos|cos8u|cos8|cos16u|cos16|deg|floor|ln|log2|rad|round|sin|sgn|sin8u|sin8|sin16u|sin16|sqrt16|sqrt|tan|any|all|len|max|min|reverse|sum|sort|memcopy|memset|memsetw|leftstr|rightstr|strlen|strcmp|substr|exit|lsb|msb|lsw|msw|mkword|rnd|rndw|rndf|rol|rol2|ror|ror2|rsave|rrestore|read_flags|sizeof|set_carry|clear_carry|set_irqd|clear_irqd|swap)\b)
+    - match: (\b(abs|atan|ceil|cos|cos8u|cos8|cos16u|cos16|deg|floor|ln|log2|rad|round|sin|sgn|sin8u|sin8|sin16u|sin16|sqrt16|sqrt|tan|any|all|len|max|min|reverse|sum|sort|memcopy|memset|memsetw|leftstr|rightstr|strlen|strcmp|strncmp|substr|exit|lsb|msb|lsw|msw|mkword|rnd|rndw|rndf|rol|rol2|ror|ror2|rsave|rrestore|read_flags|sizeof|set_carry|clear_carry|set_irqd|clear_irqd|swap)\b)
       scope: support.function.prog8
   variable:
     - match: (\b\w+\b)

syntax-files/Vim/prog8_builtins.vim

@@ -778,6 +778,7 @@ syn match prog8BuiltInFunc "\<strings\.contains\>"
 syn match prog8BuiltInFunc "\<strings\.copy\>"
 syn match prog8BuiltInFunc "\<strings\.append\>"
 syn match prog8BuiltInFunc "\<strings\.compare\>"
+syn match prog8BuiltInFunc "\<strings\.ncompare\>"
 syn match prog8BuiltInFunc "\<strings\.lower\>"
 syn match prog8BuiltInFunc "\<strings\.lowerchar\>"
 syn match prog8BuiltInFunc "\<strings\.upper\>"