FEAT: added functional /PART and /SEEK refinements for WRITE action on CHECKSUM port

Possible usage:

data: #{0bad}
port: open checksum://
sum1: read write port bin
sum2: read write/part open port tail bin -2 ;port was restarted using OPEN
sum3: read write/seek/part open port bin 2 -2
all [sum1 = sum2 sum1 = sum3] ;== true

Author: Oldes

src/core/p-checksum.c

@@ -99,6 +99,7 @@
 	REBVAL *method;
 	REBREQ *req;
 	REBVAL *arg;
+	REBCNT  args = 0;
 	REBVAL *data;
 	REBVAL *ctx;
 	REBYTE *temp;
@@ -128,16 +129,38 @@
 			Checksum_Open(port, method, ctx_size);
 			SET_OPEN(req);
 		}
+		args = Find_Refines(ds, ALL_WRITE_REFS);
 		arg = D_ARG(2);
+		REBYTE *bin = VAL_BIN_DATA(arg);
+		REBI64  pos = (REBI64)VAL_INDEX(arg);
+		if (args & AM_WRITE_SEEK) {
+			pos += Int64(D_ARG(ARG_WRITE_INDEX));
+			if(pos < 0) pos = 0;
+			else if (pos > VAL_TAIL(arg)) pos = VAL_TAIL(arg);
+		}
+		REBI64 part = (REBI64)VAL_TAIL(arg) - pos;
+		if (args & AM_WRITE_PART) {	
+			REBI64 cnt = Int64(D_ARG(ARG_WRITE_LENGTH));
+			if(cnt < 0) {
+				cnt = -cnt;
+				pos -= cnt;
+				if (pos < 0) {
+					cnt += pos;
+					pos = 0;
+				}
+				part = cnt;
+			} else if (cnt < part) part = cnt;
+		}
+		if(part <= 0) return R_RET;
 		switch (VAL_WORD_CANON(method)) {
 			case SYM_MD5:
-				MD5_Update((MD5_CTX*)VAL_BIN(ctx), VAL_BIN_DATA(arg), VAL_TAIL(arg) - VAL_INDEX(arg));
+				MD5_Update((MD5_CTX*)VAL_BIN(ctx), VAL_BIN_SKIP(arg, pos), part);
 				break;
 			case SYM_SHA1:
-				SHA1_Update((SHA_CTX*)VAL_BIN(ctx), VAL_BIN_DATA(arg), VAL_TAIL(arg) - VAL_INDEX(arg));
+				SHA1_Update((SHA_CTX*)VAL_BIN(ctx), VAL_BIN_SKIP(arg, pos), part);
 				break;
 			case SYM_SHA256:
-				SHA256_Update((SHA256_CTX*)VAL_BIN(ctx), VAL_BIN_DATA(arg), VAL_TAIL(arg) - VAL_INDEX(arg));
+				SHA256_Update((SHA256_CTX*)VAL_BIN(ctx), VAL_BIN_SKIP(arg, pos), part);
 				break;
 			}
 		break;
@@ -176,7 +199,6 @@
 		return R_RET;
 
 	case A_OPEN:
-		if (IS_OPEN(req)) return R_RET;
 		if (Checksum_Open(port, method, ctx_size)) {
 			SET_OPEN(req);
 		} else {

src/tests/units/checksum-test.r3

@@ -77,6 +77,25 @@ Rebol [
 		--assert sum1 = port/data
 		close port
 
+	--test-- "checksum-write-refinements"
+		port: open checksum://
+		write/part port bin 1
+		write/part port next bin 1
+		sum1: checksum/method bin port/spec/method
+		sum2: checksum/method join bin bin port/spec/method
+		--assert sum1 = read port
+		--assert sum1 = read write/part port bin 0
+		--assert sum1 = read write/part port bin -1
+		--assert sum2 = read write/part port tail bin -2
+		port: open checksum://
+		--assert sum1 = read write/seek/part port #{cafe0bad} 2 2
+		;opening already opened port restarts computation
+		--assert sum1 = read write/seek/part open port #{cafe0bad} 2 2
+		--assert sum1 = read write/seek/part open port tail #{cafe0bad} -2 2
+
+
+
+
 ===end-group===
 
 ~~~end-file~~~