Allow buffer/blit to take explicit nils for default args.

Also small changes for range checking code.

src/core/buffer.c

@@ -462,13 +462,15 @@ JANET_CORE_FN(cfun_buffer_blit,
     int same_buf = src.bytes == dest->data;
     int32_t offset_dest = 0;
     int32_t offset_src = 0;
-    if (argc > 2)
+    if (argc > 2 && !janet_checktype(argv[2], JANET_NIL))
         offset_dest = janet_gethalfrange(argv, 2, dest->count, "dest-start");
-    if (argc > 3)
+    if (argc > 3 && !janet_checktype(argv[3], JANET_NIL))
         offset_src = janet_gethalfrange(argv, 3, src.len, "src-start");
     int32_t length_src;
     if (argc > 4) {
-        int32_t src_end = janet_gethalfrange(argv, 4, src.len, "src-end");
+        int32_t src_end = src.len;
+        if (!janet_checktype(argv[4], JANET_NIL))
+            src_end = janet_gethalfrange(argv, 4, src.len, "src-end");
         length_src = src_end - offset_src;
         if (length_src < 0) length_src = 0;
     } else {

src/core/capi.c

@@ -342,6 +342,20 @@ int32_t janet_gethalfrange(const Janet *argv, int32_t n, int32_t length, const c
     return not_raw;
 }
 
+int32_t janet_getstartrange(const Janet *argv, int32_t argc, int32_t n, int32_t length) {
+    if (n >= argc || janet_checktype(argv[n], JANET_NIL)) {
+        return 0;
+    }
+    return janet_gethalfrange(argv, n, length, "start");
+}
+
+int32_t janet_getendrange(const Janet *argv, int32_t argc, int32_t n, int32_t length) {
+    if (n >= argc || janet_checktype(argv[n], JANET_NIL)) {
+        return length;
+    }
+    return janet_gethalfrange(argv, n, length, "end");
+}
+
 int32_t janet_getargindex(const Janet *argv, int32_t n, int32_t length, const char *which) {
     int32_t raw = janet_getinteger(argv, n);
     int32_t not_raw = raw;
@@ -394,24 +408,10 @@ JanetRange janet_getslice(int32_t argc, const Janet *argv) {
     janet_arity(argc, 1, 3);
     JanetRange range;
     int32_t length = janet_length(argv[0]);
-    if (argc == 1) {
+    range.start = janet_getstartrange(argv, argc, 1, length);
-        range.start = 0;
+    range.end = janet_getendrange(argv, argc, 2, length);
-        range.end = length;
-    } else if (argc == 2) {
-        range.start = janet_checktype(argv[1], JANET_NIL)
-                      ? 0
-                      : janet_gethalfrange(argv, 1, length, "start");
-        range.end = length;
-    } else {
-        range.start = janet_checktype(argv[1], JANET_NIL)
-                      ? 0
-                      : janet_gethalfrange(argv, 1, length, "start");
-        range.end = janet_checktype(argv[2], JANET_NIL)
-                    ? length
-                    : janet_gethalfrange(argv, 2, length, "end");
     if (range.end < range.start)
         range.end = range.start;
-    }
     return range;
 }
 

src/include/janet.h

@@ -1997,6 +1997,8 @@ JANET_API JanetDictView janet_getdictionary(const Janet *argv, int32_t n);
 JANET_API void *janet_getabstract(const Janet *argv, int32_t n, const JanetAbstractType *at);
 JANET_API JanetRange janet_getslice(int32_t argc, const Janet *argv);
 JANET_API int32_t janet_gethalfrange(const Janet *argv, int32_t n, int32_t length, const char *which);
+JANET_API int32_t janet_getstartrange(const Janet *argv, int32_t argc, int32_t n, int32_t length);
+JANET_API int32_t janet_getendrange(const Janet *argv, int32_t argc, int32_t n, int32_t length);
 JANET_API int32_t janet_getargindex(const Janet *argv, int32_t n, int32_t length, const char *which);
 JANET_API uint64_t janet_getflags(const Janet *argv, int32_t n, const char *flags);
 

test/suite-buffer.janet

@@ -103,6 +103,7 @@
 (assert (deep= @"bcde" (buffer/blit @"" a -1 1 5)) "buffer/blit 3")
 (assert (deep= @"cde" (buffer/blit @"" a -1 2 5)) "buffer/blit 4")
 (assert (deep= @"de" (buffer/blit @"" a -1 3 5)) "buffer/blit 5")
+(assert (deep= @"de" (buffer/blit @"" a nil 3 5)) "buffer/blit 6")
 
 # buffer/push-at
 # c55d93512