Flesh out string byte handling a bit:

- Get rid of public byteAt(_) method on strings. It's redundant and
  longer than .bytes[_].
- Implement bytes.count natively so it's O(1).

builtin/core.wren

@@ -137,9 +137,11 @@ class StringByteSequence is Sequence {
     _string = string
   }
 
-  [index] { _string.byteAt(index) }
+  [index] { _string.byteAt_(index) }
   iterate(iterator) { _string.iterateByte_(iterator) }
-  iteratorValue(iterator) { _string.byteAt(iterator) }
+  iteratorValue(iterator) { _string.byteAt_(iterator) }
+
+  count { _string.byteCount_ }
 }
 
 class List is Sequence {

src/vm/wren_core.c

@@ -151,9 +151,11 @@ static const char* coreLibSource =
 "    _string = string\n"
 "  }\n"
 "\n"
-"  [index] { _string.byteAt(index) }\n"
+"  [index] { _string.byteAt_(index) }\n"
 "  iterate(iterator) { _string.iterateByte_(iterator) }\n"
-"  iteratorValue(iterator) { _string.byteAt(iterator) }\n"
+"  iteratorValue(iterator) { _string.byteAt_(iterator) }\n"
+"\n"
+"  count { _string.byteCount_ }\n"
 "}\n"
 "\n"
 "class List is Sequence {\n"
@@ -1079,6 +1081,11 @@ DEF_PRIMITIVE(string_byteAt)
   RETURN_NUM((uint8_t)string->value[index]);
 }
 
+DEF_PRIMITIVE(string_byteCount)
+{
+  RETURN_NUM(AS_STRING(args[0])->length);
+}
+
 DEF_PRIMITIVE(string_codePointAt)
 {
   ObjString* string = AS_STRING(args[0]);
@@ -1409,7 +1416,8 @@ void wrenInitializeCore(WrenVM* vm)
   PRIMITIVE(vm->stringClass->obj.classObj, "fromCodePoint(_)", string_fromCodePoint);
   PRIMITIVE(vm->stringClass, "+(_)", string_plus);
   PRIMITIVE(vm->stringClass, "[_]", string_subscript);
-  PRIMITIVE(vm->stringClass, "byteAt(_)", string_byteAt);
+  PRIMITIVE(vm->stringClass, "byteAt_(_)", string_byteAt);
+  PRIMITIVE(vm->stringClass, "byteCount_", string_byteCount);
   PRIMITIVE(vm->stringClass, "codePointAt(_)", string_codePointAt);
   PRIMITIVE(vm->stringClass, "contains(_)", string_contains);
   PRIMITIVE(vm->stringClass, "count", string_count);

test/core/string/byte_at.wren

@@ -1,38 +0,0 @@
-// Bytes:           11111
-//        012345678901234
-// Chars: sø mé ஃ  thî ng
-var s = "søméஃthîng"
-
-IO.print(s.byteAt(0)) // expect: 115
-IO.print(s.byteAt(1)) // expect: 195
-IO.print(s.byteAt(2)) // expect: 184
-IO.print(s.byteAt(3)) // expect: 109
-IO.print(s.byteAt(4)) // expect: 195
-IO.print(s.byteAt(5)) // expect: 169
-IO.print(s.byteAt(6)) // expect: 224
-IO.print(s.byteAt(7)) // expect: 174
-IO.print(s.byteAt(8)) // expect: 131
-IO.print(s.byteAt(9)) // expect: 116
-IO.print(s.byteAt(10)) // expect: 104
-IO.print(s.byteAt(11)) // expect: 195
-IO.print(s.byteAt(12)) // expect: 174
-IO.print(s.byteAt(13)) // expect: 110
-IO.print(s.byteAt(14)) // expect: 103
-
-IO.print(s.byteAt(-15)) // expect: 115
-IO.print(s.byteAt(-14)) // expect: 195
-IO.print(s.byteAt(-13)) // expect: 184
-IO.print(s.byteAt(-12)) // expect: 109
-IO.print(s.byteAt(-11)) // expect: 195
-IO.print(s.byteAt(-10)) // expect: 169
-IO.print(s.byteAt(-9)) // expect: 224
-IO.print(s.byteAt(-8)) // expect: 174
-IO.print(s.byteAt(-7)) // expect: 131
-IO.print(s.byteAt(-6)) // expect: 116
-IO.print(s.byteAt(-5)) // expect: 104
-IO.print(s.byteAt(-4)) // expect: 195
-IO.print(s.byteAt(-3)) // expect: 174
-IO.print(s.byteAt(-2)) // expect: 110
-IO.print(s.byteAt(-1)) // expect: 103
-
-IO.print("\0".byteAt(0)) // expect: 0

test/core/string/byte_at_not_int.wren

@@ -1 +0,0 @@
-IO.print("string".byteAt(12.34)) // expect runtime error: Index must be an integer.

test/core/string/byte_at_not_num.wren

@@ -1 +0,0 @@
-IO.print("string".byteAt("not num")) // expect runtime error: Index must be a number.

test/core/string/byte_at_too_large.wren

@@ -1 +0,0 @@
-IO.print("string".byteAt(6)) // expect runtime error: Index out of bounds.

test/core/string/byte_at_too_small.wren

@@ -1 +0,0 @@
-IO.print("string".byteAt(-7)) // expect runtime error: Index out of bounds.

test/core/string_byte_sequence/count.wren

@@ -0,0 +1,15 @@
+// Simple.
+IO.print("".bytes.count) // expect: 0
+IO.print("123".bytes.count) // expect: 3
+
+// UTF-8.
+// Bytes:
+//        123456789
+// Chars: sø mé ஃ
+IO.print("søméஃ".bytes.count) // expect: 9
+
+// Null bytes.
+IO.print("\0\0\0".bytes.count) // expect: 3
+
+// Invalid UTF-8.
+IO.print("\xef\x00".bytes.count) // expect: 2

test/language/string/byte_escapes.wren

@@ -1,12 +1,12 @@
-var s = "\x00\x12\x34\x56\x78\xab\xCD\xfFf"
+var bytes = "\x00\x12\x34\x56\x78\xab\xCD\xfFf".bytes
 
-IO.print(s.byteAt(0)) // expect: 0
-IO.print(s.byteAt(1)) // expect: 18
-IO.print(s.byteAt(2)) // expect: 52
-IO.print(s.byteAt(3)) // expect: 86
-IO.print(s.byteAt(4)) // expect: 120
-IO.print(s.byteAt(5)) // expect: 171
-IO.print(s.byteAt(6)) // expect: 205
-IO.print(s.byteAt(7)) // expect: 255
+IO.print(bytes[0]) // expect: 0
+IO.print(bytes[1]) // expect: 18
+IO.print(bytes[2]) // expect: 52
+IO.print(bytes[3]) // expect: 86
+IO.print(bytes[4]) // expect: 120
+IO.print(bytes[5]) // expect: 171
+IO.print(bytes[6]) // expect: 205
+IO.print(bytes[7]) // expect: 255
 // "f".
-IO.print(s.byteAt(8)) // expect: 102
+IO.print(bytes[8]) // expect: 102