Heap fill/compare; Std string experiments

std/assembly/string.ts

@@ -1,4 +1,98 @@
 @global()
 export class String {
-  // TODO
+
+  private ptr: usize;
+  readonly length: u32;
+
+  constructor(ptr: usize, len: u32) {
+    this.ptr = ptr;
+    this.length = len;
+  }
+
+  charAt(index: u32): String {
+    assert(this != null && index < this.length);
+    return new String(this.ptr + (index << 1), 1);
+  }
+
+  charCodeAt(index: u32): u16 {
+    assert(this != null && index < this.length);
+    return load<u16>(this.ptr + (index << 1));
+  }
+
+  @operator("+")
+  concat(other: String): String {
+    assert(this != null && other != null);
+    const len: u32 = this.length + other.length;
+    const ptr: usize = Heap.allocate(len << 1);
+    Heap.copy(ptr, this.ptr, this.length << 1);
+    Heap.copy(ptr, this.ptr + (len << 1), other.length << 1);
+    return new String(ptr, len);
+  }
+
+  endsWith(other: String): bool {
+    assert(this != null && other != null);
+    if (other.length > this.length)
+      return false;
+    for (let i: u32 = this.length - other.length, j: u32 = 0, k: u32 = this.length; i < k;)
+      if (this.charCodeAt(i++) != other.charCodeAt(j++))
+        return false;
+    return true;
+  }
+
+  @operator("==")
+  equals(other: String): bool {
+    assert(this != null && other != null);
+    if (this.length != other.length)
+      return false;
+    for (let i: u32 = 0, k: u32 = this.length; i < k; ++i)
+      if (this.charCodeAt(i) != other.charCodeAt(i))
+        return false;
+    return true;
+  }
+
+  indexOf(other: String): u32 {
+    assert(this != null && other != null);
+    throw new Error("not implemented");
+  }
+
+  startsWith(other: String): bool {
+    assert(this != null && other != null);
+    if (other.length > this.length)
+      return false;
+    for (let i: u32 = 0, k: u32 = other.length; i < k; ++i)
+      if (this.charCodeAt(i) != other.charCodeAt(i))
+        return false;
+    return true;
+  }
+
+  substr(start: u32, length: u32 = <u32>-1): String {
+    assert(this != null);
+    if (start >= this.length)
+      return changetype<string,String>("");
+    const len: u32 = min<u32>(length, this.length - start);
+    return new String(this.ptr + (start << 1), len);
+  }
+
+  substring(start: u32, end: u32 = <u32>-1): String {
+    assert(this != null);
+    if (start >= this.length || end <= start)
+      return changetype<string,String>("");
+    const len: u32 = min<u32>(end - start, this.length - start);
+    return new String(this.ptr + (start << 1), len);
+  }
+
+  trim(): string {
+    assert(this != null);
+    throw new Error("not implemented");
+  }
+
+  trimLeft(): string {
+    assert(this != null);
+    throw new Error("not implemented");
+  }
+
+  trimRight(): string {
+    assert(this != null);
+    throw new Error("not implemented");
+  }
 }