Implement String#slice (AssemblyScript#404)

Author: LiaoPeng

std/assembly/index.d.ts

@@ -682,6 +682,7 @@ declare class String {
  padStart(targetLength: i32, padString?: string): string;
  padEnd(targetLength: i32, padString?: string): string;
  repeat(count?: i32): string;
+ slice(beginIndex: i32, endIndex?: i32): string;
  split(separator?: string, limit?: i32): string[];
  toString(): string;
  static fromUTF8(ptr: usize, len: usize): string;

std/assembly/string.ts

@@ -413,6 +413,17 @@ export class String {
  return result;
  }
 
+ slice(beginIndex: i32, endIndex: i32 = i32.MAX_VALUE): String {
+ var length = this.length;
+ var begin = (beginIndex < 0) ? max(beginIndex + length, 0) : min(beginIndex, length);
+ var end = (endIndex < 0) ? max(endIndex + length, 0) : min(endIndex, length);
+ var len = end - begin;
+ if (len <= 0) return changetype<String>("");
+ var out = allocateUnsafe(len);
+ copyUnsafe(out, 0, this, begin, len);
+ return out;
+ }
+
  split(separator: String = null, limit: i32 = i32.MAX_VALUE): String[] {
  assert(this !== null);
  if (!limit) return new Array<String>();

std/portable/index.d.ts

@@ -427,6 +427,7 @@ declare class String {
  padEnd(targetLength: i32, padString?: string): string;
  replace(search: string, replacement: string): string;
  repeat(count?: i32): string;
+ slice(beginIndex: i32, endIndex?: i32): string;
  split(separator?: string, limit?: i32): string[];
  toString(): string;
 }

tests/compiler/std/string-utf8.optimized.wat

@@ -1575,7 +1575,7 @@
  if
  i32.const 0
  i32.const 72
- i32.const 510
+ i32.const 521
  i32.const 8
  call $~lib/env/abort
  unreachable
@@ -1622,7 +1622,7 @@
  if
  i32.const 0
  i32.const 72
- i32.const 514
+ i32.const 525
  i32.const 8
  call $~lib/env/abort
  unreachable
@@ -1695,7 +1695,7 @@
  if
  i32.const 0
  i32.const 72
- i32.const 526
+ i32.const 537
  i32.const 8
  call $~lib/env/abort
  unreachable
@@ -1748,7 +1748,7 @@
  if
  i32.const 0
  i32.const 72
- i32.const 535
+ i32.const 546
  i32.const 4
  call $~lib/env/abort
  unreachable

tests/compiler/std/string-utf8.untouched.wat

@@ -2001,7 +2001,7 @@
  if
  i32.const 0
  i32.const 72
- i32.const 510
+ i32.const 521
  i32.const 8
  call $~lib/env/abort
  unreachable
@@ -2055,7 +2055,7 @@
  if
  i32.const 0
  i32.const 72
- i32.const 514
+ i32.const 525
  i32.const 8
  call $~lib/env/abort
  unreachable
@@ -2150,7 +2150,7 @@
  if
  i32.const 0
  i32.const 72
- i32.const 526
+ i32.const 537
  i32.const 8
  call $~lib/env/abort
  unreachable
@@ -2213,7 +2213,7 @@
  if
  i32.const 0
  i32.const 72
- i32.const 535
+ i32.const 546
  i32.const 4
  call $~lib/env/abort
  unreachable

tests/compiler/std/string.optimized.wat

@@ -4,7 +4,6 @@ import {
  itoa32,
  utoa64,
  itoa64,
- itoa,
  dtoa
 } from "internal/number";
 
@@ -143,6 +142,16 @@ assert("a".repeat(5) == "aaaaa");
 assert("a".repeat(6) == "aaaaaa");
 assert("a".repeat(7) == "aaaaaaa");
 
+// test cases for slice method
+str = "abcdefghijklmn";
+assert(str.slice(0) == "abcdefghijklmn");
+assert(str.slice(-1) == "n");
+assert(str.slice(-5) == "jklmn");
+assert(str.slice(2, 7) == "cdefg");
+assert(str.slice(-11, -6) == "defgh");
+assert(str.slice(4, 3) == "");
+assert(str.slice(0, -1) == "abcdefghijklm");
+
 var sa: string[];
 
 sa = "".split();