jtenner · Jul 18, 2019 · Jul 19, 2019 · Jul 19, 2019 · Jul 31, 2019 · Jul 31, 2019
diff --git a/assembly/buffer/index.ts b/assembly/buffer/index.ts
@@ -1,6 +1,7 @@
 import { BLOCK_MAXSIZE } from "rt/common";
 import { E_INVALIDLENGTH, E_INDEXOUTOFRANGE } from "util/error";
 import { Uint8Array } from "typedarray";
+import { Array } from "array";
 
 export class Buffer extends Uint8Array {
   constructor(size: i32) {
@@ -11,6 +12,42 @@ export class Buffer extends Uint8Array {
     return new Buffer(size);
   }
 
+  public static concat<T>(items: T, length: i32): Buffer {
+    if (!isArray<T>()) {
+      ERROR("Buffer.concat<T> must accept an Array where T extends Array<Uint8Array | Buffer>");
+    }
+    assert(unchecked(items[0]) instanceof Uint8Array); // Can this be a static check?
+
+    let size: usize = 0;
+    let itemCount = usize(items.length);
+    let itemsDataStart = items.dataStart;
+
+    for (let i: usize = 0; i < itemCount; i++) {
+      let item = load<usize>(itemsDataStart + (i << alignof<usize>()));
+      if (item == 0) continue;
+      size += <usize>load<u32>(item, offsetof<Uint8Array>("dataLength"));
+    }
+    size = min<usize>(usize(length), size);
+    assert(items);
+
+    let buffer = __alloc(size, idof<ArrayBuffer>());
+    let result = changetype<Buffer>(__alloc(offsetof<Buffer>(), idof<Buffer>()));
+
+    result.data = changetype<ArrayBuffer>(buffer);
+    result.dataStart = changetype<usize>(buffer);
+    let start: usize = result.dataStart;
+    for (let i: usize = 0; i < itemCount && size > 0; i++) {
+      let item = load<usize>(itemsDataStart + (i << alignof<usize>()));
+      if (item == 0) continue;
+      let count = min<u32>(size, <usize>load<u32>(item, offsetof<Uint8Array>("dataLength")));
+      memory.copy(start, load<usize>(item, offsetof<Uint8Array>("dataStart")), count);
+      start += count;
+      size -= count;
+    }
+
+    return result;
+  }
+
   @unsafe public static allocUnsafe(size: i32): Buffer {
     // Node throws an error if size is less than 0
     if (u32(size) > BLOCK_MAXSIZE) throw new RangeError(E_INVALIDLENGTH);

diff --git a/assembly/node.d.ts b/assembly/node.d.ts
@@ -3,4 +3,6 @@ declare class Buffer extends Uint8Array {
   static alloc(size: i32): Buffer;
   /** This method allocates a new Buffer of indicated size. This is unsafe because the data is not zeroed. */
   static allocUnsafe(size: i32): Buffer;
+  /** This method concatenates an array of `U extends Uint8Array` objects. */
+  static concat<T extends Uint8Array[]>(list: T, totalLength: i32): Buffer;
 }
diff --git a/tests/buffer.spec.ts b/tests/buffer.spec.ts
@@ -42,4 +42,29 @@ describe("buffer", () => {
     // TODO: expectFn(() => { Buffer.allocUnsafe(-1); }).toThrow();
     // TODO: expectFn(() => { Buffer.allocUnsafe(BLOCK_MAXSIZE + 1); }).toThrow();
   });
+
+  test("#concat", () => {
+    let list: Buffer[] = new Array<Buffer>(0);
+    for (let i = 0; i < 5; i++) {
+      let buff = Buffer.alloc(5 - i);
+      for (let j = 0; j < (5 - i); j++) {
+         buff[j] = u8(i);
+      }
+      list.push(buff);
+    }
+    let actual: Buffer = Buffer.concat<Buffer[]>(list, 15);
+
+    let expected: Buffer = Buffer.alloc(15);
+    expected[5] = 1;
+    expected[6] = 1;
+    expected[7] = 1;
+    expected[8] = 1;
+    expected[9] = 2;
+    expected[10] = 2;
+    expected[11] = 2;
+    expected[12] = 3;
+    expected[13] = 3;
+    expected[14] = 4;
+    expect<ArrayBuffer>(actual.buffer).toStrictEqual(expected.buffer);
+  });
 });
diff --git a/tests/node.js b/tests/node.js
@@ -41,14 +41,15 @@ class Reporter extends EmptyReporter {
     else           process.stdout.write("Test      : " + group.name + " -> " + test.name + " ❌ FAIL\n");
 
     if (!test.pass) {
-      process.stdout.write("Actual    : " + test.actual.message + "\n");
-      process.stdout.write("Expected  : " + test.expected.message + "\n");
+      if (test.actual) process.stdout.write("Actual    : " + test.actual.message + "\n");
+      if (test.expected) process.stdout.write("Expected  : " + test.expected.message + "\n");
     }
 
     if (test.logs.length > 0) {
       test.logs.forEach((e, i) => {
         if (i > 0) process.stdout.write("\n");
-        process.stdout.write("Log       : " + e.value);
+        if (e.bytes) process.stdout.write("Log       : " + Buffer.from(e.bytes).toString("hex"));
+        else         process.stdout.write("Log       : " + e.value);
       });
       process.stdout.write("\n");
     }