Buffer.allocUnsafeSlow(size)

• size <integer> 新的 Buffer 所需的长度。

分配 size 个字节的新 Buffer。 如果 size 大于 buffer.constants.MAX_LENGTH 或小于 0，则抛出 ERR_INVALID_OPT_VALUE。 如果 size 为 0，则创建零长度 Buffer。

以这种方式创建的 Buffer 实例的底层内存不会被初始化。 新创建的 Buffer 的内容是未知的，可能包含敏感的数据。 使用 buf.fill(0) 用零初始化此类 Buffer 实例。

当使用 Buffer.allocUnsafe() 分配新的 Buffer 实例时，4KB 以下的分配将从单个预先分配的 Buffer 中切分。 这允许应用程序避免创建许多单独分配的 Buffer 实例的垃圾收集开销。 这种方法无需跟踪和清理尽可能多的单个 ArrayBuffer 对象，从而提高了性能和内存使用率。

但是，在开发人员可能需要在不确定的时间内从池中保留一小块内存的情况下，使用 Buffer.allocUnsafeSlow() 创建未池化的 Buffer 实例然后复制出相关位可能是合适的。

// 需要保留一些小块内存。
const store = [];

socket.on('readable', () => {
  let data;
  while (null !== (data = readable.read())) {
    // 为保留的数据分配。
    const sb = Buffer.allocUnsafeSlow(10);

    // 将数据复制到新分配中。
    data.copy(sb, 0, 0, 10);

    store.push(sb);
  }
});

如果 size 不是数值，则会抛出 TypeError。

• size <integer> The desired length of the new Buffer.

Allocates a new Buffer of size bytes. If size is larger than buffer.constants.MAX_LENGTH or smaller than 0, ERR_INVALID_OPT_VALUE is thrown. A zero-length Buffer is created if size is 0.

The underlying memory for Buffer instances created in this way is not initialized. The contents of the newly created Buffer are unknown and may contain sensitive data. Use buf.fill(0) to initialize such Buffer instances with zeroes.

When using Buffer.allocUnsafe() to allocate new Buffer instances, allocations under 4KB are sliced from a single pre-allocated Buffer. This allows applications to avoid the garbage collection overhead of creating many individually allocated Buffer instances. This approach improves both performance and memory usage by eliminating the need to track and clean up as many individual ArrayBuffer objects.

However, in the case where a developer may need to retain a small chunk of memory from a pool for an indeterminate amount of time, it may be appropriate to create an un-pooled Buffer instance using Buffer.allocUnsafeSlow() and then copying out the relevant bits.

// Need to keep around a few small chunks of memory.
const store = [];

socket.on('readable', () => {
  let data;
  while (null !== (data = readable.read())) {
    // Allocate for retained data.
    const sb = Buffer.allocUnsafeSlow(10);

    // Copy the data into the new allocation.
    data.copy(sb, 0, 0, 10);

    store.push(sb);
  }
});

A TypeError will be thrown if size is not a number.