duktape/website/api/duk_get_buffer.yaml

name: duk_get_buffer

proto: |
  void *duk_get_buffer(duk_context *ctx, duk_idx_t idx, duk_size_t *out_size);

stack: |
  [ ... val! ... ]

summary: |
  <p>Get the data pointer for a (plain) buffer value at <code>idx</code> without
  modifying or coercing the value.  Returns a non-<code>NULL</code> pointer if the value
  is a valid buffer with a non-zero size.  For a zero-size buffer, may return a
  <code>NULL</code> or a non-<code>NULL</code> pointer.  Returns <code>NULL</code>
  if the value is not a buffer or the index is invalid.  If <code>out_size</code> is
  non-<code>NULL</code>, the size of the buffer is written to <code>*out_size</code>; 0
  is written if the return value is <code>NULL</code>.</p>

  <p>If the target value is a fixed buffer, the returned pointer is stable and
  won't change during the lifetime of the buffer.  For dynamic and external
  buffers the pointer may change as the buffer is resized or reconfigured;
  the caller is responsible for ensuring pointer values returned from this API
  call are not used after the buffer is resized/reconfigured.</p>

  <div include="buffer-null-pointer-ambiguity.html" />

example: |
  void *ptr;
  duk_size_t sz;

  ptr = duk_get_buffer(ctx, -3, &sz);
  printf("buf=%p, size=%lu\n", ptr, (unsigned long) sz);

tags:
  - stack
  - buffer

seealso:
  - duk_require_buffer
  - duk_get_buffer_data
  - duk_require_buffer_data

introduced: 1.0.0