duktape/website/api/duk_get_buffer.txt

=proto
void *duk_get_buffer(duk_context *ctx, duk_idx_t index, duk_size_t *out_size);

=stack
[ ... val! ... ]

=summary
<p>Get the data pointer for a buffer value at <code>index</code> without modifying
or coercing the value.  Returns a non-<code>NULL</code> pointer if the value is a
valid buffer (fixed or dynamic) with a non-zero size.  For a zero-size buffer,
may return a <code>NULL</code> or a <code>non-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>

<div class="note">
There is no reliable way to distinguish a zero-size buffer from a non-buffer
based on the return values.  A <code>NULL</code> with zero size is returned for
a non-buffer.  The same values may be returned for a zero-size buffer (although
it is also possible that a non-<code>NULL</code> pointer is returned).
</div>

=example
void *ptr;
duk_size_t sz;

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

=tags
stack
buffer