VipsSourcemap

void*
vips_source_map (
  VipsSource* source,
  size_t* length
)

Map the source entirely into memory and return a pointer to the start. If length is non-NULL, the source size is written to it.

This operation can take a long time. Use vips_source_is_mappable() to check if a source can be mapped efficiently.

The pointer is valid for as long as source is alive.

`length`	`size_t*`
	Return the file length here, or `NULL`
	The data is owned by the caller of the function.

Returns:	`gpointer`
	A pointer to the start of the file contents, or `NULL` on error.
	The data is owned by the instance.
	The return value can be `NULL`.