Caller-owned composite buffers – the module's entire memory footprint. More...

#include <zoom.h>

Data Fields
uint8_t *	row
	One source row, >= dst.w bytes.
uint32_t	row_cap
	Capacity of `row`, bytes.
uint8_t *	strip
	gray8 destination strip, dst.w * strip_rows.
uint32_t	strip_cap
	Capacity of `strip`, bytes.
uint8_t *	packed
	The strip packed to 4 bpp (2 px/byte).
uint32_t	packed_cap
	Capacity of `packed`, bytes.

Detailed Description

Caller-owned composite buffers – the module's entire memory footprint.

Three buffers, all supplied by the caller and none allocated: one source row, one destination strip in gray8, and the same strip packed to 4 bpp. Sizing is a function of the viewport width alone, never its height, which is the whole point of the strip pipeline (see the file docblock):

row_cap >= dst.w – the widest source row a frame reads
strip_cap >= dst.w – at least one destination row
packed_cap >= (dst.w * strip_rows + 1)/2 – with strip_rows = strip_cap / dst.w

zoom_view_open derives strip_rows from strip_cap and rejects a packed_cap that cannot hold it, so an under-sized buffer is a startup error and never a partial frame.

Invariant: No pointer is NULL and no capacity is zero in an opened view.; The three buffers do not overlap.

Example:: static uint8_t s_row[1024], s_strip[1024 * 16], s_packed[(1024 * 16) / 2];

cfg.scratch = (zoom_scratch_t){ .row = s_row, .row_cap = sizeof(s_row),

.strip = s_strip, .strip_cap = sizeof(s_strip),

.packed = s_packed, .packed_cap = sizeof(s_packed) };

s_strip
static longstrip_t s_strip
Opened longstrip scroll state.
Definition main.c:271

s_packed
static uint8_t s_packed[k_ez_packed_bytes]
Composite scratch: the dithered strip packed to 4 bpp (SRAM).
Definition main.c:211

s_row
static uint8_t s_row[k_ez_row_bytes]
Composite scratch: one source row at the widest viewport (SRAM).
Definition main.c:190

zoom_scratch_t
Caller-owned composite buffers – the module's entire memory footprint.
Definition zoom.h:335

zoom_scratch_t::strip_cap
uint32_t strip_cap
Capacity of strip, bytes.
Definition zoom.h:339

zoom_scratch_t::strip
uint8_t * strip
gray8 destination strip, dst.w * strip_rows.
Definition zoom.h:338