std/png/decode_png.wuffs

// Copyright 2020 The Wuffs Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use "std/crc32"
use "std/zlib"

pub status "#bad header"
pub status "#unsupported PNG file"

pub const DECODER_WORKBUF_LEN_MAX_INCL_WORST_CASE : base.u64 = 0

pub struct decoder? implements base.image_decoder(
	// The 0x00FF_FFFF limit is arbitrary (the PNG spec says 0x7FFF_FFFF) but
	// it means that (width * height * bytes_per_pixel) doesn't overflow.
	width  : base.u32[..= 0x00FF_FFFF],
	height : base.u32[..= 0x00FF_FFFF],

	// bytes_per_row doesn't include the 1 byte for the per-row filter.
	bytes_per_row : base.u64[..= 0x07FF_FFF8],

	workbuf_wi     : base.u64,
	workbuf_length : base.u64[..= 0x0007_FFFF_F100_0007],

	// Call sequence states:
	//  - 0x00: initial state.
	//  - 0x03: image config decoded.
	//  - 0x04: frame config decoded.
	//  - 0xFF: end-of-data, usually after (the non-animated) frame decoded.
	//
	// State transitions:
	//
	//  - 0x00 -> 0x03: via DIC
	//  - 0x00 -> 0x04: via DFC with implicit DIC
	//  - 0x00 -> 0xFF: via DF  with implicit DIC and DFC
	//
	//  - 0x03 -> 0x04: via DFC
	//  - 0x03 -> 0xFF: via DF  with implicit DFC
	//
	//  - 0x04 -> 0xFF: via DFC
	//  - 0x04 -> 0xFF: via DF
	//
	//  - ???? -> 0x03: via RF  for ???? > 0x00
	//
	// Where:
	//  - DF  is decode_frame
	//  - DFC is decode_frame_config, implicit means nullptr args.dst
	//  - DIC is decode_image_config, implicit means nullptr args.dst
	//  - RF  is restart_frame
	call_sequence : base.u8,

	depth : base.u8[..= 16],

	src_pixfmt : base.u32,

	chunk_type   : base.u32,
	chunk_length : base.u64,

	frame_config_io_position : base.u64,

	swizzler : base.pixel_swizzler,
	util     : base.utility,
)(
	crc  : crc32.ieee_hasher,
	zlib : zlib.decoder,
)

pub func decoder.set_quirk_enabled!(quirk: base.u32, enabled: base.bool) {
}

pub func decoder.decode_image_config?(dst: nptr base.image_config, src: base.io_reader) {
	var magic      : base.u64
	var a32        : base.u32
	var a8         : base.u8
	var dst_pixfmt : base.u32

	if this.call_sequence <> 0 {
		return base."#bad call sequence"
	}

	magic = args.src.read_u64le?()
	if magic <> '\x89PNG\x0D\x0A\x1A\x0A'le {
		return "#bad header"
	}

	magic = args.src.read_u64le?()
	if magic <> '\x00\x00\x00\x0DIHDR'le {
		return "#bad header"
	}

	a32 = args.src.read_u32be?()
	if a32 >= 0x8000_0000 {
		return "#bad header"
	} else if a32 >= 0x0100_0000 {
		return "#unsupported PNG file"
	}
	this.width = a32

	a32 = args.src.read_u32be?()
	if a32 >= 0x8000_0000 {
		return "#bad header"
	} else if a32 >= 0x0100_0000 {
		return "#unsupported PNG file"
	}
	this.height = a32

	// Depth.
	a8 = args.src.read_u8?()
	if a8 > 16 {
		return "#bad header"
	}
	this.depth = a8

	// Color.
	a8 = args.src.read_u8?()
	if a8 == 0 {
		dst_pixfmt = base.PIXEL_FORMAT__Y
		this.src_pixfmt = base.PIXEL_FORMAT__Y
		if this.depth == 8 {
			this.bytes_per_row = (this.width as base.u64) * 1
		} else {
			return "#unsupported PNG file"
		}
	} else if a8 == 2 {
		dst_pixfmt = base.PIXEL_FORMAT__BGR
		this.src_pixfmt = base.PIXEL_FORMAT__RGB
		if this.depth == 8 {
			this.bytes_per_row = (this.width as base.u64) * 3
		} else {
			return "#unsupported PNG file"
		}
	} else {
		return "#unsupported PNG file"
	}
	this.workbuf_length = (this.height as base.u64) * (1 + this.bytes_per_row)

	// Compression.
	a8 = args.src.read_u8?()
	if a8 <> 0 {
		return "#bad header"
	}

	// Filter.
	a8 = args.src.read_u8?()
	if a8 <> 0 {
		return "#bad header"
	}

	// Interlace.
	a8 = args.src.read_u8?()
	if a8 == 0 {
		// No-op.
	} else if a8 == 1 {
		return "#unsupported PNG file"
	} else {
		return "#bad header"
	}

	// TODO: verify CRC-32 checksum.
	args.src.skip_u32?(n: 4)

	// Read up until an IDAT chunk.
	while true {
		this.chunk_length = args.src.read_u32be_as_u64?()
		this.chunk_type = args.src.read_u32le?()
		if this.chunk_type == 'IDAT'le {
			break
		}
		args.src.skip?(n: this.chunk_length)
		// TODO: verify CRC-32 checksum.
		args.src.skip_u32?(n: 4)
	} endwhile

	this.frame_config_io_position = args.src.position()

	if args.dst <> nullptr {
		args.dst.set!(
			pixfmt: dst_pixfmt,
			pixsub: 0,
			width: this.width,
			height: this.height,
			first_frame_io_position: this.frame_config_io_position,
			first_frame_is_opaque: false)
	}

	this.call_sequence = 3
}

pub func decoder.decode_frame_config?(dst: nptr base.frame_config, src: base.io_reader) {
	if this.call_sequence < 3 {
		this.decode_image_config?(dst: nullptr, src: args.src)
	} else if this.call_sequence == 3 {
		if this.frame_config_io_position <> args.src.position() {
			return base."#bad restart"
		}
	} else if this.call_sequence == 4 {
		this.call_sequence = 0xFF
		return base."@end of data"
	} else {
		return base."@end of data"
	}

	if args.dst <> nullptr {
		args.dst.set!(bounds: this.util.make_rect_ie_u32(
			min_incl_x: 0,
			min_incl_y: 0,
			max_excl_x: this.width,
			max_excl_y: this.height),
			duration: 0,
			index: 0,
			io_position: this.frame_config_io_position,
			disposal: 0,
			opaque_within_bounds: false,
			overwrite_instead_of_blend: false,
			background_color: 0x0000_0000)
	}

	this.call_sequence = 4
}

pub func decoder.decode_frame?(dst: ptr base.pixel_buffer, src: base.io_reader, blend: base.pixel_blend, workbuf: slice base.u8, opts: nptr base.decode_frame_options) {
	var w           : base.io_writer
	var w_mark      : base.u64
	var r_mark      : base.u64
	var zlib_status : base.status

	if this.call_sequence < 4 {
		this.decode_frame_config?(dst: nullptr, src: args.src)
	} else if this.call_sequence == 4 {
		// No-op.
	} else {
		return base."@end of data"
	}

	this.workbuf_wi = 0
	while true {
		if (this.workbuf_wi >= this.workbuf_length) or (
			this.workbuf_length >= args.workbuf.length()) {
			return base."#bad workbuf length"
		}
		io_bind (io: w, data: args.workbuf[this.workbuf_wi .. this.workbuf_length]) {
			io_limit (io: args.src, limit: this.chunk_length) {
				w_mark = w.mark()
				r_mark = args.src.mark()
				zlib_status =? this.zlib.transform_io?(
					dst: w, src: args.src, workbuf: this.util.empty_slice_u8())
				this.chunk_length ~sat-= args.src.count_since(mark: r_mark)
				this.workbuf_wi ~sat+= w.count_since(mark: w_mark)
			}
		}

		if zlib_status.is_ok() {
			break
		} else if zlib_status == base."$short write" {
			return base."#too much data"
		} else if zlib_status <> base."$short read" {
			return zlib_status
		} else if this.chunk_length == 0 {
			// TODO: move to the next IDAT.
		}
		yield? base."$short read"
	} endwhile

	if this.workbuf_wi <> this.workbuf_length {
		return base."#not enough data"
	}

	this.call_sequence = 0xFF
}

pub func decoder.frame_dirty_rect() base.rect_ie_u32 {
	return this.util.make_rect_ie_u32(
		min_incl_x: 0,
		min_incl_y: 0,
		max_excl_x: this.width,
		max_excl_y: this.height)
}

pub func decoder.num_animation_loops() base.u32 {
	return 0
}

pub func decoder.num_decoded_frame_configs() base.u64 {
	if this.call_sequence > 3 {
		return 1
	}
	return 0
}

pub func decoder.num_decoded_frames() base.u64 {
	if this.call_sequence > 4 {
		return 1
	}
	return 0
}

pub func decoder.restart_frame!(index: base.u64, io_position: base.u64) base.status {
	if this.call_sequence < 3 {
		return base."#bad call sequence"
	}
	if args.index <> 0 {
		return base."#bad argument"
	}
	this.call_sequence = 3
	this.frame_config_io_position = args.io_position
	return ok
}

pub func decoder.set_report_metadata!(fourcc: base.u32, report: base.bool) {
	// TODO.
}

pub func decoder.tell_me_more?(dst: base.io_writer, minfo: nptr base.more_information, src: base.io_reader) {
	return base."#no more information"
}

pub func decoder.workbuf_len() base.range_ii_u64 {
	return this.util.make_range_ii_u64(
		min_incl: this.workbuf_length,
		max_incl: this.workbuf_length)
}