Add compress and image to core.

core/compress/common.odin

@@ -0,0 +1,203 @@
+package compress
+
+import "core:io"
+import "core:image"
+
+// Error helper, e.g. is_kind(err, General_Error.OK);
+is_kind :: proc(u: $U, x: $V) -> bool {
+    v, ok := u.(V);
+    return ok && v == x;
+}
+
+Error :: union {
+	General_Error,
+	Deflate_Error,
+	ZLIB_Error,
+	GZIP_Error,
+	ZIP_Error,
+	/*
+		This is here because png.load will return a this type of error union,
+		as it may involve an I/O error, a Deflate error, etc.
+	*/
+	image.PNG_Error,
+}
+
+General_Error :: enum {
+	OK = 0,
+	File_Not_Found,
+	Cannot_Open_File,
+	File_Too_Short,
+	Stream_Too_Short,
+	Output_Too_Short,
+	Unknown_Compression_Method,
+	Checksum_Failed,
+	Incompatible_Options,
+	Unimplemented,
+}
+
+GZIP_Error :: enum {
+	Invalid_GZIP_Signature,
+	Reserved_Flag_Set,
+	Invalid_Extra_Data,
+	Original_Name_Too_Long,
+	Comment_Too_Long,
+	Payload_Length_Invalid,
+	Payload_CRC_Invalid,
+}
+
+ZIP_Error :: enum {
+	Invalid_ZIP_File_Signature,
+	Unexpected_Signature,
+	Insert_Next_Disk,
+	Expected_End_of_Central_Directory_Record,
+}
+
+ZLIB_Error :: enum {
+	Unsupported_Window_Size,
+	FDICT_Unsupported,
+	Unsupported_Compression_Level,
+	Code_Buffer_Malformed,
+}
+
+Deflate_Error :: enum {
+	Huffman_Bad_Sizes,
+	Huffman_Bad_Code_Lengths,
+	Inflate_Error,
+	Bad_Distance,
+	Bad_Huffman_Code,
+	Len_Nlen_Mismatch,
+	BType_3,
+}
+
+// General context for ZLIB, LZW, etc.
+Context :: struct {
+	code_buffer: u32,
+	num_bits: i8,
+	/*
+		num_bits will be set to -100 if the buffer is malformed
+	*/
+	eof: b8,
+
+	input: io.Stream,
+	output: io.Stream,
+	bytes_written: i64,
+	// Used to update hash as we write instead of all at once
+	rolling_hash: u32,
+
+	// Sliding window buffer. Size must be a power of two.
+	window_size: i64,
+	last: ^[dynamic]byte,
+}
+
+// Stream helpers
+/*
+	TODO: These need to be optimized.
+
+	Streams should really only check if a certain method is available once, perhaps even during setup.
+
+	Bit and byte readers may be merged so that reading bytes will grab them from the bit buffer first.
+	This simplifies end-of-stream handling where bits may be left in the bit buffer.
+*/
+
+read_data :: #force_inline proc(c: ^Context, $T: typeid) -> (res: T, err: io.Error) {
+	b := make([]u8, size_of(T), context.temp_allocator);
+	r, e1 := io.to_reader(c.input);
+	_, e2 := io.read(r, b);
+	if !e1 || e2 != .None {
+		return T{}, e2;
+	}
+
+	res = (^T)(raw_data(b))^;
+	return res, .None;
+}
+
+read_u8 :: #force_inline proc(z: ^Context) -> (res: u8, err: io.Error) {
+	return read_data(z, u8);
+}
+
+peek_data :: #force_inline proc(c: ^Context, $T: typeid) -> (res: T, err: io.Error) {
+	// Get current position to read from.
+	curr, e1 := c.input->impl_seek(0, .Current);
+	if e1 != .None {
+		return T{}, e1;
+	}
+	r, e2 := io.to_reader_at(c.input);
+	if !e2 {
+		return T{}, .Empty;
+	}
+	b := make([]u8, size_of(T), context.temp_allocator);
+	_, e3 := io.read_at(r, b, curr);
+	if e3 != .None {
+		return T{}, .Empty;
+	}
+
+	res = (^T)(raw_data(b))^;
+	return res, .None;
+}
+
+// Sliding window read back
+peek_back_byte :: proc(c: ^Context, offset: i64) -> (res: u8, err: io.Error) {
+	// Look back into the sliding window.
+	return c.last[offset % c.window_size], .None;
+}
+
+// Generalized bit reader LSB
+refill_lsb :: proc(z: ^Context, width := i8(24)) {
+	for {
+		if z.num_bits > width {
+			break;
+		}
+		if z.code_buffer == 0 && z.num_bits == -1 {
+			z.num_bits = 0;
+		}
+		if z.code_buffer >= 1 << uint(z.num_bits) {
+			// Code buffer is malformed.
+			z.num_bits = -100;
+        	return;
+		}
+		c, err := read_u8(z);
+		if err != .None {
+			// This is fine at the end of the file.
+			z.num_bits = -42;
+			z.eof = true;
+			return;
+		}
+		z.code_buffer |= (u32(c) << u8(z.num_bits));
+		z.num_bits += 8;
+	}
+}
+
+consume_bits_lsb :: #force_inline proc(z: ^Context, width: u8) {
+	z.code_buffer >>= width;
+	z.num_bits -= i8(width);
+}
+
+peek_bits_lsb :: #force_inline proc(z: ^Context, width: u8) -> u32 {
+	if z.num_bits < i8(width) {
+		refill_lsb(z);
+	}
+	// assert(z.num_bits >= i8(width));
+	return z.code_buffer & ~(~u32(0) << width);
+}
+
+peek_bits_no_refill_lsb :: #force_inline proc(z: ^Context, width: u8) -> u32 {
+	assert(z.num_bits >= i8(width));
+	return z.code_buffer & ~(~u32(0) << width);
+}
+
+read_bits_lsb :: #force_inline proc(z: ^Context, width: u8) -> u32 {
+	k := peek_bits_lsb(z, width);
+	consume_bits_lsb(z, width);
+	return k;
+}
+
+read_bits_no_refill_lsb :: #force_inline proc(z: ^Context, width: u8) -> u32 {
+	k := peek_bits_no_refill_lsb(z, width);
+	consume_bits_lsb(z, width);
+	return k;
+}
+
+discard_to_next_byte_lsb :: proc(z: ^Context) {
+	discard := u8(z.num_bits & 7);
+	consume_bits_lsb(z, discard);
+}