// The PNG magic number.
export const magic: [_]u8 = [137, 80, 78, 71, 13, 10, 26, 10];

def MAGIC_LEN: size = 8;

// The chunk header type for an IHDR chunk.
export def IHDR: u32 = 0x49484452;

// The chunk header type for a PLTE chunk.
export def PLTE: u32 = 0x504c5445;

// The chunk header type for an IDAT chunk.
export def IDAT: u32 = 0x49444154;

// The chunk header type for an IEND chunk.
export def IEND: u32 = 0x49454e44;

// The chunk header type for a tRNS chunk.
export def TRNS: u32 = 0x74524e53;

// The chunk header type for a gAMA chunk.
export def GAMA: u32 = 0x67414d41;

// The chunk header type for an sRGB chunk.
export def SRGB: u32 = 0x73524742;

// The chunk header type for an iCCP chunk.
export def ICCP: u32 = 0x69434350;

// The chunk header type for a tEXT chunk.
export def TEXT: u32 = 0x74455854;

// The chunk header type for a zTXT chunk.
export def ZTXT: u32 = 0x7a545854;

// The chunk header type for an iTXT chunk.
export def ITXT: u32 = 0x69545854;

// The chunk header type for a bKGD chunk.
export def BKGD: u32 = 0x624b4744;

// The chunk header type for a pHYS chunk.
export def PHYS: u32 = 0x70485953;

// The chunk header type for a sBIT chunk.
export def SBIT: u32 = 0x73424954;

// The chunk header type for a sPLT chunk.
export def SPLT: u32 = 0x73504c54;

// The chunk header type for a hIST chunk.
export def HIST: u32 = 0x68495354;

// The chunk header type for a tIME chunk.
export def TIME: u32 = 0x74494d45;

// Returns true if the given chunk type is a "critical" chunk.
export fn is_critical(ctype: u32) bool = {
	return ctype & (1 << 29) == 0;
};

@test fn is_critical() void = {
	assert(is_critical(IHDR) == true);
	assert(is_critical(PLTE) == true);
	assert(is_critical(IDAT) == true);
	assert(is_critical(IEND) == true);
	assert(is_critical(HIST) == false);
	assert(is_critical(TIME) == false);
};