Function decodeLiteralsHeader [src]
Decode a literals section header.
Errors returned:
error.EndOfStream if there are not enough bytes in source
Prototype
pub fn decodeLiteralsHeader(source: anytype) !LiteralsSection.Header Source
pub fn decodeLiteralsHeader(source: anytype) !LiteralsSection.Header {
const byte0 = try source.readByte();
const block_type = @as(LiteralsSection.BlockType, @enumFromInt(byte0 & 0b11));
const size_format = @as(u2, @intCast((byte0 & 0b1100) >> 2));
var regenerated_size: u20 = undefined;
var compressed_size: ?u18 = null;
switch (block_type) {
.raw, .rle => {
switch (size_format) {
0, 2 => {
regenerated_size = byte0 >> 3;
},
1 => regenerated_size = (byte0 >> 4) + (@as(u20, try source.readByte()) << 4),
3 => regenerated_size = (byte0 >> 4) +
(@as(u20, try source.readByte()) << 4) +
(@as(u20, try source.readByte()) << 12),
}
},
.compressed, .treeless => {
const byte1 = try source.readByte();
const byte2 = try source.readByte();
switch (size_format) {
0, 1 => {
regenerated_size = (byte0 >> 4) + ((@as(u20, byte1) & 0b00111111) << 4);
compressed_size = ((byte1 & 0b11000000) >> 6) + (@as(u18, byte2) << 2);
},
2 => {
const byte3 = try source.readByte();
regenerated_size = (byte0 >> 4) + (@as(u20, byte1) << 4) + ((@as(u20, byte2) & 0b00000011) << 12);
compressed_size = ((byte2 & 0b11111100) >> 2) + (@as(u18, byte3) << 6);
},
3 => {
const byte3 = try source.readByte();
const byte4 = try source.readByte();
regenerated_size = (byte0 >> 4) + (@as(u20, byte1) << 4) + ((@as(u20, byte2) & 0b00111111) << 12);
compressed_size = ((byte2 & 0b11000000) >> 6) + (@as(u18, byte3) << 2) + (@as(u18, byte4) << 10);
},
}
},
}
return LiteralsSection.Header{
.block_type = block_type,
.size_format = size_format,
.regenerated_size = regenerated_size,
.compressed_size = compressed_size,
};
}