Zig 0.17.0-dev (Split by item)

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dynamicCodeLength

Decode code length symbol to code length. Writes decoded length into lens slice starting at position pos. Returns number of positions advanced.

Decompress.dynamicCodeLength

fn dynamicCodeLength(self: *Decompress, code: u16, lens: []u4, pos: usize) !usize

File

lib/std/compress/flate/Decompress.zig:202

Code

fn dynamicCodeLength(self: *Decompress, code: u16, lens: []u4, pos: usize) !usize {
    if (pos >= lens.len)
        return error.InvalidDynamicBlockHeader;

    switch (code) {
        0...15 => {
            // Represent code lengths of 0 - 15
            lens[pos] = @intCast(code);
            return 1;
        },
        16 => {
            // Copy the previous code length 3 - 6 times.
            // The next 2 bits indicate repeat length
            const n: u8 = @as(u8, try self.takeIntBits(u2)) + 3;
            if (pos == 0 or pos + n > lens.len)
                return error.InvalidDynamicBlockHeader;
            for (0..n) |i| {
                lens[pos + i] = lens[pos + i - 1];
            }
            return n;
        },
        // Repeat a code length of 0 for 3 - 10 times. (3 bits of length)
        17 => return @as(u8, try self.takeIntBits(u3)) + 3,
        // Repeat a code length of 0 for 11 - 138 times (7 bits of length)
        18 => return @as(u8, try self.takeIntBits(u7)) + 11,
        else => return error.InvalidDynamicBlockHeader,
    }
}