struct AccumBuffer [src]

An accumulating buffer for LZ sequences

Fields

buf: ArrayList(u8)Buffer

memlimit: usizeBuffer memory limit

len: usizeTotal number of bytes sent through the buffer

Members

appendByte (Function)
appendLiteral (Function)
appendLz (Function)
deinit (Function)
finish (Function)
init (Function)
lastN (Function)
lastOr (Function)
reset (Function)

Source

  pub const AccumBuffer = struct {
    /// Buffer
    buf: ArrayList(u8),
    /// Buffer memory limit
    memlimit: usize,
    /// Total number of bytes sent through the buffer
    len: usize,

    pub fn init(memlimit: usize) AccumBuffer {
        return .{
            .buf = .{},
            .memlimit = memlimit,
            .len = 0,
        };
    }

    pub fn appendByte(self: *AccumBuffer, allocator: Allocator, byte: u8) !void {
        try self.buf.append(allocator, byte);
        self.len += 1;
    }

    /// Reset the internal dictionary
    pub fn reset(self: *AccumBuffer, writer: *Writer) !void {
        try writer.writeAll(self.buf.items);
        self.buf.clearRetainingCapacity();
        self.len = 0;
    }

    /// Retrieve the last byte or return a default
    pub fn lastOr(self: AccumBuffer, lit: u8) u8 {
        const buf_len = self.buf.items.len;
        return if (buf_len == 0)
            lit
        else
            self.buf.items[buf_len - 1];
    }

    /// Retrieve the n-th last byte
    pub fn lastN(self: AccumBuffer, dist: usize) !u8 {
        const buf_len = self.buf.items.len;
        if (dist > buf_len) {
            return error.CorruptInput;
        }

        return self.buf.items[buf_len - dist];
    }

    /// Append a literal
    pub fn appendLiteral(
        self: *AccumBuffer,
        allocator: Allocator,
        lit: u8,
        writer: *Writer,
    ) !void {
        _ = writer;
        if (self.len >= self.memlimit) {
            return error.CorruptInput;
        }
        try self.buf.append(allocator, lit);
        self.len += 1;
    }

    /// Fetch an LZ sequence (length, distance) from inside the buffer
    pub fn appendLz(
        self: *AccumBuffer,
        allocator: Allocator,
        len: usize,
        dist: usize,
        writer: *Writer,
    ) !void {
        _ = writer;

        const buf_len = self.buf.items.len;
        if (dist > buf_len) return error.CorruptInput;

        try self.buf.ensureUnusedCapacity(allocator, len);
        const buffer = self.buf.allocatedSlice();
        const src = buffer[buf_len - dist ..][0..len];
        const dst = buffer[buf_len..][0..len];

        // This is not a @memmove; it intentionally repeats patterns caused by
        // iterating one byte at a time.
        for (dst, src) |*d, s| d.* = s;

        self.buf.items.len = buf_len + len;
        self.len += len;
    }

    pub fn finish(self: *AccumBuffer, writer: *Writer) !void {
        try writer.writeAll(self.buf.items);
        self.buf.clearRetainingCapacity();
    }

    pub fn deinit(self: *AccumBuffer, allocator: Allocator) void {
        self.buf.deinit(allocator);
        self.* = undefined;
    }
}  