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local queue = require "util.queue";
local s_byte, s_sub = string.byte, string.sub;
local dbuffer_methods = {};
local dynamic_buffer_mt = { __index = dbuffer_methods };
function dbuffer_methods:write(data)
if self.max_size and #data + self._length > self.max_size then
return nil;
end
local ok = self.items:push(data);
if not ok then
self:collapse();
ok = self.items:push(data);
end
if not ok then
return nil;
end
self._length = self._length + #data;
return true;
end
function dbuffer_methods:read_chunk(requested_bytes)
local chunk, consumed = self.items:peek(), self.front_consumed;
if not chunk then return; end
local chunk_length = #chunk;
local remaining_chunk_length = chunk_length - consumed;
if not requested_bytes then
requested_bytes = remaining_chunk_length;
end
if remaining_chunk_length <= requested_bytes then
self.front_consumed = 0;
self._length = self._length - remaining_chunk_length;
self.items:pop();
assert(#chunk:sub(consumed + 1, -1) == remaining_chunk_length);
return chunk:sub(consumed + 1, -1), remaining_chunk_length;
end
local end_pos = consumed + requested_bytes;
self.front_consumed = end_pos;
self._length = self._length - requested_bytes;
assert(#chunk:sub(consumed + 1, end_pos) == requested_bytes);
return chunk:sub(consumed + 1, end_pos), requested_bytes;
end
function dbuffer_methods:read(requested_bytes)
local chunks;
if requested_bytes and requested_bytes > self._length then
return nil;
end
local chunk, read_bytes = self:read_chunk(requested_bytes);
if not requested_bytes then
return chunk;
elseif chunk then
requested_bytes = requested_bytes - read_bytes;
if requested_bytes == 0 then -- Already read everything we need
return chunk;
end
chunks = {};
else
return nil;
end
-- Need to keep reading more chunks
while chunk do
table.insert(chunks, chunk);
if requested_bytes > 0 then
chunk, read_bytes = self:read_chunk(requested_bytes);
requested_bytes = requested_bytes - read_bytes;
else
break;
end
end
return table.concat(chunks);
end
function dbuffer_methods:discard(requested_bytes)
if requested_bytes > self._length then
return nil;
end
local chunk, read_bytes = self:read_chunk(requested_bytes);
if chunk then
requested_bytes = requested_bytes - read_bytes;
if requested_bytes == 0 then -- Already read everything we need
return true;
end
else
return nil;
end
while chunk do
if requested_bytes > 0 then
chunk, read_bytes = self:read_chunk(requested_bytes);
requested_bytes = requested_bytes - read_bytes;
else
break;
end
end
return true;
end
-- Normalize i, j into absolute offsets within the
-- front chunk (accounting for front_consumed), and
-- ensure there is enough data in the first chunk
-- to cover any subsequent :sub() or :byte() operation
function dbuffer_methods:_prep_sub(i, j)
if j == nil then
j = -1;
end
if j < 0 then
j = self._length + (j+1);
end
if i < 0 then
i = self._length + (i+1);
end
if i < 1 then
i = 1;
end
if j > self._length then
j = self._length;
end
if i > j then
return nil;
end
self:collapse(j);
if self.front_consumed > 0 then
i = i + self.front_consumed;
j = j + self.front_consumed;
end
return i, j;
end
function dbuffer_methods:sub(i, j)
i, j = self:_prep_sub(i, j);
if not i then
return "";
end
return s_sub(self.items:peek(), i, j);
end
function dbuffer_methods:byte(i, j)
i = i or 1;
j = j or i;
i, j = self:_prep_sub(i, j);
if not i then
return;
end
return s_byte(self.items:peek(), i, j);
end
function dbuffer_methods:length()
return self._length;
end
dbuffer_methods.len = dbuffer_methods.length; -- strings have :len()
dynamic_buffer_mt.__len = dbuffer_methods.length; -- support # operator
function dbuffer_methods:collapse(bytes)
bytes = bytes or self._length;
local front_chunk = self.items:peek();
if not front_chunk or #front_chunk - self.front_consumed >= bytes then
return;
end
local front_chunks = { front_chunk:sub(self.front_consumed+1) };
local front_bytes = #front_chunks[1];
while front_bytes < bytes do
self.items:pop();
local chunk = self.items:peek();
front_bytes = front_bytes + #chunk;
table.insert(front_chunks, chunk);
end
self.items:replace(table.concat(front_chunks));
self.front_consumed = 0;
end
local function new(max_size, max_chunks)
if max_size and max_size <= 0 then
return nil;
end
return setmetatable({
front_consumed = 0;
_length = 0;
max_size = max_size;
items = queue.new(max_chunks or 32);
}, dynamic_buffer_mt);
end
return {
new = new;
};
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