aboutsummaryrefslogtreecommitdiffstats
path: root/util/dbuffer.lua
blob: b148a4a6082fe0022774f6a7c3ca5cffb41f77bf (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
local queue = require "util.queue";

local s_byte, s_sub = string.byte, string.sub;
local dbuffer_methods = {};
local dynamic_buffer_mt = { __name = "dbuffer", __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

-- Read to, and including, the specified character sequence (return nil if not found)
function dbuffer_methods:read_until(char)
	local buffer_pos = 0;
	for i, chunk in self.items:items() do
		local start = 1 + self.front_consumed;
		local char_pos = chunk:find(char, start, true);
		if char_pos then
			return self:read(buffer_pos + (char_pos - start) + #char);
		end
		buffer_pos = buffer_pos + #chunk;
	end
	return nil;
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;
};