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| 1 | const std = @import("std"); |
| 2 | const io = std.io; |
| 3 | const assert = std.debug.assert; |
| 4 | const testing = std.testing; |
| 5 | |
| 6 | /// BufferedTee provides reader interface to the consumer. Data read by consumer |
| 7 | /// is also written to the output. Output is hold lookahead_size bytes behind |
| 8 | /// consumer. Allowing consumer to put back some bytes to be read again. On flush |
| 9 | /// all consumed bytes are flushed to the output. |
| 10 | /// |
| 11 | /// input -> tee -> consumer |
| 12 | /// | |
| 13 | /// output |
| 14 | /// |
| 15 | /// input - underlying unbuffered reader |
| 16 | /// output - writer, receives data read by consumer |
| 17 | /// consumer - uses provided reader interface |
| 18 | /// |
| 19 | /// If lookahead_size is zero output always has same bytes as consumer. |
| 20 | /// |
| 21 | pub fn BufferedTee( |
| 22 | comptime buffer_size: usize, // internal buffer size in bytes |
| 23 | comptime lookahead_size: usize, // lookahead, number of bytes to hold output behind consumer |
| 24 | comptime InputReaderType: type, |
| 25 | comptime OutputWriterType: type, |
| 26 | ) type { |
| 27 | comptime assert(buffer_size > lookahead_size); |
| 28 | |
| 29 | return struct { |
| 30 | input: InputReaderType, |
| 31 | output: OutputWriterType, |
| 32 | |
| 33 | buf: [buffer_size]u8 = undefined, // internal buffer |
| 34 | tail: usize = 0, // buffer is filled up to this position with bytes from input |
| 35 | rp: usize = 0, // reader pointer; consumer has read up to this position |
| 36 | wp: usize = 0, // writer pointer; data is sent to the output up to this position |
| 37 | |
| 38 | pub const Error = InputReaderType.Error || OutputWriterType.Error; |
| 39 | pub const Reader = io.Reader(*Self, Error, read); |
| 40 | |
| 41 | const Self = @This(); |
| 42 | |
| 43 | pub fn read(self: *Self, dest: []u8) Error!usize { |
| 44 | var dest_index: usize = 0; |
| 45 | |
| 46 | while (dest_index < dest.len) { |
| 47 | const written = @min(dest.len - dest_index, self.tail - self.rp); |
| 48 | if (written == 0) { |
| 49 | try self.preserveLookahead(); |
| 50 | // fill upper part of the buf |
| 51 | const n = try self.input.read(self.buf[self.tail..]); |
| 52 | if (n == 0) { |
| 53 | // reading from the unbuffered stream returned nothing |
| 54 | // so we have nothing left to read. |
| 55 | return dest_index; |
| 56 | } |
| 57 | self.tail += n; |
| 58 | } else { |
| 59 | @memcpy(dest[dest_index..][0..written], self.buf[self.rp..][0..written]); |
| 60 | self.rp += written; |
| 61 | dest_index += written; |
| 62 | try self.flush_(lookahead_size); |
| 63 | } |
| 64 | } |
| 65 | return dest.len; |
| 66 | } |
| 67 | |
| 68 | /// Move lookahead_size bytes to the buffer start. |
| 69 | fn preserveLookahead(self: *Self) !void { |
| 70 | assert(self.tail == self.rp); |
| 71 | if (lookahead_size == 0) { |
| 72 | // Flush is called on each read so wp must follow rp when lookahead_size == 0. |
| 73 | assert(self.wp == self.rp); |
| 74 | // Nothing to preserve rewind pointer to the buffer start |
| 75 | self.rp = 0; |
| 76 | self.wp = 0; |
| 77 | self.tail = 0; |
| 78 | return; |
| 79 | } |
| 80 | if (self.tail <= lookahead_size) { |
| 81 | // There is still palce in the buffer, append to buffer from tail position. |
| 82 | return; |
| 83 | } |
| 84 | try self.flush_(lookahead_size); |
| 85 | const head = self.tail - lookahead_size; |
| 86 | // Preserve head..tail at the start of the buffer. |
| 87 | std.mem.copyForwards(u8, self.buf[0..lookahead_size], self.buf[head..self.tail]); |
| 88 | self.wp -= head; |
| 89 | assert(self.wp <= lookahead_size); |
| 90 | self.rp = lookahead_size; |
| 91 | self.tail = lookahead_size; |
| 92 | } |
| 93 | |
| 94 | /// Flush to the output all but lookahead size bytes. |
| 95 | fn flush_(self: *Self, lookahead: usize) !void { |
| 96 | if (self.rp <= self.wp + lookahead) return; |
| 97 | const new_wp = self.rp - lookahead; |
| 98 | try self.output.writeAll(self.buf[self.wp..new_wp]); |
| 99 | self.wp = new_wp; |
| 100 | } |
| 101 | |
| 102 | /// Flush to the output all consumed bytes. |
| 103 | pub fn flush(self: *Self) !void { |
| 104 | try self.flush_(0); |
| 105 | } |
| 106 | |
| 107 | /// Put back some bytes to be consumed again. Usefull when we overshoot |
| 108 | /// reading and want to return that overshoot bytes. Can return maximum |
| 109 | /// of lookahead_size number of bytes. |
| 110 | pub fn putBack(self: *Self, n: usize) void { |
| 111 | assert(n <= lookahead_size and n <= self.rp); |
| 112 | self.rp -= n; |
| 113 | } |
| 114 | |
| 115 | pub fn reader(self: *Self) Reader { |
| 116 | return .{ .context = self }; |
| 117 | } |
| 118 | }; |
| 119 | } |
| 120 | |
| 121 | pub fn bufferedTee( |
| 122 | comptime buffer_size: usize, |
| 123 | comptime lookahead_size: usize, |
| 124 | input: anytype, |
| 125 | output: anytype, |
| 126 | ) BufferedTee( |
| 127 | buffer_size, |
| 128 | lookahead_size, |
| 129 | @TypeOf(input), |
| 130 | @TypeOf(output), |
| 131 | ) { |
| 132 | return .{ .input = input, .output = output }; |
| 133 | } |
| 134 | |
| 135 | // Running test from std.io.BufferedReader on BufferedTee |
| 136 | // It should act as BufferedReader for consumer. |
| 137 | |
| 138 | fn BufferedReader(comptime buffer_size: usize, comptime ReaderType: type) type { |
| 139 | return BufferedTee(buffer_size, 0, ReaderType, @TypeOf(io.null_writer)); |
| 140 | } |
| 141 | |
| 142 | fn bufferedReader(reader: anytype) BufferedReader(4096, @TypeOf(reader)) { |
| 143 | return .{ |
| 144 | .input = reader, |
| 145 | .output = io.null_writer, |
| 146 | }; |
| 147 | } |
| 148 | |
| 149 | test "io.BufferedTee io.BufferedReader OneByte" { |
| 150 | const OneByteReadReader = struct { |
| 151 | str: []const u8, |
| 152 | curr: usize, |
| 153 | |
| 154 | const Error = error{NoError}; |
| 155 | const Self = @This(); |
| 156 | const Reader = io.Reader(*Self, Error, read); |
| 157 | |
| 158 | fn init(str: []const u8) Self { |
| 159 | return Self{ |
| 160 | .str = str, |
| 161 | .curr = 0, |
| 162 | }; |
| 163 | } |
| 164 | |
| 165 | fn read(self: *Self, dest: []u8) Error!usize { |
| 166 | if (self.str.len <= self.curr or dest.len == 0) |
| 167 | return 0; |
| 168 | |
| 169 | dest[0] = self.str[self.curr]; |
| 170 | self.curr += 1; |
| 171 | return 1; |
| 172 | } |
| 173 | |
| 174 | fn reader(self: *Self) Reader { |
| 175 | return .{ .context = self }; |
| 176 | } |
| 177 | }; |
| 178 | |
| 179 | const str = "This is a test"; |
| 180 | var one_byte_stream = OneByteReadReader.init(str); |
| 181 | var buf_reader = bufferedReader(one_byte_stream.reader()); |
| 182 | const stream = buf_reader.reader(); |
| 183 | |
| 184 | const res = try stream.readAllAlloc(testing.allocator, str.len + 1); |
| 185 | defer testing.allocator.free(res); |
| 186 | try testing.expectEqualSlices(u8, str, res); |
| 187 | } |
| 188 | |
| 189 | test "io.BufferedTee io.BufferedReader Block" { |
| 190 | const BlockReader = struct { |
| 191 | block: []const u8, |
| 192 | reads_allowed: usize, |
| 193 | curr_read: usize, |
| 194 | |
| 195 | const Error = error{NoError}; |
| 196 | const Self = @This(); |
| 197 | const Reader = io.Reader(*Self, Error, read); |
| 198 | |
| 199 | fn init(block: []const u8, reads_allowed: usize) Self { |
| 200 | return Self{ |
| 201 | .block = block, |
| 202 | .reads_allowed = reads_allowed, |
| 203 | .curr_read = 0, |
| 204 | }; |
| 205 | } |
| 206 | |
| 207 | fn read(self: *Self, dest: []u8) Error!usize { |
| 208 | if (self.curr_read >= self.reads_allowed) return 0; |
| 209 | @memcpy(dest[0..self.block.len], self.block); |
| 210 | |
| 211 | self.curr_read += 1; |
| 212 | return self.block.len; |
| 213 | } |
| 214 | |
| 215 | fn reader(self: *Self) Reader { |
| 216 | return .{ .context = self }; |
| 217 | } |
| 218 | }; |
| 219 | |
| 220 | const block = "0123"; |
| 221 | |
| 222 | // len out == block |
| 223 | { |
| 224 | var test_buf_reader: BufferedReader(4, BlockReader) = .{ |
| 225 | .input = BlockReader.init(block, 2), |
| 226 | .output = io.null_writer, |
| 227 | }; |
| 228 | var out_buf: [4]u8 = undefined; |
| 229 | _ = try test_buf_reader.read(&out_buf); |
| 230 | try testing.expectEqualSlices(u8, &out_buf, block); |
| 231 | _ = try test_buf_reader.read(&out_buf); |
| 232 | try testing.expectEqualSlices(u8, &out_buf, block); |
| 233 | try testing.expectEqual(try test_buf_reader.read(&out_buf), 0); |
| 234 | } |
| 235 | |
| 236 | // len out < block |
| 237 | { |
| 238 | var test_buf_reader: BufferedReader(4, BlockReader) = .{ |
| 239 | .input = BlockReader.init(block, 2), |
| 240 | .output = io.null_writer, |
| 241 | }; |
| 242 | var out_buf: [3]u8 = undefined; |
| 243 | _ = try test_buf_reader.read(&out_buf); |
| 244 | try testing.expectEqualSlices(u8, &out_buf, "012"); |
| 245 | _ = try test_buf_reader.read(&out_buf); |
| 246 | try testing.expectEqualSlices(u8, &out_buf, "301"); |
| 247 | const n = try test_buf_reader.read(&out_buf); |
| 248 | try testing.expectEqualSlices(u8, out_buf[0..n], "23"); |
| 249 | try testing.expectEqual(try test_buf_reader.read(&out_buf), 0); |
| 250 | } |
| 251 | |
| 252 | // len out > block |
| 253 | { |
| 254 | var test_buf_reader: BufferedReader(4, BlockReader) = .{ |
| 255 | .input = BlockReader.init(block, 2), |
| 256 | .output = io.null_writer, |
| 257 | }; |
| 258 | var out_buf: [5]u8 = undefined; |
| 259 | _ = try test_buf_reader.read(&out_buf); |
| 260 | try testing.expectEqualSlices(u8, &out_buf, "01230"); |
| 261 | const n = try test_buf_reader.read(&out_buf); |
| 262 | try testing.expectEqualSlices(u8, out_buf[0..n], "123"); |
| 263 | try testing.expectEqual(try test_buf_reader.read(&out_buf), 0); |
| 264 | } |
| 265 | |
| 266 | // len out == 0 |
| 267 | { |
| 268 | var test_buf_reader: BufferedReader(4, BlockReader) = .{ |
| 269 | .input = BlockReader.init(block, 2), |
| 270 | .output = io.null_writer, |
| 271 | }; |
| 272 | var out_buf: [0]u8 = undefined; |
| 273 | _ = try test_buf_reader.read(&out_buf); |
| 274 | try testing.expectEqualSlices(u8, &out_buf, ""); |
| 275 | } |
| 276 | |
| 277 | // len bufreader buf > block |
| 278 | { |
| 279 | var test_buf_reader: BufferedReader(5, BlockReader) = .{ |
| 280 | .input = BlockReader.init(block, 2), |
| 281 | .output = io.null_writer, |
| 282 | }; |
| 283 | var out_buf: [4]u8 = undefined; |
| 284 | _ = try test_buf_reader.read(&out_buf); |
| 285 | try testing.expectEqualSlices(u8, &out_buf, block); |
| 286 | _ = try test_buf_reader.read(&out_buf); |
| 287 | try testing.expectEqualSlices(u8, &out_buf, block); |
| 288 | try testing.expectEqual(try test_buf_reader.read(&out_buf), 0); |
| 289 | } |
| 290 | } |
| 291 | |
| 292 | test "io.BufferedTee with zero lookahead" { |
| 293 | // output has same bytes as consumer |
| 294 | const data = [_]u8{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 } ** 12; |
| 295 | var in = io.fixedBufferStream(&data); |
| 296 | var out = std.ArrayList(u8).init(testing.allocator); |
| 297 | defer out.deinit(); |
| 298 | |
| 299 | var bt = bufferedTee(8, 0, in.reader(), out.writer()); |
| 300 | |
| 301 | var buf: [16]u8 = undefined; |
| 302 | var read_len: usize = 0; |
| 303 | for (0..buf.len) |i| { |
| 304 | const n = try bt.read(buf[0..i]); |
| 305 | try testing.expectEqual(i, n); |
| 306 | read_len += i; |
| 307 | try testing.expectEqual(read_len, out.items.len); |
| 308 | } |
| 309 | } |
| 310 | |
| 311 | test "io.BufferedTee with lookahead" { |
| 312 | // output is lookahead bytes behind consumer |
| 313 | inline for (1..8) |lookahead| { |
| 314 | const data = [_]u8{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 } ** 12; |
| 315 | var in = io.fixedBufferStream(&data); |
| 316 | var out = std.ArrayList(u8).init(testing.allocator); |
| 317 | defer out.deinit(); |
| 318 | |
| 319 | var bt = bufferedTee(8, lookahead, in.reader(), out.writer()); |
| 320 | var buf: [16]u8 = undefined; |
| 321 | |
| 322 | var read_len: usize = 0; |
| 323 | for (1..buf.len) |i| { |
| 324 | const n = try bt.read(buf[0..i]); |
| 325 | try testing.expectEqual(i, n); |
| 326 | read_len += i; |
| 327 | const out_len = if (read_len < lookahead) 0 else read_len - lookahead; |
| 328 | try testing.expectEqual(out_len, out.items.len); |
| 329 | } |
| 330 | try testing.expectEqual(read_len, out.items.len + lookahead); |
| 331 | try bt.flush(); |
| 332 | try testing.expectEqual(read_len, out.items.len); |
| 333 | } |
| 334 | } |
| 335 | |
| 336 | test "io.BufferedTee internal state" { |
| 337 | const data = [_]u8{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 } ** 2; |
| 338 | var in = io.fixedBufferStream(&data); |
| 339 | var out = std.ArrayList(u8).init(testing.allocator); |
| 340 | defer out.deinit(); |
| 341 | |
| 342 | var bt = bufferedTee(8, 4, in.reader(), out.writer()); |
| 343 | |
| 344 | var buf: [16]u8 = undefined; |
| 345 | var n = try bt.read(buf[0..3]); |
| 346 | try testing.expectEqual(3, n); |
| 347 | try testing.expectEqualSlices(u8, data[0..3], buf[0..n]); |
| 348 | try testing.expectEqual(8, bt.tail); |
| 349 | try testing.expectEqual(3, bt.rp); |
| 350 | try testing.expectEqual(0, out.items.len); |
| 351 | |
| 352 | n = try bt.read(buf[0..6]); |
| 353 | try testing.expectEqual(6, n); |
| 354 | try testing.expectEqualSlices(u8, data[3..9], buf[0..n]); |
| 355 | try testing.expectEqual(8, bt.tail); |
| 356 | try testing.expectEqual(5, bt.rp); |
| 357 | try testing.expectEqualSlices(u8, data[4..12], &bt.buf); |
| 358 | try testing.expectEqual(5, out.items.len); |
| 359 | |
| 360 | n = try bt.read(buf[0..9]); |
| 361 | try testing.expectEqual(9, n); |
| 362 | try testing.expectEqualSlices(u8, data[9..18], buf[0..n]); |
| 363 | try testing.expectEqual(8, bt.tail); |
| 364 | try testing.expectEqual(6, bt.rp); |
| 365 | try testing.expectEqualSlices(u8, data[12..20], &bt.buf); |
| 366 | try testing.expectEqual(14, out.items.len); |
| 367 | |
| 368 | try bt.flush(); |
| 369 | try testing.expectEqual(18, out.items.len); |
| 370 | |
| 371 | bt.putBack(4); |
| 372 | n = try bt.read(buf[0..4]); |
| 373 | try testing.expectEqual(4, n); |
| 374 | try testing.expectEqualSlices(u8, data[14..18], buf[0..n]); |
| 375 | |
| 376 | try testing.expectEqual(18, out.items.len); |
| 377 | try bt.flush(); |
| 378 | try testing.expectEqual(18, out.items.len); |
| 379 | } |