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| 1 | //! A set of array and slice types that bit-pack integer elements. A normal [12]u3 |
| 2 | //! takes up 12 bytes of memory since u3's alignment is 1. PackedArray(u3, 12) only |
| 3 | //! takes up 4 bytes of memory. |
| 4 | |
| 5 | const std = @import("std"); |
| 6 | const builtin = @import("builtin"); |
| 7 | const debug = std.debug; |
| 8 | const testing = std.testing; |
| 9 | const native_endian = builtin.target.cpu.arch.endian(); |
| 10 | const Endian = std.builtin.Endian; |
| 11 | |
| 12 | /// Provides a set of functions for reading and writing packed integers from a |
| 13 | /// slice of bytes. |
| 14 | pub fn PackedIntIo(comptime Int: type, comptime endian: Endian) type { |
| 15 | // The general technique employed here is to cast bytes in the array to a container |
| 16 | // integer (having bits % 8 == 0) large enough to contain the number of bits we want, |
| 17 | // then we can retrieve or store the new value with a relative minimum of masking |
| 18 | // and shifting. In this worst case, this means that we'll need an integer that's |
| 19 | // actually 1 byte larger than the minimum required to store the bits, because it |
| 20 | // is possible that the bits start at the end of the first byte, continue through |
| 21 | // zero or more, then end in the beginning of the last. But, if we try to access |
| 22 | // a value in the very last byte of memory with that integer size, that extra byte |
| 23 | // will be out of bounds. Depending on the circumstances of the memory, that might |
| 24 | // mean the OS fatally kills the program. Thus, we use a larger container (MaxIo) |
| 25 | // most of the time, but a smaller container (MinIo) when touching the last byte |
| 26 | // of the memory. |
| 27 | const int_bits = @bitSizeOf(Int); |
| 28 | |
| 29 | // In the best case, this is the number of bytes we need to touch |
| 30 | // to read or write a value, as bits. |
| 31 | const min_io_bits = ((int_bits + 7) / 8) * 8; |
| 32 | |
| 33 | // In the worst case, this is the number of bytes we need to touch |
| 34 | // to read or write a value, as bits. To calculate for int_bits > 1, |
| 35 | // set aside 2 bits to touch the first and last bytes, then divide |
| 36 | // by 8 to see how many bytes can be filled up in between. |
| 37 | const max_io_bits = switch (int_bits) { |
| 38 | 0 => 0, |
| 39 | 1 => 8, |
| 40 | else => ((int_bits - 2) / 8 + 2) * 8, |
| 41 | }; |
| 42 | |
| 43 | // We bitcast the desired Int type to an unsigned version of itself |
| 44 | // to avoid issues with shifting signed ints. |
| 45 | const UnInt = std.meta.Int(.unsigned, int_bits); |
| 46 | |
| 47 | // The maximum container int type |
| 48 | const MinIo = std.meta.Int(.unsigned, min_io_bits); |
| 49 | |
| 50 | // The minimum container int type |
| 51 | const MaxIo = std.meta.Int(.unsigned, max_io_bits); |
| 52 | |
| 53 | return struct { |
| 54 | /// Retrieves the integer at `index` from the packed data beginning at `bit_offset` |
| 55 | /// within `bytes`. |
| 56 | pub fn get(bytes: []const u8, index: usize, bit_offset: u7) Int { |
| 57 | if (int_bits == 0) return 0; |
| 58 | |
| 59 | const bit_index = (index * int_bits) + bit_offset; |
| 60 | const max_end_byte = (bit_index + max_io_bits) / 8; |
| 61 | |
| 62 | //using the larger container size will potentially read out of bounds |
| 63 | if (max_end_byte > bytes.len) return getBits(bytes, MinIo, bit_index); |
| 64 | return getBits(bytes, MaxIo, bit_index); |
| 65 | } |
| 66 | |
| 67 | fn getBits(bytes: []const u8, comptime Container: type, bit_index: usize) Int { |
| 68 | const container_bits = @bitSizeOf(Container); |
| 69 | |
| 70 | const start_byte = bit_index / 8; |
| 71 | const head_keep_bits = bit_index - (start_byte * 8); |
| 72 | const tail_keep_bits = container_bits - (int_bits + head_keep_bits); |
| 73 | |
| 74 | //read bytes as container |
| 75 | const value_ptr: *align(1) const Container = @ptrCast(&bytes[start_byte]); |
| 76 | var value = value_ptr.*; |
| 77 | |
| 78 | if (endian != native_endian) value = @byteSwap(value); |
| 79 | |
| 80 | switch (endian) { |
| 81 | .big => { |
| 82 | value <<= @intCast(head_keep_bits); |
| 83 | value >>= @intCast(head_keep_bits); |
| 84 | value >>= @intCast(tail_keep_bits); |
| 85 | }, |
| 86 | .little => { |
| 87 | value <<= @intCast(tail_keep_bits); |
| 88 | value >>= @intCast(tail_keep_bits); |
| 89 | value >>= @intCast(head_keep_bits); |
| 90 | }, |
| 91 | } |
| 92 | |
| 93 | return @bitCast(@as(UnInt, @truncate(value))); |
| 94 | } |
| 95 | |
| 96 | /// Sets the integer at `index` to `val` within the packed data beginning |
| 97 | /// at `bit_offset` into `bytes`. |
| 98 | pub fn set(bytes: []u8, index: usize, bit_offset: u3, int: Int) void { |
| 99 | if (int_bits == 0) return; |
| 100 | |
| 101 | const bit_index = (index * int_bits) + bit_offset; |
| 102 | const max_end_byte = (bit_index + max_io_bits) / 8; |
| 103 | |
| 104 | //using the larger container size will potentially write out of bounds |
| 105 | if (max_end_byte > bytes.len) return setBits(bytes, MinIo, bit_index, int); |
| 106 | setBits(bytes, MaxIo, bit_index, int); |
| 107 | } |
| 108 | |
| 109 | fn setBits(bytes: []u8, comptime Container: type, bit_index: usize, int: Int) void { |
| 110 | const container_bits = @bitSizeOf(Container); |
| 111 | const Shift = std.math.Log2Int(Container); |
| 112 | |
| 113 | const start_byte = bit_index / 8; |
| 114 | const head_keep_bits = bit_index - (start_byte * 8); |
| 115 | const tail_keep_bits = container_bits - (int_bits + head_keep_bits); |
| 116 | const keep_shift: Shift = switch (endian) { |
| 117 | .big => @intCast(tail_keep_bits), |
| 118 | .little => @intCast(head_keep_bits), |
| 119 | }; |
| 120 | |
| 121 | //position the bits where they need to be in the container |
| 122 | const value = @as(Container, @intCast(@as(UnInt, @bitCast(int)))) << keep_shift; |
| 123 | |
| 124 | //read existing bytes |
| 125 | const target_ptr: *align(1) Container = @ptrCast(&bytes[start_byte]); |
| 126 | var target = target_ptr.*; |
| 127 | |
| 128 | if (endian != native_endian) target = @byteSwap(target); |
| 129 | |
| 130 | //zero the bits we want to replace in the existing bytes |
| 131 | const inv_mask = @as(Container, @intCast(std.math.maxInt(UnInt))) << keep_shift; |
| 132 | const mask = ~inv_mask; |
| 133 | target &= mask; |
| 134 | |
| 135 | //merge the new value |
| 136 | target |= value; |
| 137 | |
| 138 | if (endian != native_endian) target = @byteSwap(target); |
| 139 | |
| 140 | //save it back |
| 141 | target_ptr.* = target; |
| 142 | } |
| 143 | |
| 144 | /// Provides a PackedIntSlice of the packed integers in `bytes` (which begins at `bit_offset`) |
| 145 | /// from the element specified by `start` to the element specified by `end`. |
| 146 | pub fn slice(bytes: []u8, bit_offset: u3, start: usize, end: usize) PackedIntSliceEndian(Int, endian) { |
| 147 | debug.assert(end >= start); |
| 148 | |
| 149 | const length = end - start; |
| 150 | const bit_index = (start * int_bits) + bit_offset; |
| 151 | const start_byte = bit_index / 8; |
| 152 | const end_byte = (bit_index + (length * int_bits) + 7) / 8; |
| 153 | const new_bytes = bytes[start_byte..end_byte]; |
| 154 | |
| 155 | if (length == 0) return PackedIntSliceEndian(Int, endian).init(new_bytes[0..0], 0); |
| 156 | |
| 157 | var new_slice = PackedIntSliceEndian(Int, endian).init(new_bytes, length); |
| 158 | new_slice.bit_offset = @intCast((bit_index - (start_byte * 8))); |
| 159 | return new_slice; |
| 160 | } |
| 161 | |
| 162 | /// Recasts a packed slice to a version with elements of type `NewInt` and endianness `new_endian`. |
| 163 | /// Slice will begin at `bit_offset` within `bytes` and the new length will be automatically |
| 164 | /// calculated from `old_len` using the sizes of the current integer type and `NewInt`. |
| 165 | pub fn sliceCast(bytes: []u8, comptime NewInt: type, comptime new_endian: Endian, bit_offset: u3, old_len: usize) PackedIntSliceEndian(NewInt, new_endian) { |
| 166 | const new_int_bits = @bitSizeOf(NewInt); |
| 167 | const New = PackedIntSliceEndian(NewInt, new_endian); |
| 168 | |
| 169 | const total_bits = (old_len * int_bits); |
| 170 | const new_int_count = total_bits / new_int_bits; |
| 171 | |
| 172 | debug.assert(total_bits == new_int_count * new_int_bits); |
| 173 | |
| 174 | var new = New.init(bytes, new_int_count); |
| 175 | new.bit_offset = bit_offset; |
| 176 | |
| 177 | return new; |
| 178 | } |
| 179 | }; |
| 180 | } |
| 181 | |
| 182 | /// Creates a bit-packed array of `Int`. Non-byte-multiple integers |
| 183 | /// will take up less memory in PackedIntArray than in a normal array. |
| 184 | /// Elements are packed using native endianness and without storing any |
| 185 | /// meta data. PackedArray(i3, 8) will occupy exactly 3 bytes |
| 186 | /// of memory. |
| 187 | pub fn PackedIntArray(comptime Int: type, comptime int_count: usize) type { |
| 188 | return PackedIntArrayEndian(Int, native_endian, int_count); |
| 189 | } |
| 190 | |
| 191 | /// Creates a bit-packed array of `Int` with bit order specified by `endian`. |
| 192 | /// Non-byte-multiple integers will take up less memory in PackedIntArrayEndian |
| 193 | /// than in a normal array. Elements are packed without storing any meta data. |
| 194 | /// PackedIntArrayEndian(i3, 8) will occupy exactly 3 bytes of memory. |
| 195 | pub fn PackedIntArrayEndian(comptime Int: type, comptime endian: Endian, comptime int_count: usize) type { |
| 196 | const int_bits = @bitSizeOf(Int); |
| 197 | const total_bits = int_bits * int_count; |
| 198 | const total_bytes = (total_bits + 7) / 8; |
| 199 | |
| 200 | const Io = PackedIntIo(Int, endian); |
| 201 | |
| 202 | return struct { |
| 203 | const Self = @This(); |
| 204 | |
| 205 | /// The byte buffer containing the packed data. |
| 206 | bytes: [total_bytes]u8, |
| 207 | /// The number of elements in the packed array. |
| 208 | comptime len: usize = int_count, |
| 209 | |
| 210 | /// The integer type of the packed array. |
| 211 | pub const Child = Int; |
| 212 | |
| 213 | /// Initialize a packed array using an unpacked array |
| 214 | /// or, more likely, an array literal. |
| 215 | pub fn init(ints: [int_count]Int) Self { |
| 216 | var self: Self = undefined; |
| 217 | for (ints, 0..) |int, i| self.set(i, int); |
| 218 | return self; |
| 219 | } |
| 220 | |
| 221 | /// Initialize all entries of a packed array to the same value. |
| 222 | pub fn initAllTo(int: Int) Self { |
| 223 | var self: Self = undefined; |
| 224 | self.setAll(int); |
| 225 | return self; |
| 226 | } |
| 227 | |
| 228 | /// Return the integer stored at `index`. |
| 229 | pub fn get(self: Self, index: usize) Int { |
| 230 | debug.assert(index < int_count); |
| 231 | return Io.get(&self.bytes, index, 0); |
| 232 | } |
| 233 | |
| 234 | /// Copy the value of `int` into the array at `index`. |
| 235 | pub fn set(self: *Self, index: usize, int: Int) void { |
| 236 | debug.assert(index < int_count); |
| 237 | return Io.set(&self.bytes, index, 0, int); |
| 238 | } |
| 239 | |
| 240 | /// Set all entries of a packed array to the value of `int`. |
| 241 | pub fn setAll(self: *Self, int: Int) void { |
| 242 | var i: usize = 0; |
| 243 | while (i < int_count) : (i += 1) { |
| 244 | self.set(i, int); |
| 245 | } |
| 246 | } |
| 247 | |
| 248 | /// Create a PackedIntSlice of the array from `start` to `end`. |
| 249 | pub fn slice(self: *Self, start: usize, end: usize) PackedIntSliceEndian(Int, endian) { |
| 250 | debug.assert(start < int_count); |
| 251 | debug.assert(end <= int_count); |
| 252 | return Io.slice(&self.bytes, 0, start, end); |
| 253 | } |
| 254 | |
| 255 | /// Create a PackedIntSlice of the array using `NewInt` as the integer type. |
| 256 | /// `NewInt`'s bit width must fit evenly within the array's `Int`'s total bits. |
| 257 | pub fn sliceCast(self: *Self, comptime NewInt: type) PackedIntSlice(NewInt) { |
| 258 | return self.sliceCastEndian(NewInt, endian); |
| 259 | } |
| 260 | |
| 261 | /// Create a PackedIntSliceEndian of the array using `NewInt` as the integer type |
| 262 | /// and `new_endian` as the new endianness. `NewInt`'s bit width must fit evenly |
| 263 | /// within the array's `Int`'s total bits. |
| 264 | pub fn sliceCastEndian(self: *Self, comptime NewInt: type, comptime new_endian: Endian) PackedIntSliceEndian(NewInt, new_endian) { |
| 265 | return Io.sliceCast(&self.bytes, NewInt, new_endian, 0, int_count); |
| 266 | } |
| 267 | }; |
| 268 | } |
| 269 | |
| 270 | /// A type representing a sub range of a PackedIntArray. |
| 271 | pub fn PackedIntSlice(comptime Int: type) type { |
| 272 | return PackedIntSliceEndian(Int, native_endian); |
| 273 | } |
| 274 | |
| 275 | /// A type representing a sub range of a PackedIntArrayEndian. |
| 276 | pub fn PackedIntSliceEndian(comptime Int: type, comptime endian: Endian) type { |
| 277 | const int_bits = @bitSizeOf(Int); |
| 278 | const Io = PackedIntIo(Int, endian); |
| 279 | |
| 280 | return struct { |
| 281 | const Self = @This(); |
| 282 | |
| 283 | bytes: []u8, |
| 284 | bit_offset: u3, |
| 285 | len: usize, |
| 286 | |
| 287 | /// The integer type of the packed slice. |
| 288 | pub const Child = Int; |
| 289 | |
| 290 | /// Calculates the number of bytes required to store a desired count |
| 291 | /// of `Int`s. |
| 292 | pub fn bytesRequired(int_count: usize) usize { |
| 293 | const total_bits = int_bits * int_count; |
| 294 | const total_bytes = (total_bits + 7) / 8; |
| 295 | return total_bytes; |
| 296 | } |
| 297 | |
| 298 | /// Initialize a packed slice using the memory at `bytes`, with `int_count` |
| 299 | /// elements. `bytes` must be large enough to accommodate the requested |
| 300 | /// count. |
| 301 | pub fn init(bytes: []u8, int_count: usize) Self { |
| 302 | debug.assert(bytes.len >= bytesRequired(int_count)); |
| 303 | |
| 304 | return Self{ |
| 305 | .bytes = bytes, |
| 306 | .len = int_count, |
| 307 | .bit_offset = 0, |
| 308 | }; |
| 309 | } |
| 310 | |
| 311 | /// Return the integer stored at `index`. |
| 312 | pub fn get(self: Self, index: usize) Int { |
| 313 | debug.assert(index < self.len); |
| 314 | return Io.get(self.bytes, index, self.bit_offset); |
| 315 | } |
| 316 | |
| 317 | /// Copy `int` into the slice at `index`. |
| 318 | pub fn set(self: *Self, index: usize, int: Int) void { |
| 319 | debug.assert(index < self.len); |
| 320 | return Io.set(self.bytes, index, self.bit_offset, int); |
| 321 | } |
| 322 | |
| 323 | /// Create a PackedIntSlice of this slice from `start` to `end`. |
| 324 | pub fn slice(self: Self, start: usize, end: usize) PackedIntSliceEndian(Int, endian) { |
| 325 | debug.assert(start < self.len); |
| 326 | debug.assert(end <= self.len); |
| 327 | return Io.slice(self.bytes, self.bit_offset, start, end); |
| 328 | } |
| 329 | |
| 330 | /// Create a PackedIntSlice of the sclice using `NewInt` as the integer type. |
| 331 | /// `NewInt`'s bit width must fit evenly within the slice's `Int`'s total bits. |
| 332 | pub fn sliceCast(self: Self, comptime NewInt: type) PackedIntSliceEndian(NewInt, endian) { |
| 333 | return self.sliceCastEndian(NewInt, endian); |
| 334 | } |
| 335 | |
| 336 | /// Create a PackedIntSliceEndian of the slice using `NewInt` as the integer type |
| 337 | /// and `new_endian` as the new endianness. `NewInt`'s bit width must fit evenly |
| 338 | /// within the slice's `Int`'s total bits. |
| 339 | pub fn sliceCastEndian(self: Self, comptime NewInt: type, comptime new_endian: Endian) PackedIntSliceEndian(NewInt, new_endian) { |
| 340 | return Io.sliceCast(self.bytes, NewInt, new_endian, self.bit_offset, self.len); |
| 341 | } |
| 342 | }; |
| 343 | } |
| 344 | |
| 345 | test "PackedIntArray" { |
| 346 | // TODO @setEvalBranchQuota generates panics in wasm32. Investigate. |
| 347 | if (builtin.target.cpu.arch == .wasm32) return error.SkipZigTest; |
| 348 | |
| 349 | // TODO: enable this test |
| 350 | if (true) return error.SkipZigTest; |
| 351 | |
| 352 | @setEvalBranchQuota(10000); |
| 353 | const max_bits = 256; |
| 354 | const int_count = 19; |
| 355 | |
| 356 | comptime var bits = 0; |
| 357 | inline while (bits <= max_bits) : (bits += 1) { |
| 358 | //alternate unsigned and signed |
| 359 | const sign: std.builtin.Signedness = if (bits % 2 == 0) .signed else .unsigned; |
| 360 | const I = std.meta.Int(sign, bits); |
| 361 | |
| 362 | const PackedArray = PackedIntArray(I, int_count); |
| 363 | const expected_bytes = ((bits * int_count) + 7) / 8; |
| 364 | try testing.expect(@sizeOf(PackedArray) == expected_bytes); |
| 365 | |
| 366 | var data: PackedArray = undefined; |
| 367 | |
| 368 | //write values, counting up |
| 369 | var i: usize = 0; |
| 370 | var count: I = 0; |
| 371 | while (i < data.len) : (i += 1) { |
| 372 | data.set(i, count); |
| 373 | if (bits > 0) count +%= 1; |
| 374 | } |
| 375 | |
| 376 | //read and verify values |
| 377 | i = 0; |
| 378 | count = 0; |
| 379 | while (i < data.len) : (i += 1) { |
| 380 | const val = data.get(i); |
| 381 | try testing.expect(val == count); |
| 382 | if (bits > 0) count +%= 1; |
| 383 | } |
| 384 | } |
| 385 | } |
| 386 | |
| 387 | test "PackedIntIo" { |
| 388 | const bytes = [_]u8{ 0b01101_000, 0b01011_110, 0b00011_101 }; |
| 389 | try testing.expectEqual(@as(u15, 0x2bcd), PackedIntIo(u15, .little).get(&bytes, 0, 3)); |
| 390 | try testing.expectEqual(@as(u16, 0xabcd), PackedIntIo(u16, .little).get(&bytes, 0, 3)); |
| 391 | try testing.expectEqual(@as(u17, 0x1abcd), PackedIntIo(u17, .little).get(&bytes, 0, 3)); |
| 392 | try testing.expectEqual(@as(u18, 0x3abcd), PackedIntIo(u18, .little).get(&bytes, 0, 3)); |
| 393 | } |
| 394 | |
| 395 | test "PackedIntArray init" { |
| 396 | const S = struct { |
| 397 | fn doTheTest() !void { |
| 398 | const PackedArray = PackedIntArray(u3, 8); |
| 399 | var packed_array = PackedArray.init([_]u3{ 0, 1, 2, 3, 4, 5, 6, 7 }); |
| 400 | var i: usize = 0; |
| 401 | while (i < packed_array.len) : (i += 1) try testing.expectEqual(@as(u3, @intCast(i)), packed_array.get(i)); |
| 402 | } |
| 403 | }; |
| 404 | try S.doTheTest(); |
| 405 | try comptime S.doTheTest(); |
| 406 | } |
| 407 | |
| 408 | test "PackedIntArray initAllTo" { |
| 409 | const S = struct { |
| 410 | fn doTheTest() !void { |
| 411 | const PackedArray = PackedIntArray(u3, 8); |
| 412 | var packed_array = PackedArray.initAllTo(5); |
| 413 | var i: usize = 0; |
| 414 | while (i < packed_array.len) : (i += 1) try testing.expectEqual(@as(u3, 5), packed_array.get(i)); |
| 415 | } |
| 416 | }; |
| 417 | try S.doTheTest(); |
| 418 | try comptime S.doTheTest(); |
| 419 | } |
| 420 | |
| 421 | test "PackedIntSlice" { |
| 422 | // TODO @setEvalBranchQuota generates panics in wasm32. Investigate. |
| 423 | if (builtin.target.cpu.arch == .wasm32) return error.SkipZigTest; |
| 424 | |
| 425 | // TODO enable this test |
| 426 | if (true) return error.SkipZigTest; |
| 427 | |
| 428 | @setEvalBranchQuota(10000); |
| 429 | const max_bits = 256; |
| 430 | const int_count = 19; |
| 431 | const total_bits = max_bits * int_count; |
| 432 | const total_bytes = (total_bits + 7) / 8; |
| 433 | |
| 434 | var buffer: [total_bytes]u8 = undefined; |
| 435 | |
| 436 | comptime var bits = 0; |
| 437 | inline while (bits <= max_bits) : (bits += 1) { |
| 438 | //alternate unsigned and signed |
| 439 | const sign: std.builtin.Signedness = if (bits % 2 == 0) .signed else .unsigned; |
| 440 | const I = std.meta.Int(sign, bits); |
| 441 | const P = PackedIntSlice(I); |
| 442 | |
| 443 | var data = P.init(&buffer, int_count); |
| 444 | |
| 445 | //write values, counting up |
| 446 | var i: usize = 0; |
| 447 | var count: I = 0; |
| 448 | while (i < data.len) : (i += 1) { |
| 449 | data.set(i, count); |
| 450 | if (bits > 0) count +%= 1; |
| 451 | } |
| 452 | |
| 453 | //read and verify values |
| 454 | i = 0; |
| 455 | count = 0; |
| 456 | while (i < data.len) : (i += 1) { |
| 457 | const val = data.get(i); |
| 458 | try testing.expect(val == count); |
| 459 | if (bits > 0) count +%= 1; |
| 460 | } |
| 461 | } |
| 462 | } |
| 463 | |
| 464 | test "PackedIntSlice of PackedInt(Array/Slice)" { |
| 465 | // TODO enable this test |
| 466 | if (true) return error.SkipZigTest; |
| 467 | |
| 468 | const max_bits = 16; |
| 469 | const int_count = 19; |
| 470 | |
| 471 | comptime var bits = 0; |
| 472 | inline while (bits <= max_bits) : (bits += 1) { |
| 473 | const Int = std.meta.Int(.unsigned, bits); |
| 474 | |
| 475 | const PackedArray = PackedIntArray(Int, int_count); |
| 476 | var packed_array: PackedArray = undefined; |
| 477 | |
| 478 | const limit = (1 << bits); |
| 479 | |
| 480 | var i: usize = 0; |
| 481 | while (i < packed_array.len) : (i += 1) { |
| 482 | packed_array.set(i, @intCast(i % limit)); |
| 483 | } |
| 484 | |
| 485 | //slice of array |
| 486 | var packed_slice = packed_array.slice(2, 5); |
| 487 | try testing.expect(packed_slice.len == 3); |
| 488 | const ps_bit_count = (bits * packed_slice.len) + packed_slice.bit_offset; |
| 489 | const ps_expected_bytes = (ps_bit_count + 7) / 8; |
| 490 | try testing.expect(packed_slice.bytes.len == ps_expected_bytes); |
| 491 | try testing.expect(packed_slice.get(0) == 2 % limit); |
| 492 | try testing.expect(packed_slice.get(1) == 3 % limit); |
| 493 | try testing.expect(packed_slice.get(2) == 4 % limit); |
| 494 | packed_slice.set(1, 7 % limit); |
| 495 | try testing.expect(packed_slice.get(1) == 7 % limit); |
| 496 | |
| 497 | //write through slice |
| 498 | try testing.expect(packed_array.get(3) == 7 % limit); |
| 499 | |
| 500 | //slice of a slice |
| 501 | const packed_slice_two = packed_slice.slice(0, 3); |
| 502 | try testing.expect(packed_slice_two.len == 3); |
| 503 | const ps2_bit_count = (bits * packed_slice_two.len) + packed_slice_two.bit_offset; |
| 504 | const ps2_expected_bytes = (ps2_bit_count + 7) / 8; |
| 505 | try testing.expect(packed_slice_two.bytes.len == ps2_expected_bytes); |
| 506 | try testing.expect(packed_slice_two.get(1) == 7 % limit); |
| 507 | try testing.expect(packed_slice_two.get(2) == 4 % limit); |
| 508 | |
| 509 | //size one case |
| 510 | const packed_slice_three = packed_slice_two.slice(1, 2); |
| 511 | try testing.expect(packed_slice_three.len == 1); |
| 512 | const ps3_bit_count = (bits * packed_slice_three.len) + packed_slice_three.bit_offset; |
| 513 | const ps3_expected_bytes = (ps3_bit_count + 7) / 8; |
| 514 | try testing.expect(packed_slice_three.bytes.len == ps3_expected_bytes); |
| 515 | try testing.expect(packed_slice_three.get(0) == 7 % limit); |
| 516 | |
| 517 | //empty slice case |
| 518 | const packed_slice_empty = packed_slice.slice(0, 0); |
| 519 | try testing.expect(packed_slice_empty.len == 0); |
| 520 | try testing.expect(packed_slice_empty.bytes.len == 0); |
| 521 | |
| 522 | //slicing at byte boundaries |
| 523 | const packed_slice_edge = packed_array.slice(8, 16); |
| 524 | try testing.expect(packed_slice_edge.len == 8); |
| 525 | const pse_bit_count = (bits * packed_slice_edge.len) + packed_slice_edge.bit_offset; |
| 526 | const pse_expected_bytes = (pse_bit_count + 7) / 8; |
| 527 | try testing.expect(packed_slice_edge.bytes.len == pse_expected_bytes); |
| 528 | try testing.expect(packed_slice_edge.bit_offset == 0); |
| 529 | } |
| 530 | } |
| 531 | |
| 532 | test "PackedIntSlice accumulating bit offsets" { |
| 533 | //bit_offset is u3, so standard debugging asserts should catch |
| 534 | // anything |
| 535 | { |
| 536 | const PackedArray = PackedIntArray(u3, 16); |
| 537 | var packed_array: PackedArray = undefined; |
| 538 | |
| 539 | var packed_slice = packed_array.slice(0, packed_array.len); |
| 540 | var i: usize = 0; |
| 541 | while (i < packed_array.len - 1) : (i += 1) { |
| 542 | packed_slice = packed_slice.slice(1, packed_slice.len); |
| 543 | } |
| 544 | } |
| 545 | { |
| 546 | const PackedArray = PackedIntArray(u11, 88); |
| 547 | var packed_array: PackedArray = undefined; |
| 548 | |
| 549 | var packed_slice = packed_array.slice(0, packed_array.len); |
| 550 | var i: usize = 0; |
| 551 | while (i < packed_array.len - 1) : (i += 1) { |
| 552 | packed_slice = packed_slice.slice(1, packed_slice.len); |
| 553 | } |
| 554 | } |
| 555 | } |
| 556 | |
| 557 | test "PackedInt(Array/Slice) sliceCast" { |
| 558 | const PackedArray = PackedIntArray(u1, 16); |
| 559 | var packed_array = PackedArray.init([_]u1{ 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1 }); |
| 560 | const packed_slice_cast_2 = packed_array.sliceCast(u2); |
| 561 | const packed_slice_cast_4 = packed_slice_cast_2.sliceCast(u4); |
| 562 | var packed_slice_cast_9 = packed_array.slice(0, (packed_array.len / 9) * 9).sliceCast(u9); |
| 563 | const packed_slice_cast_3 = packed_slice_cast_9.sliceCast(u3); |
| 564 | |
| 565 | var i: usize = 0; |
| 566 | while (i < packed_slice_cast_2.len) : (i += 1) { |
| 567 | const val = switch (native_endian) { |
| 568 | .big => 0b01, |
| 569 | .little => 0b10, |
| 570 | }; |
| 571 | try testing.expect(packed_slice_cast_2.get(i) == val); |
| 572 | } |
| 573 | i = 0; |
| 574 | while (i < packed_slice_cast_4.len) : (i += 1) { |
| 575 | const val = switch (native_endian) { |
| 576 | .big => 0b0101, |
| 577 | .little => 0b1010, |
| 578 | }; |
| 579 | try testing.expect(packed_slice_cast_4.get(i) == val); |
| 580 | } |
| 581 | i = 0; |
| 582 | while (i < packed_slice_cast_9.len) : (i += 1) { |
| 583 | const val = 0b010101010; |
| 584 | try testing.expect(packed_slice_cast_9.get(i) == val); |
| 585 | packed_slice_cast_9.set(i, 0b111000111); |
| 586 | } |
| 587 | i = 0; |
| 588 | while (i < packed_slice_cast_3.len) : (i += 1) { |
| 589 | const val: u3 = switch (native_endian) { |
| 590 | .big => if (i % 2 == 0) 0b111 else 0b000, |
| 591 | .little => if (i % 2 == 0) 0b111 else 0b000, |
| 592 | }; |
| 593 | try testing.expect(packed_slice_cast_3.get(i) == val); |
| 594 | } |
| 595 | } |
| 596 | |
| 597 | test "PackedInt(Array/Slice)Endian" { |
| 598 | { |
| 599 | const PackedArrayBe = PackedIntArrayEndian(u4, .big, 8); |
| 600 | var packed_array_be = PackedArrayBe.init([_]u4{ 0, 1, 2, 3, 4, 5, 6, 7 }); |
| 601 | try testing.expect(packed_array_be.bytes[0] == 0b00000001); |
| 602 | try testing.expect(packed_array_be.bytes[1] == 0b00100011); |
| 603 | |
| 604 | var i: usize = 0; |
| 605 | while (i < packed_array_be.len) : (i += 1) { |
| 606 | try testing.expect(packed_array_be.get(i) == i); |
| 607 | } |
| 608 | |
| 609 | var packed_slice_le = packed_array_be.sliceCastEndian(u4, .little); |
| 610 | i = 0; |
| 611 | while (i < packed_slice_le.len) : (i += 1) { |
| 612 | const val = if (i % 2 == 0) i + 1 else i - 1; |
| 613 | try testing.expect(packed_slice_le.get(i) == val); |
| 614 | } |
| 615 | |
| 616 | var packed_slice_le_shift = packed_array_be.slice(1, 5).sliceCastEndian(u4, .little); |
| 617 | i = 0; |
| 618 | while (i < packed_slice_le_shift.len) : (i += 1) { |
| 619 | const val = if (i % 2 == 0) i else i + 2; |
| 620 | try testing.expect(packed_slice_le_shift.get(i) == val); |
| 621 | } |
| 622 | } |
| 623 | |
| 624 | { |
| 625 | const PackedArrayBe = PackedIntArrayEndian(u11, .big, 8); |
| 626 | var packed_array_be = PackedArrayBe.init([_]u11{ 0, 1, 2, 3, 4, 5, 6, 7 }); |
| 627 | try testing.expect(packed_array_be.bytes[0] == 0b00000000); |
| 628 | try testing.expect(packed_array_be.bytes[1] == 0b00000000); |
| 629 | try testing.expect(packed_array_be.bytes[2] == 0b00000100); |
| 630 | try testing.expect(packed_array_be.bytes[3] == 0b00000001); |
| 631 | try testing.expect(packed_array_be.bytes[4] == 0b00000000); |
| 632 | |
| 633 | var i: usize = 0; |
| 634 | while (i < packed_array_be.len) : (i += 1) { |
| 635 | try testing.expect(packed_array_be.get(i) == i); |
| 636 | } |
| 637 | |
| 638 | var packed_slice_le = packed_array_be.sliceCastEndian(u11, .little); |
| 639 | try testing.expect(packed_slice_le.get(0) == 0b00000000000); |
| 640 | try testing.expect(packed_slice_le.get(1) == 0b00010000000); |
| 641 | try testing.expect(packed_slice_le.get(2) == 0b00000000100); |
| 642 | try testing.expect(packed_slice_le.get(3) == 0b00000000000); |
| 643 | try testing.expect(packed_slice_le.get(4) == 0b00010000011); |
| 644 | try testing.expect(packed_slice_le.get(5) == 0b00000000010); |
| 645 | try testing.expect(packed_slice_le.get(6) == 0b10000010000); |
| 646 | try testing.expect(packed_slice_le.get(7) == 0b00000111001); |
| 647 | |
| 648 | var packed_slice_le_shift = packed_array_be.slice(1, 5).sliceCastEndian(u11, .little); |
| 649 | try testing.expect(packed_slice_le_shift.get(0) == 0b00010000000); |
| 650 | try testing.expect(packed_slice_le_shift.get(1) == 0b00000000100); |
| 651 | try testing.expect(packed_slice_le_shift.get(2) == 0b00000000000); |
| 652 | try testing.expect(packed_slice_le_shift.get(3) == 0b00010000011); |
| 653 | } |
| 654 | } |
| 655 | |
| 656 | //@NOTE: Need to manually update this list as more posix os's get |
| 657 | // added to DirectAllocator. |
| 658 | |
| 659 | // These tests prove we aren't accidentally accessing memory past |
| 660 | // the end of the array/slice by placing it at the end of a page |
| 661 | // and reading the last element. The assumption is that the page |
| 662 | // after this one is not mapped and will cause a segfault if we |
| 663 | // don't account for the bounds. |
| 664 | test "PackedIntArray at end of available memory" { |
| 665 | switch (builtin.target.os.tag) { |
| 666 | .linux, .macos, .ios, .freebsd, .netbsd, .openbsd, .windows => {}, |
| 667 | else => return, |
| 668 | } |
| 669 | const PackedArray = PackedIntArray(u3, 8); |
| 670 | |
| 671 | const Padded = struct { |
| 672 | _: [std.mem.page_size - @sizeOf(PackedArray)]u8, |
| 673 | p: PackedArray, |
| 674 | }; |
| 675 | |
| 676 | const allocator = std.testing.allocator; |
| 677 | |
| 678 | var pad = try allocator.create(Padded); |
| 679 | defer allocator.destroy(pad); |
| 680 | pad.p.set(7, std.math.maxInt(u3)); |
| 681 | } |
| 682 | |
| 683 | test "PackedIntSlice at end of available memory" { |
| 684 | switch (builtin.target.os.tag) { |
| 685 | .linux, .macos, .ios, .freebsd, .netbsd, .openbsd, .windows => {}, |
| 686 | else => return, |
| 687 | } |
| 688 | const PackedSlice = PackedIntSlice(u11); |
| 689 | |
| 690 | const allocator = std.testing.allocator; |
| 691 | |
| 692 | var page = try allocator.alloc(u8, std.mem.page_size); |
| 693 | defer allocator.free(page); |
| 694 | |
| 695 | var p = PackedSlice.init(page[std.mem.page_size - 2 ..], 1); |
| 696 | p.set(0, std.math.maxInt(u11)); |
| 697 | } |
Krzysztof Wolicki <der.teufel.mail@gmail.com> 2024-10-12 12:00:09+02:00