Alan Donovan | 312d1a5 | 2017-10-02 10:10:28 -0400 | [diff] [blame^] | 1 | // Copyright 2017 The Bazel Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | // Package skylark provides a Skylark interpreter. |
| 6 | // |
| 7 | // Skylark values are represented by the Value interface. |
| 8 | // The following built-in Value types are known to the evaluator: |
| 9 | // |
| 10 | // NoneType -- NoneType |
| 11 | // Bool -- bool |
| 12 | // Int -- int |
| 13 | // Float -- float |
| 14 | // String -- string |
| 15 | // *List -- list |
| 16 | // Tuple -- tuple |
| 17 | // *Dict -- dict |
| 18 | // *Set -- set |
| 19 | // *Function -- function (implemented in Skylark) |
| 20 | // *Builtin -- builtin (function or method implemented in Go) |
| 21 | // |
| 22 | // Client applications may define new data types that satisfy at least |
| 23 | // the Value interface. Such types may provide additional operations by |
| 24 | // implementing any of these optional interfaces: |
| 25 | // |
| 26 | // Callable -- value is callable like a function |
| 27 | // Comparable -- value defines its own comparison operations |
| 28 | // Iterable -- value is iterable using 'for' loops |
| 29 | // Sequence -- value is iterable sequence of known length |
| 30 | // Indexable -- value is sequence with efficient random access |
| 31 | // HasBinary -- value defines binary operations such as * and + |
| 32 | // HasAttrs -- value has readable fields or methods x.f |
| 33 | // HasSetField -- value has settable fields x.f |
| 34 | // HasSetIndex -- value supports element update using x[i]=y |
| 35 | // |
| 36 | // Client applications may also define domain-specific functions in Go |
| 37 | // and make them available to Skylark programs. Use NewBuiltin to |
| 38 | // construct a built-in value that wraps a Go function. The |
| 39 | // implementation of the Go function may use UnpackArgs to make sense of |
| 40 | // the positional and keyword arguments provided by the caller. |
| 41 | // |
| 42 | // Skylark's None value is not equal to Go's nil, but nil may be |
| 43 | // assigned to a Skylark Value. Be careful to avoid allowing Go nil |
| 44 | // values to leak into Skylark data structures. |
| 45 | // |
| 46 | // The Compare operation requires two arguments of the same |
| 47 | // type, but this constraint cannot be expressed in Go's type system. |
| 48 | // (This is the classic "binary method problem".) |
| 49 | // So, each Value type's CompareSameType method is a partial function |
| 50 | // that compares a value only against others of the same type. |
| 51 | // Use the package's standalone Compare (or Equal) function to compare |
| 52 | // an arbitrary pair of values. |
| 53 | // |
| 54 | // To parse and evaluate a Skylark source file, use ExecFile. The Eval |
| 55 | // function evaluates a single expression. All evaluator functions |
| 56 | // require a Thread parameter which defines the "thread-local storage" |
| 57 | // of a Skylark thread and may be used to plumb application state |
| 58 | // through Sklyark code and into callbacks. When evaluation fails it |
| 59 | // returns an EvalError from which the application may obtain a |
| 60 | // backtrace of active Skylark calls. |
| 61 | // |
| 62 | package skylark |
| 63 | |
| 64 | // This file defines the data types of Skylark and their basic operations. |
| 65 | |
| 66 | import ( |
| 67 | "bytes" |
| 68 | "fmt" |
| 69 | "math" |
| 70 | "math/big" |
| 71 | "reflect" |
| 72 | "strconv" |
| 73 | "strings" |
| 74 | "unicode/utf8" |
| 75 | |
| 76 | "github.com/google/skylark/syntax" |
| 77 | ) |
| 78 | |
| 79 | // Value is a value in the Skylark interpreter. |
| 80 | type Value interface { |
| 81 | // String returns the string representation of the value. |
| 82 | // Skylark string values are quoted as if by Python's repr. |
| 83 | String() string |
| 84 | |
| 85 | // Type returns a short string describing the value's type. |
| 86 | Type() string |
| 87 | |
| 88 | // Freeze causes the value, and all values transitively |
| 89 | // reachable from it through collections and closures, to be |
| 90 | // marked as frozen. All subsequent mutations to the data |
| 91 | // structure through this API will fail dynamically, making the |
| 92 | // data structure immutable and safe for publishing to other |
| 93 | // Skylark interpreters running concurrently. |
| 94 | Freeze() |
| 95 | |
| 96 | // Truth returns the truth value of an object, according to Python rules. |
| 97 | // http://docs.python.org/2/library/stdtypes.html#truth-value-testing |
| 98 | Truth() Bool |
| 99 | |
| 100 | // Hash returns a function of x such that Equals(x, y) => Hash(x) == Hash(y). |
| 101 | // Hash may fail if the value's type is not hashable, or if the value |
| 102 | // contains a non-hashable value. |
| 103 | Hash() (uint32, error) |
| 104 | } |
| 105 | |
| 106 | // A Comparable is a value that defines its own equivalence relation and |
| 107 | // perhaps ordered comparisons. |
| 108 | type Comparable interface { |
| 109 | Value |
| 110 | // CompareSameType compares one value to another of the same Type(). |
| 111 | // The comparison operation must be one of EQL, NEQ, LT, LE, GT, or GE. |
| 112 | // CompareSameType returns an error if an ordered comparison was |
| 113 | // requested for a type that does not support it. |
| 114 | // |
| 115 | // Implementations that recursively compare subcomponents of |
| 116 | // the value should use the CompareDepth function, not Compare, to |
| 117 | // avoid infinite recursion on cyclic structures. |
| 118 | // |
| 119 | // The depth parameter is used to bound comparisons of cyclic |
| 120 | // data structures. Implementations should decrement depth |
| 121 | // before calling CompareDepth and should return an error if depth |
| 122 | // < 1. |
| 123 | // |
| 124 | // Client code should not call this method. Instead, use the |
| 125 | // standalone Compare or Equals functions, which are defined for |
| 126 | // all pairs of operands. |
| 127 | CompareSameType(op syntax.Token, y Value, depth int) (bool, error) |
| 128 | } |
| 129 | |
| 130 | var ( |
| 131 | _ Comparable = None |
| 132 | _ Comparable = Int{} |
| 133 | _ Comparable = False |
| 134 | _ Comparable = Float(0) |
| 135 | _ Comparable = String("") |
| 136 | _ Comparable = (*Dict)(nil) |
| 137 | _ Comparable = (*List)(nil) |
| 138 | _ Comparable = Tuple(nil) |
| 139 | _ Comparable = (*Set)(nil) |
| 140 | ) |
| 141 | |
| 142 | // A Callable value f may be the operand of a function call, f(x). |
| 143 | type Callable interface { |
| 144 | Value |
| 145 | Name() string |
| 146 | Call(thread *Thread, args Tuple, kwargs []Tuple) (Value, error) |
| 147 | } |
| 148 | |
| 149 | var ( |
| 150 | _ Callable = (*Builtin)(nil) |
| 151 | _ Callable = (*Function)(nil) |
| 152 | ) |
| 153 | |
| 154 | // An Iterable abstracts a sequence of values. |
| 155 | // An iterable value may be iterated over by a 'for' loop or used where |
| 156 | // any other Skylark iterable is allowed. Unlike a Sequence, the length |
| 157 | // of an Iterable is not necessarily known in advance of iteration. |
| 158 | type Iterable interface { |
| 159 | Value |
| 160 | Iterate() Iterator // must be followed by call to Iterator.Done |
| 161 | } |
| 162 | |
| 163 | // A Sequence is a sequence of values of known length. |
| 164 | type Sequence interface { |
| 165 | Iterable |
| 166 | Len() int |
| 167 | } |
| 168 | |
| 169 | var ( |
| 170 | _ Sequence = (*Dict)(nil) |
| 171 | _ Sequence = (*Set)(nil) |
| 172 | ) |
| 173 | |
| 174 | // An Indexable is a sequence of known length that supports efficient random access. |
| 175 | // It is not necessarily iterable. |
| 176 | type Indexable interface { |
| 177 | Value |
| 178 | Index(i int) Value // requires 0 <= i < Len() |
| 179 | Len() int |
| 180 | } |
| 181 | |
| 182 | // A HasSetIndex is an Indexable value whose elements may be assigned (x[i] = y). |
| 183 | // |
| 184 | // The implementation should not add Len to a negative index as the |
| 185 | // evaluator does this before the call. |
| 186 | type HasSetIndex interface { |
| 187 | Indexable |
| 188 | SetIndex(index int, v Value) error |
| 189 | } |
| 190 | |
| 191 | var ( |
| 192 | _ HasSetIndex = (*List)(nil) |
| 193 | _ Indexable = Tuple(nil) |
| 194 | _ Indexable = String("") |
| 195 | ) |
| 196 | |
| 197 | // An Iterator provides a sequence of values to the caller. |
| 198 | // |
| 199 | // The caller must call Done when the iterator is no longer needed. |
| 200 | // Operations that modify a sequence will fail if it has active iterators. |
| 201 | // |
| 202 | // Example usage: |
| 203 | // |
| 204 | // iter := iterable.Iterator() |
| 205 | // defer iter.Done() |
| 206 | // var x Value |
| 207 | // for iter.Next(&x) { |
| 208 | // ... |
| 209 | // } |
| 210 | // |
| 211 | type Iterator interface { |
| 212 | // If the iterator is exhausted, Next returns false. |
| 213 | // Otherwise it sets *p to the current element of the sequence, |
| 214 | // advances the iterator, and returns true. |
| 215 | Next(p *Value) bool |
| 216 | Done() |
| 217 | } |
| 218 | |
| 219 | // An Mapping is a mapping from keys to values, such as a dictionary. |
| 220 | type Mapping interface { |
| 221 | Value |
| 222 | // Get returns the value corresponding to the specified key, |
| 223 | // or !found if the mapping does not contain the key. |
| 224 | Get(Value) (v Value, found bool, err error) |
| 225 | } |
| 226 | |
| 227 | var _ Mapping = (*Dict)(nil) |
| 228 | |
| 229 | // A HasBinary value may be used as either operand of these binary operators: |
| 230 | // + - * / % in not in | & |
| 231 | // The Side argument indicates whether the receiver is the left or right operand. |
| 232 | // |
| 233 | // An implementation may decline to handle an operation by returning (nil, nil). |
| 234 | // For this reason, clients should always call the standalone Binary(op, x, y) |
| 235 | // function rather than calling the method directly. |
| 236 | type HasBinary interface { |
| 237 | Value |
| 238 | Binary(op syntax.Token, y Value, side Side) (Value, error) |
| 239 | } |
| 240 | |
| 241 | type Side bool |
| 242 | |
| 243 | const ( |
| 244 | Left Side = false |
| 245 | Right Side = true |
| 246 | ) |
| 247 | |
| 248 | // A HasAttrs value has fields or methods that may be read by a dot expression (y = x.f). |
| 249 | // Attribute names may be listed using the built-in 'dir' function. |
| 250 | // |
| 251 | // For implementation convenience, a result of (nil, nil) from Attr is |
| 252 | // interpreted as a "no such field or method" error. Implementations are |
| 253 | // free to return a more precise error. |
| 254 | type HasAttrs interface { |
| 255 | Value |
| 256 | Attr(name string) (Value, error) // returns (nil, nil) if attribute not present |
| 257 | AttrNames() []string // callers must not modify the result. |
| 258 | } |
| 259 | |
| 260 | var ( |
| 261 | _ HasAttrs = String("") |
| 262 | _ HasAttrs = new(List) |
| 263 | _ HasAttrs = new(Dict) |
| 264 | _ HasAttrs = new(Set) |
| 265 | ) |
| 266 | |
| 267 | // A HasSetField value has fields that may be written by a dot expression (x.f = y). |
| 268 | type HasSetField interface { |
| 269 | HasAttrs |
| 270 | SetField(name string, val Value) error |
| 271 | } |
| 272 | |
| 273 | // NoneType is the type of None. Its only legal value is None. |
| 274 | // (We represent it as a number, not struct{}, so that None may be constant.) |
| 275 | type NoneType byte |
| 276 | |
| 277 | const None = NoneType(0) |
| 278 | |
| 279 | func (NoneType) String() string { return "None" } |
| 280 | func (NoneType) Type() string { return "NoneType" } |
| 281 | func (NoneType) Freeze() {} // immutable |
| 282 | func (NoneType) Truth() Bool { return False } |
| 283 | func (NoneType) Hash() (uint32, error) { return 0, nil } |
| 284 | func (NoneType) CompareSameType(op syntax.Token, y Value, depth int) (bool, error) { |
| 285 | return threeway(op, 0), nil |
| 286 | } |
| 287 | |
| 288 | // Bool is the type of a Skylark bool. |
| 289 | type Bool bool |
| 290 | |
| 291 | const ( |
| 292 | False Bool = false |
| 293 | True Bool = true |
| 294 | ) |
| 295 | |
| 296 | func (b Bool) String() string { |
| 297 | if b { |
| 298 | return "True" |
| 299 | } else { |
| 300 | return "False" |
| 301 | } |
| 302 | } |
| 303 | func (b Bool) Type() string { return "bool" } |
| 304 | func (b Bool) Freeze() {} // immutable |
| 305 | func (b Bool) Truth() Bool { return b } |
| 306 | func (b Bool) Hash() (uint32, error) { return uint32(b2i(bool(b))), nil } |
| 307 | func (x Bool) CompareSameType(op syntax.Token, y_ Value, depth int) (bool, error) { |
| 308 | y := y_.(Bool) |
| 309 | return threeway(op, b2i(bool(x))-b2i(bool(y))), nil |
| 310 | } |
| 311 | |
| 312 | // Float is the type of a Skylark float. |
| 313 | type Float float64 |
| 314 | |
| 315 | func (f Float) String() string { return strconv.FormatFloat(float64(f), 'g', 6, 64) } |
| 316 | func (f Float) Type() string { return "float" } |
| 317 | func (f Float) Freeze() {} // immutable |
| 318 | func (f Float) Truth() Bool { return f != 0.0 } |
| 319 | func (f Float) Hash() (uint32, error) { |
| 320 | // Equal float and int values must yield the same hash. |
| 321 | // TODO(adonovan): opt: if f is non-integral, and thus not equal |
| 322 | // to any Int, we can avoid the Int conversion and use a cheaper hash. |
| 323 | if isFinite(float64(f)) { |
| 324 | return finiteFloatToInt(f).Hash() |
| 325 | } |
| 326 | return 1618033, nil // NaN, +/-Inf |
| 327 | } |
| 328 | |
| 329 | func floor(f Float) Float { return Float(math.Floor(float64(f))) } |
| 330 | |
| 331 | // isFinite reports whether f represents a finite rational value. |
| 332 | // It is equivalent to !math.IsNan(f) && !math.IsInf(f, 0). |
| 333 | func isFinite(f float64) bool { |
| 334 | return math.Abs(f) <= math.MaxFloat64 |
| 335 | } |
| 336 | |
| 337 | func (x Float) CompareSameType(op syntax.Token, y_ Value, depth int) (bool, error) { |
| 338 | y := y_.(Float) |
| 339 | switch op { |
| 340 | case syntax.EQL: |
| 341 | return x == y, nil |
| 342 | case syntax.NEQ: |
| 343 | return x != y, nil |
| 344 | case syntax.LE: |
| 345 | return x <= y, nil |
| 346 | case syntax.LT: |
| 347 | return x < y, nil |
| 348 | case syntax.GE: |
| 349 | return x >= y, nil |
| 350 | case syntax.GT: |
| 351 | return x > y, nil |
| 352 | } |
| 353 | panic(op) |
| 354 | } |
| 355 | |
| 356 | func (f Float) rational() *big.Rat { return new(big.Rat).SetFloat64(float64(f)) } |
| 357 | |
| 358 | // AsFloat returns the float64 value closest to x. |
| 359 | // The f result is undefined if x is not a float or int. |
| 360 | func AsFloat(x Value) (f float64, ok bool) { |
| 361 | switch x := x.(type) { |
| 362 | case Float: |
| 363 | return float64(x), true |
| 364 | case Int: |
| 365 | return float64(x.Float()), true |
| 366 | } |
| 367 | return 0, false |
| 368 | } |
| 369 | |
| 370 | func (x Float) Mod(y Float) Float { return Float(math.Mod(float64(x), float64(y))) } |
| 371 | |
| 372 | // String is the type of a Skylark string. |
| 373 | // |
| 374 | // A String is an immutable sequence of bytes. Strings are iterable; |
| 375 | // iteration over a string yields each of its 1-byte substrings in order. |
| 376 | type String string |
| 377 | |
| 378 | func (s String) String() string { return strconv.Quote(string(s)) } |
| 379 | func (s String) Type() string { return "string" } |
| 380 | func (s String) Freeze() {} // immutable |
| 381 | func (s String) Truth() Bool { return len(s) > 0 } |
| 382 | func (s String) Hash() (uint32, error) { return hashString(string(s)), nil } |
| 383 | func (s String) Len() int { return len(s) } // bytes |
| 384 | func (s String) Index(i int) Value { return s[i : i+1] } |
| 385 | |
| 386 | func (s String) Attr(name string) (Value, error) { return builtinAttr(s, name, stringMethods) } |
| 387 | func (s String) AttrNames() []string { return builtinAttrNames(stringMethods) } |
| 388 | |
| 389 | func (x String) CompareSameType(op syntax.Token, y_ Value, depth int) (bool, error) { |
| 390 | y := y_.(String) |
| 391 | return threeway(op, strings.Compare(string(x), string(y))), nil |
| 392 | } |
| 393 | |
| 394 | func AsString(x Value) (string, bool) { v, ok := x.(String); return string(v), ok } |
| 395 | |
| 396 | // A stringIterable is an iterable whose iterator yields a sequence of |
| 397 | // either Unicode code points or bytes, |
| 398 | // either numerically or as successive substrings. |
| 399 | type stringIterable struct { |
| 400 | s String |
| 401 | split bool |
| 402 | codepoints bool |
| 403 | } |
| 404 | |
| 405 | var _ Iterable = (*stringIterable)(nil) |
| 406 | |
| 407 | func (si stringIterable) String() string { |
| 408 | if si.split { |
| 409 | return si.s.String() + ".split_" + si.Type() + "()" |
| 410 | } else { |
| 411 | return si.s.String() + "." + si.Type() + "()" |
| 412 | } |
| 413 | } |
| 414 | func (si stringIterable) Type() string { |
| 415 | if si.codepoints { |
| 416 | return "codepoints" |
| 417 | } else { |
| 418 | return "bytes" |
| 419 | } |
| 420 | } |
| 421 | func (si stringIterable) Freeze() {} // immutable |
| 422 | func (si stringIterable) Truth() Bool { return True } |
| 423 | func (si stringIterable) Hash() (uint32, error) { return 0, fmt.Errorf("unhashable: %s", si.Type()) } |
| 424 | func (si stringIterable) Iterate() Iterator { return &stringIterator{si, 0} } |
| 425 | |
| 426 | type stringIterator struct { |
| 427 | si stringIterable |
| 428 | i int |
| 429 | } |
| 430 | |
| 431 | func (it *stringIterator) Next(p *Value) bool { |
| 432 | s := it.si.s[it.i:] |
| 433 | if s == "" { |
| 434 | return false |
| 435 | } |
| 436 | if it.si.codepoints { |
| 437 | r, sz := utf8.DecodeRuneInString(string(s)) |
| 438 | if it.si.split { |
| 439 | *p = s[:sz] |
| 440 | } else { |
| 441 | *p = MakeInt(int(r)) |
| 442 | } |
| 443 | it.i += sz |
| 444 | } else { |
| 445 | b := int(s[0]) |
| 446 | if it.si.split { |
| 447 | *p = s[:1] |
| 448 | } else { |
| 449 | *p = MakeInt(b) |
| 450 | } |
| 451 | it.i += 1 |
| 452 | } |
| 453 | return true |
| 454 | } |
| 455 | |
| 456 | func (*stringIterator) Done() {} |
| 457 | |
| 458 | // A Function is a function defined by a Skylark def statement. |
| 459 | type Function struct { |
| 460 | name string // "lambda" for anonymous functions |
| 461 | position syntax.Position // position of def or lambda token |
| 462 | syntax *syntax.Function |
| 463 | globals StringDict |
| 464 | defaults Tuple |
| 465 | freevars Tuple |
| 466 | } |
| 467 | |
| 468 | func (fn *Function) Name() string { return fn.name } |
| 469 | func (fn *Function) Hash() (uint32, error) { return hashString(fn.name), nil } |
| 470 | func (fn *Function) Freeze() { fn.defaults.Freeze(); fn.freevars.Freeze() } |
| 471 | func (fn *Function) String() string { return toString(fn) } |
| 472 | func (fn *Function) Type() string { return "function" } |
| 473 | func (fn *Function) Truth() Bool { return true } |
| 474 | |
| 475 | func (fn *Function) Syntax() *syntax.Function { return fn.syntax } |
| 476 | |
| 477 | // A Builtin is a function implemented in Go. |
| 478 | type Builtin struct { |
| 479 | name string |
| 480 | fn func(thread *Thread, fn *Builtin, args Tuple, kwargs []Tuple) (Value, error) |
| 481 | recv Value // for bound methods (e.g. "".startswith) |
| 482 | } |
| 483 | |
| 484 | func (b *Builtin) Name() string { return b.name } |
| 485 | func (b *Builtin) Freeze() { |
| 486 | if b.recv != nil { |
| 487 | b.recv.Freeze() |
| 488 | } |
| 489 | } |
| 490 | func (b *Builtin) Hash() (uint32, error) { |
| 491 | h := hashString(b.name) |
| 492 | if b.recv != nil { |
| 493 | h ^= 5521 |
| 494 | } |
| 495 | return h, nil |
| 496 | } |
| 497 | func (b *Builtin) Receiver() Value { return b.recv } |
| 498 | func (b *Builtin) String() string { return toString(b) } |
| 499 | func (b *Builtin) Type() string { return "builtin" } |
| 500 | func (b *Builtin) Call(thread *Thread, args Tuple, kwargs []Tuple) (Value, error) { |
| 501 | return b.fn(thread, b, args, kwargs) |
| 502 | } |
| 503 | func (b *Builtin) Truth() Bool { return true } |
| 504 | |
| 505 | // NewBuiltin returns a new 'builtin' value with the specified name |
| 506 | // and implementation. It compares unequal with all other values. |
| 507 | func NewBuiltin(name string, fn func(thread *Thread, fn *Builtin, args Tuple, kwargs []Tuple) (Value, error)) *Builtin { |
| 508 | return &Builtin{name: name, fn: fn} |
| 509 | } |
| 510 | |
| 511 | // BindReceiver returns a new Builtin value representing a method |
| 512 | // closure, that is, a built-in function bound to a receiver value. |
| 513 | // |
| 514 | // In the example below, the value of f is the string.index builtin bound to |
| 515 | // the receiver value "abc": |
| 516 | // |
| 517 | // f = "abc".index; f("a"); f("b") |
| 518 | // |
| 519 | // In the common case, the receiver is bound only during the call, |
| 520 | // but this still results in the creation of a temporary method closure: |
| 521 | // |
| 522 | // "abc".index("a") |
| 523 | // |
| 524 | func (b *Builtin) BindReceiver(recv Value) *Builtin { |
| 525 | return &Builtin{name: b.name, fn: b.fn, recv: recv} |
| 526 | } |
| 527 | |
| 528 | // A *Dict represents a Skylark dictionary. |
| 529 | type Dict struct { |
| 530 | ht hashtable |
| 531 | } |
| 532 | |
| 533 | func (d *Dict) Clear() error { return d.ht.clear() } |
| 534 | func (d *Dict) Delete(k Value) (v Value, found bool, err error) { return d.ht.delete(k) } |
| 535 | func (d *Dict) Get(k Value) (v Value, found bool, err error) { return d.ht.lookup(k) } |
| 536 | func (d *Dict) Items() []Tuple { return d.ht.items() } |
| 537 | func (d *Dict) Keys() []Value { return d.ht.keys() } |
| 538 | func (d *Dict) Len() int { return int(d.ht.len) } |
| 539 | func (d *Dict) Iterate() Iterator { return d.ht.iterate() } |
| 540 | func (d *Dict) Set(k, v Value) error { return d.ht.insert(k, v) } |
| 541 | func (d *Dict) String() string { return toString(d) } |
| 542 | func (d *Dict) Type() string { return "dict" } |
| 543 | func (d *Dict) Freeze() { d.ht.freeze() } |
| 544 | func (d *Dict) Truth() Bool { return d.Len() > 0 } |
| 545 | func (d *Dict) Hash() (uint32, error) { return 0, fmt.Errorf("unhashable type: dict") } |
| 546 | |
| 547 | func (d *Dict) Attr(name string) (Value, error) { return builtinAttr(d, name, dictMethods) } |
| 548 | func (d *Dict) AttrNames() []string { return builtinAttrNames(dictMethods) } |
| 549 | |
| 550 | func (x *Dict) CompareSameType(op syntax.Token, y_ Value, depth int) (bool, error) { |
| 551 | y := y_.(*Dict) |
| 552 | switch op { |
| 553 | case syntax.EQL: |
| 554 | ok, err := dictsEqual(x, y, depth) |
| 555 | return ok, err |
| 556 | case syntax.NEQ: |
| 557 | ok, err := dictsEqual(x, y, depth) |
| 558 | return !ok, err |
| 559 | default: |
| 560 | return false, fmt.Errorf("%s %s %s not implemented", x.Type(), op, y.Type()) |
| 561 | } |
| 562 | } |
| 563 | |
| 564 | func dictsEqual(x, y *Dict, depth int) (bool, error) { |
| 565 | if x.Len() != y.Len() { |
| 566 | return false, nil |
| 567 | } |
| 568 | for _, xitem := range x.Items() { |
| 569 | key, xval := xitem[0], xitem[1] |
| 570 | |
| 571 | if yval, found, _ := y.Get(key); !found { |
| 572 | return false, nil |
| 573 | } else if eq, err := EqualDepth(xval, yval, depth-1); err != nil { |
| 574 | return false, err |
| 575 | } else if !eq { |
| 576 | return false, nil |
| 577 | } |
| 578 | } |
| 579 | return true, nil |
| 580 | } |
| 581 | |
| 582 | // A *List represents a Skylark list value. |
| 583 | type List struct { |
| 584 | elems []Value |
| 585 | frozen bool |
| 586 | itercount uint32 // number of active iterators (ignored if frozen) |
| 587 | } |
| 588 | |
| 589 | // NewList returns a list containing the specified elements. |
| 590 | // Callers should not subsequently modify elems. |
| 591 | func NewList(elems []Value) *List { return &List{elems: elems} } |
| 592 | |
| 593 | func (l *List) Freeze() { |
| 594 | if !l.frozen { |
| 595 | l.frozen = true |
| 596 | for _, elem := range l.elems { |
| 597 | elem.Freeze() |
| 598 | } |
| 599 | } |
| 600 | } |
| 601 | |
| 602 | // checkMutable reports an error if the list should not be mutated. |
| 603 | // verb+" list" should describe the operation. |
| 604 | // Structural mutations are not permitted during iteration. |
| 605 | func (l *List) checkMutable(verb string, structural bool) error { |
| 606 | if l.frozen { |
| 607 | return fmt.Errorf("cannot %s frozen list", verb) |
| 608 | } |
| 609 | if structural && l.itercount > 0 { |
| 610 | return fmt.Errorf("cannot %s list during iteration", verb) |
| 611 | } |
| 612 | return nil |
| 613 | } |
| 614 | |
| 615 | func (l *List) String() string { return toString(l) } |
| 616 | func (l *List) Type() string { return "list" } |
| 617 | func (l *List) Hash() (uint32, error) { return 0, fmt.Errorf("unhashable type: list") } |
| 618 | func (l *List) Truth() Bool { return l.Len() > 0 } |
| 619 | func (l *List) Len() int { return len(l.elems) } |
| 620 | func (l *List) Index(i int) Value { return l.elems[i] } |
| 621 | |
| 622 | func (l *List) Attr(name string) (Value, error) { return builtinAttr(l, name, listMethods) } |
| 623 | func (l *List) AttrNames() []string { return builtinAttrNames(listMethods) } |
| 624 | |
| 625 | func (l *List) Iterate() Iterator { |
| 626 | if !l.frozen { |
| 627 | l.itercount++ |
| 628 | } |
| 629 | return &listIterator{l: l} |
| 630 | } |
| 631 | |
| 632 | func (x *List) CompareSameType(op syntax.Token, y_ Value, depth int) (bool, error) { |
| 633 | y := y_.(*List) |
| 634 | // It's tempting to check x == y as an optimization here, |
| 635 | // but wrong because a list containing NaN is not equal to itself. |
| 636 | return sliceCompare(op, x.elems, y.elems, depth) |
| 637 | } |
| 638 | |
| 639 | func sliceCompare(op syntax.Token, x, y []Value, depth int) (bool, error) { |
| 640 | // Fast path: check length. |
| 641 | if len(x) != len(y) && (op == syntax.EQL || op == syntax.NEQ) { |
| 642 | return op == syntax.NEQ, nil |
| 643 | } |
| 644 | |
| 645 | // Find first element that is not equal in both lists. |
| 646 | for i := 0; i < len(x) && i < len(y); i++ { |
| 647 | if eq, err := EqualDepth(x[i], y[i], depth-1); err != nil { |
| 648 | return false, err |
| 649 | } else if !eq { |
| 650 | switch op { |
| 651 | case syntax.EQL: |
| 652 | return false, nil |
| 653 | case syntax.NEQ: |
| 654 | return true, nil |
| 655 | default: |
| 656 | return CompareDepth(op, x[i], y[i], depth-1) |
| 657 | } |
| 658 | } |
| 659 | } |
| 660 | |
| 661 | return threeway(op, len(x)-len(y)), nil |
| 662 | } |
| 663 | |
| 664 | type listIterator struct { |
| 665 | l *List |
| 666 | i int |
| 667 | } |
| 668 | |
| 669 | func (it *listIterator) Next(p *Value) bool { |
| 670 | if it.i < it.l.Len() { |
| 671 | *p = it.l.elems[it.i] |
| 672 | it.i++ |
| 673 | return true |
| 674 | } |
| 675 | return false |
| 676 | } |
| 677 | |
| 678 | func (it *listIterator) Done() { |
| 679 | if !it.l.frozen { |
| 680 | it.l.itercount-- |
| 681 | } |
| 682 | } |
| 683 | |
| 684 | func (l *List) SetIndex(i int, v Value) error { |
| 685 | if err := l.checkMutable("assign to element of", false); err != nil { |
| 686 | return err |
| 687 | } |
| 688 | l.elems[i] = v |
| 689 | return nil |
| 690 | } |
| 691 | |
| 692 | func (l *List) Append(v Value) error { |
| 693 | if err := l.checkMutable("append to", true); err != nil { |
| 694 | return err |
| 695 | } |
| 696 | l.elems = append(l.elems, v) |
| 697 | return nil |
| 698 | } |
| 699 | |
| 700 | func (l *List) Clear() error { |
| 701 | if err := l.checkMutable("clear", true); err != nil { |
| 702 | return err |
| 703 | } |
| 704 | for i := range l.elems { |
| 705 | l.elems[i] = nil // aid GC |
| 706 | } |
| 707 | l.elems = l.elems[:0] |
| 708 | return nil |
| 709 | } |
| 710 | |
| 711 | // A Tuple represents a Skylark tuple value. |
| 712 | type Tuple []Value |
| 713 | |
| 714 | func (t Tuple) Len() int { return len(t) } |
| 715 | func (t Tuple) Index(i int) Value { return t[i] } |
| 716 | func (t Tuple) Iterate() Iterator { return &tupleIterator{elems: t} } |
| 717 | func (t Tuple) Freeze() { |
| 718 | for _, elem := range t { |
| 719 | elem.Freeze() |
| 720 | } |
| 721 | } |
| 722 | func (t Tuple) String() string { return toString(t) } |
| 723 | func (t Tuple) Type() string { return "tuple" } |
| 724 | func (t Tuple) Truth() Bool { return len(t) > 0 } |
| 725 | |
| 726 | func (x Tuple) CompareSameType(op syntax.Token, y_ Value, depth int) (bool, error) { |
| 727 | y := y_.(Tuple) |
| 728 | return sliceCompare(op, x, y, depth) |
| 729 | } |
| 730 | |
| 731 | func (t Tuple) Hash() (uint32, error) { |
| 732 | // Use same algorithm as Python. |
| 733 | var x, mult uint32 = 0x345678, 1000003 |
| 734 | for _, elem := range t { |
| 735 | y, err := elem.Hash() |
| 736 | if err != nil { |
| 737 | return 0, err |
| 738 | } |
| 739 | x = x ^ y*mult |
| 740 | mult += 82520 + uint32(len(t)+len(t)) |
| 741 | } |
| 742 | return x, nil |
| 743 | } |
| 744 | |
| 745 | type tupleIterator struct{ elems Tuple } |
| 746 | |
| 747 | func (it *tupleIterator) Next(p *Value) bool { |
| 748 | if len(it.elems) > 0 { |
| 749 | *p = it.elems[0] |
| 750 | it.elems = it.elems[1:] |
| 751 | return true |
| 752 | } |
| 753 | return false |
| 754 | } |
| 755 | |
| 756 | func (it *tupleIterator) Done() {} |
| 757 | |
| 758 | // A Set represents a Skylark set value. |
| 759 | type Set struct { |
| 760 | ht hashtable // values are all None |
| 761 | } |
| 762 | |
| 763 | func (s *Set) Delete(k Value) (found bool, err error) { _, found, err = s.ht.delete(k); return } |
| 764 | func (s *Set) Clear() error { return s.ht.clear() } |
| 765 | func (s *Set) Has(k Value) (found bool, err error) { _, found, err = s.ht.lookup(k); return } |
| 766 | func (s *Set) Insert(k Value) error { return s.ht.insert(k, None) } |
| 767 | func (s *Set) Len() int { return int(s.ht.len) } |
| 768 | func (s *Set) Iterate() Iterator { return s.ht.iterate() } |
| 769 | func (s *Set) String() string { return toString(s) } |
| 770 | func (s *Set) Type() string { return "set" } |
| 771 | func (s *Set) elems() []Value { return s.ht.keys() } |
| 772 | func (s *Set) Freeze() { s.ht.freeze() } |
| 773 | func (s *Set) Hash() (uint32, error) { return 0, fmt.Errorf("unhashable type: set") } |
| 774 | func (s *Set) Truth() Bool { return s.Len() > 0 } |
| 775 | |
| 776 | func (s *Set) Attr(name string) (Value, error) { return builtinAttr(s, name, setMethods) } |
| 777 | func (s *Set) AttrNames() []string { return builtinAttrNames(setMethods) } |
| 778 | |
| 779 | func (x *Set) CompareSameType(op syntax.Token, y_ Value, depth int) (bool, error) { |
| 780 | y := y_.(*Set) |
| 781 | switch op { |
| 782 | case syntax.EQL: |
| 783 | ok, err := setsEqual(x, y, depth) |
| 784 | return ok, err |
| 785 | case syntax.NEQ: |
| 786 | ok, err := setsEqual(x, y, depth) |
| 787 | return !ok, err |
| 788 | default: |
| 789 | return false, fmt.Errorf("%s %s %s not implemented", x.Type(), op, y.Type()) |
| 790 | } |
| 791 | } |
| 792 | |
| 793 | func setsEqual(x, y *Set, depth int) (bool, error) { |
| 794 | if x.Len() != y.Len() { |
| 795 | return false, nil |
| 796 | } |
| 797 | for _, elem := range x.elems() { |
| 798 | if found, _ := y.Has(elem); !found { |
| 799 | return false, nil |
| 800 | } |
| 801 | } |
| 802 | return true, nil |
| 803 | } |
| 804 | |
| 805 | func (s *Set) Union(iter Iterator) (Value, error) { |
| 806 | set := new(Set) |
| 807 | for _, elem := range s.elems() { |
| 808 | set.Insert(elem) // can't fail |
| 809 | } |
| 810 | var x Value |
| 811 | for iter.Next(&x) { |
| 812 | if err := set.Insert(x); err != nil { |
| 813 | return nil, err |
| 814 | } |
| 815 | } |
| 816 | return set, nil |
| 817 | } |
| 818 | |
| 819 | // toString returns the string form of value v. |
| 820 | // It may be more efficient than v.String() for larger values. |
| 821 | func toString(v Value) string { |
| 822 | var buf bytes.Buffer |
| 823 | path := make([]Value, 0, 4) |
| 824 | writeValue(&buf, v, path) |
| 825 | return buf.String() |
| 826 | } |
| 827 | |
| 828 | // path is the list of *List and *Dict values we're currently printing. |
| 829 | // (These are the only potentially cyclic structures.) |
| 830 | func writeValue(out *bytes.Buffer, x Value, path []Value) { |
| 831 | switch x := x.(type) { |
| 832 | case NoneType: |
| 833 | out.WriteString("None") |
| 834 | |
| 835 | case Int: |
| 836 | out.WriteString(x.String()) |
| 837 | |
| 838 | case Bool: |
| 839 | if x { |
| 840 | out.WriteString("True") |
| 841 | } else { |
| 842 | out.WriteString("False") |
| 843 | } |
| 844 | |
| 845 | case String: |
| 846 | fmt.Fprintf(out, "%q", string(x)) |
| 847 | |
| 848 | case *List: |
| 849 | out.WriteByte('[') |
| 850 | if pathContains(path, x) { |
| 851 | out.WriteString("...") // list contains itself |
| 852 | } else { |
| 853 | for i, elem := range x.elems { |
| 854 | if i > 0 { |
| 855 | out.WriteString(", ") |
| 856 | } |
| 857 | writeValue(out, elem, append(path, x)) |
| 858 | } |
| 859 | } |
| 860 | out.WriteByte(']') |
| 861 | |
| 862 | case Tuple: |
| 863 | out.WriteByte('(') |
| 864 | for i, elem := range x { |
| 865 | if i > 0 { |
| 866 | out.WriteString(", ") |
| 867 | } |
| 868 | writeValue(out, elem, path) |
| 869 | } |
| 870 | if len(x) == 1 { |
| 871 | out.WriteByte(',') |
| 872 | } |
| 873 | out.WriteByte(')') |
| 874 | |
| 875 | case *Function: |
| 876 | fmt.Fprintf(out, "<function %s>", x.Name()) |
| 877 | |
| 878 | case *Builtin: |
| 879 | if x.recv != nil { |
| 880 | fmt.Fprintf(out, "<built-in method %s of %s value>", x.Name(), x.recv.Type()) |
| 881 | } else { |
| 882 | fmt.Fprintf(out, "<built-in function %s>", x.Name()) |
| 883 | } |
| 884 | |
| 885 | case *Dict: |
| 886 | out.WriteByte('{') |
| 887 | if pathContains(path, x) { |
| 888 | out.WriteString("...") // dict contains itself |
| 889 | } else { |
| 890 | sep := "" |
| 891 | for _, item := range x.Items() { |
| 892 | k, v := item[0], item[1] |
| 893 | out.WriteString(sep) |
| 894 | writeValue(out, k, path) |
| 895 | out.WriteString(": ") |
| 896 | writeValue(out, v, append(path, x)) // cycle check |
| 897 | sep = ", " |
| 898 | } |
| 899 | } |
| 900 | out.WriteByte('}') |
| 901 | |
| 902 | case *Set: |
| 903 | out.WriteString("set([") |
| 904 | for i, elem := range x.elems() { |
| 905 | if i > 0 { |
| 906 | out.WriteString(", ") |
| 907 | } |
| 908 | writeValue(out, elem, path) |
| 909 | } |
| 910 | out.WriteString("])") |
| 911 | |
| 912 | default: |
| 913 | out.WriteString(x.String()) |
| 914 | } |
| 915 | } |
| 916 | |
| 917 | func pathContains(path []Value, x Value) bool { |
| 918 | for _, y := range path { |
| 919 | if x == y { |
| 920 | return true |
| 921 | } |
| 922 | } |
| 923 | return false |
| 924 | } |
| 925 | |
| 926 | const maxdepth = 10 |
| 927 | |
| 928 | // Equal reports whether two Skylark values are equal. |
| 929 | func Equal(x, y Value) (bool, error) { |
| 930 | return EqualDepth(x, y, maxdepth) |
| 931 | } |
| 932 | |
| 933 | // EqualDepth reports whether two Skylark values are equal. |
| 934 | // |
| 935 | // Recursive comparisons by implementations of Value.CompareSameType |
| 936 | // should use EqualDepth to prevent infinite recursion. |
| 937 | func EqualDepth(x, y Value, depth int) (bool, error) { |
| 938 | return CompareDepth(syntax.EQL, x, y, depth) |
| 939 | } |
| 940 | |
| 941 | // Compare compares two Skylark values. |
| 942 | // The comparison operation must be one of EQL, NEQ, LT, LE, GT, or GE. |
| 943 | // Compare returns an error if an ordered comparison was |
| 944 | // requested for a type that does not support it. |
| 945 | // |
| 946 | // Recursive comparisons by implementations of Value.CompareSameType |
| 947 | // should use CompareDepth to prevent infinite recursion. |
| 948 | func Compare(op syntax.Token, x, y Value) (bool, error) { |
| 949 | return CompareDepth(op, x, y, maxdepth) |
| 950 | } |
| 951 | |
| 952 | // CompareDepth compares two Skylark values. |
| 953 | // The comparison operation must be one of EQL, NEQ, LT, LE, GT, or GE. |
| 954 | // CompareDepth returns an error if an ordered comparison was |
| 955 | // requested for a pair of values that do not support it. |
| 956 | // |
| 957 | // The depth parameter limits the maximum depth of recursion |
| 958 | // in cyclic data structures. |
| 959 | func CompareDepth(op syntax.Token, x, y Value, depth int) (bool, error) { |
| 960 | if depth < 1 { |
| 961 | return false, fmt.Errorf("comparison exceeded maximum recursion depth") |
| 962 | } |
| 963 | if sameType(x, y) { |
| 964 | if xcomp, ok := x.(Comparable); ok { |
| 965 | return xcomp.CompareSameType(op, y, depth) |
| 966 | } |
| 967 | |
| 968 | // use identity comparison |
| 969 | switch op { |
| 970 | case syntax.EQL: |
| 971 | return x == y, nil |
| 972 | case syntax.NEQ: |
| 973 | return x != y, nil |
| 974 | } |
| 975 | return false, fmt.Errorf("%s %s %s not implemented", x.Type(), op, y.Type()) |
| 976 | } |
| 977 | |
| 978 | // different types |
| 979 | |
| 980 | // int/float ordered comparisons |
| 981 | switch x := x.(type) { |
| 982 | case Int: |
| 983 | if y, ok := y.(Float); ok { |
| 984 | if y != y { |
| 985 | return false, nil // y is NaN |
| 986 | } |
| 987 | var cmp int |
| 988 | if !math.IsInf(float64(y), 0) { |
| 989 | cmp = x.rational().Cmp(y.rational()) // y is finite |
| 990 | } else if y > 0 { |
| 991 | cmp = -1 // y is +Inf |
| 992 | } else { |
| 993 | cmp = +1 // y is -Inf |
| 994 | } |
| 995 | return threeway(op, cmp), nil |
| 996 | } |
| 997 | case Float: |
| 998 | if y, ok := y.(Int); ok { |
| 999 | if x != x { |
| 1000 | return false, nil // x is NaN |
| 1001 | } |
| 1002 | var cmp int |
| 1003 | if !math.IsInf(float64(x), 0) { |
| 1004 | cmp = x.rational().Cmp(y.rational()) // x is finite |
| 1005 | } else if x > 0 { |
| 1006 | cmp = -1 // x is +Inf |
| 1007 | } else { |
| 1008 | cmp = +1 // x is -Inf |
| 1009 | } |
| 1010 | return threeway(op, cmp), nil |
| 1011 | } |
| 1012 | } |
| 1013 | |
| 1014 | // All other values of different types compare unequal. |
| 1015 | switch op { |
| 1016 | case syntax.EQL: |
| 1017 | return false, nil |
| 1018 | case syntax.NEQ: |
| 1019 | return true, nil |
| 1020 | } |
| 1021 | return false, fmt.Errorf("%s %s %s not implemented", x.Type(), op, y.Type()) |
| 1022 | } |
| 1023 | |
| 1024 | func sameType(x, y Value) bool { |
| 1025 | return reflect.TypeOf(x) == reflect.TypeOf(y) || x.Type() == y.Type() |
| 1026 | } |
| 1027 | |
| 1028 | // threeway interprets a three-way comparison value cmp (-1, 0, +1) |
| 1029 | // as a boolean comparison (e.g. x < y). |
| 1030 | func threeway(op syntax.Token, cmp int) bool { |
| 1031 | switch op { |
| 1032 | case syntax.EQL: |
| 1033 | return cmp == 0 |
| 1034 | case syntax.NEQ: |
| 1035 | return cmp != 0 |
| 1036 | case syntax.LE: |
| 1037 | return cmp <= 0 |
| 1038 | case syntax.LT: |
| 1039 | return cmp < 0 |
| 1040 | case syntax.GE: |
| 1041 | return cmp >= 0 |
| 1042 | case syntax.GT: |
| 1043 | return cmp > 0 |
| 1044 | } |
| 1045 | panic(op) |
| 1046 | } |
| 1047 | |
| 1048 | func b2i(b bool) int { |
| 1049 | if b { |
| 1050 | return 1 |
| 1051 | } else { |
| 1052 | return 0 |
| 1053 | } |
| 1054 | } |
| 1055 | |
| 1056 | // Len returns the length of a string or sequence value, |
| 1057 | // and -1 for all others. |
| 1058 | // |
| 1059 | // Warning: Len(x) >= 0 does not imply Iterate(x) != nil. |
| 1060 | // A string has a known length but is not directly iterable. |
| 1061 | func Len(x Value) int { |
| 1062 | switch x := x.(type) { |
| 1063 | case String: |
| 1064 | return x.Len() |
| 1065 | case Sequence: |
| 1066 | return x.Len() |
| 1067 | } |
| 1068 | return -1 |
| 1069 | } |
| 1070 | |
| 1071 | // Iterate return a new iterator for the value if iterable, nil otherwise. |
| 1072 | // If the result is non-nil, the caller must call Done when finished with it. |
| 1073 | // |
| 1074 | // Warning: Iterate(x) != nil does not imply Len(x) >= 0. |
| 1075 | // Some iterables may have unknown length. |
| 1076 | func Iterate(x Value) Iterator { |
| 1077 | if x, ok := x.(Iterable); ok { |
| 1078 | return x.Iterate() |
| 1079 | } |
| 1080 | return nil |
| 1081 | } |