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
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
use crate::error::{DecodeError, DecodeErrorKind};
use crate::mutf8::{CharsLossy, MStr};
use std::fmt;

/// A field type descriptor not wrapped within an array.
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum BaseType<'a> {
    Boolean,
    Byte,
    Short,
    Integer,
    Long,
    Float,
    Double,
    Char,
    Object(&'a MStr),
}

impl<'a> fmt::Display for BaseType<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        use BaseType::*;
        match self {
            Boolean => write!(f, "Z"),
            Byte => write!(f, "B"),
            Short => write!(f, "S"),
            Integer => write!(f, "I"),
            Long => write!(f, "J"),
            Float => write!(f, "F"),
            Double => write!(f, "D"),
            Char => write!(f, "C"),
            Object(name) => write!(f, "L{};", name.display()),
        }
    }
}

/// A field descriptor represents the type of a class, instance or local variable.
/// It is a [`BaseType`] that may be wrapped in a n-dimensional array.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct TypeDescriptor<'a> {
    pub dimensions: u8,
    pub base: BaseType<'a>,
}

impl<'a> TypeDescriptor<'a> {
    /// Parses a field descriptor as described in [§4.3.2](https://docs.oracle.com/javase/specs/jvms/se18/html/jvms-4.html#jvms-4.3.2).
    ///
    /// # Examples
    /// ```
    /// use noak::descriptor::{BaseType, TypeDescriptor};
    /// use noak::MStr;
    ///
    /// let descriptor = TypeDescriptor::parse(MStr::from_mutf8(b"[F").unwrap()).unwrap();
    /// assert_eq!(descriptor.dimensions, 1);
    /// assert_eq!(descriptor.base, BaseType::Float);
    /// ```
    pub fn parse(s: &'a MStr) -> Result<TypeDescriptor<'a>, DecodeError> {
        let mut chars = s.chars_lossy().enumerate();
        let mut dimensions: u8 = 0;
        while let Some((start, ch)) = chars.next() {
            if ch == '[' {
                // Can't have more than 255 dimensions.
                dimensions = if let Some(dimensions) = dimensions.checked_add(1) {
                    dimensions
                } else {
                    break;
                };
            } else {
                use BaseType::*;

                let base = match ch {
                    'Z' => Boolean,
                    'B' => Byte,
                    'S' => Short,
                    'I' => Integer,
                    'J' => Long,
                    'F' => Float,
                    'D' => Double,
                    'C' => Char,
                    'L' => {
                        // Assure that the descriptor contains a ';'.
                        if !chars.by_ref().any(|(_, ch)| ch == ';') {
                            break;
                        }

                        // Extract the name from the descriptor
                        let name = &s[start + 1..s.len() - 1];
                        // Assure that the name is not empty.
                        if name.is_empty() {
                            break;
                        }
                        Object(name)
                    }
                    _ => break,
                };

                // Verify that there is no character after the base type.
                if chars.next().is_some() {
                    break;
                }

                return Ok(TypeDescriptor { dimensions, base });
            }
        }

        Err(DecodeError::new(DecodeErrorKind::InvalidDescriptor))
    }
}

impl<'a> fmt::Display for TypeDescriptor<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        for _ in 0..self.dimensions {
            write!(f, "[")?;
        }

        write!(f, "{}", self.base)
    }
}

/// A method descriptor specifies the parameter types and return type of a method.
pub struct MethodDescriptor<'a> {
    input: &'a MStr,
    return_index: usize,
}

impl<'a> MethodDescriptor<'a> {
    /// Parses a method descriptor as described in [§4.3.3](https://docs.oracle.com/javase/specs/jvms/se18/html/jvms-4.html#jvms-4.3.3).
    ///
    /// # Examples
    /// ```
    /// use noak::descriptor::{BaseType, MethodDescriptor, TypeDescriptor};
    /// use noak::MStr;
    ///
    /// let descriptor = MethodDescriptor::parse(MStr::from_mutf8(b"(Ljava/lang/String;)I").unwrap()).unwrap();
    /// assert_eq!(descriptor.parameters().count(), 1);
    /// assert_eq!(descriptor.return_type(), Some(TypeDescriptor { dimensions: 0, base: BaseType::Integer }));
    /// ```
    pub fn parse(input: &'a MStr) -> Result<MethodDescriptor<'a>, DecodeError> {
        let mut chars = input.chars_lossy();
        if let Some('(') = chars.next() {
            loop {
                let ch = chars.next();
                if let Some(')') = ch {
                    break;
                }

                validate_type(ch, &mut chars, false)?;
            }

            let return_index = input.len() - chars.as_mstr().len();
            validate_type(chars.next(), &mut chars, true)?;
            if chars.next().is_none() {
                return Ok(MethodDescriptor { input, return_index });
            }
        }

        Err(DecodeError::new(DecodeErrorKind::InvalidDescriptor))
    }

    /// Returns an iterator over the method parameters.
    pub fn parameters(&self) -> impl Iterator<Item = TypeDescriptor<'a>> + 'a {
        struct Parameters<'a> {
            chars: CharsLossy<'a>,
        }

        impl<'a> Iterator for Parameters<'a> {
            type Item = TypeDescriptor<'a>;

            fn next(&mut self) -> Option<TypeDescriptor<'a>> {
                match self.chars.next() {
                    Some(')') | None => {
                        self.chars = <&MStr>::default().chars_lossy();
                        None
                    }
                    Some(ch) => Some(read_type(ch, &mut self.chars)),
                }
            }
        }

        let mut chars = self.input.chars_lossy();
        // skip the `(`
        chars.next();
        Parameters { chars }
    }

    /// Returns the return type of this method descriptor.
    /// If the return type is void (`V`), then `None` is returned.
    #[must_use]
    pub fn return_type(&self) -> Option<TypeDescriptor<'a>> {
        let input = &self.input[self.return_index..];
        if input.as_bytes() == b"V" {
            None
        } else {
            let mut chars = input.chars_lossy();
            Some(read_type(chars.next().unwrap(), &mut chars))
        }
    }
}

/// Verify that the next type is valid.
fn validate_type(mut ch: Option<char>, chars: &mut CharsLossy<'_>, return_type: bool) -> Result<(), DecodeError> {
    if return_type && ch == Some('V') {
        return Ok(());
    }

    let mut dimensions: u8 = 0;
    while let Some('[') = ch {
        // Can't have more than 255 array dimensions.
        dimensions = dimensions
            .checked_add(1)
            .ok_or_else(|| DecodeError::new(DecodeErrorKind::InvalidDescriptor))?;
        ch = chars.next();
    }
    if let Some(ch) = ch {
        match ch {
            'Z' | 'B' | 'S' | 'I' | 'J' | 'F' | 'D' | 'C' => return Ok(()),
            'L' => {
                let mut found_semicolon = false;
                let mut found_character = false;
                for ch in chars {
                    if ch == ';' {
                        found_semicolon = true;
                        break;
                    }
                    found_character = true;
                }
                if found_semicolon && found_character {
                    return Ok(());
                }
            }
            _ => {}
        }
    }
    Err(DecodeError::new(DecodeErrorKind::InvalidDescriptor))
}

/// Reads a type descriptor from a method descriptor.
/// Does not verify the input.
fn read_type<'a>(mut ch: char, chars: &mut CharsLossy<'a>) -> TypeDescriptor<'a> {
    use BaseType::*;

    let mut dimensions = 0;
    while ch == '[' {
        ch = chars.next().unwrap();
        dimensions += 1;
    }

    let base = match ch {
        'Z' => Boolean,
        'B' => Byte,
        'S' => Short,
        'I' => Integer,
        'J' => Long,
        'F' => Float,
        'D' => Double,
        'C' => Char,
        'L' => {
            let input = chars.as_mstr();
            for ch in chars.by_ref() {
                if ch == ';' {
                    break;
                }
            }

            let name = &input[..input.len() - chars.as_mstr().len() - 1];
            Object(name)
        }
        _ => unreachable!("the tag is guaranteed to be valid"),
    };

    TypeDescriptor { dimensions, base }
}

impl<'a> fmt::Debug for MethodDescriptor<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("MethodDescriptor")
            .field("parameters", &self.parameters().collect::<Vec<_>>())
            .field("return_type", &self.return_type())
            .finish()
    }
}

#[cfg(test)]
mod test {
    use super::{BaseType::*, *};
    use crate::MString;

    #[test]
    fn valid_type() {
        fn eq(s: &str, td: TypeDescriptor<'_>) {
            let m: MString = s.into();
            assert_eq!(TypeDescriptor::parse(&m).unwrap(), td);
        }

        eq(
            "Z",
            TypeDescriptor {
                base: Boolean,
                dimensions: 0,
            },
        );
        eq(
            "B",
            TypeDescriptor {
                base: Byte,
                dimensions: 0,
            },
        );
        eq(
            "S",
            TypeDescriptor {
                base: Short,
                dimensions: 0,
            },
        );
        eq(
            "I",
            TypeDescriptor {
                base: Integer,
                dimensions: 0,
            },
        );
        eq(
            "J",
            TypeDescriptor {
                base: Long,
                dimensions: 0,
            },
        );
        eq(
            "F",
            TypeDescriptor {
                base: Float,
                dimensions: 0,
            },
        );
        eq(
            "D",
            TypeDescriptor {
                base: Double,
                dimensions: 0,
            },
        );
        eq(
            "Ljava/lang/String;",
            TypeDescriptor {
                base: Object(&MString::from("java/lang/String")),
                dimensions: 0,
            },
        );

        eq(
            "[D",
            TypeDescriptor {
                base: Double,
                dimensions: 1,
            },
        );
        eq(
            "[[Ljava/lang/String;",
            TypeDescriptor {
                base: Object(&MString::from("java/lang/String")),
                dimensions: 2,
            },
        );
        eq(
            "[[[[[[[[[[[[[[[[[[F",
            TypeDescriptor {
                base: Float,
                dimensions: 18,
            },
        );
        eq(
            &("[".repeat(255) + "I"),
            TypeDescriptor {
                base: Integer,
                dimensions: 255,
            },
        );
    }

    #[test]
    fn invalid_type() {
        #[track_caller]
        fn check(s: &str) {
            let m: MString = s.into();
            TypeDescriptor::parse(&m).unwrap_err();
        }

        check("");
        check("X");
        check("JJ");
        check("[");
        check("[]JJ");
        check(&("[".repeat(256) + "I"));
        check("L;");
        check("Ljava/lang/Object;;");
    }

    #[test]
    fn valid_method_descriptor() {
        #[track_caller]
        fn eq(s: &str, parameters: &[TypeDescriptor<'_>], return_type: Option<TypeDescriptor<'_>>) {
            let m: MString = s.into();
            let desc = MethodDescriptor::parse(&m).unwrap();

            assert_eq!(desc.parameters().collect::<Vec<_>>(), parameters);
            assert_eq!(desc.return_type(), return_type);
        }

        eq("()V", &[], None);
        eq(
            "(I)V",
            &[TypeDescriptor {
                dimensions: 0,
                base: Integer,
            }],
            None,
        );
        eq(
            "([[IF)V",
            &[
                TypeDescriptor {
                    dimensions: 2,
                    base: Integer,
                },
                TypeDescriptor {
                    dimensions: 0,
                    base: Float,
                },
            ],
            None,
        );
        eq(
            "(I)F",
            &[TypeDescriptor {
                dimensions: 0,
                base: Integer,
            }],
            Some(TypeDescriptor {
                dimensions: 0,
                base: Float,
            }),
        );
        eq(
            "(LFoo;)V",
            &[TypeDescriptor {
                dimensions: 0,
                base: Object(&MString::from("Foo")),
            }],
            None,
        );
        eq(
            "()LBar;",
            &[],
            Some(TypeDescriptor {
                dimensions: 0,
                base: Object(&MString::from("Bar")),
            }),
        );
        eq(
            "(LFoo;)LBar;",
            &[TypeDescriptor {
                dimensions: 0,
                base: Object(&MString::from("Foo")),
            }],
            Some(TypeDescriptor {
                dimensions: 0,
                base: Object(&MString::from("Bar")),
            }),
        );
    }

    #[test]
    fn invalid_method_descriptor() {
        fn check(s: &str) {
            let m: MString = s.into();
            assert!(MethodDescriptor::parse(&m).is_err());
        }

        check("");
        check("()");
        check("I)F");
        check("{I)F");
        check("F");
        check("(V)V");
        check("(L)V");
        check("(L;)V");
        check("(L;;)V");
        check("()LHmm");
        check("(L");
        check(&format!("({}I)V", "[".repeat(256)));
    }
}