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
//! Specialized iterator traits.
//!
//! The traits are iterable, and provide optimizations for contiguous
//! iterators, while still working for non-contiguous data.
#![cfg(feature = "parse")]
pub use crate::buffer::Buffer;
// Re-export our digit iterators.
#[cfg(not(feature = "format"))]
pub use crate::noskip::{AsBytes, Bytes};
#[cfg(feature = "format")]
pub use crate::skip::{AsBytes, Bytes};
/// Iterator over a contiguous block of bytes.
///
/// This allows us to convert to-and-from-slices, raw pointers, and
/// peek/query the data from either end cheaply.
///
/// A default implementation is provided for slice iterators.
/// This trait **should never** return `null` from `as_ptr`, or be
/// implemented for non-contiguous data.
///
/// # Safety
///
/// The safe methods are sound as long as the caller ensures that
/// the methods for `read_32`, `read_64`, etc. check the bounds
/// of the underlying contiguous buffer and is only called on
/// contiguous buffers.
pub unsafe trait BytesIter<'a>: Iterator<Item = &'a u8> + Buffer<'a> {
/// Get the total number of elements in the underlying slice.
fn length(&self) -> usize;
/// Get the current index of the iterator in the slice.
fn cursor(&self) -> usize;
/// Set the current index of the iterator in the slice.
///
/// This is **NOT** the current position of the iterator,
/// since iterators may skip digits: this is the cursor
/// in the underlying buffer. For example, if `slc[2]` is
/// skipped, `set_cursor(3)` would be the 3rd element in
/// the iterator, not the 4th.
///
/// # Safety
///
/// Safe if `index <= self.length()`. Although this won't
/// affect safety, the caller also should be careful it
/// does not set the cursor within skipped characters.
unsafe fn set_cursor(&mut self, index: usize);
/// Set the cursor to the start of the buffer.
#[inline(always)]
fn seek_start(&mut self) {
// SAFETY: 0 is alwatys <= any usize value.
unsafe { self.set_cursor(0) };
}
/// Get a slice to the full buffer, which may or may not be the same as
/// `as_slice`.
fn as_full_slice(&self) -> &'a [u8];
/// Get the current number of values returned by the iterator.
fn current_count(&self) -> usize;
/// Get if the iterator cannot return any more elements.
///
/// This may advance the internal iterator state, but not
/// modify the next returned value.
///
/// If this is an iterator, this is based on the number of items
/// left to be returned. We do not necessarly know the length of
/// the buffer. If this is a non-contiguous iterator, this **MUST**
/// advance the state until it knows a value can be returned.
///
/// Any incorrect implementations of this affect all safety invariants
/// for the rest of the trait. For contiguous iterators, this can be
/// as simple as checking if `self.cursor >= self.slc.len()`, but for
/// non-contiguous iterators you **MUST** advance to the next element
/// to be returned, then check to see if a value exists. The safest
/// implementation is always to check if `self.peek().is_none()` and
/// ensure [peek] is always safe.
///
/// If you would like to see if the cursor is at the end of the buffer,
/// see [is_done] or [is_empty] instead.
///
/// [is_done]: BytesIter::is_done
/// [is_empty]: Buffer::is_empty
/// [peek]: BytesIter::peek
#[inline(always)]
#[allow(clippy::wrong_self_convention)]
fn is_consumed(&mut self) -> bool {
self.peek().is_none()
}
/// Get if the buffer underlying the iterator is empty.
///
/// This might not be the same thing as [is_consumed]: [is_consumed]
/// checks if any more elements may be returned, which may require
/// peeking the next value. Consumed merely checks if the
/// iterator has an empty slice. It is effectively a cheaper,
/// but weaker variant of [is_consumed].
///
/// [is_consumed]: BytesIter::is_consumed
fn is_done(&self) -> bool;
/// Peek the next value of the iterator, without checking bounds.
///
/// Note that this can modify the internal state, by skipping digits
/// for iterators that find the first non-zero value, etc.
///
/// # Safety
///
/// Safe as long as there is at least a single valid value left in
/// the iterator. Note that the behavior of this may lead to out-of-bounds
/// access (for contiguous iterators) or panics (for non-contiguous
/// iterators).
unsafe fn peek_unchecked(&mut self) -> Self::Item;
/// Peek the next value of the iterator, without consuming it.
///
/// Note that this can modify the internal state, by skipping digits
/// for iterators that find the first non-zero value, etc.
#[inline(always)]
fn peek(&mut self) -> Option<Self::Item> {
if !self.is_empty() {
// SAFETY: safe since the buffer cannot be empty
unsafe { Some(self.peek_unchecked()) }
} else {
None
}
}
/// Peek the next value of the iterator, and step only if it exists.
#[inline(always)]
fn try_read(&mut self) -> Option<Self::Item> {
if let Some(value) = self.peek() {
// SAFETY: the slice cannot be empty because we peeked a value.
unsafe { self.step_unchecked() };
Some(value)
} else {
None
}
}
/// Check if the next element is a given value.
#[inline(always)]
fn peek_is(&mut self, value: u8) -> bool {
if let Some(&c) = self.peek() {
c == value
} else {
false
}
}
/// Peek the next value and consume it if the read value matches the
/// expected one.
#[inline(always)]
fn read_if<Pred: FnOnce(&u8) -> bool>(&mut self, pred: Pred) -> Option<Self::Item> {
if let Some(peeked) = self.peek() {
if pred(peeked) {
// SAFETY: the slice cannot be empty because we peeked a value.
unsafe { self.step_unchecked() };
Some(peeked)
} else {
None
}
} else {
None
}
}
/// Check if the next element is a given value without case sensitivity.
#[inline(always)]
fn case_insensitive_peek_is(&mut self, value: u8) -> bool {
if let Some(&c) = self.peek() {
c.to_ascii_lowercase() == value.to_ascii_lowercase()
} else {
false
}
}
/// Skip zeros from the start of the iterator
#[inline(always)]
fn skip_zeros(&mut self) -> usize {
let start = self.cursor();
while let Some(&b'0') = self.peek() {
self.next();
}
self.cursor() - start
}
/// Read a value of a difference type from the iterator.
///
/// This advances the internal state of the iterator. This
/// can only be implemented for contiguous iterators: non-
/// contiguous iterators **MUST** panic.
///
/// # Safety
///
/// Safe as long as the number of the buffer is contains as least as
/// many bytes as the size of V. This must be unimplemented for
/// non-contiguous iterators.
#[inline(always)]
unsafe fn read_unchecked<V>(&self) -> V {
unimplemented!();
}
/// Try to read a the next four bytes as a u32.
/// This advances the internal state of the iterator.
fn read_u32(&self) -> Option<u32>;
/// Try to read the next eight bytes as a u64
/// This advances the internal state of the iterator.
fn read_u64(&self) -> Option<u64>;
/// Advance the internal slice by `N` elements.
///
/// This does not advance the iterator by `N` elements for
/// non-contiguous iterators: this just advances the internal,
/// underlying buffer. This is useful for multi-digit optimizations
/// for contiguous iterators.
///
/// # Safety
///
/// As long as the iterator is at least `N` elements, this
/// is safe.
unsafe fn step_by_unchecked(&mut self, count: usize);
/// Advance the internal slice by 1 element.
///
/// # Safety
///
/// Safe as long as the iterator is not empty.
#[inline(always)]
unsafe fn step_unchecked(&mut self) {
unsafe { self.step_by_unchecked(1) };
}
}