ttf-view 0.4.0

A TrueType/OpenType font parsing/viewing library and a CLI tool.
Documentation 
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

use std::{cmp::Ordering, marker::PhantomData, num::NonZero, ptr::NonNull};

/// A dual iterator, that iterates through either `&[A]` or `&[B]`, using only 2 pointers worth
/// of memory. When iterating through `&[A]`, pointers are stored as `(start, end)`, and when
/// iterating through `&[B]` - as `(end, start)`, removing the need for a extra field.
#[derive(Clone)]
pub struct PackedDualIter<'a, T, A, B> {
    ptr_a: NonNull<()>,
    ptr_b: NonNull<()>,
    _phantom: PhantomData<&'a (T, A, B)>,
}

impl<'a, T: From<A> + From<B>, A: Copy, B: Copy> PackedDualIter<'a, T, A, B> {
    pub const fn new_a(slice: &'a [A]) -> Self {
        let start = NonNull::from_ref(slice).cast::<()>();
        let end = unsafe { start.byte_add(size_of_val(slice)) };
        Self { ptr_a: start, ptr_b: end, _phantom: Default::default() }
    }
    pub const fn new_b(slice: &'a [B]) -> Self {
        let start = NonNull::from_ref(slice).cast::<()>();
        let end = unsafe { start.byte_add(size_of_val(slice)) };
        Self { ptr_a: end, ptr_b: start, _phantom: Default::default() }
    }

    // pub fn as_slice_a(&self) -> Option<&'a [A]> {
    //     if self.ptr_a < self.ptr_b { Some(self._a_slice()) } else { None }
    // }
    // pub fn as_slice_b(&self) -> Option<&'a [B]> {
    //     if self.ptr_b < self.ptr_a { Some(self._b_slice()) } else { None }
    // }

    fn _a_read_start(&self) -> T {
        T::from(unsafe { self.ptr_a.cast::<A>().read() })
    }
    fn _a_read_end(&self) -> T {
        T::from(unsafe { self.ptr_b.cast::<A>().read() })
    }
    fn _b_read_start(&self) -> T {
        T::from(unsafe { self.ptr_b.cast::<B>().read() })
    }
    fn _b_read_end(&self) -> T {
        T::from(unsafe { self.ptr_a.cast::<B>().read() })
    }

    fn _a_advance(&mut self, n: usize) {
        self.ptr_a = unsafe { self.ptr_a.byte_add(n * size_of::<A>()) };
    }
    fn _b_advance(&mut self, n: usize) {
        self.ptr_b = unsafe { self.ptr_b.byte_add(n * size_of::<B>()) };
    }
    fn _a_advance_back(&mut self, n: usize) {
        self.ptr_b = unsafe { self.ptr_b.byte_sub(n * size_of::<A>()) };
    }
    fn _b_advance_back(&mut self, n: usize) {
        self.ptr_a = unsafe { self.ptr_a.byte_sub(n * size_of::<B>()) };
    }

    fn _a_len(&self) -> usize {
        unsafe { self.ptr_b.byte_offset_from_unsigned(self.ptr_a) / size_of::<A>() }
    }
    fn _b_len(&self) -> usize {
        unsafe { self.ptr_a.byte_offset_from_unsigned(self.ptr_b) / size_of::<B>() }
    }
    fn _a_slice(&self) -> &'a [A] {
        unsafe { NonNull::slice_from_raw_parts(self.ptr_a.cast::<A>(), self._a_len()).as_ref() }
    }
    fn _b_slice(&self) -> &'a [B] {
        unsafe { NonNull::slice_from_raw_parts(self.ptr_b.cast::<B>(), self._b_len()).as_ref() }
    }
}

impl<'a, T: From<A> + From<B>, A: Copy, B: Copy> Iterator for PackedDualIter<'a, T, A, B> {
    type Item = T;

    fn next(&mut self) -> Option<Self::Item> {
        match self.ptr_a.cmp(&self.ptr_b) {
            Ordering::Equal => None,
            Ordering::Less => {
                let item = self._a_read_start();
                self._a_advance(1);
                Some(item)
            },
            Ordering::Greater => {
                let item = self._b_read_start();
                self._b_advance(1);
                Some(item)
            },
        }
    }
    fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
        match self.ptr_a.cmp(&self.ptr_b) {
            Ordering::Equal => NonZero::new(n).map_or(Ok(()), Err),
            Ordering::Less => {
                let advance = self._a_len().min(n);
                self._a_advance(advance);
                NonZero::new(n - advance).map_or(Ok(()), Err)
            },
            Ordering::Greater => {
                let advance = self._b_len().min(n);
                self._b_advance(advance);
                NonZero::new(n - advance).map_or(Ok(()), Err)
            },
        }
    }
    fn nth(&mut self, n: usize) -> Option<Self::Item> {
        self.advance_by(n).ok()?;
        self.next()
    }
    fn try_fold<I, F, R>(&mut self, init: I, f: F) -> R
    where
        F: FnMut(I, Self::Item) -> R,
        R: std::ops::Try<Output = I>,
    {
        match self.ptr_a.cmp(&self.ptr_b) {
            Ordering::Equal => R::from_output(init),
            Ordering::Less => self._a_slice().iter().copied().map(T::from).try_fold(init, f),
            Ordering::Greater => self._b_slice().iter().copied().map(T::from).try_fold(init, f),
        }
    }
    fn fold<I, F>(mut self, init: I, mut f: F) -> I
    where F: FnMut(I, Self::Item) -> I {
        self.try_fold(init, |init, x| Ok::<_, !>(f(init, x))).unwrap()
    }
    fn last(mut self) -> Option<Self::Item> {
        self.next_back()
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        let len = self.len();
        (len, Some(len))
    }
}

impl<'a, T: From<A> + From<B>, A: Copy, B: Copy> ExactSizeIterator for PackedDualIter<'a, T, A, B> {
    fn is_empty(&self) -> bool {
        self.ptr_a == self.ptr_b
    }
    fn len(&self) -> usize {
        if self.ptr_a < self.ptr_b { self._a_len() } else { self._b_len() }
    }
}

impl<'a, T: From<A> + From<B>, A: Copy, B: Copy> DoubleEndedIterator
    for PackedDualIter<'a, T, A, B>
{
    fn next_back(&mut self) -> Option<Self::Item> {
        match self.ptr_a.cmp(&self.ptr_b) {
            Ordering::Equal => None,
            Ordering::Less => {
                self._a_advance_back(1);
                Some(self._a_read_end())
            },
            Ordering::Greater => {
                self._b_advance_back(1);
                Some(self._b_read_end())
            },
        }
    }
    fn advance_back_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
        match self.ptr_a.cmp(&self.ptr_b) {
            Ordering::Equal => NonZero::new(n).map_or(Ok(()), Err),
            Ordering::Less => {
                let advance = self._a_len().min(n);
                self._a_advance_back(advance);
                NonZero::new(n - advance).map_or(Ok(()), Err)
            },
            Ordering::Greater => {
                let advance = self._b_len().min(n);
                self._b_advance_back(advance);
                NonZero::new(n - advance).map_or(Ok(()), Err)
            },
        }
    }
    fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
        self.advance_back_by(n).ok()?;
        self.next_back()
    }
    fn try_rfold<I, F, R>(&mut self, init: I, f: F) -> R
    where
        F: FnMut(I, Self::Item) -> R,
        R: std::ops::Try<Output = I>,
    {
        match self.ptr_a.cmp(&self.ptr_b) {
            Ordering::Equal => R::from_output(init),
            Ordering::Less => self._a_slice().iter().copied().map(T::from).try_rfold(init, f),
            Ordering::Greater => self._b_slice().iter().copied().map(T::from).try_rfold(init, f),
        }
    }
    fn rfold<I, F>(mut self, init: I, mut f: F) -> I
    where F: FnMut(I, Self::Item) -> I {
        self.try_rfold(init, |init, x| Ok::<_, !>(f(init, x))).unwrap()
    }
}