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
//! A [Feature Name Table](
//! https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6feat.html) implementation.

use crate::parser::{FromData, LazyArray16, Offset, Offset32, Stream};

#[derive(Clone, Copy, Debug)]
struct FeatureNameRecord {
    feature: u16,
    setting_table_records_count: u16,
    // Offset from the beginning of the table.
    setting_table_offset: Offset32,
    flags: u8,
    default_setting_index: u8,
    name_index: u16,
}

impl FromData for FeatureNameRecord {
    const SIZE: usize = 12;

    #[inline]
    fn parse(data: &[u8]) -> Option<Self> {
        let mut s = Stream::new(data);
        Some(FeatureNameRecord {
            feature: s.read::<u16>()?,
            setting_table_records_count: s.read::<u16>()?,
            setting_table_offset: s.read::<Offset32>()?,
            flags: s.read::<u8>()?,
            default_setting_index: s.read::<u8>()?,
            name_index: s.read::<u16>()?,
        })
    }
}

/// A setting name.
#[derive(Clone, Copy, Debug)]
pub struct SettingName {
    /// The setting.
    pub setting: u16,
    /// The `name` table index for the feature's name in a 256..32768 range.
    pub name_index: u16,
}

impl FromData for SettingName {
    const SIZE: usize = 4;

    #[inline]
    fn parse(data: &[u8]) -> Option<Self> {
        let mut s = Stream::new(data);
        Some(SettingName {
            setting: s.read::<u16>()?,
            name_index: s.read::<u16>()?,
        })
    }
}

/// A feature names.
#[derive(Clone, Copy, Debug)]
pub struct FeatureName<'a> {
    /// The feature's ID.
    pub feature: u16,
    /// The feature's setting names.
    pub setting_names: LazyArray16<'a, SettingName>,
    /// The index of the default setting in the `setting_names`.
    pub default_setting_index: u8,
    /// The feature's exclusive settings. If set, the feature settings are mutually exclusive.
    pub exclusive: bool,
    /// The `name` table index for the feature's name in a 256..32768 range.
    pub name_index: u16,
}

/// A list fo feature names.
#[derive(Clone, Copy)]
pub struct FeatureNames<'a> {
    data: &'a [u8],
    records: LazyArray16<'a, FeatureNameRecord>,
}

impl<'a> FeatureNames<'a> {
    /// Returns a feature name at an index.
    pub fn get(&self, index: u16) -> Option<FeatureName<'a>> {
        let record = self.records.get(index)?;
        let data = self.data.get(record.setting_table_offset.to_usize()..)?;
        let mut s = Stream::new(data);
        let setting_names = s.read_array16::<SettingName>(record.setting_table_records_count)?;
        Some(FeatureName {
            feature: record.feature,
            setting_names,
            default_setting_index: if record.flags & 0x40 != 0 {
                record.default_setting_index
            } else {
                0
            },
            exclusive: record.flags & 0x80 != 0,
            name_index: record.name_index,
        })
    }

    /// Finds a feature name by ID.
    pub fn find(&self, feature: u16) -> Option<FeatureName<'a>> {
        let index = self
            .records
            .binary_search_by(|name| name.feature.cmp(&feature))
            .map(|(i, _)| i)?;
        self.get(index)
    }

    /// Returns the number of feature names.
    pub fn len(&self) -> u16 {
        self.records.len()
    }

    /// Checks if there are any feature names.
    pub fn is_empty(&self) -> bool {
        self.records.is_empty()
    }
}

impl<'a> core::fmt::Debug for FeatureNames<'a> {
    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
        f.debug_list().entries(*self).finish()
    }
}

impl<'a> IntoIterator for FeatureNames<'a> {
    type Item = FeatureName<'a>;
    type IntoIter = FeatureNamesIter<'a>;

    #[inline]
    fn into_iter(self) -> Self::IntoIter {
        FeatureNamesIter {
            names: self,
            index: 0,
        }
    }
}

/// An iterator over [`FeatureNames`].
#[allow(missing_debug_implementations)]
pub struct FeatureNamesIter<'a> {
    names: FeatureNames<'a>,
    index: u16,
}

impl<'a> Iterator for FeatureNamesIter<'a> {
    type Item = FeatureName<'a>;

    fn next(&mut self) -> Option<Self::Item> {
        if self.index < self.names.len() {
            self.index += 1;
            self.names.get(self.index - 1)
        } else {
            None
        }
    }
}

/// A [Feature Name Table](
/// https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6feat.html).
#[derive(Clone, Copy, Debug)]
pub struct Table<'a> {
    /// A list of feature names. Sorted by `FeatureName.feature`.
    pub names: FeatureNames<'a>,
}

impl<'a> Table<'a> {
    /// Parses a table from raw data.
    pub fn parse(data: &'a [u8]) -> Option<Self> {
        let mut s = Stream::new(data);

        let version = s.read::<u32>()?;
        if version != 0x00010000 {
            return None;
        }

        let count = s.read::<u16>()?;
        s.advance_checked(6)?; // reserved
        let records = s.read_array16::<FeatureNameRecord>(count)?;

        Some(Table {
            names: FeatureNames { data, records },
        })
    }
}