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//! The [font header][1].
//!
//! [1]: https://www.microsoft.com/typography/otspec/head.htm

use q32;

const MAGIC_NUMBER: u32 = 0x5F0F3CF5;

macro_rules! reject(() => (raise!("found a malformed font header")));

table! {
    #[doc = "A font header."]
    #[derive(Copy)]
    pub FontHeader {
        version (q32) |_, tape| { // version
            let value = try!(tape.take());
            if value != q32(0x00010000) {
                raise!("found an unknown version of the font header");
            }
            Ok(value)
        },

        revision            (q32), // fontRevision
        checksum_adjustment (u32), // checkSumAdjustment

        magic_number (u32) |_, tape| { // MagicNumber
            let value = try!(tape.take());
            if value != MAGIC_NUMBER {
                reject!();
            }
            Ok(value)
        },

        flags                (Flags), // flags
        units_per_em         (u16  ), // unitsPerEm
        created              (i64  ), // created
        modified             (i64  ), // modified
        min_x                (i16  ), // xMin
        min_y                (i16  ), // yMin
        max_x                (i16  ), // xMax
        max_y                (i16  ), // yMax
        mac_style            (u16  ), // macStyle
        lowest_ppem          (u16  ), // lowestRecPPEM
        direction_hint       (i16  ), // fontDirectionHint
        glyph_mapping_format (i16  ), // indexToLocFormat
        glyph_data_format    (i16  ), // glyphDataFormat
    }
}

flags! {
    #[doc = "Font-header flags."]
    pub Flags(u16) {
        0b0000_0000_0000_0001 => is_baseline_at_0,
        0b0000_0000_0000_0010 => is_left_side_bearing_at_0,
        0b1000_0000_0000_0000 => is_invalid,
    }
}