Handling maxp, post, vhea` versions as Version16Dot16

Signed-off-by: Vsevolod Volkov <[email protected]>

src/tables/maxp.js

@@ -1,8 +1,9 @@
 import * as r from 'restructure';
+import { version16Dot16 } from '../utils';
 
 // maxiumum profile
 export default new r.Struct({
-  version:                r.int32,
+  version:                version16Dot16,
   numGlyphs:              r.uint16,  // The number of glyphs in the font
   maxPoints:              r.uint16,  // Maximum points in a non-composite glyph
   maxContours:            r.uint16,  // Maximum contours in a non-composite glyph

src/tables/post.js

@@ -1,7 +1,8 @@
 import * as r from 'restructure';
+import { version16Dot16 } from '../utils';
 
 // PostScript information
-export default new r.VersionedStruct(r.fixed32, {
+export default new r.VersionedStruct(version16Dot16, {
   header: { // these fields exist at the top of all versions
     italicAngle:        r.fixed32, // Italic angle in counter-clockwise degrees from the vertical.
     underlinePosition:  r.int16,   // Suggested distance of the top of the underline from the baseline

src/tables/vhea.js

@@ -1,9 +1,9 @@
 import * as r from 'restructure';
+import { version16Dot16 } from '../utils';
 
 // Vertical Header Table
 export default new r.Struct({
-  majorVersion:           r.uint16,  // Major version number of the Vertical Header Table
-  minorVersion:           r.uint16,  // Minor version number of the Vertical Header Table
+  version:                version16Dot16,
   ascent:                 r.int16,   // The vertical typographic ascender for this font
   descent:                r.int16,   // The vertical typographic descender for this font
   lineGap:                r.int16,   // The vertical typographic line gap for this font

src/utils.js

@@ -1,3 +1,5 @@
+import { DecodeStream, EncodeStream } from 'restructure';
+
 export function binarySearch(arr, cmp) {
   let min = 0;
   let max = arr.length - 1;
@@ -60,3 +62,37 @@ export function decodeBase64(base64) {
 
   return bytes;
 }
+
+export class Version16Dot16 {
+  fromBuffer(buffer) {
+    let stream = new DecodeStream(buffer);
+    return this.decode(stream);
+  }
+
+  toBuffer(value) {
+    let size = this.size(value);
+    let buffer = new Uint8Array(size);
+    let stream = new EncodeStream(buffer);
+    this.encode(stream, value);
+    return buffer;
+  }
+
+  size() {
+    return 4;
+  }
+
+  decode(stream) {
+    let major = stream.readUInt16BE();
+    let minor = stream.readUInt16BE() >> 12;
+    return major + minor / 10;
+  }
+
+  encode(stream, val) {
+    let major = Math.trunc(val);
+    let minor = (val - major) * 10;
+    stream.writeUInt16BE(major);
+    return stream.writeUInt16BE(minor << 12);
+  }
+}
+
+export const version16Dot16 = new Version16Dot16();