Merge pull request #21053 from Snuffleupagus/CFFCompiler-TypedArray

Reduce allocations when compiling CFF fonts

src/core/cff_parser.js

@@ -228,7 +228,7 @@ class CFFParser {
 
   parse() {
     const properties = this.properties;
-    const cff = new CFF();
+    const cff = new CFF(this.bytes.length);
     this.cff = cff;
 
     // The first five sections must be in order, all the others are reached
@@ -1017,6 +1017,10 @@ class CFF {
 
   charStringCount = 0;
 
+  constructor(rawFileLength = 0) {
+    this.rawFileLength = rawFileLength;
+  }
+
   duplicateFirstGlyph() {
     // Browsers will not display a glyph at position 0. Typically glyph 0 is
     // notdef, but a number of fonts put a valid glyph there so it must be
@@ -1372,6 +1376,57 @@ class CFFOffsetTracker {
   }
 }
 
+class CompilerOutput {
+  #buf;
+
+  #bufLength = 1024;
+
+  #pos = 0;
+
+  constructor(minLength) {
+    // Note: Usually the compiled size is smaller than the initial data,
+    //       however in some cases it may increase slightly.
+    this.#initBuf(minLength);
+  }
+
+  #initBuf(minLength) {
+    // Compute the first power of two that is as big as the `minLength`.
+    while (this.#bufLength < minLength) {
+      this.#bufLength *= 2;
+    }
+    const newBuf = new Uint8Array(this.#bufLength);
+
+    if (this.#buf) {
+      newBuf.set(this.#buf, 0);
+    }
+    this.#buf = newBuf;
+  }
+
+  get data() {
+    return this.#buf.subarray(0, this.#pos);
+  }
+
+  get finalData() {
+    const data = this.#buf.slice(0, this.#pos);
+    this.#buf = null;
+    return data;
+  }
+
+  get length() {
+    return this.#pos;
+  }
+
+  add(data) {
+    const newPos = this.#pos + data.length;
+    if (newPos > this.#bufLength) {
+      // It should be very rare that the buffer needs to grow.
+      this.#initBuf(newPos);
+    }
+    this.#buf.set(data, this.#pos);
+    this.#pos = newPos;
+  }
+}
+
 // Takes a CFF and converts it to the binary representation.
 class CFFCompiler {
   constructor(cff) {
@@ -1380,21 +1435,7 @@ class CFFCompiler {
 
   compile() {
     const cff = this.cff;
-    const output = {
-      data: [],
-      length: 0,
-      add(data) {
-        try {
-          // It's possible to exceed the call stack maximum size when trying
-          // to push too much elements.
-          // In case of failure, we fallback to the `concat` method.
-          this.data.push(...data);
-        } catch {
-          this.data = this.data.concat(data);
-        }
-        this.length = this.data.length;
-      },
-    };
+    const output = new CompilerOutput(cff.rawFileLength);
 
     // Compile the five entries that must be in order.
     const header = this.compileHeader(cff.header);
@@ -1499,7 +1540,7 @@ class CFFCompiler {
     // the sanitizer will bail out. Add a dummy byte to avoid that.
     output.add([0]);
 
-    return output.data;
+    return output.finalData;
   }
 
   encodeNumber(value) {
@@ -1781,7 +1822,7 @@ class CFFCompiler {
     } else {
       const length = 1 + numGlyphsLessNotDef * 2;
       out = new Uint8Array(length);
-      out[0] = 0; // format 0
+      // format 0, skip redundant `out[0] = 0;` assignment.
       let charsetIndex = 0;
       const numCharsets = charset.charset.length;
       let warned = false;
@@ -1802,11 +1843,11 @@ class CFFCompiler {
         out[i + 1] = sid & 0xff;
       }
     }
-    return this.compileTypedArray(out);
+    return out;
   }
 
   compileEncoding(encoding) {
-    return this.compileTypedArray(encoding.raw);
+    return encoding.raw;
   }
 
   compileFDSelect(fdSelect) {
@@ -1847,11 +1888,7 @@ class CFFCompiler {
         out = new Uint8Array(ranges);
         break;
     }
-    return this.compileTypedArray(out);
-  }
-
-  compileTypedArray(data) {
-    return Array.from(data);
+    return out;
   }
 
   compileIndex(index, trackers = []) {
@@ -1915,9 +1952,8 @@ class CFFCompiler {
 
     for (i = 0; i < count; i++) {
       // Notify the tracker where the object will be offset in the data.
-      if (trackers[i]) {
-        trackers[i].offset(data.length);
-      }
+      trackers[i]?.offset(data.length);
+
       data.push(...objects[i]);
     }
     return data;

src/core/opentype_file_builder.js

@@ -35,11 +35,6 @@ function writeData(dest, offset, data) {
     for (let i = 0, ii = data.length; i < ii; i++) {
       dest[offset++] = data.charCodeAt(i) & 0xff;
     }
-  } else {
-    // treating everything else as array
-    for (const num of data) {
-      dest[offset++] = num & 0xff;
-    }
   }
 }
 

src/core/type1_font.js

@@ -153,6 +153,8 @@ function getEexecBlock(stream, suggestedLength) {
  * Type1Font is also a CIDFontType0.
  */
 class Type1Font {
+  #rawFileLength;
+
   constructor(name, file, properties) {
     // Some bad generators embed pfb file as is, we have to strip 6-byte header.
     // Also, length1 and length2 might be off by 6 bytes as well.
@@ -200,6 +202,7 @@ class Type1Font {
     for (const key in data.properties) {
       properties[key] = data.properties[key];
     }
+    this.#rawFileLength = headerBlock.length + eexecBlock.length;
 
     const charstrings = data.charstrings;
     const type2Charstrings = this.getType2Charstrings(charstrings);
@@ -323,7 +326,7 @@ class Type1Font {
   }
 
   wrap(name, glyphs, charstrings, subrs, properties) {
-    const cff = new CFF();
+    const cff = new CFF(this.#rawFileLength);
     cff.header = new CFFHeader(1, 0, 4, 4);
 
     cff.names = [name];

test/unit/cff_parser_spec.js

@@ -430,47 +430,53 @@ describe("CFFCompiler", function () {
     const fdSelect = new CFFFDSelect(0, [3, 2, 1]);
     const c = new CFFCompiler();
     const out = c.compileFDSelect(fdSelect);
-    expect(out).toEqual([
-      0, // format
-      3, // gid: 0 fd 3
-      2, // gid: 1 fd 3
-      1, // gid: 2 fd 3
-    ]);
+    expect(out).toEqual(
+      new Uint8Array([
+        0, // format
+        3, // gid: 0 fd 3
+        2, // gid: 1 fd 3
+        1, // gid: 2 fd 3
+      ])
+    );
   });
 
   it("compiles fdselect format 3", function () {
     const fdSelect = new CFFFDSelect(3, [0, 0, 1, 1]);
     const c = new CFFCompiler();
     const out = c.compileFDSelect(fdSelect);
-    expect(out).toEqual([
-      3, // format
-      0, // nRanges (high)
-      2, // nRanges (low)
-      0, // range struct 0 - first (high)
-      0, // range struct 0 - first (low)
-      0, // range struct 0 - fd
-      0, // range struct 0 - first (high)
-      2, // range struct 0 - first (low)
-      1, // range struct 0 - fd
-      0, // sentinel (high)
-      4, // sentinel (low)
-    ]);
+    expect(out).toEqual(
+      new Uint8Array([
+        3, // format
+        0, // nRanges (high)
+        2, // nRanges (low)
+        0, // range struct 0 - first (high)
+        0, // range struct 0 - first (low)
+        0, // range struct 0 - fd
+        0, // range struct 0 - first (high)
+        2, // range struct 0 - first (low)
+        1, // range struct 0 - fd
+        0, // sentinel (high)
+        4, // sentinel (low)
+      ])
+    );
   });
 
   it("compiles fdselect format 3, single range", function () {
     const fdSelect = new CFFFDSelect(3, [0, 0]);
     const c = new CFFCompiler();
     const out = c.compileFDSelect(fdSelect);
-    expect(out).toEqual([
-      3, // format
-      0, // nRanges (high)
-      1, // nRanges (low)
-      0, // range struct 0 - first (high)
-      0, // range struct 0 - first (low)
-      0, // range struct 0 - fd
-      0, // sentinel (high)
-      2, // sentinel (low)
-    ]);
+    expect(out).toEqual(
+      new Uint8Array([
+        3, // format
+        0, // nRanges (high)
+        1, // nRanges (low)
+        0, // range struct 0 - first (high)
+        0, // range struct 0 - first (low)
+        0, // range struct 0 - fd
+        0, // sentinel (high)
+        2, // sentinel (low)
+      ])
+    );
   });
 
   it("compiles charset of CID font", function () {
@@ -479,13 +485,15 @@ describe("CFFCompiler", function () {
     const numGlyphs = 7;
     const out = c.compileCharset(charset, numGlyphs, new CFFStrings(), true);
     // All CID charsets get turned into a simple format 2.
-    expect(out).toEqual([
-      2, // format
-      0, // cid (high)
-      1, // cid (low)
-      0, // nLeft (high)
-      numGlyphs - 2, // nLeft (low)
-    ]);
+    expect(out).toEqual(
+      new Uint8Array([
+        2, // format
+        0, // cid (high)
+        1, // cid (low)
+        0, // nLeft (high)
+        numGlyphs - 2, // nLeft (low)
+      ])
+    );
   });
 
   it("compiles charset of non CID font", function () {
@@ -494,13 +502,15 @@ describe("CFFCompiler", function () {
     const numGlyphs = 3;
     const out = c.compileCharset(charset, numGlyphs, new CFFStrings(), false);
     // All non-CID fonts use a format 0 charset.
-    expect(out).toEqual([
-      0, // format
-      0, // sid of 'space' (high)
-      1, // sid of 'space' (low)
-      0, // sid of 'exclam' (high)
-      2, // sid of 'exclam' (low)
-    ]);
+    expect(out).toEqual(
+      new Uint8Array([
+        0, // format
+        0, // sid of 'space' (high)
+        1, // sid of 'space' (low)
+        0, // sid of 'exclam' (high)
+        2, // sid of 'exclam' (low)
+      ])
+    );
   });
 
   // TODO a lot more compiler tests