diff --git a/src/core/binary_cmap.js b/src/core/binary_cmap.js
new file mode 100644
index 000000000..0a160eed9
--- /dev/null
+++ b/src/core/binary_cmap.js
@@ -0,0 +1,326 @@
+/* Copyright 2012 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { FormatError } from "../shared/util.js";
+
+function hexToInt(a, size) {
+  let n = 0;
+  for (let i = 0; i <= size; i++) {
+    n = (n << 8) | a[i];
+  }
+  return n >>> 0;
+}
+
+function hexToStr(a, size) {
+  // This code is hot. Special-case some common values to avoid creating an
+  // object with subarray().
+  if (size === 1) {
+    return String.fromCharCode(a[0], a[1]);
+  }
+  if (size === 3) {
+    return String.fromCharCode(a[0], a[1], a[2], a[3]);
+  }
+  return String.fromCharCode.apply(null, a.subarray(0, size + 1));
+}
+
+function addHex(a, b, size) {
+  let c = 0;
+  for (let i = size; i >= 0; i--) {
+    c += a[i] + b[i];
+    a[i] = c & 255;
+    c >>= 8;
+  }
+}
+
+function incHex(a, size) {
+  let c = 1;
+  for (let i = size; i >= 0 && c > 0; i--) {
+    c += a[i];
+    a[i] = c & 255;
+    c >>= 8;
+  }
+}
+
+const MAX_NUM_SIZE = 16;
+const MAX_ENCODED_NUM_SIZE = 19; // ceil(MAX_NUM_SIZE * 7 / 8)
+
+class BinaryCMapStream {
+  constructor(data) {
+    this.buffer = data;
+    this.pos = 0;
+    this.end = data.length;
+    this.tmpBuf = new Uint8Array(MAX_ENCODED_NUM_SIZE);
+  }
+
+  readByte() {
+    if (this.pos >= this.end) {
+      return -1;
+    }
+    return this.buffer[this.pos++];
+  }
+
+  readNumber() {
+    let n = 0;
+    let last;
+    do {
+      const b = this.readByte();
+      if (b < 0) {
+        throw new FormatError("unexpected EOF in bcmap");
+      }
+      last = !(b & 0x80);
+      n = (n << 7) | (b & 0x7f);
+    } while (!last);
+    return n;
+  }
+
+  readSigned() {
+    const n = this.readNumber();
+    return n & 1 ? ~(n >>> 1) : n >>> 1;
+  }
+
+  readHex(num, size) {
+    num.set(this.buffer.subarray(this.pos, this.pos + size + 1));
+    this.pos += size + 1;
+  }
+
+  readHexNumber(num, size) {
+    let last;
+    const stack = this.tmpBuf;
+    let sp = 0;
+    do {
+      const b = this.readByte();
+      if (b < 0) {
+        throw new FormatError("unexpected EOF in bcmap");
+      }
+      last = !(b & 0x80);
+      stack[sp++] = b & 0x7f;
+    } while (!last);
+    let i = size,
+      buffer = 0,
+      bufferSize = 0;
+    while (i >= 0) {
+      while (bufferSize < 8 && stack.length > 0) {
+        buffer |= stack[--sp] << bufferSize;
+        bufferSize += 7;
+      }
+      num[i] = buffer & 255;
+      i--;
+      buffer >>= 8;
+      bufferSize -= 8;
+    }
+  }
+
+  readHexSigned(num, size) {
+    this.readHexNumber(num, size);
+    const sign = num[size] & 1 ? 255 : 0;
+    let c = 0;
+    for (let i = 0; i <= size; i++) {
+      c = ((c & 1) << 8) | num[i];
+      num[i] = (c >> 1) ^ sign;
+    }
+  }
+
+  readString() {
+    const len = this.readNumber();
+    let s = "";
+    for (let i = 0; i < len; i++) {
+      s += String.fromCharCode(this.readNumber());
+    }
+    return s;
+  }
+}
+
+class BinaryCMapReader {
+  async process(data, cMap, extend) {
+    const stream = new BinaryCMapStream(data);
+    const header = stream.readByte();
+    cMap.vertical = !!(header & 1);
+
+    let useCMap = null;
+    const start = new Uint8Array(MAX_NUM_SIZE);
+    const end = new Uint8Array(MAX_NUM_SIZE);
+    const char = new Uint8Array(MAX_NUM_SIZE);
+    const charCode = new Uint8Array(MAX_NUM_SIZE);
+    const tmp = new Uint8Array(MAX_NUM_SIZE);
+    let code;
+
+    let b;
+    while ((b = stream.readByte()) >= 0) {
+      const type = b >> 5;
+      if (type === 7) {
+        // metadata, e.g. comment or usecmap
+        switch (b & 0x1f) {
+          case 0:
+            stream.readString(); // skipping comment
+            break;
+          case 1:
+            useCMap = stream.readString();
+            break;
+        }
+        continue;
+      }
+      const sequence = !!(b & 0x10);
+      const dataSize = b & 15;
+
+      if (dataSize + 1 > MAX_NUM_SIZE) {
+        throw new Error("BinaryCMapReader.process: Invalid dataSize.");
+      }
+
+      const ucs2DataSize = 1;
+      const subitemsCount = stream.readNumber();
+      switch (type) {
+        case 0: // codespacerange
+          stream.readHex(start, dataSize);
+          stream.readHexNumber(end, dataSize);
+          addHex(end, start, dataSize);
+          cMap.addCodespaceRange(
+            dataSize + 1,
+            hexToInt(start, dataSize),
+            hexToInt(end, dataSize)
+          );
+          for (let i = 1; i < subitemsCount; i++) {
+            incHex(end, dataSize);
+            stream.readHexNumber(start, dataSize);
+            addHex(start, end, dataSize);
+            stream.readHexNumber(end, dataSize);
+            addHex(end, start, dataSize);
+            cMap.addCodespaceRange(
+              dataSize + 1,
+              hexToInt(start, dataSize),
+              hexToInt(end, dataSize)
+            );
+          }
+          break;
+        case 1: // notdefrange
+          stream.readHex(start, dataSize);
+          stream.readHexNumber(end, dataSize);
+          addHex(end, start, dataSize);
+          stream.readNumber(); // code
+          // undefined range, skipping
+          for (let i = 1; i < subitemsCount; i++) {
+            incHex(end, dataSize);
+            stream.readHexNumber(start, dataSize);
+            addHex(start, end, dataSize);
+            stream.readHexNumber(end, dataSize);
+            addHex(end, start, dataSize);
+            stream.readNumber(); // code
+            // nop
+          }
+          break;
+        case 2: // cidchar
+          stream.readHex(char, dataSize);
+          code = stream.readNumber();
+          cMap.mapOne(hexToInt(char, dataSize), code);
+          for (let i = 1; i < subitemsCount; i++) {
+            incHex(char, dataSize);
+            if (!sequence) {
+              stream.readHexNumber(tmp, dataSize);
+              addHex(char, tmp, dataSize);
+            }
+            code = stream.readSigned() + (code + 1);
+            cMap.mapOne(hexToInt(char, dataSize), code);
+          }
+          break;
+        case 3: // cidrange
+          stream.readHex(start, dataSize);
+          stream.readHexNumber(end, dataSize);
+          addHex(end, start, dataSize);
+          code = stream.readNumber();
+          cMap.mapCidRange(
+            hexToInt(start, dataSize),
+            hexToInt(end, dataSize),
+            code
+          );
+          for (let i = 1; i < subitemsCount; i++) {
+            incHex(end, dataSize);
+            if (!sequence) {
+              stream.readHexNumber(start, dataSize);
+              addHex(start, end, dataSize);
+            } else {
+              start.set(end);
+            }
+            stream.readHexNumber(end, dataSize);
+            addHex(end, start, dataSize);
+            code = stream.readNumber();
+            cMap.mapCidRange(
+              hexToInt(start, dataSize),
+              hexToInt(end, dataSize),
+              code
+            );
+          }
+          break;
+        case 4: // bfchar
+          stream.readHex(char, ucs2DataSize);
+          stream.readHex(charCode, dataSize);
+          cMap.mapOne(
+            hexToInt(char, ucs2DataSize),
+            hexToStr(charCode, dataSize)
+          );
+          for (let i = 1; i < subitemsCount; i++) {
+            incHex(char, ucs2DataSize);
+            if (!sequence) {
+              stream.readHexNumber(tmp, ucs2DataSize);
+              addHex(char, tmp, ucs2DataSize);
+            }
+            incHex(charCode, dataSize);
+            stream.readHexSigned(tmp, dataSize);
+            addHex(charCode, tmp, dataSize);
+            cMap.mapOne(
+              hexToInt(char, ucs2DataSize),
+              hexToStr(charCode, dataSize)
+            );
+          }
+          break;
+        case 5: // bfrange
+          stream.readHex(start, ucs2DataSize);
+          stream.readHexNumber(end, ucs2DataSize);
+          addHex(end, start, ucs2DataSize);
+          stream.readHex(charCode, dataSize);
+          cMap.mapBfRange(
+            hexToInt(start, ucs2DataSize),
+            hexToInt(end, ucs2DataSize),
+            hexToStr(charCode, dataSize)
+          );
+          for (let i = 1; i < subitemsCount; i++) {
+            incHex(end, ucs2DataSize);
+            if (!sequence) {
+              stream.readHexNumber(start, ucs2DataSize);
+              addHex(start, end, ucs2DataSize);
+            } else {
+              start.set(end);
+            }
+            stream.readHexNumber(end, ucs2DataSize);
+            addHex(end, start, ucs2DataSize);
+            stream.readHex(charCode, dataSize);
+            cMap.mapBfRange(
+              hexToInt(start, ucs2DataSize),
+              hexToInt(end, ucs2DataSize),
+              hexToStr(charCode, dataSize)
+            );
+          }
+          break;
+        default:
+          throw new Error(`BinaryCMapReader.process - unknown type: ${type}`);
+      }
+    }
+
+    if (useCMap) {
+      return extend(useCMap);
+    }
+    return cMap;
+  }
+}
+
+export { BinaryCMapReader };
diff --git a/src/core/cmap.js b/src/core/cmap.js
index 5cde7d29f..1f50a9227 100644
--- a/src/core/cmap.js
+++ b/src/core/cmap.js
@@ -21,6 +21,7 @@ import {
 } from "../shared/util.js";
 import { Cmd, EOF, isCmd, Name } from "./primitives.js";
 import { BaseStream } from "./base_stream.js";
+import { BinaryCMapReader } from "./binary_cmap.js";
 import { Lexer } from "./parser.js";
 import { MissingDataException } from "./core_utils.js";
 import { Stream } from "./stream.js";
@@ -443,319 +444,6 @@ class IdentityCMap extends CMap {
   }
 }
 
-const BinaryCMapReader = (function BinaryCMapReaderClosure() {
-  function hexToInt(a, size) {
-    let n = 0;
-    for (let i = 0; i <= size; i++) {
-      n = (n << 8) | a[i];
-    }
-    return n >>> 0;
-  }
-
-  function hexToStr(a, size) {
-    // This code is hot. Special-case some common values to avoid creating an
-    // object with subarray().
-    if (size === 1) {
-      return String.fromCharCode(a[0], a[1]);
-    }
-    if (size === 3) {
-      return String.fromCharCode(a[0], a[1], a[2], a[3]);
-    }
-    return String.fromCharCode.apply(null, a.subarray(0, size + 1));
-  }
-
-  function addHex(a, b, size) {
-    let c = 0;
-    for (let i = size; i >= 0; i--) {
-      c += a[i] + b[i];
-      a[i] = c & 255;
-      c >>= 8;
-    }
-  }
-
-  function incHex(a, size) {
-    let c = 1;
-    for (let i = size; i >= 0 && c > 0; i--) {
-      c += a[i];
-      a[i] = c & 255;
-      c >>= 8;
-    }
-  }
-
-  const MAX_NUM_SIZE = 16;
-  const MAX_ENCODED_NUM_SIZE = 19; // ceil(MAX_NUM_SIZE * 7 / 8)
-
-  class BinaryCMapStream {
-    constructor(data) {
-      this.buffer = data;
-      this.pos = 0;
-      this.end = data.length;
-      this.tmpBuf = new Uint8Array(MAX_ENCODED_NUM_SIZE);
-    }
-
-    readByte() {
-      if (this.pos >= this.end) {
-        return -1;
-      }
-      return this.buffer[this.pos++];
-    }
-
-    readNumber() {
-      let n = 0;
-      let last;
-      do {
-        const b = this.readByte();
-        if (b < 0) {
-          throw new FormatError("unexpected EOF in bcmap");
-        }
-        last = !(b & 0x80);
-        n = (n << 7) | (b & 0x7f);
-      } while (!last);
-      return n;
-    }
-
-    readSigned() {
-      const n = this.readNumber();
-      return n & 1 ? ~(n >>> 1) : n >>> 1;
-    }
-
-    readHex(num, size) {
-      num.set(this.buffer.subarray(this.pos, this.pos + size + 1));
-      this.pos += size + 1;
-    }
-
-    readHexNumber(num, size) {
-      let last;
-      const stack = this.tmpBuf;
-      let sp = 0;
-      do {
-        const b = this.readByte();
-        if (b < 0) {
-          throw new FormatError("unexpected EOF in bcmap");
-        }
-        last = !(b & 0x80);
-        stack[sp++] = b & 0x7f;
-      } while (!last);
-      let i = size,
-        buffer = 0,
-        bufferSize = 0;
-      while (i >= 0) {
-        while (bufferSize < 8 && stack.length > 0) {
-          buffer |= stack[--sp] << bufferSize;
-          bufferSize += 7;
-        }
-        num[i] = buffer & 255;
-        i--;
-        buffer >>= 8;
-        bufferSize -= 8;
-      }
-    }
-
-    readHexSigned(num, size) {
-      this.readHexNumber(num, size);
-      const sign = num[size] & 1 ? 255 : 0;
-      let c = 0;
-      for (let i = 0; i <= size; i++) {
-        c = ((c & 1) << 8) | num[i];
-        num[i] = (c >> 1) ^ sign;
-      }
-    }
-
-    readString() {
-      const len = this.readNumber();
-      let s = "";
-      for (let i = 0; i < len; i++) {
-        s += String.fromCharCode(this.readNumber());
-      }
-      return s;
-    }
-  }
-
-  // eslint-disable-next-line no-shadow
-  class BinaryCMapReader {
-    async process(data, cMap, extend) {
-      const stream = new BinaryCMapStream(data);
-      const header = stream.readByte();
-      cMap.vertical = !!(header & 1);
-
-      let useCMap = null;
-      const start = new Uint8Array(MAX_NUM_SIZE);
-      const end = new Uint8Array(MAX_NUM_SIZE);
-      const char = new Uint8Array(MAX_NUM_SIZE);
-      const charCode = new Uint8Array(MAX_NUM_SIZE);
-      const tmp = new Uint8Array(MAX_NUM_SIZE);
-      let code;
-
-      let b;
-      while ((b = stream.readByte()) >= 0) {
-        const type = b >> 5;
-        if (type === 7) {
-          // metadata, e.g. comment or usecmap
-          switch (b & 0x1f) {
-            case 0:
-              stream.readString(); // skipping comment
-              break;
-            case 1:
-              useCMap = stream.readString();
-              break;
-          }
-          continue;
-        }
-        const sequence = !!(b & 0x10);
-        const dataSize = b & 15;
-
-        if (dataSize + 1 > MAX_NUM_SIZE) {
-          throw new Error("BinaryCMapReader.process: Invalid dataSize.");
-        }
-
-        const ucs2DataSize = 1;
-        const subitemsCount = stream.readNumber();
-        switch (type) {
-          case 0: // codespacerange
-            stream.readHex(start, dataSize);
-            stream.readHexNumber(end, dataSize);
-            addHex(end, start, dataSize);
-            cMap.addCodespaceRange(
-              dataSize + 1,
-              hexToInt(start, dataSize),
-              hexToInt(end, dataSize)
-            );
-            for (let i = 1; i < subitemsCount; i++) {
-              incHex(end, dataSize);
-              stream.readHexNumber(start, dataSize);
-              addHex(start, end, dataSize);
-              stream.readHexNumber(end, dataSize);
-              addHex(end, start, dataSize);
-              cMap.addCodespaceRange(
-                dataSize + 1,
-                hexToInt(start, dataSize),
-                hexToInt(end, dataSize)
-              );
-            }
-            break;
-          case 1: // notdefrange
-            stream.readHex(start, dataSize);
-            stream.readHexNumber(end, dataSize);
-            addHex(end, start, dataSize);
-            stream.readNumber(); // code
-            // undefined range, skipping
-            for (let i = 1; i < subitemsCount; i++) {
-              incHex(end, dataSize);
-              stream.readHexNumber(start, dataSize);
-              addHex(start, end, dataSize);
-              stream.readHexNumber(end, dataSize);
-              addHex(end, start, dataSize);
-              stream.readNumber(); // code
-              // nop
-            }
-            break;
-          case 2: // cidchar
-            stream.readHex(char, dataSize);
-            code = stream.readNumber();
-            cMap.mapOne(hexToInt(char, dataSize), code);
-            for (let i = 1; i < subitemsCount; i++) {
-              incHex(char, dataSize);
-              if (!sequence) {
-                stream.readHexNumber(tmp, dataSize);
-                addHex(char, tmp, dataSize);
-              }
-              code = stream.readSigned() + (code + 1);
-              cMap.mapOne(hexToInt(char, dataSize), code);
-            }
-            break;
-          case 3: // cidrange
-            stream.readHex(start, dataSize);
-            stream.readHexNumber(end, dataSize);
-            addHex(end, start, dataSize);
-            code = stream.readNumber();
-            cMap.mapCidRange(
-              hexToInt(start, dataSize),
-              hexToInt(end, dataSize),
-              code
-            );
-            for (let i = 1; i < subitemsCount; i++) {
-              incHex(end, dataSize);
-              if (!sequence) {
-                stream.readHexNumber(start, dataSize);
-                addHex(start, end, dataSize);
-              } else {
-                start.set(end);
-              }
-              stream.readHexNumber(end, dataSize);
-              addHex(end, start, dataSize);
-              code = stream.readNumber();
-              cMap.mapCidRange(
-                hexToInt(start, dataSize),
-                hexToInt(end, dataSize),
-                code
-              );
-            }
-            break;
-          case 4: // bfchar
-            stream.readHex(char, ucs2DataSize);
-            stream.readHex(charCode, dataSize);
-            cMap.mapOne(
-              hexToInt(char, ucs2DataSize),
-              hexToStr(charCode, dataSize)
-            );
-            for (let i = 1; i < subitemsCount; i++) {
-              incHex(char, ucs2DataSize);
-              if (!sequence) {
-                stream.readHexNumber(tmp, ucs2DataSize);
-                addHex(char, tmp, ucs2DataSize);
-              }
-              incHex(charCode, dataSize);
-              stream.readHexSigned(tmp, dataSize);
-              addHex(charCode, tmp, dataSize);
-              cMap.mapOne(
-                hexToInt(char, ucs2DataSize),
-                hexToStr(charCode, dataSize)
-              );
-            }
-            break;
-          case 5: // bfrange
-            stream.readHex(start, ucs2DataSize);
-            stream.readHexNumber(end, ucs2DataSize);
-            addHex(end, start, ucs2DataSize);
-            stream.readHex(charCode, dataSize);
-            cMap.mapBfRange(
-              hexToInt(start, ucs2DataSize),
-              hexToInt(end, ucs2DataSize),
-              hexToStr(charCode, dataSize)
-            );
-            for (let i = 1; i < subitemsCount; i++) {
-              incHex(end, ucs2DataSize);
-              if (!sequence) {
-                stream.readHexNumber(start, ucs2DataSize);
-                addHex(start, end, ucs2DataSize);
-              } else {
-                start.set(end);
-              }
-              stream.readHexNumber(end, ucs2DataSize);
-              addHex(end, start, ucs2DataSize);
-              stream.readHex(charCode, dataSize);
-              cMap.mapBfRange(
-                hexToInt(start, ucs2DataSize),
-                hexToInt(end, ucs2DataSize),
-                hexToStr(charCode, dataSize)
-              );
-            }
-            break;
-          default:
-            throw new Error(`BinaryCMapReader.process - unknown type: ${type}`);
-        }
-      }
-
-      if (useCMap) {
-        return extend(useCMap);
-      }
-      return cMap;
-    }
-  }
-
-  return BinaryCMapReader;
-})();
-
 const CMapFactory = (function CMapFactoryClosure() {
   function strToInt(str) {
     let a = 0;