Merge pull request #13303 from Snuffleupagus/BaseStream

Add an abstract base-class, which all the various Stream implementations inherit from

src/core/ascii_85_stream.js

@@ -0,0 +1,98 @@
+/* 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 { DecodeStream } from "./decode_stream.js";
+import { isWhiteSpace } from "./core_utils.js";
+
+class Ascii85Stream extends DecodeStream {
+  constructor(str, maybeLength) {
+    // Most streams increase in size when decoded, but Ascii85 streams
+    // typically shrink by ~20%.
+    if (maybeLength) {
+      maybeLength = 0.8 * maybeLength;
+    }
+    super(maybeLength);
+
+    this.str = str;
+    this.dict = str.dict;
+    this.input = new Uint8Array(5);
+  }
+
+  readBlock() {
+    const TILDA_CHAR = 0x7e; // '~'
+    const Z_LOWER_CHAR = 0x7a; // 'z'
+    const EOF = -1;
+
+    const str = this.str;
+
+    let c = str.getByte();
+    while (isWhiteSpace(c)) {
+      c = str.getByte();
+    }
+
+    if (c === EOF || c === TILDA_CHAR) {
+      this.eof = true;
+      return;
+    }
+
+    const bufferLength = this.bufferLength;
+    let buffer, i;
+
+    // special code for z
+    if (c === Z_LOWER_CHAR) {
+      buffer = this.ensureBuffer(bufferLength + 4);
+      for (i = 0; i < 4; ++i) {
+        buffer[bufferLength + i] = 0;
+      }
+      this.bufferLength += 4;
+    } else {
+      const input = this.input;
+      input[0] = c;
+      for (i = 1; i < 5; ++i) {
+        c = str.getByte();
+        while (isWhiteSpace(c)) {
+          c = str.getByte();
+        }
+
+        input[i] = c;
+
+        if (c === EOF || c === TILDA_CHAR) {
+          break;
+        }
+      }
+      buffer = this.ensureBuffer(bufferLength + i - 1);
+      this.bufferLength += i - 1;
+
+      // partial ending;
+      if (i < 5) {
+        for (; i < 5; ++i) {
+          input[i] = 0x21 + 84;
+        }
+        this.eof = true;
+      }
+      let t = 0;
+      for (i = 0; i < 5; ++i) {
+        t = t * 85 + (input[i] - 0x21);
+      }
+
+      for (i = 3; i >= 0; --i) {
+        buffer[bufferLength + i] = t & 0xff;
+        t >>= 8;
+      }
+    }
+  }
+}
+
+export { Ascii85Stream };

src/core/ascii_hex_stream.js

@@ -0,0 +1,79 @@
+/* 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 { DecodeStream } from "./decode_stream.js";
+
+class AsciiHexStream extends DecodeStream {
+  constructor(str, maybeLength) {
+    // Most streams increase in size when decoded, but AsciiHex streams shrink
+    // by 50%.
+    if (maybeLength) {
+      maybeLength = 0.5 * maybeLength;
+    }
+    super(maybeLength);
+
+    this.str = str;
+    this.dict = str.dict;
+
+    this.firstDigit = -1;
+  }
+
+  readBlock() {
+    const UPSTREAM_BLOCK_SIZE = 8000;
+    const bytes = this.str.getBytes(UPSTREAM_BLOCK_SIZE);
+    if (!bytes.length) {
+      this.eof = true;
+      return;
+    }
+
+    const maxDecodeLength = (bytes.length + 1) >> 1;
+    const buffer = this.ensureBuffer(this.bufferLength + maxDecodeLength);
+    let bufferLength = this.bufferLength;
+
+    let firstDigit = this.firstDigit;
+    for (const ch of bytes) {
+      let digit;
+      if (ch >= /* '0' = */ 0x30 && ch <= /* '9' = */ 0x39) {
+        digit = ch & 0x0f;
+      } else if (
+        (ch >= /* 'A' = */ 0x41 && ch <= /* 'Z' = */ 0x46) ||
+        (ch >= /* 'a' = */ 0x61 && ch <= /* 'z' = */ 0x66)
+      ) {
+        digit = (ch & 0x0f) + 9;
+      } else if (ch === /* '>' = */ 0x3e) {
+        this.eof = true;
+        break;
+      } else {
+        // Probably whitespace, ignoring.
+        continue;
+      }
+      if (firstDigit < 0) {
+        firstDigit = digit;
+      } else {
+        buffer[bufferLength++] = (firstDigit << 4) | digit;
+        firstDigit = -1;
+      }
+    }
+    if (firstDigit >= 0 && this.eof) {
+      // incomplete byte
+      buffer[bufferLength++] = firstDigit << 4;
+      firstDigit = -1;
+    }
+    this.firstDigit = firstDigit;
+    this.bufferLength = bufferLength;
+  }
+}
+
+export { AsciiHexStream };

src/core/base_stream.js

@@ -0,0 +1,106 @@
+/* Copyright 2021 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 { shadow, unreachable } from "../shared/util.js";
+
+class BaseStream {
+  constructor() {
+    if (this.constructor === BaseStream) {
+      unreachable("Cannot initialize BaseStream.");
+    }
+  }
+
+  // eslint-disable-next-line getter-return
+  get length() {
+    unreachable("Abstract getter `length` accessed");
+  }
+
+  // eslint-disable-next-line getter-return
+  get isEmpty() {
+    unreachable("Abstract getter `isEmpty` accessed");
+  }
+
+  get isDataLoaded() {
+    return shadow(this, "isDataLoaded", true);
+  }
+
+  getByte() {
+    unreachable("Abstract method `getByte` called");
+  }
+
+  getBytes(length, forceClamped = false) {
+    unreachable("Abstract method `getBytes` called");
+  }
+
+  peekByte() {
+    const peekedByte = this.getByte();
+    if (peekedByte !== -1) {
+      this.pos--;
+    }
+    return peekedByte;
+  }
+
+  peekBytes(length, forceClamped = false) {
+    const bytes = this.getBytes(length, forceClamped);
+    this.pos -= bytes.length;
+    return bytes;
+  }
+
+  getUint16() {
+    const b0 = this.getByte();
+    const b1 = this.getByte();
+    if (b0 === -1 || b1 === -1) {
+      return -1;
+    }
+    return (b0 << 8) + b1;
+  }
+
+  getInt32() {
+    const b0 = this.getByte();
+    const b1 = this.getByte();
+    const b2 = this.getByte();
+    const b3 = this.getByte();
+    return (b0 << 24) + (b1 << 16) + (b2 << 8) + b3;
+  }
+
+  getByteRange(begin, end) {
+    unreachable("Abstract method `getByteRange` called");
+  }
+
+  skip(n) {
+    this.pos += n || 1;
+  }
+
+  reset() {
+    unreachable("Abstract method `reset` called");
+  }
+
+  moveStart() {
+    unreachable("Abstract method `moveStart` called");
+  }
+
+  makeSubStream(start, length, dict = null) {
+    unreachable("Abstract method `makeSubStream` called");
+  }
+
+  /**
+   * @returns {Array | null}
+   */
+  getBaseStreams() {
+    return null;
+  }
+}
+
+export { BaseStream };

src/core/ccitt_stream.js

@@ -15,7 +15,7 @@
 
 import { Dict, isDict } from "./primitives.js";
 import { CCITTFaxDecoder } from "./ccitt.js";
-import { DecodeStream } from "./stream.js";
+import { DecodeStream } from "./decode_stream.js";
 
 class CCITTFaxStream extends DecodeStream {
   constructor(str, maybeLength, params) {