Use stream for whatever substrem in stream classes

and add a method in order to get the original stream.
When writing an existing stream it'll help to have the original one instead of the filtered one.

src/core/ascii_85_stream.js

@@ -25,7 +25,7 @@ class Ascii85Stream extends DecodeStream {
     }
     super(maybeLength);
 
-    this.str = str;
+    this.stream = str;
     this.dict = str.dict;
     this.input = new Uint8Array(5);
   }
@@ -35,7 +35,7 @@ class Ascii85Stream extends DecodeStream {
     const Z_LOWER_CHAR = 0x7a; // 'z'
     const EOF = -1;
 
-    const str = this.str;
+    const str = this.stream;
 
     let c = str.getByte();
     while (isWhiteSpace(c)) {

src/core/ascii_hex_stream.js

@@ -24,7 +24,7 @@ class AsciiHexStream extends DecodeStream {
     }
     super(maybeLength);
 
-    this.str = str;
+    this.stream = str;
     this.dict = str.dict;
 
     this.firstDigit = -1;
@@ -32,7 +32,7 @@ class AsciiHexStream extends DecodeStream {
 
   readBlock() {
     const UPSTREAM_BLOCK_SIZE = 8000;
-    const bytes = this.str.getBytes(UPSTREAM_BLOCK_SIZE);
+    const bytes = this.stream.getBytes(UPSTREAM_BLOCK_SIZE);
     if (!bytes.length) {
       this.eof = true;
       return;

src/core/base_stream.js

@@ -137,6 +137,10 @@ class BaseStream {
   getBaseStreams() {
     return null;
   }
+
+  getOriginalStream() {
+    return this.stream?.getOriginalStream() || this;
+  }
 }
 
 export { BaseStream };

src/core/ccitt_stream.js

@@ -21,7 +21,7 @@ class CCITTFaxStream extends DecodeStream {
   constructor(str, maybeLength, params) {
     super(maybeLength);
 
-    this.str = str;
+    this.stream = str;
     this.dict = str.dict;
 
     if (!(params instanceof Dict)) {

src/core/decode_stream.js

@@ -129,7 +129,7 @@ class DecodeStream extends BaseStream {
   }
 
   getBaseStreams() {
-    return this.str ? this.str.getBaseStreams() : null;
+    return this.stream ? this.stream.getBaseStreams() : null;
   }
 }
 

src/core/decrypt_stream.js

@@ -21,7 +21,7 @@ class DecryptStream extends DecodeStream {
   constructor(str, maybeLength, decrypt) {
     super(maybeLength);
 
-    this.str = str;
+    this.stream = str;
     this.dict = str.dict;
     this.decrypt = decrypt;
     this.nextChunk = null;
@@ -33,14 +33,14 @@ class DecryptStream extends DecodeStream {
     if (this.initialized) {
       chunk = this.nextChunk;
     } else {
-      chunk = this.str.getBytes(chunkSize);
+      chunk = this.stream.getBytes(chunkSize);
       this.initialized = true;
     }
     if (!chunk?.length) {
       this.eof = true;
       return;
     }
-    this.nextChunk = this.str.getBytes(chunkSize);
+    this.nextChunk = this.stream.getBytes(chunkSize);
     const hasMoreData = this.nextChunk?.length > 0;
 
     const decrypt = this.decrypt;

src/core/flate_stream.js

@@ -125,7 +125,7 @@ class FlateStream extends DecodeStream {
   constructor(str, maybeLength) {
     super(maybeLength);
 
-    this.str = str;
+    this.stream = str;
     this.dict = str.dict;
 
     const cmf = str.getByte();
@@ -161,8 +161,8 @@ class FlateStream extends DecodeStream {
   }
 
   async asyncGetBytes() {
-    this.str.reset();
-    const bytes = this.str.getBytes();
+    this.stream.reset();
+    const bytes = this.stream.getBytes();
 
     try {
       const { readable, writable } = new DecompressionStream("deflate");
@@ -200,11 +200,11 @@ class FlateStream extends DecodeStream {
       // decoder.
       // We already get the bytes from the underlying stream, so we just reuse
       // them to avoid get them again.
-      this.str = new Stream(
+      this.stream = new Stream(
         bytes,
         2 /* = header size (see ctor) */,
         bytes.length,
-        this.str.dict
+        this.stream.dict
       );
       this.reset();
       return null;
@@ -216,7 +216,7 @@ class FlateStream extends DecodeStream {
   }
 
   getBits(bits) {
-    const str = this.str;
+    const str = this.stream;
     let codeSize = this.codeSize;
     let codeBuf = this.codeBuf;
 
@@ -236,7 +236,7 @@ class FlateStream extends DecodeStream {
   }
 
   getCode(table) {
-    const str = this.str;
+    const str = this.stream;
     const codes = table[0];
     const maxLen = table[1];
     let codeSize = this.codeSize;
@@ -312,7 +312,7 @@ class FlateStream extends DecodeStream {
 
   readBlock() {
     let buffer, hdr, len;
-    const str = this.str;
+    const str = this.stream;
     // read block header
     try {
       hdr = this.getBits(3);

src/core/lzw_stream.js

@@ -19,7 +19,7 @@ class LZWStream extends DecodeStream {
   constructor(str, maybeLength, earlyChange) {
     super(maybeLength);
 
-    this.str = str;
+    this.stream = str;
     this.dict = str.dict;
     this.cachedData = 0;
     this.bitsCached = 0;
@@ -46,7 +46,7 @@ class LZWStream extends DecodeStream {
     let bitsCached = this.bitsCached;
     let cachedData = this.cachedData;
     while (bitsCached < n) {
-      const c = this.str.getByte();
+      const c = this.stream.getByte();
       if (c === -1) {
         this.eof = true;
         return null;

src/core/predictor_stream.js

@@ -35,7 +35,7 @@ class PredictorStream extends DecodeStream {
 
     this.readBlock = predictor === 2 ? this.readBlockTiff : this.readBlockPng;
 
-    this.str = str;
+    this.stream = str;
     this.dict = str.dict;
 
     const colors = (this.colors = params.get("Colors") || 1);
@@ -57,7 +57,7 @@ class PredictorStream extends DecodeStream {
     const bits = this.bits;
     const colors = this.colors;
 
-    const rawBytes = this.str.getBytes(rowBytes);
+    const rawBytes = this.stream.getBytes(rowBytes);
     this.eof = !rawBytes.length;
     if (this.eof) {
       return;
@@ -138,8 +138,8 @@ class PredictorStream extends DecodeStream {
     const rowBytes = this.rowBytes;
     const pixBytes = this.pixBytes;
 
-    const predictor = this.str.getByte();
-    const rawBytes = this.str.getBytes(rowBytes);
+    const predictor = this.stream.getByte();
+    const rawBytes = this.stream.getBytes(rowBytes);
     this.eof = !rawBytes.length;
     if (this.eof) {
       return;

src/core/run_length_stream.js

@@ -19,7 +19,7 @@ class RunLengthStream extends DecodeStream {
   constructor(str, maybeLength) {
     super(maybeLength);
 
-    this.str = str;
+    this.stream = str;
     this.dict = str.dict;
   }
 
@@ -28,7 +28,7 @@ class RunLengthStream extends DecodeStream {
     // and amount of bytes to repeat/copy: n = 0 through 127 - copy next n bytes
     // (in addition to the second byte from the header), n = 129 through 255 -
     // duplicate the second byte from the header (257 - n) times, n = 128 - end.
-    const repeatHeader = this.str.getBytes(2);
+    const repeatHeader = this.stream.getBytes(2);
     if (!repeatHeader || repeatHeader.length < 2 || repeatHeader[0] === 128) {
       this.eof = true;
       return;
@@ -42,7 +42,7 @@ class RunLengthStream extends DecodeStream {
       buffer = this.ensureBuffer(bufferLength + n + 1);
       buffer[bufferLength++] = repeatHeader[1];
       if (n > 0) {
-        const source = this.str.getBytes(n);
+        const source = this.stream.getBytes(n);
         buffer.set(source, bufferLength);
         bufferLength += n;
       }