From c077b22410037559d0e8af9fedc6f0971a67b9ab Mon Sep 17 00:00:00 2001
From: n1474335 <n1474335@gmail.com>
Date: Thu, 10 Jan 2019 17:30:52 +0000
Subject: [PATCH] Stream.readBits() method implemented. Unfinished.

---
 src/core/lib/FileSignatures.mjs | 12 +++++-------
 src/core/lib/Stream.mjs         |  7 +++----
 2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/src/core/lib/FileSignatures.mjs b/src/core/lib/FileSignatures.mjs
index b0eb5884..d8d97a2b 100644
--- a/src/core/lib/FileSignatures.mjs
+++ b/src/core/lib/FileSignatures.mjs
@@ -1438,10 +1438,8 @@ export function extractGZIP(bytes, offset) {
 
     while (!finalBlock) {
         // Read header
-        const blockHeader = stream.readBits(3);
-
-        finalBlock = blockHeader & 0x1;
-        const blockType = blockHeader & 0x6;
+        finalBlock = stream.readBits(1);
+        const blockType = stream.readBits(2);
 
         if (blockType === 0) {
             // No compression
@@ -1451,23 +1449,23 @@ export function extractGZIP(bytes, offset) {
             stream.moveForwardsBy(2 + blockLength);
         } else if (blockType === 1) {
             // Fixed Huffman
+            console.log("Fixed Huffman");
 
         } else if (blockType === 2) {
             // Dynamic Huffman
-
+            console.log("Dynamic Huffman");
         } else {
             throw new Error("Invalid block type");
             break;
         }
     }
 
-
     /* FOOTER */
 
     // Skip over checksum and size of original uncompressed input
     stream.moveForwardsBy(8);
 
-    console.log(stream.position);
+    console.log("Ending at " + stream.position);
 
     return stream.carve();
 }
diff --git a/src/core/lib/Stream.mjs b/src/core/lib/Stream.mjs
index 2b5d8d09..886d4589 100644
--- a/src/core/lib/Stream.mjs
+++ b/src/core/lib/Stream.mjs
@@ -106,7 +106,7 @@ export default class Stream {
             bitBufLen = 0;
 
         // Add remaining bits from current byte
-        bitBuf = this.bytes[this.position++] & bitMask(this.bitPos);
+        bitBuf = (this.bytes[this.position++] & bitMask(this.bitPos)) >>> this.bitPos;
         bitBufLen = 8 - this.bitPos;
         this.bitPos = 0;
 
@@ -119,7 +119,7 @@ export default class Stream {
         // Reverse back to numBits
         if (bitBufLen > numBits) {
             const excess = bitBufLen - numBits;
-            bitBuf >>>= excess;
+            bitBuf &= (1 << numBits) - 1;
             bitBufLen -= excess;
             this.position--;
             this.bitPos = 8 - excess;
@@ -134,11 +134,10 @@ export default class Stream {
          * @returns {number} The bit mask
          */
         function bitMask(bitPos) {
-            return (1 << (8 - bitPos)) - 1;
+            return 256 - (1 << bitPos);
         }
     }
 
-
     /**
      * Consume the stream until we reach the specified byte or sequence of bytes.
      *