[GitHub] [parquet-mr] theosib-amazon commented on a diff in pull request #960: Performance optimization: Move all LittleEndianDataInputStream functionality into ByteBufferInputStream

[GitBox <gi...@apache.org>]

theosib-amazon commented on code in PR #960:
URL: https://github.com/apache/parquet-mr/pull/960#discussion_r929007342


##########
parquet-common/src/main/java/org/apache/parquet/bytes/ByteBufferInputStream.java:
##########
@@ -157,4 +165,80 @@ public void reset() throws IOException {
   public boolean markSupported() {
     return delegate.markSupported();
   }
+
+  public boolean readBoolean() throws IOException {
+    return readByte() != 0;
+  }
+
+  public byte readByte() throws IOException {
+    return delegate.readByte();
+  }
+
+  public int readUnsignedByte() throws IOException {
+    return delegate.readUnsignedByte();
+  }
+
+  public short readShort() throws IOException {
+    return delegate.readShort();
+  }
+
+  public int readUnsignedShort() throws IOException {
+    return delegate.readUnsignedShort();
+  }
+
+  public int readInt() throws IOException {
+    return delegate.readInt();
+  }
+
+  public long readLong() throws IOException {
+    return delegate.readLong();
+  }
+
+  public float readFloat() throws IOException {
+    return Float.intBitsToFloat(readInt());
+  }
+
+  public double readDouble() throws IOException {
+    return Double.longBitsToDouble(readLong());
+  }
+
+  public int readIntLittleEndianOnThreeBytes() throws IOException {
+    int ch1 = readUnsignedByte();
+    int ch2 = readUnsignedByte();
+    int ch3 = readUnsignedByte();
+    return ((ch3 << 16) + (ch2 << 8) + (ch1 << 0));
+  }
+
+  public int readIntLittleEndianPaddedOnBitWidth(int bitWidth)
+    throws IOException {
+
+    int bytesWidth = BytesUtils.paddedByteCountFromBits(bitWidth);
+    switch (bytesWidth) {
+      case 0:
+        return 0;
+      case 1:
+        return readUnsignedByte();
+      case 2:
+        return readUnsignedShort();
+      case 3:
+        return readIntLittleEndianOnThreeBytes();
+      case 4:
+        return readInt();
+      default:
+        throw new IOException(
+          String.format("Encountered bitWidth (%d) that requires more than 4 bytes", bitWidth));
+    }
+  }
+
+  public int readUnsignedVarInt() throws IOException {

Review Comment:
   Not exactly. The one in BytesUtils calls methods that read one byte at a time. This one can take advantage of faster methods that read whole words at a time. This is a critical-path method, so it's a performance win to eliminate the extra level of abstraction and all the extra overhead fetching individual bytes and shifting.



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