Put the full help before the options

[folly.git] / folly / experimental / BitVectorCoding.h

diff --git a/folly/experimental/BitVectorCoding.h b/folly/experimental/BitVectorCoding.h
index 814b58186e96a9e64d26abcf7a82facc1b02dd70..e2290fcd3d8f35dd25f79c998c09018c87febc4c 100644 (file)
--- a/folly/experimental/BitVectorCoding.h
+++ b/folly/experimental/BitVectorCoding.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2015 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,8 +14,7 @@
  * limitations under the License.
  */
 
-#ifndef FOLLY_EXPERIMENTAL_BIT_VECTOR_CODING_H
-#define FOLLY_EXPERIMENTAL_BIT_VECTOR_CODING_H
+#pragma once
 
 #include <cstdlib>
 #include <limits>
@@ -30,20 +29,14 @@
 #include <folly/experimental/Select64.h>
 #include <glog/logging.h>
 
-#ifndef __GNUC__
-#error BitVectorCoding.h requires GCC
-#endif
-
 #if !FOLLY_X64
 #error BitVectorCoding.h requires x86_64
 #endif
 
-#if __BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__
-#error BitVectorCoding.h requires little endianness
-#endif
-
 namespace folly { namespace compression {
 
+static_assert(kIsLittleEndian, "BitVectorCoding.h requires little endianness");
+
 template <class Pointer>
 struct BitVectorCompressedListBase {
   BitVectorCompressedListBase() = default;
@@ -101,7 +94,7 @@ struct BitVectorEncoder {
     if (begin == end) {
       return MutableCompressedList();
     }
-    BitVectorEncoder encoder(end - begin, *(end - 1));
+    BitVectorEncoder encoder(size_t(end - begin), *(end - 1));
     for (; begin != end; ++begin) {
       encoder.add(*begin);
     }
@@ -132,7 +125,7 @@ struct BitVectorEncoder {
         reinterpret_cast<folly::Unaligned<uint64_t>*>(block), inner);
 
     if (skipQuantum != 0) {
-      size_t nextSkipPointerSize = value / (skipQuantum ?: 1);
+      size_t nextSkipPointerSize = value / skipQuantum;
       while (skipPointersSize_ < nextSkipPointerSize) {
         auto pos = skipPointersSize_++;
         folly::storeUnaligned<SkipValueType>(
@@ -141,8 +134,8 @@ struct BitVectorEncoder {
     }
 
     if (forwardQuantum != 0) {
-      if (size_ != 0 && (size_ % (forwardQuantum ?: 1) == 0)) {
-        const auto pos = size_ / (forwardQuantum ?: 1) - 1;
+      if (size_ != 0 && (size_ % forwardQuantum == 0)) {
+        const auto pos = size_ / forwardQuantum - 1;
         folly::storeUnaligned<SkipValueType>(
             forwardPointers_ + pos * sizeof(SkipValueType), value);
       }
@@ -186,11 +179,11 @@ struct BitVectorEncoder<Value, SkipValue, kSkipQuantum, kForwardQuantum>::
     layout.bits = bitVectorSizeInBytes;
 
     if (skipQuantum != 0) {
-      size_t numSkipPointers = upperBound / (skipQuantum ?: 1);
+      size_t numSkipPointers = upperBound / skipQuantum;
       layout.skipPointers = numSkipPointers * sizeof(SkipValueType);
     }
     if (forwardQuantum != 0) {
-      size_t numForwardPointers = size / (forwardQuantum ?: 1);
+      size_t numForwardPointers = size / forwardQuantum;
       layout.forwardPointers = numForwardPointers * sizeof(SkipValueType);
     }
 
@@ -307,15 +300,12 @@ class BitVectorReader {
 
     // Use forward pointer.
     if (Encoder::forwardQuantum > 0 && n > Encoder::forwardQuantum) {
-      // Workaround to avoid 'division by zero' compile-time error.
-      constexpr size_t q = Encoder::forwardQuantum ?: 1;
-
-      const size_t steps = position_ / q;
+      const size_t steps = position_ / Encoder::forwardQuantum;
       const size_t dest = folly::loadUnaligned<SkipValueType>(
           forwardPointers_ + (steps - 1) * sizeof(SkipValueType));
 
       reposition(dest);
-      n = position_ + 1 - steps * q;
+      n = position_ + 1 - steps * Encoder::forwardQuantum;
       // Correct inner_ will be set at the end.
     }
 
@@ -356,8 +346,8 @@ class BitVectorReader {
 
     if (Encoder::skipQuantum > 0 && v - value_ > Encoder::skipQuantum) {
       size_t q = v / Encoder::skipQuantum;
-      position_ = folly::loadUnaligned<SkipValueType>(
-                      skipPointers_ + (q - 1) * sizeof(SkipValueType)) - 1;
+      position_ = size_t(folly::loadUnaligned<SkipValueType>(
+                      skipPointers_ + (q - 1) * sizeof(SkipValueType))) - 1;
 
       reposition(q * Encoder::skipQuantum);
     }
@@ -448,5 +438,3 @@ class BitVectorReader {
 };
 
 }}  // namespaces
-
-#endif  // FOLLY_EXPERIMENTAL_BIT_VECTOR_CODING_H