Support dynamic field width in folly::format()

[folly.git] / folly / Bits.h

diff --git a/folly/Bits.h b/folly/Bits.h
index ade126d0803b6920c7fdd8dd1c30fd0009308811..4c1182a633c99dbac620a4e251065d47e77631f6 100644 (file)
--- a/folly/Bits.h
+++ b/folly/Bits.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014 Facebook, Inc.
+ * Copyright 2015 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -55,16 +55,10 @@
 #ifndef FOLLY_BITS_H_
 #define FOLLY_BITS_H_
 
-#include <folly/Portability.h>
-
-#ifndef __GNUC__
-#error GCC required
-#endif
-
-#ifndef __clang__
+#if !defined(__clang__) && !defined(_MSC_VER)
 #define FOLLY_INTRINSIC_CONSTEXPR constexpr
 #else
-// Unlike GCC, in Clang (as of 3.2) intrinsics aren't constexpr.
+// GCC is the only compiler with intrinsics constexpr.
 #define FOLLY_INTRINSIC_CONSTEXPR const
 #endif
 
@@ -78,6 +72,14 @@
 # include <byteswap.h>
 #endif
 
+#ifdef _MSC_VER
+# include <intrin.h>
+# pragma intrinsic(_BitScanForward)
+# pragma intrinsic(_BitScanForward64)
+# pragma intrinsic(_BitScanReverse)
+# pragma intrinsic(_BitScanReverse64)
+#endif
+
 #include <cassert>
 #include <cinttypes>
 #include <iterator>
@@ -98,7 +100,12 @@ typename std::enable_if<
    sizeof(T) <= sizeof(unsigned int)),
   unsigned int>::type
   findFirstSet(T x) {
+#ifdef _MSC_VER
+  unsigned long index;
+  return _BitScanForward(&index, x) ? index : 0;
+#else
   return __builtin_ffs(x);
+#endif
 }
 
 template <class T>
@@ -110,7 +117,12 @@ typename std::enable_if<
    sizeof(T) <= sizeof(unsigned long)),
   unsigned int>::type
   findFirstSet(T x) {
+#ifdef _MSC_VER
+  unsigned long index;
+  return _BitScanForward(&index, x) ? index : 0;
+#else
   return __builtin_ffsl(x);
+#endif
 }
 
 template <class T>
@@ -122,7 +134,12 @@ typename std::enable_if<
    sizeof(T) <= sizeof(unsigned long long)),
   unsigned int>::type
   findFirstSet(T x) {
+#ifdef _MSC_VER
+  unsigned long index;
+  return _BitScanForward64(&index, x) ? index : 0;
+#else
   return __builtin_ffsll(x);
+#endif
 }
 
 template <class T>
@@ -147,7 +164,18 @@ typename std::enable_if<
    sizeof(T) <= sizeof(unsigned int)),
   unsigned int>::type
   findLastSet(T x) {
+#ifdef _MSC_VER
+  unsigned long index;
+  int clz;
+  if (_BitScanReverse(&index, x)) {
+    clz = static_cast<int>(31 - index);
+  } else {
+    clz = 32;
+  }
+  return x ? 8 * sizeof(unsigned int) - clz : 0;
+#else
   return x ? 8 * sizeof(unsigned int) - __builtin_clz(x) : 0;
+#endif
 }
 
 template <class T>
@@ -159,7 +187,18 @@ typename std::enable_if<
    sizeof(T) <= sizeof(unsigned long)),
   unsigned int>::type
   findLastSet(T x) {
+#ifdef _MSC_VER
+  unsigned long index;
+  int clz;
+  if (_BitScanReverse(&index, x)) {
+    clz = static_cast<int>(31 - index);
+  } else {
+    clz = 32;
+  }
+  return x ? 8 * sizeof(unsigned int) - clz : 0;
+#else
   return x ? 8 * sizeof(unsigned long) - __builtin_clzl(x) : 0;
+#endif
 }
 
 template <class T>
@@ -171,7 +210,18 @@ typename std::enable_if<
    sizeof(T) <= sizeof(unsigned long long)),
   unsigned int>::type
   findLastSet(T x) {
+#ifdef _MSC_VER
+  unsigned long index;
+  unsigned long long clz;
+  if (_BitScanReverse(&index, x)) {
+    clz = static_cast<unsigned long long>(63 - index);
+  } else {
+    clz = 64;
+  }
+  return x ? 8 * sizeof(unsigned long long) - clz : 0;
+#else
   return x ? 8 * sizeof(unsigned long long) - __builtin_clzll(x) : 0;
+#endif
 }
 
 template <class T>
@@ -237,6 +287,8 @@ struct EndianIntBase {
   static T swap(T x);
 };
 
+#ifndef _MSC_VER
+
 /**
  * If we have the bswap_16 macro from byteswap.h, use it; otherwise, provide our
  * own definition.
@@ -254,6 +306,8 @@ our_bswap16(Int16 x) {
 }
 #endif
 
+#endif
+
 #define FB_GEN(t, fn) \
 template<> inline t EndianIntBase<t>::swap(t x) { return fn(x); }
 
@@ -262,12 +316,21 @@ template<> inline t EndianIntBase<t>::swap(t x) { return fn(x); }
 // __builtin_bswap16 for some reason, so we have to provide our own.
 FB_GEN( int8_t,)
 FB_GEN(uint8_t,)
+#ifdef _MSC_VER
+FB_GEN( int64_t, _byteswap_uint64)
+FB_GEN(uint64_t, _byteswap_uint64)
+FB_GEN( int32_t, _byteswap_ulong)
+FB_GEN(uint32_t, _byteswap_ulong)
+FB_GEN( int16_t, _byteswap_ushort)
+FB_GEN(uint16_t, _byteswap_ushort)
+#else
 FB_GEN( int64_t, __builtin_bswap64)
 FB_GEN(uint64_t, __builtin_bswap64)
 FB_GEN( int32_t, __builtin_bswap32)
 FB_GEN(uint32_t, __builtin_bswap32)
 FB_GEN( int16_t, our_bswap16)
 FB_GEN(uint16_t, our_bswap16)
+#endif
 
 #undef FB_GEN
 
@@ -339,10 +402,12 @@ class Endian {
     return detail::EndianInt<T>::little(x);
   }
 
+#if !defined(__ANDROID__)
   FB_GEN(64)
   FB_GEN(32)
   FB_GEN(16)
   FB_GEN(8)
+#endif
 };
 
 #undef FB_GEN
@@ -371,7 +436,7 @@ class BitIterator
   /**
    * Return the number of bits in an element of the underlying iterator.
    */
-  static size_t bitsPerBlock() {
+  static unsigned int bitsPerBlock() {
     return std::numeric_limits<
       typename std::make_unsigned<
         typename std::iterator_traits<BaseIter>::value_type
@@ -457,10 +522,10 @@ class BitIterator
   ssize_t distance_to(const BitIterator& other) const {
     return
       (other.base_reference() - this->base_reference()) * bitsPerBlock() +
-      (other.bitOffset_ - bitOffset_);
+      other.bitOffset_ - bitOffset_;
   }
 
-  ssize_t bitOffset_;
+  unsigned int bitOffset_;
 };
 
 /**