js/src/jstypes.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /*
   8 ** File:                jstypes.h
   9 ** Description: Definitions of NSPR's basic types
  10 **
  11 ** Prototypes and macros used to make up for deficiencies in ANSI environments
  12 ** that we have found.
  13 **
  14 ** Since we do not wrap <stdlib.h> and all the other standard headers, authors
  15 ** of portable code will not know in general that they need these definitions.
  16 ** Instead of requiring these authors to find the dependent uses in their code
  17 ** and take the following steps only in those C files, we take steps once here
  18 ** for all C files.
  19 **/
  20
  21 #ifndef jstypes_h
  22 #define jstypes_h
  23
  24 #include "mozilla/Casting.h"
  25 #include "mozilla/Types.h"
  26
  27 #include <stddef.h>
  28 #include <stdint.h>
  29
  30 // jstypes.h is (or should be!) included by every file in SpiderMonkey.
  31 // js-config.h also should be included by every file. So include it here.
  32 #include "js-config.h"
  33
  34 /*
  35  * The linkage of JS API functions differs depending on whether the file is
  36  * used within the JS library or not. Any source file within the JS
  37  * interpreter should define EXPORT_JS_API whereas any client of the library
  38  * should not. STATIC_JS_API is used to build JS as a static library.
  39  */
  40 #if defined(STATIC_JS_API)
  41 #  define JS_PUBLIC_API
  42 #  define JS_PUBLIC_DATA
  43 #elif defined(EXPORT_JS_API) || defined(STATIC_EXPORTABLE_JS_API)
  44 #  define JS_PUBLIC_API MOZ_EXPORT
  45 #  define JS_PUBLIC_DATA MOZ_EXPORT
  46 #else
  47 #  define JS_PUBLIC_API MOZ_IMPORT_API
  48 #  define JS_PUBLIC_DATA MOZ_IMPORT_DATA
  49 #endif
  50
  51 /***********************************************************************
  52 ** MACROS:      JS_BEGIN_MACRO
  53 **              JS_END_MACRO
  54 ** DESCRIPTION:
  55 **      Macro body brackets so that macros with compound statement definitions
  56 **      behave syntactically more like functions when called.
  57 ***********************************************************************/
  58 #define JS_BEGIN_MACRO do {
  59 #define JS_END_MACRO \
  60   }                  \
  61   while (0)
  62
  63 /***********************************************************************
  64 ** FUNCTIONS:   Bit
  65 **              BitMask
  66 ** DESCRIPTION:
  67 ** Bit masking functions.  XXX n must be <= 31 to be portable
  68 ***********************************************************************/
  69 namespace js {
  70 constexpr uint32_t Bit(uint32_t n) { return uint32_t(1) << n; }
  71
  72 constexpr uint32_t BitMask(uint32_t n) { return Bit(n) - 1; }
  73 }  // namespace js
  74
  75 /***********************************************************************
  76 ** FUNCTIONS:   HowMany
  77 **              RoundUp
  78 **              RoundDown
  79 **              Round
  80 ** DESCRIPTION:
  81 **      Commonly used functions for operations on compatible types.
  82 ***********************************************************************/
  83 namespace js {
  84 constexpr size_t HowMany(size_t x, size_t y) { return (x + y - 1) / y; }
  85
  86 constexpr size_t RoundUp(size_t x, size_t y) { return HowMany(x, y) * y; }
  87
  88 constexpr size_t RoundDown(size_t x, size_t y) { return (x / y) * y; }
  89
  90 constexpr size_t Round(size_t x, size_t y) { return ((x + y / 2) / y) * y; }
  91 }  // namespace js
  92
  93 #if (defined(__SIZEOF_POINTER__) && __SIZEOF_POINTER__ == 8) || \
  94     (defined(UINTPTR_MAX) && UINTPTR_MAX == 0xFFFFFFFFFFFFFFFFu)
  95 #  define JS_BITS_PER_WORD 64
  96 #else
  97 #  define JS_BITS_PER_WORD 32
  98 #endif
  99
 100 static_assert(sizeof(void*) == 8 ? JS_BITS_PER_WORD == 64
 101                                  : JS_BITS_PER_WORD == 32,
 102               "preprocessor and compiler must agree");
 103
 104 /***********************************************************************
 105 ** MACROS:      JS_FUNC_TO_DATA_PTR
 106 **              JS_DATA_TO_FUNC_PTR
 107 ** DESCRIPTION:
 108 **      Macros to convert between function and data pointers of the same
 109 **      size. Use them like this:
 110 **
 111 **      JSGetterOp nativeGetter;
 112 **      JSObject* scriptedGetter;
 113 **      ...
 114 **      scriptedGetter = JS_FUNC_TO_DATA_PTR(JSObject*, nativeGetter);
 115 **      ...
 116 **      nativeGetter = JS_DATA_TO_FUNC_PTR(JSGetterOp, scriptedGetter);
 117 **
 118 ***********************************************************************/
 119
 120 #define JS_FUNC_TO_DATA_PTR(type, fun) (mozilla::BitwiseCast<type>(fun))
 121 #define JS_DATA_TO_FUNC_PTR(type, ptr) (mozilla::BitwiseCast<type>(ptr))
 122
 123 #endif /* jstypes_h */