js/src/jit/FixedList.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 #ifndef jit_FixedList_h
   8 #define jit_FixedList_h
   9
  10 #include "mozilla/Assertions.h"
  11 #include "mozilla/Likely.h"
  12
  13 #include <stddef.h>
  14
  15 #include "jit/JitAllocPolicy.h"
  16 #include "js/Utility.h"
  17
  18 namespace js {
  19 namespace jit {
  20
  21 // List of a fixed length, but the length is unknown until runtime.
  22 template <typename T>
  23 class FixedList {
  24   T* list_;
  25   size_t length_;
  26
  27  private:
  28   FixedList(const FixedList&);       // no copy definition.
  29   void operator=(const FixedList*);  // no assignment definition.
  30
  31  public:
  32   FixedList() : list_(nullptr), length_(0) {}
  33
  34   // Dynamic memory allocation requires the ability to report failure.
  35   [[nodiscard]] bool init(TempAllocator& alloc, size_t length) {
  36     if (length == 0) {
  37       return true;
  38     }
  39
  40     list_ = alloc.allocateArray<T>(length);
  41     if (!list_) {
  42       return false;
  43     }
  44
  45     length_ = length;
  46     return true;
  47   }
  48
  49   size_t empty() const { return length_ == 0; }
  50
  51   size_t length() const { return length_; }
  52
  53   void shrink(size_t num) {
  54     MOZ_ASSERT(num < length_);
  55     length_ -= num;
  56   }
  57
  58   [[nodiscard]] bool growBy(TempAllocator& alloc, size_t num) {
  59     size_t newlength = length_ + num;
  60     if (newlength < length_) {
  61       return false;
  62     }
  63     size_t bytes;
  64     if (MOZ_UNLIKELY(!CalculateAllocSize<T>(newlength, &bytes))) {
  65       return false;
  66     }
  67     T* list = (T*)alloc.allocate(bytes);
  68     if (MOZ_UNLIKELY(!list)) {
  69       return false;
  70     }
  71
  72     for (size_t i = 0; i < length_; i++) {
  73       list[i] = list_[i];
  74     }
  75
  76     length_ += num;
  77     list_ = list;
  78     return true;
  79   }
  80
  81   T& operator[](size_t index) {
  82     MOZ_ASSERT(index < length_);
  83     return list_[index];
  84   }
  85   const T& operator[](size_t index) const {
  86     MOZ_ASSERT(index < length_);
  87     return list_[index];
  88   }
  89
  90   T* data() { return list_; }
  91
  92   T* begin() { return list_; }
  93   T* end() { return list_ + length_; }
  94 };
  95
  96 }  // namespace jit
  97 }  // namespace js
  98
  99 #endif /* jit_FixedList_h */