disas/libvixl/code-buffer.h

   1 // Copyright 2014, ARM Limited
   2 // All rights reserved.
   3 //
   4 // Redistribution and use in source and binary forms, with or without
   5 // modification, are permitted provided that the following conditions are met:
   6 //
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   8 //     this list of conditions and the following disclaimer.
   9 //   * Redistributions in binary form must reproduce the above copyright notice,
  10 //     this list of conditions and the following disclaimer in the documentation
  11 //     and/or other materials provided with the distribution.
  12 //   * Neither the name of ARM Limited nor the names of its contributors may be
  13 //     used to endorse or promote products derived from this software without
  14 //     specific prior written permission.
  15 //
  16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS CONTRIBUTORS "AS IS" AND
  17 // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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  25 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26
  27 #ifndef VIXL_CODE_BUFFER_H
  28 #define VIXL_CODE_BUFFER_H
  29
  30 #include <string.h>
  31 #include "globals.h"
  32
  33 namespace vixl {
  34
  35 class CodeBuffer {
  36  public:
  37   explicit CodeBuffer(size_t capacity = 4 * KBytes);
  38   CodeBuffer(void* buffer, size_t capacity);
  39   ~CodeBuffer();
  40
  41   void Reset();
  42
  43   ptrdiff_t OffsetFrom(ptrdiff_t offset) const {
  44     ptrdiff_t cursor_offset = cursor_ - buffer_;
  45     VIXL_ASSERT((offset >= 0) && (offset <= cursor_offset));
  46     return cursor_offset - offset;
  47   }
  48
  49   ptrdiff_t CursorOffset() const {
  50     return OffsetFrom(0);
  51   }
  52
  53   template <typename T>
  54   T GetOffsetAddress(ptrdiff_t offset) const {
  55     VIXL_ASSERT((offset >= 0) && (offset <= (cursor_ - buffer_)));
  56     return reinterpret_cast<T>(buffer_ + offset);
  57   }
  58
  59   size_t RemainingBytes() const {
  60     VIXL_ASSERT((cursor_ >= buffer_) && (cursor_ <= (buffer_ + capacity_)));
  61     return (buffer_ + capacity_) - cursor_;
  62   }
  63
  64   // A code buffer can emit:
  65   //  * 32-bit data: instruction and constant.
  66   //  * 64-bit data: constant.
  67   //  * string: debug info.
  68   void Emit32(uint32_t data) { Emit(data); }
  69
  70   void Emit64(uint64_t data) { Emit(data); }
  71
  72   void EmitString(const char* string);
  73
  74   // Align to kInstructionSize.
  75   void Align();
  76
  77   size_t capacity() const { return capacity_; }
  78
  79   bool IsManaged() const { return managed_; }
  80
  81   void Grow(size_t new_capacity);
  82
  83   bool IsDirty() const { return dirty_; }
  84
  85   void SetClean() { dirty_ = false; }
  86
  87  private:
  88   template <typename T>
  89   void Emit(T value) {
  90     VIXL_ASSERT(RemainingBytes() >= sizeof(value));
  91     dirty_ = true;
  92     memcpy(cursor_, &value, sizeof(value));
  93     cursor_ += sizeof(value);
  94   }
  95
  96   // Backing store of the buffer.
  97   byte* buffer_;
  98   // If true the backing store is allocated and deallocated by the buffer. The
  99   // backing store can then grow on demand. If false the backing store is
 100   // provided by the user and cannot be resized internally.
 101   bool managed_;
 102   // Pointer to the next location to be written.
 103   byte* cursor_;
 104   // True if there has been any write since the buffer was created or cleaned.
 105   bool dirty_;
 106   // Capacity in bytes of the backing store.
 107   size_t capacity_;
 108 };
 109
 110 }  // namespace vixl
 111
 112 #endif  // VIXL_CODE_BUFFER_H
 113