github.com/bhojpur/cache@v0.0.4/pkg/memory/storage_arm.go (about)

     1  package memory
     2  
     3  // Copyright (c) 2018 Bhojpur Consulting Private Limited, India. All rights reserved.
     4  
     5  // Permission is hereby granted, free of charge, to any person obtaining a copy
     6  // of this software and associated documentation files (the "Software"), to deal
     7  // in the Software without restriction, including without limitation the rights
     8  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     9  // copies of the Software, and to permit persons to whom the Software is
    10  // furnished to do so, subject to the following conditions:
    11  
    12  // The above copyright notice and this permission notice shall be included in
    13  // all copies or substantial portions of the Software.
    14  
    15  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    16  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    17  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    18  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    19  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    20  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    21  // THE SOFTWARE.
    22  
    23  import "unsafe"
    24  
    25  // maxMapSize represents the largest mmap size supported by Bhojpur Cache
    26  // in-memory database storage engine.
    27  const maxMapSize = 0x7FFFFFFF // 2GB
    28  
    29  // maxAllocSize is the size used when creating array pointers.
    30  const maxAllocSize = 0xFFFFFFF
    31  
    32  // Are unaligned load/stores broken on this arch?
    33  var brokenUnaligned bool
    34  
    35  func init() {
    36  	// Simple check to see whether this arch handles unaligned load/stores
    37  	// correctly.
    38  
    39  	// ARM9 and older devices require load/stores to be from/to aligned
    40  	// addresses. If not, the lower 2 bits are cleared and that address is
    41  	// read in a jumbled up order.
    42  
    43  	raw := [6]byte{0xfe, 0xef, 0x11, 0x22, 0x22, 0x11}
    44  	val := *(*uint32)(unsafe.Pointer(uintptr(unsafe.Pointer(&raw)) + 2))
    45  
    46  	brokenUnaligned = val != 0x11222211
    47  }