external/public-domain/xz/dist/src/liblzma/api/lzma/hardware.h

   1 /**
   2  * \file        lzma/hardware.h
   3  * \brief       Hardware information
   4  *
   5  * Since liblzma can consume a lot of system resources, it also provides
   6  * ways to limit the resource usage. Applications linking against liblzma
   7  * need to do the actual decisions how much resources to let liblzma to use.
   8  * To ease making these decisions, liblzma provides functions to find out
   9  * the relevant capabilities of the underlaying hardware. Currently there
  10  * is only a function to find out the amount of RAM, but in the future there
  11  * will be also a function to detect how many concurrent threads the system
  12  * can run.
  13  *
  14  * \note        On some operating systems, these function may temporarily
  15  *              load a shared library or open file descriptor(s) to find out
  16  *              the requested hardware information. Unless the application
  17  *              assumes that specific file descriptors are not touched by
  18  *              other threads, this should have no effect on thread safety.
  19  *              Possible operations involving file descriptors will restart
  20  *              the syscalls if they return EINTR.
  21  */
  22
  23 /*
  24  * Author: Lasse Collin
  25  *
  26  * This file has been put into the public domain.
  27  * You can do whatever you want with this file.
  28  *
  29  * See ../lzma.h for information about liblzma as a whole.
  30  */
  31
  32 #ifndef LZMA_H_INTERNAL
  33 #       error Never include this file directly. Use <lzma.h> instead.
  34 #endif
  35
  36
  37 /**
  38  * \brief       Get the total amount of physical memory (RAM) in bytes
  39  *
  40  * This function may be useful when determining a reasonable memory
  41  * usage limit for decompressing or how much memory it is OK to use
  42  * for compressing.
  43  *
  44  * \return      On success, the total amount of physical memory in bytes
  45  *              is returned. If the amount of RAM cannot be determined,
  46  *              zero is returned. This can happen if an error occurs
  47  *              or if there is no code in liblzma to detect the amount
  48  *              of RAM on the specific operating system.
  49  */
  50 extern LZMA_API(uint64_t) lzma_physmem(void) lzma_nothrow;
  51
  52
  53 /**
  54  * \brief       Get the number of processor cores or threads
  55  *
  56  * This function may be useful when determining how many threads to use.
  57  * If the hardware supports more than one thread per CPU core, the number
  58  * of hardware threads is returned if that information is available.
  59  *
  60  * \brief       On success, the number of available CPU threads or cores is
  61  *              returned. If this information isn't available or an error
  62  *              occurs, zero is returned.
  63  */
  64 extern LZMA_API(uint32_t) lzma_cputhreads(void) lzma_nothrow;