1 files changed, 75 insertions, 0 deletions
diff --git a/src/xz/hardware.h b/src/xz/hardware.h
new file mode 100644
index 0000000..a67b26e
--- /dev/null
+++ b/src/xz/hardware.h
@@ -0,0 +1,75 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       hardware.h
+/// \brief      Detection of available hardware resources
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+/// Initialize some hardware-specific variables, which are needed by other
+/// hardware_* functions.
+extern void hardware_init(void);
+
+
+/// Set the maximum number of worker threads.
+/// A special value of UINT32_MAX sets one thread in multi-threaded mode.
+extern void hardware_threads_set(uint32_t threadlimit);
+
+/// Get the maximum number of worker threads.
+extern uint32_t hardware_threads_get(void);
+
+/// Returns true if multithreaded mode should be used for .xz compression.
+/// This can be true even if the number of threads is one.
+extern bool hardware_threads_is_mt(void);
+
+
+/// Set the memory usage limit. There are separate limits for compression,
+/// decompression (also includes --list), and multithreaded decompression.
+/// Any combination of these can be set with a single call to this function.
+/// Zero indicates resetting the limit back to the defaults.
+/// The limit can also be set as a percentage of installed RAM; the
+/// percentage must be in the range [1, 100].
+extern void hardware_memlimit_set(uint64_t new_memlimit,
+		bool set_compress, bool set_decompress, bool set_mtdec,
+		bool is_percentage);
+
+/// Get the current memory usage limit for compression or decompression.
+/// This is a hard limit that will not be exceeded. This is obeyed in
+/// both single-threaded and multithreaded modes.
+extern uint64_t hardware_memlimit_get(enum operation_mode mode);
+
+/// This returns a system-specific default value if all of the following
+/// conditions are true:
+///
+///   - An automatic number of threads was requested (--threads=0).
+///
+///   - --memlimit-compress wasn't used or it was reset to the default
+///     value by setting it to 0.
+///
+/// Otherwise this is identical to hardware_memlimit_get(MODE_COMPRESS).
+///
+/// The idea is to keep automatic thread count reasonable so that too
+/// high memory usage is avoided and, with 32-bit xz, running out of
+/// address space is avoided.
+extern uint64_t hardware_memlimit_mtenc_get(void);
+
+/// Returns true if the value returned by hardware_memlimit_mtenc_get() is
+/// a system-specific default value. coder.c uses this to ignore the default
+/// memlimit in case it's too small even for a single thread in multithreaded
+/// mode. This way the default limit will never make xz fail or affect the
+/// compressed output; it will only make xz reduce the number of threads.
+extern bool hardware_memlimit_mtenc_is_default(void);
+
+/// Get the current memory usage limit for multithreaded decompression.
+/// This is only used to reduce the number of threads. This limit can be
+/// exceeded if the number of threads are reduce to one. Then the value
+/// from hardware_memlimit_get() will be honored like in single-threaded mode.
+extern uint64_t hardware_memlimit_mtdec_get(void);
+
+/// Display the amount of RAM and memory usage limits and exit.
+tuklib_attr_noreturn
+extern void hardware_memlimit_show(void);