[PATCH v3 2/4] erofs-utils: add a helper to get available processors

[Yifan Zhao]

From: Gao Xiang <hsiangkao at linux.alibaba.com>

In order to prepare for multi-threaded decompression.

Signed-off-by: Gao Xiang <hsiangkao at linux.alibaba.com>
---
 configure.ac           |  1 +
 include/erofs/config.h |  1 +
 lib/config.c           | 12 ++++++++++++
 3 files changed, 14 insertions(+)

diff --git a/configure.ac b/configure.ac
index 1c7f53b..08eee08 100644
--- a/configure.ac
+++ b/configure.ac
@@ -256,6 +256,7 @@ AC_CHECK_FUNCS(m4_flatten([
 	strerror
 	strrchr
 	strtoull
+	sysconf
 	tmpfile64
 	utimensat]))
 
diff --git a/include/erofs/config.h b/include/erofs/config.h
index eecf575..73e3ac2 100644
--- a/include/erofs/config.h
+++ b/include/erofs/config.h
@@ -109,6 +109,7 @@ static inline int erofs_selabel_open(const char *file_contexts)
 
 void erofs_update_progressinfo(const char *fmt, ...);
 char *erofs_trim_for_progressinfo(const char *str, int placeholder);
+unsigned int erofs_get_available_processors(void);
 
 #ifdef __cplusplus
 }
diff --git a/lib/config.c b/lib/config.c
index 1096cd1..947a183 100644
--- a/lib/config.c
+++ b/lib/config.c
@@ -14,6 +14,9 @@
 #ifdef HAVE_SYS_IOCTL_H
 #include <sys/ioctl.h>
 #endif
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
 
 struct erofs_configure cfg;
 struct erofs_sb_info sbi;
@@ -177,3 +180,12 @@ void erofs_update_progressinfo(const char *fmt, ...)
 	fputs(msg, stdout);
 	fputc('\n', stdout);
 }
+
+unsigned int erofs_get_available_processors(void)
+{
+#if defined(HAVE_UNISTD_H) && defined(HAVE_SYSCONF)
+	return sysconf(_SC_NPROCESSORS_ONLN);
+#else
+	return 0;
+#endif
+}
-- 
2.44.0