stat: Don't assume blocks are 512 bytes

POSIX says

> The unit for the st_blocks member of the stat structure is not defined
> within POSIX.1‐2008.

and recommends using DEV_BSIZE from <sys/param.h> if available.

Also, for -printf '%S', print 1 instead of NaN for empty files with no
blocks.

3 files changed, 24 insertions, 6 deletions

diff --git a/eval.c b/eval.c
index ff81e92..6731b31 100644
--- a/eval.c
+++ b/eval.c
@@ -626,7 +626,7 @@ bool eval_fls(const struct expr *expr, struct eval_state *state) {
 	}
 
 	uintmax_t ino = statbuf->ino;
-	uintmax_t blocks = (statbuf->blocks + 1)/2;
+	uintmax_t blocks = ((uintmax_t)statbuf->blocks*BFS_STAT_BLKSIZE + 1023)/1024;
 	char mode[11];
 	format_mode(statbuf->mode, mode);
 	uintmax_t nlink = statbuf->nlink;
@@ -886,7 +886,7 @@ bool eval_sparse(const struct expr *expr, struct eval_state *state) {
 		return false;
 	}
 
-	blkcnt_t expected = (statbuf->size + 511)/512;
+	blkcnt_t expected = (statbuf->size + BFS_STAT_BLKSIZE - 1)/BFS_STAT_BLKSIZE;
 	return statbuf->blocks < expected;
 }
 
diff --git a/printf.c b/printf.c
index 6a87f99..0e9110e 100644
--- a/printf.c
+++ b/printf.c
@@ -184,7 +184,8 @@ static int bfs_printf_strftime(FILE *file, const struct bfs_printf_directive *di
 
 /** %b: blocks */
 static int bfs_printf_b(FILE *file, const struct bfs_printf_directive *directive, const struct BFTW *ftwbuf) {
-	BFS_PRINTF_BUF(buf, "%ju", (uintmax_t)ftwbuf->statbuf->blocks);
+	uintmax_t blocks = ((uintmax_t)ftwbuf->statbuf->blocks*BFS_STAT_BLKSIZE + 511)/512;
+	BFS_PRINTF_BUF(buf, "%ju", blocks);
 	return fprintf(file, directive->str, buf);
 }
 
@@ -266,7 +267,8 @@ static int bfs_printf_i(FILE *file, const struct bfs_printf_directive *directive
 
 /** %k: 1K blocks */
 static int bfs_printf_k(FILE *file, const struct bfs_printf_directive *directive, const struct BFTW *ftwbuf) {
-	BFS_PRINTF_BUF(buf, "%ju", (uintmax_t)(ftwbuf->statbuf->blocks + 1)/2);
+	uintmax_t blocks = ((uintmax_t)ftwbuf->statbuf->blocks*BFS_STAT_BLKSIZE + 1023)/1024;
+	BFS_PRINTF_BUF(buf, "%ju", blocks);
 	return fprintf(file, directive->str, buf);
 }
 
@@ -326,7 +328,13 @@ static int bfs_printf_s(FILE *file, const struct bfs_printf_directive *directive
 
 /** %S: sparseness */
 static int bfs_printf_S(FILE *file, const struct bfs_printf_directive *directive, const struct BFTW *ftwbuf) {
-	double sparsity = 512.0 * ftwbuf->statbuf->blocks / ftwbuf->statbuf->size;
+	double sparsity;
+	const struct bfs_stat *sb = ftwbuf->statbuf;
+	if (sb->size == 0 && sb->blocks == 0) {
+		sparsity = 1.0;
+	} else {
+		sparsity = (double)BFS_STAT_BLKSIZE*sb->blocks/sb->size;
+	}
 	return fprintf(file, directive->str, sparsity);
 }
 
diff --git a/stat.h b/stat.h
index d47d248..95c61ec 100644
--- a/stat.h
+++ b/stat.h
@@ -17,7 +17,9 @@
 #ifndef BFS_STAT_H
 #define BFS_STAT_H
 
+#include <sys/param.h>
 #include <sys/types.h>
+#include <sys/stat.h>
 #include <time.h>
 
 /**
@@ -47,6 +49,14 @@ enum bfs_stat_flag {
 	BFS_STAT_BROKEN_OK = 1 << 0,
 };
 
+#ifdef DEV_BSIZE
+#	define BFS_STAT_BLKSIZE DEV_BSIZE
+#elif defined(S_BLKSIZE)
+#	define BFS_STAT_BLKSIZE S_BLKSIZE
+#else
+#	define BFS_STAT_BLKSIZE 512
+#endif
+
 /**
  * Facade over struct stat.
  */
@@ -68,7 +78,7 @@ struct bfs_stat {
 	uid_t uid;
 	/** File size in bytes. */
 	off_t size;
-	/** Number of 512B blocks allocated. */
+	/** Number of disk blocks allocated (of size BFS_STAT_BLKSIZE). */
 	blkcnt_t blocks;
 
 	/** Access time. */