[PATCH 1/2] simple random data generator for tests

Subsystems: kernel build + files below scripts/ (unless maintained elsewhere), the rest

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4 messages, 2 authors, 2016-06-15 · open the first message on its own page

[PATCH 1/2] simple random data generator for tests

From: Nicolas Pitre <hidden>
Date: 2016-06-15 22:43:04

Reliance on /dev/urandom produces test vectors that are, well, random. 
This can create problems impossible to track down when the data is 
different from one test invokation to another.

The goal is not to have random data to test, but rather to have a 
convenient way to create sets of large files with non compressible and 
non deltifiable data in a reproducible way.

Signed-off-by: Nicolas Pitre <redacted>
---
 Makefile         |    7 +++++--
 test-genrandom.c |   34 ++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 2 deletions(-)
 create mode 100644 test-genrandom.c

diff --git a/Makefile b/Makefile
index a77d31d..bd0ba95 100644
--- a/Makefile
+++ b/Makefile

@@ -932,7 +932,7 @@ endif
 
 export NO_SVN_TESTS
 
-test: all test-chmtime$X
+test: all test-chmtime$X test-genrandom$X
 	$(MAKE) -C t/ all
 
 test-date$X: test-date.c date.o ctype.o

@@ -953,6 +953,9 @@ test-match-trees$X: test-match-trees.o $(GITLIBS)
 test-chmtime$X: test-chmtime.c
 	$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $<
 
+test-genrandom$X: test-genrandom.c
+	$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $<
+
 check-sha1:: test-sha1$X
 	./test-sha1.sh

@@ -1041,7 +1044,7 @@ dist-doc:
 
 clean:
 	rm -f *.o mozilla-sha1/*.o arm/*.o ppc/*.o compat/*.o xdiff/*.o \
-		test-chmtime$X $(LIB_FILE) $(XDIFF_LIB)
+		test-chmtime$X test-genrandom$X $(LIB_FILE) $(XDIFF_LIB)
 	rm -f $(ALL_PROGRAMS) $(BUILT_INS) git$X
 	rm -f *.spec *.pyc *.pyo */*.pyc */*.pyo common-cmds.h TAGS tags
 	rm -rf autom4te.cache

diff --git a/test-genrandom.c b/test-genrandom.c
new file mode 100644
index 0000000..6cc4650
--- /dev/null
+++ b/test-genrandom.c

@@ -0,0 +1,34 @@
+/*
+ * Simple random data generator used to create reproducible test files.
+ * This is inspired from POSIX.1-2001 implementation example for rand().
+ * Copyright (C) 2007 by Nicolas Pitre, licensed under the GPL version 2.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char *argv[])
+{
+	unsigned long count, next = 0;
+	unsigned char *c;
+
+	if (argc < 2 || argc > 3) {
+		fprintf( stderr, "Usage: %s <seed_string> [<size>]", argv[0]);
+		return 1;
+	}
+
+	c = (unsigned char *) argv[1];
+	do {
+		next = next * 11 + *c;
+	} while (*c++);
+	
+	count = (argc == 3) ? strtoul(argv[2], NULL, 0) : -1L;
+
+	while (count--) {
+		next = next * 1103515245 + 12345;
+		if (putchar((next >> 16) & 0xff) == EOF)
+			return -1;
+	}
+
+	return 0;
+}

-- 
1.5.1.777.gd14d3-dirty

Re: [PATCH 1/2] simple random data generator for tests

From: Shawn O. Pearce <hidden>
Date: 2016-06-15 22:43:04

Nicolas Pitre [off-list ref] wrote:

---
 Makefile         |    7 +++++--
 test-genrandom.c |   34 ++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 2 deletions(-)
 create mode 100644 test-genrandom.c

A change to .gitignore would also be nice.  ;-)

+	unsigned long count, next = 0;

What about wraparound?  Could this produce different results on a
32 bit system and a 64 bit system, due to the difference in size
of unsigned long?

-- 
Shawn.

Re: [PATCH 1/2] simple random data generator for tests

From: Nicolas Pitre <hidden>
Date: 2016-06-15 22:43:04

On Wed, 11 Apr 2007, Shawn O. Pearce wrote:

Nicolas Pitre [off-list ref] wrote:

quoted

---
 Makefile         |    7 +++++--
 test-genrandom.c |   34 ++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 2 deletions(-)
 create mode 100644 test-genrandom.c

A change to .gitignore would also be nice.  ;-)

Gah!

quoted

+	unsigned long count, next = 0;

What about wraparound?  Could this produce different results on a
32 bit system and a 64 bit system, due to the difference in size
of unsigned long?

No, because the bits we extract are below 32 bits, and the multiply 
operation will always provide the same results in the low 32 bits 
regardless.


Nicolas

[PATCH 1/2 (with .gitignore)] simple random data generator for tests

From: Nicolas Pitre <hidden>
Date: 2016-06-15 22:43:04

Reliance on /dev/urandom produces test vectors that are, well, random. 
This can cause problems impossible to track down when the data is 
different from one test invokation to another.

The goal is not to have random data to test, but rather to have a 
convenient way to create sets of large files with non compressible and 
non deltifiable data in a reproducible way.

Signed-off-by: Nicolas Pitre <redacted>
---

diff --git a/Makefile b/Makefile
index a77d31d..bd0ba95 100644
--- a/Makefile
+++ b/Makefile

@@ -932,7 +932,7 @@ endif
 
 export NO_SVN_TESTS
 
-test: all test-chmtime$X
+test: all test-chmtime$X test-genrandom$X
 	$(MAKE) -C t/ all
 
 test-date$X: test-date.c date.o ctype.o

@@ -953,6 +953,9 @@ test-match-trees$X: test-match-trees.o $(GITLIBS)
 test-chmtime$X: test-chmtime.c
 	$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $<
 
+test-genrandom$X: test-genrandom.c
+	$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $<
+
 check-sha1:: test-sha1$X
 	./test-sha1.sh

@@ -1041,7 +1044,7 @@ dist-doc:
 
 clean:
 	rm -f *.o mozilla-sha1/*.o arm/*.o ppc/*.o compat/*.o xdiff/*.o \
-		test-chmtime$X $(LIB_FILE) $(XDIFF_LIB)
+		test-chmtime$X test-genrandom$X $(LIB_FILE) $(XDIFF_LIB)
 	rm -f $(ALL_PROGRAMS) $(BUILT_INS) git$X
 	rm -f *.spec *.pyc *.pyo */*.pyc */*.pyo common-cmds.h TAGS tags
 	rm -rf autom4te.cache

diff --git a/test-genrandom.c b/test-genrandom.c
new file mode 100644
index 0000000..6cc4650
--- /dev/null
+++ b/test-genrandom.c

@@ -0,0 +1,34 @@
+/*
+ * Simple random data generator used to create reproducible test files.
+ * This is inspired from POSIX.1-2001 implementation example for rand().
+ * Copyright (C) 2007 by Nicolas Pitre, licensed under the GPL version 2.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char *argv[])
+{
+	unsigned long count, next = 0;
+	unsigned char *c;
+
+	if (argc < 2 || argc > 3) {
+		fprintf( stderr, "Usage: %s <seed_string> [<size>]", argv[0]);
+		return 1;
+	}
+
+	c = (unsigned char *) argv[1];
+	do {
+		next = next * 11 + *c;
+	} while (*c++);
+	
+	count = (argc == 3) ? strtoul(argv[2], NULL, 0) : -1L;
+
+	while (count--) {
+		next = next * 1103515245 + 12345;
+		if (putchar((next >> 16) & 0xff) == EOF)
+			return -1;
+	}
+
+	return 0;
+}

diff --git a/.gitignore b/.gitignore
index 9229e91..fa7ac93 100644
--- a/.gitignore
+++ b/.gitignore

@@ -149,6 +149,7 @@ test-chmtime
 test-date
 test-delta
 test-dump-cache-tree
+test-genrandom
 test-match-trees
 common-cmds.h
 *.tar.gz

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