From b52a9567520570bd6c850bcad3a6966f68639ef7 Mon Sep 17 00:00:00 2001
From: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Date: Thu, 17 Sep 2020 13:09:06 +0200
Subject: Add a check whether libzstd supports stream compression

Streaming compression was added fairly recently to zstd (and then
the API was changed a few times).

Rather than rely on libzstd versioning macros, this commit adds an
m4 script to test at configure time if the enums/functions we need
are available by trying to compile a small sample.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
---
 configure.ac                                |  2 ++
 lib/fstream/compress/ostream_compressor.c   |  2 +-
 lib/fstream/compress/zstd.c                 |  2 ++
 lib/fstream/compressor.c                    |  2 +-
 lib/fstream/uncompress/istream_compressor.c |  2 +-
 lib/fstream/uncompress/zstd.c               |  2 ++
 m4/zstd.m4                                  | 11 +++++++++++
 7 files changed, 20 insertions(+), 3 deletions(-)
 create mode 100644 m4/zstd.m4

diff --git a/configure.ac b/configure.ac
index 3de1109..70a1dfd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -182,6 +182,8 @@ AS_IF([test "x$with_zstd" != "xno"], [
 				       [with_zstd="no"])])
 ], [])
 
+AS_IF([test "x$with_zstd" != "xno"], [AC_TEST_ZSTD_STREAM], [])
+
 AS_IF([test "x$with_selinux" != "xno"], [
 	have_selinux="yes"
 
diff --git a/lib/fstream/compress/ostream_compressor.c b/lib/fstream/compress/ostream_compressor.c
index 7ea7919..30ff7eb 100644
--- a/lib/fstream/compress/ostream_compressor.c
+++ b/lib/fstream/compress/ostream_compressor.c
@@ -78,7 +78,7 @@ ostream_t *ostream_compressor_create(ostream_t *strm, int comp_id)
 #endif
 		break;
 	case FSTREAM_COMPRESSOR_ZSTD:
-#ifdef WITH_ZSTD
+#if defined(WITH_ZSTD) && defined(HAVE_ZSTD_STREAM)
 		comp = ostream_zstd_create(strm->get_filename(strm));
 #endif
 		break;
diff --git a/lib/fstream/compress/zstd.c b/lib/fstream/compress/zstd.c
index f4f7f86..c0b002e 100644
--- a/lib/fstream/compress/zstd.c
+++ b/lib/fstream/compress/zstd.c
@@ -8,6 +8,7 @@
 
 #include <zstd.h>
 
+#ifdef HAVE_ZSTD_STREAM
 typedef struct {
 	ostream_comp_t base;
 
@@ -90,3 +91,4 @@ ostream_comp_t *ostream_zstd_create(const char *filename)
 	base->cleanup = cleanup;
 	return base;
 }
+#endif /* HAVE_ZSTD_STREAM */
diff --git a/lib/fstream/compressor.c b/lib/fstream/compressor.c
index 903a5f7..48f9567 100644
--- a/lib/fstream/compressor.c
+++ b/lib/fstream/compressor.c
@@ -51,7 +51,7 @@ bool fstream_compressor_exists(int id)
 	case FSTREAM_COMPRESSOR_XZ:
 		return true;
 #endif
-#ifdef WITH_ZSTD
+#if defined(WITH_ZSTD) && defined(HAVE_ZSTD_STREAM)
 	case FSTREAM_COMPRESSOR_ZSTD:
 		return true;
 #endif
diff --git a/lib/fstream/uncompress/istream_compressor.c b/lib/fstream/uncompress/istream_compressor.c
index bc8ef39..75edd1b 100644
--- a/lib/fstream/uncompress/istream_compressor.c
+++ b/lib/fstream/uncompress/istream_compressor.c
@@ -40,7 +40,7 @@ istream_t *istream_compressor_create(istream_t *strm, int comp_id)
 #endif
 		break;
 	case FSTREAM_COMPRESSOR_ZSTD:
-#ifdef WITH_ZSTD
+#if defined(WITH_ZSTD) && defined(HAVE_ZSTD_STREAM)
 		comp = istream_zstd_create(strm->get_filename(strm));
 #endif
 		break;
diff --git a/lib/fstream/uncompress/zstd.c b/lib/fstream/uncompress/zstd.c
index 1838af5..fd22cbf 100644
--- a/lib/fstream/uncompress/zstd.c
+++ b/lib/fstream/uncompress/zstd.c
@@ -8,6 +8,7 @@
 
 #include <zstd.h>
 
+#ifdef HAVE_ZSTD_STREAM
 typedef struct {
 	istream_comp_t base;
 
@@ -77,3 +78,4 @@ istream_comp_t *istream_zstd_create(const char *filename)
 	base->cleanup = cleanup;
 	return base;
 }
+#endif /* HAVE_ZSTD_STREAM */
diff --git a/m4/zstd.m4 b/m4/zstd.m4
new file mode 100644
index 0000000..f644264
--- /dev/null
+++ b/m4/zstd.m4
@@ -0,0 +1,11 @@
+AC_DEFUN([AC_TEST_ZSTD_STREAM], [
+	AC_MSG_CHECKING([whether zstd supports stream compression])
+	AC_LANG_PUSH([C])
+	ac_zstd_save_CFLAGS="$CFLAGS"
+	CFLAGS="$CFLAGS $ZSTD_CFLAGS"
+	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <zstd.h>], [ZSTD_EndDirective op = ZSTD_e_end; ZSTD_compressStream2(NULL, NULL, NULL, op);])],
+			  AC_DEFINE(HAVE_ZSTD_STREAM, 1, [Does zstd support stream compression?])
+			  AC_MSG_RESULT([yes]), AC_MSG_RESULT([no]))
+	CFLAGS=$ac_zstd_save_CFLAGS
+	AC_LANG_POP([C])
+])
-- 
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