tdf#137308 - Add zstd build support and decompression classes

Integrate build system support for the Zstandard (zstd) library and
implement the corresponding C++ decompression stream classes, enabling
future use of zstd-compressed streams in ZIP packages.

Build System (Part 2a):
- Add `--with-system-zstd=[yes|no|auto]` configure option.
- Implement system library checks (`zstd.h`, `libzstd`) in configure.ac.
- Define rules (`external/zstd/*`) for downloading and building the
  internal zstd static library (decompression components only).
- Set up necessary CFLAGS/LIBS via configure.ac and config_host.mk.in.
- Configure linking via RepositoryExternal.mk (`gb_LinkTarget__use_zstd`).
- Update auxiliary files (download.lst, distro-configs, etc.).

C++ Implementation (Part 2b):
- Implement `InflateZstd` (in `include/package`) and `InflaterBytesZstd`
  (in `package/inc`) inheriting from `Inflater`/`InflaterBytes`.
- Use the zstd streaming API (`ZSTD_decompressStream`) following the
  existing single-call pattern established by the zlib implementation.
- Manage context (`ZSTD_DCtx`) and input buffer (`ZSTD_inBuffer`) state.
- Handle errors, stream completion (`ret == 0`), and input truncation.
- Add new classes to `package/Library_package2.mk` build.

This completes the infrastructure for zstd decompression support.
The next step (Part 2c) involves adding logic to select the
appropriate Inflater based on the ZIP entry's compression method ID.

Change-Id: Ia673f3f19b6a751ba5225394fcf8c3f145c4ae63
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/184243
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolan.mcnamara@collabora.com>

Makefile.fetch

@@ -240,6 +240,7 @@ $(WORKDIR)/download: $(BUILDDIR)/config_$(gb_Side).mk $(SRCDIR)/download.lst $(S
 		$(call fetch_Optional,WPS,WPS_TARBALL) \
 		$(call fetch_Optional,XSLTML,XSLTML_TARBALL) \
 		$(call fetch_Optional,ZLIB,ZLIB_TARBALL) \
+		$(call fetch_Optional,ZSTD,ZSTD_TARBALL) \
 		$(call fetch_Optional,ZMF,ZMF_TARBALL) \
 	,$(call fetch_Download_item,https://dev-www.libreoffice.org/src,$(item)))
 	$(foreach item, \

RepositoryExternal.mk

@@ -409,6 +409,23 @@ endef
 
 endif # SYSTEM_ZLIB
 
+ifneq ($(SYSTEM_ZSTD),)
+  define gb_LinkTarget__use_zstd
+    $(call gb_LinkTarget_add_libs,$(1),-lzstd)
+  endef
+
+  gb_ExternalProject__use_zstd :=
+else
+  define gb_LinkTarget__use_zstd
+    $(call gb_LinkTarget_set_include,$(1),$(ZSTD_CFLAGS) $$(INCLUDE))
+    $(call gb_LinkTarget_use_static_libraries,$(1),zstd)
+  endef
+
+  define gb_ExternalProject__use_zstd
+    $(call gb_ExternalProject_use_static_libraries,$(1),zstd)
+  endef
+endif
+
 
 ifneq ($(SYSTEM_LIBJPEG),)
 

bin/oss-fuzz-setup.sh

@@ -53,6 +53,7 @@ curl --no-progress-meter -S \
     -C - -O https://dev-www.libreoffice.org/src/$ZMF_TARBALL \
     -C - -O https://dev-www.libreoffice.org/src/$PIXMAN_TARBALL \
     -C - -O https://dev-www.libreoffice.org/src/$ZLIB_TARBALL \
+    -C - -O https://dev-www.libreoffice.org/src/$ZSTD_TARBALL \
     -C - -O https://dev-www.libreoffice.org/src/$MDDS_TARBALL \
     -C - -O https://dev-www.libreoffice.org/src/$OPENSSL_TARBALL \
     -C - -O https://dev-www.libreoffice.org/src/$LANGTAGREG_TARBALL \

config_host.mk.in

@@ -736,6 +736,7 @@ SYSTEM_WPG=@SYSTEM_WPG@
 SYSTEM_WPS=@SYSTEM_WPS@
 SYSTEM_XMLSEC=@SYSTEM_XMLSEC@
 SYSTEM_ZLIB=@SYSTEM_ZLIB@
+SYSTEM_ZSTD=@SYSTEM_ZSTD@
 SYSTEM_ZMF=@SYSTEM_ZMF@
 export SYSTEMD_ESCAPE=@SYSTEMD_ESCAPE@
 export SYSTEMD_RUN=@SYSTEMD_RUN@
@@ -803,6 +804,8 @@ export XSLTPROC=@XSLTPROC@
 export XVFB_RUN=@XVFB_RUN@
 export ZLIB_CFLAGS=$(gb_SPACE)@ZLIB_CFLAGS@
 export ZLIB_LIBS=$(gb_SPACE)@ZLIB_LIBS@
+ZSTD_CFLAGS=$(gb_SPACE)@ZSTD_CFLAGS@
+ZSTD_LIBS=$(gb_SPACE)@ZSTD_LIBS@
 export ZMF_CFLAGS=$(gb_SPACE)@ZMF_CFLAGS@
 export ZMF_LIBS=$(gb_SPACE)@ZMF_LIBS@
 export GET_TASK_ALLOW_ENTITLEMENT=@GET_TASK_ALLOW_ENTITLEMENT@

configure.ac

@@ -2439,6 +2439,11 @@ AC_ARG_WITH(system-zlib,
         [Use zlib already on system.]),,
     [with_system_zlib=auto])
 
+AC_ARG_WITH(system-zstd,
+    AS_HELP_STRING([--with-system-zstd=@<:@yes|no|auto@:>@],
+        [Use zstd already on system [default=auto].]),,
+    [with_system_zstd=auto])
+
 AC_ARG_WITH(system-jpeg,
     AS_HELP_STRING([--with-system-jpeg],
         [Use jpeg already on system.]),,
@@ -9857,6 +9862,52 @@ AC_SUBST(ZLIB_CFLAGS)
 AC_SUBST(ZLIB_LIBS)
 AC_SUBST(SYSTEM_ZLIB)
 
+dnl ===================================================================
+dnl Check for system zstd
+dnl ===================================================================
+
+if test "x$with_system_zstd" = "xauto"; then
+  case "$_os" in
+    WINNT) with_system_zstd="$with_system_libs" ;;  # follow system-libs on Windows
+    *)     with_system_zstd="$with_system_libs" ;;  # follow system-libs on Unix
+  esac
+fi
+
+AC_MSG_CHECKING([which zstd to use])
+case "$with_system_zstd" in
+  yes)
+    AC_MSG_RESULT([system])
+    SYSTEM_ZSTD=TRUE
+
+    AC_CHECK_HEADER([zstd.h], [],
+      [AC_MSG_ERROR([zstd.h not found. Install system zstd.])])
+
+    AC_CHECK_LIB([zstd], [ZSTD_createDStream],
+      [ ZSTD_LIBS="-lzstd"
+        ZSTD_CFLAGS="" ],
+      [ AC_MSG_ERROR([system zstd library not found or broken.]) ])
+    ;;
+
+  ""|no)
+    AC_MSG_RESULT([bundled])
+    SYSTEM_ZSTD=
+    ZSTD_LIBS=""
+    ZSTD_CFLAGS="-I\${WORKDIR}/UnpackedTarball/zstd/lib \
+                 -I\${WORKDIR}/UnpackedTarball/zstd/lib/common \
+                 -I\${WORKDIR}/UnpackedTarball/zstd/lib/decompress"
+    BUILD_TYPE="$BUILD_TYPE ZSTD"
+    ;;
+
+  *)
+    AC_MSG_ERROR([Invalid value for --with-system-zstd: $with_system_zstd])
+    ;;
+esac
+
+AC_SUBST(SYSTEM_ZSTD)
+AC_SUBST(ZSTD_LIBS)
+AC_SUBST(ZSTD_CFLAGS)
+AC_SUBST(BUILD_TYPE)
+
 dnl ===================================================================
 dnl Check for system jpeg
 dnl ===================================================================

distro-configs/CPLinux-LOKit.conf

@@ -6,6 +6,7 @@
 --with-system-dicts
 --with-myspell-dicts
 --with-system-zlib
+--with-system-zstd
 --disable-poppler
 --enable-cairo-rgba
 --without-system-cairo

distro-configs/Jenkins/LibreOfficeLinuxUpdater.conf

@@ -3,6 +3,7 @@
 --with-system-dicts
 --with-myspell-dicts
 --with-system-zlib
+--with-system-zstd
 --without-system-poppler
 --without-system-openssl
 --without-system-libpng

distro-configs/LibreOfficeLinux.conf

@@ -1,6 +1,7 @@
 --with-system-dicts
 --with-myspell-dicts
 --with-system-zlib
+--with-system-zstd
 --without-system-poppler
 --without-system-openssl
 --without-system-libpng

distro-configs/LibreOfficeOnline.conf

@@ -37,6 +37,7 @@
 --with-linker-hash-style=both
 --with-system-dicts
 --with-system-zlib
+--with-system-zstd
 --with-theme=colibre
 --without-branding
 --without-help

distro-configs/LibreOfficeOpenBSD.conf

@@ -26,6 +26,7 @@
 --with-system-poppler
 --with-system-redland
 --with-system-zlib
+--with-system-zstd
 --with-vendor=The OpenBSD project
 --without-junit
 --without-system-libwpd

download.lst

@@ -680,6 +680,11 @@ ZLIB_TARBALL := zlib-1.3.1.tar.xz
 # three static lines
 # so that git cherry-pick
 # will not run into conflicts
+ZSTD_SHA256SUM := eb33e51f49a15e023950cd7825ca74a4a2b43db8354825ac24fc1b7ee09e6fa3
+ZSTD_TARBALL := zstd-1.5.7.tar.gz
+# three static lines
+# so that git cherry-pick
+# will not run into conflicts
 ZMF_SHA256SUM := 27051a30cb057fdb5d5de65a1f165c7153dc76e27fe62251cbb86639eb2caf22
 ZMF_TARBALL := libzmf-0.0.2.tar.xz
 # three static lines

external/Module_external.mk

@@ -101,6 +101,7 @@ $(eval $(call gb_Module_add_moduledirs,external,\
 	$(call gb_Helper_optional,WPS,libwps) \
 	$(call gb_Helper_optional,XSLTML,xsltml) \
 	$(call gb_Helper_optional,ZLIB,zlib) \
+	$(call gb_Helper_optional,ZSTD,zstd) \
 	$(call gb_Helper_optional,ZMF,libzmf) \
 ))
 

external/zstd/Makefile

@@ -0,0 +1,14 @@
+# -*- Mode: makefile-gmake; tab-width: 4; indent-tabs-mode: t -*-
+#
+# This file is part of the LibreOffice project.
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+#
+
+module_directory:=$(dir $(realpath $(firstword $(MAKEFILE_LIST))))
+
+include $(module_directory)/../../solenv/gbuild/partial_build.mk
+
+# vim: set noet sw=4 ts=4:

external/zstd/Module_zstd.mk

@@ -0,0 +1,17 @@
+# -*- Mode: makefile-gmake; tab-width: 4; indent-tabs-mode: t -*-
+#
+# This file is part of the LibreOffice project.
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+#
+
+$(eval $(call gb_Module_Module,zstd))
+
+$(eval $(call gb_Module_add_targets,zstd,\
+    StaticLibrary_zstd \
+    UnpackedTarball_zstd \
+))
+
+# vim: set noet sw=4 ts=4:

external/zstd/StaticLibrary_zstd.mk

@@ -0,0 +1,41 @@
+# -*- Mode: makefile-gmake; tab-width: 4; indent-tabs-mode: t -*-
+#
+# This file is part of the LibreOffice project.
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+#
+
+$(eval $(call gb_StaticLibrary_StaticLibrary,zstd))
+
+$(eval $(call gb_StaticLibrary_use_unpacked,zstd,zstd))
+
+$(eval $(call gb_StaticLibrary_set_warnings_disabled,zstd))
+
+$(eval $(call gb_StaticLibrary_set_include,zstd,\
+    -I$(gb_UnpackedTarball_workdir)/zstd/lib \
+    -I$(gb_UnpackedTarball_workdir)/zstd/lib/common \
+    -I$(gb_UnpackedTarball_workdir)/zstd/lib/decompress \
+    $$(INCLUDE) \
+))
+
+$(eval $(call gb_StaticLibrary_add_generated_cobjects,zstd,\
+    UnpackedTarball/zstd/lib/common/entropy_common \
+    UnpackedTarball/zstd/lib/common/error_private \
+    UnpackedTarball/zstd/lib/common/fse_decompress \
+    UnpackedTarball/zstd/lib/common/xxhash \
+    UnpackedTarball/zstd/lib/common/zstd_common \
+    UnpackedTarball/zstd/lib/decompress/huf_decompress \
+    UnpackedTarball/zstd/lib/decompress/zstd_ddict \
+    UnpackedTarball/zstd/lib/decompress/zstd_decompress \
+    UnpackedTarball/zstd/lib/decompress/zstd_decompress_block \
+))
+
+$(eval $(call gb_StaticLibrary_add_cflags,zstd,-DZSTD_DISABLE_ASM))
+
+ifeq ($(ENABLE_DEBUG),TRUE)
+$(eval $(call gb_StaticLibrary_add_cflags,zstd,-DZSTD_DEBUG=1))
+endif
+
+# vim: set noet sw=4 ts=4:

external/zstd/UnpackedTarball_zstd.mk

@@ -0,0 +1,14 @@
+# -*- Mode: makefile-gmake; tab-width: 4; indent-tabs-mode: t -*-
+#
+# This file is part of the LibreOffice project.
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+#
+
+$(eval $(call gb_UnpackedTarball_UnpackedTarball,zstd))
+
+$(eval $(call gb_UnpackedTarball_set_tarball,zstd,$(ZSTD_TARBALL)))
+
+# vim: set noet sw=4 ts=4:

include/package/InflateZstd.hxx

@@ -0,0 +1,48 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#pragma once
+
+#include <memory>
+#include <package/Inflater.hxx>
+#include <zstd.h>
+#include <zstd_errors.h>
+
+namespace ZipUtils
+{
+class DLLPUBLIC_PACKAGE InflateZstd : public Inflater
+{
+private:
+    bool bFinished;
+    bool bNeedDict;
+    sal_Int32 nLastInflateError;
+    css::uno::Sequence<sal_Int8> sInBuffer;
+    ZSTD_DCtx* pDCtx;
+    ZSTD_inBuffer inBuffer;
+    bool bStreamInitialized;
+
+    sal_Int32 doInflateBytes(css::uno::Sequence<sal_Int8>& rBuffer, sal_Int32 nNewOffset,
+                             sal_Int32 nNewLength);
+
+public:
+    explicit InflateZstd(bool bNoWrap = false);
+    virtual ~InflateZstd() override;
+
+    virtual void setInput(const css::uno::Sequence<sal_Int8>& rBuffer) override;
+    virtual bool needsDictionary() const override { return bNeedDict; }
+    virtual bool finished() const override { return bFinished; }
+    virtual sal_Int32 doInflateSegment(css::uno::Sequence<sal_Int8>& rBuffer, sal_Int32 nNewOffset,
+                                       sal_Int32 nNewLength) override;
+    virtual void end() override final;
+    virtual sal_Int32 getLastInflateError() const override { return nLastInflateError; }
+};
+
+} // namespace ZipUtils
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */

package/Library_package2.mk

@@ -43,6 +43,7 @@ $(eval $(call gb_Library_use_libraries,package2,\
 $(eval $(call gb_Library_use_externals,package2,\
 	argon2 \
 	zlib \
+	zstd \
 ))
 
 $(eval $(call gb_Library_add_exception_objects,package2,\
@@ -56,7 +57,9 @@ $(eval $(call gb_Library_add_exception_objects,package2,\
 	package/source/zipapi/CRC32 \
 	package/source/zipapi/Deflater \
 	package/source/zipapi/InflaterBytesZlib \
+	package/source/zipapi/InflaterBytesZstd \
 	package/source/zipapi/InflateZlib \
+	package/source/zipapi/InflateZstd \
 	package/source/zipapi/sha1context \
 	package/source/zipapi/ThreadedDeflater \
 	package/source/zipapi/XBufferedThreadedStream \

package/inc/InflaterBytesZstd.hxx

@@ -0,0 +1,43 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#pragma once
+
+#include <memory>
+#include <package/Inflater.hxx>
+#include <zstd.h>
+
+namespace ZipUtils
+{
+class DLLPUBLIC_PACKAGE InflaterBytesZstd : public InflaterBytes
+{
+private:
+    bool bFinished;
+    const sal_Int8* sInBuffer;
+    ZSTD_DCtx* pDCtx;
+    sal_Int32 nLastInflateError;
+    ZSTD_inBuffer inBuffer;
+    bool bStreamInitialized;
+
+    sal_Int32 doInflateBytes(sal_Int8* pOutBuffer, sal_Int32 nNewOffset, sal_Int32 nNewLength);
+
+public:
+    InflaterBytesZstd();
+    virtual ~InflaterBytesZstd() override;
+
+    virtual void setInput(const sal_Int8* pBuffer, sal_Int32 nLen) override;
+    virtual bool finished() const override { return bFinished; }
+    virtual sal_Int32 doInflateSegment(sal_Int8* pOutBuffer, sal_Int32 nBufLen,
+                                       sal_Int32 nNewOffset, sal_Int32 nNewLength) override;
+    virtual void end() override final;
+};
+
+} // namespace ZipUtils
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */

package/source/zipapi/InflateZstd.cxx

@@ -0,0 +1,94 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <package/InflateZstd.hxx>
+#include <string.h>
+
+using namespace com::sun::star::uno;
+using namespace ZipUtils;
+
+InflateZstd::InflateZstd(bool)
+    : bFinished(false)
+    , bNeedDict(false)
+    , nLastInflateError(0)
+    , pDCtx(ZSTD_createDCtx())
+    , bStreamInitialized(false)
+{
+    if (!pDCtx)
+    {
+        nLastInflateError = static_cast<sal_Int32>(ZSTD_error_memory_allocation);
+    }
+    inBuffer = { nullptr, 0, 0 };
+}
+
+InflateZstd::~InflateZstd() { end(); }
+
+void InflateZstd::setInput(const Sequence<sal_Int8>& rBuffer)
+{
+    if (!pDCtx)
+    {
+        bStreamInitialized = false;
+        return;
+    }
+    sInBuffer = rBuffer;
+    inBuffer.src = sInBuffer.getConstArray();
+    inBuffer.size = sInBuffer.getLength();
+    inBuffer.pos = 0;
+    bStreamInitialized = true;
+}
+
+sal_Int32 InflateZstd::doInflateSegment(Sequence<sal_Int8>& rBuffer, sal_Int32 nNewOffset,
+                                        sal_Int32 nNewLength)
+{
+    if (nNewOffset < 0 || nNewLength < 0 || nNewOffset + nNewLength > rBuffer.getLength())
+        return 0;
+
+    return doInflateBytes(rBuffer, nNewOffset, nNewLength);
+}
+
+void InflateZstd::end()
+{
+    if (pDCtx)
+    {
+        ZSTD_freeDCtx(pDCtx);
+        pDCtx = nullptr;
+    }
+    bStreamInitialized = false;
+    inBuffer = { nullptr, 0, 0 };
+}
+
+sal_Int32 InflateZstd::doInflateBytes(Sequence<sal_Int8>& rBuffer, sal_Int32 nNewOffset,
+                                      sal_Int32 nNewLength)
+{
+    if (bFinished)
+    {
+        return 0;
+    }
+    if (!pDCtx || !bStreamInitialized)
+    {
+        nLastInflateError = 1;
+        return 0;
+    }
+    nLastInflateError = 0;
+    ZSTD_outBuffer outBuffer
+        = { rBuffer.getArray() + nNewOffset, static_cast<size_t>(nNewLength), 0 };
+    size_t ret = ZSTD_decompressStream(pDCtx, &outBuffer, &inBuffer);
+    if (ZSTD_isError(ret))
+    {
+        nLastInflateError = static_cast<sal_Int32>(ret);
+        ZSTD_DCtx_reset(pDCtx, ZSTD_reset_session_only);
+        return 0;
+    }
+    if (ret == 0)
+        bFinished = true;
+
+    return static_cast<sal_Int32>(outBuffer.pos);
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */

package/source/zipapi/InflaterBytesZstd.cxx

@@ -0,0 +1,82 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <InflaterBytesZstd.hxx>
+#include <string.h>
+
+using namespace ZipUtils;
+
+InflaterBytesZstd::InflaterBytesZstd()
+    : bFinished(false)
+    , sInBuffer(nullptr)
+    , pDCtx(ZSTD_createDCtx())
+    , nLastInflateError(0)
+    , bStreamInitialized(false)
+{
+    inBuffer = { nullptr, 0, 0 };
+}
+
+InflaterBytesZstd::~InflaterBytesZstd() { end(); }
+
+void InflaterBytesZstd::setInput(const sal_Int8* rBuffer, sal_Int32 nBufLen)
+{
+    sInBuffer = rBuffer;
+    inBuffer.src = sInBuffer;
+    inBuffer.size = nBufLen;
+    inBuffer.pos = 0;
+    bStreamInitialized = true;
+}
+
+sal_Int32 InflaterBytesZstd::doInflateSegment(sal_Int8* pOutBuffer, sal_Int32 nBufLen,
+                                              sal_Int32 nNewOffset, sal_Int32 nNewLength)
+{
+    if (nNewOffset < 0 || nNewLength < 0 || nNewOffset + nNewLength > nBufLen)
+        return 0;
+
+    return doInflateBytes(pOutBuffer, nNewOffset, nNewLength);
+}
+
+void InflaterBytesZstd::end()
+{
+    if (pDCtx)
+    {
+        ZSTD_freeDCtx(pDCtx);
+        pDCtx = nullptr;
+    }
+    bStreamInitialized = false;
+    inBuffer = { nullptr, 0, 0 };
+}
+
+sal_Int32 InflaterBytesZstd::doInflateBytes(sal_Int8* pOutBuffer, sal_Int32 nNewOffset,
+                                            sal_Int32 nNewLength)
+{
+    if (!pDCtx || !bStreamInitialized)
+        return 0;
+
+    ZSTD_outBuffer outBuffer = { pOutBuffer + nNewOffset, static_cast<size_t>(nNewLength), 0 };
+    size_t ret = ZSTD_decompressStream(pDCtx, &outBuffer, &inBuffer);
+    if (ZSTD_isError(ret))
+    {
+        nLastInflateError = static_cast<sal_Int32>(ret);
+        ZSTD_DCtx_reset(pDCtx, ZSTD_reset_session_only);
+        return 0;
+    }
+    if (ret != 0)
+    {
+        ZSTD_DCtx_reset(pDCtx, ZSTD_reset_session_only);
+        return static_cast<sal_Int32>(outBuffer.pos);
+    }
+    if (ret == 0)
+        bFinished = true;
+    nLastInflateError = 0;
+
+    return static_cast<sal_Int32>(outBuffer.pos);
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */