content_encoding: add zstd decoding support

include zstd curl patch for Makefile.m32 from vszakats
and include Add CMake support for zstd from Peter Wu

Helped-by: Viktor Szakats
Helped-by: Peter Wu
Closes #5453

.azure-pipelines.yml

@@ -76,7 +76,7 @@ stages:
           configure: --enable-debug --disable-shared --disable-threaded-resolver --enable-alt-svc
           tflags: -n -t --shallow=40 !FTP
     steps:
-    - script: sudo apt-get update && sudo apt-get install -y stunnel4 python-impacket $(install)
+    - script: sudo apt-get update && sudo apt-get install -y stunnel4 python-impacket libzstd-dev libbrotli-dev $(install)
       displayName: 'apt install'
 
     - script: ./buildconf && ./configure $(configure)

.travis.yml

@@ -94,6 +94,7 @@ jobs:
         - *common_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=novalgrind BORINGSSL=yes C="--with-ssl=$HOME/boringssl" LD_LIBRARY_PATH=/home/travis/boringssl/lib:/usr/local/lib
     - OVERRIDE_CC="CC=gcc-8" OVERRIDE_CXX="CXX=g++-8"
@@ -111,6 +112,7 @@ jobs:
         - *common_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=novalgrind NGTCP2=yes C="--with-ssl=$HOME/ngbuild --with-ngtcp2=$HOME/ngbuild --with-nghttp3=$HOME/ngbuild --enable-alt-svc" NOTESTS=
     - OVERRIDE_CC="CC=gcc-8" OVERRIDE_CXX="CXX=g++-8"
@@ -121,6 +123,7 @@ jobs:
         - *common_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=novalgrind NGTCP2=yes GNUTLS=yes C="PKG_CONFIG_PATH=$HOME/ngbuild --without-ssl --with-gnutls=$HOME/ngbuild --with-ngtcp2=$HOME/ngbuild --with-nghttp3=$HOME/ngbuild --enable-alt-svc" NOTESTS=
     - OVERRIDE_CC="CC=gcc-8" OVERRIDE_CXX="CXX=g++-8"
@@ -131,6 +134,7 @@ jobs:
         - *common_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
         - autogen
         - automake
         - autopoint
@@ -151,6 +155,7 @@ jobs:
         - *common_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=debug-mesalink C="--with-mesalink --without-ssl"
     - OVERRIDE_CC="CC=gcc-8" OVERRIDE_CXX="CXX=g++-8"
@@ -161,6 +166,7 @@ jobs:
         - *common_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=debug
     - &clang OVERRIDE_CC="CC=clang-9" OVERRIDE_CXX="CXX=clang++-9"
@@ -172,6 +178,7 @@ jobs:
         - &clang_packages [*common_packages, clang-9]
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=debug C="--enable-alt-svc"
     - *clang
@@ -183,6 +190,7 @@ jobs:
         - *clang_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=debug C="--with-mbedtls --without-ssl"
     - *clang
@@ -194,6 +202,7 @@ jobs:
         - *clang_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
         - libmbedtls-dev
   - env:
     - T=debug C="--with-gnutls --without-ssl"
@@ -207,6 +216,7 @@ jobs:
         - libgnutls28-dev
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=debug C="--with-nss --without-ssl" NOTESTS=1 CPPFLAGS="-isystem /usr/include/nss"
     - *clang
@@ -219,11 +229,12 @@ jobs:
         - libnss3-dev
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=iconv
     - OVERRIDE_CC="CC=gcc-8" OVERRIDE_CXX="CXX=g++-8"
   - env:
-    - T=cmake BORINGSSL=yes QUICHE=yes C="-DUSE_QUICHE=1 -DOPENSSL_ROOT_DIR=$HOME/boringssl"
+    - T=cmake BORINGSSL=yes QUICHE=yes C="-DUSE_QUICHE=1 -DOPENSSL_ROOT_DIR=$HOME/boringssl -DCURL_BROTLI=1 -DCURL_ZSTD=1"
     - OVERRIDE_CC="CC=gcc-8" OVERRIDE_CXX="CXX=g++-8"
     - PKG_CONFIG_PATH="$HOME/quiche/target/release"
     before_install:
@@ -235,8 +246,9 @@ jobs:
         - *common_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
-    - T=cmake NGTCP2=yes C="-DUSE_NGTCP2=ON"
+    - T=cmake NGTCP2=yes C="-DUSE_NGTCP2=ON -DCURL_BROTLI=1 -DCURL_ZSTD=1"
     - *clang
     - PKG_CONFIG_PATH="$HOME/ngbuild/lib/pkgconfig"
     compiler: clang
@@ -247,6 +259,7 @@ jobs:
         - *clang_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=torture
     - OVERRIDE_CC="CC=gcc-8" OVERRIDE_CXX="CXX=g++-8"
@@ -258,6 +271,7 @@ jobs:
         - lcov
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
         - libssh2-1-dev
   - env:
     - T=distcheck
@@ -269,6 +283,7 @@ jobs:
         - *common_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=fuzzer
     - *clang
@@ -280,6 +295,7 @@ jobs:
         - *clang_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=tidy
     - *clang
@@ -292,6 +308,7 @@ jobs:
         - clang-tidy-9
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=scan-build
     - *clang
@@ -303,6 +320,7 @@ jobs:
         - *clang_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=debug CFLAGS="-fsanitize=address,undefined,signed-integer-overflow -fno-sanitize-recover=undefined,integer -Wformat -Werror=format-security -Werror=array-bounds -g" LDFLAGS="-fsanitize=address,undefined -fno-sanitize-recover=undefined,integer" LIBS="-ldl -lubsan"
     - *clang
@@ -314,6 +332,7 @@ jobs:
         - *clang_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
   - env:
     - T=debug C="--enable-alt-svc"
     - OVERRIDE_CC="CC=gcc-8" OVERRIDE_CXX="CXX=g++-8"
@@ -325,6 +344,7 @@ jobs:
         - *common_packages
         - libpsl-dev
         - libbrotli-dev
+        - libzstd-dev
         - libev-dev
         - libssl-dev
         - libtool

CMake/FindZstd.cmake

@@ -0,0 +1,69 @@
+#***************************************************************************
+#                                  _   _ ____  _
+#  Project                     ___| | | |  _ \| |
+#                             / __| | | | |_) | |
+#                            | (__| |_| |  _ <| |___
+#                             \___|\___/|_| \_\_____|
+#
+# Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
+#
+# This software is licensed as described in the file COPYING, which
+# you should have received as part of this distribution. The terms
+# are also available at https://curl.haxx.se/docs/copyright.html.
+#
+# You may opt to use, copy, modify, merge, publish, distribute and/or sell
+# copies of the Software, and permit persons to whom the Software is
+# furnished to do so, under the terms of the COPYING file.
+#
+# This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+# KIND, either express or implied.
+#
+###########################################################################
+
+#[=======================================================================[.rst:
+FindZstd
+----------
+
+Find the zstd library
+
+Result Variables
+^^^^^^^^^^^^^^^^
+
+``Zstd_FOUND``
+  System has zstd
+``Zstd_INCLUDE_DIRS``
+  The zstd include directories.
+``Zstd_LIBRARIES``
+  The libraries needed to use zstd
+#]=======================================================================]
+
+if(UNIX)
+  find_package(PkgConfig QUIET)
+  pkg_search_module(PC_Zstd libzstd)
+endif()
+
+find_path(Zstd_INCLUDE_DIR zstd.h
+  HINTS
+    ${PC_Zstd_INCLUDEDIR}
+    ${PC_Zstd_INCLUDE_DIRS}
+)
+
+find_library(Zstd_LIBRARY NAMES zstd
+  HINTS
+    ${PC_Zstd_LIBDIR}
+    ${PC_Zstd_LIBRARY_DIRS}
+)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(Zstd
+  REQUIRED_VARS
+    Zstd_LIBRARY
+    Zstd_INCLUDE_DIR
+)
+
+if(Zstd_FOUND)
+  set(Zstd_LIBRARIES    ${Zstd_LIBRARY})
+  set(Zstd_INCLUDE_DIRS ${Zstd_INCLUDE_DIR})
+endif()
+
+mark_as_advanced(Zstd_INCLUDE_DIRS Zstd_LIBRARIES)

CMakeLists.txt

@@ -641,6 +641,22 @@ if(CURL_BROTLI)
   endif()
 endif()
 
+option(CURL_ZSTD "Set to ON to enable building curl with zstd support." OFF)
+set(HAVE_ZSTD OFF)
+if(CURL_ZSTD)
+  find_package(Zstd REQUIRED)
+  cmake_push_check_state()
+  set(CMAKE_REQUIRED_INCLUDES ${Zstd_INCLUDE_DIRS})
+  set(CMAKE_REQUIRED_LIBRARIES ${Zstd_LIBRARIES})
+  check_symbol_exists(ZSTD_createDStream "zstd.h" HAVE_ZSTD_CREATEDSTREAM)
+  cmake_pop_check_state()
+  if(Zstd_FOUND AND HAVE_ZSTD_CREATEDSTREAM)
+    set(HAVE_ZSTD ON)
+    list(APPEND CURL_LIBS ${Zstd_LIBRARIES})
+    include_directories(${Zstd_INCLUDE_DIRS})
+  endif()
+endif()
+
 #libSSH2
 option(CMAKE_USE_LIBSSH2 "Use libSSH2" ON)
 mark_as_advanced(CMAKE_USE_LIBSSH2)
@@ -1322,6 +1338,8 @@ _add_if("SSL"           SSL_ENABLED)
 _add_if("IPv6"          ENABLE_IPV6)
 _add_if("unix-sockets"  USE_UNIX_SOCKETS)
 _add_if("libz"          HAVE_LIBZ)
+_add_if("brotli"        HAVE_BROTLI)
+_add_if("zstd"          HAVE_ZSTD)
 _add_if("AsynchDNS"     USE_ARES OR USE_THREADS_POSIX OR USE_THREADS_WIN32)
 _add_if("IDN"           HAVE_LIBIDN2)
 _add_if("Largefile"     (CURL_SIZEOF_CURL_OFF_T GREATER 4) AND

configure.ac

@@ -1115,6 +1115,93 @@ if test X"$OPT_BROTLI" != Xno; then
   fi
 fi
 
+dnl **********************************************************************
+dnl Check for libzstd
+dnl **********************************************************************
+
+dnl Default to compiler & linker defaults for libzstd
+OPT_ZSTD=off
+AC_ARG_WITH(zstd,dnl
+AC_HELP_STRING([--with-zstd=PATH],[Where to look for libzstd, PATH points to the libzstd installation; when possible, set the PKG_CONFIG_PATH environment variable instead of using this option])
+AC_HELP_STRING([--without-zstd], [disable libzstd]),
+  OPT_ZSTD=$withval)
+
+if test X"$OPT_ZSTD" != Xno; then
+  dnl backup the pre-zstd variables
+  CLEANLDFLAGS="$LDFLAGS"
+  CLEANCPPFLAGS="$CPPFLAGS"
+  CLEANLIBS="$LIBS"
+
+  case "$OPT_ZSTD" in
+  yes)
+    dnl --with-zstd (without path) used
+    CURL_CHECK_PKGCONFIG(libzstd)
+
+    if test "$PKGCONFIG" != "no" ; then
+      LIB_ZSTD=`$PKGCONFIG --libs-only-l libzstd`
+      LD_ZSTD=`$PKGCONFIG --libs-only-L libzstd`
+      CPP_ZSTD=`$PKGCONFIG --cflags-only-I libzstd`
+      version=`$PKGCONFIG --modversion libzstd`
+      DIR_ZSTD=`echo $LD_ZSTD | $SED -e 's/-L//'`
+    fi
+
+    ;;
+  off)
+    dnl no --with-zstd option given, just check default places
+    ;;
+  *)
+    dnl use the given --with-zstd spot
+    PREFIX_ZSTD=$OPT_ZSTD
+    ;;
+  esac
+
+  dnl if given with a prefix, we set -L and -I based on that
+  if test -n "$PREFIX_ZSTD"; then
+    LIB_ZSTD="-lzstd"
+    LD_ZSTD=-L${PREFIX_ZSTD}/lib$libsuff
+    CPP_ZSTD=-I${PREFIX_ZSTD}/include
+    DIR_ZSTD=${PREFIX_ZSTD}/lib$libsuff
+  fi
+
+  LDFLAGS="$LDFLAGS $LD_ZSTD"
+  CPPFLAGS="$CPPFLAGS $CPP_ZSTD"
+  LIBS="$LIB_ZSTD $LIBS"
+
+  AC_CHECK_LIB(zstd, ZSTD_createDStream)
+
+  AC_CHECK_HEADERS(zstd.h,
+    curl_zstd_msg="enabled (libzstd)"
+    HAVE_ZSTD=1
+    AC_DEFINE(HAVE_ZSTD, 1, [if libzstd is in use])
+    AC_SUBST(HAVE_ZSTD, [1])
+  )
+
+  if test X"$OPT_ZSTD" != Xoff &&
+     test "$HAVE_ZSTD" != "1"; then
+    AC_MSG_ERROR([libzstd was not found where specified!])
+  fi
+
+  if test "$HAVE_ZSTD" = "1"; then
+    if test -n "$DIR_ZSTD"; then
+       dnl when the zstd shared lib were found in a path that the run-time
+       dnl linker doesn't search through, we need to add it to
+       dnl CURL_LIBRARY_PATH to prevent further configure tests to fail due to
+       dnl this
+
+       if test "x$cross_compiling" != "xyes"; then
+         CURL_LIBRARY_PATH="$CURL_LIBRARY_PATH:$DIR_ZSTD"
+         export CURL_LIBRARY_PATH
+         AC_MSG_NOTICE([Added $DIR_ZSTD to CURL_LIBRARY_PATH])
+       fi
+    fi
+  else
+    dnl no zstd, revert back to clean variables
+    LDFLAGS=$CLEANLDFLAGS
+    CPPFLAGS=$CLEANCPPFLAGS
+    LIBS=$CLEANLIBS
+  fi
+fi
+
 dnl **********************************************************************
 dnl Check for LDAP
 dnl **********************************************************************
@@ -4825,6 +4912,9 @@ fi
 if test "x$HAVE_BROTLI" = "x1"; then
   SUPPORT_FEATURES="$SUPPORT_FEATURES brotli"
 fi
+if test "x$HAVE_ZSTD" = "x1"; then
+  SUPPORT_FEATURES="$SUPPORT_FEATURES zstd"
+fi
 if test "x$USE_ARES" = "x1" -o "x$USE_THREADS_POSIX" = "x1" \
                             -o "x$USE_THREADS_WIN32" = "x1"; then
   SUPPORT_FEATURES="$SUPPORT_FEATURES AsynchDNS"
@@ -5067,6 +5157,7 @@ AC_MSG_NOTICE([Configured to build curl/libcurl:
   SSH:              ${curl_ssh_msg}
   zlib:             ${curl_zlib_msg}
   brotli:           ${curl_brotli_msg}
+  zstd:             ${curl_zstd_msg}
   GSS-API:          ${curl_gss_msg}
   TLS-SRP:          ${curl_tls_srp_msg}
   resolver:         ${curl_res_msg}

docs/examples/Makefile.m32

@@ -24,7 +24,7 @@
 #
 ## Makefile for building curl examples with MingW (GCC-3.2 or later)
 ## and optionally OpenSSL (1.0.2a), libssh2 (1.5), zlib (1.2.8), librtmp (2.4),
-## brotli (1.0.1)
+## brotli (1.0.1), zstd (1.4.5)
 ##
 ## Usage:   mingw32-make -f Makefile.m32 CFG=-feature1[-feature2][-feature3][...]
 ## Example: mingw32-make -f Makefile.m32 CFG=-zlib-ssl-sspi-winidn
@@ -39,6 +39,10 @@
 ifndef ZLIB_PATH
 ZLIB_PATH = ../../../zlib-1.2.8
 endif
+# Edit the path below to point to the base of your Zstandard sources.
+ifndef ZSTD_PATH
+ZSTD_PATH = ../../../zstd-1.4.5
+endif
 # Edit the path below to point to the base of your Brotli sources.
 ifndef BROTLI_PATH
 BROTLI_PATH = ../../../brotli-1.0.1
@@ -180,6 +184,9 @@ endif
 ifeq ($(findstring -zlib,$(CFG)),-zlib)
 ZLIB = 1
 endif
+ifeq ($(findstring -zstd,$(CFG)),-zstd)
+ZSTD = 1
+endif
 ifeq ($(findstring -brotli,$(CFG)),-brotli)
 BROTLI = 1
 endif
@@ -284,6 +291,11 @@ ifdef ZLIB
   CFLAGS += -DHAVE_LIBZ -DHAVE_ZLIB_H
   curl_LDADD += -L"$(ZLIB_PATH)" -lz
 endif
+ifdef ZSTD
+  INCLUDES += -I"$(ZSTD_PATH)/include"
+  CFLAGS += -DHAVE_ZSTD
+  curl_LDADD += -L"$(ZSTD_PATH)/lib" -lzstd
+endif
 ifdef BROTLI
   INCLUDES += -I"$(BROTLI_PATH)/include"
   CFLAGS += -DHAVE_BROTLI

docs/libcurl/curl_version_info.3

@@ -92,6 +92,11 @@ typedef struct {
                                   be NULL */
   const char *capath;          /* the built-in default CURLOPT_CAPATH, might
                                   be NULL */
+  /* when 'age' is CURLVERSION_EIGHTH or higher (>= 7.71.0), the members
+     below exist */
+  unsigned int zstd_ver_num; /* Numeric Zstd version
+                                  (MAJOR << 24) | (MINOR << 12) | PATCH */
+  const char *zstd_version; /* human readable string. */
 } curl_version_info_data;
 .fi
 
@@ -121,6 +126,8 @@ more exact timeouts (even on Windows) and less blocking when using the multi
 interface. (added in 7.10.7)
 .IP CURL_VERSION_BROTLI
 supports HTTP Brotli content encoding using libbrotlidec (Added in 7.57.0)
+.IP CURL_VERSION_ZSTD
+supports HTTP zstd content encoding using zstd library (Added in 7.72.0)
 .IP CURL_VERSION_CONV
 libcurl was built with support for character conversions, as provided by the
 CURLOPT_CONV_* callbacks. (Added in 7.15.4)

docs/libcurl/opts/CURLOPT_ACCEPT_ENCODING.3

@@ -45,8 +45,9 @@ Alternatively, you can specify exactly the encoding or list of encodings you
 want in the response. Four encodings are supported: \fIidentity\fP, meaning
 non-compressed, \fIdeflate\fP which requests the server to compress its
 response using the zlib algorithm, \fIgzip\fP which requests the gzip
-algorithm and (since curl 7.57.0) \fIbr\fP which is brotli.  Provide them in
+algorithm, (since curl 7.57.0) \fIbr\fP which is brotli and (since curl
-the string as a comma-separated list of accepted encodings, like:
+7.72.0) \fIzstd\fP which is zstd.  Provide them in the string as a
+comma-separated list of accepted encodings, like:
 
   "br, gzip, deflate".
 
@@ -94,8 +95,9 @@ if(curl) {
 This option was called CURLOPT_ENCODING before 7.21.6
 
 The specific libcurl you're using must have been built with zlib to be able to
-decompress gzip and deflate responses and with the brotli library to
+decompress gzip and deflate responses, with the brotli library to
-decompress brotli responses.
+decompress brotli responses and with the zstd library to decompress zstd
+responses.
 .SH RETURN VALUE
 Returns CURLE_OK if the option is supported, CURLE_UNKNOWN_OPTION if not, or
 CURLE_OUT_OF_MEMORY if there was insufficient heap space.

docs/libcurl/symbols-in-versions

@@ -803,6 +803,7 @@ CURLU_NO_DEFAULT_PORT           7.62.0
 CURLU_PATH_AS_IS                7.62.0
 CURLU_URLDECODE                 7.62.0
 CURLU_URLENCODE                 7.62.0
+CURLVERSION_EIGHTH              7.72.0
 CURLVERSION_FIFTH               7.57.0
 CURLVERSION_FIRST               7.10
 CURLVERSION_FOURTH              7.16.1
@@ -968,6 +969,7 @@ CURL_VERSION_SSL                7.10
 CURL_VERSION_SSPI               7.13.2
 CURL_VERSION_TLSAUTH_SRP        7.21.4
 CURL_VERSION_UNIX_SOCKETS       7.40.0
+CURL_VERSION_ZSTD               7.72.0
 CURL_WAIT_POLLIN                7.28.0
 CURL_WAIT_POLLOUT               7.28.0
 CURL_WAIT_POLLPRI               7.28.0

include/curl/curl.h

@@ -2748,6 +2748,7 @@ typedef enum {
   CURLVERSION_FIFTH,
   CURLVERSION_SIXTH,
   CURLVERSION_SEVENTH,
+  CURLVERSION_EIGHTH,
   CURLVERSION_LAST /* never actually use this */
 } CURLversion;
 
@@ -2756,7 +2757,7 @@ typedef enum {
    meant to be a built-in version number for what kind of struct the caller
    expects. If the struct ever changes, we redefine the NOW to another enum
    from above. */
-#define CURLVERSION_NOW CURLVERSION_SEVENTH
+#define CURLVERSION_NOW CURLVERSION_EIGHTH
 
 struct curl_version_info_data {
   CURLversion age;          /* age of the returned struct */
@@ -2802,6 +2803,11 @@ struct curl_version_info_data {
   const char *capath;          /* the built-in default CURLOPT_CAPATH, might
                                   be NULL */
 
+  /* These fields were added in CURLVERSION_EIGHTH */
+  unsigned int zstd_ver_num; /* Numeric Zstd version
+                                  (MAJOR << 24) | (MINOR << 12) | PATCH */
+  const char *zstd_version; /* human readable string. */
+
 };
 typedef struct curl_version_info_data curl_version_info_data;
 
@@ -2836,7 +2842,7 @@ typedef struct curl_version_info_data curl_version_info_data;
 #define CURL_VERSION_BROTLI       (1<<23) /* Brotli features are present. */
 #define CURL_VERSION_ALTSVC       (1<<24) /* Alt-Svc handling built-in */
 #define CURL_VERSION_HTTP3        (1<<25) /* HTTP3 support built-in */
-
+#define CURL_VERSION_ZSTD         (1<<26) /* zstd features are present */
  /*
  * NAME curl_version_info()
  *

lib/Makefile.m32

@@ -24,7 +24,7 @@
 #
 ## Makefile for building libcurl.a with MingW (GCC-3.2 or later or LLVM/Clang)
 ## and optionally OpenSSL (1.0.2a), libssh2 (1.5), zlib (1.2.8), librtmp (2.4),
-## brotli (1.0.1)
+## brotli (1.0.1), zstd (1.4.5)
 ##
 ## Usage:   mingw32-make -f Makefile.m32 CFG=-feature1[-feature2][-feature3][...]
 ## Example: mingw32-make -f Makefile.m32 CFG=-zlib-ssl-sspi-winidn
@@ -39,6 +39,10 @@
 ifndef ZLIB_PATH
 ZLIB_PATH = ../../zlib-1.2.8
 endif
+# Edit the path below to point to the base of your Zstandard sources.
+ifndef ZSTD_PATH
+ZSTD_PATH = ../../zstd-1.4.5
+endif
 # Edit the path below to point to the base of your Brotli sources.
 ifndef BROTLI_PATH
 BROTLI_PATH = ../../brotli-1.0.1
@@ -180,6 +184,9 @@ endif
 ifeq ($(findstring -zlib,$(CFG)),-zlib)
 ZLIB = 1
 endif
+ifeq ($(findstring -zstd,$(CFG)),-zstd)
+ZSTD = 1
+endif
 ifeq ($(findstring -brotli,$(CFG)),-brotli)
 BROTLI = 1
 endif
@@ -288,6 +295,11 @@ ifdef ZLIB
   CFLAGS += -DHAVE_LIBZ -DHAVE_ZLIB_H
   DLL_LIBS += -L"$(ZLIB_PATH)" -lz
 endif
+ifdef ZSTD
+  INCLUDES += -I"$(ZSTD_PATH)/include"
+  CFLAGS += -DHAVE_ZSTD
+  DLL_LIBS += -L"$(ZSTD_PATH)/lib" -lzstd
+endif
 ifdef BROTLI
   INCLUDES += -I"$(BROTLI_PATH)/include"
   CFLAGS += -DHAVE_BROTLI

lib/content_encoding.c

@@ -38,6 +38,10 @@
 #include <brotli/decode.h>
 #endif
 
+#ifdef HAVE_ZSTD
+#include <zstd.h>
+#endif
+
 #include "sendf.h"
 #include "http.h"
 #include "content_encoding.h"
@@ -710,6 +714,95 @@ static const struct content_encoding brotli_encoding = {
 #endif
 
 
+#ifdef HAVE_ZSTD
+/* Writer parameters. */
+struct zstd_params {
+  ZSTD_DStream *zds;    /* State structure for zstd. */
+  void *decomp;
+};
+
+static CURLcode zstd_init_writer(struct connectdata *conn,
+                                 struct contenc_writer *writer)
+{
+  struct zstd_params *zp = (struct zstd_params *)&writer->params;
+  (void)conn;
+
+  if(!writer->downstream)
+    return CURLE_WRITE_ERROR;
+
+  zp->zds = ZSTD_createDStream();
+  zp->decomp = NULL;
+  return zp->zds ? CURLE_OK : CURLE_OUT_OF_MEMORY;
+}
+
+static CURLcode zstd_unencode_write(struct connectdata *conn,
+    struct contenc_writer *writer,
+    const char *buf, size_t nbytes)
+{
+  CURLcode result = CURLE_OK;
+  struct zstd_params *zp = (struct zstd_params *)&writer->params;
+  ZSTD_inBuffer in;
+  ZSTD_outBuffer out;
+  size_t errorCode;
+
+  if(!zp->decomp) {
+    zp->decomp = malloc(DSIZ);
+    if(!zp->decomp)
+      return CURLE_OUT_OF_MEMORY;
+  }
+  in.pos = 0;
+  in.src = buf;
+  in.size = nbytes;
+
+  for(;;) {
+    out.pos = 0;
+    out.dst = zp->decomp;
+    out.size = DSIZ;
+
+    errorCode = ZSTD_decompressStream(zp->zds, &out, &in);
+    if(ZSTD_isError(errorCode)) {
+      return CURLE_BAD_CONTENT_ENCODING;
+    }
+    if(out.pos > 0) {
+      result = Curl_unencode_write(conn, writer->downstream,
+                                   zp->decomp, out.pos);
+      if(result)
+        break;
+    }
+    if((in.pos == nbytes) && (out.pos < out.size))
+      break;
+  }
+
+  return result;
+}
+
+static void zstd_close_writer(struct connectdata *conn,
+    struct contenc_writer *writer)
+{
+  struct zstd_params *zp = (struct zstd_params *)&writer->params;
+  (void)conn;
+
+  if(zp->decomp) {
+    free(zp->decomp);
+    zp->decomp = NULL;
+  }
+  if(zp->zds) {
+    ZSTD_freeDStream(zp->zds);
+    zp->zds = NULL;
+  }
+}
+
+static const struct content_encoding zstd_encoding = {
+  "zstd",
+  NULL,
+  zstd_init_writer,
+  zstd_unencode_write,
+  zstd_close_writer,
+  sizeof(struct zstd_params)
+};
+#endif
+
+
 /* Identity handler. */
 static CURLcode identity_init_writer(struct connectdata *conn,
                                      struct contenc_writer *writer)
@@ -751,6 +844,9 @@ static const struct content_encoding * const encodings[] = {
 #endif
 #ifdef HAVE_BROTLI
   &brotli_encoding,
+#endif
+#ifdef HAVE_ZSTD
+  &zstd_encoding,
 #endif
   NULL
 };

lib/curl_config.h.cmake

@@ -437,6 +437,9 @@
 /* if brotli is available */
 #cmakedefine HAVE_BROTLI 1
 
+/* if zstd is available */
+#cmakedefine HAVE_ZSTD 1
+
 /* if your compiler supports LL */
 #cmakedefine HAVE_LL 1
 

lib/version.c

@@ -66,6 +66,10 @@
 #include <brotli/decode.h>
 #endif
 
+#ifdef HAVE_ZSTD
+#include <zstd.h>
+#endif
+
 #ifdef HAVE_BROTLI
 static size_t brotli_version(char *buf, size_t bufsz)
 {
@@ -78,6 +82,20 @@ static size_t brotli_version(char *buf, size_t bufsz)
 }
 #endif
 
+#ifdef HAVE_ZSTD
+static size_t zstd_version(char *buf, size_t bufsz)
+{
+  unsigned long zstd_version = (unsigned long)ZSTD_versionNumber();
+  unsigned int major = (unsigned int)(zstd_version / (100 * 100));
+  unsigned int minor = (unsigned int)((zstd_version -
+                         (major * 100 * 100)) / 100);
+  unsigned int patch = (unsigned int)(zstd_version -
+                         (major * 100 * 100) - (minor * 100));
+
+  return msnprintf(buf, bufsz, "%u.%u.%u", major, minor, patch);
+}
+#endif
+
 /*
  * curl_version() returns a pointer to a static buffer.
  *
@@ -103,6 +121,9 @@ char *curl_version(void)
 #ifdef HAVE_BROTLI
   char br_version[40] = "brotli/";
 #endif
+#ifdef HAVE_ZSTD
+  char zst_version[40] = "zstd/";
+#endif
 #ifdef USE_ARES
   char cares_version[40];
 #endif
@@ -153,6 +174,10 @@ char *curl_version(void)
   brotli_version(&br_version[7], sizeof(br_version) - 7);
   src[i++] = br_version;
 #endif
+#ifdef HAVE_ZSTD
+  zstd_version(&zst_version[5], sizeof(zst_version) - 5);
+  src[i++] = zst_version;
+#endif
 #ifdef USE_ARES
   msnprintf(cares_version, sizeof(cares_version),
             "c-ares/%s", ares_version(NULL));
@@ -389,6 +414,9 @@ static curl_version_info_data version_info = {
 #if defined(HAVE_BROTLI)
   | CURL_VERSION_BROTLI
 #endif
+#if defined(HAVE_ZSTD)
+  | CURL_VERSION_ZSTD
+#endif
 #if defined(USE_ALTSVC)
   | CURL_VERSION_ALTSVC
 #endif
@@ -413,10 +441,12 @@ static curl_version_info_data version_info = {
   NULL,
 #endif
 #ifdef CURL_CA_PATH
-  CURL_CA_PATH  /* capath */
+  CURL_CA_PATH,  /* capath */
 #else
-  NULL
+  NULL,
 #endif
+  0,    /* zstd_ver_num */
+  NULL  /* zstd version */
 };
 
 curl_version_info_data *curl_version_info(CURLversion stamp)
@@ -434,6 +464,10 @@ curl_version_info_data *curl_version_info(CURLversion stamp)
 #ifdef HAVE_BROTLI
   static char brotli_buffer[80];
 #endif
+#ifdef HAVE_ZSTD
+  static char zstd_buffer[80];
+#endif
+
 
 #ifdef USE_SSL
   Curl_ssl_version(ssl_buffer, sizeof(ssl_buffer));
@@ -485,6 +519,12 @@ curl_version_info_data *curl_version_info(CURLversion stamp)
   version_info.brotli_version = brotli_buffer;
 #endif
 
+#ifdef HAVE_ZSTD
+  version_info.zstd_ver_num = (unsigned int)ZSTD_versionNumber();
+  zstd_version(zstd_buffer, sizeof(zstd_buffer));
+  version_info.zstd_version = zstd_buffer;
+#endif
+
 #ifdef USE_NGHTTP2
   {
     nghttp2_info *h2 = nghttp2_version(0);

src/Makefile.m32

@@ -24,7 +24,7 @@
 #
 ## Makefile for building curl.exe with MingW (GCC-3.2 or later or LLVM/Clang)
 ## and optionally OpenSSL (1.0.2a), libssh2 (1.5), zlib (1.2.8), librtmp (2.4),
-## brotli (1.0.1)
+## brotli (1.0.1), zstd (1.4.5)
 ##
 ## Usage:   mingw32-make -f Makefile.m32 CFG=-feature1[-feature2][-feature3][...]
 ## Example: mingw32-make -f Makefile.m32 CFG=-zlib-ssl-sspi-winidn
@@ -39,6 +39,10 @@
 ifndef ZLIB_PATH
 ZLIB_PATH = ../../zlib-1.2.8
 endif
+# Edit the path below to point to the base of your Zstandard sources.
+ifndef ZSTD_PATH
+ZSTD_PATH = ../../zstd-1.4.5
+endif
 # Edit the path below to point to the base of your Brotli sources.
 ifndef BROTLI_PATH
 BROTLI_PATH = ../../brotli-1.0.1
@@ -189,6 +193,9 @@ endif
 ifeq ($(findstring -zlib,$(CFG)),-zlib)
 ZLIB = 1
 endif
+ifeq ($(findstring -zstd,$(CFG)),-zstd)
+ZSTD = 1
+endif
 ifeq ($(findstring -brotli,$(CFG)),-brotli)
 BROTLI = 1
 endif
@@ -302,6 +309,11 @@ ifdef ZLIB
   CFLAGS += -DHAVE_LIBZ -DHAVE_ZLIB_H
   curl_LDADD += -L"$(ZLIB_PATH)" -lz
 endif
+ifdef ZSTD
+  INCLUDES += -I"$(ZSTD_PATH)/include"
+  CFLAGS += -DHAVE_ZSTD
+  curl_LDADD += -L"$(ZSTD_PATH)/lib" -lzstd
+endif
 ifdef BROTLI
   INCLUDES += -I"$(BROTLI_PATH)/include"
   CFLAGS += -DHAVE_BROTLI

src/tool_getparam.c

@@ -695,7 +695,8 @@ ParameterError getparameter(const char *flag, /* f or -long-flag */
 
       case 'j': /* --compressed */
         if(toggle &&
-           !(curlinfo->features & (CURL_VERSION_LIBZ | CURL_VERSION_BROTLI)))
+           !(curlinfo->features & (CURL_VERSION_LIBZ |
+                                   CURL_VERSION_BROTLI | CURL_VERSION_ZSTD)))
           return PARAM_LIBCURL_DOESNT_SUPPORT;
         config->encoding = toggle;
         break;

src/tool_help.c

@@ -546,6 +546,7 @@ static const struct feat feats[] = {
   {"SSL",            CURL_VERSION_SSL},
   {"libz",           CURL_VERSION_LIBZ},
   {"brotli",         CURL_VERSION_BROTLI},
+  {"zstd",           CURL_VERSION_ZSTD},
   {"CharConv",       CURL_VERSION_CONV},
   {"TLS-SRP",        CURL_VERSION_TLSAUTH_SRP},
   {"HTTP2",          CURL_VERSION_HTTP2},

tests/data/Makefile.inc

@@ -61,7 +61,7 @@ test334 test335 test336 test337 test338 test339 test340 test341 test342 \
 test343 test344 test345 test346 \
 test350 test351 test352 test353 test354 test355 test356 test357 test358 \
 test359 \
-test393 test394 test395 \
+test393 test394 test395 test396 test397 \
 \
 test400 test401 test402 test403 test404 test405 test406 test407 test408 \
 test409 \

tests/data/test396

@@ -0,0 +1,202 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+compressed
+</keywords>
+</info>
+#
+# Server-side
+<reply>
+<data base64="yes">
+SFRUUC8xLjEgMjAwIE9LDQpEYXRlOiBNb24sIDI5IE5vdiAyMDA0IDIxOjU2OjUzIEdNVA0KU2Vy
+dmVyOiBBcGFjaGUvMS4zLjMxIChEZWJpYW4gR05VL0xpbnV4KSBtb2RfZ3ppcC8xLjMuMjYuMWEg
+UEhQLzQuMy45LTEgbW9kX3NzbC8yLjguMjAgT3BlblNTTC8wLjkuN2QgbW9kX3BlcmwvMS4yOQ0K
+VmFyeTogQWNjZXB0LUVuY29kaW5nDQpDb250ZW50LVR5cGU6IHRleHQvaHRtbDsgY2hhcnNldD1J
+U08tODg1OS0xDQpDb250ZW50LUVuY29kaW5nOiB6c3RkDQpDb250ZW50LUxlbmd0aDogMTMwOQ0K
+DQootS/9ZLESfSgAhj+9KODQugGwA7ZypiefqCCMWuEChf2B/kAy8O+aCN/J85sQo2WYoY3AzAu3
+ALMArADzIbf2pNpzu3kaHt3a+7pumz3QvrNJn6zxUdptGFLvNOy67bymt1gZRqqBqhqopndRkImC
+WNNUYZLrGFaqAWoasKZHVZBrglyVCoXJljJq+kbJsKImFCan5j0IgxD2kFdKljRBHrJtWNa+0GLG
+t6t0Y2+db98wD3D3dh7PwZLBVGAep877k0Ku1hbWuWeJqMgcQCAAQAgreFCQiuS6IBAYhgcBp05p
+tdrvMUnUg6Da+d6eR7eMAhjTU/ubEztOjRRyTNXz9lh739eZvfb42ruTgRxSd+6LNDLIIdsbw3Lv
+5/fMsM699c68G27U5mZebw1yXDCYbOvqdSvdYvxH7kWyt+7bIUcko6Vc977nhbXai24X3bccJD5K
+GwNyfHyRhGUhAkIhslwYEl4UYYBweVHG8nCxZF6UOWBASIAcUUQm4UWYKCKTWXh/3XJc9+8yPCkj
+3qrx30GObzo3Ht/Px1B6783X6PddJCZey7W1Se0G2a373CC/5z3vYYj1x47mHWT5WcbbjLdZy6zl
+xvnGOWSOpc2psaNx88PNT/XJqk/24dwP50Jmn7K9N9thyPxYcyKnod4xvLSLm0bANB2tRs8i2Fc7
+Lzdd+6x7hpGLIVVht3ZW0zCcJNIVnaFkYkhdUoRiaEkkqyKZeKQdZzmGlQmFXdToDCeUFMFubc2b
+Y0iRSNZFkWDtVnuNxp003ulhCDmkv7W3aj0MIYzht0eIVkUklkWj3GYvUKypimSTfihJpKIi1kSj
+ZSgQ8C4YTG3uzsvQmlgUTE6G00Num9XaHwTNadyn0VOrLWtzLSHDiISaKlfFmlDTNFXUdVGRSVUx
+rDzW7411btMZMkPvigGBNbXOkL0lJ2Yb1DuGHO+s9sU82rPGd9u5XWSIZVvXuZprO1+7XXvIckqu
+aUJhWEkVJVEwTdN2zWV4eVs3r9uv9uBRcIbBAesPgOiggZVzaGZABgAggEEBQELCICNKAyHz5wz5
+Gr+3SMoKzoiT4JcFlMRJ8E0BVdBikl8WJGONBZ5ErsE5h2Oju5HWDnZ50LZofbucqKR8qlj/gvM2
+pP8JtMX1f4XHv4sy+T9yUDCHs9YmJmw5hnGWowLZWgC0/j7rTMyJRnY3KrwRdj/wXTFmjnFucfZu
+/94DmfjeEDOFz0C0f3YgYWUsI+2YO9YVXGtiM3AJTNsy5j6K9jkAKLew5bRCRJqMYqloGVw2M0JH
+f4ZlSeeJaBsx6A24uIythC24JsTWGU7cNBP0NL3qbNPMIllkjj1n95If2W0cQobpYDaGF2ja1bjg
+5MAexBa5GWSJY2kGTsRGwkEd3Ad5qiG3zWSmXQGb7VwHzPvskUlDyLuenXPmlGEajIyyvcZ1Dns9
+S2Ru2G3YO5OHEHZNu4aZS8MuG5GPrZkBNbsTDMDQBg0rr/EM2GW5AKf9gZiRlINAzPQ5ltqgBSFC
+GNOIHYGDMjg5MNphi1sImR3WcGKBiIA8sM64mdAQ0sxEb84XSBFzplx8N2jz0O5guS/GeNfaqg7r
+yLrOzSoJKq2aJUadLQgFtLV6UcfzOw296pBr0/ms+rHmnTs5jnmC0eqLUKV72l4Ym3HYkknmcEsY
+QP51NUQZGktcjt2485yobNJeXv/S9pzH3nguOoYl36mAbjiMjYXDkIwI+7N0JMiHzrs7y3WvSOFZ
+</data>
+
+<datacheck>
+HTTP/1.1 200 OK
+Date: Mon, 29 Nov 2004 21:56:53 GMT
+Server: Apache/1.3.31 (Debian GNU/Linux) mod_gzip/1.3.26.1a PHP/4.3.9-1 mod_ssl/2.8.20 OpenSSL/0.9.7d mod_perl/1.29
+Vary: Accept-Encoding
+Content-Type: text/html; charset=ISO-8859-1
+Content-Encoding: zstd
+Content-Length: 1309
+
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!DOCTYPE project-listing SYSTEM "http://freshmeat.net/backend/fm-projects-0.4.dtd">
+<project-listing>
+  <project>
+    <project_id>1612</project_id>
+    <date_added>1998-08-21 04:01:29</date_added>
+    <date_updated>2004-10-18 02:22:23</date_updated>
+    <projectname_short>curl</projectname_short>
+    <projectname_full>curl and libcurl</projectname_full>
+    <desc_short>Command line tool and library for client-side URL transfers.</desc_short>
+    <desc_full>curl and libcurl is a tool for transferring files
+using URL syntax. It supports HTTP, HTTPS, FTP,
+FTPS, DICT, TELNET, LDAP, FILE, and GOPHER, as
+well as HTTP-post, HTTP-put, cookies, FTP upload,
+resumed transfers, passwords, portnumbers, SSL
+certificates, Kerberos, and proxies. It is powered
+by libcurl, the client-side URL transfer library.
+There are bindings to libcurl for over 20
+languages and environments.
+</desc_full>
+    <vitality_score>5784.57</vitality_score>
+    <vitality_percent>3.16</vitality_percent>
+    <vitality_rank>169</vitality_rank>
+    <popularity_score>6594.54</popularity_score>
+    <popularity_percent>13.81</popularity_percent>
+    <popularity_rank>105</popularity_rank>
+    <rating>8.50</rating>
+    <rating_count>21</rating_count>
+    <rating_rank>183</rating_rank>
+    <subscriptions>323</subscriptions>
+    <branch_name>Default</branch_name>
+    <url_project_page>http://freshmeat.net/projects/curl/</url_project_page>
+    <url_homepage>http://freshmeat.net/redir/curl/1612/url_homepage/</url_homepage>
+    <url_tgz>http://freshmeat.net/redir/curl/1612/url_tgz/</url_tgz>
+    <url_bz2>http://freshmeat.net/redir/curl/1612/url_bz2/</url_bz2>
+    <url_zip>http://freshmeat.net/redir/curl/1612/url_zip/</url_zip>
+    <url_changelog>http://freshmeat.net/redir/curl/1612/url_changelog/</url_changelog>
+    <url_rpm>http://freshmeat.net/redir/curl/1612/url_rpm/</url_rpm>
+    <url_deb>http://freshmeat.net/redir/curl/1612/url_deb/</url_deb>
+    <url_osx>http://freshmeat.net/redir/curl/1612/url_osx/</url_osx>
+    <url_bsdport>http://freshmeat.net/redir/curl/1612/url_bsdport/</url_bsdport>
+    <url_purchase></url_purchase>
+    <url_cvs>http://freshmeat.net/redir/curl/1612/url_cvs/</url_cvs>
+    <url_list>http://freshmeat.net/redir/curl/1612/url_list/</url_list>
+    <url_mirror>http://freshmeat.net/redir/curl/1612/url_mirror/</url_mirror>
+    <url_demo></url_demo>
+    <license>MIT/X Consortium License</license>
+    <latest_release>
+      <latest_release_version>7.12.2</latest_release_version>
+      <latest_release_id>176085</latest_release_id>
+      <latest_release_date>2004-10-18 02:22:23</latest_release_date>
+    </latest_release>
+    <screenshot_thumb></screenshot_thumb>
+    <authors>
+      <author>
+        <author_name>Daniel Stenberg</author_name>
+        <author_url>http://freshmeat.net/~bagder/</author_url>
+        <author_role>Owner</author_role>
+      </author>
+    </authors>
+    <descriminators>
+      <trove_id>12</trove_id>
+      <trove_id>226</trove_id>
+      <trove_id>3</trove_id>
+      <trove_id>2</trove_id>
+      <trove_id>188</trove_id>
+      <trove_id>216</trove_id>
+      <trove_id>200</trove_id>
+      <trove_id>220</trove_id>
+      <trove_id>164</trove_id>
+      <trove_id>90</trove_id>
+      <trove_id>89</trove_id>
+      <trove_id>809</trove_id>
+      <trove_id>150</trove_id>
+      <trove_id>224</trove_id>
+      <trove_id>900</trove_id>
+      <trove_id>839</trove_id>
+    </descriminators>
+    <dependencies>
+      <dependency type="recommended">
+        <dependency_release_id>0</dependency_release_id>
+        <dependency_branch_id>7464</dependency_branch_id>
+        <dependency_project_id>7464</dependency_project_id>
+        <dependency_project_title>OpenSSL (Default)</dependency_project_title>
+      </dependency>
+      <dependency type="optional">
+        <dependency_release_id>0</dependency_release_id>
+        <dependency_branch_id>0</dependency_branch_id>
+        <dependency_project_id>7443</dependency_project_id>
+        <dependency_project_title>OpenLDAP</dependency_project_title>
+      </dependency>
+      <dependency type="optional">
+        <dependency_release_id>0</dependency_release_id>
+        <dependency_branch_id>0</dependency_branch_id>
+        <dependency_project_id>12351</dependency_project_id>
+        <dependency_project_title>zlib</dependency_project_title>
+      </dependency>
+      <dependency type="optional">
+        <dependency_release_id>0</dependency_release_id>
+        <dependency_branch_id>0</dependency_branch_id>
+        <dependency_project_id>32047</dependency_project_id>
+        <dependency_project_title>Heimdal</dependency_project_title>
+      </dependency>
+      <dependency type="optional">
+        <dependency_release_id>0</dependency_release_id>
+        <dependency_branch_id>0</dependency_branch_id>
+        <dependency_project_id>44532</dependency_project_id>
+        <dependency_project_title>c-ares</dependency_project_title>
+      </dependency>
+    </dependencies>
+  </project>
+</project-listing>
+</datacheck>
+
+</reply>
+
+#
+# Client-side
+<client>
+<features>
+zstd
+</features>
+<server>
+http
+</server>
+ <name>
+HTTP GET zstd compressed content
+ </name>
+ <command>
+http://%HOSTIP:%HTTPPORT/396 --compressed
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<strip>
+^User-Agent:.*
+</strip>
+<strippart>
+s/^Accept-Encoding: .*/Accept-Encoding: xxx/
+</strippart>
+<protocol>
+GET /396 HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Accept: */*
+Accept-Encoding: xxx
+
+</protocol>
+</verify>
+</testcase>

tests/data/test397

@@ -0,0 +1,198 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+compressed
+</keywords>
+</info>
+#
+# Server-side
+<reply>
+# Length of not-encoded content is 16512 what is greater than default value of
+# CURL_MAX_WRITE_SIZE (16384)
+<data base64="yes">
+SFRUUC8xLjEgMjAwIE9LDQpEYXRlOiBNb24sIDI5IE5vdiAyMDA0IDIxOjU2OjUzIEdNVA0KU2Vy
+dmVyOiBBcGFjaGUvMS4zLjMxIChEZWJpYW4gR05VL0xpbnV4KSBtb2RfZ3ppcC8xLjMuMjYuMWEg
+UEhQLzQuMy45LTEgbW9kX3NzbC8yLjguMjAgT3BlblNTTC8wLjkuN2QgbW9kX3BlcmwvMS4yOQ0K
+VmFyeTogQWNjZXB0LUVuY29kaW5nDQpDb250ZW50LVR5cGU6IHRleHQvaHRtbDsgY2hhcnNldD1J
+U08tODg1OS0xDQpDb250ZW50LUVuY29kaW5nOiB6c3RkDQpDb250ZW50LUxlbmd0aDogNDcNCg0K
+KLUv/WSAPw0BAIgwMTIzNDU2Nzg5QUJDREVGCgQAfJ9geAAEGh3Sq006l4KvuZw=
+</data>
+
+<datacheck>
+HTTP/1.1 200 OK
+Date: Mon, 29 Nov 2004 21:56:53 GMT
+Server: Apache/1.3.31 (Debian GNU/Linux) mod_gzip/1.3.26.1a PHP/4.3.9-1 mod_ssl/2.8.20 OpenSSL/0.9.7d mod_perl/1.29
+Vary: Accept-Encoding
+Content-Type: text/html; charset=ISO-8859-1
+Content-Encoding: zstd
+Content-Length: 47
+
+0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF
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+</datacheck>
+
+</reply>
+
+#
+# Client-side
+<client>
+<features>
+zstd
+</features>
+<server>
+http
+</server>
+ <name>
+HTTP GET zstd compressed content of size more than CURL_MAX_WRITE_SIZE
+ </name>
+ <command>
+http://%HOSTIP:%HTTPPORT/397 --compressed
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<strip>
+^User-Agent:.*
+</strip>
+<strippart>
+s/^Accept-Encoding: .*/Accept-Encoding: xxx/
+</strippart>
+<protocol>
+GET /397 HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Accept: */*
+Accept-Encoding: xxx
+
+</protocol>
+</verify>
+</testcase>

tests/runtests.pl

@@ -240,6 +240,7 @@ my $has_ipv6;       # set if libcurl is built with IPv6 support
 my $has_unix;       # set if libcurl is built with Unix sockets support
 my $has_libz;       # set if libcurl is built with libz support
 my $has_brotli;     # set if libcurl is built with brotli support
+my $has_zstd;       # set if libcurl is built with zstd support
 my $has_getrlimit;  # set if system has getrlimit()
 my $has_ntlm;       # set if libcurl is built with NTLM support
 my $has_ntlm_wb;    # set if libcurl is built with NTLM delegation to winbind
@@ -2831,6 +2832,7 @@ sub setupfeatures {
     $feature{"unix-sockets"} = $has_unix;
     $feature{"win32"} = $has_win32;
     $feature{"WinSSL"} = $has_winssl;
+    $feature{"zstd"} = $has_zstd;
 
     # make each protocol an enabled "feature"
     for my $p (@protocols) {
@@ -3011,6 +3013,9 @@ sub checksystem {
             if($feat =~ /brotli/i) {
                 $has_brotli = 1;
             }
+            if($feat =~ /zstd/i) {
+                $has_zstd = 1;
+            }
             if($feat =~ /NTLM/i) {
                 # NTLM enabled
                 $has_ntlm=1;