Split stream compression out of libio

Move it to a separate libxfrm library, where it can be independently
tested as well. The bulk of the new code is also mainly test cases
for the compressors.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

6 files changed, 755 insertions, 0 deletions

diff --git a/lib/xfrm/Makemodule.am b/lib/xfrm/Makemodule.am
new file mode 100644
index 0000000..a344820
--- /dev/null
+++ b/lib/xfrm/Makemodule.am
@@ -0,0 +1,27 @@
+libxfrm_a_SOURCES = include/xfrm/stream.h include/xfrm/compress.h
+libxfrm_a_SOURCES += lib/xfrm/compress.c
+libxfrm_a_CFLAGS = $(AM_CFLAGS)
+
+if WITH_XZ
+libxfrm_a_SOURCES += lib/xfrm/xz.c
+libxfrm_a_CFLAGS += $(XZ_CFLAGS) -DWITH_XZ
+endif
+
+if WITH_BZIP2
+libxfrm_a_SOURCES += lib/xfrm/bzip2.c
+libxfrm_a_CFLAGS += $(BZIP2_CFLAGS) -DWITH_BZIP2
+endif
+
+if WITH_GZIP
+libxfrm_a_SOURCES += lib/xfrm/gzip.c
+libxfrm_a_CFLAGS += $(ZLIB_CFLAGS) -DWITH_GZIP
+endif
+
+if WITH_ZSTD
+if HAVE_ZSTD_STREAM
+libxfrm_a_SOURCES += lib/xfrm/zstd.c
+libxfrm_a_CFLAGS += $(ZSTD_CFLAGS) -DWITH_ZSTD
+endif
+endif
+
+noinst_LIBRARIES += libxfrm.a
diff --git a/lib/xfrm/bzip2.c b/lib/xfrm/bzip2.c
new file mode 100644
index 0000000..7e5807d
--- /dev/null
+++ b/lib/xfrm/bzip2.c
@@ -0,0 +1,151 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * bzip2.c
+ *
+ * Copyright (C) 2021 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <bzlib.h>
+
+#include "xfrm/stream.h"
+#include "xfrm/compress.h"
+
+typedef struct {
+	xfrm_stream_t base;
+
+	bz_stream strm;
+	bool compress;
+	bool initialized;
+
+	int level;
+	int work_factor;
+} xfrm_stream_bzip2_t;
+
+static const int bzlib_action[] = {
+	[XFRM_STREAM_FLUSH_NONE] = BZ_RUN,
+	[XFRM_STREAM_FLUSH_SYNC] = BZ_FLUSH,
+	[XFRM_STREAM_FLUSH_FULL] = BZ_FINISH,
+};
+
+static int process_data(xfrm_stream_t *stream, const void *in, sqfs_u32 in_size,
+			void *out, sqfs_u32 out_size,
+			sqfs_u32 *in_read, sqfs_u32 *out_written,
+			int flush_mode)
+{
+	xfrm_stream_bzip2_t *bzip2 = (xfrm_stream_bzip2_t *)stream;
+	sqfs_u32 diff;
+	int ret;
+
+	if (!bzip2->initialized) {
+		if (bzip2->compress) {
+			ret = BZ2_bzCompressInit(&bzip2->strm, bzip2->level, 0,
+						 bzip2->work_factor);
+		} else {
+			ret = BZ2_bzDecompressInit(&bzip2->strm, 0, 0);
+		}
+
+		if (ret != BZ_OK)
+			return XFRM_STREAM_ERROR;
+
+		bzip2->initialized = true;
+	}
+
+	if (flush_mode < 0 || flush_mode >= XFRM_STREAM_FLUSH_COUNT)
+		flush_mode = XFRM_STREAM_FLUSH_NONE;
+
+	while (in_size > 0 && out_size > 0) {
+		bzip2->strm.next_in = (char *)in;
+		bzip2->strm.avail_in = in_size;
+
+		bzip2->strm.next_out = (char *)out;
+		bzip2->strm.avail_out = out_size;
+
+		if (bzip2->compress) {
+			ret = BZ2_bzCompress(&bzip2->strm,
+					     bzlib_action[flush_mode]);
+		} else {
+			ret = BZ2_bzDecompress(&bzip2->strm);
+		}
+
+		if (ret == BZ_OUTBUFF_FULL)
+			return XFRM_STREAM_BUFFER_FULL;
+
+		if (ret < 0)
+			return XFRM_STREAM_ERROR;
+
+		diff = (in_size - bzip2->strm.avail_in);
+		in = (const char *)in + diff;
+		in_size -= diff;
+		*in_read += diff;
+
+		diff = (out_size - bzip2->strm.avail_out);
+		out = (char *)out + diff;
+		out_size -= diff;
+		*out_written += diff;
+
+		if (ret == BZ_STREAM_END) {
+			if (bzip2->compress) {
+				BZ2_bzCompressEnd(&bzip2->strm);
+			} else {
+				BZ2_bzDecompressEnd(&bzip2->strm);
+			}
+
+			bzip2->initialized = false;
+			return XFRM_STREAM_END;
+		}
+	}
+
+	return XFRM_STREAM_OK;
+}
+
+static void destroy(sqfs_object_t *obj)
+{
+	xfrm_stream_bzip2_t *bzip2 = (xfrm_stream_bzip2_t *)obj;
+
+	if (bzip2->initialized) {
+		if (bzip2->compress) {
+			BZ2_bzCompressEnd(&bzip2->strm);
+		} else {
+			BZ2_bzDecompressEnd(&bzip2->strm);
+		}
+	}
+
+	free(bzip2);
+}
+
+static xfrm_stream_t *stream_create(const compressor_config_t *cfg,
+				    bool compress)
+{
+	xfrm_stream_bzip2_t *bzip2 = calloc(1, sizeof(*bzip2));
+	xfrm_stream_t *xfrm = (xfrm_stream_t *)bzip2;
+
+	if (bzip2 == NULL) {
+		perror("creating bzip2 stream compressor");
+		return NULL;
+	}
+
+	if (cfg == NULL) {
+		bzip2->level = COMP_BZIP2_DEFAULT_LEVEL;
+		bzip2->work_factor = COMP_BZIP2_DEFAULT_WORK_FACTOR;
+	} else {
+		bzip2->level = cfg->level;
+		bzip2->work_factor = cfg->opt.bzip2.work_factor;
+	}
+
+	bzip2->initialized = false;
+	bzip2->compress = compress;
+	xfrm->process_data = process_data;
+	sqfs_object_init(bzip2, destroy, NULL);
+	return xfrm;
+}
+
+xfrm_stream_t *compressor_stream_bzip2_create(const compressor_config_t *cfg)
+{
+	return stream_create(cfg, true);
+}
+
+xfrm_stream_t *decompressor_stream_bzip2_create(void)
+{
+	return stream_create(NULL, false);
+}
diff --git a/lib/xfrm/compress.c b/lib/xfrm/compress.c
new file mode 100644
index 0000000..fbd6987
--- /dev/null
+++ b/lib/xfrm/compress.c
@@ -0,0 +1,102 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * compress.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "xfrm/compress.h"
+#include "config.h"
+
+#include <string.h>
+
+static const struct {
+	int id;
+	const char *name;
+	const sqfs_u8 *magic;
+	size_t count;
+	xfrm_stream_t *(*mk_comp_stream)(const compressor_config_t *);
+	xfrm_stream_t *(*mk_decomp_stream)(void);
+} compressors[] = {
+#ifdef WITH_GZIP
+	{ XFRM_COMPRESSOR_GZIP, "gzip", (const sqfs_u8 *)"\x1F\x8B\x08", 3,
+	  compressor_stream_gzip_create, decompressor_stream_gzip_create },
+#endif
+#ifdef WITH_XZ
+	{ XFRM_COMPRESSOR_XZ, "xz", (const sqfs_u8 *)("\xFD" "7zXZ"), 6,
+	  compressor_stream_xz_create, decompressor_stream_xz_create },
+#endif
+#if defined(WITH_ZSTD) && defined(HAVE_ZSTD_STREAM)
+	{ XFRM_COMPRESSOR_ZSTD, "zstd",
+	  (const sqfs_u8 *)"\x28\xB5\x2F\xFD", 4,
+	  compressor_stream_zstd_create, decompressor_stream_zstd_create },
+#endif
+#ifdef WITH_BZIP2
+	{ XFRM_COMPRESSOR_BZIP2, "bzip2", (const sqfs_u8 *)"BZh", 3,
+	  compressor_stream_bzip2_create, decompressor_stream_bzip2_create },
+#endif
+};
+
+int xfrm_compressor_id_from_name(const char *name)
+{
+	size_t i;
+
+	for (i = 0; i < sizeof(compressors) / sizeof(compressors[0]); ++i) {
+		if (strcmp(name, compressors[i].name) == 0)
+			return compressors[i].id;
+	}
+
+	return -1;
+}
+
+int xfrm_compressor_id_from_magic(const void *data, size_t count)
+{
+	size_t i;
+	int ret;
+
+	for (i = 0; i < sizeof(compressors) / sizeof(compressors[0]); ++i) {
+		if (compressors[i].count > count)
+			continue;
+
+		ret = memcmp(compressors[i].magic, data, compressors[i].count);
+		if (ret == 0)
+			return compressors[i].id;
+	}
+
+	return -1;
+}
+
+const char *xfrm_compressor_name_from_id(int id)
+{
+	size_t i;
+
+	for (i = 0; i < sizeof(compressors) / sizeof(compressors[0]); ++i) {
+		if (compressors[i].id == id)
+			return compressors[i].name;
+	}
+
+	return NULL;
+}
+
+xfrm_stream_t *compressor_stream_create(int id, const compressor_config_t *cfg)
+{
+	size_t i;
+
+	for (i = 0; i < sizeof(compressors) / sizeof(compressors[0]); ++i) {
+		if (compressors[i].id == id)
+			return compressors[i].mk_comp_stream(cfg);
+	}
+
+	return NULL;
+}
+
+xfrm_stream_t *decompressor_stream_create(int id)
+{
+	size_t i;
+
+	for (i = 0; i < sizeof(compressors) / sizeof(compressors[0]); ++i) {
+		if (compressors[i].id == id)
+			return compressors[i].mk_decomp_stream();
+	}
+
+	return NULL;
+}
diff --git a/lib/xfrm/gzip.c b/lib/xfrm/gzip.c
new file mode 100644
index 0000000..67224f7
--- /dev/null
+++ b/lib/xfrm/gzip.c
@@ -0,0 +1,144 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * gzip.c
+ *
+ * Copyright (C) 2021 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <zlib.h>
+
+#include "xfrm/stream.h"
+#include "xfrm/compress.h"
+
+typedef struct {
+	xfrm_stream_t base;
+
+	z_stream strm;
+	bool compress;
+} xfrm_stream_gzip_t;
+
+static const int zlib_action[] = {
+	[XFRM_STREAM_FLUSH_NONE] = Z_NO_FLUSH,
+	[XFRM_STREAM_FLUSH_SYNC] = Z_SYNC_FLUSH,
+	[XFRM_STREAM_FLUSH_FULL] = Z_FINISH,
+};
+
+static int process_data(xfrm_stream_t *stream, const void *in,
+			sqfs_u32 in_size, void *out, sqfs_u32 out_size,
+			sqfs_u32 *in_read, sqfs_u32 *out_written,
+			int flush_mode)
+{
+	xfrm_stream_gzip_t *gzip = (xfrm_stream_gzip_t *)stream;
+	sqfs_u32 diff;
+	int ret;
+
+	if (flush_mode < 0 || flush_mode >= XFRM_STREAM_FLUSH_COUNT)
+		flush_mode = XFRM_STREAM_FLUSH_NONE;
+
+	while (in_size > 0 && out_size > 0) {
+		gzip->strm.next_in = (void *)in;
+		gzip->strm.avail_in = in_size;
+
+		gzip->strm.next_out = out;
+		gzip->strm.avail_out = out_size;
+
+		if (gzip->compress) {
+			ret = deflate(&gzip->strm, zlib_action[flush_mode]);
+		} else {
+			ret = inflate(&gzip->strm, zlib_action[flush_mode]);
+		}
+
+		if (ret == Z_STREAM_ERROR)
+			return XFRM_STREAM_ERROR;
+
+		diff = in_size - gzip->strm.avail_in;
+		in = (const char *)in + diff;
+		in_size -= diff;
+		*in_read += diff;
+
+		diff = out_size - gzip->strm.avail_out;
+		out = (char *)out + diff;
+		out_size -= diff;
+		*out_written += diff;
+
+		if (ret == Z_STREAM_END) {
+			if (gzip->compress) {
+				ret = deflateReset(&gzip->strm);
+			} else {
+				ret = inflateReset(&gzip->strm);
+			}
+
+			if (ret != Z_OK)
+				return XFRM_STREAM_ERROR;
+
+			return XFRM_STREAM_END;
+		}
+
+		if (ret == Z_BUF_ERROR)
+			return XFRM_STREAM_BUFFER_FULL;
+	}
+
+	return XFRM_STREAM_OK;
+}
+
+static void destroy(sqfs_object_t *obj)
+{
+	xfrm_stream_gzip_t *gzip = (xfrm_stream_gzip_t *)obj;
+
+	if (gzip->compress) {
+		deflateEnd(&gzip->strm);
+	} else {
+		inflateEnd(&gzip->strm);
+	}
+	free(gzip);
+}
+
+static xfrm_stream_t *create_stream(const compressor_config_t *cfg,
+				    bool compress)
+{
+	xfrm_stream_gzip_t *gzip = calloc(1, sizeof(*gzip));
+	xfrm_stream_t *xfrm = (xfrm_stream_t *)gzip;
+	int ret;
+
+	if (gzip == NULL) {
+		perror("creating gzip stream compressor");
+		return NULL;
+	}
+
+	if (compress) {
+		int level = COMP_GZIP_DEFAULT_LEVEL;
+		int wnd = COMP_GZIP_DEFAULT_WINDOW;
+
+		if (cfg != NULL) {
+			level = cfg->level;
+			wnd = cfg->opt.gzip.window_size;
+		}
+
+		ret = deflateInit2(&gzip->strm, level, Z_DEFLATED,
+				   wnd + 16, 8, Z_DEFAULT_STRATEGY);
+	} else {
+		ret = inflateInit2(&gzip->strm, 16 + 15);
+	}
+
+	if (ret != Z_OK) {
+		fputs("internal error creating gzip compressor.\n", stderr);
+		free(gzip);
+		return NULL;
+	}
+
+	gzip->compress = compress;
+	xfrm->process_data = process_data;
+	sqfs_object_init(xfrm, destroy, NULL);
+	return xfrm;
+}
+
+xfrm_stream_t *compressor_stream_gzip_create(const compressor_config_t *cfg)
+{
+	return create_stream(cfg, true);
+}
+
+xfrm_stream_t *decompressor_stream_gzip_create(void)
+{
+	return create_stream(NULL, false);
+}
diff --git a/lib/xfrm/xz.c b/lib/xfrm/xz.c
new file mode 100644
index 0000000..5adb6f3
--- /dev/null
+++ b/lib/xfrm/xz.c
@@ -0,0 +1,195 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * xz.c
+ *
+ * Copyright (C) 2021 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <lzma.h>
+
+#include "xfrm/stream.h"
+#include "xfrm/compress.h"
+
+typedef struct {
+	xfrm_stream_t base;
+
+	lzma_stream strm;
+
+	sqfs_u64 memlimit;
+	lzma_filter filters[3];
+	lzma_options_lzma opt;
+	lzma_vli vli_filter;
+	sqfs_u32 presets;
+
+	bool compress;
+	bool initialized;
+} xfrm_xz_t;
+
+static const lzma_action xzlib_action[] = {
+	[XFRM_STREAM_FLUSH_NONE] = LZMA_RUN,
+	[XFRM_STREAM_FLUSH_SYNC] = LZMA_FULL_FLUSH,
+	[XFRM_STREAM_FLUSH_FULL] = LZMA_FINISH,
+};
+
+static lzma_vli vli_filter_from_flags(int vli)
+{
+	switch (vli) {
+	case COMP_XZ_VLI_X86:
+		return LZMA_FILTER_X86;
+	case COMP_XZ_VLI_POWERPC:
+		return LZMA_FILTER_POWERPC;
+	case COMP_XZ_VLI_IA64:
+		return LZMA_FILTER_IA64;
+	case COMP_XZ_VLI_ARM:
+		return LZMA_FILTER_ARM;
+	case COMP_XZ_VLI_ARMTHUMB:
+		return LZMA_FILTER_ARMTHUMB;
+	case COMP_XZ_VLI_SPARC:
+		return LZMA_FILTER_SPARC;
+	default:
+		return LZMA_VLI_UNKNOWN;
+	}
+}
+
+static int process_data(xfrm_stream_t *stream, const void *in,
+			sqfs_u32 in_size, void *out, sqfs_u32 out_size,
+			sqfs_u32 *in_read, sqfs_u32 *out_written,
+			int flush_mode)
+{
+	xfrm_xz_t *xz = (xfrm_xz_t *)stream;
+	lzma_ret ret_xz;
+	sqfs_u32 diff;
+
+	if (!xz->initialized) {
+		if (xz->compress) {
+			ret_xz = lzma_stream_encoder(&xz->strm, xz->filters,
+						     LZMA_CHECK_CRC32);
+		} else {
+			ret_xz = lzma_stream_decoder(&xz->strm,
+						     xz->memlimit, 0);
+		}
+
+		if (ret_xz != LZMA_OK)
+			return XFRM_STREAM_ERROR;
+
+		xz->initialized = true;
+	}
+
+	if (flush_mode < 0 || flush_mode >= XFRM_STREAM_FLUSH_COUNT)
+		flush_mode = XFRM_STREAM_FLUSH_NONE;
+
+	while (in_size > 0 && out_size > 0) {
+		xz->strm.next_in = in;
+		xz->strm.avail_in = in_size;
+
+		xz->strm.next_out = out;
+		xz->strm.avail_out = out_size;
+
+		ret_xz = lzma_code(&xz->strm, xzlib_action[flush_mode]);
+
+		if (ret_xz != LZMA_OK && ret_xz != LZMA_BUF_ERROR &&
+		    ret_xz != LZMA_STREAM_END) {
+			return XFRM_STREAM_ERROR;
+		}
+
+		diff = in_size - xz->strm.avail_in;
+		in = (const char *)in + diff;
+		in_size -= diff;
+		*in_read += diff;
+
+		diff = out_size - xz->strm.avail_out;
+		out = (char *)out + diff;
+		out_size -= diff;
+		*out_written += diff;
+
+		if (ret_xz == LZMA_BUF_ERROR)
+			return XFRM_STREAM_BUFFER_FULL;
+
+		if (ret_xz == LZMA_STREAM_END) {
+			lzma_end(&xz->strm);
+			xz->initialized = false;
+			return XFRM_STREAM_END;
+		}
+	}
+
+	return XFRM_STREAM_OK;
+}
+
+static void destroy(sqfs_object_t *obj)
+{
+	xfrm_xz_t *xz = (xfrm_xz_t *)obj;
+
+	if (xz->initialized)
+		lzma_end(&xz->strm);
+
+	free(xz);
+}
+
+static xfrm_stream_t *create_stream(const compressor_config_t *cfg,
+				    bool compress)
+{
+	xfrm_xz_t *xz = calloc(1, sizeof(*xz));
+	xfrm_stream_t *xfrm = (xfrm_stream_t *)xz;
+	int i = 0;
+
+	if (xz == NULL) {
+		perror("creating xz stream compressor");
+		return NULL;
+	}
+
+	xz->memlimit = 128 * 1024 * 1024;
+	xz->compress = compress;
+	xz->initialized = false;
+
+	if (compress) {
+		if (cfg == NULL) {
+			xz->presets = COMP_XZ_DEFAULT_LEVEL;
+		} else {
+			xz->presets = cfg->level;
+			if (cfg->flags & COMP_FLAG_XZ_EXTREME)
+				xz->presets |= LZMA_PRESET_EXTREME;
+		}
+
+		if (lzma_lzma_preset(&xz->opt, xz->presets))
+			goto fail_init;
+
+		if (cfg == NULL) {
+			xz->vli_filter = LZMA_VLI_UNKNOWN;
+		} else {
+			xz->vli_filter = vli_filter_from_flags(cfg->opt.xz.vli);
+		}
+
+		if (xz->vli_filter != LZMA_VLI_UNKNOWN) {
+			xz->filters[i].id = xz->vli_filter;
+			xz->filters[i].options = NULL;
+			++i;
+		}
+
+		xz->filters[i].id = LZMA_FILTER_LZMA2;
+		xz->filters[i].options = &xz->opt;
+		++i;
+
+		xz->filters[i].id = LZMA_VLI_UNKNOWN;
+		xz->filters[i].options = NULL;
+		++i;
+	}
+
+	xfrm->process_data = process_data;
+	sqfs_object_init(xz, destroy, NULL);
+	return xfrm;
+fail_init:
+	fputs("error initializing XZ compressor\n", stderr);
+	free(xz);
+	return NULL;
+}
+
+xfrm_stream_t *compressor_stream_xz_create(const compressor_config_t *cfg)
+{
+	return create_stream(cfg, true);
+}
+
+xfrm_stream_t *decompressor_stream_xz_create(void)
+{
+	return create_stream(NULL, false);
+}
diff --git a/lib/xfrm/zstd.c b/lib/xfrm/zstd.c
new file mode 100644
index 0000000..70666c1
--- /dev/null
+++ b/lib/xfrm/zstd.c
@@ -0,0 +1,136 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * zstd.c
+ *
+ * Copyright (C) 2021 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <zstd.h>
+
+#include "xfrm/stream.h"
+#include "xfrm/compress.h"
+
+typedef struct {
+	xfrm_stream_t base;
+
+	ZSTD_CStream *cstrm;
+	ZSTD_DStream *dstrm;
+	bool compress;
+} xfrm_zstd_t;
+
+static const ZSTD_EndDirective zstd_action[] = {
+	[XFRM_STREAM_FLUSH_NONE] = ZSTD_e_continue,
+	[XFRM_STREAM_FLUSH_SYNC] = ZSTD_e_flush,
+	[XFRM_STREAM_FLUSH_FULL] = ZSTD_e_end,
+};
+
+static int process_data(xfrm_stream_t *stream, const void *in,
+			sqfs_u32 in_size, void *out, sqfs_u32 out_size,
+			sqfs_u32 *in_read, sqfs_u32 *out_written,
+			int flush_mode)
+{
+	xfrm_zstd_t *zstd = (xfrm_zstd_t *)stream;
+	ZSTD_outBuffer out_desc;
+	ZSTD_inBuffer in_desc;
+	size_t ret;
+
+	if (flush_mode < 0 || flush_mode >= XFRM_STREAM_FLUSH_COUNT)
+		flush_mode = XFRM_STREAM_FLUSH_NONE;
+
+	while (in_size > 0 && out_size > 0) {
+		memset(&in_desc, 0, sizeof(in_desc));
+		in_desc.src = in;
+		in_desc.size = in_size;
+
+		memset(&out_desc, 0, sizeof(out_desc));
+		out_desc.dst = out;
+		out_desc.size = out_size;
+
+		if (zstd->compress) {
+			ret = ZSTD_compressStream2(zstd->cstrm, &out_desc,
+						   &in_desc,
+						   zstd_action[flush_mode]);
+		} else {
+			ret = ZSTD_decompressStream(zstd->dstrm, &out_desc,
+						    &in_desc);
+		}
+
+		if (ZSTD_isError(ret))
+			return XFRM_STREAM_ERROR;
+
+		in = (const char *)in + in_desc.pos;
+		in_size -= in_desc.pos;
+		*in_read += in_desc.pos;
+
+		out = (char *)out + out_desc.pos;
+		out_size -= out_desc.pos;
+		*out_written += out_desc.pos;
+	}
+
+	if (flush_mode != XFRM_STREAM_FLUSH_NONE) {
+		if (in_size == 0)
+			return XFRM_STREAM_END;
+	}
+
+	if (in_size > 0 && out_size == 0)
+		return XFRM_STREAM_BUFFER_FULL;
+
+	return XFRM_STREAM_OK;
+}
+
+static void destroy(sqfs_object_t *obj)
+{
+	xfrm_zstd_t *zstd = (xfrm_zstd_t *)obj;
+
+	if (zstd->compress) {
+		ZSTD_freeCStream(zstd->cstrm);
+	} else {
+		ZSTD_freeDStream(zstd->dstrm);
+	}
+
+	free(zstd);
+}
+
+static xfrm_stream_t *stream_create(const compressor_config_t *cfg,
+				    bool compress)
+{
+	xfrm_zstd_t *zstd = calloc(1, sizeof(*zstd));
+	xfrm_stream_t *strm = (xfrm_stream_t *)zstd;
+	(void)cfg;
+
+	if (zstd == NULL) {
+		perror("creating zstd stream compressor");
+		return NULL;
+	}
+
+	if (compress) {
+		zstd->cstrm = ZSTD_createCStream();
+		if (zstd->cstrm == NULL)
+			goto fail_strm;
+	} else {
+		zstd->dstrm = ZSTD_createDStream();
+		if (zstd->dstrm == NULL)
+			goto fail_strm;
+	}
+
+	zstd->compress = compress;
+	strm->process_data = process_data;
+	sqfs_object_init(zstd, destroy, NULL);
+	return strm;
+fail_strm:
+	fputs("error initializing zstd stream.\n", stderr);
+	free(zstd);
+	return NULL;
+}
+
+xfrm_stream_t *compressor_stream_zstd_create(const compressor_config_t *cfg)
+{
+	return stream_create(cfg, true);
+}
+
+xfrm_stream_t *decompressor_stream_zstd_create(void)
+{
+	return stream_create(NULL, false);
+}