1 files changed, 152 insertions, 0 deletions
diff --git a/tools/perf/util/zstd.c b/tools/perf/util/zstd.c
new file mode 100644
index 000000000..d98014902
--- /dev/null
+++ b/tools/perf/util/zstd.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <string.h>
+#include <linux/perf_event.h>
+
+#include "util/compress.h"
+#include "util/debug.h"
+
+int zstd_init(struct zstd_data *data, int level)
+{
+	data->comp_level = level;
+	data->dstream = NULL;
+	data->cstream = NULL;
+	return 0;
+}
+
+int zstd_fini(struct zstd_data *data)
+{
+	if (data->dstream) {
+		ZSTD_freeDStream(data->dstream);
+		data->dstream = NULL;
+	}
+
+	if (data->cstream) {
+		ZSTD_freeCStream(data->cstream);
+		data->cstream = NULL;
+	}
+
+	return 0;
+}
+
+ssize_t zstd_compress_stream_to_records(struct zstd_data *data, void *dst, size_t dst_size,
+				       void *src, size_t src_size, size_t max_record_size,
+				       ssize_t process_header(void *record, size_t dst_size,
+							      size_t data_size))
+{
+	size_t ret, compressed = 0;
+	ssize_t size;
+	ZSTD_inBuffer input = { src, src_size, 0 };
+	ZSTD_outBuffer output;
+	void *record;
+
+	if (!data->cstream) {
+		data->cstream = ZSTD_createCStream();
+		if (data->cstream == NULL) {
+			pr_err("Couldn't create compression stream.\n");
+			return -1;
+		}
+
+		ret = ZSTD_initCStream(data->cstream, data->comp_level);
+		if (ZSTD_isError(ret)) {
+			pr_err("Failed to initialize compression stream: %s\n",
+				ZSTD_getErrorName(ret));
+			return -1;
+		}
+	}
+
+	while (input.pos < input.size) {
+		record = dst;
+		size = process_header(record, dst_size, 0);
+		/* Output buffer full — cannot fit even the record header */
+		if (size < 0)
+			goto reset;
+		compressed += size;
+		dst += size;
+		dst_size -= size;
+		output = (ZSTD_outBuffer){ dst, (dst_size > max_record_size) ?
+						max_record_size : dst_size, 0 };
+		ret = ZSTD_compressStream(data->cstream, &output, &input);
+		ZSTD_flushStream(data->cstream, &output);
+		if (ZSTD_isError(ret)) {
+			pr_err("failed to compress %ld bytes: %s\n",
+				(long)src_size, ZSTD_getErrorName(ret));
+			goto reset;
+		}
+		compressed += output.pos;
+		dst += output.pos;
+		dst_size -= output.pos;
+		/*
+		 * No progress: ZSTD couldn't emit any bytes into the
+		 * remaining output buffer.  Calling process_header
+		 * with output.pos=0 would re-trigger header initialization,
+		 * double-subtracting the header size from dst_size and
+		 * underflowing the unsigned counter.
+		 */
+		if (output.pos == 0)
+			goto reset;
+		size = process_header(record, dst_size, output.pos);
+		if (size < 0)
+			goto reset;
+		compressed += size;
+		dst += size;
+		dst_size -= size;
+	}
+
+	return compressed;
+
+reset:
+	/* Reset so the context is usable if the caller retries */
+	ret = ZSTD_initCStream(data->cstream, data->comp_level);
+	if (ZSTD_isError(ret))
+		pr_err("failed to reset compression context: %s\n",
+			ZSTD_getErrorName(ret));
+	return -1;
+}
+
+size_t zstd_decompress_stream(struct zstd_data *data, void *src, size_t src_size,
+			      void *dst, size_t dst_size)
+{
+	size_t ret;
+	ZSTD_inBuffer input = { src, src_size, 0 };
+	ZSTD_outBuffer output = { dst, dst_size, 0 };
+
+	if (!data->dstream) {
+		data->dstream = ZSTD_createDStream();
+		if (data->dstream == NULL) {
+			pr_err("Couldn't create decompression stream.\n");
+			return 0;
+		}
+
+		ret = ZSTD_initDStream(data->dstream);
+		if (ZSTD_isError(ret)) {
+			pr_err("Failed to initialize decompression stream: %s\n",
+				ZSTD_getErrorName(ret));
+			return 0;
+		}
+	}
+	while (input.pos < input.size) {
+		size_t prev_in = input.pos;
+		size_t prev_out = output.pos;
+
+		ret = ZSTD_decompressStream(data->dstream, &output, &input);
+		if (ZSTD_isError(ret)) {
+			pr_err("failed to decompress (B): %zd -> %zd, dst_size %zd : %s\n",
+			       src_size, output.pos, dst_size, ZSTD_getErrorName(ret));
+			return 0;
+		}
+		/*
+		 * Neither stream advanced — decompression is stuck.
+		 * Return 0 (error) rather than partial output: perf
+		 * uses ZSTD_flushStream (not ZSTD_endStream), so the
+		 * stream is continuous across compressed events.
+		 * Discarding unconsumed input would desynchronize the
+		 * decompressor, causing the next call to produce
+		 * garbage that could be misinterpreted as valid events.
+		 */
+		if (input.pos == prev_in && output.pos == prev_out)
+			return 0;
+	}
+
+	return output.pos;
+}