[PATCH 3/4] perf: zstd: add streaming decompression and format probe functions

[Ivan Shapovalov <intelfx@intelfx.name>]

Add an actual streaming zstd decompression (fd->fd) entry point,
plus a file->fd wrapper and a helper to detect zstd magic on a file
for compressions[] in dso.c.

Signed-off-by: Ivan Shapovalov <intelfx@intelfx.name>
---
 tools/perf/util/compress.h |  18 ++++++++
 tools/perf/util/zstd.c     | 104 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 122 insertions(+)

diff --git a/tools/perf/util/compress.h b/tools/perf/util/compress.h
index e7aa89d31fc6f..fd6b541358bb6 100644
--- a/tools/perf/util/compress.h
+++ b/tools/perf/util/compress.h
@@ -59,6 +59,9 @@ ssize_t zstd_compress_stream_to_records(struct zstd_data *data, void *dst, size_
 
 size_t zstd_decompress_buffer(struct zstd_data *data, void *src, size_t src_size,
 			      void *dst, size_t dst_size);
+int zstd_decompress_stream(struct zstd_data *data, int input_fd, int output_fd);
+int zstd_decompress_to_fd(const char *input, int output_fd);
+bool zstd_is_compressed(const char *input);
 #else /* !HAVE_ZSTD_SUPPORT */
 
 static inline int zstd_init(struct zstd_data *data __maybe_unused, int level __maybe_unused)
@@ -88,6 +91,21 @@ static inline size_t zstd_decompress_buffer(struct zstd_data *data __maybe_unuse
 {
 	return 0;
 }
+
+static inline int zstd_decompress_stream(struct zstd_data *data, int input_fd, int output_fd)
+{
+	return -1;
+}
+
+static inline int zstd_decompress_to_fd(const char *input, int output_fd)
+{
+	return -1;
+}
+
+static inline bool zstd_is_compressed(const char *input)
+{
+	return false;
+}
 #endif
 
 #endif /* PERF_COMPRESS_H */
diff --git a/tools/perf/util/zstd.c b/tools/perf/util/zstd.c
index 3af8910bb87cf..982655a1f1a51 100644
--- a/tools/perf/util/zstd.c
+++ b/tools/perf/util/zstd.c
@@ -1,7 +1,11 @@
 // SPDX-License-Identifier: GPL-2.0
 
+#include <errno.h>
+#include <fcntl.h>
 #include <string.h>
+#include <unistd.h>
 #include <linux/perf_event.h>
+#include <internal/lib.h>
 
 #include "util/compress.h"
 #include "util/debug.h"
@@ -172,3 +176,103 @@ size_t zstd_decompress_buffer(struct zstd_data *data, void *src, size_t src_size
 
 	return output.pos;
 }
+
+int zstd_decompress_stream(struct zstd_data *data, int input_fd, int output_fd)
+{
+	ssize_t ret;
+	bool unflushed = false;
+	char buf_in[ZSTD_DStreamInSize()];
+	char buf_out[ZSTD_DStreamOutSize()];
+	ZSTD_inBuffer in = {};
+	ZSTD_outBuffer out = {};
+
+	ret = zstd_init_dstream(data);
+	if (ret < 0)
+		return ret;
+
+	for (;;) {
+		if (in.pos == in.size) {
+			/* out of input, read more */
+			ret = read(input_fd, buf_in, sizeof(buf_in));
+			if (ret < 0) {
+				pr_err("zstd: failed to read() %zu bytes: %s\n",
+				       sizeof(buf_in), strerror(errno));
+				return ret;
+			}
+			in = (ZSTD_inBuffer) {
+				.src = &buf_in,
+				.pos = 0,
+				.size = ret,
+			};
+		}
+
+		if (in.pos == in.size && !unflushed) {
+			/* out of input, out of file, and nothing to flush, exit */
+			break;
+		}
+
+		out = (ZSTD_outBuffer) {
+			.dst = &buf_out,
+			.pos = 0,
+			.size = sizeof(buf_out),
+		};
+		ret = ZSTD_decompressStream(data->dstream, &out, &in);
+		if (ZSTD_isError(ret)) {
+			pr_err("zstd: failed to decompress %zu bytes into buffer of %zu bytes (wrote %zu): %s\n",
+				in.size, out.size, out.pos, ZSTD_getErrorName(ret));
+			return -1;
+		}
+		unflushed = ret > 0;
+
+		ret = writen(output_fd, out.dst, out.pos);
+		if (ret < 0) {
+			pr_err("zstd: failed to write() %zu bytes: %s\n",
+			       out.pos, strerror(errno));
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+int zstd_decompress_to_fd(const char *input, int output_fd)
+{
+	int input_fd = -1;
+	int ret;
+	struct zstd_data data;
+
+	input_fd = open(input, O_RDONLY);
+	if (input_fd < 0) {
+		pr_err("zstd: failed to open(%s): %s\n", input, strerror(errno));
+		return -1;
+	}
+
+	ret = zstd_init(&data, ZSTD_CLEVEL_DEFAULT);
+	if (ret < 0)
+		goto err;
+
+	ret = zstd_decompress_stream(&data, input_fd, output_fd);
+
+err:
+	zstd_fini(&data);
+	close(input_fd);
+	return ret;
+}
+
+bool zstd_is_compressed(const char *file)
+{
+	int fd = open(file, O_RDONLY);
+	const uint32_t magic_le = htole32(ZSTD_MAGICNUMBER);
+	char buf[4];
+	ssize_t rc;
+
+	if (fd < 0) {
+		pr_err("zstd: failed to open(%s): %s\n", file, strerror(errno));
+		return -1;
+	}
+
+	rc = read(fd, buf, sizeof(buf));
+	close(fd);
+	return rc == sizeof(buf) ?
+	       memcmp(buf, (const char *) &magic_le, sizeof(buf)) == 0 : false;
+}

-- 
2.55.0.8.g37e2a0019f