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authorIan Rogers <irogers@google.com>2020-04-14 22:40:49 -0700
committerArnaldo Carvalho de Melo <acme@redhat.com>2020-04-30 10:48:28 -0300
commite95770af4c4a280fab2080529d30452a7628d45d (patch)
tree6abebd1ff578789b6d7e2d37fbfee32b42ae2fd4 /tools/lib/api
parent13edc237200c75425ab0e3fe4b4c75dafb468c2e (diff)
tools api: Add a lightweight buffered reading api
The synthesize benchmark shows the majority of execution time going to fgets and sscanf, necessary to parse /proc/pid/maps. Add a new buffered reading library that will be used to replace these calls in a follow-up CL. Add tests for the library to perf test. Committer tests: $ perf test api 63: Test api io : Ok $ Signed-off-by: Ian Rogers <irogers@google.com> Acked-by: Jiri Olsa <jolsa@redhat.com> Acked-by: Namhyung Kim <namhyung@kernel.org> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andrey Zhizhikin <andrey.z@gmail.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Kan Liang <kan.liang@linux.intel.com> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Petr Mladek <pmladek@suse.com> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lore.kernel.org/lkml/20200415054050.31645-3-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/lib/api')
-rw-r--r--tools/lib/api/io.h112
1 files changed, 112 insertions, 0 deletions
diff --git a/tools/lib/api/io.h b/tools/lib/api/io.h
new file mode 100644
index 000000000000..b7e55b5f8a4a
--- /dev/null
+++ b/tools/lib/api/io.h
@@ -0,0 +1,112 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Lightweight buffered reading library.
+ *
+ * Copyright 2019 Google LLC.
+ */
+#ifndef __API_IO__
+#define __API_IO__
+
+struct io {
+ /* File descriptor being read/ */
+ int fd;
+ /* Size of the read buffer. */
+ unsigned int buf_len;
+ /* Pointer to storage for buffering read. */
+ char *buf;
+ /* End of the storage. */
+ char *end;
+ /* Currently accessed data pointer. */
+ char *data;
+ /* Set true on when the end of file on read error. */
+ bool eof;
+};
+
+static inline void io__init(struct io *io, int fd,
+ char *buf, unsigned int buf_len)
+{
+ io->fd = fd;
+ io->buf_len = buf_len;
+ io->buf = buf;
+ io->end = buf;
+ io->data = buf;
+ io->eof = false;
+}
+
+/* Reads one character from the "io" file with similar semantics to fgetc. */
+static inline int io__get_char(struct io *io)
+{
+ char *ptr = io->data;
+
+ if (io->eof)
+ return -1;
+
+ if (ptr == io->end) {
+ ssize_t n = read(io->fd, io->buf, io->buf_len);
+
+ if (n <= 0) {
+ io->eof = true;
+ return -1;
+ }
+ ptr = &io->buf[0];
+ io->end = &io->buf[n];
+ }
+ io->data = ptr + 1;
+ return *ptr;
+}
+
+/* Read a hexadecimal value with no 0x prefix into the out argument hex. If the
+ * first character isn't hexadecimal returns -2, io->eof returns -1, otherwise
+ * returns the character after the hexadecimal value which may be -1 for eof.
+ * If the read value is larger than a u64 the high-order bits will be dropped.
+ */
+static inline int io__get_hex(struct io *io, __u64 *hex)
+{
+ bool first_read = true;
+
+ *hex = 0;
+ while (true) {
+ int ch = io__get_char(io);
+
+ if (ch < 0)
+ return ch;
+ if (ch >= '0' && ch <= '9')
+ *hex = (*hex << 4) | (ch - '0');
+ else if (ch >= 'a' && ch <= 'f')
+ *hex = (*hex << 4) | (ch - 'a' + 10);
+ else if (ch >= 'A' && ch <= 'F')
+ *hex = (*hex << 4) | (ch - 'A' + 10);
+ else if (first_read)
+ return -2;
+ else
+ return ch;
+ first_read = false;
+ }
+}
+
+/* Read a positive decimal value with out argument dec. If the first character
+ * isn't a decimal returns -2, io->eof returns -1, otherwise returns the
+ * character after the decimal value which may be -1 for eof. If the read value
+ * is larger than a u64 the high-order bits will be dropped.
+ */
+static inline int io__get_dec(struct io *io, __u64 *dec)
+{
+ bool first_read = true;
+
+ *dec = 0;
+ while (true) {
+ int ch = io__get_char(io);
+
+ if (ch < 0)
+ return ch;
+ if (ch >= '0' && ch <= '9')
+ *dec = (*dec * 10) + ch - '0';
+ else if (first_read)
+ return -2;
+ else
+ return ch;
+ first_read = false;
+ }
+}
+
+#endif /* __API_IO__ */