Messages in this thread Patch in this message |  | | Date | Thu, 2 Apr 2020 08:43:56 -0700 | Subject | [PATCH v2 4/5] tools api: add a lightweight buffered reading api | From | Ian Rogers <> |
| |
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.
Signed-off-by: Ian Rogers <irogers@google.com> --- tools/lib/api/io.h | 107 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 107 insertions(+) create mode 100644 tools/lib/api/io.h
diff --git a/tools/lib/api/io.h b/tools/lib/api/io.h new file mode 100644 index 000000000000..5aa5b0e26a7a --- /dev/null +++ b/tools/lib/api/io.h @@ -0,0 +1,107 @@ +/* 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 (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. + * Returns -1 on error or if nothing is read, otherwise returns the character + * after the hexadecimal value. + */ +static inline int io__get_hex(struct io *io, __u64 *hex) +{ + bool first_read = true; + + *hex = 0; + while (true) { + char 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 -1; + else + return ch; + first_read = false; + } +} + +/* Read a decimal value into the out argument dec. + * Returns -1 on error or if nothing is read, otherwise returns the character + * after the decimal value. + */ +static inline int io__get_dec(struct io *io, __u64 *dec) +{ + bool first_read = true; + + *dec = 0; + while (true) { + char 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 -1; + else + return ch; + first_read = false; + } +} + +#endif /* __API_IO__ */ -- 2.26.0.rc2.310.g2932bb562d-goog
|  |