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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Lightweight buffered reading library.
*
* Copyright 2019 Google LLC.
*/
#ifndef __API_IO__
#define __API_IO__
#include <errno.h>
#include <poll.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <linux/types.h>
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;
/* Read timeout, 0 implies no timeout. */
int timeout_ms;
/* 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->timeout_ms = 0;
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;
if (io->timeout_ms != 0) {
struct pollfd pfds[] = {
{
.fd = io->fd,
.events = POLLIN,
},
};
n = poll(pfds, 1, io->timeout_ms);
if (n == 0)
errno = ETIMEDOUT;
if (n > 0 && !(pfds[0].revents & POLLIN)) {
errno = EIO;
n = -1;
}
if (n <= 0) {
io->eof = true;
return -1;
}
}
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;
}
}
/* Read up to and including the first newline following the pattern of getline. */
static inline ssize_t io__getline(struct io *io, char **line_out, size_t *line_len_out)
{
char buf[128];
int buf_pos = 0;
char *line = NULL, *temp;
size_t line_len = 0;
int ch = 0;
/* TODO: reuse previously allocated memory. */
free(*line_out);
while (ch != '\n') {
ch = io__get_char(io);
if (ch < 0)
break;
if (buf_pos == sizeof(buf)) {
temp = realloc(line, line_len + sizeof(buf));
if (!temp)
goto err_out;
line = temp;
memcpy(&line[line_len], buf, sizeof(buf));
line_len += sizeof(buf);
buf_pos = 0;
}
buf[buf_pos++] = (char)ch;
}
temp = realloc(line, line_len + buf_pos + 1);
if (!temp)
goto err_out;
line = temp;
memcpy(&line[line_len], buf, buf_pos);
line[line_len + buf_pos] = '\0';
line_len += buf_pos;
*line_out = line;
*line_len_out = line_len;
return line_len;
err_out:
free(line);
*line_out = NULL;
return -ENOMEM;
}
#endif /* __API_IO__ */
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