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/* 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__ */
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