116 lines
2.5 KiB
C
116 lines
2.5 KiB
C
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/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Lightweight buffered reading library.
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*
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* Copyright 2019 Google LLC.
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*/
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#ifndef __API_IO__
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#define __API_IO__
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#include <stdlib.h>
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#include <unistd.h>
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struct io {
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/* File descriptor being read/ */
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int fd;
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/* Size of the read buffer. */
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unsigned int buf_len;
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/* Pointer to storage for buffering read. */
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char *buf;
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/* End of the storage. */
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char *end;
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/* Currently accessed data pointer. */
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char *data;
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/* Set true on when the end of file on read error. */
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bool eof;
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};
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static inline void io__init(struct io *io, int fd,
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char *buf, unsigned int buf_len)
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{
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io->fd = fd;
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io->buf_len = buf_len;
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io->buf = buf;
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io->end = buf;
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io->data = buf;
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io->eof = false;
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}
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/* Reads one character from the "io" file with similar semantics to fgetc. */
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static inline int io__get_char(struct io *io)
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{
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char *ptr = io->data;
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if (io->eof)
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return -1;
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if (ptr == io->end) {
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ssize_t n = read(io->fd, io->buf, io->buf_len);
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if (n <= 0) {
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io->eof = true;
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return -1;
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}
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ptr = &io->buf[0];
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io->end = &io->buf[n];
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}
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io->data = ptr + 1;
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return *ptr;
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}
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/* Read a hexadecimal value with no 0x prefix into the out argument hex. If the
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* first character isn't hexadecimal returns -2, io->eof returns -1, otherwise
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* returns the character after the hexadecimal value which may be -1 for eof.
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* If the read value is larger than a u64 the high-order bits will be dropped.
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*/
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static inline int io__get_hex(struct io *io, __u64 *hex)
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{
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bool first_read = true;
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*hex = 0;
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while (true) {
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int ch = io__get_char(io);
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if (ch < 0)
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return ch;
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if (ch >= '0' && ch <= '9')
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*hex = (*hex << 4) | (ch - '0');
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else if (ch >= 'a' && ch <= 'f')
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*hex = (*hex << 4) | (ch - 'a' + 10);
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else if (ch >= 'A' && ch <= 'F')
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*hex = (*hex << 4) | (ch - 'A' + 10);
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else if (first_read)
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return -2;
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else
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return ch;
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first_read = false;
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}
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}
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/* Read a positive decimal value with out argument dec. If the first character
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* isn't a decimal returns -2, io->eof returns -1, otherwise returns the
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* character after the decimal value which may be -1 for eof. If the read value
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* is larger than a u64 the high-order bits will be dropped.
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*/
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static inline int io__get_dec(struct io *io, __u64 *dec)
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{
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bool first_read = true;
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*dec = 0;
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while (true) {
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int ch = io__get_char(io);
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if (ch < 0)
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return ch;
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if (ch >= '0' && ch <= '9')
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*dec = (*dec * 10) + ch - '0';
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else if (first_read)
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return -2;
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else
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return ch;
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first_read = false;
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}
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}
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#endif /* __API_IO__ */
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