1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * Lightweight buffered reading library.
4 *
5 * Copyright 2019 Google LLC.
6 */
7 #ifndef __API_IO__
8 #define __API_IO__
9
10 #include <stdlib.h>
11 #include <unistd.h>
12
13 struct io {
14 /* File descriptor being read/ */
15 int fd;
16 /* Size of the read buffer. */
17 unsigned int buf_len;
18 /* Pointer to storage for buffering read. */
19 char *buf;
20 /* End of the storage. */
21 char *end;
22 /* Currently accessed data pointer. */
23 char *data;
24 /* Set true on when the end of file on read error. */
25 bool eof;
26 };
27
io__init(struct io * io,int fd,char * buf,unsigned int buf_len)28 static inline void io__init(struct io *io, int fd,
29 char *buf, unsigned int buf_len)
30 {
31 io->fd = fd;
32 io->buf_len = buf_len;
33 io->buf = buf;
34 io->end = buf;
35 io->data = buf;
36 io->eof = false;
37 }
38
39 /* Reads one character from the "io" file with similar semantics to fgetc. */
io__get_char(struct io * io)40 static inline int io__get_char(struct io *io)
41 {
42 char *ptr = io->data;
43
44 if (io->eof)
45 return -1;
46
47 if (ptr == io->end) {
48 ssize_t n = read(io->fd, io->buf, io->buf_len);
49
50 if (n <= 0) {
51 io->eof = true;
52 return -1;
53 }
54 ptr = &io->buf[0];
55 io->end = &io->buf[n];
56 }
57 io->data = ptr + 1;
58 return *ptr;
59 }
60
61 /* Read a hexadecimal value with no 0x prefix into the out argument hex. If the
62 * first character isn't hexadecimal returns -2, io->eof returns -1, otherwise
63 * returns the character after the hexadecimal value which may be -1 for eof.
64 * If the read value is larger than a u64 the high-order bits will be dropped.
65 */
io__get_hex(struct io * io,__u64 * hex)66 static inline int io__get_hex(struct io *io, __u64 *hex)
67 {
68 bool first_read = true;
69
70 *hex = 0;
71 while (true) {
72 int ch = io__get_char(io);
73
74 if (ch < 0)
75 return ch;
76 if (ch >= '0' && ch <= '9')
77 *hex = (*hex << 4) | (ch - '0');
78 else if (ch >= 'a' && ch <= 'f')
79 *hex = (*hex << 4) | (ch - 'a' + 10);
80 else if (ch >= 'A' && ch <= 'F')
81 *hex = (*hex << 4) | (ch - 'A' + 10);
82 else if (first_read)
83 return -2;
84 else
85 return ch;
86 first_read = false;
87 }
88 }
89
90 /* Read a positive decimal value with out argument dec. If the first character
91 * isn't a decimal returns -2, io->eof returns -1, otherwise returns the
92 * character after the decimal value which may be -1 for eof. If the read value
93 * is larger than a u64 the high-order bits will be dropped.
94 */
io__get_dec(struct io * io,__u64 * dec)95 static inline int io__get_dec(struct io *io, __u64 *dec)
96 {
97 bool first_read = true;
98
99 *dec = 0;
100 while (true) {
101 int ch = io__get_char(io);
102
103 if (ch < 0)
104 return ch;
105 if (ch >= '0' && ch <= '9')
106 *dec = (*dec * 10) + ch - '0';
107 else if (first_read)
108 return -2;
109 else
110 return ch;
111 first_read = false;
112 }
113 }
114
115 #endif /* __API_IO__ */
116