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 <errno.h> |
11 | #include <poll.h> |
12 | #include <stdlib.h> |
13 | #include <string.h> |
14 | #include <unistd.h> |
15 | #include <linux/types.h> |
16 | |
17 | struct io { |
18 | /* File descriptor being read/ */ |
19 | int fd; |
20 | /* Size of the read buffer. */ |
21 | unsigned int buf_len; |
22 | /* Pointer to storage for buffering read. */ |
23 | char *buf; |
24 | /* End of the storage. */ |
25 | char *end; |
26 | /* Currently accessed data pointer. */ |
27 | char *data; |
28 | /* Read timeout, 0 implies no timeout. */ |
29 | int timeout_ms; |
30 | /* Set true on when the end of file on read error. */ |
31 | bool eof; |
32 | }; |
33 | |
34 | static inline void io__init(struct io *io, int fd, |
35 | char *buf, unsigned int buf_len) |
36 | { |
37 | io->fd = fd; |
38 | io->buf_len = buf_len; |
39 | io->buf = buf; |
40 | io->end = buf; |
41 | io->data = buf; |
42 | io->timeout_ms = 0; |
43 | io->eof = false; |
44 | } |
45 | |
46 | /* Reads one character from the "io" file with similar semantics to fgetc. */ |
47 | static inline int io__get_char(struct io *io) |
48 | { |
49 | char *ptr = io->data; |
50 | |
51 | if (io->eof) |
52 | return -1; |
53 | |
54 | if (ptr == io->end) { |
55 | ssize_t n; |
56 | |
57 | if (io->timeout_ms != 0) { |
58 | struct pollfd pfds[] = { |
59 | { |
60 | .fd = io->fd, |
61 | .events = POLLIN, |
62 | }, |
63 | }; |
64 | |
65 | n = poll(pfds, 1, io->timeout_ms); |
66 | if (n == 0) |
67 | errno = ETIMEDOUT; |
68 | if (n > 0 && !(pfds[0].revents & POLLIN)) { |
69 | errno = EIO; |
70 | n = -1; |
71 | } |
72 | if (n <= 0) { |
73 | io->eof = true; |
74 | return -1; |
75 | } |
76 | } |
77 | n = read(io->fd, io->buf, io->buf_len); |
78 | |
79 | if (n <= 0) { |
80 | io->eof = true; |
81 | return -1; |
82 | } |
83 | ptr = &io->buf[0]; |
84 | io->end = &io->buf[n]; |
85 | } |
86 | io->data = ptr + 1; |
87 | return *ptr; |
88 | } |
89 | |
90 | /* Read a hexadecimal value with no 0x prefix into the out argument hex. If the |
91 | * first character isn't hexadecimal returns -2, io->eof returns -1, otherwise |
92 | * returns the character after the hexadecimal value which may be -1 for eof. |
93 | * If the read value is larger than a u64 the high-order bits will be dropped. |
94 | */ |
95 | static inline int io__get_hex(struct io *io, __u64 *hex) |
96 | { |
97 | bool first_read = true; |
98 | |
99 | *hex = 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 | *hex = (*hex << 4) | (ch - '0'); |
107 | else if (ch >= 'a' && ch <= 'f') |
108 | *hex = (*hex << 4) | (ch - 'a' + 10); |
109 | else if (ch >= 'A' && ch <= 'F') |
110 | *hex = (*hex << 4) | (ch - 'A' + 10); |
111 | else if (first_read) |
112 | return -2; |
113 | else |
114 | return ch; |
115 | first_read = false; |
116 | } |
117 | } |
118 | |
119 | /* Read a positive decimal value with out argument dec. If the first character |
120 | * isn't a decimal returns -2, io->eof returns -1, otherwise returns the |
121 | * character after the decimal value which may be -1 for eof. If the read value |
122 | * is larger than a u64 the high-order bits will be dropped. |
123 | */ |
124 | static inline int io__get_dec(struct io *io, __u64 *dec) |
125 | { |
126 | bool first_read = true; |
127 | |
128 | *dec = 0; |
129 | while (true) { |
130 | int ch = io__get_char(io); |
131 | |
132 | if (ch < 0) |
133 | return ch; |
134 | if (ch >= '0' && ch <= '9') |
135 | *dec = (*dec * 10) + ch - '0'; |
136 | else if (first_read) |
137 | return -2; |
138 | else |
139 | return ch; |
140 | first_read = false; |
141 | } |
142 | } |
143 | |
144 | /* Read up to and including the first delim. */ |
145 | static inline ssize_t io__getdelim(struct io *io, char **line_out, size_t *line_len_out, int delim) |
146 | { |
147 | char buf[128]; |
148 | int buf_pos = 0; |
149 | char *line = NULL, *temp; |
150 | size_t line_len = 0; |
151 | int ch = 0; |
152 | |
153 | /* TODO: reuse previously allocated memory. */ |
154 | free(*line_out); |
155 | while (ch != delim) { |
156 | ch = io__get_char(io); |
157 | |
158 | if (ch < 0) |
159 | break; |
160 | |
161 | if (buf_pos == sizeof(buf)) { |
162 | temp = realloc(line, line_len + sizeof(buf)); |
163 | if (!temp) |
164 | goto err_out; |
165 | line = temp; |
166 | memcpy(&line[line_len], buf, sizeof(buf)); |
167 | line_len += sizeof(buf); |
168 | buf_pos = 0; |
169 | } |
170 | buf[buf_pos++] = (char)ch; |
171 | } |
172 | temp = realloc(line, line_len + buf_pos + 1); |
173 | if (!temp) |
174 | goto err_out; |
175 | line = temp; |
176 | memcpy(&line[line_len], buf, buf_pos); |
177 | line[line_len + buf_pos] = '\0'; |
178 | line_len += buf_pos; |
179 | *line_out = line; |
180 | *line_len_out = line_len; |
181 | return line_len; |
182 | err_out: |
183 | free(line); |
184 | *line_out = NULL; |
185 | return -ENOMEM; |
186 | } |
187 | |
188 | static inline ssize_t io__getline(struct io *io, char **line_out, size_t *line_len_out) |
189 | { |
190 | return io__getdelim(io, line_out, line_len_out, /*delim=*/delim: '\n'); |
191 | } |
192 | |
193 | #endif /* __API_IO__ */ |
194 | |