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
io__init(struct io * io,int fd,char * buf,unsigned int buf_len)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 /* Read from fd filling the buffer. Called when io->data == io->end. */
io__fill_buffer(struct io * io)47 static inline int io__fill_buffer(struct io *io)
48 {
49 ssize_t n;
50
51 if (io->eof)
52 return -1;
53
54 if (io->timeout_ms != 0) {
55 struct pollfd pfds[] = {
56 {
57 .fd = io->fd,
58 .events = POLLIN,
59 },
60 };
61
62 n = poll(pfds, 1, io->timeout_ms);
63 if (n == 0)
64 errno = ETIMEDOUT;
65 if (n > 0 && !(pfds[0].revents & POLLIN)) {
66 errno = EIO;
67 n = -1;
68 }
69 if (n <= 0) {
70 io->eof = true;
71 return -1;
72 }
73 }
74 n = read(io->fd, io->buf, io->buf_len);
75
76 if (n <= 0) {
77 io->eof = true;
78 return -1;
79 }
80 io->data = &io->buf[0];
81 io->end = &io->buf[n];
82 return 0;
83 }
84
85 /* Reads one character from the "io" file with similar semantics to fgetc. */
io__get_char(struct io * io)86 static inline int io__get_char(struct io *io)
87 {
88 if (io->data == io->end) {
89 int ret = io__fill_buffer(io);
90
91 if (ret)
92 return ret;
93 }
94 return *io->data++;
95 }
96
97 /* Read a hexadecimal value with no 0x prefix into the out argument hex. If the
98 * first character isn't hexadecimal returns -2, io->eof returns -1, otherwise
99 * returns the character after the hexadecimal value which may be -1 for eof.
100 * If the read value is larger than a u64 the high-order bits will be dropped.
101 */
io__get_hex(struct io * io,__u64 * hex)102 static inline int io__get_hex(struct io *io, __u64 *hex)
103 {
104 bool first_read = true;
105
106 *hex = 0;
107 while (true) {
108 int ch = io__get_char(io);
109
110 if (ch < 0)
111 return ch;
112 if (ch >= '0' && ch <= '9')
113 *hex = (*hex << 4) | (ch - '0');
114 else if (ch >= 'a' && ch <= 'f')
115 *hex = (*hex << 4) | (ch - 'a' + 10);
116 else if (ch >= 'A' && ch <= 'F')
117 *hex = (*hex << 4) | (ch - 'A' + 10);
118 else if (first_read)
119 return -2;
120 else
121 return ch;
122 first_read = false;
123 }
124 }
125
126 /* Read a positive decimal value with out argument dec. If the first character
127 * isn't a decimal returns -2, io->eof returns -1, otherwise returns the
128 * character after the decimal value which may be -1 for eof. If the read value
129 * is larger than a u64 the high-order bits will be dropped.
130 */
io__get_dec(struct io * io,__u64 * dec)131 static inline int io__get_dec(struct io *io, __u64 *dec)
132 {
133 bool first_read = true;
134
135 *dec = 0;
136 while (true) {
137 int ch = io__get_char(io);
138
139 if (ch < 0)
140 return ch;
141 if (ch >= '0' && ch <= '9')
142 *dec = (*dec * 10) + ch - '0';
143 else if (first_read)
144 return -2;
145 else
146 return ch;
147 first_read = false;
148 }
149 }
150
151 /* Read up to and including the first delim. */
io__getdelim(struct io * io,char ** line_out,size_t * line_len_out,int delim)152 static inline ssize_t io__getdelim(struct io *io, char **line_out, size_t *line_len_out, int delim)
153 {
154 char buf[128];
155 int buf_pos = 0;
156 char *line = NULL, *temp;
157 size_t line_len = 0;
158 int ch = 0;
159
160 /* TODO: reuse previously allocated memory. */
161 free(*line_out);
162 while (ch != delim) {
163 ch = io__get_char(io);
164
165 if (ch < 0)
166 break;
167
168 if (buf_pos == sizeof(buf)) {
169 temp = realloc(line, line_len + sizeof(buf));
170 if (!temp)
171 goto err_out;
172 line = temp;
173 memcpy(&line[line_len], buf, sizeof(buf));
174 line_len += sizeof(buf);
175 buf_pos = 0;
176 }
177 buf[buf_pos++] = (char)ch;
178 }
179 temp = realloc(line, line_len + buf_pos + 1);
180 if (!temp)
181 goto err_out;
182 line = temp;
183 memcpy(&line[line_len], buf, buf_pos);
184 line[line_len + buf_pos] = '\0';
185 line_len += buf_pos;
186 *line_out = line;
187 *line_len_out = line_len;
188 return line_len;
189 err_out:
190 free(line);
191 *line_out = NULL;
192 return -ENOMEM;
193 }
194
io__getline(struct io * io,char ** line_out,size_t * line_len_out)195 static inline ssize_t io__getline(struct io *io, char **line_out, size_t *line_len_out)
196 {
197 return io__getdelim(io, line_out, line_len_out, /*delim=*/'\n');
198 }
199
200 #endif /* __API_IO__ */
201