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