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 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. */ 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 */ 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 */ 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