1 /*- 2 * Copyright (c) 2013 David Chisnall 3 * All rights reserved. 4 * 5 * This software was developed by SRI International and the University of 6 * Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237) 7 * ("CTSRD"), as part of the DARPA CRASH research programme. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 * 30 * $FreeBSD$ 31 */ 32 33 #ifndef _INPUT_BUFFER_HH_ 34 #define _INPUT_BUFFER_HH_ 35 #include "util.hh" 36 #include <assert.h> 37 38 namespace dtc 39 { 40 41 /** 42 * Class encapsulating the input file. Can be used as a const char*, but has 43 * range checking. Attempting to access anything out of range will return a 0 44 * byte. The input buffer can be cheaply copied, without copying the 45 * underlying memory, however it is the user's responsibility to ensure that 46 * such copies do not persist beyond the lifetime of the underlying memory. 47 * 48 * This also contains methods for reporting errors and for consuming the token 49 * stream. 50 */ 51 class input_buffer 52 { 53 protected: 54 /** 55 * The buffer. This class doesn't own the buffer, but the 56 * mmap_input_buffer subclass does. 57 */ 58 const char* buffer; 59 /** 60 * The size of the buffer. 61 */ 62 int size; 63 private: 64 /** 65 * The current place in the buffer where we are reading. This class 66 * keeps a separate size, pointer, and cursor so that we can move 67 * forwards and backwards and still have checks that we haven't fallen 68 * off either end. 69 */ 70 int cursor; 71 /** 72 * Private constructor. This is used to create input buffers that 73 * refer to the same memory, but have different cursors. 74 */ 75 input_buffer(const char* b, int s, int c) : buffer(b), size(s), 76 cursor(c) {} 77 /** 78 * Reads forward past any spaces. The DTS format is not whitespace 79 * sensitive and so we want to scan past whitespace when reading it. 80 */ 81 void skip_spaces(); 82 public: 83 /** 84 * Virtual destructor. Does nothing, but exists so that subclasses 85 * that own the memory can run cleanup code for deallocating it. 86 */ 87 virtual ~input_buffer() {}; 88 /** 89 * Constructs an empty buffer. 90 */ 91 input_buffer() : buffer(0), size(0), cursor(0) {} 92 /** 93 * Constructs a new buffer with a specified memory region and size. 94 */ 95 input_buffer(const char* b, int s) : buffer(b), size(s), cursor(0){} 96 /** 97 * Returns a new input buffer referring into this input, clamped to the 98 * specified size. If the requested buffer would fall outside the 99 * range of this one, then it returns an empty buffer. 100 * 101 * The returned buffer shares the same underlying storage as the 102 * original. This is intended to be used for splitting up the various 103 * sections of a device tree blob. Requesting a size of 0 will give a 104 * buffer that extends to the end of the available memory. 105 */ 106 input_buffer buffer_from_offset(int offset, int s=0); 107 /** 108 * Returns true if this buffer has no unconsumed space in it. 109 */ 110 inline bool empty() 111 { 112 return cursor >= size; 113 } 114 /** 115 * Dereferencing operator, allows the buffer to be treated as a char* 116 * and dereferenced to give a character. This returns a null byte if 117 * the cursor is out of range. 118 */ 119 inline char operator*() 120 { 121 if (cursor >= size) { return '\0'; } 122 if (cursor < 0) { return '\0'; } 123 return buffer[cursor]; 124 } 125 /** 126 * Array subscripting operator, returns a character at the specified 127 * index offset from the current cursor. The offset may be negative, 128 * to reread characters that have already been read. If the current 129 * cursor plus offset is outside of the range, this returns a nul 130 * byte. 131 */ 132 inline char operator[](int offset) 133 { 134 if (cursor + offset >= size) { return '\0'; } 135 if (cursor + offset < 0) { return '\0'; } 136 return buffer[cursor + offset]; 137 } 138 /** 139 * Increments the cursor, iterating forward in the buffer. 140 */ 141 inline input_buffer &operator++() 142 { 143 cursor++; 144 return *this; 145 } 146 /** 147 * Cast to char* operator. Returns a pointer into the buffer that can 148 * be used for constructing strings. 149 */ 150 inline operator const char*() 151 { 152 if (cursor >= size) { return 0; } 153 if (cursor < 0) { return 0; } 154 return &buffer[cursor]; 155 } 156 /** 157 * Consumes a character. Moves the cursor one character forward if the 158 * next character matches the argument, returning true. If the current 159 * character does not match the argument, returns false. 160 */ 161 inline bool consume(char c) 162 { 163 if ((*this)[0] == c) 164 { 165 ++(*this); 166 return true; 167 } 168 return false; 169 } 170 /** 171 * Consumes a string. If the (null-terminated) string passed as the 172 * argument appears in the input, advances the cursor to the end and 173 * returns true. Returns false if the string does not appear at the 174 * current point in the input. 175 */ 176 bool consume(const char *str); 177 /** 178 * Reads an integer in base 8, 10, or 16. Returns true and advances 179 * the cursor to the end of the integer if the cursor points to an 180 * integer, returns false and does not move the cursor otherwise. 181 * 182 * The parsed value is returned via the argument. 183 */ 184 bool consume_integer(long long &outInt); 185 /** 186 * Template function that consumes a binary value in big-endian format 187 * from the input stream. Returns true and advances the cursor if 188 * there is a value of the correct size. This function assumes that 189 * all values must be natively aligned, and so advances the cursor to 190 * the correct alignment before reading. 191 */ 192 template<typename T> 193 bool consume_binary(T &out) 194 { 195 int align = 0; 196 int type_size = sizeof(T); 197 if (cursor % type_size != 0) 198 { 199 align = type_size - (cursor % type_size); 200 } 201 if (size < cursor + align + type_size) 202 { 203 return false; 204 } 205 cursor += align; 206 assert(cursor % type_size == 0); 207 out = 0; 208 for (int i=0 ; i<type_size ; ++i) 209 { 210 out <<= 8; 211 out |= (((T)buffer[cursor++]) & 0xff); 212 } 213 return true; 214 } 215 /** 216 * Consumes two hex digits and return the resulting byte via the first 217 * argument. If the next two characters are hex digits, returns true 218 * and advances the cursor. If not, then returns false and leaves the 219 * cursor in place. 220 */ 221 bool consume_hex_byte(uint8_t &outByte); 222 /** 223 * Advances the cursor to the start of the next token, skipping 224 * comments and whitespace. If the cursor already points to the start 225 * of a token, then this function does nothing. 226 */ 227 input_buffer &next_token(); 228 /** 229 * Prints a message indicating the location of a parse error. 230 */ 231 void parse_error(const char *msg); 232 /** 233 * Dumps the current cursor value and the unconsumed values in the 234 * input buffer to the standard error. This method is intended solely 235 * for debugging. 236 */ 237 void dump(); 238 }; 239 /** 240 * Explicit specialisation for reading a single byte. 241 */ 242 template<> 243 inline bool input_buffer::consume_binary(uint8_t &out) 244 { 245 if (size < cursor + 1) 246 { 247 return false; 248 } 249 out = buffer[cursor++]; 250 return true; 251 } 252 253 /** 254 * Subclass of input_buffer that mmap()s a file and owns the resulting memory. 255 * When this object is destroyed, the memory is unmapped. 256 */ 257 struct mmap_input_buffer : public input_buffer 258 { 259 /** 260 * Constructs a new buffer from the file passed in as a file 261 * descriptor. 262 */ 263 mmap_input_buffer(int fd); 264 /** 265 * Unmaps the buffer, if one exists. 266 */ 267 virtual ~mmap_input_buffer(); 268 }; 269 /** 270 * Input buffer read from standard input. This is used for reading device tree 271 * blobs and source from standard input. It reads the entire input into 272 * malloc'd memory, so will be very slow for large inputs. DTS and DTB files 273 * are very rarely more than 10KB though, so this is probably not a problem. 274 */ 275 struct stream_input_buffer : public input_buffer 276 { 277 /** 278 * The buffer that will store the data read from the standard input. 279 */ 280 std::vector<char> b; 281 /** 282 * Constructs a new buffer from the standard input. 283 */ 284 stream_input_buffer(); 285 }; 286 287 } // namespace dtc 288 289 #endif // !_INPUT_BUFFER_HH_ 290