1 /* 2 * Copyright (c) 2015 Google, Inc 3 * Written by Simon Glass <sjg@chromium.org> 4 * 5 * Copyright (c) 1992 Simon Glass 6 * 7 * SPDX-License-Identifier: GPL-2.0+ 8 */ 9 10 #ifndef _MEMBUFF_H 11 #define _MEMBUFF_H 12 13 /** 14 * @struct membuff: holds the state of a membuff - it is used for input and 15 * output buffers. The buffer extends from @start to (@start + @size - 1). 16 * Data in the buffer extends from @tail to @head: it is written in at 17 * @head and read out from @tail. The membuff is empty when @head == @tail 18 * and full when adding another character would make @head == @tail. We 19 * therefore waste one character in the membuff to avoid having an extra flag 20 * to determine whether (when @head == @tail) the membuff is empty or full. 21 * 22 * xxxxxx data 23 * ...... empty 24 * 25 * .............xxxxxxxxxxxxxxxx......................... 26 * ^ ^ 27 * tail head 28 * 29 * xxxxxxxxxxxxx................xxxxxxxxxxxxxxxxxxxxxxxxx 30 * ^ ^ 31 * head tail 32 */ 33 struct membuff { 34 char *start; /** the start of the buffer */ 35 char *end; /** the end of the buffer (start + length) */ 36 char *head; /** current buffer head */ 37 char *tail; /** current buffer tail */ 38 }; 39 40 /** 41 * membuff_purge() - reset a membuff to the empty state 42 * 43 * Initialise head and tail pointers so that the membuff becomes empty. 44 * 45 * @mb: membuff to purge 46 */ 47 void membuff_purge(struct membuff *mb); 48 49 /** 50 * membuff_putraw() - find out where bytes can be written 51 * 52 * Work out where in the membuff some data could be written. Return a pointer 53 * to the address and the number of bytes which can be written there. If 54 * @update is true, the caller must then write the data immediately, since 55 * the membuff is updated as if the write has been done, 56 * 57 * Note that because the spare space in a membuff may not be contiguous, this 58 * function may not return @maxlen even if there is enough space in the 59 * membuff. However, by calling this function twice (with @update == true), 60 * you will get access to all the spare space. 61 * 62 * @mb: membuff to adjust 63 * @maxlen: the number of bytes we want to write 64 * @update: true to update the membuff as if the write happened, false to not 65 * @data: the address data can be written to 66 * @return number of bytes which can be written 67 */ 68 int membuff_putraw(struct membuff *mb, int maxlen, bool update, char **data); 69 70 /** 71 * membuff_getraw() - find and return a pointer to available bytes 72 * 73 * Returns a pointer to any valid input data in the given membuff and 74 * optionally marks it as read. Note that not all input data may not be 75 * returned, since data is not necessarily contiguous in the membuff. However, 76 * if you call this function twice (with @update == true) you are guaranteed 77 * to get all available data, in at most two installments. 78 * 79 * @mb: membuff to adjust 80 * @maxlen: maximum number of bytes to get 81 * @update: true to update the membuff as if the bytes have been read (use 82 * false to check bytes without reading them) 83 * @data: returns address of data in input membuff 84 * @return the number of bytes available at *@data 85 */ 86 int membuff_getraw(struct membuff *mb, int maxlen, bool update, char **data); 87 88 /** 89 * membuff_putbyte() - Writes a byte to a membuff 90 * 91 * @mb: membuff to adjust 92 * @ch: byte to write 93 * @return true on success, false if membuff is full 94 */ 95 bool membuff_putbyte(struct membuff *mb, int ch); 96 97 /** 98 * @mb: membuff to adjust 99 * membuff_getbyte() - Read a byte from the membuff 100 * @return the byte read, or -1 if the membuff is empty 101 */ 102 int membuff_getbyte(struct membuff *mb); 103 104 /** 105 * membuff_peekbyte() - check the next available byte 106 * 107 * Return the next byte which membuff_getbyte() would return, without 108 * removing it from the membuff. 109 * 110 * @mb: membuff to adjust 111 * @return the byte peeked, or -1 if the membuff is empty 112 */ 113 int membuff_peekbyte(struct membuff *mb); 114 115 /** 116 * membuff_get() - get data from a membuff 117 * 118 * Copies any available data (up to @maxlen bytes) to @buff and removes it 119 * from the membuff. 120 * 121 * @mb: membuff to adjust 122 * @Buff: address of membuff to transfer bytes to 123 * @maxlen: maximum number of bytes to read 124 * @return the number of bytes read 125 */ 126 int membuff_get(struct membuff *mb, char *buff, int maxlen); 127 128 /** 129 * membuff_put() - write data to a membuff 130 * 131 * Writes some data to a membuff. Returns the number of bytes added. If this 132 * is less than @lnehgt, then the membuff got full 133 * 134 * @mb: membuff to adjust 135 * @data: the data to write 136 * @length: number of bytes to write from 'data' 137 * @return the number of bytes added 138 */ 139 int membuff_put(struct membuff *mb, const char *buff, int length); 140 141 /** 142 * membuff_isempty() - check if a membuff is empty 143 * 144 * @mb: membuff to check 145 * @return true if empty, else false 146 */ 147 bool membuff_isempty(struct membuff *mb); 148 149 /** 150 * membuff_avail() - check available data in a membuff 151 * 152 * @mb: membuff to check 153 * @return number of bytes of data available 154 */ 155 int membuff_avail(struct membuff *mb); 156 157 /** 158 * membuff_size() - get the size of a membuff 159 * 160 * Note that a membuff can only old data up to one byte less than its size. 161 * 162 * @mb: membuff to check 163 * @return total size 164 */ 165 int membuff_size(struct membuff *mb); 166 167 /** 168 * membuff_makecontig() - adjust all membuff data to be contiguous 169 * 170 * This places all data in a membuff into a single contiguous lump, if 171 * possible 172 * 173 * @mb: membuff to adjust 174 * @return true on success 175 */ 176 bool membuff_makecontig(struct membuff *mb); 177 178 /** 179 * membuff_free() - find the number of bytes that can be written to a membuff 180 * 181 * @mb: membuff to check 182 * @return returns the number of bytes free in a membuff 183 */ 184 int membuff_free(struct membuff *mb); 185 186 /** 187 * membuff_readline() - read a line of text from a membuff 188 * 189 * Reads a line of text of up to 'maxlen' characters from a membuff and puts 190 * it in @str. Any character less than @minch is assumed to be the end of 191 * line character 192 * 193 * @mb: membuff to adjust 194 * @str: Place to put the line 195 * @maxlen: Maximum line length (excluding terminator) 196 * @return number of bytes read (including terminator) if a line has been 197 * read, 0 if nothing was there 198 */ 199 int membuff_readline(struct membuff *mb, char *str, int maxlen, int minch); 200 201 /** 202 * membuff_extend_by() - expand a membuff 203 * 204 * Extends a membuff by the given number of bytes 205 * 206 * @mb: membuff to adjust 207 * @by: Number of bytes to increase the size by 208 * @max: Maximum size to allow 209 * @return 0 if the expand succeeded, -ENOMEM if not enough memory, -E2BIG 210 * if the the size would exceed @max 211 */ 212 int membuff_extend_by(struct membuff *mb, int by, int max); 213 214 /** 215 * membuff_init() - set up a new membuff using an existing membuff 216 * 217 * @mb: membuff to set up 218 * @buff: Address of buffer 219 * @size: Size of buffer 220 */ 221 void membuff_init(struct membuff *mb, char *buff, int size); 222 223 /** 224 * membuff_uninit() - clear a membuff so it can no longer be used 225 * 226 * @mb: membuff to uninit 227 */ 228 void membuff_uninit(struct membuff *mb); 229 230 /** 231 * membuff_new() - create a new membuff 232 * 233 * @mb: membuff to init 234 * @size: size of membuff to create 235 * @return 0 if OK, -ENOMEM if out of memory 236 */ 237 int membuff_new(struct membuff *mb, int size); 238 239 /** 240 * membuff_dispose() - free memory allocated to a membuff and uninit it 241 * 242 * @mb: membuff to dispose 243 */ 244 void membuff_dispose(struct membuff *mb); 245 246 #endif 247