1 /* 2 * A simple kernel FIFO implementation. 3 * 4 * Copyright (C) 2004 Stelian Pop <stelian (at) popies.net> 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License as published by 8 * the Free Software Foundation; either version 2 of the License, or 9 * (at your option) any later version. 10 * 11 * This program is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 * GNU General Public License for more details. 15 * 16 * You should have received a copy of the GNU General Public License 17 * along with this program; if not, write to the Free Software 18 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 19 * 20 */ 21 22 #include <stdio.h> 23 #include <stdlib.h> 24 #include <string.h> 25 26 #include "fifo.h" 27 28 struct fifo *fifo_alloc(unsigned int size) 29 { 30 struct fifo *fifo; 31 32 fifo = malloc(sizeof(struct fifo)); 33 if (!fifo) 34 return NULL; 35 36 fifo->buffer = malloc(size); 37 fifo->size = size; 38 fifo->in = fifo->out = 0; 39 40 return fifo; 41 } 42 43 void fifo_free(struct fifo *fifo) 44 { 45 free(fifo->buffer); 46 free(fifo); 47 } 48 49 unsigned int fifo_put(struct fifo *fifo, void *buffer, unsigned int len) 50 { 51 unsigned int l; 52 53 len = min(len, fifo_room(fifo)); 54 55 /* first put the data starting from fifo->in to buffer end */ 56 l = min(len, fifo->size - (fifo->in & (fifo->size - 1))); 57 memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l); 58 59 /* then put the rest (if any) at the beginning of the buffer */ 60 memcpy(fifo->buffer, buffer + l, len - l); 61 62 /* 63 * Ensure that we add the bytes to the fifo -before- 64 * we update the fifo->in index. 65 */ 66 67 fifo->in += len; 68 69 return len; 70 } 71 72 unsigned int fifo_get(struct fifo *fifo, void *buf, unsigned int len) 73 { 74 len = min(len, fifo->in - fifo->out); 75 76 if (buf) { 77 unsigned int l; 78 79 /* 80 * first get the data from fifo->out until the end of the buffer 81 */ 82 l = min(len, fifo->size - (fifo->out & (fifo->size - 1))); 83 memcpy(buf, fifo->buffer + (fifo->out & (fifo->size - 1)), l); 84 85 /* 86 * then get the rest (if any) from the beginning of the buffer 87 */ 88 memcpy(buf + l, fifo->buffer, len - l); 89 } 90 91 fifo->out += len; 92 93 if (fifo->in == fifo->out) 94 fifo->in = fifo->out = 0; 95 96 return len; 97 } 98
