浅析linux中鼠标数据读取

我们就是去读/dev/input/mice设备节点,源码如下：

#include <stdio.h>#include <errno.h>#include <fcntl.h>#include <sys/select.h>#include <string.h>/* Mouse button bits*/#define WHEEL_UP 0x10#define WHEEL_DOWN 0x08#define BUTTON_L 0x04#define BUTTON_M 0x02#define BUTTON_R 0x01#define SCALE 3 /* default scaling factor for acceleration */#define THRESH 5 /* default threshhold for acceleration */static int xpos; /* current x position of mouse */static int ypos; /* current y position of mouse */static int minx; /* minimum allowed x position */static int maxx; /* maximum allowed x position */static int miny; /* minimum allowed y position */static int maxy; /* maximum allowed y position */static int buttons; /* current state of buttons */static int scale = SCALE; /* acceleration scale factor */static int thresh = THRESH;/* acceleration threshhold */static int mouse_update(int dx, int dy, int dz);static int IMPS2_Read (int *dx, int *dy, int *dz, int *bp);static void mouse_setposition (int newx, int newy);static void mouse_setrange (int newminx, int newminy, int newmaxx, int newmaxy);int mouse_fd;int main(void){    int dx,dy,dz;    static unsigned char imps2_param [] = {243,200,243,100,243,80};//,242};    // 来自vnc4的xc/programs/Xserver/hw/xfree86/input/mouse/mouse.c==>PROT_IMPS2    const char *mdev="/dev/input/mice";     mouse_fd = open (mdev, O_RDWR); // | O_NONBLOCK);    if (mouse_fd < 0) {        printf("[luther.gliethttp]: RW error [please use root user]: %s\n", mdev);         mouse_fd = open (mdev, O_RDONLY); // | O_NONBLOCK);        if (mouse_fd < 0)            return -1;    } else {        write (mouse_fd, imps2_param, sizeof (imps2_param)); // 初始化序列, 这样可以读取4个字节数据        // 0x80用来表示滚轮向上还是向下滚动.de>        // 0xa0表示滚轮向上滚动的同时中键按下         printf("[luther.gliethttp]: imps2_param ok!\n");    }         mouse_setrange(0, 0, 1024, 768);    for (;;) {         IMPS2_Read(&dx, &dy, &dz, &buttons);         mouse_update(dx, dy, dz);         mouse_setposition(xpos, ypos);        printf("[%04d,%04d,0x%04x]\n", xpos, ypos, buttons);    }        return 0;}static int IMPS2_Read (int *dx, int *dy, int *dz, int *bp){    static unsigned char buf[5];    static int buttons[7] = { 0, 1, 3, 0, 2, 0, 0}; // 1左键,2中键,3右键    static int nbytes;    int n;    while ((n = read (mouse_fd, &buf [nbytes], 4 - nbytes))) {        if (n < 0) {            if (errno == EINTR)                continue;            else                return -1;        }         nbytes += n;        if (nbytes == 4) {            int wheel;            // printf("[luther.gliethttp]: %02x %02x %02x %02x\n", buf[0], buf[1], buf[2], buf[3]);            if ((buf[0] & 0xc0) != 0) {                 buf[0] = buf[1];                 buf[1] = buf[2];                 buf[2] = buf[3];                 nbytes = 3;                return -1;            }            /* FORM XFree86 4.0.1 */            *bp = buttons[(buf[0] & 0x07)];            *dx = (buf[0] & 0x10) ? buf[1] - 256 : buf[1];            *dy = (buf[0] & 0x20) ? -(buf[2] - 256) : -buf[2];            /* Is a wheel event? */            if ((wheel = buf[3]) != 0) {                if(wheel > 0x7f) {                    *bp |= WHEEL_UP;                }                else {                    *bp |= WHEEL_DOWN;                }            }                         *dz = 0;             nbytes = 0;            return 1;        }    }    return 0;}static int mouse_update(int dx, int dy, int dz){    int r;    int sign;         sign = 1;    if (dx < 0) {         sign = -1;         dx = -dx;    }    if (dx > thresh)         dx = thresh + (dx - thresh) * scale;     dx *= sign;     xpos += dx;    if( xpos < minx )         xpos = minx;    if( xpos > maxx )         xpos = maxx;     sign = 1;    if (dy < 0) {         sign = -1;         dy = -dy;    }    if (dy > thresh)         dy = thresh + (dy - thresh) * scale;     dy *= sign;     ypos += dy;    if ( ypos < miny )         ypos = miny;    if ( ypos > maxy )         ypos = maxy;    return 1;}static void mouse_setposition (int newx, int newy){    if (newx < minx)         newx = minx;    if (newx > maxx)         newx = maxx;    if (newy < miny)         newy = miny;    if (newy > maxy)         newy = maxy;    if (newx == xpos && newy == ypos)        return;     xpos = newx;     ypos = newy;}static void mouse_setrange (int newminx, int newminy, int newmaxx, int newmaxy){     minx = newminx;     miny = newminy;     maxx = newmaxx;     maxy = newmaxy;     mouse_setposition ((newminx + newmaxx) / 2, (newminy + newmaxy) / 2);}static int mouse_getbutton (void){    return buttons;}static void mouse_getxy (int* x, int* y){    *x = xpos;    *y = ypos;}