Webcam Library Reference Documentation

Libs/libwebcam/libwebcam.h

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/*
 * Copyright (c) 2006-2008 Logitech.
 *
 * This file is part of libwebcam.
 * 
 * libwebcam is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * libwebcam is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with libwebcam.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef C_LIBWEBCAM_H
#define C_LIBWEBCAM_H


#include <assert.h>


/*
 * Constants
 */

#define USE_UVCVIDEO

#define USE_LOGITECH_DYNCTRL

#undef  DISABLE_UVCVIDEO_DYNCTRL
// There is no dynctrl support without uvcvideo support
#ifndef USE_UVCVIDEO
    #define DISABLE_UVCVIDEO_DYNCTRL
#endif

#define ENABLE_V4L2_ADVANCED_CONTROL_ENUMERATION

#define DYNCTRL_IGNORE_EEXIST_AFTER_PASS1

#define MAX_HANDLES                     32

#define DISABLE_LOCKING                 1

#define DEBUG_LOCKING                   1

#define UNKNOWN_CONTROL_NAME            "Unknown control"
#define CONTROL_IO_ERROR_RETRIES        2



/*
 * Macros
 */

#define GET_HANDLE(handle)      (handle_list.handles[(handle)])

#define HANDLE_OPEN(handle)     ((handle) < MAX_HANDLES && GET_HANDLE(handle).open)

#define HANDLE_VALID(handle)    (HANDLE_OPEN(handle) && GET_HANDLE(handle).device)

#define V4L2_MENU_CTRL_MAX_NAME_SIZE    sizeof(((struct v4l2_querymenu *)NULL)->name)

#define MAKE_FOURCC(c1,c2,c3,c4) \
    (unsigned int)((long)c1 | (long)c2 << 8 | (long)c3 << 16 | (long)c4 << 24)



/*
 * Structures
 */

typedef struct _Control {
    CControl        control;
    int             v4l2_control;
    struct _Control * next;

} Control;

typedef struct _ControlList {
    Control         * first;
    pthread_mutex_t mutex;
    int             count;

} ControlList;

typedef struct _Device {
    CDevice         device;
    char            v4l2_name[NAME_MAX];
    int             handles;
    ControlList     controls;
    int             valid;
    struct _Device  * next;

} Device;

typedef struct _DeviceList {
    Device          * first;
    pthread_mutex_t mutex;
    int             count;

} DeviceList;

typedef struct _Handle {
    Device          * device;
    int             open;
    int             last_system_error;
    
} Handle;

typedef struct _HandleList {
    Handle          handles[MAX_HANDLES];
    pthread_mutex_t mutex;
    int             first_free;
    
} HandleList;



/*
 * Globals
 */

extern int initialized;
extern HandleList handle_list;

extern int open_v4l2_device(char *device_name);



/*
 * Helper functions
 */

static inline CResult lock_mutex (pthread_mutex_t *mutex)
{
#ifndef DISABLE_LOCKING
#ifdef DEBUG_LOCKING
    fprintf(stderr, "Acquiring mutex 0x%08x ...\n", (unsigned int)mutex);
#endif
    int ret = pthread_mutex_lock(mutex);
#ifdef DEBUG_LOCKING
    fprintf(stderr, "Acquisition of mutex 0x%08x %s.\n", (unsigned int)mutex,
            ret ? "failed" : "successful");
#endif
    assert(ret == 0);
    return ret ? C_SYNC_ERROR : C_SUCCESS;
#else
    return C_SUCCESS;
#endif
}


static inline void unlock_mutex (pthread_mutex_t *mutex)
{
#ifndef DISABLE_LOCKING
#ifdef DEBUG_LOCKING
    fprintf(stderr, "Releasing mutex 0x%08x ...\n", (unsigned int)mutex);
#endif
    int ret = pthread_mutex_unlock(mutex);
#ifdef DEBUG_LOCKING
    fprintf(stderr, "Release of mutex 0x%08x %s.\n", (unsigned int)mutex,
            ret ? "failed" : "successful");
#endif
    assert(ret == 0);
#endif
}


static inline void copy_string_to_buffer (char **target, char *source, void *buffer, unsigned int *offset)
{
    unsigned int length = strlen(source);
    *target = (char *)buffer + *offset;
    memcpy(*target, source, length + 1);
    *offset += length + 1;
}


#endif /* C_LIBWEBCAM_H */

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