/* $Id: sysfs.cpp 15644 2008-12-18 11:16:58Z vboxsync $ */
/** @file
 * IPRT - Linux sysfs access.
 */

/*
 * Copyright (C) 2006-2008 Sun Microsystems, Inc.
 *
 * This file is part of VirtualBox Open Source Edition (OSE), as
 * available from http://www.virtualbox.org. This file is free software;
 * you can redistribute it and/or modify it under the terms of the GNU
 * General Public License (GPL) as published by the Free Software
 * Foundation, in version 2 as it comes in the "COPYING" file of the
 * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
 *
 * The contents of this file may alternatively be used under the terms
 * of the Common Development and Distribution License Version 1.0
 * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
 * VirtualBox OSE distribution, in which case the provisions of the
 * CDDL are applicable instead of those of the GPL.
 *
 * You may elect to license modified versions of this file under the
 * terms and conditions of either the GPL or the CDDL or both.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
 * Clara, CA 95054 USA or visit http://www.sun.com if you need
 * additional information or have any questions.
 */


/*******************************************************************************
*   Header Files                                                               *
*******************************************************************************/
#define LOG_GROUP RTLOGGROUP_SYSTEM
#include <iprt/linux/sysfs.h>
#include <iprt/assert.h>
#include <iprt/param.h>
#include <iprt/path.h>
#include <iprt/string.h>

#include <unistd.h>
#include <stdio.h>
#include <sys/sysctl.h>
#include <sys/stat.h>
#include <sys/fcntl.h>
#include <errno.h>


/**
 * Constructs the path of a sysfs file from the format paramaters passed,
 * prepending "/sys/" if the path is relative.
 *
 * @returns The number of characters returned, or -1 and errno set to ERANGE on
 *        failure.
 *
 * @param   pszBuf     Where to write the path.  Must be at least
 *                     sizeof("/sys/") characters long
 * @param   cchBuf     The size of the buffer pointed to by @a pszBuf.
 * @param   pszFormat  The name format, either absolute or relative to "/sys/".
 * @param   va         The format args.
 */
static ssize_t rtLinuxSysFsConstructPath(char *pszBuf, size_t cchBuf, const char *pszFormat, va_list va)
{
    static const char s_szPrefix[] = "/sys/";
    AssertReturnStmt(cchBuf > sizeof(s_szPrefix), errno = ERANGE, -1);

    size_t cch = RTStrPrintfV(pszBuf, cchBuf, pszFormat, va);
    if (*pszBuf != '/')
    {
        AssertReturnStmt(cchBuf >= cch + sizeof(s_szPrefix), errno = ERANGE, -1);
        memmove(pszBuf + sizeof(s_szPrefix) - 1, pszBuf, cch + 1);
        memcpy(pszBuf, s_szPrefix, sizeof(s_szPrefix) - 1);
        cch += sizeof(s_szPrefix) - 1;
    }
    return cch;
}


RTDECL(bool) RTLinuxSysFsExistsV(const char *pszFormat, va_list va)
{
    int iSavedErrno = errno;

    /*
     * Construct the filename and call stat.
     */
    bool fRet = false;
    char szFilename[RTPATH_MAX];
    ssize_t rc = rtLinuxSysFsConstructPath(szFilename, sizeof(szFilename), pszFormat, va);
    if (rc != -1)
    {
        struct stat st;
        fRet = stat(szFilename, &st) == 0;
    }

    errno = iSavedErrno;
    return fRet;
}


RTDECL(bool) RTLinuxSysFsExists(const char *pszFormat, ...)
{
    va_list va;
    va_start(va, pszFormat);
    bool fRet = RTLinuxSysFsExistsV(pszFormat, va);
    va_end(va);
    return fRet;
}


RTDECL(int) RTLinuxSysFsOpenV(const char *pszFormat, va_list va)
{
    /*
     * Construct the filename and call open.
     */
    char szFilename[RTPATH_MAX];
    ssize_t rc = rtLinuxSysFsConstructPath(szFilename, sizeof(szFilename), pszFormat, va);
    if (rc != -1)
        rc = open(szFilename, O_RDONLY, 0);
    return rc;
}


RTDECL(int) RTLinuxSysFsOpen(const char *pszFormat, ...)
{
    va_list va;
    va_start(va, pszFormat);
    int fd = RTLinuxSysFsOpenV(pszFormat, va);
    va_end(va);
    return fd;
}


RTDECL(void) RTLinuxSysFsClose(int fd)
{
    int iSavedErrno = errno;
    close(fd);
    errno = iSavedErrno;
}


RTDECL(ssize_t) RTLinuxSysFsReadStr(int fd, char *pszBuf, size_t cchBuf)
{
    Assert(cchBuf > 1);
    ssize_t cchRead = read(fd, pszBuf, cchBuf - 1);
    pszBuf[cchRead >= 0 ? cchRead : 0] = '\0';
    return cchRead;
}


RTDECL(int64_t) RTLinuxSysFsReadIntFileV(unsigned uBase, const char *pszFormat, va_list va)
{
    int fd = RTLinuxSysFsOpenV(pszFormat, va);
    if (fd == -1)
        return -1;

    int64_t i64Ret = -1;
    char szNum[128];
    ssize_t cchNum = RTLinuxSysFsReadStr(fd, szNum, sizeof(szNum));
    if (cchNum > 0)
    {
        int rc = RTStrToInt64Ex(szNum, NULL, uBase, &i64Ret);
        if (RT_FAILURE(rc))
        {
            i64Ret = -1;
            errno = -ETXTBSY; /* just something that won't happen at read / open. */
        }
    }
    else if (cchNum == 0)
        errno = -ETXTBSY; /* just something that won't happen at read / open. */

    RTLinuxSysFsClose(fd);
    return i64Ret;
}


RTDECL(int64_t) RTLinuxSysFsReadIntFile(unsigned uBase, const char *pszFormat, ...)
{
    va_list va;
    va_start(va, pszFormat);
    int64_t i64Ret = RTLinuxSysFsReadIntFileV(uBase, pszFormat, va);
    va_end(va);
    return i64Ret;
}


RTDECL(ssize_t) RTLinuxSysFsReadStrFileV(char *pszBuf, size_t cchBuf, const char *pszFormat, va_list va)
{
    int fd = RTLinuxSysFsOpenV(pszFormat, va);
    if (fd == -1)
        return -1;

    ssize_t cchRet = RTLinuxSysFsReadStr(fd, pszBuf, cchBuf);
    RTLinuxSysFsClose(fd);
    if (cchRet > 0)
    {
        char *pchNewLine = (char *)memchr(pszBuf, '\n', cchRet);
        if (pchNewLine)
            *pchNewLine = '\0';
    }
    return cchRet;
}


RTDECL(ssize_t) RTLinuxSysFsReadStrFile(char *pszBuf, size_t cchBuf, const char *pszFormat, ...)
{
    va_list va;
    va_start(va, pszFormat);
    ssize_t cchRet = RTLinuxSysFsReadStrFileV(pszBuf, cchBuf, pszFormat, va);
    va_end(va);
    return cchRet;
}


RTDECL(ssize_t) RTLinuxSysFsGetLinkDestV(char *pszBuf, size_t cchBuf, const char *pszFormat, va_list va)
{
    AssertReturnStmt(cchBuf >= 2, errno = EINVAL, -1);

    /*
     * Construct the filename and read the link.
     */
    char szFilename[RTPATH_MAX];
    int rc = rtLinuxSysFsConstructPath(szFilename, sizeof(szFilename), pszFormat, va);
    if (rc == -1)
        return -1;

    char szLink[RTPATH_MAX];
    rc = readlink(szFilename, szLink, sizeof(szLink));
    if (rc == -1)
        return -1;
    if ((size_t)rc > sizeof(szLink) - 1)
    {
        errno = ERANGE;
        return -1;
    }
    szLink[rc] = '\0'; /* readlink fun. */

    /*
     * Extract the file name component and copy it into the return buffer.
     */
    size_t cchName;
    const char *pszName = RTPathFilename(szLink);
    if (pszName)
    {
        cchName = strlen(pszName);
        if (cchName >= cchBuf)
        {
            errno = ERANGE;
            return -1;
        }
        memcpy(pszBuf, pszName, cchName);
    }
    else
    {
        *pszBuf = '\0';
        cchName = 0;
    }
    return cchName;
}


RTDECL(ssize_t) RTLinuxSysFsGetLinkDest(char *pszBuf, size_t cchBuf, const char *pszFormat, ...)
{
    va_list va;
    va_start(va, pszFormat);
    int rc = RTLinuxSysFsGetLinkDestV(pszBuf, cchBuf, pszFormat, va);
    va_end(va);
    return rc;
}