/*
 * Copyright 2009 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

#undef  _LARGEFILE64_SOURCE
#define _LARGEFILE64_SOURCE 1

/*
 * processutil_md.c - Functions used both by java.lang.UNIXProcess 
 *                    native code and processhelper.c
 */

#include <assert.h>
#include <stddef.h>
#include <stdlib.h>
#include <sys/types.h>
#include <ctype.h>
#include <wait.h>
#include <signal.h>
#include <string.h>
#include <errno.h>
#include <dirent.h>
#include <unistd.h>
#include <fcntl.h>
#include <limits.h>

#include "processutil_md.h"

/**
 * Cached value of JVM's effective PATH.
 * (We don't support putenv("PATH=...") in native code)
 */
const char *jlup_parentPath;

/**
 * Split, canonicalized version of parentPath
 */
const char * const *jlup_parentPathv;

int jlup_isAsciiDigit(char c)
{
  return c >= '0' && c <= '9';
}

void jlup_moveDescriptor(int fd_from, int fd_to)
{
    if (fd_from != fd_to) {
        dup2(fd_from, fd_to);
        close(fd_from);
    }
}

void jlup_initVectorFromBlock(const char**vector, const char* block, int count)
{
    int i;
    const char *p;
    for (i = 0, p = block; i < count; i++) {
        /* Invariant: p always points to the start of a C string. */
        vector[i] = p;
        while (*(p++));
    }
    vector[count] = NULL;
}

void jlup_initialize(void *env)
{
    jlup_parentPath  = jlup_effectivePath();
    jlup_parentPathv = jlup_splitPath(env, jlup_parentPath);
}


int jlup_closeDescriptors(int from_fd)
{
    DIR *dp;
    struct dirent64 *dirp;

    /* We're trying to close all file descriptors, but opendir() might
     * itself be implemented using a file descriptor, and we certainly
     * don't want to close that while it's in use.  We assume that if
     * opendir() is implemented using a file descriptor, then it uses
     * the lowest numbered file descriptor, just like open().  So we
     * close a couple explicitly.  */

    close(from_fd);             /* for possible use by opendir() */
    close(from_fd + 1);         /* another one for good luck */

    if ((dp = opendir("/proc/self/fd")) == NULL)
        return 0;

    /* We use readdir64 instead of readdir to work around Solaris bug
     * 6395699: /proc/self/fd fails to report file descriptors >= 1024 on Solaris 9
     */
    while ((dirp = readdir64(dp)) != NULL) {
        int fd;
        if (jlup_isAsciiDigit(dirp->d_name[0]) &&
            (fd = strtol(dirp->d_name, NULL, 10)) >= from_fd + 2)
            close(fd);
    }

    closedir(dp);

    return 1;
}


/**
 * If PATH is not defined, the OS provides some default value.
 * Unfortunately, there's no portable way to get this value.
 * Fortunately, it's only needed if the child has PATH while we do not.
 */
const char* jlup_defaultPath(void)
{
#ifdef __solaris__
    /* These really are the Solaris defaults! */
    return (geteuid() == 0 || getuid() == 0) ?
        "/usr/xpg4/bin:/usr/ccs/bin:/usr/bin:/opt/SUNWspro/bin:/usr/sbin" :
        "/usr/xpg4/bin:/usr/ccs/bin:/usr/bin:/opt/SUNWspro/bin:";
#else
    return ":/bin:/usr/bin";    /* glibc */
#endif
}

const char* jlup_effectivePath(void)
{
    const char *s = getenv("PATH");
    return (s != NULL) ? s : jlup_defaultPath();
}

int jlup_countOccurrences(const char *s, char c)
{
    int count;
    for (count = 0; *s != '\0'; s++)
        count += (*s == c);
    return count;
}

const char * const *
jlup_splitPath(void *env, const char *path)
{
    const char *p, *q;
    char **pathv;
    int i;
    int count = jlup_countOccurrences(path, ':') + 1;

    pathv = jlup_xmalloc (env, (count+1)*sizeof(char *));
    pathv[count] = NULL;
    for (p = path, i = 0; i < count; i++, p = q + 1) {
        for (q = p; (*q != ':') && (*q != '\0'); q++)
            ;
        if (q == p)             /* empty PATH component => "." */
            pathv[i] = "./";
        else {
            int addSlash = ((*(q - 1)) != '/');
            pathv[i] = jlup_xmalloc(env, q - p + addSlash + 1);
            memcpy(pathv[i], p, q - p);
            if (addSlash)
                pathv[i][q - p] = '/';
            pathv[i][q - p + addSlash] = '\0';
        }
    }
    return (const char * const *) pathv;
}

/* Version of execvpe when child's PATH differs from parent's */
int
jlup_execvp_usingParentPath(const char *file, const char *const argv[])
{
    char expanded_file[PATH_MAX];
    int filelen = strlen(file);
    int sticky_errno = 0;
    const char * const * dirs;
    /* Search parent's PATH */
    for (dirs = jlup_parentPathv; *dirs; dirs++) {
        const char * dir = *dirs;
        int dirlen = strlen(dir);
        if (filelen + dirlen + 1 >= PATH_MAX) {
            /* Resist the urge to remove this limit;
             * calling malloc after fork is unsafe. */
            errno = ENAMETOOLONG;
            continue;
        }
        strcpy(expanded_file, dir);
        strcpy(expanded_file + dirlen, file);
        execvp(expanded_file, (char **) argv);
        /* There are 3 responses to various classes of errno:
         * return immediately, continue (especially for ENOENT),
         * or continue with "sticky" errno.
         *
         * From exec(3):
         *
         * If permission is denied for a file (the attempted
         * execve returned EACCES), these functions will continue
         * searching the rest of the search path.  If no other
         * file is found, however, they will return with the
         * global variable errno set to EACCES.
         */
        switch (errno) {
        case EACCES:
            sticky_errno = errno;
            /* FALLTHRU */
        case ENOENT:
        case ENOTDIR:
#ifdef ELOOP
        case ELOOP:
#endif
#ifdef ESTALE
        case ESTALE:
#endif
#ifdef ENODEV
        case ENODEV:
#endif
#ifdef ETIMEDOUT
        case ETIMEDOUT:
#endif
            break; /* Try other directories in PATH */
        default:
            return -1;
        }
    }
    if (sticky_errno != 0)
        errno = sticky_errno;
    return -1;
}

/* execvpe should have been included in the Unix standards. */
int
jlup_execvpe(const char *file, const char *const argv[], const char *const envp[])
{
    /* This is one of the rare times it's more portable to declare an
     * external symbol explicitly, rather than via a system header.
     * The declaration is standardized as part of UNIX98, but there is
     * no standard (not even de-facto) header file where the
     * declaration is to be found.  See:
     * http://www.opengroup.org/onlinepubs/009695399/functions/environ.html
     * http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_02.html
     *
     * "All identifiers in this volume of IEEE Std 1003.1-2001, except
     * environ, are defined in at least one of the headers" (!)
     */
    extern char **environ;

    if (envp != NULL)
        environ = (char **) envp;

    if (/* Parent and child environment the same?  Use child PATH. */
        (envp == NULL)

        /* http://www.opengroup.org/onlinepubs/009695399/functions/exec.html
         * "If the file argument contains a slash character, it is used as
         * the pathname for this file.  Otherwise, the path prefix for this
         * file is obtained by a search of the directories passed in the
         * PATH environment variable" */
        || (strchr(file, '/') != NULL)

        /* Parent and child PATH the same?  Use child PATH. */
        || (strcmp(jlup_parentPath, jlup_effectivePath()) == 0)

        /* We want ENOENT, not EACCES, for zero-length program names. */
        || (*file == '\0')) {
	
        return execvp(file, (char **) argv);
    } else {
        return jlup_execvp_usingParentPath(file, argv);
    }
}

void
jlup_closeSafely(int fd)
{
    if (fd != -1)
        close(fd);
}

/*
 * Reads nbyte bytes from file descriptor fd into buf,
 * The read operation is retried in case of EINTR or partial reads.
 *
 * Returns number of bytes read (normally nbyte, but may be less in
 * case of EOF).  In case of read errors, returns -1 and sets errno.
 */
ssize_t
jlup_readFully(int fd, void *buf, size_t nbyte)
{
    ssize_t remaining = nbyte;
    for (;;) {
        ssize_t n = read(fd, buf, remaining);
        if (n == 0) {
            return nbyte - remaining;
        } else if (n > 0) {
            remaining -= n;
            if (remaining <= 0)
                return nbyte;
            /* We were interrupted in the middle of reading the bytes.
             * Unlikely, but possible. */
            buf = (void *) (((char *)buf) + n);
        } else if (errno == EINTR) {
            /* Strange signals like SIGJVM1 are possible at any time.
             * See http://www.dreamsongs.com/WorseIsBetter.html */
        } else {
            return -1;
        }
    }
}