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/************************************************************
* lib_getenv.c
*
* Copyright (C) 2007 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name Gregory Nutt nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
************************************************************/
/************************************************************
* Compilation Switches
************************************************************/
/************************************************************
* Included Files
************************************************************/
#include <sys/types.h>
#include <stdlib.h>
#include <debug.h>
/************************************************************
* Definitions
************************************************************/
/************************************************************
* Private Type Declarations
************************************************************/
/************************************************************
* Private Function Prototypes
************************************************************/
/**********************************************************
* Global Constant Data
**********************************************************/
/************************************************************
* Global Variables
************************************************************/
/**********************************************************
* Private Constant Data
**********************************************************/
#ifdef ENVIRONMENT_STRINGS
static const char environment[] = ENVIRONMENT_STRINGS;
#else
static const char environment[] = "";
#endif
/************************************************************
* Private Variables
************************************************************/
/************************************************************
* Function: getenv
*
* Description:
*
* getenv() searches the environment list for a string of
* the form name=value, and returns a pointer to the value
* in the current environment if such a string is present,
* otherwise a NULL pointer. name can be either the desired
* name, null-terminated, or of the form name=value, in which
* case getenv() uses the portion to the left of the = as the
* search key.
*
* getenv() is (by convention) declared in stdlib.h
*
************************************************************/
char *getenv(const char *name)
{
const char *penv = environment;
int size = sizeof(environment);
const char *pend = &environment[size-1];
const char *ptmp;
ldbg("name=\"%s\"\n", name);
if (name)
{
/* Process each string in the environment. */
while (penv < pend)
{
lvdbg("Compare to=\"%s\"\n", penv);
/* The logic below basically implements a version of
* strcmp where the strings may be terminated with = signs.
*/
ptmp = name;
for (;;)
{
/* Are we at the end of the name-to-matching? */
if (!*ptmp || *ptmp == '=')
{
/* Yes.. are we also at the end of the matching-name? */
if (*penv == '=')
{
/* Yes.. return the pointer to the value. */
ldbg("Returning \"%s\"\n", penv+1);
return ((char*)penv+1);
}
else
{
/* No.. Skip to the next name matching name candidate. */
while(*penv++);
break;
}
}
/* NO.. are we at the end of the matching name candidate?
* OR.. do the corresponding characters not match.
*/
else if (*penv != *ptmp)
{
/* Yes.. Skip to the next name matching name candidate. */
while(*penv++);
break;
}
else
{
/* No.. try the next characters. */
penv++; ptmp++;
}
}
}
}
/* If we got here, then no matching string was found. */
ldbg("Returning NULL\n");
return NULL;
}
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