b08a86171f
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3 42af7a65-404d-4744-a932-0658087f49c3
164 lines
5.3 KiB
C
164 lines
5.3 KiB
C
/************************************************************
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* lib_getenv.c
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*
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* Copyright (C) 2007 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name Gregory Nutt nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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************************************************************/
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/************************************************************
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* Compilation Switches
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************************************************************/
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/************************************************************
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* Included Files
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************************************************************/
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#include <sys/types.h>
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#include <stdlib.h>
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#include <debug.h>
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/************************************************************
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* Definitions
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************************************************************/
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/************************************************************
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* Private Type Declarations
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************************************************************/
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/************************************************************
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* Private Function Prototypes
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************************************************************/
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/**********************************************************
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* Global Constant Data
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**********************************************************/
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/************************************************************
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* Global Variables
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************************************************************/
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/**********************************************************
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* Private Constant Data
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**********************************************************/
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#ifdef ENVIRONMENT_STRINGS
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static const char environment[] = ENVIRONMENT_STRINGS;
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#else
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static const char environment[] = "";
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#endif
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/************************************************************
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* Private Variables
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************************************************************/
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/************************************************************
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* Function: getenv
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*
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* Description:
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*
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* getenv() searches the environment list for a string of
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* the form name=value, and returns a pointer to the value
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* in the current environment if such a string is present,
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* otherwise a NULL pointer. name can be either the desired
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* name, null-terminated, or of the form name=value, in which
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* case getenv() uses the portion to the left of the = as the
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* search key.
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*
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* getenv() is (by convention) declared in stdlib.h
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*
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************************************************************/
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char *getenv(const char *name)
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{
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const char *penv = environment;
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int size = sizeof(environment);
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const char *pend = &environment[size-1];
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const char *ptmp;
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dbg("getenv(ge): name=\"%s\"\n", name);
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if (name) {
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/* Process each string in the environment. */
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while (penv < pend) {
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vdbg("(ge):\tCompare to=\"%s\"\n", penv);
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/* The logic below basically implements a version of
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* strcmp where the strings may be terminated with = signs. */
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ptmp = name;
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for (;;) {
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/* Are we at the end of the name-to-matching? */
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if ((!*ptmp) || (*ptmp == '=')) {
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/* Yes.. are we also at the end of the matching-name? */
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if (*penv == '=') {
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/* Yes.. return the pointer to the value. */
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dbg("(ge):\tReturning \"%s\"\n", penv+1);
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return ((char*)penv+1);
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} /* end if */
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else {
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/* No.. Skip to the next name matching name candidate. */
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while(*penv++);
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break;
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} /* end else */
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} /* end if */
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/* NO.. are we at the end of the matching name candidate? */
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/* OR.. do the corresponding characters not match. */
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else if (*penv != *ptmp) {
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/* Yes.. Skip to the next name matching name candidate. */
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while(*penv++);
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break;
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} /* end else if */
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else {
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/* No.. try the next characters. */
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penv++; ptmp++;
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} /* end else */
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} /* end for */
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} /* end while */
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} /* end if */
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/* If we got here, then no matching string was found. */
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dbg("(ge):\tReturning NULL\n");
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return NULL;
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} /* end getenv */
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