/* 
 * tclEnv.c --
 *
 *	Tcl support for environment variables, including a setenv
 *	procedure.  This file contains the generic portion of the
 *	environment module.  It is primarily responsible for keeping
 *	the "env" arrays in sync with the system environment variables.
 *
 * Copyright (c) 1991-1994 The Regents of the University of California.
 * Copyright (c) 1994-1998 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclEnv.c,v 1.6 1999/10/29 03:04:00 hobbs Exp $
 */

#include "tclInt.h"
#include "tclPort.h"

TCL_DECLARE_MUTEX(envMutex)	/* To serialize access to environ */

static int cacheSize = 0;	/* Number of env strings in environCache. */
static char **environCache = NULL;
				/* Array containing all of the environment
				 * strings that Tcl has allocated. */

#ifndef USE_PUTENV
static int environSize = 0;	/* Non-zero means that the environ array was
				 * malloced and has this many total entries
				 * allocated to it (not all may be in use at
				 * once).  Zero means that the environment
				 * array is in its original static state. */
#endif

/*
 * Declarations for local procedures defined in this file:
 */

static char *		EnvTraceProc _ANSI_ARGS_((ClientData clientData,
			    Tcl_Interp *interp, char *name1, char *name2,
			    int flags));
static void		ReplaceString _ANSI_ARGS_((CONST char *oldStr,
			    char *newStr));
void			TclSetEnv _ANSI_ARGS_((CONST char *name,
			    CONST char *value));
void			TclUnsetEnv _ANSI_ARGS_((CONST char *name));


/*
 *----------------------------------------------------------------------
 *
 * TclSetupEnv --
 *
 *	This procedure is invoked for an interpreter to make environment
 *	variables accessible from that interpreter via the "env"
 *	associative array.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The interpreter is added to a list of interpreters managed
 *	by us, so that its view of envariables can be kept consistent
 *	with the view in other interpreters.  If this is the first
 *	call to TclSetupEnv, then additional initialization happens,
 *	such as copying the environment to dynamically-allocated space
 *	for ease of management.
 *
 *----------------------------------------------------------------------
 */

void
TclSetupEnv(interp)
    Tcl_Interp *interp;		/* Interpreter whose "env" array is to be
				 * managed. */
{
    Tcl_DString envString;
    char *p1, *p2;
    int i;

    /*
     * Synchronize the values in the environ array with the contents
     * of the Tcl "env" variable.  To do this:
     *    1) Remove the trace that fires when the "env" var is unset.
     *    2) Unset the "env" variable.
     *    3) If there are no environ variables, create an empty "env"
     *       array.  Otherwise populate the array with current values.
     *    4) Add a trace that synchronizes the "env" array.
     */
    
    Tcl_UntraceVar2(interp, "env", (char *) NULL,
	    TCL_GLOBAL_ONLY | TCL_TRACE_WRITES | TCL_TRACE_UNSETS |
	    TCL_TRACE_READS | TCL_TRACE_ARRAY,  EnvTraceProc,
	    (ClientData) NULL);
    
    Tcl_UnsetVar2(interp, "env", (char *) NULL, TCL_GLOBAL_ONLY); 
    
    if (environ[0] == NULL) {
	Tcl_Obj *varNamePtr;
	
	varNamePtr = Tcl_NewStringObj("env", -1);
	Tcl_IncrRefCount(varNamePtr);
	TclArraySet(interp, varNamePtr, NULL);	
	Tcl_DecrRefCount(varNamePtr);
    } else {
	Tcl_MutexLock(&envMutex);
	for (i = 0; environ[i] != NULL; i++) {
	    p1 = Tcl_ExternalToUtfDString(NULL, environ[i], -1, &envString);
	    p2 = strchr(p1, '=');
	    if (p2 == NULL) {
		/*
		 * This condition seem to happen occasionally under some
		 * versions of Solaris; ignore the entry.
		 */
		
		continue;
	    }
	    p2++;
	    p2[-1] = '\0';
	    Tcl_SetVar2(interp, "env", p1, p2, TCL_GLOBAL_ONLY);	
	    Tcl_DStringFree(&envString);
	}
	Tcl_MutexUnlock(&envMutex);
    }

    Tcl_TraceVar2(interp, "env", (char *) NULL,
	    TCL_GLOBAL_ONLY | TCL_TRACE_WRITES | TCL_TRACE_UNSETS |
	    TCL_TRACE_READS | TCL_TRACE_ARRAY,  EnvTraceProc,
	    (ClientData) NULL);
}

/*
 *----------------------------------------------------------------------
 *
 * TclSetEnv --
 *
 *	Set an environment variable, replacing an existing value
 *	or creating a new variable if there doesn't exist a variable
 *	by the given name.  This procedure is intended to be a
 *	stand-in for the  UNIX "setenv" procedure so that applications
 *	using that procedure will interface properly to Tcl.  To make
 *	it a stand-in, the Makefile must define "TclSetEnv" to "setenv".
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The environ array gets updated.
 *
 *----------------------------------------------------------------------
 */

void
TclSetEnv(name, value)
    CONST char *name;		/* Name of variable whose value is to be
				 * set (UTF-8). */
    CONST char *value;		/* New value for variable (UTF-8). */
{
    Tcl_DString envString;
    int index, length, nameLength;
    char *p, *p2, *oldValue;

    /*
     * Figure out where the entry is going to go.  If the name doesn't
     * already exist, enlarge the array if necessary to make room.  If the
     * name exists, free its old entry.
     */

    Tcl_MutexLock(&envMutex);
    index = TclpFindVariable(name, &length);

    if (index == -1) {
#ifndef USE_PUTENV
	if ((length + 2) > environSize) {
	    char **newEnviron;

	    newEnviron = (char **) ckalloc((unsigned)
		    ((length + 5) * sizeof(char *)));
	    memcpy((VOID *) newEnviron, (VOID *) environ,
		    length*sizeof(char *));
	    if (environSize != 0) {
		ckfree((char *) environ);
	    }
	    environ = newEnviron;
	    environSize = length + 5;
	}
	index = length;
	environ[index + 1] = NULL;
#endif
	oldValue = NULL;
	nameLength = strlen(name);
    } else {
	char *env;

	/*
	 * Compare the new value to the existing value.  If they're
	 * the same then quit immediately (e.g. don't rewrite the
	 * value or propagate it to other interpreters).  Otherwise,
	 * when there are N interpreters there will be N! propagations
	 * of the same value among the interpreters.
	 */

	env = Tcl_ExternalToUtfDString(NULL, environ[index], -1, &envString);
	if (strcmp(value, (env + length + 1)) == 0) {
	    Tcl_DStringFree(&envString);
	    Tcl_MutexUnlock(&envMutex);
	    return;
	}
	Tcl_DStringFree(&envString);

	oldValue = environ[index];
	nameLength = length;
    }
	

    /*
     * Create a new entry.  Build a complete UTF string that contains
     * a "name=value" pattern.  Then convert the string to the native
     * encoding, and set the environ array value.
     */

    p = (char *) ckalloc((unsigned) (nameLength + strlen(value) + 2));
    strcpy(p, name);
    p[nameLength] = '=';
    strcpy(p+nameLength+1, value);
    p2 = Tcl_UtfToExternalDString(NULL, p, -1, &envString);

    /*
     * Copy the native string to heap memory.
     */
    
    p = (char *) ckrealloc(p, (unsigned) (strlen(p2) + 1));
    strcpy(p, p2);
    Tcl_DStringFree(&envString);

#ifdef USE_PUTENV
    /*
     * Update the system environment.
     */

    putenv(p);
    index = TclpFindVariable(name, &length);
#else
    environ[index] = p;
#endif

    /*
     * Watch out for versions of putenv that copy the string (e.g. VC++).
     * In this case we need to free the string immediately.  Otherwise
     * update the string in the cache.
     */

    if ((index != -1) && (environ[index] == p)) {
	ReplaceString(oldValue, p);
    }

    Tcl_MutexUnlock(&envMutex);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_PutEnv --
 *
 *	Set an environment variable.  Similar to setenv except that
 *	the information is passed in a single string of the form
 *	NAME=value, rather than as separate name strings.  This procedure
 *	is intended to be a stand-in for the  UNIX "putenv" procedure
 *	so that applications using that procedure will interface
 *	properly to Tcl.  To make it a stand-in, the Makefile will
 *	define "Tcl_PutEnv" to "putenv".
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The environ array gets updated, as do all of the interpreters
 *	that we manage.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_PutEnv(string)
    CONST char *string;		/* Info about environment variable in the
				 * form NAME=value. (native) */
{
    Tcl_DString nameString;   
    int nameLength;
    char *name, *value;

    if (string == NULL) {
	return 0;
    }

    /*
     * First convert the native string to UTF.  Then separate the
     * string into name and value parts, and call TclSetEnv to do
     * all of the real work.
     */

    name = Tcl_ExternalToUtfDString(NULL, string, -1, &nameString);
    value = strchr(name, '=');
    if (value == NULL) {
	return 0;
    }
    nameLength = value - name;
    if (nameLength == 0) {
	return 0;
    }

    value[0] = '\0';
    TclSetEnv(name, value+1);
    Tcl_DStringFree(&nameString);
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * TclUnsetEnv --
 *
 *	Remove an environment variable, updating the "env" arrays
 *	in all interpreters managed by us.  This function is intended
 *	to replace the UNIX "unsetenv" function (but to do this the
 *	Makefile must be modified to redefine "TclUnsetEnv" to
 *	"unsetenv".
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Interpreters are updated, as is environ.
 *
 *----------------------------------------------------------------------
 */

void
TclUnsetEnv(name)
    CONST char *name;		/* Name of variable to remove (UTF-8). */
{
    char *oldValue;
    int length, index;
#ifdef USE_PUTENV
    Tcl_DString envString;
    char *string;
#else
    char **envPtr;
#endif

    Tcl_MutexLock(&envMutex);
    index = TclpFindVariable(name, &length);

    /*
     * First make sure that the environment variable exists to avoid
     * doing needless work and to avoid recursion on the unset.
     */
    
    if (index == -1) {
	Tcl_MutexUnlock(&envMutex);
	return;
    }
    /*
     * Remember the old value so we can free it if Tcl created the string.
     */

    oldValue = environ[index];

    /*
     * Update the system environment.  This must be done before we 
     * update the interpreters or we will recurse.
     */

#ifdef USE_PUTENV
    string = ckalloc(length+2);
    memcpy((VOID *) string, (VOID *) name, (size_t) length);
    string[length] = '=';
    string[length+1] = '\0';
    
    Tcl_UtfToExternalDString(NULL, string, -1, &envString);
    string = ckrealloc(string, (unsigned) (Tcl_DStringLength(&envString)+1));
    strcpy(string, Tcl_DStringValue(&envString));
    Tcl_DStringFree(&envString);

    putenv(string);

    /*
     * Watch out for versions of putenv that copy the string (e.g. VC++).
     * In this case we need to free the string immediately.  Otherwise
     * update the string in the cache.
     */

    if (environ[index] == string) {
	ReplaceString(oldValue, string);
    }
#else
    for (envPtr = environ+index+1; ; envPtr++) {
	envPtr[-1] = *envPtr;
	if (*envPtr == NULL) {
	    break;
	}
    }
    ReplaceString(oldValue, NULL);
#endif

    Tcl_MutexUnlock(&envMutex);
}

/*
 *---------------------------------------------------------------------------
 *
 * TclGetEnv --
 *
 *	Retrieve the value of an environment variable.
 *
 * Results:
 *	The result is a pointer to a string specifying the value of the
 *	environment variable, or NULL if that environment variable does
 *	not exist.  Storage for the result string is allocated in valuePtr;
 *	the caller must call Tcl_DStringFree() when the result is no
 *	longer needed.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

char *
TclGetEnv(name, valuePtr)
    CONST char *name;		/* Name of environment variable to find
				 * (UTF-8). */
    Tcl_DString *valuePtr;	/* Uninitialized or free DString in which
				 * the value of the environment variable is
				 * stored. */
{
    int length, index;
    char *result;

    Tcl_MutexLock(&envMutex);
    index = TclpFindVariable(name, &length);
    result = NULL;
    if (index != -1) {
	Tcl_DString envStr;
	
	result = Tcl_ExternalToUtfDString(NULL, environ[index], -1, &envStr);
	result += length;
	if (*result == '=') {
	    result++;
	    Tcl_DStringInit(valuePtr);
	    Tcl_DStringAppend(valuePtr, result, -1);
	    result = Tcl_DStringValue(valuePtr);
	} else {
	    result = NULL;
	}
	Tcl_DStringFree(&envStr);
    }
    Tcl_MutexUnlock(&envMutex);
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * EnvTraceProc --
 *
 *	This procedure is invoked whenever an environment variable
 *	is read, modified or deleted.  It propagates the change to the global
 *	"environ" array.
 *
 * Results:
 *	Always returns NULL to indicate success.
 *
 * Side effects:
 *	Environment variable changes get propagated.  If the whole
 *	"env" array is deleted, then we stop managing things for
 *	this interpreter (usually this happens because the whole
 *	interpreter is being deleted).
 *
 *----------------------------------------------------------------------
 */

	/* ARGSUSED */
static char *
EnvTraceProc(clientData, interp, name1, name2, flags)
    ClientData clientData;	/* Not used. */
    Tcl_Interp *interp;		/* Interpreter whose "env" variable is
				 * being modified. */
    char *name1;		/* Better be "env". */
    char *name2;		/* Name of variable being modified, or NULL
				 * if whole array is being deleted (UTF-8). */
    int flags;			/* Indicates what's happening. */
{
    /*
     * For array traces, let TclSetupEnv do all the work.
     */

    if (flags & TCL_TRACE_ARRAY) {
	TclSetupEnv(interp);
	return NULL;
    }

    /*
     * If name2 is NULL, then return and do nothing.
     */
     
    if (name2 == NULL) {
	return NULL;
    }

    /*
     * If a value is being set, call TclSetEnv to do all of the work.
     */

    if (flags & TCL_TRACE_WRITES) {
	char *value;
	
	value = Tcl_GetVar2(interp, "env", name2, TCL_GLOBAL_ONLY);
	TclSetEnv(name2, value);
    }

    /*
     * If a value is being read, call TclGetEnv to do all of the work.
     */

    if (flags & TCL_TRACE_READS) {
	Tcl_DString valueString;
	char *value;

	value = TclGetEnv(name2, &valueString);
	if (value == NULL) {
	    return "no such variable";
	}
	Tcl_SetVar2(interp, name1, name2, value, 0);
	Tcl_DStringFree(&valueString);
    }

    /*
     * For unset traces, let TclUnsetEnv do all the work.
     */

    if (flags & TCL_TRACE_UNSETS) {
	TclUnsetEnv(name2);
    }
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * ReplaceString --
 *
 *	Replace one string with another in the environment variable
 *	cache.  The cache keeps track of all of the environment
 *	variables that Tcl has modified so they can be freed later.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May free the old string.
 *
 *----------------------------------------------------------------------
 */

static void
ReplaceString(oldStr, newStr)
    CONST char *oldStr;		/* Old environment string. */
    char *newStr;		/* New environment string. */
{
    int i;
    char **newCache;

    /*
     * Check to see if the old value was allocated by Tcl.  If so,
     * it needs to be deallocated to avoid memory leaks.  Note that this
     * algorithm is O(n), not O(1).  This will result in n-squared behavior
     * if lots of environment changes are being made.
     */

    for (i = 0; i < cacheSize; i++) {
	if ((environCache[i] == oldStr) || (environCache[i] == NULL)) {
	    break;
	}
    }
    if (i < cacheSize) {
	/*
	 * Replace or delete the old value.
	 */

	if (environCache[i]) {
	    ckfree(environCache[i]);
	}
	    
	if (newStr) {
	    environCache[i] = newStr;
	} else {
	    for (; i < cacheSize-1; i++) {
		environCache[i] = environCache[i+1];
	    }
	    environCache[cacheSize-1] = NULL;
	}
    } else {	
        int allocatedSize = (cacheSize + 5) * sizeof(char *);

	/*
	 * We need to grow the cache in order to hold the new string.
	 */

	newCache = (char **) ckalloc((unsigned) allocatedSize);
        (VOID *) memset(newCache, (int) 0, (size_t) allocatedSize);
        
	if (environCache) {
	    memcpy((VOID *) newCache, (VOID *) environCache,
		    (size_t) (cacheSize * sizeof(char*)));
	    ckfree((char *) environCache);
	}
	environCache = newCache;
	environCache[cacheSize] = (char *) newStr;
	environCache[cacheSize+1] = NULL;
	cacheSize += 5;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclFinalizeEnvironment --
 *
 *	This function releases any storage allocated by this module
 *	that isn't still in use by the global environment.  Any
 *	strings that are still in the environment will be leaked.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May deallocate storage.
 *
 *----------------------------------------------------------------------
 */

void
TclFinalizeEnvironment()
{
    /*
     * For now we just deallocate the cache array and none of the environment
     * strings.  This may leak more memory that strictly necessary, since some
     * of the strings may no longer be in the environment.  However,
     * determining which ones are ok to delete is n-squared, and is pretty
     * unlikely, so we don't bother.
     */

    if (environCache) {
	ckfree((char *) environCache);
	environCache = NULL;
	cacheSize    = 0;
#ifndef USE_PUTENV
	environSize  = 0;
#endif
    }
}
