[micropolis] / src / tcl / tclenv.c

/* 
 * tclEnv.c --
 *
 *      Tcl support for environment variables, including a setenv_tcl
 *      procedure.
 *
 * Copyright 1991 Regents of the University of California
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that this copyright
 * notice appears in all copies.  The University of California
 * makes no representations about the suitability of this
 * software for any purpose.  It is provided "as is" without
 * express or implied warranty.
 */

#ifndef lint
static char rcsid[] = "$Header: /user6/ouster/tcl/RCS/tclEnv.c,v 1.7 91/09/23 11:22:21 ouster Exp $ SPRITE (Berkeley)";
#endif /* not lint */

#include "tclint.h"
#include "tclunix.h"

/*
 * The structure below is used to keep track of all of the interpereters
 * for which we're managing the "env" array.  It's needed so that they
 * can all be updated whenever an environment variable is changed
 * anywhere.
 */

typedef struct EnvInterp {
    Tcl_Interp *interp;         /* Interpreter for which we're managing
                                 * the env array. */
    struct EnvInterp *nextPtr;  /* Next in list of all such interpreters,
                                 * or zero. */
} EnvInterp;

static EnvInterp *firstInterpPtr;
                                /* First in list of all managed interpreters,
                                 * or NULL if none. */

static int environSize = 0;     /* Non-zero means that the all of the
                                 * environ-related information is malloc-ed
                                 * and the environ array itself 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. */

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

static void             EnvInit _ANSI_ARGS_((void));
static char *           EnvTraceProc _ANSI_ARGS_((ClientData clientData,
                            Tcl_Interp *interp, char *name1, char *name2,
                            int flags));
static int              FindVariable _ANSI_ARGS_((char *name, int *lengthPtr));

void                    setenv_tcl _ANSI_ARGS_((char *name, char *value));
int                     unsetenv_tcl _ANSI_ARGS_((char *name));

\f
/*
 *----------------------------------------------------------------------
 *
 * 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 Tcl_SetupEnv, 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. */
{
    EnvInterp *eiPtr;
    int i;

    /*
     * First, initialize our environment-related information, if
     * necessary.
     */

    if (environSize == 0) {
        EnvInit();
    }

    /*
     * Next, add the interpreter to the list of those that we manage.
     */

    eiPtr = (EnvInterp *) ckalloc(sizeof(EnvInterp));
    eiPtr->interp = interp;
    eiPtr->nextPtr = firstInterpPtr;
    firstInterpPtr = eiPtr;

    /*
     * Store the environment variable values into the interpreter's
     * "env" array, and arrange for us to be notified on future
     * writes and unsets to that array.
     */

    (void) Tcl_UnsetVar2(interp, "env", (char *) NULL, TCL_GLOBAL_ONLY);
    for (i = 0; ; i++) {
        char *p, *p2;

        p = environ[i];
        if (p == NULL) {
            break;
        }
        for (p2 = p; *p2 != '='; p2++) {
            /* Empty loop body. */
        }
        *p2 = 0;
        (void) Tcl_SetVar2(interp, "env", p, p2+1, TCL_GLOBAL_ONLY);
        *p2 = '=';
    }
    Tcl_TraceVar2(interp, "env", (char *) NULL,
            TCL_GLOBAL_ONLY | TCL_TRACE_WRITES | TCL_TRACE_UNSETS,
            EnvTraceProc, (ClientData) NULL);
}
\f
/*
 *----------------------------------------------------------------------
 *
 * FindVariable --
 *
 *      Locate the entry in environ for a given name.
 *
 * Results:
 *      The return value is the index in environ of an entry with the
 *      name "name", or -1 if there is no such entry.   The integer at
 *      *lengthPtr is filled in with the length of name (if a matching
 *      entry is found) or the length of the environ array (if no matching
 *      entry is found).
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

static int
FindVariable(name, lengthPtr)
    char *name;                 /* Name of desired environment variable. */
    int *lengthPtr;             /* Used to return length of name (for
                                 * successful searches) or number of non-NULL
                                 * entries in environ (for unsuccessful
                                 * searches). */
{
    int i;
    register char *p1, *p2;

    for (i = 0, p1 = environ[i]; p1 != NULL; i++, p1 = environ[i]) {
        for (p2 = name; *p2 == *p1; p1++, p2++) {
            /* NULL loop body. */
        }
        if ((*p1 == '=') && (*p2 == '\0')) {
            *lengthPtr = p2-name;
            return i;
        }
    }
    *lengthPtr = i;
    return -1;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * setenv_tcl --
 *
 *      Set an environment variable, replacing an existing value
 *      or creating a new variable if there doesn't exist a variable
 *      by the given name.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The environ array gets updated, as do all of the interpreters
 *      that we manage.
 *
 *----------------------------------------------------------------------
 */

void
setenv_tcl(name, value)
    char *name;                 /* Name of variable whose value is to be
                                 * set. */
    char *value;                /* New value for variable. */
{
    int index, length, nameLength;
    char *p;
    EnvInterp *eiPtr;

    if (environSize == 0) {
        EnvInit();
    }

    /*
     * 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.
     */

    index = FindVariable((char *)name, &length);
    if (index == -1) {
        if ((length+2) > environSize) {
            char **newEnviron;

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

    /*
     * Create a new entry and enter it into the table.
     */

    p = (char *) ckalloc((unsigned) (nameLength + strlen(value) + 2));
    environ[index] = p;
    strcpy(p, name);
    p += nameLength;
    *p = '=';
    strcpy(p+1, value);

    /*
     * Update all of the interpreters.
     */

    for (eiPtr= firstInterpPtr; eiPtr != NULL; eiPtr = eiPtr->nextPtr) {
        (void) Tcl_SetVar2(eiPtr->interp, "env", (char *)name, p+1, TCL_GLOBAL_ONLY);
    }
}
\f
/*
 *----------------------------------------------------------------------
 *
 * unsetenv_tcl --
 *
 *      Remove an environment variable, updating the "env" arrays
 *      in all interpreters managed by us.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Interpreters are updated, as is environ.
 *
 *----------------------------------------------------------------------
 */

int
unsetenv_tcl(name)
    char *name;                 /* Name of variable to remove. */
{
    int index, dummy;
    char **envPtr;
    EnvInterp *eiPtr;

    if (environSize == 0) {
        EnvInit();
    }

    /*
     * Update the environ array.
     */

    index = FindVariable((char *)name, &dummy);
    if (index == -1) {
        return;
    }
    ckfree(environ[index]);
    for (envPtr = environ+index+1; ; envPtr++) {
        envPtr[-1] = *envPtr;
        if (*envPtr == NULL) {
            break;
       }
    }

    /*
     * Update all of the interpreters.
     */

    for (eiPtr = firstInterpPtr; eiPtr != NULL; eiPtr = eiPtr->nextPtr) {
        (void) Tcl_UnsetVar2(eiPtr->interp, "env", (char *)name, TCL_GLOBAL_ONLY);
    }
}
\f
/*
 *----------------------------------------------------------------------
 *
 * EnvTraceProc --
 *
 *      This procedure is invoked whenever an environment variable
 *      is modified or deleted.  It propagates the change to the
 *      "environ" array and to any other interpreters for whom
 *      we're managing an "env" 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. */
    int flags;                  /* Indicates what's happening. */
{
    /*
     * First see if the whole "env" variable is being deleted.  If
     * so, just forget about this interpreter.
     */

    if (name2 == NULL) {
        register EnvInterp *eiPtr, *prevPtr;

        if ((flags & (TCL_TRACE_UNSETS|TCL_TRACE_DESTROYED))
                != (TCL_TRACE_UNSETS|TCL_TRACE_DESTROYED)) {
            panic("EnvTraceProc called with confusing arguments");
        }
        eiPtr = firstInterpPtr;
        if (eiPtr->interp == interp) {
            firstInterpPtr = eiPtr->nextPtr;
        } else {
            for (prevPtr = eiPtr, eiPtr = eiPtr->nextPtr; ;
                    prevPtr = eiPtr, eiPtr = eiPtr->nextPtr) {
                if (eiPtr == NULL) {
                    panic("EnvTraceProc couldn't find interpreter");
                }
                if (eiPtr->interp == interp) {
                    prevPtr->nextPtr = eiPtr->nextPtr;
                    break;
                }
            }
        }
        ckfree((char *) eiPtr);
        return NULL;
    }

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

    if (flags & TCL_TRACE_WRITES) {
        setenv_tcl(name2, Tcl_GetVar2(interp, "env", name2, TCL_GLOBAL_ONLY));
    }

    if (flags & TCL_TRACE_UNSETS) {
        unsetenv_tcl(name2);
    }
    return NULL;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * EnvInit --
 *
 *      This procedure is called to initialize our management
 *      of the environ array.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Environ gets copied to malloc-ed storage, so that in
 *      the future we don't have to worry about which entries
 *      are malloc-ed and which are static.
 *
 *----------------------------------------------------------------------
 */

static void
EnvInit()
{
    char **newEnviron;
    int i, length;

    if (environSize != 0) {
        return;
    }
    for (length = 0; environ[length] != NULL; length++) {
        /* Empty loop body. */
    }
    environSize = length+5;
    newEnviron = (char **) ckalloc((unsigned)
                (environSize * sizeof(char *)));
    for (i = 0; i < length; i++) {
        newEnviron[i] = (char *) ckalloc((unsigned) (strlen(environ[i]) + 1));
        strcpy(newEnviron[i], environ[i]);
    }
    newEnviron[length] = NULL;
    environ = newEnviron;
}