/**************************************************************************
*
* FILE envvar.c
* MODULE OF fvwm
*
* DESCRIPTION Routines to expand environment-variables into strings.
* Will understand both $ENV and ${ENV} -type variables.
*
* WRITTEN BY Sverre H. Huseby
* sverrehu@ifi.uio.no
*
* CREATED 1995/10/3
*
**************************************************************************/
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <fvwm/fvwmlib.h>
#ifndef NULL
#define NULL 0
#endif
/**************************************************************************
* *
* P R I V A T E D A T A *
* *
**************************************************************************/
/**************************************************************************
* *
* P R I V A T E F U N C T I O N S *
* *
**************************************************************************/
/*-------------------------------------------------------------------------
*
* NAME strDel
*
* FUNCTION Delete characters from a string.
*
* INPUT s the string to delete characters from.
* idx index of first character to delete.
* n number of characters to delete.
*
* OUTPUT s string with characters deleted.
*
* DESCRIPTION Deletes characters from a string by moving following
* characters back.
*
*/
static void strDel(char *s, int idx, int n)
{
int l;
char *p;
if (idx >= (l = strlen(s)))
return;
if (idx + n > l)
n = l - idx;
s += idx;
p = s + n;
do {
*s++ = *p;
} while (*p++);
}
/*-------------------------------------------------------------------------
*
* NAME strIns
*
* FUNCTION Insert a string into a string.
*
* INPUT s the string to insert into.
* ins the string to insert.
* idx index of where to insert the string.
* maxstrlen max length of s, including '\0'.
*
* OUTPUT s string with characters inserted.
*
* DESCRIPTION The insertion will be done even if the string gets to
* long, but characters will be sacrificed at the end of s.
* The string is always '\0'-terminated.
*
*/
static void strIns(char *s, const char *ins, int idx, int maxstrlen)
{
int l, li, move;
char *p1, *p2;
if (idx > (l = strlen(s)))
idx = l;
li = strlen(ins);
move = l - idx + 2; /* include '\0' in move */
p1 = s + l;
p2 = p1 + li;
while (p2 >= s + maxstrlen) {
--p1;
--p2;
--move;
}
while (move-- > 0)
*p2-- = *p1--;
p1 = s + idx;
if (idx + li >= maxstrlen)
li = maxstrlen - idx - 1;
while (li--)
*p1++ = *ins++;
s[maxstrlen - 1] = '\0';
}
/*-------------------------------------------------------------------------
*
* NAME findEnvVar
*
* FUNCTION Find first environment variable in a string.
*
* INPUT s the string to scan.
*
* OUTPUT len length of variable, including $ and { }.
*
* RETURNS Pointer to the $ that introduces the variable, or NULL
* if no variable is found.
*
* DESCRIPTION Searches for matches like $NAME and ${NAME}, where NAME is
* a sequence of characters, digits and underscores, of which
* the first can not be a digit.
*
* NOTE This function will only return `legal' variables. There
* may be $'s in the string that are not followed by what
* is considered a legal variable name introducer. Such
* occurrences are skipped.
*
*/
static char *findEnvVar(const char *s, int *len)
{
int brace = 0;
char *ret = NULL;
const char *next;
if (!s)
return NULL;
while (*s) {
next = s + 1;
if (*s == '$' && (isalpha(*next) || *next == '_' || *next == '{')) {
ret = (char *) s++;
if (*s == '{') {
brace = 1;
++s;
}
while (*s && (isalnum(*s) || *s == '_'))
++s;
*len = s - ret;
if (brace) {
if (*s == '}') {
++*len;
break;
}
ret = NULL;
} else
break;
}
++s;
}
return ret;
}
/*-------------------------------------------------------------------------
*
* NAME getEnv
*
* FUNCTION Look up environment variable.
*
* INPUT name name of environment variable to look up. This
* may include $ and { }.
*
* RETURNS The variable contents, or "" if not found.
*
*/
static const char *getEnv(const char *name)
{
static char *empty = "";
char *ret, *tmp, *p, *p2;
if ((tmp = strdup(name)) == NULL)
return empty; /* better than no test at all. */
p = tmp;
if (*p == '$')
++p;
if (*p == '{') {
++p;
if ((p2 = strchr(p, '}')) != NULL)
*p2 = '\0';
}
if ((ret = getenv(p)) == NULL)
ret = empty;
free(tmp);
return ret;
}
/**************************************************************************
* *
* P U B L I C F U N C T I O N S *
* *
**************************************************************************/
/*-------------------------------------------------------------------------
*
* NAME envExpand
*
* FUNCTION Expand environment variables in a string.
*
* SYNOPSIS #include "envvar.h"
* int envExpand(char *s, int maxstrlen);
*
* INPUT s string to expand environment variables in.
* maxstrlen max length of string, including '\0'.
*
* OUTPUT s the string with environment variables expanded.
*
* RETURNS Number of changes done.
*
* NOTES A non-existing variable is substituted with the empty
* string.
*
*/
int envExpand(char *s, int maxstrlen)
{
char *var, *s2, save;
const char *env;
int len, ret = 0;
s2 = s;
while ((var = findEnvVar(s2, &len)) != NULL) {
++ret;
save = var[len];
var[len] = '\0';
env = getEnv(var);
var[len] = save;
strDel(s, var - s, len);
strIns(s, env, var - s, maxstrlen);
s2 = var + strlen(env);
}
return ret;
}
/*-------------------------------------------------------------------------
*
* NAME envDupExpand
*
* FUNCTION Expand environment variables into a new string.
*
* SYNOPSIS #include "envvar.h"
* char *envDupExpand(const char *s, int extra);
*
* INPUT s string to expand environment variables in.
* extra number of extra bytes to allocate in the
* string, in addition to the string contents
* and the terminating '\0'.
*
* RETURNS A dynamically allocated string with environment
* variables expanded.
* Use free() to deallocate the buffer when it is no
* longer needed.
* NULL is returned if there is not enough memory.
*
* NOTES A non-existing variable is substituted with the empty
* string.
*
*/
char *envDupExpand(const char *s, int extra)
{
char *var, *ret, save;
const char *env, *s2;
int len, slen, elen, bufflen;
/*
* calculate length needed.
*/
s2 = s;
slen = strlen(s);
bufflen = slen + 1 + extra;
while ((var = findEnvVar(s2, &len)) != NULL) {
save = var[len];
var[len] = '\0';
env = getEnv(var);
var[len] = save;
elen = strlen(env);
/* need to make a buffer the maximum possible size, else we
* may get trouble while expanding. */
bufflen += len > elen ? len : elen;
s2 = var + len;
}
if (bufflen < slen + 1)
bufflen = slen + 1;
ret = safemalloc(bufflen);
/*
* now do the real expansion.
*/
strcpy(ret, s);
envExpand(ret, bufflen - extra);
return ret;
}
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