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#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "qemu-queue.h"
#include "envlist.h"

struct envlist_entry {
const char *ev_var; /* actual env value */
QLIST_ENTRY(envlist_entry) ev_link;
};

struct envlist {
QLIST_HEAD(, envlist_entry) el_entries; /* actual entries */
size_t el_count; /* number of entries */
};

static int envlist_parse(envlist_t *envlist,
    const char *env, int (*)(envlist_t *, const char *));

/*
* Allocates new envlist and returns pointer to that or
* NULL in case of error.
*/
envlist_t *
envlist_create(void)
{
envlist_t *envlist;

if ((envlist = malloc(sizeof (*envlist))) == NULL)
return (NULL);

QLIST_INIT(&envlist->el_entries);
envlist->el_count = 0;

return (envlist);
}

/*
* Releases given envlist and its entries.
*/
void
envlist_free(envlist_t *envlist)
{
struct envlist_entry *entry;

assert(envlist != NULL);

while (envlist->el_entries.lh_first != NULL) {
entry = envlist->el_entries.lh_first;
QLIST_REMOVE(entry, ev_link);

free((char *)entry->ev_var);
free(entry);
}
free(envlist);
}

/*
* Parses comma separated list of set/modify environment
* variable entries and updates given enlist accordingly.
*
* For example:
* envlist_parse(el, "HOME=foo,SHELL=/bin/sh");
*
* inserts/sets environment variables HOME and SHELL.
*
* Returns 0 on success, errno otherwise.
*/
int
envlist_parse_set(envlist_t *envlist, const char *env)
{
return (envlist_parse(envlist, env, &envlist_setenv));
}

/*
* Parses comma separated list of unset environment variable
* entries and removes given variables from given envlist.
*
* Returns 0 on success, errno otherwise.
*/
int
envlist_parse_unset(envlist_t *envlist, const char *env)
{
return (envlist_parse(envlist, env, &envlist_unsetenv));
}

/*
* Parses comma separated list of set, modify or unset entries
* and calls given callback for each entry.
*
* Returns 0 in case of success, errno otherwise.
*/
static int
envlist_parse(envlist_t *envlist, const char *env,
    int (*callback)(envlist_t *, const char *))
{
char *tmpenv, *envvar;
char *envsave = NULL;

assert(callback != NULL);

if ((envlist == NULL) || (env == NULL))
return (EINVAL);

/*
* We need to make temporary copy of the env string
* as strtok_r(3) modifies it while it tokenizes.
*/
if ((tmpenv = strdup(env)) == NULL)
return (errno);

envvar = strtok_r(tmpenv, ",", &envsave);
while (envvar != NULL) {
if ((*callback)(envlist, envvar) != 0) {
free(tmpenv);
return (errno);
}
envvar = strtok_r(NULL, ",", &envsave);
}

free(tmpenv);
return (0);
}

/*
* Sets environment value to envlist in similar manner
* than putenv(3).
*
* Returns 0 in success, errno otherwise.
*/
int
envlist_setenv(envlist_t *envlist, const char *env)
{
struct envlist_entry *entry = NULL;
const char *eq_sign;
size_t envname_len;

if ((envlist == NULL) || (env == NULL))
return (EINVAL);

/* find out first equals sign in given env */
if ((eq_sign = strchr(env, '=')) == NULL)
return (EINVAL);
envname_len = eq_sign - env + 1;

/*
* If there already exists variable with given name
* we remove and release it before allocating a whole
* new entry.
*/
for (entry = envlist->el_entries.lh_first; entry != NULL;
entry = entry->ev_link.le_next) {
if (strncmp(entry->ev_var, env, envname_len) == 0)
break;
}

if (entry != NULL) {
QLIST_REMOVE(entry, ev_link);
free((char *)entry->ev_var);
free(entry);
} else {
envlist->el_count++;
}

if ((entry = malloc(sizeof (*entry))) == NULL)
return (errno);
if ((entry->ev_var = strdup(env)) == NULL) {
free(entry);
return (errno);
}
QLIST_INSERT_HEAD(&envlist->el_entries, entry, ev_link);

return (0);
}

/*
* Removes given env value from envlist in similar manner
* than unsetenv(3). Returns 0 in success, errno otherwise.
*/
int
envlist_unsetenv(envlist_t *envlist, const char *env)
{
struct envlist_entry *entry;
size_t envname_len;

if ((envlist == NULL) || (env == NULL))
return (EINVAL);

/* env is not allowed to contain '=' */
if (strchr(env, '=') != NULL)
return (EINVAL);

/*
* Find out the requested entry and remove
* it from the list.
*/
envname_len = strlen(env);
for (entry = envlist->el_entries.lh_first; entry != NULL;
entry = entry->ev_link.le_next) {
if (strncmp(entry->ev_var, env, envname_len) == 0)
break;
}
if (entry != NULL) {
QLIST_REMOVE(entry, ev_link);
free((char *)entry->ev_var);
free(entry);

envlist->el_count--;
}
return (0);
}

/*
* Returns given envlist as array of strings (in same form that
* global variable environ is). Caller must free returned memory
* by calling free(3) for each element and for the array. Returned
* array and given envlist are not related (no common references).
*
* If caller provides count pointer, number of items in array is
* stored there. In case of error, NULL is returned and no memory
* is allocated.
*/
char **
envlist_to_environ(const envlist_t *envlist, size_t *count)
{
struct envlist_entry *entry;
char **env, **penv;

penv = env = malloc((envlist->el_count + 1) * sizeof (char *));
if (env == NULL)
return (NULL);

for (entry = envlist->el_entries.lh_first; entry != NULL;
entry = entry->ev_link.le_next) {
*(penv++) = strdup(entry->ev_var);
}
*penv = NULL; /* NULL terminate the list */

if (count != NULL)
*count = envlist->el_count;

return (env);
}
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