esp-idf/tools/kconfig/expand_env.c

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C
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#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <assert.h>
#include <ctype.h>
#include <stdbool.h>
#include "expand_env.h"
static bool allowed_env_var_name(char c)
{
return c != '\0' &&
!isblank(c) &&
!iscntrl(c) &&
c != '/' &&
c != '\\' &&
c != '=' &&
c != '$';
}
#define MAX_LEN (128 * 1024) /* Longest a result can expand to */
/* Very basic expansion that looks for variable references like $NAME and expands them
*
*/
char *expand_environment(const char *input, const char *src_name, int src_line_no)
{
char *result = malloc(MAX_LEN);
char *out = result;
const char *in = input;
while (*in != '\0') {
// check for buffer overflow
if (out >= result + MAX_LEN - 1) {
goto too_long;
}
if (*in != '$') {
// not part of an environment variable name, copy directly
*out++ = *in++;
continue;
}
// *in points to start of an environment variable reference
in++;
const char *env_start = in;
while (allowed_env_var_name(*in)) { // scan to the end of the name
in++;
}
size_t env_len = in - env_start;
// make a buffer to hold the environment variable name
//
// strndup is not available on mingw32, apparently.
char *env_name = calloc(1, env_len + 1);
assert(env_name != NULL);
strncpy(env_name, env_start, env_len);
const char *value = getenv(env_name);
if (value == NULL || strlen(value) == 0) {
printf("%s:%d: undefined environment variable \"%s\"\n",
src_name, src_line_no, env_name);
exit(1);
}
free(env_name);
if (out + strlen(value) >= result + MAX_LEN - 1) {
goto too_long;
}
strcpy(out, value); // append the value to the result (range checked in previous statement)
out += strlen(value);
}
*out = '\0'; // null terminate the result string
return result;
too_long:
printf("%s:%d: Expansion is longer than %d bytes\n",
src_name, src_line_no, MAX_LEN);
free(result);
exit(1);
}
void free_expanded(char *expanded)
{
free(expanded);
}