Function make_environment_block

compat/mingw.c:1786–1857

* Build an environment block combining the inherited environment * merged with the given list of settings. * * Values of the form "KEY=VALUE" in deltaenv override inherited values. * Values of the form "KEY" in deltaenv delete inherited values. * * Multiple entries in deltaenv for the same key are explicitly allowed. * * We return a contiguous block of UNICODE strings with a final trailing

 * zero word.
 */
static wchar_t *make_environment_block(char **deltaenv)
{
	wchar_t *wenv = GetEnvironmentStringsW(), *wdeltaenv, *result, *p;
	size_t wlen, s, delta_size, size;

	wchar_t **array = NULL;
	size_t alloc = 0, nr = 0, i;

	size = 1; /* for extra NUL at the end */

	/* If there is no deltaenv to apply, simply return a copy. */
	if (!deltaenv || !*deltaenv) {
		for (p = wenv; p && *p; ) {
			size_t s = wcslen(p) + 1;
			size += s;
			p += s;
		}

		DUP_ARRAY(result, wenv, size);
		FreeEnvironmentStringsW(wenv);
		return result;
	}

	/*
	 * If there is a deltaenv, let's accumulate all keys into `array`,
	 * sort them using the stable git_stable_qsort() and then copy,
	 * skipping duplicate keys
	 */
	for (p = wenv; p && *p; ) {
		ALLOC_GROW(array, nr + 1, alloc);
		s = wcslen(p) + 1;
		array[nr++] = p;
		p += s;
		size += s;
	}

	/* (over-)assess size needed for wchar version of deltaenv */
	for (delta_size = 0, i = 0; deltaenv[i]; i++)
		delta_size += strlen(deltaenv[i]) * 2 + 1;
	ALLOC_ARRAY(wdeltaenv, delta_size);

	/* convert the deltaenv, appending to array */
	for (i = 0, p = wdeltaenv; deltaenv[i]; i++) {
		ALLOC_GROW(array, nr + 1, alloc);
		wlen = xutftowcs(p, deltaenv[i], wdeltaenv + delta_size - p);
		array[nr++] = p;
		p += wlen + 1;
	}

	git_stable_qsort(array, nr, sizeof(*array), wenvcmp);
	ALLOC_ARRAY(result, size + delta_size);

	for (p = result, i = 0; i < nr; i++) {
		/* Skip any duplicate keys; last one wins */
		while (i + 1 < nr && !wenvcmp(array + i, array + i + 1))
		       i++;

		/* Skip "to delete" entry */