From 2ec589ec1968001fcdf0cee66ae69e8b09c1e9ba Mon Sep 17 00:00:00 2001
From: Joel Rosdahl <joel@rosdahl.net>
Date: Sun, 3 Apr 2011 21:51:10 +0200
Subject: [PATCH] Add subst_env_in_string function

---
 ccache.h         |  1 +
 test/test_util.c | 38 +++++++++++++++++++++++
 util.c           | 80 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 119 insertions(+)

diff --git a/ccache.h b/ccache.h
index 64baf7348..59c05f7bb 100644
--- a/ccache.h
+++ b/ccache.h
@@ -152,6 +152,7 @@ char *x_readlink(const char *path);
 #endif
 bool read_file(const char *path, size_t size_hint, char **data, size_t *size);
 char *read_text_file(const char *path, size_t size_hint);
+char *subst_env_in_string(const char *str, char **errmsg);
 
 /* ------------------------------------------------------------------------- */
 /* stats.c */
diff --git a/test/test_util.c b/test/test_util.c
index a92d55c2c..435720558 100644
--- a/test/test_util.c
+++ b/test/test_util.c
@@ -56,4 +56,42 @@ TEST(format_hash_as_string)
 	                   format_hash_as_string(hash, 12345));
 }
 
+TEST(subst_env_in_string)
+{
+	char *errmsg;
+	const char *shell = getenv("SHELL");
+
+	errmsg = "";
+	CHECK_STR_EQ_FREE2(shell,
+	                   subst_env_in_string("$SHELL", &errmsg));
+	CHECK(!errmsg);
+
+	errmsg = "";
+	CHECK_STR_EQ_FREE2("$",
+	                   subst_env_in_string("$", &errmsg));
+	CHECK(!errmsg);
+
+	errmsg = "";
+	CHECK_STR_EQ_FREE12(format("%s %s:%s", shell, shell, shell),
+	                    subst_env_in_string("$SHELL $SHELL:$SHELL", &errmsg));
+	CHECK(!errmsg);
+
+	errmsg = "";
+	CHECK_STR_EQ_FREE12(format("x%s", shell),
+	                    subst_env_in_string("x$SHELL", &errmsg));
+	CHECK(!errmsg);
+
+	errmsg = "";
+	CHECK_STR_EQ_FREE12(format("%sx", shell),
+	                    subst_env_in_string("${SHELL}x", &errmsg));
+	CHECK(!errmsg);
+
+	CHECK(!subst_env_in_string("$surelydoesntexist", &errmsg));
+	CHECK_STR_EQ_FREE2("environment variable \"surelydoesntexist\" not set",
+	                   errmsg);
+
+	CHECK(!subst_env_in_string("${SHELL", &errmsg));
+	CHECK_STR_EQ_FREE2("syntax error: missing '}' after \"SHELL\"", errmsg);
+}
+
 TEST_SUITE_END
diff --git a/util.c b/util.c
index d64cd2320..1b7c950ce 100644
--- a/util.c
+++ b/util.c
@@ -1270,3 +1270,83 @@ read_text_file(const char *path, size_t size_hint)
 		return NULL;
 	}
 }
+
+static bool
+expand_variable(const char **str, char **result, char **errmsg)
+{
+	bool curly;
+	const char *p, *q;
+	char *name;
+	const char *value;
+
+	assert(**str == '$');
+	p = *str + 1;
+	if (*p == '{') {
+		curly = true;
+		++p;
+	} else {
+		curly = false;
+	}
+	q = p;
+	while (isalnum(*q) || *q == '_') {
+		++q;
+	}
+	if (curly) {
+		if (*q != '}') {
+			*errmsg = format("syntax error: missing '}' after \"%s\"", p);
+			return NULL;
+		}
+	}
+
+	if (q == p) {
+		/* Special case: don't consider a single $ the start of a variable. */
+		x_asprintf2(result, "%s$", *result);
+		return true;
+	}
+
+	name = x_strndup(p, q - p);
+	value = getenv(name);
+	if (!value) {
+		*errmsg = format("environment variable \"%s\" not set", name);
+		return false;
+	}
+	x_asprintf2(result, "%s%s", *result, value);
+	if (!curly) {
+		--q;
+	}
+	*str = q;
+	return true;
+}
+
+/*
+ * Substitute all instances of $VAR or ${VAR}, where VAR is an environment
+ * variable, in a string. Caller frees. If one of the environment variables
+ * doesn't exist, NULL will be returned and *errmsg will be an appropriate
+ * error message (caller frees).
+ */
+char *
+subst_env_in_string(const char *str, char **errmsg)
+{
+	const char *p; /* Interval start. */
+	const char *q; /* Interval end. */
+	char *result;
+
+	assert(errmsg);
+	*errmsg = NULL;
+
+	result = x_strdup("");
+	p = str;
+	q = str;
+	for (q = str; *q; ++q) {
+		if (*q == '$') {
+			x_asprintf2(&result, "%s%.*s", result, (int)(q - p), p);
+			if (!expand_variable(&q, &result, errmsg)) {
+				free(result);
+				return NULL;
+			}
+			p = q + 1;
+		}
+	}
+	x_asprintf2(&result, "%s%.*s", result, (int)(q - p), p);
+	return result;
+}
-- 
2.47.3