spa: add a new string helper with spa_strtol()

Most of the time when we convert a string to an integer we only care about
success. Let's wrap this with a helper function that sets the value to the
result and returns true on success.

spa/include/spa/utils/string.h

@@ -0,0 +1,67 @@
+/* Simple Plugin API
+ *
+ * Copyright © 2021 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef SPA_UTILS_STRING_H
+#define SPA_UTILS_STRING_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdbool.h>
+#include <errno.h>
+
+/**
+ * Convert \a str to an int32_t with the given \a base and store the
+ * result in \a val.
+ *
+ * On failure, the value of \a val is undefined.
+ *
+ * \return true on success, false otherwise
+ */
+static inline bool spa_atoi32(const char *str, int32_t *val, int base)
+{
+	char *endptr;
+	long v;
+
+	if (!str || *str =='\0')
+		return false;
+
+	errno = 0;
+	v = strtol(str, &endptr, base);
+	if (errno != 0 || *endptr != '\0')
+		return false;
+
+	if (v != (int32_t)v)
+		return false;
+
+	*val = v;
+	return true;
+}
+
+#ifdef __cplusplus
+}  /* extern "C" */
+#endif
+
+#endif /* SPA_UTILS_STRING_H */