os2: initial implementation for Darwin&BSDs, process API is only thing incomplete

core/os/os2/env_posix.odin

@@ -0,0 +1,78 @@
+//+private
+//+build darwin, netbsd, freebsd, openbsd
+package os2
+
+import "base:runtime"
+
+import "core:strings"
+import "core:sys/posix"
+
+_lookup_env :: proc(key: string, allocator: runtime.Allocator) -> (value: string, found: bool) {
+	if key == "" {
+		return
+	}
+
+	assert(!is_temp(allocator))
+	TEMP_ALLOCATOR_GUARD()
+
+	ckey := strings.clone_to_cstring(key, temp_allocator())
+	cval := posix.getenv(ckey)
+	if cval == nil {
+		return
+	}
+
+	found = true
+	value = strings.clone(string(cval), allocator) // NOTE(laytan): what if allocation fails?
+
+	return
+}
+
+_set_env :: proc(key, value: string) -> (ok: bool) {
+	TEMP_ALLOCATOR_GUARD()
+
+	ckey := strings.clone_to_cstring(key, temp_allocator())
+	cval := strings.clone_to_cstring(key, temp_allocator())
+
+	ok = posix.setenv(ckey, cval, true) == .OK
+	return
+}
+
+_unset_env :: proc(key: string) -> (ok: bool) {
+	TEMP_ALLOCATOR_GUARD()
+
+	ckey := strings.clone_to_cstring(key, temp_allocator())
+
+	ok = posix.unsetenv(ckey) == .OK
+	return
+}
+
+// NOTE(laytan): clearing the env is weird, why would you ever do that?
+
+_clear_env :: proc() {
+	for i, entry := 0, posix.environ[0]; entry != nil; i, entry = i+1, posix.environ[i] {
+		key := strings.truncate_to_byte(string(entry), '=')
+		_unset_env(key)
+	}
+}
+
+_environ :: proc(allocator: runtime.Allocator) -> (environ: []string) {
+	n := 0	
+	for entry := posix.environ[0]; entry != nil; n, entry = n+1, posix.environ[n] {}
+
+	err: runtime.Allocator_Error
+	if environ, err = make([]string, n, allocator); err != nil {
+		// NOTE(laytan): is the environment empty or did allocation fail, how does the user know?
+		return
+	}
+
+	for i, entry := 0, posix.environ[0]; entry != nil; i, entry = i+1, posix.environ[i] {
+		if environ[i], err = strings.clone(string(entry), allocator); err != nil {
+			// NOTE(laytan): is the entire environment returned or did allocation fail, how does the user know?
+			return
+		}
+	}
+
+	return
+}
+
+