std/os: add the LookupEnv function

std/os/file.jule

@@ -4,7 +4,6 @@
 
 use "std/internal/poll"
 use "std/io"
-use "std/jule/integrated"
 use "std/sys"
 
 // Seek whence values.

std/os/proc.jule

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD 3-Clause
 // license that can be found in the LICENSE file.
 
+use integ "std/jule/integrated"
 use "std/os/internal"
 use "std/runtime"
 use "std/sys"

std/os/proc_unix.jule

@@ -0,0 +1,15 @@
+// Copyright 2024 The Jule Programming Language.
+// Use of this source code is governed by a BSD 3-Clause
+// license that can be found in the LICENSE file.
+
+use integ "std/jule/integrated"
+use "std/sys"
+
+// Retrieves the value of the environment variable named by the key.
+// If the variable is present in the environment the value (which may be empty)
+// is returned and the boolean is false. Otherwise the returned value will be
+// empty and the boolean will be true.
+fn LookupEnv(key: str): (val: str, unset: bool) {
+	keyPtr := integ::StrToBytes(key)
+	ret unsafe { sys::Getenv(&keyPtr[0]) }
+}

std/os/proc_windows.jule

@@ -0,0 +1,15 @@
+// Copyright 2024 The Jule Programming Language.
+// Use of this source code is governed by a BSD 3-Clause
+// license that can be found in the LICENSE file.
+
+use integ "std/jule/integrated"
+use "std/sys"
+
+// Retrieves the value of the environment variable named by the key.
+// If the variable is present in the environment the value (which may be empty)
+// is returned and the boolean is false. Otherwise the returned value will be
+// empty and the boolean will be true.
+fn LookupEnv(key: str): (val: str, unset: bool) {
+	keyPtr := integ::UTF16FromStr(key)
+	ret unsafe { sys::Getenv(&keyPtr[0]) }
+}

std/sys/syscall_unix.jule

@@ -34,6 +34,7 @@ cpp unsafe fn remove(path: *integ::Char): int
 cpp unsafe fn mkdir(path: *integ::Char, mode: int): int
 cpp unsafe fn rmdir(path: *integ::Char): int
 cpp unsafe fn unlink(path: *integ::Char): int
+cpp unsafe fn getenv(key: *integ::Char): *integ::Char
 
 // C's DIR.
 type Dir: cpp.DIR
@@ -96,4 +97,16 @@ unsafe fn Mkdir(path: *byte, mode: int): int {
 unsafe fn Rmdir(path: *byte): int { ret cpp.rmdir((*integ::Char)(path)) }
 
 // Wrapper for C's unlink function.
-unsafe fn Unlink(path: *byte): int { ret cpp.unlink((*integ::Char)(path)) }
+unsafe fn Unlink(path: *byte): int { ret cpp.unlink((*integ::Char)(path)) }
+
+// Retrieves the value of the environment variable named by the key.
+// It returns the value, which will be empty if the variable is not present.
+unsafe fn Getenv(key: *byte): (val: str, unset: bool) {
+	valPtr := cpp.getenv((*integ::Char)(key))
+	if valPtr == nil {
+		unset = true
+	} else {
+		val = integ::BytePtrToStr((*byte)(valPtr))
+	}
+	ret
+}

std/sys/syscall_windows.jule

@@ -30,6 +30,7 @@ cpp fn GetStdHandle(stdh: uintptr): *unsafe
 cpp unsafe fn CloseHandle(stdh: *unsafe): bool
 cpp unsafe fn _wstat(path: *integ::Wchar, mut handle: *cpp._stat): int
 cpp unsafe fn _wopen(path: *integ::Wchar, flag: int, mode: int): int
+cpp unsafe fn _wgetenv(key: *integ::Wchar): *integ::Wchar
 cpp fn GetLastError(): u32
 cpp unsafe fn GetCurrentDirectoryW(bufflen: u32, buff: *integ::Wchar): u32
 cpp unsafe fn SetCurrentDirectoryW(path: *integ::Wchar): bool
@@ -154,4 +155,16 @@ unsafe fn FindNextFile(h: Handle, mut data: *Win32FindData): int {
 // Call's Windows FindClose function.
 fn FindClose(h: Handle): int {
 	ret unsafe { cpp.FindClose(cpp.HANDLE(h)) }
+}
+
+// Retrieves the value of the environment variable named by the key.
+// It returns the value, which will be empty if the variable is not present.
+unsafe fn Getenv(key: *u16): (val: str, unset: bool) {
+	valPtr := cpp._wgetenv((*integ::Wchar)(key))
+	if valPtr == nil {
+		unset = true
+	} else {
+		val = integ::U16PtrToStr((*u16)(valPtr))
+	}
+	ret
 }