Implement embedded input function

stdlib/internal/builtin.codon

@@ -34,6 +34,16 @@ def print(*args, sep: str = " ", end: str = "\n", file=_stdout, flush: bool = Fa
     if flush:
         _C.fflush(fp)
 
+def input(prompt: str = '') -> str:
+    if (prompt != ''):
+        print(prompt, end='')
+    buf = Ptr[byte]()
+    sz = 0
+    rd = _C.getline(Ptr[Ptr[byte]](__ptr__(buf)), Ptr[int](__ptr__(sz)), _C.seq_stdin())
+    if rd == -1:
+        return ''
+    return str(buf, rd - 1)
+
 @extend
 class __internal__:
     def print(*args):

test/app/input.codon

@@ -0,0 +1,3 @@
+print(input("input: "), end=',')
+print(input(), end=',')
+print(input())

test/app/input.txt

@@ -0,0 +1,3 @@
+aa bb
+
+cc

test/app/test.sh

@@ -18,3 +18,6 @@ gcc "$testdir/test.c" -L"$arg" -Wl,-rpath,"$arg" -lcodon_export_test -o "$arg/te
 
 # exit code test
 $codon run "$testdir/exit.codon" || if [[ $? -ne 42 ]]; then exit 4; fi
+
+# input test
+[ "$($codon run "$testdir/input.codon" < "$testdir/input.txt")" == "input: aa bb,,cc" ] || exit 5