From 13254d06f01e910e08f3170a815ed3761e021392 Mon Sep 17 00:00:00 2001
From: Justin Ethier <justin.ethier@gmail.com>
Date: Tue, 24 Oct 2017 13:23:48 +0000
Subject: [PATCH] WIP - utf8 / string conversion functions

---
 runtime.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/runtime.c b/runtime.c
index 5387dbf9..da3f255c 100644
--- a/runtime.c
+++ b/runtime.c
@@ -2106,6 +2106,7 @@ object Cyc_string_set(void *data, object str, object k, object chr)
   if (string_num_cp(str) == string_len(str)) {
     raw[idx] = obj_obj2char(chr);
   } else {
+fprintf(stderr, "DEBUG %s, num_cp = %d, len = %d\n", raw, string_num_cp(str), len);
     // TODO: utf8 support
     // find codepoint at k, figure out how many bytes it is,
     // allocate a new string (start) + chr + (end)
@@ -2569,6 +2570,10 @@ object Cyc_utf82string(void *data, object cont, object bv, object start,
     st.str = alloca(sizeof(char) * (len + 1));
     memcpy(st.str, &buf[s], len);
     st.str[len] = '\0';
+    st.num_cp = Cyc_utf8_count_code_points((uint8_t *)(st.str));
+    if (st.num_cp < 0) {
+       Cyc_rt_raise2(data, "utf8->string - error decoding UTF 8", bv);
+    }
     _return_closcall1(data, cont, &st);
   }
 }
@@ -2596,6 +2601,11 @@ object Cyc_string2utf8(void *data, object cont, object str, object start,
     Cyc_rt_raise2(data, "string->utf8 - invalid end", end);
   }
 
+  // TODO: we have code point positions s, e, and length. We need to take those
+  // and walk the string to figure out the starting and ending BYTE positions
+
+  // TODO: fast path, can keep below if string_num_cp(str) == string_len(str)
+
   result.len = len;
   result.data = alloca(sizeof(char) * len);
   memcpy(&result.data[0], &(string_str(str))[s], len);